A SERVICE PUBLICATION OFLOCKHEED-GEORGIA COMPANYA DIVISION OFLOCKHEED AIRCRAFT CORPORATION

EditorJay V. Roy

Associate EditorsCharles I. GaleDon H. HungateJames A. Loftin

Art Direction & ProductionAnne G. Anderson

Cover: The Hercules radome isopen for access to the APQ-122radar antenna. The antenna ispositioned for fan beam operationand the pencil beam reflector isstowed aft.

Published by Lockheed-Georgia Company, a Division ofLockheed Aircraft Corporation. Information contained inthis issue is considered by Lockheed-Georgia Company tobe accurate and authoritative; it should not be assumed,however, that this material has received approval from anygovernmental agency or military service unless it isspecifically noted. This publication is for planning andinformation purposes only, and it is not to be construedas authority for making changes on aircraft or equipment,or as superseding any established operational ormaintenance procedures or policies. The following marksare registered and owned by Lockheed AircraftCorporation: “ “, “Lockheed”, “Hercules”, and“JetStar”. Written permission must be obtained fromLockheed-Georgia Company before republishing anymaterial in this periodical. Address all communications toEditor, Service News, Department 64-22, Zone 278,Lockheed-Georgia Company, Marietta, Georgia 30063.Copyright 1977 Lockheed Aircraft Corporation.

Vol. 4, No. 4, October - December 1977

CONTENTS

3

6

7

14

15

16

17

18

19

18

APO-1 22 Radar

System Operation

Subsystems

Glossary

Upper Cowling Hinge Lubrication

AC Voltage Regulators

Hercules MLG Ballscrew Lube

Side Lubrication Fitting Modified

Spare Nuts For V-Band Couplings

KC-130R Flight Simulator

StarTipBoost Pump Electrical Connector

DIRECTOR T.J. CLELAND

MANAGER D.L.BRAUND

FIELD SERVICE & INVENTORY MGMT A.H. McCRUM

CUSTOMER TRAINING E. L. PARKER

JETSTAR SUPPORT H.L. BURNETTE

SPARES STORES & SHIPPING J.K. PIERCE

MANAGER M.M. HODNETT

SUPPLY PROCUREMENT R.C. WEIHE

SUPPLY SYSTEMS & INVENTORY CONTROL C.K. ALLEN

SUPPLY SALES & CONTRACTS H.T. NISSLEY, JR.

SUPPLY TECHNICAL SUPPORT J.L. THURMOND

by Ralph A. Romanis, Electronics Engineer, Senior

Radar is an electronic accessory to man’s sensory equip-ment which makes it possible to detect certain objects atdistances beyond the normal range of vision. The detec-tion process is unimpaired by darkness, fog, smoke, ormost clouds, and permits the distance (range) to theobject to be determined, as well as the location (bearing)of the object with respect to the radar platform.

The word RADAR is an acronym coined from the descrip-tive phrase “radio detecting and ranging.” Radar worksby transmitting a pulse of energy and measuring theamount of energy reflected from the target and the timerequired for an echo of the pulse to return. The trans-mitted pulses are very brief in duration, and are spaced insuch a manner that a time (receive) period follows eachtransmitted pulse. The timing of the pulses depends onthe range that has been selected. During the receiveperiod, echoes from close-in targets will be received first,then those from medium range targets, and finally echoeswill be returned from targets at the maximum effectiverange of the system. When sufficient time has elapsed toallow echoes to be received from the most distant target plus constant evolutionary improvement, have converted aof interest, the transmitter is pulsed again and the cycle is cranky, cumbersome “secret weapon” into a reliable andrepeated. It is the linear relationship between range and indispensible aid for navigation and operational safety intime which is the basis of the ranging capability of radar. all sectors of the aviation field.

The radio waves used in radar are propagated at the speedof light, and the time interval required to complete a cycleis very short; measurable in terms of microseconds formost terrestrial targets. Such brief intervals cannot bedifferentiated or even detected by a human observer, butelectronically it is possible to distinguish between themwith a high degree of precision.

