Fixed Wing

BOMBARDIER, CL600 2B19 (RJ440)
SDR # 20091228003
Main Landing Gear Swivel Brake Line Installation

SDR submitted:

During a heavy maintenance visit, while performing brake system bleeding, maintenance personnel found that hydraulic system No.2 was actuating the in-board brake carriers and that hydraulic system No.3 was actuating the out-board brake carriers. As per Aircraft Maintenance Manual (AMM), this was an incorrect configuration.

After research it was noted that the hydraulic lines at the swivel fittings were reversed and were not properly installed on both main landing gears.

All hydraulic lines were re-oriented correctly and the brake system was found serviceable.

The aircraft arrived at the maintenance facility with no abnormalities noticed by the flight crew, however with these hydraulic lines reversed, the aircraft’s anti-skid system would have worked opposite to the anti wheelskid requirements and could have severely affected the controllability of the aircraft while landing in wet or bad weather conditions, including the possibility of tire failure.

Transport Canada Comments:
Incorrect hydraulic brake line configuration could potentially have been very serious if it had remained undetected.

The operational task within the AMM removal – installation procedures for these brake swivels, if done correctly, would have detected the incorrectly configured brake line.

Always ensure to follow all AMM task procedures.  Hammer and wrench in X formation indicating end of article

Incorrect hyd line installation

AMM 32-11-20

SDR # 20100330001
Inspection Requirement for the Installation of Serviceable Parts

SDR submitted:

During a heavy maintenance visit on a CRJ100 aircraft, multiple repeated snags for flat and deflated landing gear were raised. While replacing the nitrogen servicing schrader valve o-ring on the gear strut, it was noted by maintenance crew, that the new and old o-ring packings were found with a surface finish defect, causing the MLG gears to loose its gas charge.

A magnified visual inspection of the o-ring surface finish, as seen in the attached figure, confirmed this manufacturer’s defect, in comparison to a correctly manufacturer o-ring.

Transport Canada Comments:
Despite mandated quality assurance programs that exist throughout the industry, quality escapes still occur. Therefore it is essential that attention be given to the condition of serviceable parts being installed on aircraft.  Hammer and wrench in X formation indicating end of article

A correct surface and serviceable o-ring

SDR # 20090929002
Flap Torque Tube - Sheared

SDR submitted:

On final descent to airfield, the flight crew noticed that the “flap drive” caution light illuminated immediately following the specified flap selection.

Following an uneventful landing, the maintenance crew inspected the visible sections of the flap drive train and discovered the R/H #4 flap torque tube had sheared. It appeared that the torque tube had been chafing against one of the flap shroud hangars. The chafing was a result of either an unbalanced torque tube condition, or a slight bend/distortion in the actual torque tube. The chafing was mostly concentrated at approximately 120 degrees of the outside diameter of the torque tube. However, the remaining torque tube wall was paper-thin.

Transport Canada Comments:
It is apparent that this chafing existed for some time. It is essential that proper inspections be carried out with the flaps lowered for proper visual access.  Hammer and wrench in X formation indicating end of article

Flap Torque Tube

SDR # 20100331003
Engine Mount Weld Failures

SDR submitted:

During a letter check inspection, maintenance found on the R/H engine, the upper outboard engine mount sheared off at the firewall attachment point.

The inner attachment bolt was still in place, however the engine support truss tube had separated from the flange or end-cap by a crack of the weld.

The complete engine truss assembly was replaced with a serviceable unit.

There was no snag or indication from the previous flight crew for any form of engine or airframe vibration.

Transport Canada Comments:
The engine truss mount is attached to the firewall at four attachment points. Each point of the mount has an endcap welded to the truss end with an internal attaching bolt, as seen in detail A.

Failure of this weld could amount to a catastrophic failure of the aircraft.

TCCA would like to bring to the attention of all owners and operators, the importance of a detailed inspection of all engine mounts, especially following a turbulent flight, propeller strike or a hard landing. The Fairchild Service Bulletin 227-71-008 has been raised to address this endcap fault.

This issue is currently under investigation with TCCA and the FAA.  Hammer and wrench in X formation indicating end of article

Top Outboard firewall attach fitting

End-cap attachment point

SDR # 20100427009F
Horizontal Stab Backlash Wear and Trunnion Bolt Corrosion

SDR submitted:

While maintenance was performing a routine horizontal stab trunnion bolt lube, it was noticed that there was excessive vertical movement (backlash) of the stab at the forward leading edge. A free play check was carried out as per AMM and the measurement was found in excess of the maintenance manual by 0.635 cm (0.250 inches). Upon further investigation, the removal of the bolt assembly was very difficult because of excessive corrosion found. The vertical stab bushings were also heavily worn, which added to the horizontal stabs excessive backlash.

Both sets of bushings and the bolt assembly were replaced and shimmed correctly as per the AMM and the aircraft was released for service.

Transport Canada Comments:
Despite a well-defined and established maintenance program for Fairchild aircraft, maintenance personnel are encouraged to always take note of any amount of backlash found on all flight controls. Hammer and wrench in X formation indicating end of article

Stab backlash wear

SDR # 20100504004
Aileron PCU Centering Rod Failure

SDR submitted:

During a scheduled “B”- check maintenance visit, the R/H Aileron PCU External Centering Spring Rod was found broken.

