Fixed Wing

AIRBUS, A320 211
Service Difficulty Report (SDR) # 20110325003
Wing Wiring Raceway Chaffing

SDR submitted:

The aeroplane arrived with a no-go snag for a left wing tip brake solenoid fault. While maintenance was troubleshooting this defect, it was discovered that several wires were chaffed and burnt on the left wing aft spar raceway just outboard of the #1 engine pylon area.

Other systems affected due to the wiring fault included the #1 engine low pressure fuel valve and the left-hand nav/strobe light.

The wiring was repaired and the aeroplane was made serviceable.

Transport Canada Comments:
European Aviation Safety Agency (EASA) Airworthiness Directive (AD) 2008-0051R1 mandated the incorporation of Airbus Service Bulletin (SBA320-24-1062 which installed insulation for the “S” or inner harness runs.

Optional Service Bulletins A320-92-1049 and A320-92-1052 provides additional insulation for the “M” or outer harness runs.

Transport Canada Civil Aviation (TCCA) is working with European Aviation Safety Agency and Airbus to address this present issue and would like to advise all A320 operators/maintainers of this possible scenario for wire raceway chaffing and available Airbus optional Service Bulletins.

A rear wing spar with chaffed wires


Raceway wiring guides
Rear wing spar
Service Bulletin A320-24-1062

AIRBUS, A330 243
SDR # 20110413014
Wing Panel Missing

SDR submitted:

During a maintenance walk-around, it was discovered that a riveted panel, forward of inboard flap on right wing, was missing.

The aeroplane was repaired as per the Structural Repair Manual (SRM). A new wing panel was installed and the aeroplane was made serviceable.

Transport Canada Comments:
European Aviation Safety Agency Airworthiness Directive 2006-0107 was issued which mandated the one-time inspection of the supporting fasteners and surrounding structure of this discrepant wing panel. Following this and due to the occurrence of more events of this nature, European Aviation Safety Agency Airworthiness Directive 2008-0002 was issued mandating the incorporation of Service Bulletin A330-57-3100, which replaces the existing blind rivets with bolted fasteners.

Transport Canada Civil Aviation (TCCA) would like to advise all A330-200/300 and also applicable 340-300 operators of this possible scenario and available documentation. The accomplishment of the latest Service Bulletin is recommended to be done at the soonest possible opportunity.

A inboard wing root with a missing wing panel


Missing panel area
Inboard wing root
Inboard flap panel

SDR # 20091002006
Hydro Mechanical Unit Fuel Line - Leakage

SDR submitted:

The pilot noticed fuel leaking from the left-hand engine lower cowling during a walk around inspection. Maintenance personnel removed a cowling, cleaned the residual fuel but could not find the source of the fuel leakage. An engine ground run-up was carried out and it was then that a steady fuel spray was emanating from the fuel line that attached from the engine pylon to the Hydro Mechanical Unit (HMU).

The fuel spray was contacting the back of one of the engine igniters, thus the engine was immediately shutdown without incident. The fuel line was replaced but did not show any evidence of damage or wear. No cause for fuel line failure was found.

Transport Canada Comments:
The proper maintenance of fuel lines and fittings is particularly important because of the flammability of fuel. Even a small leak in a confined area (such as the above area, igniters) can soon produce an explosive atmosphere that can be ignited by any kind of spark.

The Service Difficulty Report database contains 3 previous reports of this fuel line being chaffed by the engine cowl latch.

BOEING, 737 800
SDR # 20110316005
Flap Gimbal Bushing Excessive Wear

SDR submitted:

During a scheduled performance of Boeing task cards 27-144-00-01/02 to lubricate the left and right inboard flap outboard ballscrew and gimbals, it was found that the lower gimbal bushing assembly on both the left and the right inboard flaps had migrated out from their respective gimbal seats.

The results of these migrated bushings were excessively worn attachment bolts, which are used to retain the bushings within the gimbal.

The photo to the right shows the abnormal wear of a retaining bolt and gimbal bushing. Both gimbal bushing assemblies and retaining bolts were replaced and the aeroplane was released back to service.

Transport Canada Comments:
Boeing Fleet Team Digest (FTD737NG-FTD-27-03006 defines in detail this possible scenario which is rooted to the application of excessive high grease-gun pressures that can apply undue pressure on the gimbal bushing, forcing it to migrate out and wear into its retaining bolt.

Transport Canada Civil Aviation (TCCA) would like to advise all Boeing 737-600/700/800/BBJ operators and maintainers of this available Boeing Fleet Team Digest and the precaution to take when using high-pressure grease guns.

