Fixed Wing

Overheated Automatic Direction Finder Control Panel

Airbus A310-304
(SDR) # 20120827017

SDR submitted:

During cruise, the flight crew reported smoke coming out of the Automatic Direction Finder (ADF) #2 control panel. The ADF #2 circuit-breaker was pulled but smoke continued to come out of panel. The panel was removed and disconnected and the smoke discontinued.

The ADF panel was sent to an approved repair shop for investigation.

A new serviceable ADF panel was installed, making the aeroplane serviceable.

Automatic Direction Finder input/output board short circuit and overheat

Transport Canada Comments:  

An in-depth investigation was performed by an approved overhaul facility where the following conclusion was stated: 

  • “The root cause has not been established, but it may be a short circuit between the ground and +28V DC transfer light signals localized:
  • at green indicator lights DS3 or DS4 (potentially caused by water intrusion)
  • or
  • on the I/O board between the ground and +28V DC transfer light tracks near the connector P1 (potentially caused by a foreign object, debris or pollution).”

It is important to note that for both scenarios of this conclusion, potential foreign object damage (FOD) was stated.

As maintainers of unpressurized piston powered aeroplanes to large turbine commercial jets, the cleanliness of our aeroplanes in being free of potential damaging debris or FOD is critical for its safe continued operation.

Alternating Current (AC) Power Feeder Cable

Bombardier BD-700-1A10
(SDR) # 20110826007

SDR submitted:

Shortly before entering operational service, a foreign interior completion center had installed the finished interior in the baggage bay. At this time, an upper intercostal was added to support the ceiling headline paneling. It was later found that the screws & bolts used to install the intercostal were excessively long and were chafing into the generator #1 power feeder cable. The feeder cable is installed above the headliner paneling and in an inaccessible area that the installer could not see while installing these improper screws.

Soon thereafter, it was discovered that the screws had damaged the insulation layers of the feeder cable and possibly the conductor of the feeder wires. The document holder will soon be issuing an engineering order to carry out a repair.

Chafing damage to the alternating current electrical power cable due to excessively long screws

Transport Canada Comments:

The above defect was entirely preventable and had the potential to have caused significant problems during flight. 

Personnel should be fully aware of the areas that they work in, particularly when drilling into hidden compartments. It is essential that the proper hardware/screws be installed. 

Cracked Pilot Seat Bellcrank

Cessna Equipment
(SDR) # 20120507021

SDR submitted:

The bellcranks were found cracked where they connect to the “crank-weld assembly” on both the left and right hand side. The pins that secure the bellcrank on the left hand side had partially sheared placing the load on 2 of the 4 holes and appeared to cause the cracks to spread open. Damage to the right hand bellcrank was less severe and the pins were intact. Complete failure of the bellcranks or securing pins would cause the seat backrest to fully recline without warning.

Damaged roll pin and cracked bellcrank

Transport Canada Comments:  

Seats are sometimes overlooked or not inspected as thoroughly as other items on an aeroplane. We must remember that they are an airworthiness item just as important as any other installed component. Should a seat back or locking device fail during a critical phase of flight such as during rotation, disastrous consequences could result. 

Upper Wing Strut Fitting – Crack

Cessna 208
(SDR) # 20120626016

SDR submitted:

While completing a scheduled inspection in the wing area, a significant crack was found at the aft portion of the upper wing strut fitting. Further inspection revealed that the crack located on the fitting ear left only 6.35 mm (14) of material remaining.

The eddy current inspection interval for the upper wing strut is set at 10 000 hours. In this case, the next inspection was still some 4333 hours away.

A cracked upper wing strut fitting

Transport Canada Comments:  

Cessna examined the failed right hand aft upper wing strut fitting part number (P/N) 2621008-202 and determined the mode of failure as high cycle fatigue. 

Fortunately, Cessna 208 wings are externally braced by struts that are redundant (double shafts and double fittings). This extra margin of ruggedness built into the type design ensured a margin of safety. 