Also, knowing accurately the direction in which theantenna is pointing at the instant an echo is receivedpermits information about the bearing (azimuth) of anobject to be determined. Once both the range and thebearing of an object are known, it is possible to show theposition of the target and the radar platform relative toeach other on athe radar signals.

map-like display of the area covered by

The present generation of aircraft radar systems is theproduct of a long line of intensive developmental effortsin airborne radar which extends back to the days whenthe first bulky, unpredictable sets were crammed aboard

nightfighters and anti-submarine patrol craft in the early1940s. Although many of the basic principles of radarhave remained the same, the advanced solid-state units inuse today bear little functional resemblance to those ofthree decades ago.Major technological breakthroughs,

The APQ-122(V)5 radar set has been installed on manyHercules aircraft since 1975, beginning with aircraft serialnumber LAC 4653. This radar system is representative ofthe advanced, multi-purpose airborne navigational radarscurrently available. It is a pulse-modulated, solid-state,frequency-agile, X-band system which provides precisenavigational capabilities for long-range ground mapping,weather detection, and beacon interrogation.

The major components of the system are the antenna,antenna control, electronic control amplifier, receiver-transmitter, radar set control, cursor control, sweep gen-erator, and the radar stabilization control. In addition,both pilot and navigator are provided with azimuth-rangeindicator (display) units. The pilot’s indicator is a 5-inchdirect view storage tube display suitable for the highambient light conditions often present at this station. Thenavigator is provided with a 7-inch high-resolution cath-ode ray tube (CRT). In addition, the navigator can placeelectronic cursors over a specific target on the display andread out the range and azimuth of the target.

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COMPONENTS ANO LOCATION

~

SYSTEM OPERATION

There are three modes of operation available onAPQ-122(V)5 radar set; map mode, beacon mode,weather mode.

Map Mode

theand

The map mode is used to provide ground-mapping capa-bility for navigation. When used in the long-range map-ping mode, the radar set detects and displays targets suchas shore lines and mountains at ranges in excess of 200nautical miles. The following selectable range positionsare available :

3-30/1-

3-30/5-

50/10-

100/20-

6240/30-

Placing the selector knob in this position selectsvariable display range from O-3 to O-30 nauticalmiles with range marks at 1 nautical-mile incre-ments.

This position selects variable display range fromO-3 to O-30 nautical miles with range marks at 5nautical-mile increments.

At this position, a O-50 nautical-mile displayrange is selected with range marks at 10 nauti-cal-mile increments.

This position presents a O-100 nautical-miledisplay range, with range marks at 20 nautical-mile increments.

When the range is set at this position, the maxi-mum range of the radar set (approximately 240nautical miles) is selected. Range markers areprovided at 30 nautical-mile increments.

Range delay is available when the range switch is set at the50/10, 100/20, or 240/30 positions. When this functionis selected, the sweep is delayed so that an adjustable

segment (O-3 to O-30 miles) of the displayed range is pre-sented, generated about the range cursor. The rangecursor may be positioned at any point from 0 to 240nautical miles, depending upon the range switch position.The effect of range delay is to expand the display at longrange, thereby highlighting a target.

C U R S O R C O N T R O L P A N E L

Beacon ModeThe beacon function is available in all ranges. When thebeacon mode is selected, the radar set’s magnetron isdriven to a fixed frequency (9375 MHz) and the frequen-cy select and the frequency agility switches are renderedinoperative.

The beacon mode provides the tactical capability of inter-rogating an X-band beacon. The beacon reply is coded toenable an identification to be made, and can originatefrom either a ground station or an airborne station. Sincethe beacon reply is a transmitted signal, it can be detectedat longer range than the echo of a radar pulse from con-ventional targets, although it still must be within the lineof sight of the radar transmitter. This mode is often usedto find aircraft of interest such as tankers for aerial refuel-ing.

Weather ModeThe weather function is also available in all ranges. In thismode of operation, the radar set detects and displaysstorm fronts, heavy rainfall areas, or other turbulentweather cells containing precipitation at distances of up to150 nautical miles.

Photograph of APQ-122(V)5 radar display

of Florida Gulf coast area - 240 NM range

with 30-mile range marks. Radar in “north”

stabil ization with aircraft f lying 330° true

head ing . (Returns are shown from St.

Petersburg on the far right, to New Orleans,

on the far left.) Photo courtesy of T e x a s Instruments.

Photograph of APQ-122(V)5

radar display of weather cell

with iso-echo contouring.

Radar in �weather� mode,

50 NM range with lo-mile

range marks. Antenna in

sector scan.

Selection of the weather mode activates the ISO-ECHOcontrols on the pilot’s indicator and the cursor controlpanel, enabling the operator to vary the threshold atwhich storm contouring is displayed. The control permitsthe selective rejection of echos from light, medium, heavy,or excessively heavy precipitation. This allows an evalua-tion of the severity of storm cells to be made.

SUBSYSTEMS

The APQ-122(V)5 radar set is divided into three majorsubsystems: the antenna, the receiver-transmitter, and theindicators. A closer look at each of these subsystems willhelp clarify their functions.