The function of this rod is to ensure the Aileron PCU returns to its neutral position (Aileron panel faired at 0) in case of a pilot Aileron control input disconnect. This rod experiences a twisting force when the ailerons are moved and acts as a return spring for the PCU shuttle valve to the neutral position.

The rod is located in such a position that it would be hard to detect and could go unnoticed until a functional text is carried out or a specific inspection is accomplished.

A new rod was installed with the assistance of Gulfstream and the aircraft was made serviceable.

Transport Canada Comments:
TCCA is advising all operators and owners to inspect the condition of both the aileron PCU and the external centering spring rods.

TCCA is presently working with both the FAA and the CAAI (Continuing Airworthiness Authorities of Israel) to access and address this issue. Hammer and wrench in X formation indicating end of article

Centering rod failure

SDR # 20100203010
Passenger Door – Severe Internal Corrosion

SDR submitted:

Following his last flight of the day, the pilot noticed that the main cabin door structure was coming apart at the location where the door is hinged to the lower fuselage. Further investigation by maintenance personnel revealed severe corrosion of the honeycomb inner door structure. Some rivets that attach the bonded assembly to the door had also failed.

The SDR submitter stated that the older Beech 1900C cabin doors have a steel doubler installed that is riveted and bonded together. This configuration made this particular area difficult to inspect until bulging and/or door skin separation occurred.

Transport Canada Comments:
This specific area of the cabin door is inspected at every 1200 hours. Additionally, model 1900 Airliner Series Corrosion Control Manual, Task 52-10-01, provides further instructions and procedures to detect corrosion.

It is recommended that frequent visual inspections of the area be carried out to detect signs of internal corrosion.

The cabin door is constantly exposed to moisture/dirt contaminants. The constant opening and closing of the door and numerous pressurization cycles further stress/ fatigue the integrity of the door structure.  Hammer and wrench in X formation indicating end of article

Passenger Door -Severe Internal Corrosion

SDR # 20091118013
Horizontal/Vertical Stabilizer Interface – Cracked Doubler

SDR submitted:

During a 1200 Hour Scheduled Inspection, a 7.62 cm (3 inches) crack was found on a manufacturer’s installed doubler, located at the horizontal/vertical stabilizer tailplane interface. The aircraft was immediately grounded pending further investigation. Maintenance personnel confirmed that all of the screws were properly secured, however several screws still spun freely.

The SDR submitter stated that it appeared that the loose screws might be a result of the 7.62 cm crack.

Transport Canada Comments:
Aerodynamic stresses on the horizontal/vertical stabilizer during flight regime can be significant. Any loose hardware in this area can cause undesirable vibrations during flight. Hammer and wrench in X formation indicating end of article

Horizontal/Vertical Stabilizer Interface

SDR # 20090123004 &20070202007
Elevator Torque Tube - Cracks

SDR submitted:

During major overhaul; the elevator bellcrank torque tube was removed for routine maintenance. Inspection revealed that the bellcrank arms were loose. After removal of the arms, non destructive testing (NDT) inspection revealed cracks on two of the eight taper pin holes.

An earlier SDR also reported a crack which started at the horn attach taper pin and spiraled 270 degrees around the elevator torque tube. In this case, the crack progressed very rapidly since the last inspection that was carried out 82 hours previously.

Transport Canada Comments:
An SDR search revealed several other reports of elongation/wear of elevator bellcrank taper pinholes. It appears that the taper pinholes may have been incorrectly drilled (oversize) during manufacture. To preclude undesirable flutter related problems; it is recommended that owners/operators be attentive to any excess play in the elevator controls.

Transport Canada has advised the responsible foreign airworthiness authorities of these defects.  Hammer and wrench in X formation indicating end of article

SDR # 20100423008
Flap Roller Bearings/Bushings - Wear

SDR submitted:

During descent to the airport, the appropriate flap selection was made when suddenly the flaps stopped and the ailerons became difficult to move. The crew then selected flaps up but no movement occurred. The crew declared an emergency and carried out an uneventful landing at a nearby airfield. It was later found that the aft attachment point on the L/H outboard flap, had failed inside the flap.

During the above failure sequence, the flap actuator continued to drive the flaps until the asymmetrical flap protection system activated thereby removing electrical/ hydraulic power from the flaps. Just prior to activation of flap protection system, the flap had pushed the inboard end of the L/H flap further aft (instead of down) which then caused interference with the aileron. The Beech maintenance manual specifies a clearance of 0.4826 cm (0.190 inches) between the flap and aileron; however, the flap was now pushed out of position far enough that contact was made with the inboard trailing edge of the aileron. The flap required minor skin repairs and the inboard and outboard flap ribs were replaced.

The flap is attached through two ribs on either side of the flap track. The flap roller assembly consists of a roller bearing, a large “hat” section and a Teflon washer. All these parts were found to be jammed into the flap track. It became apparent that the “hat” section bushing had been spinning and wearing into the outboard rib until the Feedback 3/2010 9 material, 1.27 cm (0.50 inches) thick, eventually failed resulting in a jammed flap.

