407-MM-CH18

BHT-407-MM-2

18-00-0023 DEC 2009 Rev. 26 ECCN EAR99

TABLE OF CONTENTS

Paragraph Chapter/Section Page Number Title Number Number

CHAPTER 18 — ROTOR TRACK AND BALANCE AND VIBRATION MONITORING

18-1 RADS-AT Components and Software — Requirements................ 18-00-00 318-2 RADS-AT Components — Requirements................................. 18-00-00 318-3 RADS-AT Software — Requirements....................................... 18-00-00 318-4 Vibration Sources — Definition ...................................................... 18-00-00 318-5 Main Rotor 1/REV — Checks and Control..................................... 18-00-00 318-6 Main Rotor 1/REV Checks and Control — Purpose ................. 18-00-00 318-7 Main Rotor — Preparation for Track and Balance.................... 18-00-00 318-8 RADS-AT — Installation ........................................................... 18-00-00 718-9 Decrease the Main Rotor 1/REV — Description....................... 18-00-00 818-10 Main Rotor — Flight Plans for Smoothing the Main

Rotor ................................................................................. 18-00-00 818-11 The CADU INITIAL Flight Plan — Smoothing the Main

Rotor on the Ground ......................................................... 18-00-00 818-12 The CADU FLIGHT Flight Plan — Smoothing the Main

Rotor In Flight ................................................................... 18-00-00 2218-13 Main Rotor — Adjustments....................................................... 18-00-00 2318-14 Hub Balance Mass — Adjustments .................................. 18-00-00 2318-15 Pitch links — Track Adjustments ...................................... 18-00-00 2518-16 Main Rotor Autorotation RPM — Adjustment ................... 18-00-00 26A18-16A Main Rotor Autorotation RPM — Pitch Link Assembly

Adjustment ........................................................................ 18-00-00 26J18-17 Trim Tabs — Adjustment .......................................................... 18-00-00 2718-18 RADS-AT Troubleshooting ....................................................... 18-00-00 2818-19 Conditions for Rotor Smoothing and Mechanical

Troubleshooting ............................................................................. 18-00-00 2918-20 Tasks to be Done After You Smooth the Main Rotor..................... 18-00-00 2918-21 Tail Rotor — Balancing .................................................................. 18-00-00 3118-22 Tail Rotor Balancing — Purpose .............................................. 18-00-00 3118-23 Tail Rotor Balancing RADS-AT — Installation.......................... 18-00-00 3118-24 Tail Rotor — Balance................................................................ 18-00-00 3418-25 Tail Rotor Balance — Adjustments........................................... 18-00-00 3518-26 Tasks to be Done After You Balance the Tail Rotor ................. 18-00-00 3618-27 General Vibration — Troubleshooting ...................................... 18-00-00 3618-28 General Vibration Troubleshooting — Purpose ........................ 18-00-00 3618-29 General Vibration Troubleshooting RADS-AT — Installation ... 18-00-00 3618-30 Vibration Data — Collecting...................................................... 18-00-00 3918-31 RADS-AT — Technical Support..................................................... 18-00-00 3918-32 RADS-AT — Available Help ..................................................... 18-00-00 3918-33 RADS-AT — Ground Station .................................................... 18-00-00 3918-34 RADS-AT — Bulletin Board ...................................................... 18-00-00 39

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FIGURES

Figure Page Number Title Number

18-1 Accelerometer Installation, Fore, Aft and Vertical, Forward Cabin ..................... 1018-2 Accelerometer Installation, Vertical, Aft Cabin.................................................... 1118-3 Magnetic RPM Sensor and 28 VDC Power Ports, Forward Cabin ..................... 1218-4 RADS-At Installation Schematic ......................................................................... 1318-5 Magnetic RPM Sensor - Removal/Installation .................................................... 1418-6 UTD Bracket - Removal/Installation.................................................................... 1518-7 Main Rotor Blade Paint and Reflective Tape - Removal/Installation .................. 1718-8 CADU Main Menu Display for Initial and Flight Modes ....................................... 1918-9 Main Rotor Track and Balance Adjustment Log ................................................. 2018-10 Main Rotor Hub Balance Weight Location .......................................................... 2418-11 Pitch Link — Track Adjustment........................................................................... 2618-11A Density Altitude (HDmin) Chart ........................................................................... 26C18-11B Autorotation RPM Adjustment Chart................................................................... 26E18-11C Autorotation RPM Adjustment — Example ......................................................... 26F18-11D Main Rotor Pitch Links Adjustment — Autorotative RPM ................................... 26H18-12 RADS-AT Tail Rotor Balance - Removal/Installation .......................................... 3218-13 Schematic of RADS-AT Installation for Tail Rotor Balancing.............................. 3318-14 Balance Location for Tail Rotor........................................................................... 3718-15 Tail Rotor Adjustment Log .................................................................................. 4118-16 CADU Main Menu Display for Tail Flight Plan .................................................... 4218-17 CADU Main Menu Display for VIBCHK and SPECTRUM Flight Plans............... 43

TABLES

Table Page Number Title Number

18-1 Vibration Sources and Related Frequencies for the Model 407 withthe Allison 250-C47B Engine Installed................................................................ 4

18-2 Maintenance Actions to Reduce Vibration .......................................................... 518-3 List of Components Required to Smooth the Main Rotor ................................... 618-4 Description of the Test Conditions that are used to Smooth the Main Rotor

for the Model 407................................................................................................ 918-4A Autorotation RPM — Adjustment Log ................................................................. 26B18-5 RADS-AT Troubleshooting ................................................................................. 2818-6 Vibration Conditions for the Model 407 Series.................................................... 3018-7 Helicopter Vibration Troubleshooting.................................................................. 3018-8 Balance Parts for the Bell Model 407 Tail Rotor ................................................. 38

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ROTOR TRACK AND BALANCE AND VIBRATION MONITORING

18-1. RADS-AT COMPONENTS AND SOFTWARE — REQUIREMENTS

18-2. RADS-AT COMPONENTS — REQUIREMENTS

The Scientific Atlanta (SA) Rotor Analysis Diagnostic System - Advanced Technology (RADS-AT) is the primary vibration analysis and rotor smoothing equipment that is recommended by Bell Helicopter Textron for the Model 407. The RADS-AT equipment that is used on th e Model 407 i s made up of th e components that follow:

The sunshield SA#29722100 is recommended to improve tracker performance in sunny conditions. This sunshield includes special filters and has superior performance compared to si mple tube type sunshields.

18-3. RADS-AT SOFTWARE — REQUIREMENTS

To use the RADS-AT on the Model 407, this software is required: The AIRCRAFT TYPE 407 Version 2.00 (or later version). This software includes all of th e functions that are necessary to control the main rotor 1/rev, the tail rotor 1/rev, and to troubleshoot the vibrations. Future maintenance manual revisions will control the updates to this software.

18-4. VIBRATION SOURCES — DEFINITION

All of the components that rotate can cause vibration because of imbalances in mass and/or aerodynamics. A certain level of vibration from each source is normal and cannot be prevented. Table 18-1 shows the primary sources of vibration and the frequency at which the vibration occurs at 100% RPM. The level of each of the se vibrations is dependent on either the amount of generated force or by the ac tion of th e generated force on the specific individual component. The normal level of vi bration is dependent on the location, the lo ading, and the flight condition. Know these, and know how the vibration sensor is attached, to be consistent when you measure the vibration levels. Table 18-2 shows the maintenance actions that are supported by the RADS-AT.

If there is a sudden change in the main rotor 1/rev levels or in the tail rotor 1/rev levels, do an immediate and thorough inspection of the rotor blades, the hub, and the control system.

18-5. MAIN ROTOR 1/REV — CHECKS AND CONTROL

18-6. MAIN ROTOR 1/REV CHECKS AND CONTROL — PURPOSE

This section describes the t asks that are required to keep the 1/rev vibration to a minimum in the main rotor system. There are two separate flight plans in the RADS-AT to do this task. The first flight plan is a limited flight plan for initial track and balance (INITIAL). This is used to track the main rotor before flight, when one or more major main rotor components have been changed or overhauled. The second flight plan is a complete flight plan (FLIGHT). This is used to reduce the main rotor 1/rev thru the fu ll flight envelope. The components that are required to track and balance the main rotor are shown in Table 18-3.

18-7. MAIN ROTOR — PREPARATION FOR TRACK AND BALANCE

When you use the RADS-AT, the main rotor is built-up and maintained as specified in the applicable maintenance manual and overhaul manual, without change. The procedures that follow are recommended to keep the time required to track and balance the main rotor to a minimum:

TOOLS REQUIRED

NUMBER NOMENCLATURE

SA#29333301 Basic RADS-AT kit (commercial)

SA#29335501 RADS-AT adapter kit (206/407)

SA#29313000 Stiff accelerometer bracket (4) (Optional)

T103317-101 Trim tab bender

T103316-101 Trim tab gage

SA#29722100 Sunshield (Not included in adapter kit)

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FOR PREVIOUSLY WORKED ROTOR BLADE SET, DO NOT SET THE TRIM TAB TO ZERO EVERY T IME THAT YOU SMOOTH A MAIN ROTOR. YOU CAN CAUSE DAMAGE TO THE TAB AND YOU CAN CAUSE FLIGHTS THAT ARE NOT NECESSARY.

1. When a main rotor system is smoothed, make a record of the trim tab settings. Until a main rotor blade

is replaced, use the same trim tab settings as the initial setting for the times that you smooth the main rotor.

2. Do not set the hub balance to zero for routine main rotor trimming. Set the hub balance to zero only if the hub has had maintenance.

3. Unless you must change the length of the pi tch link to set the autorotation RPM, leave the length of the pitch link the same as it was from the last rotor smoothing flight. If you have replaced any components on the pitch links, set the pitch links to the same length as before.

