Fixed Wing

Gear By-pass Valve Failure

AIRBUS, A319-114
SERVICE DIFFICULTY REPORT
(SDR) # 20110909012

SDR submitted:

The left main landing gear (MLG) door would not close following an aeroplane scheduled maintenance event. The MLG door by-pass valve was found to have two sheared bolt heads, causing the failure. The valve was replaced and all functional tests passed, making the aeroplane serviceable.

Main landing gear door by-pass valve
* Sheared bolt heads still being held by the lockwire

Transport Canada Comments:

This MLG by-pass valve is located within each MLG wheelwell just above the MLG door uplocks which can be seen on a walk-around.

Transport Canada Civil Aviation (TCCA) would like to advise all Airbus 318, 319 and 320 operators of the possible failure of this valve.

Failure to Reset the Fuse Pin

BAE-UK, 3112
SDR # 20110627022

SDR submitted:

The aeroplane arrived with a nose landing gear (NLG) steering snag. The NLG was changed with a serviceable gear assembly. The aeroplane took off the next morning on a scheduled departure, but it returned with a "landing gear failed to retract" snag. Upon investigation it was determined that the fuse pin for the emergency landing gear hydraulic system was not reset during its recent replacement.

The fuse pin was reset and the aeroplane was made serviceable.

Transport Canada Comments:

An internal investigation was conducted to look into why maintenance did not reset the fuse pin at the emergency selector valve prior to making the aeroplane serviceable.

Upon review of the Aircraft Maintenance Manual (AMM) it was discovered that the complete NLG replacement procedure referenced 10 separate AMM tasks which added to the complexity of the job. It was noted that the AMM does make mention of resetting the fuse pin, but this essential procedure is difficult and cumbersome to locate within the numerous AMM tasks.

Through the efforts of the operator involved, Transport Canada Civil Aviation and BAE engineering, revision 28 of the AMM was released in September 2011 which has introduced the following note within 5 separate applicable AMM tasks:

"Following maintenance actions, ensure that the emergency selector valve and release valve is reset (reference chapter 29-20-00, page block 201").

Flap Actuator Failure

BOEING, 727-27C
SDR # 20110817010

SDR submitted:

Upon departure, the No 2 slat failed to retract. The flaps were re-cycled and shortly after, the hydraulic "A" system quantity went to zero. An emergency was declared, applicable checklists were run and the crew performed a non-eventful landing.

Due to the loss of hydraulic system "A", the aeroplane had to be towed off the runway. Upon investigation, maintenance found that the No 2 slat actuator inner sleeve sheared causing the hydraulic fluid loss.

The Noo 2 slat actuator along with both engine filters and system "A" pumps were replaced. The hydraulic system was serviced and all flight control functional checks were carried out as per the Aircraft Maintenance Manual with no noted leaks or faults, making the aeroplane serviceable.


* B-nut elbow retract port
** Sheared inner hydraulic sleeve

Transport Canada Comments:

Feedback from the operator's shop tear-down report gave no indication of the root cause of the failure and there was no indication noted by maintenance prior to the event.

It is suspected that the B-nut elbow fitting may have seized within the inner sleeve, which in turn created undue stresses through the swivel movement of the actuator during slat operation.

Leading Edge Skin Failure

BOEING, 767-375
SDR # 20110823004

SDR submitted:

During a standard walk-around, maintenance found that a section of the No 11 leading edge slat top skin measuring 33 cm (13 in.) wide by 16.5 cm (6.5 in.) fore and aft was torn away with pulled rivets on the bottom.

The aeroplane was taken out of service and a temporary repair was carried-out.

#11 Slat panel skin failure
#11 Slat panel skin failure

Transport Canada Comments:

Another example of the importance of the close attention required when performing a walk-around inspection.

