Fixed Wing

Nose Landing Gear Up-Lock Support Failure

BOEING, 727 227
SERVICE DIFFICULTY REPORT
(SDR) # 20110422001

SDR submitted:

As the aeroplane taxied away from the ramp, and on arrival to the runway threshold, the flight crew noticed a loss of hydraulic fluid pressure and hydraulic fluid quantity.

Maintenance was alerted and the aeroplane was towed back to the ramp. Hydraulic fluid was found coming from the belly drains aft of the Nose Landing Gear (NLG) bay. Further maintenance investigation found the NLG lock actuator leaking due to the lock actuator support bracket being cracked.

The bracket, actuator, hydraulic pump case drain filters and pressure filter were replaced, gear swing functional accomplished, leak checks and engine runs carried out and the aeroplane was made serviceable.

A cracked lock actuator support bracket

Transport Canada Comments:
Transport Canada Civil Aviation would like to advise all Boeing 727 operators of possible NLG lock actuator support bracket fatigue cracks.

Main Landing Gear Torque-Tube Failure

BOEING, 727 227
SDR # 20110620010

SDR submitted:

On approach, the crew selected the gear down but did not get confirmation (green indicator) of that the right main gear down and locked. The crew proceeded to perform the alternate extension procedure and was successful in acquiring the ‘down and locked’ indication.

After an uneventful landing, maintenance discovered the right-hand down lock torque tube sheared near the universal joint.

The torque tube was replaced, no further discrepancies were identified, and the aeroplane was returned to service.

A right-hand down lock torque tube sheared near the universal joint

* Right Main Landing Gear down lock torque-tube and corrosion noted

Transport Canada Comments:
The operator noted that the torque-tube universal joint attachment end was corroded, causing its failure.

Transport Canada Civil Aviation is advising all Boeing 727 operators and maintainers to pay close attention to this torque-tube assembly for any indication of possible corrosion.

Brake Fuse Failure

BOEING, 737 7CT
SDR # 20110426005

SDR submitted:

Maintenance discovered a hydraulic fluid leak in the right-hand wheel well. The right-hand normal brake hydraulic fuse was found to be leaking fluid where the fuse was subsequently replaced as per the Aircraft Maintenance Manual (AMM32-41-72, making the aeroplane serviceable.

It was noted by maintenance that the manual bypass lever and its hold down plate were missing. Also the attachment screws which secure the hold down plate were both fractured.

A Brake Fuse Body with a missing manual bypass lever and sheared attaching screws

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Missing manual bypass lever
Sheared attaching screws
Brake Fuse Body

Transport Canada Comments:
Transport Canada Civil Aviation would like to advise all Boeing 737 operators and maintainers of this possible brake fuse failure scenario.

Flap Power Driven Unit Support Channel Crack

BOEING, 747 SPJ6
SDR # 20110421005

SDR submitted:

Upon removing the flap Power Drive Unit (PDU) for access, maintenance found the support beam channel of the PDU cracked. The part was removed for repair per Structural Repair Manual 51-40-03 and the aeroplane was made serviceable.

An inspection was called by the operator for all leading edge flap PDU support beam channels on the remaining fleet.

A Power Drive Unit with a cracked support beam channel

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Corners to be inspected for cracks
Left-hand wing Power Driven Unit removed

Transport Canada Comments:
The initiative to inspect the complete fleet taken by this operator in order to advert a potential flap system failure is a proactive and responsible approach to aviation safety.

Wire Harness Clamp Failure

BOEING, 767 375
SDR # 20110503004

SDR submitted:

During the operational check of the hydraulic Power Transfer Unit (PTU) system, arcing was observed at a wiring harness clamp approximately 60 centimeters (cm) (2 feet) from the right hand electric hydraulic pump power connector.

The operational check was stopped; the wiring clamp removed which revealed chaffing and arcing of the electric hydraulic pump wiring.

The wiring was repaired; its associated clamp properly reinstalled and the aeroplane was made serviceable.

Electric hydraulic pump wiring with clamp damage due to its incorrect installation

* Clamp damage due to its incorrect installation

Transport Canada Comments:
Correct clamping for all electrical harnesses is essential for the continued and safe operation of all systems.

When a harness is clamped, there should be enough compression to gently support the wiring but enough slack to allow for sideways movement.

Main Landing Gear Upper Support Lug Crack

CANADAIR, CL 215 6B11(CL415)
SDR # 20110510002

SDR submitted:

During a scheduled gear inspection, maintenance found a 36 millimeter (mm) long by 5.5 mm deep crack on the forward left-hand lug of the upper member.