Table 18-1. Vibration Sources and Related Frequencies for the Model 407 with the Allison 250-C47B Engine Installed

VIBRATION EXCITATION SOURCE DESIGNATION REFERENCE RPM (%)

SOURCE FREQUENCY

(RPM)

SOURCE FREQUENCY

(Hz)

Main rotor 1/rev 100% Nr 413 6.88

Main gearbox planetary pinion 1/rev 100% Nr 776 12.93



Main gearbox input gear 1/rev 100% Nr 1936 32.26

Main gearbox sun gear 1/rev 100% Nr 1936 32.26

Tail rotor 1/rev 100% Nr 2500 41.67

Tail gearbox output gear 1/rev 100% Nr 2500 41.67


Engine gearbox idler gear 1/rev (gear #3) 100% N1 4205 70.08

Engine gearbox fuel pump drive 1/rev (gear #5) 100% N1 4205 70.08

Engine gearbox fuel control drive 1/rev (gear #5) 100% N1 4205 70.08

Engine gearbox oil pump drive 1/rev (gear #5) 100% N1 4205 70.08

Engine gearbox N1 tach drive 1/rev (gear #5) 100% N1 4205 70.08

Engine gearbox N2 tach and governor drive 1/rev (gear #12)

100% N2 4410 73.5

Main gearbox accessory drive pinion 1/rev 100% Nr 4445 74.09

Tail rotor 2/rev 100% Nr 5000 83.33


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Main input driveshaft 1/rev 100% Nr 6317 105.28

Main gearbox input pinion 1/rev 100% Nr 6317 105.28

Tail rotor driveshaft 1/rev 100% Nr 6317 105.28

Tail rotor gearbox input pinion 1/rev 100% Nr 6317 105.28

Oil cooler fan 1/rev 100% Nr 6317 105.28

Freewheeling unit 1/rev 100% Nr 6317 105.28

Engine gearbox power output drive 1/rev (gear #10) 100% N2 6317 105.28


Tail rotor 4/rev 100% Nr 10 000 166.67

Engine gearbox torquemeter gear 1/rev (gear #9) 100% N2 10 528 175.47

Engine gearbox starter generator drive 1/rev (gear #7) 100% N1 11 992 199.87

Engine gearbox idler gear 1/rev (gear #4) 100% N2 12 454 207.56

Centrifugal breather idler (gear #2) 100% N1 12 454 207.56

Main rotor driveshaft 2/rev 100% Nr 12 634 210.57

Tail rotor driveshaft 2/rev 100% Nr 12 634 210.57

Oil cooler fan 2/rev 100% Nr 12 634 210.57

Engine gearbox power turbine (N2) input 1/rev (gear #8)

100% N2 32 187 536.44

Engine gearbox gas generator (N1) input 1/rev (gear #1)

100% N1 32 187 850.00

Table 18-1. Vibration Sources and Related Frequencies for the Model 407 with the Allison 250-C47B Engine Installed (Cont.)

VIBRATION EXCITATION SOURCE DESIGNATION REFERENCE RPM (%)

SOURCE FREQUENCY

(RPM)

SOURCE FREQUENCY

(Hz)

Table 18-2. Maintenance Actions to Reduce Vibration

MAINTENANCE TASK WHEN TASK SHOULD BE DONE Paragraph

Track and balance the main rotor / Cabin ride check

After any component is changed in the hub/blade assembly or after any pitch link is changed

18-5 to 18-20

or

At 300 flight hour increments (recommended)

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Track and balance the main rotor / Cabin ride check (Cont’d)

When the flight crew complains of rough ride 18-5 to 18-20

or

Before and after any major overhaul is done on the baseline helicopter

Balance the tail rotor After any change to the tail rotor assembly 18-21 to 18-26

or

At 300 flight hour increments (recommended)

or

When the flight or the ground crew complain of high frequency vibration, or before and after any major overhaul is done on the tailboom.

General vibration troubleshooting When the flight or ground crew detect a change in the normal level of vibration of the helicopter

18-28 to 18-30

Table 18-2. Maintenance Actions to Reduce Vibration (Cont.)

MAINTENANCE TASK WHEN TASK SHOULD BE DONE Paragraph

Table 18-3. List of Components Required to Smooth the Main Rotor

ITEM IDENTIFICATION QUANTITY REQUIRED

Trim tab bender T103317-101 1

Trim tab gage T103316-101 1

Hub balance components BOLT P/N (grams): A/R

• NAS6204-31 (16.0)

• NAS6204-36 (19.0)

• NAS6204-42 (20.9)

• NAS6204-44 (21.5)

• NAS6204-46 (22.4)

• NAS6204-48 (23.1)

• NAS6204-50 (27.4)

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18-8. RADS-AT — INSTALLATION

To track and balance the main rotor, install the RADS-AT as follows:

1. Install the Data Acquisition Unit (DAU) in th e passenger compartment.

2. Attach the accelerometer SA#28110900 to the left hand side of the pedestal, aft of the copilot pedals, with the connector pointed aft (refer to Figure 18-1).

3. Connect the accelerometer end of the accelerometer cable SA#29105600 or SA#29105605 to the accelerometer SA#28110900. Connect the other end of t he cable to ACC1 port on the DAU. This accelerometer measures the fore and aft (F/A) vibrations and is used to determine the main rotor balance (refer to Figure 18-4).

4. Attach the accelerometer SA#28110900 to the left hand side of the pedestal, aft of the copilot pedals, with the connector pointed up (refer to Figure 18-1).

5. Connect the accelerometer end of the accelerometer cable SA#29105600 or SA#29105605 to the accelerometer SA#28110900. Connect the other end of t he cable to ACC2 port on the DAU. This

accelerometer measures the vertical vibrations at the crew station (V_Fwd) (refer to Figure 18-4).

6. Remove the aft right hand passenger seat (refer to Chapter 25).

7. Attach the ac celerometer SA#28110900 to th e screw next to the seat belt with the connector pointed up (refer to Figure 18-2).

8. Connect the accelerometer end of the accelerometer cable SA#29105600 or SA#29105605 to the accelerometer SA#28110900. Connect the other end of t he cable to ACC3 port on the DAU. This accelerometer measures the vertical vibrations at the aft passenger station (V_Aft) (refer to Figure 18-4).

9. Install the ma gnetic RPM sensor through the bottom of the magnetic RPM sensor bracket (refer to Figure 18-5).

10. Disconnect the magnetic RPM sensor cable from the transmission and connect it to the magnetic RPM sensor on the mast.

11. Connect the magnetic pickup cable SA#29105403 to th e magnetic sensor port (receptacle) on the pedestal (or bulkhead) below the

WEIGHT P/N (grams):• 212-010-710-001 (112)

A/R (maximum of six per location)

WASHER P/N (grams):• AN970-4 (7)

A/R (maximum of eight per loca-tion)

NUT P/N (grams):• MS21042L4 (1.4)

A/R

Flat black stencil ink or A-A-208 Type III A/R

Black lacquer paint MIL-C-81352 A/R

Basic RADS-AT kit SA#29333301 1

RADS-AT adapter kit (206/407) SA#29335501 1

Corrosion preventive compound MIL-C-16173 Grade 1 A/R

Table 18-3. List of Components Required to Smooth the Main Rotor (Cont.)

ITEM IDENTIFICATION QUANTITY REQUIRED

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28 VDC power port and to the TACHO 1 port on the DAU (refer to Figures 18-3 and 18-4).

12. When the interrupter is over the ma gnetic RPM sensor, the BLUE blade is over the copilot seat (refer to Figures 18-5 and 18-7). Adjust the sensor in the bracket to ge t a gap of 0.025 inches (0.635 mm) between the magnetic RPM sensor and the interrupter. Attach the magnetic RPM sensor with jamnuts. Safety the jamnuts with lockwire (C-405, BHT-ALL-SPM).

13. Install the tracker bracket SA#29726801 on the landing light cover (refer to Figure 18-6). Install the tracker on the tracker bracket SA#29726801 with the black night lens pointed forward and aligned as shown in Figure 18-6. Tighten the tracker bolts. Make sure that the angle is correct. Connect the tracker cable SA#29325701 to the tracker. Put the tracker cable SA#29325701 through the drain plug of the copilot chin bubble and into the flight compartment. Attach the tracker cable SA#29325701 to the airframe with tape or tie wraps. Make sure that the tracker cable SA#29325701 is below the pi tot tube and the static probes and does not touch them. Connect the tracker cable SA#29325701 to the tracker No. 1 port on the DAU (refer to Figure 18-4).

14. For daylight operations, paint the leading edge of the lower side of the blade with black lacquer paint or flat black stencil ink (refer to Figure 18-7). For night operations, install the r eflective tape SA#10605000 (refer to Figure 18-7). Point the tracker within the area covered by the paint or by the reflective tape for the full range of motion of the main rotor blades. If this condition is not satisfied, the Control And Display Unit (CADU) can report errors (refer to Table 18-4).

NOTE

You must use the tracker when you work in the INITIAL and FLIGHT flight plans.

We recommend that you use the optional sunshield SA#29722100 during periods of high ambient light conditions, for better tracker reliability.

15. Connect the cable SA#29325601 from the CADU to the DAU (refer to Figure 18-4).

16. Connect the 28 VDC power cable SA#29104700 to the 28 VDC outlet on the side of the instrument pedestal near the copilot cyclic control stick and to the 28 VDC port of the DAU (refer to Figures 18-3 and 18-4).

MAKE SURE THAT ALL OF THE EQUIPMENT INSTALLED DOES NOT AFFECT THE SAFE OPERATION OF THE HELICOPTER. SECURE ALL OF THE CABLES TO PREVENT INTERFERENCE WITH THE CONTROLS OR THE CREW.

17. The RADS-AT is now installed and ready to track and balance the main rotor (refer to Figure 18-4).

18. Set the DAU power switch to O N and the DAU comes on when power is supplied to the helicopter.

18-9. DECREASE THE MAIN ROTOR 1/REV — DESCRIPTION

18-10. Main rotor — Flight plans for smoothing the main rotor

Two separate flight plans on the RADS-AT are used to smooth the main rotor. These are the INITIAL flight plan and the FLIGHT flight plan. The test conditions that are used in each flight plan are shown in Table 18-4. The INITIAL flight plan is used when one or more of the major main rotor components are changed and a coarse track and balance of the main rotor system is necessary before forward flight. The FLIGHT flight plan is used to do the final main rotor smoothing in flight, after the INITIAL flight plan is completed, and to trim the main rotor at regular intervals.

