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FAA wire incidents report: March 2009

Conference & Report

The following are the wire incidents reported in the FAA’s March 2009 Circular 43-16A – Alert Number 368.

Incident # 1

  • Aircraft Make: Cessna
  • Aircraft Model: A150K
  • Part Name: Air Intake
  • Part Condition: Water Block

From the perspective of FAA Wire Incidents, a mechanic provides this excellent analysis of his customer’s aircraft problems:

“The owner took off for some pattern work. (Since…) the weather had been cold and clear for several days he thought it perfect for touch-&-goes. On the downwind leg he began his normal landing check list—including checking the carburetor heat. After pulling (this heat control) ‘ON’ the engine died. He turned off carburetor heat and the engine restarted on its own without pilot input. He continued the pattern and gradually reapplied carburetor heat on base and final. On short final the engine died and the pilot glided to a safe touchdown just beyond the end of the runway. He was able to restart the engine and taxi back to parking without incident.

We looked at the engine…and found the Scat hose (model 150 & A150; 1970-77 parts manual; figure 56; sheet 2; item 29) coming from the front baffle down to the front of the exhaust shroud had filled with water. The installed hose is in the form of a ‘J’, and the bottom of this ‘J’ was full of water and ice.

In our damp climate we have noticed this before and usually ensure each scat hose has a drain hole in any low areas. Somehow this (particular) aircraft had been missed. We have found water and ice in similar installations on Cessna 150 and 172 series aircraft. Because of their location, the air intake scoops in the front baffle funnel rain water into the SCAT hose, (filling) the forward hose. Sometimes the water overflows the front hose and flows along the lower inside of the heater shroud, (attempting…) to also fill the carburetor heat box-to-right-shroud Scat hose (model 150 & A150; 1970-77 parts manual; figure 56; sheet 2; item 19). This results in the engine receiving a large slug of water or ice when the carburetor heat is applied. Whether the water is in a liquid or solid form depends on the duration of the flight and whether the heat of the operating engine has melted any ice that may have formed during periods of inactivity.

This is a dangerous condition during weather conditions when carburetor icing is a possibility. The pilot would (be prompted) to turn on the carburetor heat to clear any icing that may have formed through the normal induction system. Instead of getting warm air as expected, the engine would suddenly receive a small to very large burst of water or ice into the induction system that could instantly refreeze, plugging the induction system entirely. So far, we have not seen this happen.

We normally encounter this problem in warmer months when we receive more rain. Under those conditions the pilots notice a rough running engine when carburetor heat is applied, and turn the heat off before the water is fully removed—or (they opt) to continue with the heat (applied and the resulting engine roughness…)—until the water clears from the hose.

One way to check for this problem on any aircraft is to (examine) the scat tube reinforcing wire for rust in the lower areas. The occasional water build-up will cause these reinforcing wires to have more pronounced rust on the lower portions where water would sit on the wire wraps. Any aircraft showing abnormal wire deterioration in those areas should consider installing drain holes.”

Incident # 2

  • Aircraft Make: Piper
  • Aircraft Model: PA31-350
  • Part Name: Fuel Pump
  • Part Condition: Electrical Failure

An unidentified mechanic relates the following:

(The aircraft was departing the field…) when he reported he lost substantial power to the left engine just after take off, and that the left low pressure fuel boost pump light on the aircraft annunciator panel illuminated. He (effected a safe landing at an airport) and called for aircraft maintenance. The aircraft technician on location could not find any problems with the engine during run-up other than the electric, low pressure fuel boost pump not supplying rated pressure. (Note: the electric, in-line low pressure boost pump is intended for flight above 15,000 feet MSL and can be deferred, as per our Part 91 MEL (minimum equipment list). The aircraft (initiated its take-off roll for departure…) when the left engine again lost power at (approximately) 40 knots airspeed. (Subsequent) trouble shooting of the engine fuel pump and fuel nozzles revealed no problems. The in-line low pressure fuel pump was removed (revealing) the bypass valve assembly in the pump had dislodged from the pump body and acted as a fuel (flow) restriction to the emergency electric fuel pump. We have been operating the Piper Navajo Chieftain aircraft for 20 years and have never seen this happen until now.”

Incident Reports
(Parker Hannifin Pump, P/N 2B6-64. Time since overhaul: 2,098.4 hours. The FAA Service Difficulty Reporting System (SDRS) reflects 11 entries for this part number.)

Incident # 3

  • Aircraft Make: Piper
  • Aircraft Model: PA32R-301T
  • Part Name: Main Gear Down-Lock Switch
  • Part Condition: Failing
(The following combines five reports on four PA32 aircraft—all from the same mechanic.)

This aircraft’s “…main gear down lock switch wires pull tight on the strut during retraction, pulling wire strands apart to the breaking point. The silicone type wire coating tends to hold the wire ends together, creating intermitent contact. (This assembly) needs better wire and routing.”

Incident # 4

  • Aircraft Make:
  • Aircraft Model:
  • Part Name: Wire Harness
  • Part Condition: Frayed
  • Part Location: NLG
  • Nose Landing Gear electrical harness – outer fabric shield – frayed. Harness replaced.