A cracked Main Landing Gear Upper Support Lug

Transport Canada Comments:
Further investigation by the operator has found other similar cracks in their fleet. Canadair has been involved in ongoing corrective action and has released an Alert Service Bulletins (ASB) detailing the Liquid Penetrant Inspection (LPI) as well as Eddy Current (EC) inspection procedures. The LPI is detailed in Service Bulletin (SB215-A4450 and SB 215-A547. The EC inspection is detailed in SB 215-A4451 and SB 215-A548. Transport Canada has recently issued Airworthiness Directive CF-2011-35 mandating these inspections.

Hydraulic Leaks Undetected

CANADAIR, CL 215 /415
SDR # 20110701003

SDR submitted:

Maintenance had been adding a litre of hydraulic oil after every water bombing mission. They found the nose landing gear actuator relief valve, part number 150-323, assembly had been spraying hydraulic oil under pressure out of the valve’s air vent hole when the nose landing gear was selected down. The actuator was removed and disassembled. Inspection found 2 O-rings severely damaged. Piston O-ring, part number MS28775-334, was split radially along the outside surface. The second O-ring, part number MS28775-225, had been rolled, cut and damaged. Any leakage out of the vent hole of the relief valve is a major cause for concern and the actuator should be removed for repair. Finding leaking oil in the nose wheel well area can be difficult as some water scooping operations may wash out the well.

A nose landing gear actuator relief valve with 2 severely damaged O-rings

Transport Canada Comments:
Any closed fluid system will lose some fluid. When an excessive amount needs to be added at regular intervals, it is an indication of a problem. In the above example, the washing of the nose compartment in scooping operations was likely masking the condition. Good job by the engineer who remained vigilant and discovered this snag.

Cracked Oil Tank

CANADAIR, CL600 2B19 (RJ100)
SDR # 20110502001

SDR submitted:

During a routine maintenance, high oil consumption was noted on the right-hand engine. The initial investigation indicated an oil leak on the engine. The engine was cleaned and ground runs were carried out. A crack in the top weld of the oil tank was found. The right-hand engine oil tank, part number 5079T05G01, was replaced and the aeroplane was returned to service.

A oil tank with a crack in the top weld

* Location of crack along weld line

Transport Canada Comments:
While the use of dye penetrant developer is a great tool for locating leaks, precaution must be taken to ensure that the developer is not applied to any surface that it might be incompatible with.

Nose Landing Gear Door Failure

CANADAIR, CL600 2D15 (705)
SDR # 20110309001

SDR submitted:

During a post flight walk around, the flight crew noticed damage to the aft Nose Landing Gear (NLG) door assembly. The aeroplane was grounded and a maintenance team dispatched.

After evaluation of the damages, the door assembly was removed and the aeroplane ferried to a maintenance base for repair. Visual inspection of the NLG area revealed that the aft door had sustained significant damage and needed replacement including both actuating rods. Also replaced was the NLG aft door drive bracket being bent and the steering control module.

The failure likely occurred during the gear extension of the flight as there was no abnormal noise or condition reported by the flight crew during flight.

A Failed Nose Landing Gear door

* Failed Nose Landing Gear door

Transport Canada Comments:
Transport Canada Civil Aviation is presently working with Bombardier Aerospace concerning this issue.

All operators and maintainers need to pay close attention to this area for condition and integrity.

Engine Oil Cooler – Broken Adaptor Fitting

DEHAVILLAND, DHC 8 102
SDR # 20110615005

SDR submitted:

The take-off was rejected (below 70 knots) when the left-hand engine oil pressure gauge indicated zero Pounds per Square Inch (PSI).

Maintenance soon discovered that the right-hand oil inlet tube adaptor fitting that connects to the left-hand oil cooler was broken and disconnected. This resulted in the loss of a substantial amount of oil in a very short period of time.

The oil cooler and the inlet fitting were replaced and the aeroplane returned to service. The oil cooler (part number 28E99-8) was only recently installed. It is suspected that the adaptor fitting may have had a hairline crack during the last installation. Please note that the adaptor fitting remains with the aeroplane when the oil cooler is replaced.

A broken right-hand oil inlet tube adaptor fitting

Transport Canada Comments:
Although fittings can suddenly fail without warning, it is important to always check for signs of oil leaks around the engine area.

#1 Hydraulic System Depletion

DEHAVILLAND, DHC 8 102
SDR # 20110630002

SDR submitted:

During climb; the crew observed that the #1 Hydraulic System was gradually depleting. Rather than return to the departure airfield, the pilot elected to continue on to the planned destination due to weather conditions and runway length considerations. Near the planned destination, the crew declared an “emergency” and landed without incident.

The loss of #1 Hydraulic System resulted in the loss of wing flaps, inboard roll spoilers, lower rudder actuator, normal braking and anti-skid function.

Maintenance personnel found that the leak originated somewhere in the tail section area. Further investigation revealed 3 pin holes on the pressure supply hydraulic tube that connects to the rudder dual pressure regulator. The holes are located on the outside of a 180-degree elbow. The defective hydraulic line and engine driven hydraulic pump were replaced and the aeroplane returned to service.