18-11. The CADU INITIAL flight plan — Smoothing the main rotor on the ground

The INITIAL flight plan is used when one or more of the major components were changed and a c oarse track and balance procedure is required before flight. The purpose of this flight plan is to track and balance the main rotor on the ground at idle (63% Ng) and at 100% Nr with 35% torque. This is done to c orrectly set the pitch links and the trim tabs, and to balance the main rotor for flight. When you fly after maintenance was done you can prevent too much 1/rev vibration in

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forward flight by using the INITIAL flight plan. When the helicopter has flown, you do not have to do the INITIAL flight plan again until the time for the next major main rotor maintenance procedure occurs. Do the INITIAL flight plan as follows:

1. On the main menu of the CADU, set 407 as the AIRCRAFT TYPE.

2. Set or create the tail number for the helicopter.

3. Use INITIAL as the Flight Plan. When the CADU is correctly set for the INITIAL flight plan, the CADU display is as shown in Figure 18-8.

4. To begin the measure sequence, press the F1 key on the CADU. The list of test conditions at which data will be taken shows on the display (Idle). This test conditions are given in Table 18-4.

Table 18-4. Description of the test conditions that are used to smooth the main rotor for the Model 407

INITIAL FLIGHT

TEST CON-DITIONS

RADS-AT F/A 1/REV

VERTICAL F/A 1/REV

VERTICAL 1/REV

RADS-AT

ID VIBRATION 1/REV VIBRATION

VIBRATION VIBRATION ID

TARGET TARGET TARGET TARGET

(IPS) (IPS) (IPS) (IPS)

Flat pitch at idle (63 % Ng)

IDLE 0.5 - 0.5 - IDLE

100 % Nr at 35 % Torque

35 % Tq 0.25 - 0.25 - 35 % TQ

Hover - - - 0.1 0.15 HOVER

60 knots level flight

- - - - 0.15 60 K


- - - - 0.15 100 K


- - - - 0.15 120 K

60 Kt descent

- - - - 0.15 L/DOWN

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Figure 18-1. Accelerometer Installation, fore, aft and vertical, forward cabin

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Figure 18-2. Accelerometer installation, vertical, aft cabin

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Figure 18-3. Magnetic RPM sensor and 28 VDC power ports, forward cabin

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Figure 18-4. RADS-AT installation schematic

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Figure 18-5. Magetic RPM Sensor — Removal and Installation407MM_18_0006

VIEW LOOKING INBOARD FROM LEFT-HAND SIDE

MAGNETIC RPM SENSOR

NOTE VIEW LOOKING UP

When the magnetic RPM sensor is over the pickup, the blue blade is over the copilot's seat.

INSTALL DIRECTLY UNDERTHE GREEN PITCH HORN

INTERRUPTER

SEE DETAIL A

DETAIL ALOCKWIRE (C-405)

SET GAP TO0.050 IN. (1.270 mm) MIN0.070 IN. (1.778 mm) MAX

Bell Helicopter TEXTRON BHT-407-MM-2

SECURE TRACKERCABLE WITH TAPE

Figure 18-6. UTD bracket - Removal/installation (Sheet 1 of 2)

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Figure 18-6. UTD bracket - Removal/Installation (Sheet 2)

Bell Helicopter B HT-407-M M-2

SPRAY BARE METALLEADING EDGE FOR

(UNDER SIDE)

INSTALL TAPE ATTRAILING EDGE FORNIGHT TRACKING

DAY TRACKING(UNDER SIDE)

MAIN ROTOR BLADE(407-015-001-101)

Figure 18-7. Main rotor blade paint and reflective tape - Removal/Installation

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5. Operate the h elicopter and m ake sure that the main rotor RPM is stable at the idle position (63% Ng). Put the c yclic control stick in the center position and make sure that the collective control stick is all the way down. On the CADU, the IDLE test state is selected (highlighted). Press the DO button to arm the RADS-AT. If all of the internal tests are successful, the title of the test condition appears at the bottom of the display and the system is armed to take data. Press the DO button again to collect the data. When all of the data is collected, the next condition for which data is taken is highlighted and the word DONE shows next to the test condition.

IF THE 1 /REV GROUND BOUNCE BECOMES TOO MUCH WHEN YOU INCREASE THE MAIN ROTOR RPM FROM IDLE TO 100% NR, DO NOT GO TO THE 100% NR TEST CONDITION.SHUT DOWN THE HELICOPTER. TRACK AND BALANCE THE MAIN ROTOR AND USE ONLY THE DATA FROM THE IDLE TEST CONDITION.

NOTE

If any warnings show on the CA DU, try to take the data again at th e same test condition. If the warning shows again, write down the error code. Corrective actions will be shown on the display. You can also find them in the RADS-AT manual. Shut down the helicopter and do the n ecessary corrective action before you continue flight.

6. If you have collected all of the data for the idle test condition, go to the 100% NR wit h 35% T q test condition. When the 100 % NR with 35% Tq testcondition is highlighted on the C ADU, press the DO button to arm the system. When the helicopter is stable, press the DO button again to collect the data.

7. When you have collected all of the data at the twotest conditions, and before you shut down the helicopter, select DIAGNOSTICS from the menu on the CADU. If you have any results that are above the programmed vibration and track targets, they will be shown on the display. To see all of the r esults, press the up arrow key. If you decide to go into flight, go out

of the INITIAL flight plan. Set the RADS-AT to collect data in the FLIGHT flight plan. It is necessary to repeat the ground test conditions to get a correct analysis.

NOTE

The word “limits” shown on the CADU does not refer to an actual limit or to the manufacturer specification. The word limits is a relative word that is used by the RADS-AT to guide the tracking and balance of the main rotor. For the gu idelines to th e vibration levels which require corrective maintenance, refer to Table 18-6.

8. The CORRECTIVE ACTIONS display shows. Use the right arrow key and read the recommended adjustments. Make a record of these adjustments on a 'Main Rotor Adjustment Form' (refer to Figure 18-9).

9. On the CADU, press the DO button to see the predicted results. Press the DO button again to see the DIAGNOSTICS menu. If you have made a record of all of the adjustments, select MAIN MENU and press the DO button to return to the main display.

10. To make the adjustments that show on the RADS-AT, follow the procedures in Paragraph 18-14. The initial flight plan is complete when you meet the conditions that follow:

a. At Idle, the main rotor is in track (±2 mm).

b. At 100% NR with 35% Tq, the main rotor is in track (± 2 mm) and is in balance per Table 18-4.

11. If you must change the main rotor track, do as follows:

a. At Idle, adjust the pitch links.

b. At 100% NR with 35% Tq, set the tab adjustment on the RADS-AT to the ‘ on’ position and use tab adjustment to track the rotor.

12. Do the previous steps 4. thru 10. until you reach all of the vibration and track targets. On the CADU, go to the FLIGHT flight plan to do the fi nal main rotor smoothing in flight.

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Figure 18-8. CADU main menu display for initial and flight modes

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Figure 18-9. Main rotor track and balance adjustment log (Sheet 1 of 2)

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Figure 18-9. Main rotor track and balance adjustment log (Sheet 2)

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18-12. THE CADU FLIGHT FLIGHT PLAN —SMOOTHING THE MAIN ROTOR INFLIGHT

The FLIGHT flight plan is used when periodic orroutine smoothing of the main rotor with respect to themain rotor 1/rev is necessary. It is also used after mainrotor maintenance, and after the INITIAL flight plan issatisfactorily completed. Do the FLIGHT flight plan asfollows:

1. On the main menu of the CADU, set 407 as theAIRCRAFT TYPE.


3. Use FLIGHT as the flight plan. When the CADUis correctly set for the FLIGHT flight plan, the CADUdisplay is as shown in Figure 18-8.

4. To begin the measuring sequence, press the F1key on the CADU. The list of test conditions at whichdata will be taken will be shown on the display. Thesetest conditions are given in Table 18-4.

5. Operate the h elicopter and collect the data foreach test condition that is shown on the display.Follow the procedures in paragraph 18-11. Observethe general rules that follow:

NOTE

If any warnings show on the CADU, try totake the data again at t he same testcondition. If the warning shows again, writedown the error code. Corrective actions willshow on the display. You can also find themin the RADS-AT manual. Shut down thehelicopter and do the necessary correctiveaction before you continue flight.

6. When you collect data in flight, it is not necessaryfor you to collect data at the high speed test conditionsif the 1/rev becomes more than is comfortable.

7. If you do not collect data for some test conditions,or if you collect data out of sequence, use the arrowkeys to select the applicable test condition.

8. Do not keep data from one test condition underthe label for another test condition, or the RADS-ATdiagnostics will not function correctly.

9. Only one forward flight condition is necessary forthe RADS-AT to beg in to mak e an an alysis of the

adjustments that are necessary to smooth the mainrotor. As the 1/rev levels are reduced, however, it isimportant to c ollect data at al l of th e test conditionsthat show on the display, to make sure that the bestmain rotor 1/rev levels will be reached for the full flightenvelope of the helicopter.

10. After a test condition is measured, you may pressthe F1 key under DISPLAY to see the measurementsfor that test condition.

11. After you have collected all of the data, land thehelicopter and shut it down. The CADU willautomatically show the menu options on the display. Ifdata for some of the test conditions was not collected,press QUIT to go ou t of the MEASUREMENT mode.Use the arrow keys to select SAVE AND EXIT. Pressthe DO button to keep the data.

12. On the CADU, use the arrow keys to selectDIAGNOSTICS and press the DO button. If the mainmenu is displayed, press F3 to access theDIAGNOSTICS. The CA DU will display both thecollected flight data and the p rogrammed vibrationtarget values on the screen. If all the collected data arewithin the targets, press quit to exit the program andremove RADS per paragraph 18-20. If any of th emeasured vibrations exceed the targets, it is theresponsibility of the owner/operator to determine if therotor vibrations need to be lowered. If the decision ismade to improve the rotor vibrations, proceed with thefollowing steps.

NOTE

The word 'limits' shown on the CADU doesnot refer to an actual limit or to themanufacturer specification. The word 'limits'is a relative word that is used by theRADS-AT to guide the tracking and balanceof the main rotor. For the guidelines to thevibration levels which require correctivemaintenance, refer to Table 18-6.

13. To find the adjustments that are necessary tosmooth the main rotor, do the steps that follow:

a. Press the DO button to calculate and show therecommended adjustments. Make a not e of th eseadjustments.

b. Press the DO button again to see thepredicted results (if you have a 6.01 system, selectVIEW PREDICTIONS from the DIAGNOSTICSmenu).

