Landing gear/indication

Shortly after take-off, as the landing gear retracted, the crew heard a loud bang. The crew detected a potential issue with the landing gear and began troubleshooting the problem. The crew noted that the red landing gear transit warning light had remained illuminated. They cycled the landing gear on several occasions, which resulted in the green main landing gear down indicator lights illuminating, but not the nose landing gear (NLG) light. The transit light also remained illuminated. 

The aircraft arrived at Toowoomba, Queensland and a pass over the runway confirmed that the NLG had extended but was not in the locked position. The crew then referenced the wheels up landing procedure and formulated a plan.

During the subsequent landing, the aircraft’s nose lowered and slid along the runway. The aircraft came to a stop and the crew exited.

An examination of the aircraft determined that the rod end on the NLG forward retract rod assembly had separated from the plunger tube on the NLG plunger assembly. The affected components were further examined by the aircraft manufacturer who determined that copper braze had not been placed inside the plunger tube before the rod end had been inserted during the manufacturing process, which was conducted by an external supplier. 

As a result of this occurrence, the aircraft manufacturer released a Mandatory Service Bulletin for the inspection, and if necessary, replacement of the affected plunger assemblies. They further advised the ATSB that the manufacture of the plunger assembly will now be conducted in‑house, and that they are reviewing all braze process specifications and other brazed components manufactured by the external supplier.

While the crew were faced with an unfortunate situation, this accident highlighted the benefits of using time to your advantage. The crew took the time to formulate a strategy for the landing, assigned responsibilities to each crew member, and then rehearsed the plan. This ensured that they were well prepared and ended in a safe outcome.

 Aviation Short investigation Bulletin Issue 21

On 29 March 2013, at about 1000 Eastern Daylight-saving Time, a Piper PA-30 aircraft, registered VH-HPR (HPR), departed Bankstown Airport for Griffith Airport on a private flight. On board were the pilot and two passengers.

Following the take-off, the pilot selected the landing gear up. Passing through 400 ft, the tower advised that the landing gear was still down. The pilot responded that he would continue with the departure and hold at 2,000 ft to troubleshoot the problem. 

At 2,000 ft, the pilot engaged the autopilot and confirmed that the gear was selected up, but the gear down and locked light remained illuminated. The pilot checked the circuit breakers and could not see any that had tripped. The pilot then cycled the gear a number of times, however, the gear did not retract and the gear down and locked light remained illuminated. 

The pilot elected to return to Bankstown and was cleared for a straight in approach. On short finals, the tower advised HPR to ‘check wheels’, the pilot confirmed that the green down and locked light was still illuminated and that the gear selector was in the down position.

HPR touched down on the main wheels followed by the nose wheel, which collapsed when it contacted the ground, followed by the left main wheel and right main wheel. The pilot and passengers exited the aircraft without injury and the aircraft sustained substantial damage. 

Inspection of the aircraft by a licenced maintenance organisation was arranged by the insurer. The landing gear mechanism was visually inspected, and the worm drive was almost to the full retraction position, indicating the gear was retracted electrically.

The reason for this electrical retraction despite the gear selector being in the down position was not determined.

Aviation Short Investigation Bulletin Issue 20

On 27 March 2013, a Raytheon B200, registered VH-ZCO, was being operated on an aero-medical flight from Darwin to Port Keats, Northern Territory. On board the aircraft were the pilot and two flight nurses.

In preparation for landing at Port Keats the pilot selected the gear down. The left and right main landing gear down indication lights did not illuminate, while the nose landing gear down indication light (green) illuminated. The pilot elected to return to Darwin and advised air traffic control.

The pilot reported that on landing, the right main landing gear wheel touched down first and when the left landing gear wheel touched down the pilot felt the left side of the aircraft start to sink. The pilot shut down the left engine and feathered the left propeller, then shut down the right engine and feathered the right propeller. The left wing then contacted the runway, and the aircraft skidded to a stop, at about 1551. The pilot and flight nurses evacuated the aircraft via the overwing exit. The aircraft sustained minor damage, while the pilot and flight nurses were not injured.

The operator determined that during the last overhaul of the left main landing gear, a washer was not installed, which resulted in the landing gear contacting the aircraft structure preventing the landing gear from locking in the down and locked position.

The Civil Aviation Safety Authority (CASA) conducted an investigation into the accident and found that there was no conclusive way to determine when the washer installation error occurred. CASA also established that this error was an isolated event.

The manufacturer was informed of the accident and determined that the missing washer would not have led to the failure of the landing gear to lock down. They believed that it was more likely that the drag brace was not installed or rigged correctly when installed on ZCO or that another landing gear assembly or maintenance error occurred, causing the circuit breaker to trip, resulting in the accident.

As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:

• A medical bag that was located near the overwing emergency exit was relocated.
• All B200 aircraft were inspected. The main landing gear on one aircraft was found not to be correctly assembled and this was rectified before further flight.
• A safety bulletin was issued to all staff to inform them of the accident.
• The training and checking department were to review the part within the proficiency check about this type of landing and ensure it is reiterated at the next base check.