Tire Failure on Takeoff

BOEING, 737-7CT
SDR # 20110822012

SDR submitted:

During takeoff, the crew reported feeling a vibration as though a tire had blown. This was subsequently confirmed by the air traffic controller as pieces of rubber were found on the runway. The aeroplane was diverted to another airport where maintenance confirmed that the right-hand outboard tire had failed. The disintegrating tire also caused structural damage to the aeroplane.

The tire was replaced and all necessary repairs were done on the aeroplane, making it serviceable.

Shredded B737 main tire assembly
Shredded B737 main tire assembly

Transport Canada Comments:

A request from the operator for a detailed tear-down report was made to the wheel overhaul vendor where it was determined that the most probable cause of the tire failure was "over-deflection" or an under-serviced condition.

For maintenance engineers, special attention to correct tire pressure is essential for the continued safe operation of all aeroplanes.

Bird Strike Incurred Damage

BOMBARDIER, CL600 2B19 (RJ100)
SDR # 20110818004

SDR submitted:

The flight crew reported a possible bird strike on rotation in the area of the nose landing gear (NLG). Subsequent inspection revealed damage to the left-hand lower corner of the NLG aft door (gear-down configuration). The NLG aft door was replaced and the aeroplane was returned to service.

Incurred bird-strike damage on the aft nose landing gear door
Incurred bird-strike damage on the aft nose landing gear door

Transport Canada Comments:

The bird strike damage as defined in this article had the potential to cause a serious incident on this aeroplane if it had gone undetected by the flight crew and ground personnel.

In this case, the damage was obvious and easily found due to its location, but in other scenarios and with other types of aircraft, the ability to detect exterior damage caused by a bird strike, is at times more difficult and less apparent.

Through the seasonal migration of various birds and their constant summer activity, the potential of a bird strike is a year-round concern.

Transport Canada Civil Aviation (TCCA) would like to advise all owners, operators and maintainers of the importance of being diligent with our standard walk-around inspections for potential bird strike damage.

Lightning Strike Damage Incurred

BOMBARDIER, CL600 2B19 (RJ100)
SDR # 20110822011

SDR submitted:

The crew reported a lightning strike on the left wing during descent. Initial inspection revealed some damage to the lower left winglet static discharger. The aeroplane was removed from service and inspected in accordance with the Aircraft Maintenance Manual (AMM) Chapter 05-51-05.

An inspection revealed minor damage to the right elevator (entry point) and damage to the left winglet lower fairing composite, static discharger and base (exit point). The left winglet lower fairing part number 600-10388-1 was replaced and the aeroplane was released for service.

Left winglet lower static wick base with lightning strike damage
Left winglet lower static wick base with lightning strike damage

Transport Canada Comments:

Lightning strike damage can vary from minor damage, as seen in this article, to major damage, where significant structural damage can be incurred.

As defined in this event, lightning strikes have entry and exit points. Sometimes there are several exit points from a single entry point.

Transport Canada Civil Aviation (TCCA) would like to advise all owners, operators and maintainers of the importance of investigating all reported lightning strikes; all parts of the aeroplane exterior need to be inspected prior to next flight.

Auxiliary Power Unit Oil Leak Causing a Rejected Takeoff

BOMBARDIER, CL600 2B19 (RJ100)
SDR # 20110921002

SDR submitted:

On taxi out, the aeroplane lost the function of its auxiliary power unit (APU) and returned to the gate. Upon investigation, maintenance discovered that a stud was missing at an oil line attachment within its enclosure, causing the auto shutdown of the APU.

The APU was put on the minimum equipment list (MEL) and dispatched; the aeroplane's next takeoff was aborted due to smoke in the cabin.

The aeroplane returned to the gate and maintenance found oil residue forward of the isolation valve within the bleed air duct.

The oil residue was removed and the aeroplane was released back to service.

Auxiliary power unit oil line missing attachment stud
Auxiliary power unit oil line missing attachment stud

Transport Canada Comments:

From the oil leak within the APU enclosure, oil was ingested through the air intake of the APU, contaminating the aeroplane's bleed air ducts.