BHT-407-MM-2

18-00-0016 FEB 2012 Rev. 34 ECCN EAR99

c. Make a note of the measured 1/rev levels andof the predictions.

d. Press the DO button again to return to theDIAGNOSTICS menu.

e. If three or more adjustments arerecommended, or if the recommended adjustmentsinclude bending the outboard tab in the directionopposite to the indicated pitch link adjustment, you canget an acceptable ride with fewer adjustments. Tomake an analysis, do the steps that follow:

(1) Use the arrow keys and select EDITDEFAULTS. Press the DO button.

(2) If the field MAXIMUM NUMBER OFADJUSTMENTS is not selected (the number zero (0)is shown), use the arrow keys and select it.

(3) Type the number 1 and press the DObutton to calculate the one best adjustment. Make anote of the recommended adjustment and look at thepredicted results. If the predicted results aresatisfactory, make a record of the adjustment on aMain Rotor Adjustment Log (Figure 18-9). Follow thesteps in paragraph 18-14 and make the adjustment. Ifthe predicted results are not satisfactory, do the EDITDEFAULTS procedure again and select 2. If thosepredicted results are again not satisfactory, do theEDIT DEFAULTS procedure again and select 3. Ifthose predicted results are again not satisfactory, dothe EDIT DEFAULTS procedure again and select 4.Do this until the predicted results are satisfactory oruntil there is a large improvement. When you find theminimum number of adjustments, make a record of theadjustments on a Main Rotor Adjustment Log(Figure 18-9). Do the adjustments (paragraph 18-14).

NOTE

For the diagnostics to work correctly, youmust get at least one forward speed.

NOTE

When you are in the EDIT ADJUSTABLESoption, one and only one hub balanceadjustment in each blade pair must beturned on at all times.

14. When you have made all of the adjustments, dothe previous step 4 through step 12 again until youhave the best ride. The best ride is:

• One where all of the in flight vibration levelsare below the target

• The ride is acceptable to the flight crew

• More adjustments are not predicted to changethe predicted 1/rev levels

15. If the ride is satisfactory, go to paragraph 18-20. Ifthe vibration levels are not satisfactory, refer toparagraph 18-18 and paragraph 18-19 for thetroubleshooting procedures.

18-13. MAIN ROTOR ADJUSTMENTS

18-14. Hub Balance Mass — Adjustments

The RADS-AT gives the amount of hub balance mass(weights, washers, bolts) in grams. The mass of eachof these components is shown in Table 18-3. Thebalance masses are added or removed from the armsat the location shown in Figure 18-10. A positiveadjustment tells you to either add mass to theindicated yoke or to remove mass from the oppositeyoke. A negative adjustment tells you to either removemass from the indicated yoke or to add mass to theopposite yoke.

To make the adjustments, do the steps that follow:

NOTE

To do the adjustment, it is better to removethe weights than to add the weights.Remove the weights whenever possible.

1. Find the hub balance mass combination to getthe RADS-AT recommended adjustment.

2. At the adjustment location, remove the nut (5,Figure 18-10, washers (2), weights (3), and bolt (1)from the yoke arm (4). Add or remove the applicablehub balance mass.

NOTE

At least one full thread of each bolt (1) mustshow beyond the nut (5).

BHT-407-MM-2

18-00-00 Rev. 2

Figure 18-10. Main Rotor Hub Balance Weight Location

BHT-407-MM-2

18-00-0016 FEB 2012 Rev. 34 ECCN EAR99

3. Equally divide the washers (2) and the weights(3) between the top and bottom of the yoke arm. Installthe bolt (1) and the nut (5). Torque the nut 50 to70 inch-pounds (5.65 to 7.91 Nm).

4. After you complete the main rotor smoothingprocedure, replace all of the nuts that were removed.Install new nuts (5) and torque them.

18-15. Pitch links — Track Adjustments

The RADS-AT gives the pitch link adjustments in flats.A positive adjustment tells you to increase the pitch onthe specified blade. A negative adjustment tells you todecrease the pitch on the specified blade. To make thepitch link adjustments, refer to Figure 18-11.

NOTE

On main rotors that have a significantout-of-track for which the RADS-AT givesmore than 12 flats of adjustment, you cando the coarse adjustment with the lower rodend or the upper clevis as follows:

• 1 turn of the pitch link barrel = 6 flats

• 1/2 turn of the lower rod end = 10 flats

• 1/2 turn of the upper clevis = 7 flats

1. When you use the pitch link barrel to make theadjustment, do the steps that follow (Figure 18-11):

a. Find the pitch link adjustment on theRADS-AT.

b. Remove the lockwire (2) from the nut (1).

c. Loosen the nuts (1 and 4).

d. Turn the barrel of the pitch link (3) to get theadjustment that is indicated on the RADS-AT.

NOTE

After you tighten the nut (1), the maximumnumber of threads that are permitted toshow on the upper clevis is 14. After youtighten the nut (4), the maximum number ofthreads that are permitted to show on thelower rod end is 9.

e. Torque the nut (1) . Safety the nut withlockwire (C-405).

f. Put the collective control stick at themid-collective position and put the cyclic control stickin the center position. Adjust the position of the rodend bearing (8) in the swashplate horn (7) untilDimension A and Dimension B are equal to within0.04 inch (1.02 mm). Hold the rod end in this position.

g. Torque the nut (4) .

h. Do the previous step b through step g againfor the remaining pitch links (3) that must be adjusted.

2. When you use the pitch link lower rod end tomake the adjustment, do the steps that follow:

a. Identify the pitch link that you will adjust.

b. Loosen the nut (4). Remove the cotter pin(10), nut (9), washer (11), bolt (5), and washer (6).

c. Adjust the rod end bearing (8) as necessary toadjust the blade track.

d. Put a coating of corrosion preventivecompound (C-104) on the shank of the bolt (5),washers (6 and 11), and mating surfaces of the rodend bearing (8) and the swashplate horn (7).

e. Install the pitch link (3) in the swashplate horn(7). Install the bolt (5), washers (6 and 11), and nut (9).

f. Torque the nut (9) . Safety the nut with thecotter pin (10).

Refer to BHT-ALL-SPM for specifications.

MATERIALS REQUIRED

NUMBER NOMENCLATURE

C-104 Corrosion Preventive Compound

C-405 Lockwire

T

T

T

BHT-407-MM-2

18-00-00 Rev. 26 23 DEC 2009 ECCN EAR99

Figure 18-11. Pitch Link — Track Adjustment407_MM_18_0012

TURN THIS WAY TO

INCREASE PITCH

DECREASE PITCH

TURN THIS WAY TO

12. Cotter pin

15. Clevis

14. Bolt

13. Nut

11. Washer

10. Cotter pin

9. Nut

8. Rod end bearing

7. Swashplate horn

6. Washer

5. Bolt

4. Nut

3. Pitch link

2. Lockwire

1. Nut

2

50 TO 70 IN-LBS(5.6 TO 7.9 Nm)

120 TO 160 IN-LBS(14 TO 18 Nm)

1

NOTE

Dimensions A and B are to be equal within 0.04 inch (1.0 mm).

3

14

1

12

13

152

1

4

11

10

9

87

6

5

3

2

B

A

3

3

150 TO 200 IN-LBS(17 TO 22 Nm)

1616

16. Washer

BHT-407-MM-2

18-00-00

ECCN EAR99

g. Put the collective control stick at the midcollective position and put the cyclic control stick in thecenter position. Adjust the position of the lower rodend bearing (8) in the swashplate horn (7) untilDimension A and Dimension B are equal to within0.04 inch (1.02 mm). Hold the rod end in this position.

h. Torque the nut (4) .

i. Do the previous step b through step h againfor the remaining pitch links (3) that must be adjusted.

3. When you use the upper clevis to make theadjustment, do the steps that follow (Figure 18-11):

a. Remove the lockwire (2) from the nut (1).Loosen the nut.

b. Remove the cotter pin (12), nut (13), washers(16), and bolt (14).

c. Adjust the clevis (15) as necessary to adjustthe blade track.

d. Put a coating of corrosion preventivecompound (C-104) on the shank of the bolt (14), thewashers, and the mating surfaces.

e. Put the collective control stick at the midcollective position and put the cyclic control stick in thecenter position. Adjust the position of the rod endbearing (8) in the swashplate horn (7) until theDimension A and Dimension B are equal to within0.04 inch (1.0 mm). Hold the rod end in this position.

f. Install the upper clevis with the bolt (14),washers (16), and nut (13). Torque the nut andinstall cotter pin (12).

g. Torque the nut (1) . Safety the nut withlockwire (C-405).

h. Do the previous step a through step g againfor the remaining pitch links that must be adjusted.

18-16. Main Rotor Autorotation RPM —Adjustment

Autorotation RPM should be adjusted withconsideration given to seasonal OAT and altitudes in

the operating environment. Low gross weight, low

temperature/low density altitude result in lowerautorotation RPM when compared to high gross

weight, high temperature/high density altitude.

This procedure uses a seasonally adjusted densityaltitude (HDmin), as a baseline to optimize autorotation

RPM throughout the gross weight range. It isrecommended that a check/adjustment of autorotation

RPM be carried out, at a minimum, when seasonalchanges result in a change in average minimum OATor when the helicopter geographical location changes.

An autorotation RPM adjustment log (Table 18-4A) isprovided to assist in completing the procedure.

Density altitude is the result of pressure altitude

corrected for temperature. To define HDmin, thefollowing two factors must be considered:

• Determine the lowest pressure altitude

(HPmin) over which operations are likely to becarried out. The lowest geographic altitudemay be used for the purpose of these

calculations.

• Determine the seasonal average minimumtemperature (OATmin) in the operating region.

(Use average temperature anticipated untilnext autorotation check/adjustment is

anticipated.)

Initiate calculations to determine the correct main rotorautorotation RPM as follows:

NOTE

Record information in the Autorotation RPM

Adjustment Log (Table 18-4A).

1. Using HPmin and OATmin, calculate HDmin usingthe density altitude conversion chart (Figure 18-11A).

The value (HDmin) is the minimum density altitudeover which operations are likely to be carried out.

The following provides two examples of determiningHDmin.

