LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …
Transcript of LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …
![Page 1: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/1.jpg)
AFFTC-PA-11014
LESSONS LEARNED WHILE MEASURING
FUEL SYSTEM DIFFERENTIAL PRESSURE
MARK HEATON
AIR FORCE FLIGHT TEST CENTER EDWARDS AFB, CA
10 MAY 2011
AFFTCm
Approved for public release A: distribution is unlimited.
AIR FORCE FLIGHT TEST CENTER EDWARDS AIR FORCE BASE, CALIFORNIA
AIR FORCE MATERIEL COMMAND
UNITED STATES AIR FORCE
![Page 2: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/2.jpg)
REPORT DOCUMENTATION PAGE Form Approved
OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
1. REPORT DATE (DD-MM-YYYY)
10-05-2011 2. REPORT TYPE
TECHNICAL PRESENTATION 3. DATES COVERED (From - To)
4. TITLE AND SUBTITLE
Lessons learned while measuring fuel system differential pressure
5a. CONTRACT NUMBER
5b. GRANT NUMBER
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S)
Mark Heaton
5d. PROJECT NUMBER
5e. TASK NUMBER
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) AND ADDRESS(ES)
8. PERFORMING ORGANIZATION REPORT NUMBER
AFFTC-PA-11014
9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES)
AFFTC 412 Test Wing ENI Edwards AFB, CA 10. SPONSOR/MONITOR’S ACRONYM(S)
N/A
11. SPONSOR/MONITOR’S REPORT
NUMBER(S)
12. DISTRIBUTION / AVAILABILITY STATEMENT
Approved for public release A: distribution is unlimited.
13. SUPPLEMENTARY NOTES
CA: Air Force Flight Test Center Edwards AFB CA CC: 012100
14. ABSTRACT
A recent aircraft project required the measurement of differential pressures across a fuel filter during engine operation. Early testing
showed intermittent noise in the system. Additionally, transducers were failing. Attempts to troubleshoot the problem led to the discovery
of unexpected large pressure transients within the fuel system which were causing the “noise” and damaging the transducers. Attempts
were made, with some success, to gather the data without extensively modifying the existing system. This presentation provides a brief
review of what was done and what was learned from this program.
15. SUBJECT TERMS
Fuel Pressure Transducer, Differential Pressure Transducer, Pressure Noise, Data Acquisition System (DAS)
16. SECURITY CLASSIFICATION OF:
Unclassified
17. LIMITATION OF ABSTRACT
18. NUMBER OF PAGES
19a. NAME OF RESPONSIBLE PERSON
412 TENG/EN (Tech Pubs)
a. REPORT
Unclassified b. ABSTRACT
Unclassified c. THIS PAGE
Unclassified None
19b. TELEPHONE NUMBER (include area
code)
661-277-8615 Standard Form 298 (Rev. 8-98)
Prescribed by ANSI Std. Z39.18
![Page 3: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/3.jpg)
1
Air Force Flight Test Center
Mark Heaton
412TENG/ENI
661-275-4426
I n t e g r i t y - S e r v i c e - E x c e l l e n c e
Approved for public release; distribution is unlimited.AFFTC-PA No.: 11014
War-Winning Capabilities … On Time, On Cost
Lessons learned while measuring
fuel system differential pressure
10 May 2011
![Page 4: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/4.jpg)
2
Overview
• Requirement
• Method
• Early problems
• Resolution
• Results
• Lessons learned
![Page 5: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/5.jpg)
3
Program Requirement
• Demonstrate fuel pressure characteristics
– Ice buildup on strainer
– In flight
• Normally: 0.2 psid
– Clean filter
• Strainer has bypass valve
– Opens when filter clogs
– Opens at ~ 1 psid
– Full flow at 2.1 psid
• Blocked strainer
![Page 6: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/6.jpg)
• Differential Pressure across strainer
– Engines already instrumented
• Video of strainer in housing
– Intrusion of camera or borescope in fuel
– Extensive modification to strainer housing
– Would ice be obvious?
• Require further lab testing
– Time
4
Approaches (1)
![Page 7: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/7.jpg)
• Use Hall Effect Sensor on bypass valve
– Require modification to strainer housing
– Provide actual bypass valve position
• Seal bypass valve
– Method used during lab testing
– Minor modification to strainer housing
– Potential engine flameout
5
Approaches (2)
![Page 8: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/8.jpg)
6
Design
• Measure differential pressure across strainer
– +/- 15psid transducer
– Amplified, 5V output
• Absolute pressure measured on strainer output
– 100psia transducer
– Passive bridge, 100mV output
• Used transducers on hand
![Page 9: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/9.jpg)
412TENG/ENIM P07A017A
7
Layout
Fuel strainer
Absolute
Transducer
Differential
Transducer
strainer Inlet
![Page 10: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/10.jpg)
• Data looked good during acceptance testing
• Later ground testing “noisy”
• Replaced transducers to combat “noise”
Initial Testing
8
![Page 11: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/11.jpg)
• Priority to test
– Plane available for limited time
– Try quick simple fixes
• Access to aircraft
– Other programs on aircraft
• Slow update rate from onboard display
– Hard to quantify noise levels
• Data access
• Fuel system knowledge
Troubleshooting Difficulties
9
![Page 12: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/12.jpg)
• Baseline flight
– New transducer
– Day prior ground test good
First Flight
10
![Page 13: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/13.jpg)
11
What To Do?