Regulator installation-empennage dual pressure

* Regulator installation-empennage dual pressure

Transport Canada Comments:
Any bends in hydraulic tubing can result in stresses that can fail without notice. It is important to ensure bends do not exceed manufacturers’ recommendations.

In this case, depletion of #1 hydraulic system presented the crew with a very challenging landing.

Dangers of Homemade Tooling

DEHAVILLAND, DHC 8 311
SDR # 20110620005

SDR submitted:

Aeroplane parts (propeller cuff) were found on runway. The parts were given to a local shop where the director of maintenance determined they were off of a Hamilton Sunstrand propeller (identified by the part number on the pieces found).

The director of maintenance contacted the aeroplane operators who use the airport. It was determined the part separated during the take-off. The aeroplane was identified and taken out of service for repair.

Investigation revealed the part may have been damaged from tooling used to remove the spinner during a propeller balance session. The tooling was located and a test conducted to determine if the tool (homemade) could have caused the damage. This was confirmed and the tool was removed from service. All personnel involved were given coaching to prevent reoccurrence. A new blade cuff was reinstalled. The aeroplane was returned to service.

Transport Canada Comments:
Instances such as the one above are most likely to occur when deviating from the manufacturer’s approved tool list and/or procedures. Extra caution must be used, particularly when combined with the time constraints this industry often imposes.

Rudder ‘S-tube’ Wear

DIAMOND, DA 20C1
SDR # 20110531005

SDR submitted:

Prior to start-up, the pilot noticed that he wasn’t able to adjust the rudder pedals. After a visual inspection, the Aircraft Maintenance Engineer (AME) noticed that the left pilot side rudder pedals ‘S-tube’ had the rudder cable protruding from one of the bends. Both pilot side rudder pedals were replaced and further inspection revealed that the right side had significant wear.

A rudder cable protruding from a bend in the 'S-tube'

* Rudder pedal ‘S tube’ wear

Transport Canada Comments:
According to the manufacturer, the only time the cables move through these tubes is during pedal adjustment. In a situation where an individual pilot is operating the aeroplane and little or no pedal adjustments are made, this should never be an issue. In a flight-training environment where many pilots are operating the machine, extra care must be taken by the maintainer to inspect this area carefully.

The manufacturer is looking into alternate lubricants that may help reduce wear.

Flap Bellcrank Wear

DIAMOND, DA 42
SDR # 20110427001

SDR submitted:

The split flap bellcrank has a 0.1524 millimeters (mm) (0.006 inches) deep wear mark on the flap actuator lower arm. The material thickness in this area is 1.651 millimeters (mm) (0.065 inches). The wear was caused by interference with the flap actuator rod end. The combination of both the rod end alignment and bushing location can cause wear.

A worn flap bellcrank

* Arrow indicates location of wear (Approximately 0.006 inches deep)

Transport Canada Comments:
This appears to be an area that could be difficult to detect any anomalies. Operators should be aware of this potential wear spot.

Chaffed wiring

GROB-WERKE, G120A
SDR # 20110412009

SDR submitted:

Multiple wires on ground block module VN220, behind the right-hand instrument panel, were found with abrasion damage caused by chaffing on the engine instrument display. Several wires were found with the insulation damaged through to the conductor.

Damaged wires discovered during scheduled inspection

* Damaged wires discovered during scheduled inspection

Transport Canada Comments:
Great job by the maintenance engineer who discovered this issue before it became a bigger problem. A fine example of vigilance and thorough inspection.

Spoiler Panel Quality Escape

 LEARJET, 35A
SDR # 20110316006

SDR submitted:

During a routine wing spoiler panel change and installation, maintenance found the hinge holes on both replacement panels to be beyond serviceable diameter limits. They also found fasteners missing and holes not even drilled on all three mounts. Maintenance contacted the supplier and was told that they did an inspection of their stock of spoiler panels and found numerous issues with other spoiler boards.

This Service Difficulty Report was issued due to the fact that these defects could easily be overlooked by the installer.

Transport Canada Comments:
Through the co-operative research done with Learjet engineering and the Federal Aviation Authority (FAA), it was determined that the missing fasteners noted on the new spoiler panels were intentionally not installed in order to provide for initial fitting of the panel upon installation. Special spares kit # SSK 0936E provides the necessary work instructions and are to be complied with when installing and fitting new replacement spoiler panels.

Also confirmed with Learjet engineering, the hinge hole size was incorrect and is considered a quality escape to which all affected spoiler panels were purged and quarantined from stock.

Learjet is planning to issue a Service Bulletin to address this issue for all in-service operators along with an Aircraft Maintenance Manual (AMM) revision to reflect correct spoiler panel installation procedures.

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