T

T

T

16 FEB 2012 Rev. 34 Page 26A

BHT-407-MM-2

ECCN EAR9918-00-00

Table 18-4A. Autorotation RPM — Adjustment Log

AUTOROTATION RPM ADJUSTMENT LOG

Date: ___________________

Helicopter S/N: ______________________

Total Flight Time: __________________

1. Determine HDmin (minimum density altitude):

HPmin (use lowest operational geographic altitude) ___________

OATmin (use average seasonal minimum temperature) ___________

HDmin (calculate from Figure 18-11A) ___________

2. Conduct autorotation RPM check (collective full down, throttle at idle, stabilize at 55KTS):

HPcheck (set 29.92 (1013 mb) on altimeter) ___________

OATcheck ___________

Main Rotor RPM ___________

Fuel Quantity ___________

3. Calculate HDcheck:

Apply HPcheck _________ and OATcheck __________ against Figure 18-11A to obtain HDcheck ___________

4. Calculate delta density altitude (ΔHD):

HDcheck _________ – HDmin __________ = ΔHD ___________

5. Determine test gross weight of helicopter at time of RPM check (use recorded fuel quantity and loading configuration):

Gross Weight ___________

6. Apply ΔHD and helicopter test gross weight to Autorotational Adjustment RPM Chart (Figure 18-11B):

ΔHD ___________

Helicopter Test Gross Weight ___________

Target Main Rotor RPM ___________

7. Adjust main rotor RPM if not within ±2% of target. Refer to paragraph 18-16A.

8. Final adjusted main rotor autorotational RPM ______________

Page 26B Rev. 26 23 DEC 2009

BHT-407-MM-2

18-00-00ECCN EAR99

Figure 18-11A. Density Altitude (HDmin) Chart

-50 -40 -30 -20 -10 0 10 20 30 40 50 60OUTSIDE AIR TEMPERATURE - °C

-8

-6

-4

-2

0

2

4

6

8

10

12

14

16

18

20

22

24DE

NSIT

YAL

TITU

DE-F

Tx

1000

25,000

SEA LEVEL

STANDARDDAY

5,000

-5,000

10,000

15,000

20,000

PRESSURE ALTITUDE - FT

-10,000

23 DEC 2009 Rev. 26 Page 26C

BHT-407-MM-2

ECCN EAR99

18-00-00

NOTE

Refer to Figure 18-11C, Sheet 1 of 2 for thefirst example.

• The helicopter is based at 2000 feet (609.6 m)and the minimum average seasonaltemperature (OATmin) is 62.6°F (17°C). Thehelicopter is normally operated at or abovethese conditions, so HDmin will be theresultant density altitude at 2000 feet(609.6 m) (HPmin) and 62.6°F (17°C)(OATmin), or 2700 feet (822.9 m) (HDmin).This becomes the baseline for the autorotationadjustment chart.

NOTE

Refer to Figure 18-11C, Sheet 2 of 2 for thesecond example.

• The helicopter is based at an airport at700 feet (213.4 m) ASL, but is frequentlyoperated offshore (sea level). The averageseasonal minimum temperature is 17.5°F(-8°C). Therefore, the seasonal minimumdensity altitude over which operations arelikely to be carried out is sea level (HPmin) at17.5°F (-8°C) (OATmin), or -2900 feet(-883.9 m) (HDmin).

CAUTION

A QUALIFIED PERSON MUST BE AT THEHELICOPTER CONTROLS DURING THEFOLLOWING PROCEDURE.

2. Start and operate helicopter (BHT-407-FM-1,Section 2).

CAUTION

BE PREPARED TO APPLY THROTTLE IFNR DROPS BELOW 85%. BE PREPAREDTO APPLY COLLECTIVE TO PREVENTNR OVERSPEED ABOVE 107%.

3. Fly the helicopter and establish the existingautorotation RPM (NR) by initiating an autorotative

descent (collective full down, throttle at IDLE position)at 55 KIAS. Once stabilized, record pressure altitude(HPcheck), outside air temperature (OATcheck), mainrotor RPM, and fuel quantity on the autorotation RPMAdjustment Log (Table 18-4A).

4. Using HPcheck and OATcheck, establish thedensity altitude (HDcheck) at which the autorotativeRPM check was conducted from the density altitudechart (Figure 18-11A).

5. Compute the delta density altitude (ΔHD) betweenHDmin and HDcheck. This is done by subtractingHDmin from HDcheck:

HDcheck – HDmin = ΔHD

NOTE

Subtracting a minus (negative) value fromanother value results in the two valuesbeing added.

For example:

+2000 – (-1000) = +3000

6. Determine the test gross weight of the helicopterusing the recorded fuel quantity and loadingconfiguration at the time of the RPM check.

7. Using the autorotation RPM adjustment chart(Figure 18-11B), plot the ΔHD value computed instep 5. Move over to the appropriate gross weight lineand down to the target main rotor RPM (NR).

NOTE

If the chart target NR value is above 107%,adjust gross weight or modify check altitudeas necessary to achieve a target NR valuewithin chart limits.

8. Adjust the main rotor pitch links (paragraph18-16A) if the autorotation RPM is not within ±2% ofthe required RPM.

9. If necessary, repeat step 1 through step 8 andadjust the main rotor pitch links until the correctautorotation RPM has been established.

10. Some examples of autorotation RPM calculationsare provided in Figure 18-11C.

Page 26D Rev. 34 16 FEB 2012

BHT-407-MM-2

18-00-00ECCN EAR99

Figure 18-11B. Autorotation RPM Adjustment Chart

407 AUTOROTATION NR

NOTE: Min Operational Density Altitude refers tothe absolute minimum density altitude atwhich operations are to be carried out.

85 90 95 100 105 110 115

MAIN ROTOR RPM (%)

- 2000

- 1000

+ 1000

+ 2000

+ 3000

+ 4000

+ 5000

+ 6000

+ 7000

+ 8000

+ 9000

+ 10000

DE

LT

AD

EN

SIT

YA

LT

ITU

DE

AB

OV

E(F

EE

T)

MIN

OP

ER

AT

ION

AL

HD

NR (MAX)

107N

R (MIN)

GROSS WEIGHT (LBS) = 4000 4500

5000

3000 3500

Min OperationalDensity Altitude

23 DEC 2009 Rev. 26 Page 26E

BHT-407-MM-2

ECCN EAR9918-00-00

Figure 18-11C. Autorotation RPM Adjustment — Example (Sheet 1 of 2)

407_MM_18_0036a

Determining HDmin:

HPmin = 2000 feet

OATmin = 17°CH

Dmin = 2700 feet (Calculated from Density Altitude chart, Figure 18-11A)

Auto NR

check:

HPcheck = 3000 feet

OATcheck = 24°CH

Dcheck = 4700 feet (Calculated from Density Altitude chart, Figure 18-11A)

HD = (H

Dcheck - H

Dmin) = 4700 - 2700 = 2000 feet H

D

Test Gross weight = 3500 pounds

Target NR = 94.5%

94.5%

(TARGET)

HD

407 AUTOROTATION NR

NOTE: Min Operational Density Altitude refers to the absolute minimum

density altitude at which operations are to be carried out.

85 90 95 100 105 110 115

MAIN ROTOR RPM (%)

- 2000

- 1000

+ 1000

+ 2000

+ 3000

+ 4000

+ 5000

+ 6000

+ 7000

+ 8000

+ 9000

+ 10000

DE

LT

AD

EN

SIT

YA

LT

ITU

DE

AB

OV

E(F

EE

T)

MIN

OP

ER

AT

ION

AL

HD

N

107N

R (MIN)


5000

3000 3500


D

D

R(MAX)

Page 26F Rev. 26 23 DEC 2009

BHT-407-MM-2

18-00-00ECCN EAR99

Figure 18-11C. Autorotation RPM Adjustment — Example (Sheet 2 of 2)407_MM_18_0036b

Determining HDmin:

HPmin = Sea level

OATmin = -8°CH

Dmin = -2900 feet (Calculated from Density Altitude chart, Figure 18-11A)

Auto NR check:

HPcheck = 2000 feet

OATcheck = 0°CH

Dcheck = 650 feet (Calculated from Density Altitude chart, Figure 18-11A)

HD = (H

Dcheck - H

Dmin) = 650 minus -2900 = 3550 feet H

D

Test Gross weight = 4500 pounds

Target NR = 104%

104%

(TARGET)

HD

407 AUTOROTATION NR

NOTE: Min Operational Density Altitude refers to the absolute minimum

density altitude at which operations are to be carried out.

85 90 95 100 105 110 115

MAIN ROTOR RPM (%)

- 2000

- 1000

+ 1000

+ 2000

+ 3000

+ 4000

+ 5000

+ 6000

+ 7000

+ 8000

+ 9000

+ 10000

DE

LT

AD

EN

SIT

YA

LT

ITU

DE

AB

OV

E(F

EE

T)

MIN

OP

ER

AT

ION

AL

HD

107


5000

3000 3500


D

DN

NR (MIN)

R(MAX)

23 DEC 2009 Rev. 26 Page 26G

BHT-407-MM-2

ECCN EAR9918-00-00

Figure 18-11D. Main Rotor Pitch Links Adjustment — Autorotative RPM (Sheet 1 of 2)407_MM_18_0037a

1

17

16

16

15

14

18

2

11

SEE DETAIL A

12

13

3

10

9

8

7

3

4

5

4

6

193

1

2

Page 26H Rev. 26 23 DEC 2009

BHT-407-MM-2

18-00-00ECCN EAR99

Figure 18-11D. Main Rotor Pitch Links Adjustment — Autorotative RPM (Sheet 2 of 2)NO OBJECT BEYOND THIS POINT 407_MM_18_0037b

Lower rod end bearing

NutWasherBoltOuter ring assemblyJam nut

12.13.14.15.16.17.18.19.

Apply corrosion preventive compound (C-104) to bolt shanks prior to installation. Do not apply corrosionpreventive compound to the bolt threads.

Dimensions A and B are to be equal within 0.04 inch (1.0 mm).

1

2

NOTES

Pitch hornBearing assemblyBoltWasherNutCotter pin

1.2.3.4.5.6.7.8.9.

10.11.

3

4

CORROSION PREVENTIVECOMPOUND (C-104)

CORROSION PREVENTIVECOMPOUND (C-101)

1

3

Apply a coating of corrosion preventive compound (C-101) to the jam nuts (12 and 19) and exposed threadsof lower rod end bearing (13) and upper clevis (7) after final adjustment.

Apply corrosion preventive compound (C-101) to all bolt heads, washers, nuts and exposed threads after installation.