Antennaor a fan

Antenna Subsystem

The antenna subsystem focuses and directs radio fre-quency (RF) energy to and from the receiver-transmitter,and provides the interface between the aircraft and theground over which the aircraft is flying. In addition, itgenerates positional information to accurately tie thebearing of targets in the azimuth plane to that of theaircraft for display on the navigator’s and pilot’s indi-cators. In the weather mode, antenna tilt angles are alsoused. This permits the height of weather cells to be deter-mined so that not only the bearing of the cell is known,but also its altitude relative to the altitude of the aircraft.The antenna is stabilized with pitch and roll data suppliedfrom the number 1 or number 2 flight director gyros.

The functions of the antenna subsystem are carried out bythe antenna and the electronic control amplifier (ECA)and are controlled by the antenna control, radar set con-trol, and radar stabilization control.

The antenna has two reflectors: One reflector radiates apencil beam for long-range search and navigation, andweather detection. The other reflector radiates a fanbeam which is used for ground mapping. The fan andpencil reflectors are mounted back-to-back on the antennapedestal; they are positioned in azimuth and stabilized inpitch, roll, and tilt by a four-gimbal servosystem. Eachreflector is selectable by a signal which comes from aswitch marked BEAM-PENCIL/FAN on the radar setcontrol. Because of the back-to-back configuration of theantenna reflectors, it is necessary to reverse the directionof the rotation of the tilt drive when changing reflectors.To initiate this change, a relay is energized which reversesthe inputs to the tilt control circuit. This causes the tiltgimbal to reverse its direction of rotation.

ANTENNA CONTROL PANEL

reflectors are reversible for eitherbeam. Ph to o courtesy of Texas Instruments.

a pencil

Input information is received by the ECA from the air-craft compass system, number 1 or number 2 flight

8director gyro, the radar set control, and the antennacontrol. These inputs generate signals which control thepositioning of the antenna. The selection of gyro number1 or gyro number 2 is made through a switch mounted onthe radar stabilization control panel. Should both gyrosfail, there is an off position (STAB OUT) which selects azero reference for the radar antenna and “locks” it to theairframe. This position can also be used to check theantenna zero alignment during installation and groundcheckout, and during troubleshooting.

RADAR STABILIZATION CONTROL

PANEL

The ECA passes antenna positional information to thenavigator’s CRT indicator and processes the feedbackinformation from the four antenna drives (roll, pitch, tilt,and azimuth) in such a way that the four loops are drivenin a controlled manner. Loss of control, or a hard failurein any of the four loops, will result in an antenna or ECAfail indication on the ECA unit mounted in the radome.At the same time, the ANT FAIL light will be illuminatedon the radar set control in the flight station.

Receiver-Transmitter SubsystemThe receiver-transmitter (R-T) subsystem transmits andreceives X-band RF energy and develops the video andmaster trigger pulses used by the pilot’s and navigator’sindicators. The R-T subsystem consists of the radar setcontrol and the R-T. The following controls, located onthe radar set control, are the principal ones used tooperate the R-T:

FTC - Controls fast time constant, on-off.

STC - Adjusts sensitivity time control in depth and range.

RCVR GAIN - Controls receiver gain.

AGILE - Selects fixed (off) or varying (on) frequency on apulse-to-pulse basis.

RF PWR - Directs RF power to antenna or dummy load.

MODE - Selects mode: off, standby, map, beacon, orweather.

RANGE - Selects each of the five display ranges.

FREQ - Permits selection of nine discrete operatingfrequencies.

Transmit Mode - The transmit mode is initiated by movingthe mode switch from OFF to STBY (standby). Notethat a mechanical interlock in the bottom of the switchknob must be released before the switch can be returned

to the OFF position. This prevents the operator frominadvertantly deenergizing the set. The STBY position isa warm-up and test position in which 115 VAC, 3-phasepower is supplied to the system ~ in particular to thesynchronizer - to generate the radar timing pulses:modulator trigger, pre-master trigger, master trigger, andsystem blanking. (System blanking is not used in thesystem as configured.) The timing pulses occur at a pulserepetition frequency (PRF) of 250, 1,000, and 2,000 Hz,determined by the positions of the mode and rangeswitches on the radar set control. At the completion of a3-minute time delay, power is applied to the modulator,allowing the modulator to fire the magnetron. Themodulator produces high voltage pulses which fire themagnetron at a PRF and pulse width (PW) determined bymode and range selections as follows:

Mode Range (NM) ) PRF 1 Pulse Wid t h

MAP 3-30/lMAP 3-30/5MAP 50/10MAP 100/20MAP 240/30BCN All RangesWEA All Ranges

2 KHz2 KHz1 KHz250 Hz250 Hz250 Hz250 Hz

0.3 0.3 0.6 4.0 4.0 2.35 4.0

The magnetron produces high power (60 KW minimum)transmitted pulses at a frequency determined by the selec-tion made on the radar set control. The control has nineselectable frequencies in 50 MHz steps and is inhibited

during the BCN mode.The nine frequency steps are asfollows:

Frequency Control Generated FrequencyPosition (MHz)

1 91002 91503 92004 92505 93006 93507 94008 94509 9500

Frequency agile operation causes the frequency to bevaried below the selected frequency to reduce scintillationin the returned echo display. It is initiated when theAGILE switch is placed in the ON position. Frequencyagility is inhibited in the beacon mode.

The transmitter pulses are applied from the magnetronthrough a circulator and a waveguide switch to theantenna. Should it be necessary to check power output orto have the radar in the transmit mode, but not desirableto have RF energy being radiated by the antenna, there isa built-in dummy load. By switching from ANT to LOADon the radar set control, RF energy is switched to thedummy load and a warning light is illuminated on the

9

10

radar set control panel. The power going to the dummyload is picked off by a 40 db coupler and is made availableat a waveguide test port for power measurement, PW, andPRF checks. A 71 db pick-off is used to monitor thepower out. Should the peak power of the transmittedpulse fall below 30 KW, the power monitor generates afailure signal, the R-T FAIL light on the radar set controlin illuminated, and the transmitter is shut down.

Receive Mode - The receiver is a superheterodyne typewith a 60 MHz intermediate frequency (IF). The solid-state local oscillator is frequency tunable throughout therange of the receiver. In map and weather modes, theautomatic frequency control (AFC) drives the local oscil-lator 60 MHz above the transmitter frequency. The AFCcompares the coarse frequency analog and fine frequencyanalog signals from the magnetron tuning circuits andgenerates a DC voltage which tunes the local oscillator tothe approximate magnetron frequency. The transmitterpulse from the magnetron is attenuated by 74 db andapplied to a frequency discriminator in the AFC. Thecompared output of discriminator and coarse and fineanalog signals generates a DC offset voltage which finetunes the local oscillator to exactly 60 MHz above thetransmitted frequency.When the beacon mode is select-ed, the local oscillator is crystal controlled to generate afrequency 60 MHz above the 9310 MHz signals receivedfrom radar beacon station.

The received echos are applied through the waveguideswitch, the circulator, and a transmit-receive limiter to theIF mixer diodes. The T-R limiter is a passive device usedto protect the mixer diodes from very strong echos such

as are experienced from hangar doors and from nearbyaircraft transmitting directly into the antenna. Thoughthe T-R limiter is an adequate protective device, it isrecommended that care be taken to transmit only awayfrom nearby buildings and other aircraft to prolong thelife of the mixer crystals which are inherently delicatedevices.

The received echos are mixed with the local oscillatoroutput to generate a 60 MHz IF signal. The resultingsignal is amplified by a preamplifier and logarithmic post-amplifier to provide a gain of approximately 60 db.

The 60 MHz IF signal is detected, and the resulting videois supplied to the navigator’s indicator where it is split: apilot’s video signal is sent to the sweep generator forfurther processing and final display on the pilot’s indi-cator.

The sensitivity time control (STC) is a gain reductiondevice to cut down the amplitude of close-in targetswhich, due to their proximity, appear around the centerof the plan position indicator or at the vertex of a sectorscan, causing clutter and a large bright area. The STC

reduces the brightness of large close-in targets so that theyare de-emphasized to allow targets at greater ranges toappear at approximately the same amplitude/brightness,provided they have the same reflectivity. STC can beconsidered as a modification of the fan beam to de-emphasize close targets. STC range and depth controls areprovided on the radar set control. The STC range is vari-able from 0 to approximately 20 nautical miles. In theWEA mode the STC controls are inoperative and a fixedmaximum STC is provided to 40 nautical miles.

Fast time constant (FTC) is a device used to break upvideo in the receiver to better accentuate hard targets andcut down on clutter. FTC breaks up signals of long dura-tion, leaving less voltage amplitude as integrated by thedisplay phosphor. This reduces the tendency of the signalintensity to “creep” on the phosphor, permitting sharper,more definitive outlines of complex targets and the virtualelimination of clutter.