A worn flap ballscrew bushing and bolt


Worn gimbal bushing
Worn Retaining Bolt

BOEING, 757 200
SDR # 20110215002
Engine Fuel Leak and Imbalance

SDR submitted:

During cruise, the aeroplane experienced a large fuel imbalance due to a fuel leak at the right hand engine. The aeroplane declared an emergency and diverted where upon arrival the right hand tank fuel quantity was 1500 kilogram (kg) less than the left hand tank.

Maintenance personnel found an o-ring that was leaking at the right engine high-pressure fuel pump feed line. The o-ring was replaced and the aeroplane was returned to service.

Six flight legs previous to this event, the right engine high-pressure fuel pump had been replaced where new o-rings were used and leak checks carried out.

Transport Canada Comments:
The reason behind the failure of the o-ring has not been determined but is suspected that possible damage or improper installation of the new o-ring was incurred during the pumps replacement.

Transport Canada Civil Aviation (TCCA) would like to emphasize the importance for maintainers to follow all maintenance manual procedures and necessary handling precautions.

An aircraft engine with a leaking o-ring at the high-pressure fuel pump feed line


Leak occurred here
Fuel Control Unit Assembly
High Pressure Fuel Pump

BOEING, 767 300
SDR # 20110607014
Relay Failure

SDR submitted:

During flight, several system failure messages were posted where maintenance troubleshot the fault to a failing relay.

It was noted that several of the connecting post studs were loose within the relay body receptacles, breaking the posts electrical continuity capability.

The relay was replaced and the aeroplane was made serviceable.

Transport Canada Comments:
Transport Canada Civil Aviation (TCCA) would like to emphasize to all aeroplane maintainers of this relay’s possible failure scenario.

A relay assembly and posts


Connecting post receptacles at the relay
Dislodged connecting post studs

SDR # 20110526004
Insufficient Hydraulic Line Support

SDR submitted:

During flight at cruise and inbound to a maintenance base, the #1 hydraulic quantity went to zero followed by the pressure going to zero and associated system low pressure caution messages.

Upon maintenance investigation, it was found that the #1 hydraulic pressure line in the aft equipment bay was chaffed through, causing the complete loss of the fluid. The chaffing was a result of the hydraulic line jam-nuts at the top of the hydraulic support shelf coming loose, allowing significant movement and vibration.

The hydraulic support shelf was severely worn along with several support bracket fairleads downstream the line.

The hydraulic support shelf was repaired, the hydraulic line and fairlead inserts for the support brackets were replaced and the aircraft was made serviceable.

Transport Canada Comments:
The correct support of all hydraulic lines is essential for the continued operation of aircraft hydraulic systems.

This scenario demonstrates that the worn fairlead inserts were an indicator of a more significant failure else-where in the system.

Transport Canada Civil Aviation (TCCA) would like to advise all operators and maintainers of this possible scenario that may lead to a complete hydraulic system failure.

Failed hydraulic line support clamp fairlead inserts found severely worn


Failed hydraulic line support clamp fairlead inserts found severely worn


A hydraulic support shelf found severely worn with a failed hydraulic line


Failed hydraulic line
Hydraulic support shelf found severely worn

BOMBARDIER, CL600 2D24 (RJ900)
SDR # 20110310004
Main Landing Gear Wheel Rim Cracks

SDR submitted:

During a standard service check it was found that several rim spokes of the main landing gear wheel number 2 (left-hand inboard) were found cracked.

The wheel assembly was replaced as per the aircraft maintenance manual and the aeroplane was made serviceable.

Transport Canada Comments:
The close visual inspection of all wheel assembly landing gear items is an essential task to accomplish for all pre-departure walk-around and service checks. 

A main landing gear wheel rim with cracks


9 of the 18 wheel spokes are broken

DHC 8 301
SDR # 20110524008
Frayed Aileron Cable

SDR submitted:

During inspection, the right-hand aileron cable was found to be significantly frayed and beginning to unravel. The area of the failing cable (Wing Station (WS) 181) is located in a cable block on the aft spar where aluminum guide rollers part number FL4C6-2. This particular area of the cable is almost impossible to see when the gust lock is engaged and/or the aileron is in a neutral position because of the cable block.

Transport Canada Comments:
The SDR database reveals several previous reports of this nature in this general area.

A reminder for personnel that during flight control cable inspection that the entire cable run must be inspected to detect these types of failures.

A frayed right-hand aileron cable

SDR # 20110121001
Pylon Fairing Missing Attaching Hardware

SDR submitted:

During a heavy maintenance “N1” check visit on the aeroplane, a left-hand pylon inspection found that the aft lower fixed fairing assembly was missing several items of attaching hardware. Within the pylon fixed fairing, both forward quick release pins had fallen out, as had one of four mid-point attach bolts. The missing hardware was found in the bottom of the fairing. The right-hand pylon was found to have the two forward quick release pins and three of four mid-point bolts also missing. The pins and two of the three missing bolts were found inside the fairing. In both cases, the four aft mounting bolts were found installed and properly torqued.