Cessna are planning corrective action and will conduct additional cyclic testing on the wing struts to verify that the current inspection in Chapter 4 of the Model 208 Maintenance Manual (MM) is adequate. It is also Cessna’s position that any aeroplane operated on floats should be following the “Severe Inspection Time Limits” and not the “Typical Inspection Time Limits”. The Cessna MM will be revised accordingly. 

Main Wheel Rim Crack

Douglas DC-10-30F
(SDR) # 20130405007

SDR submitted:

A 1.8 cm (0.700 inch) long crack was found on the outboard wheel half during a routine shop overhaul procedure. The method used to detect the crack was a high frequency eddy current (HFEC) inspection. The crack originated on the mating surface between the spoke and bolt hole.

A half cracked wheel rim

Transport Canada Comments:  

The crack was detected using the HFEC method, Transport Canada Civil Aviation emphasizes the importance of close visual inspections during all daily and service check walkaround’s for all gear related equipment. 

Wing Slat Anti-Ice Hose Delamination

Dassault Falcon 10
(SDR) # 20130109009

SDR submitted:

During cruise flight, the crew noticed that the left wing inboard leading edge slat was not shedding ice with the anti-ice selected. Upon maintenance investigation, the anti-ice flex hose for the left inboard slat was removed and found to be delaminated in several areas of the inner lining.

The hose was replaced and the aeroplane was made serviceable.

A delaminated slat anti-ice flex hose inner

Transport Canada Comments:  

As explained by the operator, the remaining 3 other slat flex hoses were inspected where 2 more hoses with mild delamination of the inner lining were found.

All four slat anti-icing hoses were sent to Dassault (Falcon) Continuing Airworthiness Engineering. Through their investigative efforts, it was concluded that from the possible torsion imposed on the hose during installation, heat-buildup and delamination can occur. Due to this possibility, all affected Aircraft Maintenance Manual installation procedures were revised. 

Also, it was decided to de-escalate or drop the hard-time airworthiness limitation from 700 hours to 400 hours for this anti-ice hose. 

Elevator De-Icing Boot Failure

Dornier 328-300
(SDR) # 20120828006

SDR submitted:

The left-hand elevator horn failed in flight ("amber fail" on push-button annunciator panel).

Upon removal of the faulty left hand elevator horn assembly, maintenance noticed that the de-icing boot itself was deformed due to excessive heat. An elongated hole was also noticed on the de-icing boot and it is suspected that this is where an electrical short occurred, causing the overheat condition.

The fiberglass fairing was burned through and required replacement including the installation of a new de-icing boot.

Elevator horn de-icing boot overheated and deformed

Transport Canada Comments:  

The thorough maintenance investigation captured exactly what the amber fail light indicated. 

Bleed Air T-Duct Failure

Embraer ERJ 170-200 SU
(SDR) # 20121009002

SDR submitted:

During a scheduled maintenance inspection task, the engine bleed air T-Duct below the pre-cooler on the right-hand pylon was found cracked.

The T-Duct was replaced, making the aeroplane serviceable.

Cracked engine bleed air T-Duct

Transport Canada Comments:  

This would be the second Service Difficulty Report (SDR) reported by the operator in the past year for this type of T-Duct failure. 

The responsible type certificate holder for this aeroplane has been notified and Transport Canada Civil Aviation is advising all Embraer 170 owners, operators and maintainers to pay close attention to this area and duct. 

Failed Annunciator Switch

Fairchild SA227-AC
(SDR) # 20121002002

SDR submitted:

During taxi for takeoff, the crew noticed a left-hand (L/H) engine fire warning indication. Both engines were shut down and the passengers were deplaned.

As reported by maintenance, the fault was with the L/H fire bottle switch pushbutton which also acts as an annunciator light.

The switch is mounted inside a metal case where the spot-welds holding the switch within the case had failed allowing the switch to move around within the case due to normal vibrations. This caused the switch wires to ground-out on the case which lead to the false fire indication and the flight crews’ requirement to shut down both engines and evacuate the passengers.