Upper clevisPitch link assemblyPitch link tubeUP (decal)DOWN (decal)

Jam nut

Cotter pin

150 TO 70 IN-LBS

(5.6 TO 7.9 Nm)

2

3

120 TO 160 IN-LBS

(14 TO 18 Nm)

150 TO 200 IN-LBS

(17 TO 22 Nm)

2

1

4

LOCKWIRE (C-405)

A

B

1318

2

2

DETAIL A

23 DEC 2009 Rev. 26 Page 26I

BHT-407-MM-2

ECCN EAR9918-00-00

18-16A. Main Rotor Autorotation RPM — PitchLink Assembly Adjustment

NOTE

As applicable, refer to Chapter 67 forcomplete information on pitch link assemblyremoval, cleaning, inspection, repair,adjustment limits, and installation.

NOTE

The following procedure is identical for allfour pitch link assemblies (8,Figure 18-11D). Adjust all four pitch linkassemblies to an equal amount.Information is provided to adjust the upperclevis (7), lower rod end bearing (13), or toroll the pitch link tube (9), as required.

1. Determine the autorotation RPM adjustment thatis required (paragraph 18-16).

2. When using the pitch link assembly lower rod endbearing (13) for RPM adjustments, proceed as follows:

a. Loosen the jam nut (12).

b. Remove the cotter pin (14), nut (15), washers(16), and bolt (17). Discard the cotter pin.

c. Move the lower rod end bearing (13) of thepitch link assembly (8) away from the lug of the outerring assembly (18).

NOTE

Prior to making any adjustment, note thecurrent position of the lower rod endbearing (13) and pre-identify the directionand amount of rod end rotation that will berequired. Only full turns (3% RPM) or1/2 turns (1.5% RPM) are achievable usingthe lower rod end bearing.

d. If the autorotation RPM is high, turn the lowerrod end bearing (13) out of the pitch link assembly (8)to reduce the RPM.

e. If the autorotation RPM is low, turn the lowerrod end bearing (13) into the pitch link assembly (8) toincrease the RPM.

f. Position the lower rod end bearing (13) of thepitch link assembly (8) into the lug of the outer ringassembly (18).

g. Apply corrosion preventive compound (C-104)to the shank of the bolt (17). Do not apply corrosionpreventive compound to the bolt threads.

h. With the head of the bolt (17) facing in thedirection of main rotor rotation, install the bolt, washers(16), and nut (15). Torque the nut and safety withnew cotter pin (14).

i. Make sure the lower rod end bearing (13) iscentered in the lug of the outer ring assembly (18)(Figure 18-11D, Detail A).

j. Hold the lower rod end bearing (13) in thecorrect position and torque the lower jam nut (12) .Confirm position per Detail A.

k. After final adjustment, apply a coating ofcorrosion preventive compound (C-101) to the jam nut(12), the exposed threads of the lower rod end bearing(13), the bolt head (17), washers (16), nut (15), andexposed threads of the bolt.

3. When using the pitch link assembly upper clevis(7) for RPM adjustments, proceed as follows:

a. Remove the lockwire and loosen the jamnut (19).

b. Remove the cotter pin (6), nut (5), washers(4), and bolt (3). Discard the cotter pin.

Refer to BHT-ALL-SPM for specifications.

MATERIALS REQUIRED

NUMBER NOMENCLATURE



C-405 Lockwire

T

T

Page 26J Rev. 26 23 DEC 2009

BHT-407-MM-2

18-00-0023 DEC 2009 Rev. 26 Page 27ECCN EAR99

c. Move the upper clevis (7) of the pitch linkassembly (8) out of the bearing assembly (2).

NOTE

Prior to making any adjustment, note thecurrent position of the upper clevis (7) andpre-identify the direction and amount ofrotation that will be required. Only full turns(1.5% RPM) or 1/2 turns (0.75% RPM) areachievable.

d. If the autorotation RPM is high, turn the upperclevis (7) out of the pitch link assembly (8) to reducethe RPM.

e. If the autorotation RPM is low, turn the upperclevis (7) into the pitch link assembly (8) to increasethe RPM.

f. Position the upper clevis (7) of the pitch linkassembly (8) into the bearing assembly (2).

g. Apply corrosion preventive compound (C-104)to the shank of the bolt (3). Do not apply corrosionpreventive compound to the bolt threads.

h. With the head of the bolt (3) facing in thedirection of main rotor rotation, install the bolt, washers(4), and nut (5). Torque the nut and safety with newcotter pin (6).

i. Make sure the lower rod end bearing (13) iscentered in the lug of the outer ring assembly (18)(Figure 18-11D, Detail A).

j. Hold the lower rod end bearing (13) in thecorrect position and torque the upper jam nut (19) .Confirm position per Detail A. Safety the jam nut withlockwire (C-405).

k. After final adjustment, apply a coating ofcorrosion preventive compound (C-101) to the jam nut(19), the exposed threads of the upper clevis (7), thebolt head (3), washers (4), nut (5), and exposedthreads of the bolt.

4. When using the pitch link tube (9) foradjustments, proceed as follows:

a. Remove the lockwire from the upper jam nut(19). Loosen the jam nuts (19 and 12).

NOTE

Prior to making any adjustment, note thecurrent position of the pitch link tube (9)and pre-identify the direction and amount ofrotation that will be required. Each fullrotation of the pitch link tube will provide achange of approximately 0.5% RPM.

b. If the autorotation RPM is high, refer to the UPdecal (10) and rotate the tube (9) in the direction of thearrow to increase its length and reduce the RPM.

c. If the autorotation RPM is low, refer to theDOWN decal (11) and rotate the tube (9) in thedirection of the arrow to decrease its length andincrease the RPM.

d. Make sure the lower rod end bearing (13) iscentered in the lug of the outer ring assembly (18)(Figure 18-11D, Detail A).

e. Hold the upper clevis (7) and lower rod endbearing (13) in the correct position and torque theupper and lower jam nuts (19 and 12) . Confirmposition of lower rod end bearing per Detail A. Safetythe jam nut (19) with lockwire (C-405).

f. After final adjustment, apply a coating ofcorrosion preventive compound (C-101) to the jamnuts (19 and 12) and the exposed threads of upperclevis (7) and lower rod end bearing (13).

18-17. TRIM TABS — ADJUSTMENT

The RADS-AT gives the tab adjustments in 0.1°increments. A positive adjustment tells you to bend thetab of the specified blade up, or to bend the tab on theopposite blade down. A negative adjustment tells youto bend the tab of the specified blade down, or to bendthe tab on the opposite blade up. To adjust the trimtabs, do the steps that follow:

1. On the RADS-AT, find the trim tab adjustment.Make the recommended adjustment to the nearest0.5°.

2. Put the trim tab gauge (T103316-101) on themain rotor blade just inboard of the tab. Make sure thatthe arrow on the gauge points up.

T

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3. Loosen the wing nuts on the trim tab benderT103317-101. Put the trim tab bender T103317-101 inposition over the trim tab. Make sure that the trim tabbender T103317-101 is in the center and that there isapproximately a 0.125 inch (3.17 mm) gap betweenthe leading edge of the trim tab bender T1033-101 andthe trailing edge of the blade. Tighten the wing nutsuntil the trim tab bender T103317-101 is attachedcorrectly to the trim tab.

4. Adjust the position of the trim tab gaugeT103316-101 so that it is square with the trim tabbender TT103317-101. Make sure that the trim tabgauge TT103316-101 touches the indicator on the trimtab bender TT103317-101 and that it also touches thetrailing edge of the main rotor blade.

5. Make a note of the current angle of the trim tabon the trim tab gauge TT103316-101. Calculate whatthe final reading should be to get the necessaryadjustment.

NOTE

Final top settings of more than ±15° mayhave a tendency to move back very slowlyto the lower settings. If possible, do not dolarge settings.

6. Bend the trim tab in the necessary direction untilthe trim tab is at rest (with no load on the trim tabbender T103317-101). Make sure that the actual trimtab angle is approximately 2° more than the calculatedfinal trim tab angle. Bend the trim tab back until thefinal ‘at rest’ position of the trim tab is at the necessarytrim tab angle. This minimizes trim tab creep.

7. Remove the trim tab bender T103317-101 andthe trim tab gauge T103316-101 from the main rotorblade.

8. Do step 1 through step 7 again until you make allof the adjustments.

18-18. RADS-AT TROUBLESHOOTING

Table 18-5. RADS-AT Troubleshooting Chart

PROBLEM CAUSE SOLUTION

Adjustments do not reduce 1/rev Improper accelerometer installation Refer to applicable section in this manual for the correct installation.

Data is not stored when the flight condition is completed

Operator presses the QUIT button before the data is stored

Do not press the QUIT button unless you want to clear a warning or go out of the list of test conditions.

Accelerometer saturation Soft accelerometer bracket Install thicker bracket.

Damaged accelerometer cable Replace the accelerometer cable.

Failed accelerometer Replace accelerometer.

TACHO failure Magnetic sensor gap is too wide Adjust the gap: the minimum is 0.025 inch (0.635 mm), the maximum is 0.07 inch (1.78 mm).

Damaged magnetic sensor cable Replace the magnetic sensor cable.

Track failures or bad track data Wrong tracker angle Set the tracker angle as shown in the applicable section.

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18-19. CONDITIONS FOR ROTOR SMOOTHING AND MECHANICAL TROUBLESHOOTING

The operator decides the satisfactory level of the 1/rev vibration. On a he licopter that is serviceable, refer to Table 18-6 for the conditions.

No dangerous effects have been measured for main rotor 1/rev levels of 1.0 Inches Per Second (IPS) or less. The level of main rotor 1/rev vibration is used to find the ride quality only. Main rotor 1/rev is not a wear or a fatigue problem. However, do not ignore sudden changes in the level of the main rotor 1/rev vibrations. If the level of the main rotor 1/rev vibrations changes suddenly, do an immediate and thorough inspection of the main rotor blades, the hub, and the control system to find the cause.

If you cannot get a satisfactory level of main rotor 1/rev vibration, there can be a mechanical problem. For the probable cause of many of the helicopter problems that you can have while you troubleshoot the main rotor 1/rev vibration, refer to Table 18-7. If y ou still

cannot get a s atisfactory level of main rotor 1/rev vibration, refer to Paragraph 18-30.