Incident # 5

  • Aircraft Make: Airbus
  • Aircraft Model: A310304
  • Part Name: Wire
  • Part Condition: Arced
  • Part Location: Fusleage
  • Mechanic noticed flash of light from left wheel well. Found power supply wire bundle under support clamp on aft wall of left wheel well. System was deactivated and put on MEL 29-2. Harness will be replaced at the next available downtime and harness will be routed to engineering for evaluation. (TC NR 20090112009)

Incident # 6

  • Aircraft Make: AMD
  • Aircraft Model: Falcon
  • Part Name: Power Supply
  • Part Condition: Defective
  • Part Location: Cabin
  • Wrong parts inside strobe power supply PN 39-44-31: C3, C6, C9 (capacitors), Q5 (transistor) and wire color. No serial number on unit; serial number on customer paperwork is 1024088873.

Incident # 7

  • Aircraft Make: Beech
  • Aircraft Model: B200
  • Part Name: Wire
  • Part Condition: Broken
  • Part Location: Reset Switch
  • Air conditioning reset switch located in the wheel well found broken. Upon examination of switch it was noted factory installed heat shrink tubing was not properly installed thereby allowing it to migrate away from the switch connector. This in turn caused exposed electrical wiring which given the right conditions could cause electrical arcing and possibly smoke and/or fire. This defect was discovered as a result of normal inspection however review of previous discrepancies showed this was not the first occurrence of failure for this switch installation. Stores inventory was checked and found spares had the same flaw. Before installing new switch, additional heat shrink tubing was installed illuminating the possibility of further occurrence. (TC NR 20090126005)

Incident # 8

  • Aircraft Make: Armgen
  • Aircraft Model: AA5B
  • Part Name: Wire
  • Part Condition: Burned
  • Part Location: Beacon
  • During annual inspection flashing beacon was found to be not working. Upon tracing the wiring a burned wire was discovered at junction jp-1-2 below instrument panel aft of center console. This was the second time that burned wires were found at this location on this type of aircraft and the third time that burned wires were found at a connector in the flashing beacon circuit.

Incident # 9

  • Aircraft Make: Boeing
  • Aircraft Model: 777*
  • Part Name: Wire Harness
  • Part Condition: Worn
  • Part Location:NR 2 Engine
  • On NR 2 engine found harness W729 damaged behind fan cowl at 6 o’clock position. The damage was caused by the harness rubbing on each other. The harness was changed and repositioned (TC NR 20090115001).

Incident # 10

  • Aircraft Make: Boeing
  • Aircraft Model: 777*
  • Part Name: Wire Harness
  • Part Condition: Worn
  • Part Location: NR 1 Engine
  • On nr1 engine found harness W721 damaged behind fan cowl at 8 o’clock position. The harness damage was caused by the rub between 2 electrical harnesses W721 harness replaced and repositioned IAW B-777 AMM task 70-00-01-400-806-H-01. (TC NR 20090115002)

Incident # 11

  • Aircraft Make: Bombardier
  • Aircraft Model: BD1001A10
  • Part Name: Generator
  • Part Condition: Fire
  • Part Location: APU
  • After APU start at fl100 just before APU gen on line APU fire CAS message posted. Pilots arm APU bottle message disappeared. Pilots shutdown APU and land a/c safely. In aft equipment bay pilots noted an odor of burned wire. After inspection of APU generator found generator on fire. Fire went out via cooling duct to educator sensing element of APU fire detection system. APU door showing signs of fire.

Incident # 12

  • Aircraft Make: Cessna
  • Aircraft Model: 182P
  • Part Name: Connector
  • Part Condition: Burned
  • Part Location: Light Switch
  • Pilot reported smoke in cockpit after takeoff and returned to the airport making an uneventful landing. Maintenance inspected the aircraft and found a loose connection at the landing light switch with burned wiring insulation. Installed new wiring and connector as needed and ops checked good. Push-on type of wiring connectors need to be checked closely for security during scheduled maintenance.

Incident # 13

  • Aircraft Make: Cessna
  • Aircraft Model: 208
  • Part Name: Wire
  • Part Condition: Burned
  • Part Location: Prop Deice
  • During inspection it was found that the electrical connector and approx 3 inch of wire forward of the vanister. In the prop de-ice CCT was burned and the wire had become separated from the Vaniston leaving the prop de-ice system in-active. Flight crew was unaware of any inoperative systems. Wiring was repaired and connector replaced, system function tested normal. Submitter suspects/connector wire had worked loose over time causing arcing/burning with wire finally fell off. (TC NR 20081222005)

Incident # 14

  • Aircraft Make: Cessna
  • Aircraft Model: 208B
  • Part Name: Wire
  • Part Condition: Chafed
  • Part Location: Tail Beacon
  • The pilot reported his tail beacon inoperative. Maintenance techs troubleshot the wiring and found that the wiring bundle that contains the power wire for the tail beacon where it routes over the glove box had chafed on the glove box. The chafing caused the wire to burn through the glove box.