• Noise or Data?
• Quick fixes
• Add “dummy” transducer
• Perform autopsy on failed transducer
• Plan for alternatives
![Page 14: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/14.jpg)
• Indications point to fluctuations being data
– Hard transducer failure
– No significant noise on other channels
– Noise levels change with throttle change
– Noise voltage levels
• Absolute transducer-passive, 5mv “noise” seen
• Differential transducer-active, 2v “noise” seen
• Similar EU values between the two
• Lab tests showed no pressure fluctuations
– Flight representative?
Noise or Data?
12
![Page 15: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/15.jpg)
• Replaced transducers
– Passive vs. active
• DAS-Transducer coupling?
– Little or no effect
• Altered grounding of transducer and DAS
– Little or no effect
• Instrument for temperature
– Not a factor, < 50°C
Quick Fixes
13
![Page 16: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/16.jpg)
14
Dummy Transducer
•“Dummy” transducer–Installed on another engine
•Previously instrumented
•Transducer removed
–Not connected to fuel Line
•Also noisy–Coincidence?
–Bad transducer?
–Noisy ground?
–Noise Level
Ground Strap
Thermocouple
412TENG/ENIM P07A017A
![Page 17: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/17.jpg)
15
Transducer Autopsy
• Electronics still good
– Amplified output at -1.0V
– Zero adjustment worked
• Could not be brought to zero
– Not responsive to pressure
• Diaphragm distorted
• Bridge de-bonded & broken
• Causes
• Overpressure
• Severe dynamic fluctuations
Damaged
Areas
Boeing Failure Analysis
5 Nov 2010
![Page 18: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/18.jpg)
16
Cause
• Fuel pump pressure noise
• Cavitation
• Surge
• Valves
– Water Hammer effect
• Affect each side of transducer differently
– Strainer
– Different paths
– Air pockets
![Page 19: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/19.jpg)
17
Fuel system
•Investigate fuel system–Boost pumps
•Low pressure
•Normally fuel comes from boost pumps
–Auxiliary pumps•High pressure
•Test fuel comes from auxiliary pumps
•Significant pressure fluctuations observed
–Switching pumps often caused “noise”•Accompanied by pressure spikes
–100+psi
•Became obvious later
![Page 20: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/20.jpg)
18
New plan
• Add redundancy
– Use two absolute pressure transducers
• Input and output of strainer
• Lower fidelity
• Good results when filtered
• Alternative Instrumentation ruled out
– Hall effect sensor
– Seal bypass valve shut
• Add pressure snubbers
– Porous membrane to dampen transients
– Applied to differential transducer only
![Page 21: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/21.jpg)
19
Layout
Strainer
Differential
Snubber
Strainer
Inlet
Strainer
Outlet
412TENG/ENIM P07A017A
![Page 22: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/22.jpg)
20
Initial Ground Test
![Page 23: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/23.jpg)
21
Later Ground Test
Boost pumps
Gravity
feed Aux pumps
Pressure
spikesPressure
noise
![Page 24: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/24.jpg)
22
First Flight
Boost pumps Aux pumps
Pressure
noise
Drift
and
Bias
![Page 25: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/25.jpg)
23
Last flight
Transducer
Failure
Bias
![Page 26: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/26.jpg)
24
Lessons Learned (1)
• Easy to look for problems with instrumentation
– Spent to much time looking for “noise”
• Coincidence wreaks havoc
– Fuel pumps
– Dummy transducer
• Know the system
– Did not expect high transients or fluctuations
– Did not understand fuel pump differences
![Page 27: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/27.jpg)
25
Lessons Learned (2)
• Look at the data
– Onboard display limited
– Slow turnaround of data
– System characteristics in data
• Fuel systems may exhibit transient pressures
– Valves and pumps
– 100+psia and 30psid transients
• Redundancy is good
– Second absolute transducer saved last flight
• Lab test may not represent flight
– No transients observed in lab
![Page 28: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/28.jpg)
26
Summary
Questions?
![Page 29: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/29.jpg)
27
Back Up Slides
![Page 30: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/30.jpg)
28
Last flight
![Page 31: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/31.jpg)
29
Dummy Noise
Con
nec
ted
Du
mm
y
Note Scale
•Reacting to throttle
•Lower level
•Scale
•Coincidence?
•Bad transducer?
•Noisy ground?
![Page 32: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/32.jpg)
30
Second Ground Test
![Page 33: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/33.jpg)
31
Engine Start Transients
![Page 34: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/34.jpg)
32
Later Ground Test
![Page 35: LESSONS LEARNED WHILE MEASURING FUEL SYSTEM …](https://reader030.fdocuments.us/reader030/viewer/2022012721/61b3d6997d2ad978456d7f11/html5/thumbnails/35.jpg)
33
Flight 2
• Flight test after modification
– Data filtered
– Start of test