18-20. TASKS TO BE DONE AFTER YOU SMOOTH THE MAIN ROTOR

After you have smoothed the main rotor, do the tasks that follow:

1. Remove all of the RADS-AT components from the helicopter. Replace the swashplate nuts that were removed. Torque the nuts as specified in the applicable maintenance manual.

2. Apply corrosion preventive compound to th e exposed threads of any controls that were adjusted.

3. Write down all of the tab settings on a copy of the Main Rotor Adjustment Log. Refer to Figure 18-9.

Track failures or bad track data (Cont’d)

Bright blade leading edge in daily trim

Paint the lower surface of the lead-ing edge of the blade.

The sun Install the sunshield SA#29722100.

No track data at night Examine the reflective tape.

The TACHO is out of bounds when you examine the tail rotor or the driveshaft

The photocell tape is not in the cor-rect position

Lengthen the tape. Make sure that the red light shines on the photocell when the tail rotor is flapped or when the reflector is below the photocell on the driveshaft.

The sun Move the helicopter so that the photocell for the tail rotor does not point at the sun or so that the drive-shaft is not in the sun.

TACHO too high Make sure that the reflective tape is facing the photocell on one tail rotor blade only.

CADU will not communicate with the DAU

The DAU does not receive power Examine the DAU switch and the helicopter 28 VDC circuit breaker.

The tracker cable has a short cir-cuit

Remove the tracker cable. If the problem is solved, replace or repair the tracker cable.

Table 18-5. RADS-AT troubleshooting chart (Cont.)

PROBLEM CAUSE SOLUTION

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Table 18-6. Vibration conditions for the model 407 series

VIBRATIONFREQUENCY

OPERATINGCONDITION

VIBRATIONLEVEL (IPS)

RECOMMENDED ACTION

Main rotor 1/rev HOVER LEVEL <0.2 None

60 K 0.2<LEVEL<0.5 At operator discretion

100 K

120 K 0.5<LEVEL<1.0 Correct as soon as you can

VNE

L/DOWN 1.0<LEVEL Remove the helicopter from service. Correct before the next flight

Tail rotor 1/rev 100% Nr LEVEL<0.2 None

0.2<LEVEL Balance the tail rotor

Table 18-7. Helicopter vibration troubleshooting

PROBLEM PROBABLE CAUSE SOLUTION

1/rev vibration levels change Mast cones are loose Torque the mast cones

Worn pitch links Replace the pitch links

Damaged main rotor blade Repair or replace the main rotor

Worn mast cones Replace the mast cones

Blades are out of track or out of balance

Do the rotor smoothing procedure

1/rev vibrations in turns Swashplate breakout friction is low Adjust the swashplate friction

Torque sensitive 1/rev Worn or loose drive link and attach-ing hardware

Tighten or replace the drive link and/or the attaching hardware

Out-of-track condition because of an out-of-tab or out-of-roll condition

Do the main rotor smoothing proce-dure

1/rev vibration in a low power descent

Free play or wear between the slider and the swashplate

Replace all of the worn parts

2/rev vibrations Two blades are out of product bal-ance

Do the main rotor smoothing proce-dure and identify the unbalanced blades. Change one blade for another, or replace the applicable blades

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4. For future reference, store the final flight as a file in the CADU or in a computer.

18-21. TAIL ROTOR — BALANCING

18-22. TAIL ROTOR BALANCING — PURPOSE

This section describes the balancing of the tail rotor to reduce tail rotor 1/rev vibration. The installation of the RADS-AT permits these procedures to be done at the same time that you balance the m ain rotor in the INITIAL flight plan. You can do this with an extra accelerometer and an accelerometer cable that is 50 feet long. You can also balance the tail rotor by itself, with no main rotor balancing components installed.

18-23. TAIL ROTOR BALANCING RADS-AT — INSTALLATION

To balance the tail rotor assembly, install the RADS- AT as follows:

1. Install the DAU in the passenger compartment.

2. Attach the optical RPM sensor SA#29314708 to the tail rotor optical RPM sensor bracket SA#29338501 with #440 self locking nuts. Make sure that the lens is next to the vertical leg of the bracket (refer to Figure 18-12).

3. Remove the bottom forward screw of the 9 0 degree gearbox fairing. Use a longer screw and install the photocell bracket. Make sure that the photocell points forward and that the lens points at the tail rotor (refer to Figure 18-12).

4. Insert the accelerometer SA#28110900 into the hole on the s ide of t he photocell bracket. Make sure that the c able connector points toward the tail rotor. Attach the accelerometer with a self locking nut.

LEAVE A LARGE LOOP IN THE 50 FOOT ACCELEROMETER CABLE, TO MAKE SURE THAT IT STAYS LOOSE. THIS WILL PREVENT INTERNAL DAMAGE TO THE CABLE.

5. Connect the accelerometer end of the 5 0 foot accelerometer cable SA#29105600 to the tail rotor accelerometer.

4/rev vibrations Vertical fin is not secure Tighten the retaining bolts

Horizontal stabilizer is not secure Tighten the retaining hardware

Landing gear is not secure Tighten, repair, or replace the land-ing gear attachment fittings

Lateral engine mount is loose or worn

Torque the mounts bolts or replace the mounts

Pylon is not rigged correctly Do the pylon rigging procedure

Pylon mount failure Replace the defective pylon mount

Hub FRAHM assembly is worn or damaged

Replace all worn or damage parts

Hub FRAHM assembly is out of adjustment

Adjust the hub FRAHM

Table 18-7. Helicopter vibration troubleshooting (Cont.)

PROBLEM PROBABLE CAUSE SOLUTION

z

002

0

BHT-407-MM-2 Bell Helicopter

0

U60 0 0 0 0 0 0 00

PHOTOCELL,POINTING TOWARD

TAIL ROTOR BLADE

0

RUN CABLE DOWN SIDEOF TAIL BOOM

0 0

TEXTRON

0 0 //S 0 0(\\O O O O O OO

OACCELEROMETER

O

VIEW LOOKING UP FROM UNDER SIDET/R GEAR BOX

COWLING OMITTED FOR CLARITY

REFLECTIVE TAPEINBD OPPOSITE BLADE

Figure 18-12. RADS-AT tail rotor balance - Removal/Installation

e

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Figure 18-13. Schematic of RADS-AT installation for tail rotor balancing

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6. Install the optical RPM sensor cable and the 50 foot accelerometer cable SA#29105600 along the side of the tailboom that is opposite the tail rotor. Install the two cables from the t ailboom to the flight compartment. Safety both cables to the tailboom. This makes sure that none of the cables can get caught in the helicopter components that rotate and that the cables do not block the photocell lens.

7. On the DAU, connect the optical RPM sensor cable to T ACHO #2. Connect the 50 foo t accelerometer cable SA#29105600 to ACC4 (refer to Figure 18-12).

8. Connect the 28 VDC power cable SA#29104700 to the 28 V DC outlet on th e left hand side of th e instrument pedestal near the copilot cyclic control stick. Connect the other end of t he 28 VDC power cable SA#29104700 to the 28 VDC port on the DAU (refer to Figure 18-3).

9. Connect the cable SA#29325601 from the CADU to the CADU port on the DAU. Refer to Figure 18-12.

10. From the roll of reflective tape SA#10605000, cut two pieces of tape 3 inches (76.2 mm) long by 1 inch (25.4 mm) wide. Install one piece of reflective tape on the tailboom side of one tail rotor blade. Start 3 inches (76.2 mm) outboard of the outer blade bolt (refer to Figure 18-12). This is the t arget blade. As a counterweight, install the second piece of reflective tape on t he opposite tail rotor blade at th e same location, but on the side of the blade that is away from the tailboom.

11. Apply power to the DAU. Slowly rotate the tail rotor. Monitor the red light on th e back of the op tical RPM sensor. It should stay off until the reflector is seen by the sensor. When the sensor sees the reflector, the red light should come on. Flap the tail rotor to make sure that the light stays on for the entire flapping range. If the light does not come on or does not stay on, do the troubleshooting steps that follow:

a. Make sure that the optical RPM sensor is getting power.

b. Adjust the r eflector until the red light comes on. The photocell should be located in such a way that it is opposite to the center of the piece of reflective tape.

12. The RADS-AT is now installed and ready to balance the tail rotor. Refer to Figures 18-12 and 18-13.

18-24. TAIL ROTOR — BALANCE

Collect the tail rotor balance data and balance the tail rotor as follows:

1. With the RADS-AT installed, select 407 as the AIRCRAFT TYPE on the CADU main menu.


3. Use Tail as the flight plan. When the CADU is correctly set for the Tail flight plan, the CADU display is as shown in Figure 18-16.

4. To begin the measuring sequence, press F1. The test condition title for which data will be taken shows on the display (100% Tr).

5. Put the cyclic control stick in the center position and make sure that the collective control stick is all the way down. Press the directional pedals to the left 1.5 inches (38.1 mm). Operate the helicopter as c lose to 100% RPM as possible. On the CADU, the 100% Tr test condition is highlighted. Press the DO button to arm the RADS-AT. If a ll of the internal checks are successful, the te st condition title will appear at th e bottom of the display and the s ystem is armed to collect the data. When all of the data is collected, the RADS-AT shows that the te st is completed. Select FINISH. Select DIAGNOSTICS to review the tail rotor 1/rev levels. Make a decision whether any adjustments are required. If a TACHO error occurs during data collection, do the test again at least two times. If the TACHO error still occurs, do the steps that follow:

a. Shut down the helicopter.

b. Inspect the reflective tape and make sure that it is still in place and that it is still clean. If necessary, replace the reflective tape.

c. With power supplied to th e DAU, make sure that the red light on the back of the optical RPM sensor comes on when the reflector is in front of the optical sensor.

d. Make sure that the op tical RPM sensor is connected to TACHO #2 port.

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e. If all of th e above are correct, and if the red light still does not come on, remove the clear cover from the optical RPM sensor. Gently turn the brass screw clockwise to increase the gain until you feel a slight click. With the optical RPM sensor pointing at the reflector, the red light should come on during this step. Install the clear plastic cover.

6. If the tail rotor balance is satisfactory, go to Paragraph 18-26. If it i s necessary to balance the tail rotor, write down the recommended adjustments that you will make on a c opy of the Tail Rotor Adjustment Log tail rotor form. Refer to Figure 18-15.