Transport Canada Civil Aviation (TCCA) is advising all maintainers of the importance of ensuring all residual contaminants are removed from all possible affected systems when addressing any form of fluid leakage.

Aging Wiring and Incurred Damage

BOMBARDIER, CL600 2B19 (RJ100)
SDR # 20110826002

SDR submitted:

During testing of the flap electrical system for an unrelated reason, maintenance found an open circuit between the No 1 flap power drive unit (PDU) thermistor and the flap electronic control Unit (FECU). Further investigation revealed that electrical wire 1CE46A22wht of the FECU was broken between connector 1J6CE pin f and connector P4CE-a pin 15; reference wiring diagram 27-51-00 sheet 4 and 5.

Wire 1CE46A22blu was also found with substantial damage. The wires were part of a bundle located behind the FECU, rack as seen in the attached picture.

The damaged wires were likely the result of a plastic tie-wrap that was adjusted too tight. The wires were repaired, the system tested and the aeroplane was released for service.

Flap electronic control unit rack
* Area of wiring damage found

Transport Canada Comments:

The thermistor wiring circuit provides overheat protection for the PDU electrical motor. With the loss of this thermal protection due to the wiring fault noted, indication of an overheat condition would not trigger any caution or status messages to the flight crew, potentially affecting the safety of the aeroplane.

It is suspected that the tie-wrap that caused the wiring failure was factory installed and was adjusted too tight.

Due to the concerns regarding the expected wear-and-tear for aging aeroplanes, Transport Canada Civil Aviation (TCCA) would like to emphasize the importance of this type of wiring failure to all maintainers.

Integral Wing Structure Cracks

BOMBARDIER, CL600 2B19 (RJ100)
SDR # 20110824001

SDR submitted:

While carrying out a scheduled inspection of the wing fuel tanks, the aircraft maintenance engineer (AME) noticed cracks on the lower cap angles forward of the wing rib at wing station 29.42 in both the centre and right fuel tanks.

The cap angles were removed and replaced with newly fabricated angles in accordance with Bombardier SRM Chapter 51-10-06 and the aeroplane was made serviceable.

Crack Location
* Crack Location

Transport Canada Comments:

The Instructions for Continued Airworthiness (ICA) are created to direct specific maintenance inspections towards the expected structural and system failures of the aeroplane through its calculated service time.

A Bombardier inspection task-card called for the inspection of the area which included the discrepant cap angles.

Lightning Strike Damage

DHC 8 102
SDR # 20110908007

SDR submitted:

While descending through 5000 feet altitude, the aeroplane experienced a lightning strike.

Ground investigation revealed burnt exit holes through the top and bottom skin of the right hand elevator as well as an exit hole through the elevator tab trailing edge. Further examination revealed lightning strike damage to the elevator spring tab assembly, which required replacement.

Lightning strike exit hole on bottom of R/H elevator assembly
Lightning strike exit hole on bottom of R/H elevator assembly

Transport Canada Comments:

Static charges build up on aeroplanes during flight and tend to accumulate near sharp edges on the trailing edges of wings and tail surfaces. Therefore, static wicks are installed in these areas to provide a conductive path for the excess electrons (static build-up) to go back into the atmosphere. Static wicks also dissipate excess static charges that can interfere with aeroplane navigation and communication systems.

These same static wicks also dissipate lightning strike charges back into the atmosphere. It is essential that static wicks be in good condition.

Rudder Hinge Attaching Bolt Failure

EMBRAER, EMB-145LR
SDR # 20110830020

SDR submitted:

On a C1 check, while performing a detailed visual inspection of the rudder hinges in accordance with task E27-21-02-220-001, the inspector found the bottom hinge attachment bolt on rudder-II (aft) missing. After a quick investigation, he found the bolt severed in two with the remaining attaching hardware inside the rudder.

The bolt, adjoining bushings and hardware were replaced and the aeroplane was made serviceable.