Incident # 15

  • Aircraft Make: Canadair
  • Aircraft Model: CL6002B19
  • Part Name: Sensor
  • Part Condition:Malfunctioned
  • Part Location: Brake Position
  • Flap fail on descent when flaps set to 45 deg. Oat was 3 deg. Crew indicated that flaps failed appeared after flaps had reached 45 deg in both event. Action plan 156-jan-4-09-plan 2 c/out, left BPSU replaced IAW aircraft mm 27-51-10-830-801, left BPSU wiring checked no fault found.

Incident # 16

  • Aircraft Make: Canadair
  • Aircraft Model: CL6002B19
  • Part Name: Actuator
  • Part Condition: Malfunctioned
  • Part Location: TE Flap
  • On final approach, crew selected flaps to 45 degrees. Flaps failed at 38 degree. Forecast oat at altitude was -60C. Oat at landing was – 2 degree. No emergency was declared and flight landed safely. Aircraft had been in flight for about 2 hours. After landing crew positioned flap lever to 0° but there was no movement of flaps. Maintenance received the following fault codes from the FECU: 1. Jam. 2. Left BPSU. 3. Wiring left BPSU. An action plan was developed for lubrication and freeze checks of the left actuators. NR 3 and NR 4 left actuators failed freeze check. Maximum breakout torque is 15 lb in, reading for left NR 3 was 27 lb in and left NR 4 was off the scale. Per these findings a second action plan has been issued to replace all 8 flap actuators. Removed actuators to be sent to vendor as a ship set for further investigation. It was noted that this set of actuators had only recently been installed (TSR 98 hours) and all were the upgraded version of actuator. (TC NR 20090107003)

Incident # 17

  • Aircraft Make: Canadair
  • Aircraft Model: CL6002B19
  • Part Name: BPSU
  • Part Condition: Failed
  • Part Location: TE Flaps
  • During final segment of climb, the flight crew received a flap fail message on EICAS. The flaps were at zero and were indicating zero at the time. The QRH was followed and the aircraft landed without incident. Maintenance checked FECU for fault codes and found codes for right BPSU, FECU and wiring for right BPSU. The system was reset, the flaps were ops checked and no further defects noted. Aircraft returned to service. In cruise flight, the flight crew received a flap fail msg. The flight control synoptic page indicated the flaps were outlined in yellow showing zero degrees of extension. The aircraft landed back without incident. Maintenance pulled FECU codes (see attached) which indicated right BPSU or wiring. The right BPSU was replaced, the flap system was ops checked and no further defects noted. Aircraft returned to service.

Incident # 18

  • Aircraft Make: Bombardier
  • Aircraft Model: DHC8102
  • Part Name: Generator
  • Part Condition: Malfunctioned
  • Part Location: NR 1 AC
  • Shortly after take off, the flight crew received “NR 1 AC gen” and “NR 2 AC gen” caution lights. Systems were reset and NR 2 AC generator returned on line. Decision was made to return and the aircraft landed without further incident. The NR 1 AC generator was replaced and the phase A and C wires located under the right flap between the nacelle and the fuselage were repaired. Both wires were shorted due to chafing.

Incident # 19

  • Aircraft Make: Embraer
  • Aircraft Model: EMB145LR
  • Part Name: Wire
  • Part Condition: Chafed
  • Part Location: RT Nacelle
  • IAH – flight 2749, the crew reported the NR 2 engine fire detection system failed in flight. The aircraft returned to IAH where it landed without incident. Maintenance inspected the aircraft, and repaired wires W407-0011-20 & W407-0012-20 near connector P0914, ops checked with no defects, and the aircraft was approved for return to service.

Incident # 20

  • Aircraft Make: Swearingen
  • Aircraft Model: SA226TC
  • Part Name: Solenoid Valve
  • Part Condition: Mismanufactured
  • Maintenance replaced the bleed air valve solenoid for a flight snag. The PN320250-4-1 solenoid is located in the right WW of the aircraft. After replacement of the valve the AME did not notice that the electrical connection for the cannon connector on the valve was oriented differently than the previous valve which was removed. The wire harness and connector was able to be hooked up in this different configuration. Normally with the valve installed, looking forward the connector in at a 2 o’clock position. This replacement valve has the connector located at approximately the 6 o’clock position. The aircraft was dispatched and after takeoff the crew retracted the gear and noticed the right main landing gear remained in transit rather than locking in the up position. The gear was recycled with no success. The crew elected to return to the airport and landed without further problems. Maintenance immediately noticed that the nr 3 tire had markings on it from contacting the bleed air solenoid connector when it was attempted to be retracted. This damaged the valve bracket and the connector, the valve was not damaged. Maintenance realigned the cannon connector and reinstalled the valve with a new bracket, performed a gear swing and released the aircraft.
Michael Traskos

This article was written by the Lectromec technical team. Aircraft wiring is our passion and we strive to make a contribution to the field by sharing our expertise through blogs, podcasts, and videos. We hope you find this information helpful. We also encourage you to submit comments and spur discussions.