Further inspection revealed that the problem appears to originate with the roller bearings. The BC-56985 bearings are inside the large bushing and premature wear causes the bearing to move inside the bushing. The operator has modified their B300 inspection program to include a specific requirement to inspect this area both on the detailed 800 hour interval and the routine 200 hour interval inspection. A precautionary inspection on their other B300 aircraft revealed similar premature wear.

Transport Canada Comments:
TCCA raised this issue with the FAA and Hawker Beechcraft (HBC) who stated that they have not had previous reports of this nature, however premature roller wear appears to be the root cause of this event. There is a previous service bulletin to replace the flap rib next to the actuator (not the rib next to the flap track). HBC have stated that the current maintenance instructions are specific on the inspection of this area.

It is important to note that flaps are at times subjected to significant aerodynamic loading (buffeting) during take off, approach and landing; thus it is important to carefully inspect these areas for premature wear and/or damage. It is also essential that flaps and all flight controls be precisely rigged in accordance with manufacturers instructions.  Hammer and wrench in X formation indicating end of article

Flap Roller Bearings


PIPER PA24 250
SDR # 20091109003
Horizontal Stabilator Horn - Cracked

SDR submitted:

A precautionary inspection was carried out on the stabilator horn due to reports of cracking on other aircrafts. No cracks were visible from the horn exterior; however, removal of the 2 stabilator halves, the torque tubes and the horn assembly was necessary in order to inspect the inner wall of the horn.

Close examination with magnification and dye penetrant revealed a crack running from each attachment through a bolthole to the balance tube hole on the forward side of the horn. The crack found in the cast aluminum horn appears to be caused by stress corrosion.

Transport Canada Comments:
Currently, the horizontal stabilator area is the subject of the following FAA Airworthiness Directives (ADs):

  • 74-13-01 Stabilator Torque Tube
  • 74-13-03 Stabilator Attachment Bolts
  • 76-19-07 Stabilator Weight Assembly
  • 94-13-10 Stabilator Torque Tube Bearing Support

In this particular case, the stabilator horn had cracks occurring at the boltholes that may be directly related to FAA AD 74-13-03 (installation of corrosion resistant AN bolts). Any corroded bolts must be changed before further flight. Hammer and wrench in X formation indicating end of article

Horizontal Stabilator Horn

PIPER PA24 250
SDR # 20091117001
Main Landing Gear – Retraction Push- Pull Cable Conduit

SDR submitted:

A domestic operator reported that the R/H landing gear collapsed during landing and caused the aircraft to veer off the runway. Subsequent investigation revealed that R/H retraction push-pull conduit was worn between the inner and outer sleeves. Separation of the sleeves did not allow the gear to extend to the full down and locked position. Significant corrosion was also found on the sleeve assembly.

A service history review has revealed numerous problems with the cable conduit assembly resulting in failure of the landing gear to extend fully or retract. Additionally, the retraction motor circuit breaker has popped on numerous occasions, which was directly linked to lack of lubrication of pertinent parts. Other defects such as binding or worn cables have also caused landing gear malfunctions.

Transport Canada Comments:
The electrically powered landing gear is subject to environmental contaminants that promote corrosion, thus it is essential that adequate lubrication and inspections be carried out. Inspect push-pull cables for signs of excess wear, corrosion, freedom of movement and bends and cracks of the threaded ends.

Please also refer to FAA Special Airworthiness Information Bulletin (SAIB) CE-08-50 titled “Landing Gear Manual Extension System Inspection” and Piper Service Letter 782B. These documents emphasize the importance of regular/preventive maintenance. Hammer and wrench in X formation indicating end of article

Pull cable conduit

PIPER PA31 350
SDR # 20090616005
Aft Upper Fuselage Door

SDR submitted:

Shortly after take off, the crew heard a loud rushing air sound, which was quickly identified as the upper portion of the aft passenger door coming slightly ajar. As the crew was finishing the turning back procedures to the airfield, the upper portion had then become completely open due to inflight aerodynamic forces.

Following flight, the pilot reported obvious metal scarring on the fuselage doorframe, perhaps indicating that both the upper and the lower stair door locking mechanism were engaged prior to flight. Because the cockpit “door unsafe” light never illuminated, this would indicate that the lower portion of the aft door remained secured during this event.

Post flight inspection revealed that the forward aft upper door hinge had failed and separated from the door frame/fuselage interface, just leaving the rear hinge to hold the upper door in place. Because there are several contributing factors related to this event; it is unknown if it was the upper door hinge or the upper door latches that failed first.

Transport Canada Comments:
A review of SDRs revealed other door failures with a complete door separation, which damaged the aircraft during flight. Other door unsafe events were caused because of the worn door latching mechanisms (bushings/ springs, latch plates and door cables).

TCCA recommends that owners/operators pay particular attention to premature wear of the door latching mechanisms. Any difficulty in opening, closing or securing the door should be an early indicator of impending failure.

TCCA has reported the above door failure to the FAA for their action with the OEM. Hammer and wrench in X formation indicating end of article

Aft Upper Fuselage Door

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