Receiver noise is continuously monitored by an automaticnoise figure monitor. During each transmit dead time, thenoise figure generator sends a noise pulse through thereceiver. Should the IF noise level be greater than theinjected noise pulse level by more than 2 db, a receivernoise figure fail signal is generated, and the R-T fail lighton the radar set control is illuminated.

A built-in test function of the R-T unit continuouslymonitors the following signals: power supply (+/- 20

VDC), waveguide switch, power monitor (output), noisefigure, master trigger,beacon mode, frequency select,AFC, AFC crystal 1, AFC crystal 2, IF crystal 1, and IFcrystal 2.

A failure of any of the above causes the R-T fail light onthe radar set control to illuminate. A test meter andswitch are installed on the forward corner of the R-T.Should the R-T fail light on the radar set control illumi-nate, the test switch and meter indication on the R-Tshould be monitored to accurately determine where thefailure has occurred.

Indicator SubsystemThe indicator subsystem displays the video from the R-Tunit on the 7-inch navigator’s CRT and the S-inch, pilot’sdirect view storage tube. The indicator subsystem in-cludes the navigator’s and the pilot’s display systems.

The navigator’s display system consists of the navigator’sindicator, cursor control, and the radar set control.

The navigator’s indicator processes the incoming videofrom the R-T and, using master trigger, range, mode, andscan select information, displays the video on the 7-inchCRT, requiring minimal front panel controls. To providethe processing, the navigator’s indicator has the followingfunctional loops: the timing generation loop, sweepgeneration loop, deflection and focus loop, video pro-cessing loop, and the power supply loop.

12

The timing generation loop generates the range gate. Therange gate master trigger is derived from the transmitterand is used as time or range zero for the range gate. Therange gate length is controlled by the range selection onthe radar set control. A gate is generated which will be apositive pulse 618 +/- 10 wide in the 50 nautical-milerange. The pulse width or the gated range is used to gatethrough video and to set up sweep lengths for the display.

The timing generation loop also provides the headingmark, range marks, and range cursor.

The sweep generation loop produces the selectedhorizontal and vertical sweeps, the lengths of which aredirectly proportional to the range gate. The horizontaland vertical sweeps are derived from antenna positioninformation in the radar set control, which presents theposition of the antenna relative to the azimuth stabiliza-tion that has been selected. Either magnetic north, or theaircraft’s heading may be displayed at the top of theindicator screens.

The deflection and focus loop develops the horizontal andvertical sweep voltages which are applied to the CRTdeflection yokes. This loop also produces the dynamicand static focus voltages required to focus the electronbeam onto the face of the display. The video processing

PILOT TRlGGERl

FROM NAV IND

TIMINGMODE

RADAR G E N E R A T I O N

RANGE LOOPSET

CONTROL SCAN

COMMANDS

MODE RANGELOGIC GATE

ANTENNA POSITIONFROM ECA

VED ANTENNA POSITION-ROM NAV INDICATOR

SWEEPGENERATION

LOOP

loop combines the raw video, the range marks, and therange cursor into a composite video signal, and applies thissignal to the cathode of the CRT. The loop also generatesan unblanking signal which is combined with the headingmark and azimuth cursor and applied to the control gridof the CRT. The unblanking signal is intensity-com-pensated to correct for the difference in selected ranges,pulse repetition frequency, and scan speeds.

The power supply loop generates the low voltage powerrequired by the processing circuitry and the high voltage(+ 8 KV) power required by the CRT. The power suppliestransform the low-voltage power from the 3-phase aircraftpower which is applied through individual circuit breakersand line filters. The + 40 VDC output of the powersupply is chopped at a 1.500 Hz rate and applied to thehigh voltage power supply to produce the +8 KV anodevoltage for the CRT.

The pilot’s display system is similar to the navigator’s, butdue to size restrictions at the pilot-copilot stations, thepilot’s indicator is made as small as possible and most ofthe signal processing is done in the sweep generator unit.

The pilot’s display system has the same loops as thenavigator’s display system, and some of the navigator’sindicator and sweep generator printed circuit cards areinterchangeable.

