Fixed Wing

Extensive Pressure Bulkhead Corrosion

AIRBUS, A310 304
SERVICE DIFFICULTY REPORT
(SDR) # 20120504003

SDR submitted:

During a standard maintenance inspection check, extensive corrosion was found at forward wing-box bulkhead frame 39. The corrosion had perforated the pressure structure between stringers 55 and 54 left-hand side below waterline z-2557.

The bulkhead was repaired through the guidance of an Airbus Repair Approval Sheet (RAS) and made serviceable.

Wing-box pressure bulkhead

* Wing-box pressure bulkhead
extensive corrosion

Transport Canada Comments:
The standard inspection interval of this area is set at a 5 year interval where this aeroplane was last inspected on March of 2011. Depending on the aeroplanes operating environment and upon the operators’ discretion, this interval can be reduced to accommodate possible discrepant findings as seen with this service difficulty.

Main Landing Gear A-Frame / V-Braces - Cracks

Beech 76
SDR # 20110210006

SDR submitted:

Following a landing, it was discovered that the left hand main landing gear V-brace was separated from the gear actuator point. Had the aeroplane taxied any further, the landing gear would have collapsed. A precautionary visual inspection on the right hand landing gear also revealed that the right hand V-Brace was cracked.

A detailed inspection using the magnetic particle inspection (MPI) technique on another aeroplane in their fleet found both the right hand & left hand V-braces to be cracked.

Main landing gear with a

* Main landing gear with a broken V-brace

Transport Canada Comments:
Beechcraft Service Bulletin (SB) 2361 recommends that should fatigue cracks be found on the main landing gear “A” Frame assemblies, then to install subject part number 105-8100-75 & 76. This should further support the strength of the attachment bracket for the hydraulic actuator connection.

Federal Aviation Authority (FAA) Airworthiness Directive 97-06-10 mandates SB 2361 to inspect the “A” Frame assemblies using both visual and dye penetrant methods but not MPI methods. The FAA has been advised accordingly.

Main Passenger Door Hinge & Channel Defects

Beech A100
SDR # 20111108004

SDR submitted:

During servicing for the next flight, it was noted that the main cabin door lower step would move when stepped upon. Further investigation found the lower door channel had a 15.24 cm (6 inches) crack and the door side half hinge was broken 5.08 cm (2 inches) from the aft end. The channel (part number (P/N) 50-430043-619) half hinge (P/N 50-430043-547) and hinge pin (P/N 50-430043-393) were replaced due to severe corrosion.

Severely corroded lower door channel

* Door Half Hinge
** Crack
*** Door Channel
**** aft
***** Crack
****** inboard
******* Severely corroded lower door channel

Transport Canada Comments:
The main door and steps require continuous inspections due to consistent use from passengers and exposure to environmental contaminants that promote corrosion. In this case, it appears that this step had been in this deteriorated condition for some time.

Main Landing Gear Anti-Skid Harness Incurred Damage

BOEING, 757 28A
SDR # 20120126011

SDR submitted:

During taxi, the anti-skid warning light illuminated intermittently. The anti-skid system was deferred in accordance with the Minimum Equipment List (MEL) 32-42-01-1 and the aeroplane was returned to service.

At the next maintenance opportunity, an investigation revealed that a clamp assembly was broken and had failed on the gear truck/bogie. The anti-skid wiring and conduits were also damaged. The damaged clamp, wiring and conduits were repaired making the aeroplane serviceable.

In order for this damage to occur, it appears that the plate assembly that the clamp secures was being pulled upwards (with the oleo at full extension) by the two flexible wiring conduits that travel up the gear strut.

Missing gear truck clamp with

* Missing gear truck clamp with lifting plate assembly

Transport Canada Comments:
Further investigations revealed that these two flexible conduits on the right-hand (R/H) gear were about 5 cm (2 inches) shorter than the ones on the opposite main landing gear causing the stress on the clamp.

The investigation is still ongoing into this apparent discrepancy of gear harness conduit length and is suspected to be a quality control issue from the supplier of the discrepant harnesses. In the meantime, Transport Canada Civil Aviation (TCCA) would like to advise all owners, operators and maintainers of this possible condition of clamp failure.

Worn Aileron Power Control Unit Attachment

BOMBARDIER, CL600 2B19 (RJ100)
SDR # 20120112003

SDR submitted:

The Aircraft Maintenance Engineer (AME) was performing a detailed inspection of the right-hand (R/H) aileron panel and surrounding area as per a planned task when he found the R/H aileron out-board power control unit (PCU) link attachment fitting on the aileron to be worn. The excessive wear occurred where the attachment bolt flange bushing is installed. The flange bushing was found loose and had migrated slightly and showed evidence of rotating within the link-fitting.