Failed rudder bolt and excessively worn bushing
Failed rudder bolt and excessively worn bushing
Hinge hardware found in the bottom of the rudder
Hinge hardware found in the bottom of the rudder

Transport Canada Comments:

Transport Canada Civil Aviation (TCCA) is working with the Federal Aviation Administration (FAA), because this aeroplane is American-registered-and the responsible Brazilian Authorities, Agência Nacional de Aviação Civil (ANAC) to address this issue.

TCCA would like to advise all owners, operators and maintainers of this possible scenario.

Flight Deck Smoke due to Shorting Circuit Breakers

FAIRCHILD, SA227DC
SDR # 20110829016

SDR submitted:

The inner-wire metal support of the skeet hose broke free and came into contact with the "hot" terminal ends of several right-hand essential bus circuit breakers, causing smoke in the cockpit when the aeroplane was landing.

The aeroplane landed without incident where maintenance replaced the hose and damaged circuit breakers.

Skeet hose and circuit breaker damage
* Skeet hose and circuit breaker damage

Transport Canada Comments:

The correct support and integrity of all aeroplane ducting, wiring and anything else near "hot" terminal ends behind circuit breaker panels is essential to prevent occurrences such as the one seen above.

As confirmed with the manufacturer, part numbers 32-84301-101 or 32-84301-107 hose assembly as seen in the Illustrated Parts Catalog (IPC) are to be used in this area only; these have a protective shrink tube sleeve to provide additional electrical insulation. Service bulletins CCS7-21-001, 227-21-009 and 226-21-021 have been issued to address this issue Service Bulletins CCS7-21-001, 227-21-009 and 226-21-021 have been issued to address this issue.

Centering Arm Unapproved Part

FAIRCHILD, SA227AC
SDR # 20110829011

SDR submitted:

The nose wheel centering mechanism contains a centering arm with a bearing that rotates in a cam to center the wheels. The bearing is retained in the arm by a pin.

This particular arm, which was removed from the aeroplane, was not drilled to accept the pin. The bearing started to back out of the arm which caused the bearing to bind up in the cam; this was caught on a daily inspection done by the technician.

The sub-standard part was removed and replaced with a new centering arm that was correctly built.

Removed discrepant centering arm with no retaining screw
* Replacement part with required retaining screw

Transport Canada Comments:

When replacing aeroplane parts or components, it is essential to perform a complete general visual inspection of the part prior to installation.

Sub-standard or suspected unapproved parts (SUP) are to be reported as an Service Difficulty Report (SDR), defined in Standard 571.13 within an information note.

Hydraulic Fluid Loss

HAWKER SIDDELEY-UK, HS-748 2A
SDR # 20110803022

SDR submitted:

Upon the selection to extend the landing gear in preparation for landing, the crew noticed a pressure drop in the hydraulic system. After a normal landing, when the aeroplane was parked on the ramp, hydraulic fluid was noticed under the right hand nacelle area. Maintenance personnel found the hydraulic cut-out valve had a cracked housing. The valve was replaced and the aeroplane was returned to service.

Further inspection found that the failed cut-out valve was a pre-mod 2843. This optional mod introduces a new and more robust hydraulic cut-out valve (part number AIR48920). The post-mod cut-out valve was installed in the place of the cracked pre-mod valve.

Cracked hydraulic cut-out valve
Cracked hydraulic cut-out valve

Transport Canada Comments:

Transport Canada Civil Aviation (TCCA) would like to advise all HS748 owners and operators of this available post-mod cut-out valve.

Cracked Nose Gear Actuator Link

WIPAIRE, AMPHIBIOUS FLOAT ASSEMBLY
SDR # 20110823006

SDR submitted:

During maintenance gear swing, on retraction cycle, the piston rod link broke. Upon inspection, intergranular corrosion was found at the fracture point. The piston rod link was replaced with a serviceable part.

Broken Piston Rod Link
Broken Piston Rod Link

Transport Canada Comments:

It is possible that this unit would have failed on the next landing had maintenance not discovered the fault.

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