13

SWEEP GENERATOR VIDEO FROM PI LOT lNDlCATORNAV INDICATOR

t

RANGE M A R KMIXED VIDEO VIDEO

VIDEO VIDEORANGE GATE PROCESSING PROCESSING

HIGH VOLTAGE

LOOPPOWER SUPPLY

UNBLANKING/ LOOP UNBLANK ING

HEADING MARK ENABLE HEADING MARKER

UNBLANKING

FLOOD GUNS

5 INCH

SELECTEO HORIZONTAL SWEEP

SELECT&Q VERTlCAL SWEEP

+Fiv - 5.2V +15v +4ov

PILOT DISPLAY SYSTEM DIAGRAM

LOOP

The timing generation loop, sweep generation loop, videoprocessing loop and part of the low voltage power supplyloop, together with the built-in test loop, are contained inthe sweep generator. Additionally, direct view storagetube processing circuits and the deflection loop, togetherwith low and high voltage power supplies, are contained inthe pilot’s indicator.

The pilot’s video and the pilot’s trigger are passed to thesweep generator from the navigator’s indicator. Theheading mark trigger is generated in the sweep generatorand sent to the navigator’s indicator. The pilot’s indicatordoes not display the electronic cursors. It also must beslaved to the azimuth stabilization of the navigator’sindicator in order to display north-up oriented infor-mation.

In the approximately two years that the APQ-122 radarsystem has been in service with the Hercules fleet, it hasproved to be effective, versatile, and reliable. All solid-state construction and conservative engineering have

contributed to an outstanding record of dependability andlow maintenance cost. In all respects of operation andmaintainability, this system has proven to be a worthyreplacement for the APN-59.

Of course no electronic system will remain trouble-freeindefinitely, and also with the APQ-122 the time eventual-ly comes when service is needed. In general, the servicingprocedures for the APQ-122 are quite straightforward, butbecause the system is still relatively new, some customersare unsure of the best way to evolve efficient trouble-shooting methods. To assist these operators in reducingthe time required to service their APQ-122 radar sets andreturn their aircraft to operational status, we will presenta special article on troubleshooting this system in an up-coming issue of Service News.

GLOSSARY

14

If radar is not your speciality and it has been a while sinceyou have studied electronics, the following glossary maybe of some help.

X-band - A radar frequency band extending from 5,200to 11,000 MHz.

cursor - A mechanical or electronically-generatedmovable line used as a reference to denote heading,azimuth, etc., on a radar indicator.

loop - In radar, the term loop is often used to define aseries of circuits designed to perform a specific function:as in sweep generation loop, power supply loop, etc.

trigger -- A signal or pulse used to initiate action inanother circuit.

blanking/unblanking - An electronic process in which thebeam of a cathode ray tube is turned off or on.

magnetron - A specialized type of electron tube which iscapable of producing high power RF energy in the micro-wave region of the radar band.

waveguide switch -- A switch in the transmission (wave-guide) line which directs RF energy to one device oranother.

circulator - A microwave coupling unit that has three ormore terminals arranged in such a way that energy enter-ing one terminal is transmitted to an adjacent terminal ina particular direction.

frequency discriminator - A device in which amplitudevariations are derived in response to frequency or phasevariations.

DC offset voltage -- The difference in DC voltage at twoinputs of an operational amplifier required to bring theoutput voltage to zero.

mixer -- A circuit that generates output frequencies equalto the sum and thedifference of two input frequencies.

frequency analog -given frequency.

gate - A circuit usedpassanother signal.

A voltage which is equivalentto a

as a switch or“gate” to inhibit or

superhetrodyne - A method of reception in which thereceived frequency is mixed with a local oscillator fre-quency to produce a fixed intermediate frequency whichmay be conveniently amplified and controlled.

chopper - An electronic device used to interrupt a DCsignal at regular intervals to permit amplification by anAC amplifier.

scintillation - A “sparkling” effect in the display of aradar return signal caused by random ground objectspeculiarly reflective to the transmitted radar frequencybeing used.

by W. C. Barre, Service Representative To lubricate the hinges, the usual procedure is to pull the

If you have experienced difficulty lubricating the pins inthe Hercules QEC center beam hinge, here is an ideawhich may be helpful.

Access to the top of the Hercules’ engine accessory sec-tion is provided by two hinged panels in the engine nacellecowling. Two hinges for each panel are bolted to thenacelle center beam, and Paneloc fasteners along the open-ing edges secure these panels in the closed position. Thepanels can be removed after opening by pulling the hingepins; each pin is secured with a castellated nut and acotter pin.

pins and remove the panel. After the pins and hinges arecleaned and lubricated, installation steps are in reverseorder of removal The difficulty comes with aligning bothhinges at the same time to install the pins. Each uppercowling panel weighs over twenty-two pounds. Thisdoesn’t seem heavy until you try a one-man balancing actto install one of them.