The aileron panel assembly was replaced with a serviceable unit and the aeroplane was returned to service following the heavy maintenance check.

Aileron power control unit worn

* Aileron power control unit worn link fitting and flange bushing

Transport Canada Comments:
This condition can cause excessive backlash in the aileron system and damage to the PCU link and attachment fitting.

Transport Canada Civil Aviation (TCCA) is advising all CRJ100/200 owners, operators and maintainers of this possible condition.

Nose Landing Gear Door Actuator Mount - Cracks

BOMBARDIER, CL600 2B19 (RJ100)
SDR # 20111125002

SDR submitted:

During a routine inspection, the maintenance engineer found cracks on both lower lugs of the nose landing gear (NLG) door actuator support base.The base is mounted on the right wall in the forward section of the nose wheel well.

The base was replaced and the aeroplane was made serviceable.

NLG door actuator support base cracks

* NLG door actuator support base cracks

Transport Canada Comments:
Transport Canada Civil Aviation (TCCA) and the responsible type certificate holder, Bombardier, are working together in assessing this type of failure and its potential implications.

TCCA would like to advise all owners, operators and maintainers of this NLG door actuator support base failure possibility.

Flap Torque-Tube Chaffing

BOMBARDIER, CL600 2D15 (705)
SDR # 20111216004

SDR submitted:

During a routine service check inspection, circumferential damage was found on the left-hand flap drive torque-tube at wing station (WS) 128 to WS 97. It was discovered that the torque-tube had been rubbing on the plastic containment ring during flap operation and maximum wing deflection, causing a chaffing condition.

The torque-tube was worn beyond limits and was replaced making the aeroplane serviceable.

Flap torque-tube wear groove due to chaffing

* Flap torque-tube wear groove due to chaffing on the containment ring during flap operation and maximum wing deflection
** Forward

Transport Canada Comments:
Bombardier Service Bulletin (SB) 670BA-27-049 introduces a slightly larger containment ring to increase the clearance with the torque-tube and removes the possibility of a chaffing condition during flap operation and maximum wing deflection.

Auxiliary Power Unit Oil Filter Damaged

BOMBARDIER, CL600 2D15 (705)
SDR # 20120103001

SDR submitted:

A collapsed filter was found during a scheduled replacement of the auxiliary power unit (APU) oil filter element per task 000-49-360-714 (2000 hours interval). The filter was replaced, leak checked and the aeroplane was released for service.

The filter had no trace of excessive contamination to cause the element to collapse where the likely cause was determined to be due to an incorrect installation.

Damaged/collapsed auxiliary power

* Damaged/collapsed auxiliary power unit oil filter element

Transport Canada Comments:
It is important to note that for the correct installation of the APU oil filter and to prevent its inadvertent damage, the filter element must first be installed to the lube-module, followed by the oil filter bowl assembly.

Rudder Hinge Assembly Flange - Crack

DHC 3T
SDR # 20110929016

SDR submitted:

A visual inspection revealed a stress corrosion crack 6.35 cm (2.5 inches) in length, located on the lower rudder hinge bracket flange extension, adjacent to the rudder push pull rod end attachment point.

The rudder was removed to facilitate the replacement of the bottom bracket.

Lower Rudder Hinge Bracket Flange

* A Lower Rudder Hinge Bracket Flange

Transport Canada Comments:
Possible contributing factors to stress corrosion cracks could be attributed to flight loads associated with floatplane operations, salt water environment and exposed rudder actuating rod end.

Nose Landing Gear Drag Strut Actuator – Flex Hose Failures

DHC 8 300 series
SDR # 20110919003

SDR submitted:

After gear up selection, the nose gear did not fully retract and the nose wheel remained extended with the doors still open. The crew noted that #2 hydraulic fluid level and hydraulic pressure were rapidly depleting. The crew declared an emergency and carried out a manual (alternate) gear extension. This situation was compounded by loss of several other aircraft system reliant on #2 hydraulic pressure. Fortunately, an uneventful landing was carried out.

Maintenance personnel soon discovered that a nose landing gear (NLG) drag strut flexible hose had failed at the T-fitting resulting in fluid depletion and pressure from the #2 hydraulic system.

The operator had earlier self-imposed a precautionary life limit of 10 000 cycles and additional inspections on the subject hose in order to reduce hose failures.