Transport Canada Comments:
This operator obtained the required engineering Original Equipment Manufacturer (OEM) and company approval to install a single dash length longer attaching bolt and reinstalled new quick release “pip” pins.

Further investigations of the operators E170 fleet and Embraer, the Original Equipment Manufacturer (OEM), revealed that this was a fleet wide affected issue upon which a Service Newsletter (SNL170-54-0001 was released.

Transport Canada Civil Aviation (TCCA) would like to advise all Embraer 170 operators of this Service Newsletter (SNL) and its intent to replace the discrepant hardware to increase its bolt length, final torque and to introduce a new countersunk washer.

A left engine pylon with a missing fastener

SDR # 20110526002
Engine Driven Pump Hydraulic T-Fitting Cracks

SDR submitted:

During a heavy maintenance “C-check” visit, maintenance found the #1 & #2 pylon engine driven hydraulic pump pressure line T-fittings cracked and with evidence of hydraulic fluid leakage.

Both pressure line T-fittings were replaced to correct the fault.

Transport Canada Comments:
Transport Canada Civil Aviation (TCCA) would like to advise all Embraer 190 operators and maintainers of this possible scenario.

An engine driven pump hydraulic line fitting with a crack and evidence of leakage


Crack and evidence of leakage

SDR # 20110614008
Metroliner Bleed Duct Failure

SDR submitted:

The pressurization was snagged as inoperative by the flight crew. During maintenance trouble-shooting it was noted that the engine bleed pressure would fluctuate uncontrollably and when turned to “high” only function for approximately 30 seconds. Then the eyeball vents would drop off with almost no air-flow output available.

During subsequent inspection of the right-hand wing bleed air duct plumbing, maintenance found the tube assembly from the right-hand modulating valve to right-hand cooling turbine cracked in half. The tube was replaced, ground run accomplished and the aircraft returned to service.

Transport Canada Comments:
Transport Canada Civil Aviation (TCCA) would like to advise all Fairchild SA227 operators and maintainers of this possible bleed duct failure scenario.

A failed bleed air duct

SDR # 20110608005
Cabin Temperature Control Valve Failure

SDR submitted:

During cruise, the cabin temperature was uncontrollable, leaving the cabin in a very warm and uncomfortable condition.

Upon maintenance investigation, the cabin temperature control valve plunger body was found cracked off, shearing the plastic link arm which opens and closes the butterfly valve and rendering it uncontrollable.

The valve was replaced and the aircraft made serviceable.

Transport Canada Comments:
Transport Canada Civil Aviation (TCCA) would like to advise all Learjet 60 operators of this possible scenario concerning the integrity of the cabin temperature control valve.

A broken cabin temperature control valve


Broken valve body and parts

SDR # 20110429007
Elevator Trim Servo Running Backwards

SDR submitted:

During annual inspection three autopilot servos and one elevator trim servo were removed and sent for 900 hour test/re-certification. The returned servos were re-installed per Maintenance Manual (MM). The Aircraft Maintenance Engineer (AME) ensured trim tab and elevator trim gauge agreed throughout the range of movement (indicated nose up corresponded with trim tab down and vice versa). Manual trim moved in the correct direction agreeing with the gauge and trim tab. What the AME didn’t notice was the direction arrows on the elevator trim switch on the control column during these checks. When pushed “up” on the electric trim switch, the system moved towards nose up rather than the correct direction of nose down. The autopilot and trim system were dual inspected and the aeroplane was sent for a test flight. During the flight, it was discovered the trim system was operating backwards and the autopilot would not hold altitude. The pilots used manual trim (which was working normally) to return to base. The trim servo was suspected and a serviceable unit was installed. The electric trim system functioned normally with the serviceable unit installed. The system was dual inspected again, sent for test flight and found airworthy.

It appears the servo was assembled/rewired incorrectly by the overhaul facility although the original work order does not show rewiring. The suspect servo was returned to the overhaul facility.

Transport Canada Comments:
It is important to fully understand the operation of a system being worked on. It must be tested and confirmed in all modes once the work is completed.

SDR # 20110509004
Incorrectly Installed Fuel Line

SDR submitted:

During a scheduled inspection on a SAAB 340A, maintenance found a fuel line twisted on the left-hand engine lower nacelle.

The line was removed, replaced and the aeroplane was made serviceable.

Transport Canada Comments:
Correct fuel line installation is essential to support the full range of engine operation.

When installing fuel lines of any type and in particular aluminum, proper aircraft maintenance manual torque values must be followed.

A twisted fuel line

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