NOTE

The RADS-AT is operating on set limits of 0.2 IPS for the tail rotor balance. If you want to decrease the level to below 0.2 IPS, press the DO button on the LIMITS display. The RADS-AT shows the adj ustments that are required to get a 0.0 IPS balance.

7. Do the previous steps 1. thru 6. again until the tail rotor is balanced (refer to Table 18-6).

18-25. TAIL ROTOR BALANCE — ADJUSTMENTS

The RADS-AT shows the tail rotor balance corrections as adjustments that you must make to th e outboard blade bolt of the target blade and to the chordwise balance arm (refer to Figure 18-14). If s mall span adjustments are necessary, you can use the i nboard blade bolt. To show an adjustment for the inboard blade bolt, use the EDIT ADJUSTABLES display to turn off the outboard span adjustment. At no tim e should two adjustments of the same type show on the display for both the inboard and outboard locations.

Adjust the tail rotor balance as follows:

1. Look at the adjustments that are recorded on the adjustment log.

NOTE

To do the adjustments, it is better to remove the weights than to add the weights. Remove the weights whenever possible.

2. Look at the location and at the size of the weights that are installed. You are permitted to install weights on both sides to make small adjustments.

3. To install the required span balance weight to the tail rotor blade bolt, at the applicable outboard span balance location or inboard span balance location (refer to Figure 18-14), do the steps that follow:

a. Remove the cotter pin and the nut from the blade bolt where the weight will be adjusted.

b. Use the components in Table 18-8. Adjust the washers as necessary to get the correct balance. Observe the general rules that follow:

• Make sure that one 140-007-25-22C4 washer is against the tail rotor blade on each side.

• Do a dynamic balance with the addition or the deletion of washers NAS1149F0663P, NAS1149F0632P, and AN970-6 in any combi-nation required to achieve the span balance. Determine the required length of bolts, NAS6606D30 (minimum) to NAS6606D38 (maximum), to accommodate the balance washers.

• On the inboard blade bolt at the inboard span balance location, the maximum number of washers permitted is six of AN970-6 and two of AN960-6162 in any combination. The total number of washers must not be more than nine.

• Divide the balance washers into two approxi-mately equal packages. One package will go under the head of the bolt and one package will go under the nut. Put the largest balance washers in position against the 104-007-25-22C4 washers. Make a stack of the remaining washers so that the lightest washer is next to the head of the bolt or the nut.

• Inspect the length of the bolt. If necessary, change the length of the bolt to make sure that you can install the cotter pin and that at least two of the bolt threads show beyond the end of the nut. If you change the bolt, adjust the stack of washers to make allowance for the change in the bolt weight.

c. When you have selected the bolt and the weight package (refer to Table 18-8), install and

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tighten the nut . Safety the nut with a ne w MS24665-283 cotter pin (refer to Figure 18-14).

4. Install the chordwise balance weight at the chord balance location as follows:

NOTE

To do the adjustment, it is better to remove the weights than to add the w eights. Remove the weights whenever possible.

a. Inspect the tail rotor to find the actual adjustment that must be made.

b. Use the balance parts in Table 18-8 and make up the balance package that you will install at th e selected chord balance location. Observe the general rules that follow:

(1) Dynamic balance by the addition or the deletion of washers NAS 1149F0432P, NAS1149F0463P and AN970-4, in a ny combination, as required to achieve chord balance.

(2) Each support may have a maximum of nine (9) washers in any combination. The bolt head is to face the pitch horn with a maximum of three (3) washers under the head. The bolt is to have a minimum length of NAS6204-1 and a maximum length of NAS6204-9 to accommodate the balance washers (refer to Figure 18-14).

(3) You can install weight at both locations to make small adjustments.

c. When you have selected the bolt, the washer, and the n ut combination, install the p ackage at th e chord balance location with the head of the bolt pointing towards the pitch horn. Install and tighten the nut (refer to Figure 18-14).

18-26. TASKS TO BE DONE AFTER YOU BALANCE THE TAIL ROTOR

When the t ail rotor tracking and/or balancing is complete, do the steps that follow:

1. Remove the RA DS-AT components from the helicopter.

2. Attach the gearbox fairing with a new bolt.

3. Apply corrosion preventive compound (C-104, BHT-ALL-SPM) to t he shank of any new bolts. Make sure that you do no t apply the c orrosion preventive compound to the threads.

4. Replace all of the nuts which look as if they have lost their self locking torque. Torque the nuts to their applicable values.

5. Apply corrosion preventive compound (C-101, BHT-ALL-SPM) to the bolts, the nuts, and the weight packages.

18-27. GENERAL VIBRATION — TROUBLESHOOTING

18-28. GENERAL VIBRATION TROUBLESHOOTING — PURPOSE

This section tells how to isolate the source of an unknown vibration.

18-29. GENERAL VIBRATION TROUBLESHOOTING RADS-AT — INSTALLATION

1. Look at the complaint. Decide at which location and for which test condition the problem vibration is felt.

2. Attach one or more accelerometers as close to the location of the pr oblem vibration as possible. Use either standard or locally made brackets. Point the accelerometer in the di rection where the vibration is felt. For example: vibration that is felt at the copilot heel rest will be in the vertical direction, while vibration that is felt in the pedals will be in the fore a nd aft direction, because of the position of the feet.

3. Use accelerometer cables and connect each accelerometer to a channel on the DAU. Make a note of which accelerometer is connected to which channel.

4. Make the cables secure so that they cannot touch the controls or get caught in the components that rotate while the helicopter operates. Make sure that the cables are clear of the engine exhaust.

T

T

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Figure 18-14. Balance location for tail rotor

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Table 18-8. Balance parts for the Bell model 407 tail rotor

PURPOSE DESCRIPTION PART NUMBER MASS (GRAMS) QUANTITY

OUTBOARD SPAN BALANCE

BOLT NAS6606D30 39.2 A/R

NAS6606D31 39.6 A/R

NAS6606D32 40.8 A/R

NAS6606D34 42.5 A/R

NAS6606D36 44.3 A/R

NAS6606D38 46.0 A/R

WASHER 140-007-25-22C4 3.7 Always installed

NAS1149F0632P 0.7 A/R

NAS1149F0663P 1.4 A/R

AN970-6 14.9 A/R

NUT MS141144L6 3.5 Always installed

COTTER PIN MS24665-285 N/A Always installed

INBOARD SPAN BALANCE

BOLT NAS6606D36 44.3 A/R

NAS6606D37 45.2 A/R

NAS6606D38 46.0 A/R

NAS6606D39 47.0 A/R

WASHER 140-007-25-22C4 3.7 Always installed

NAS1149F0632P 0.7 A/R

NAS1149F0663P 1.4 A/R

NUT MS14144L6 3.5 Always installed

COTTER PIN MS24665-285 N/A Always installed

CHORD BALANCE BOLT NAS6604-1 4.8 A/R

NAS6604-3 5.6 A/R

NAS6604-5 6.4 A/R

NAS6604-7 7.2 A/R

NAS6604-9 8.0 A/R

WASHER NAS1149F0432P 0.5 A/R

NAS1149F0463P 1.0 A/R

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5. Connect the comms cable SA#29325601 to the CADU. Connect the other end to the CADU port on the DAU.

6. Connect the 28 VDC power cable SA#29104700 to the 28 V DC outlet on th e left hand side of th e instrument pedestal near the copilot cyclic control stick. Connect the other end of t he 28 VDC power cable SA#29104700 to the 28 VDC port on the DAU. Set the power switch to the ON position.

7. The RADS-AT is now installed and r eady to troubleshoot the vibration.

18-30. VIBRATION DATA — COLLECTING

1. With the RADS-AT installed (Paragraph 18-8), select 407 as the AIRCRAFT TYPE for the helicopter.


3. Use VIBCHK or SPECTRUM as the flight plan. When the CADU is correctly set for the VIBCHK or SPECTRUM flight plan to examine the general vibration levels, the CADU display is as shown in Figure 18-17.

4. To begin the measuring sequence, press F1. The eight test conditions for which data can be c ollected are shown on the display. These test conditions indicate on which channel the data will be collected and for which frequency range. Data can be collected on one, all, or any combination of channels.

5. Operate the helicopter at the test condition where the vibration complaint was made.

6. Collect data for the specified channel by selecting the test conditions with the arrow keys and press the DO button. Do this again until you have collected all of the data.

7. When you have collected all of t he data, shut down the helicopter.

8. On the CADU, select SAVE AND EXIT or FINISH. To look at the data, select MAIN MENU. Press F2 and select SINGLE TEST. Select the test condition that you want to see and press the DO button. Write down the magnitude and the frequency of the significant peaks.

9. Refer to the frequency list in Table 18-1. Identify the source of the vibration for each peak. Inspect the source component for serviceability. Do the applicable balance or smoothing procedure for that source.

10. When you have completed the tes ts, remove all of the RADS-AT components from the helicopter.

18-31. RADS-AT — TECHNICAL SUPPORT

18-32. RADS-AT — AVAILABLE HELP

The people below can help you to add features to the RADS-AT software. You can get data about this software and help from the sources that follow:

Fax:

(450) 433-0272 (Attn.: Product Support Engineering based in Mirabel, Quebec, Canada)

18-33. RADS-AT — GROUND STATION

Bell Helicopter Textron has developed a ground station for the RADS-AT that will run o n any IBM PC or compatible computer. This ground station software is available free of charge from Bell Helicopter Textron.

18-34. RADS-AT — BULLETIN BOARD

Bell Helicopter Textron software for the RADS-AT is available from a Bulletin Board on Heli-Comm.

Heli-Comm: send a message to:

CHORD BALANCE (Cont’d)

AN970-4 7.0 A/R

NUT MS21042L4 1.4 A/R

Table 18-8. Balance parts for the Bell model 407 tail rotor (Cont.)

PURPOSE DESCRIPTION PART NUMBER MASS (GRAMS) QUANTITY

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• PSECANLIGHT (Product Support Engineering based in Mirabel, Quebec, Canada).

• RADSAT2 (Scientific Atlanta - Chuck Kemp, Commercial Field Representative).

• RADSAT (Scientific Atlanta - San Diego).

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Figure 18-15. Tail rotor adjustment log

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Figure 18-16. CADU main menu display for Tail flight plan

BHT-407-MM-2

Figure 18-17. CADU main menu display for VIBCHK and SPECTRUM flight plans

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407-MM-CH18

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