Transport Canada Comments:
Bombardier had previously published an article in their monthly ISAR (In-Service Activities Report) 2000-11-3230 to advise and instruct operators on the importance of correct installation/orientation of the T-fitting. In order to prevent leakage and failures; the T-fitting should be installed at a 15-20 degree angle orientation from vertical. This will alleviate pre-loading and kinking as well as reduce failures of the flex hose when the NLG is in the retracted position. The aircraft maintenance manual (AMM) 32-30-36 has been amended accordingly.

Additionally, Transport Canada published Service Difficulty Alert (AV 2003-11) recommending compliance with Bombardier ISAR 2000-11-3230 and adherence to AMM 32-30-36.

Underfloor Electrical Wires - Chafing and Shorting

DHC 8-102
SDR # 20111021007

SDR submitted:

During taxi out for departure, the crew noticed a strong burning smell in the cabin and cockpit. The pilot elected to stop the aeroplane in the central deicing facility and the flight attendants proceeded to disembark all passengers.

During maintenance troubleshooting, several unusual defects were noted. The #2 cargo smoke detector failed to “test”, the #1 standby pump “hot” caution light illuminated and the #1 bleed control circuit breaker “popped” whenever the switch was selected to “off”. Further investigation revealed numerous electrical wires in the wiring channel located under the cabin floorboards on the left-hand side at passenger Row 1, were chafed/blackened and “shorted” to each other. The damaged wires were repaired, electrical circuits tested and aeroplane returned to service.

The wiring in this area was previously inspected and modified in accordance with Airworthiness Directive (AD) CF-1998- 08R2 that mandated Modification 8/2705 and Bombardier Service Bulletin (SB) 8-53-80.

Underfloor Electrical Wiring

* Underfloor Electrical Wiring

Transport Canada Comments:
It is advisable that maintenance personnel be particularly mindful regarding the condition of electrical wiring, particularly in older model aeroplanes.

Hose Clamp Miss-install

DORNIER, 328 300
SDR # 20120224002

SDR submitted:

Following the troubleshooting of an air-conditioning fault, an unusual noise was heard coming from under the floor area around frame 20 (mid fuselage) when operating the rudder pedals.

A visual inspection confirmed that a stainless steel hose clamp for an air-conditioning distribution duct was mistakenly secured around an adjacent rudder control cable.

Chaffing marks were found on the transverse floor beam channel and a repair was performed as per Structural Repair Manual (SRM) 53-00-5.

The rudder cable was visually inspected, tension checked and a Non-Destructive Testing (NDT) was performed, with no faults found.

All other cables in the sub floor area were inspected for the same potential defect with no fault found making the aeroplane serviceable.

Miss-installed hose clamp,

* Miss-installed hose clamp, affecting a rudder pedal flight control cable

Transport Canada Comments:
An obvious mistake from the installer where the lesson learnt and standard to take would be to always perform a complete visual inspection of the installed part and its surrounding area to ensure for its correct installation.

Cracked Main Landing Gear Retract Actuator Spacers

LEARJET, 60
SDR # 20120209006

SDR submitted:

The conical spacer was discovered cracked when the left main landing gear (MLG) retract actuator was removed for access to address another problem. The right MLG was also found with the same cracked conical spacer.

The nature of the crack indicates it is being over-loaded on the conical surface resulting in the fracture.

Both of the conical spacers were replaced, making the aeroplane serviceable after the initial problem was corrected.

Illustrated Parts Catalogue main landing gear

* Illustrated Parts Catalogue main landing gear side-stay actuator and attachment hardware.
* Cracked conical spacers, Item 32

Transport Canada Comments:
Bombardier Learjet engineering have been advised of this event, including two others in the past 4 years. Learjet analysis has confirmed that the cracking of these spacers is due to stress corrosion and does not create a safety issue.

Transport Canada Civil Aviation is advising all Learjet 60 and 35A owner, operator and maintainers of this possible condition.

Main Landing Gear Oleo Housing - Cracked

Piper PA 31-350
SDR # 20111205001

SDR submitted:

Maintenance crew noticed that fluid was leaking around the main landing gear (MLG) shock strut area. After dismantling the brake line bracket that is attached to the strut, a 3.81 cm (1.5 inch) crack was found.

The landing gear trunnion was replaced and the aeroplane was returned to service.

Transport Canada Comments:
A service history review revealed a number of previous service difficulty reports (SDRs) reporting mild to severe corrosion around the area where the stainless steel clamp retains the brake line to the oleo housing. Dissimilar metals are a contributing factor to this corrosion problem.

Additionally, the landing gear is in line with the exhaust trail emissions and this combined with the clamp holding moisture can also promote corrosion.

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