These removable pins receive a dry film lubricant in pro-duction, and as a rule this is all they need until removal ofthe QEC. No periodic schedule is specified for lubricatingthese hinges between overhauls; therefore, operating con-ditions and the inspection schedule set by the Herculesoperator should determine when the hinges are to be ser-viced.

Two I Hercules operators have eliminated the necessity ofremoving the pins and panels for this job by installinga standard grease fitting in the ccntcr of each hinge. Thisis illustrated in Figure 1 . The fittings allow use of astandard grease gun to apply an aircraft general-purposelubricating grease such as MIL-G-21 164 or MIL-G-33827.The latter specification replaces MIL-G-77 1 1 which maystill appear in some manuals.

Installation of the grease fittings is at the option of theoperator. Lockheed has no plans to install grease fittingsin these hinges in production because problems with thehinges in the field have been minimal.

Figure 1 Production installation of a cowling hinge with pin. Dry Figure 2 Hinge modified to allow lubrication with grease.

lubrication is standard.

16

Some Hercules operators have asked which voltage regu-lator is to be used with which AC generator. The follow-ing list of generators and their matching voltage regulatorsshould answer most of these questions.

Generator

A50J207-4Westinghouse Brush Type

Voltage Regulator

A40A1750

976J480-2Westinghouse Brushless

A40Al750-2

28B58-9-ABendix Brushless

20B95-4-A

2CM353CID/HGeneral ElectricBrushless

3S2060DR113Al

3 1220-004Lear SieglerATM Brush Type

51107-003

AC voltage regulators on the electrical control and supply rack justforward of the 245 bulkhead.

Any of the following generator control panels can be usedwith any of the generator and regulator combinationslisted previously.

A mismatch of a generator and a voltage regulator willresult in voltage regulator failure because of the differ-ences in the designed interaction between generator andregulator. Extra precautions are necessary for Herculesoperators having a mix of airplanes that may use morethan one type of generator.

Effective at serial LAC 4733 and up, certain versions ofHercules airplanes incorporate the Bendix brushless gen-erator (P/N 28B58-9-A) and its matching voltage regulator(P/N 20B95-4-A in lieu of General Electric or Westing-house. On these airplanes precautions have been taken toprevent mismatch.Caution decals are installed on theBendix components and on the aircraft structure.

side lubrication fitting modifiedby C. R. Bush, Design Engineer Specialist

The Calco 8353 main landing gear ballscrew assembly hasbeen installed on Hercules airplanes subsequent to serialnumber LAC 4547 and is the preferred spare for allHercules. It is normally very reliable and has given goodservice. However, as with any mechanical device, therehave been some failures. This article discusses the majorcause of these failures and the preventive action.

Premature failure of Calco ballscrews was experienced byone operator during Arctic operations. The ballscrewswere analyzed by the manufacturer and his report in-dicated that the failure was caused by excessive grease inthe ball nuts. An excessive amount of grease, coupledwith low temperatures under Arctic conditions or ataltitude during flight, can cause a problem in that thegrease may stiffen sufficiently to impede motion of theinternal balls. This motion restriction, plus a light bearingload condition, tends to cause the balls to skid rather thanroll. Skidding can cause ball flat-spotting and resultantdamage to the thin chrome plating on the screw and thenut.

On Hercules aircraft serial number LAC 4669 and up, andon spare Calco 8353 ballscrew assemblies shipped afterMay 10, 1976, the lubrication fitting on the side of theball nut is modified to exclude the spring and ball. Thisprovides a path through which excess grease can be ex-pelled from the ball nut during gear operation.

Field modification of the MS1 5001-l side-mounted lubri-cation fitting to provide similar protection against thebuild-up of excessive amounts of grease is also recom-mended: Remove the fitting (Figure 1) from the ball nut(accessible from the wheel well) and file away the base of

Figure 1ACCESS TO BALL NUT GREASE FITTING BEHIND STRUT.

17

Figure 2 BALL NUT AND SCREW ASSEMBLY.

the fitting in order to remove the spring and ball. Discardthe spring and ball and reinstall the fitting after carefulcleaning.

Operation of a ballscrew with its circulating balls is similarto that of a ball bearing, in that only a third of the avail-able volume should be filled with grease. Using a hand-operated grease gun, lubricate the ball nut with four“shots” of MIL-G-23827A grease (Aeroshell 7 or equi-valent) at each 200-hour “B” check. MIL-G-21164Cgrease (Aeroshell 17 or equivalent) is no longer recom-mended for this application because of its tendency toseparate and dry out.The lubrication fitting on top ofthe ball nut lubricates only the mounting flange on theoutside of the ball nut and it is not modified.