The switch was replaced, making the aeroplane serviceable.

Failed switch spot-welds

Transport Canada Comments:  

An indication fault as seen here can be as serious as a true engine fire fault. 

Main Landing Gear Component Cracks

Gulfstream Aerospace 690D
(SDR) # 20120901001 & 20120901002

SDR submitted:

During a 5 year main landing gear (MLG) inspection, cracks were discovered in the uplock bracket (View A) and the drag-brace eyebolt (View B) by the non destructive testing (NDT) technician.

The discrepant parts were replaced and the MLG assembly was made serviceable for re-installation onto the aeroplane.

Standard main landing gear view. View A : Cracked uplock bracket. View B : Cracked drag-brace eyebolt

Transport Canada Comments:  

The requirement to NDT the faulted items for this landing gear at the 5 year visit are not required by the manufactures inspection maintenance program and it was through the proactive initiative of the maintainer that these cracks were found. 

As commented by the maintainer, it’s believed that even with a total failure of the drag-brace eyebolt and uplock bracket, due to the redundancy of the design, the gear would have functioned safely, yet operational discrepancies may be noted. 

Transport Canada Civil Aviation is advising all owners, operators and maintainers of this possible MLG condition. 

Heat Damage to the Windshield Anti-ice Nozzle

Learjet 35A
(SDR) # 20120710012

SDR submitted:

The flight crew reported a window overheat master caution when at 40 000 feet in cruise with the outside air temperature at -55 degrees C.

Maintenance troubleshooting discovered the windshield ram air modulating valve had internally failed (input shaft had separated from the internal bellows). The valve was replaced and the system function tested serviceable.

As a result of the failing windshield ram air modulating valve, both the left and right windshield anti-ice nozzle ducts received extensive heat damage.

The left and right ducts were removed for repair and the windshields were inspected for possible heat damage.

Heat damage of the windshield anti-ice nozzle ducts

Transport Canada Comments:  

Any form of windshield anti-ice nozzle heat damage is an indication of a failed pre-cooling or overheat detection system. 

Main Wheel Rim Failure

Learjet 35A
(SDR) # 20120812001

SDR submitted:

The aircrew reported a tire failure on roll out after landing. The tire was serviced the day before the flight where no-defects were reported. The #3 main wheel outboard rim was found to be severely damaged where it appears that a crack began at the rim bead and propagated around almost half of the rim circumference.

The aeroplane was inspected for possible foreign-object-damage (FOD), the wheel assembly was replaced and the aeroplane was returned to service.

A severely damaged wheel rim

Transport Canada Comments:  

Through discussion with the operator, it has been confirmed that for all tire assembly replacements, the rim halves require an eddy current inspection in the bead seat radius. Reference Learjet aircraft maintenance manual (AMM) 32-42-00. 

Main Landing Gear Door Attachment Fitting

Learjet 60
(SDR) # 20120531006

SDR submitted:

On departure during taxi-out, the line-maintenance crew notified the flight-crew that the left-hand main landing gear (MLG) door was flapping in the wind. Just prior to this, a Sikorsky S-92 had been operating in close vicinity to the aeroplane, violently rocking the aeroplane. It is suspected that the downwash from the helicopter caused the gear door fitting to crack as there was no dirt to indicate a pre-existing crack.

The fitting was replaced and the aeroplane was returned to service.

Broken attachment fitting on the main landing gear door

Transport Canada Comments:  

As seen in the illustrated parts catalog 52-80-11, the rod attachment to the MLG door is done through a bolt, washer, floating bushing and castellated nut with cotter-pin. The floating bushing ensures that there is no clamping or pinching effect on the attachment fitting of the MLG door when the nut is torqued. 

The correct installation for this attachment is critical to ensure the fittings integrity. 

It is also an essential point to note that after any form of adverse handling of an aeroplane, be that in the air or on the ground, that a specific maintenance inspection be done to prevent scenarios as such defined in this article. 

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