SPARE NUTS for V-BAND COUPLINGS

The sections of the bleed air ducts in the Hercules and The price of a nut can” save the cost of a coupling assem-JetStar are connected by V-band couplings, sometimes called Marman clamps. While the major use for the‘ V-

bly. Also, stocking spare nuts in both sizes may save con-

band couplings is on the bleed air ducts o f the pneu-siderable time. ‘Tag them to prevent mixing with other

nuts which may be similar only in appearance .matic systems, they are also used on other components.

These couplings are practically trouble free if they are The stainless steel, silver-plated.‘nuts that come with theseinstalled according to the instructions in the aircraftmaintenance manual and/or T.O. 1-1A-8 Structural Hard-

couplings have a castellated appearance as a result of cutsmade in the top to allow a self-locking spring action.

ware.

The nuts used to tighten the clamps on the V-band cou-plings may, in time, become worn or damaged and needreplacing. While the nuts are relatively inexpensive, theyare of unique design - special for this application. Inmany cases, it has been necessary to replace an otherwiseserviceable coupling assembly because a spare nut was notin the local inventory. Substitution with a nut which doesnot meet the specification of the original nut is notallowed.

While this article does not cover all couplings nor detailtheir installation, we have listed the part numbers for thetwo nuts used for the majority of V-band couplings.

18

Boost Pump Electrical Connector

We have received several field reports concerningpins shorting in the electrical receptacle for thesuction boost pump. This is apparently due topoor mating of the aircraft electrical plug andpump electrical receptacle, which allows con-tamination to collect around the base of the pins.

The wiring diagram for the hydraulic suctionboost pump has been changed to reflect anenvironmental plug, P/N MS3108R18-4S, in lieuof the standard P/N MS3108B18-4s plug. Ifaircraft at your facility are experiencing burnt pinproblems at the suction boost pump connection,we recommend installing the P/N MS3108R 18-4s

plug.New environmental plug for hydraulic suction boost pump.

KC-130RFlight Simulator

Operation of the complex modern-day airplane requiresskills which must periodically be monitored and rein-forced through training. Much of this training is accom-plished with aircraft flight simulators which have gainedan increasingly important role in the training programs ofboth commercial and military operations. The use of aflight simulator in lieu of an actual aircraft offers distinctadvantages; safety, cost, schedule flexibility, and versa-tility in training missions.

The U. S. Marine Corps operates KC-130F and KC-130Rtanker aircraft and their flight crew personnel receivetraining on flight simulators designed and built by theSinger Company. A KC-130F simulator is being modifiedfor use as a Cockpit Procedures Trainer (CPT) whileanother KC-130F simulator is being updated to theKC-1 30R configuration.

The CPT will have full systems capability with the excep-tion of radio and navigational aids and will be able tosimulate 200 different malfunctions.

The KC-130R flight simulator will be capable of simulat-ing up to 900 different malfunctions and will employ thelatest state-of-the-art features such as a six-degree-of-freedom motion system with a visual display. In additionto the normal features, it will also simulate such things asturbulence, rain, hail, and wind shear. Of special impor-tance to inflight refueling operations, the simulator will becapable of depicting airborne rendezvous between thetanker and the receiving aircraft. Progress and responsesof the crew can be monitored on a video system with slowmotion and instant replay capabilities.

Training is provided by the Simulator Section of the 3rdMarine Air Wing MAWTUPAC (Marine Air Weapon Train-

ABOVE: The KC-130R Hercules simulator in a nose up atti-tude. LEFT: Instructor’s station for the Hercules simulator.Photos courtesy of The Singer Company.

ing Unit Pacific), at El Toro, California. The Officer-In-Charge of the Simulator Section is Captain F. B. Smith.The El Toro simulator facilities are also used to trainpersonnel from other organizations such as the U. S. CoastGuard and the U. S. Navy.

Among the different training courses conducted at thefacility are basic C-130 pilot familiarization, refresherpilot training, squadron quarterly emergency procedurereviews, and a ground school and simulator training forflight engineers. The KC-1 30F/R training supplied by the3rd Marine Air Wing is a valuable asset to the successfuloperation of the Marine Corps’ C-130 fleet and demon-strates the effectiveness of simulator training.

CUSTOMER SERVICE DIVISION LOCKHEED·GEORGIA COMPANY A OIVJJ•O~ QIJ t.OC~+'ElO A.l"ICFlAfT COAf'CRATIO~ YA-ttTTA 0.IOlllCIA. >OOfil

U.S. Marine Corps Kc-·1JOR Hercules and flight simulators. See page 19.