Aviation Short investigation Bulletin Issue 22

On 7 January 2013 at 0900 Eastern Daylight-saving Time a Piper PA28, registered VH-JXR, departed Mangalore Airport, Victoria on a navigation training exercise. The student pilot was the only person on board. 

An instructor on the ground watched the aircraft depart and observed an object trailing behind the aircraft following the take-off. During a low-level pass, the right main wheel and inner cylinder of the oleo assembly were observed to have detached from the upper cylinder and to be hanging off the brake line. After a second low level pass, it was observed that the wheel had completely detached.

The instructor advised the student to hold over the airfield to burn off fuel and allow time for a plan to be formulated. After several hours and with emergency services in attendance the student was instructed to make a normal approach to runway 36. The aircraft touched down on the runway and slid off to the side coming to rest on the grass. The student was uninjured; however, the aircraft was substantially damaged.     

The examination of the right landing gear assembly revealed that the lower torque link attachment bolt had fractured allowing the inner cylinder to become detached from the torque link and to fall from the outer cylinder when the aircraft became airborne. The examination indicated that the failure of the bolt was due to single-point bending fatigue due to asymmetrical loading i.e. bending from one side.

Since this incident, the aircraft operator has undertaken to replace all torque link attachment bolts during the next scheduled maintenance on any Piper PA-28 aircraft they operate. The operator also advised that they will be treating all landings where a sideways load may have occurred with caution.

Aviation Short Investigation Bulletin Issue 20

What happened

On 15 February 2012, a Toll Aviation Pty Ltd Fairchild Industries Inc SA227 Metro III aircraft, registered VH-UZA, was being operated on a post-maintenance acceptance flight in the circuit at Brisbane Airport, Queensland with two crew on board. On selection of the landing gear handle to the down position, the landing gear would not extend. After unsuccessful attempts to extend the landing gear in both normal and emergency gear extension modes, the crew decided to conduct a wheels-up landing. At about 0230 Eastern Standard Time the aircraft landed along the centreline of runway 19. The crew evacuated without injury and the aircraft sustained substantial damage.

What the ATSB found

The ATSB found that an electrical wire to the landing gear selector valve had separated at a connector adjacent to its terminal preventing normal operation of the landing gear to the down position. The investigation also identified an out of rig condition in the landing gear emergency extension system, which prevented correct operation of that system. Factors including the maintenance practices by a number of personnel and inconsistent maintenance documentation contributed to the existence of the defects.

What's been done as a result

The aircraft manufacturer advised that, as a result of this occurrence, re-routing requirements for the landing gear selector valve electrical wiring loom in the Metro aircraft have been distributed to all Metro operators through a Metro Global advisory publication.

The operator carried out a fleet-wide check of the landing gear on its Metro aircraft and rectified any defects found. The operator also re-routed the electrical wiring loom to the landing gear selector valve. In addition, the operator amended the pilot’s quick reference handbook and the Metro phase inspection worksheets and issued an engineering memorandum to all aircraft maintenance personnel detailing the operator’s requirements with regards to following standard procedures and approved data for maintenance tasks.

Safety message

This investigation highlights the importance of operators and approved maintenance organisations having a detailed understanding of the systems installed on the aircraft types that they are authorised to certify and aircraft manufacturers providing clear and concise maintenance procedures in an aircraft’s suite of manuals.

Following landing at Sydney Airport on the 8 Nov 2011, one of the main wheels of a Virgin Australia Boeing 737-8FE, registered VH-VUF, was found to have separated at the hub. The failure was traced to fatigue cracks emanating from an unpeened area of the inner hub's bearing bore. The operator had complied with the manufacturer's wheel inspection requirements. However, as a result of the occurrence, the operator increased the frequency of the ultrasonic inspection of the wheel hubs.

Aviation Short Investigation Bulletin - Issue 11

The Australian Transport Safety Bureau (ATSB) has completed its download and replay of the cockpit voice recorder (CVR) from a Bombardier DHC-8-311 aircraft, registered ZK-NEQ. The work was conducted on behalf of the Transport Accident Investigation Commission (TAIC) of New Zealand, in support of their investigation into the failure of the aircraft's nose landing gear, and subsequent diversion to Woodbourne Aerodrome, New Zealand, on 09 February 2011.

The TAIC is responsible for investigating this occurrence and requested assistance from the ATSB to download and replay the CVR. To facilitate the ATSB's involvement, an accredited representative was appointed to the investigation, in accordance with clause 5.23 of Annex 13 to the Convention on International Civil Aviation.

To protect the CVR audio and other information supplied by the TAIC, the ATSB initiated an investigation under the Transport Safety Investigation Act 2003. The CVR was downloaded at the ATSB's technical facilities in Canberra and a copy of the recovered audio was provided to the TAIC on 16 February 2011. A download and replay of a CVR fitted to ZK-NEZ was also carried out at the ATSB on 16 Mar 2011 to assist the investigation.

The TAIC is responsible for releasing a final investigation report regarding this occurrence.

Contact details for the TAIC are available at www.taic.org.nz

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Released in accordance with section 25 of the Transport Safety Investigation Act 2003.

The Australian Transport Safety Bureau (ATSB) has completed its download and replay of the cockpit voice recorder (CVR) from a Bombardier DHC-8-300 aircraft, registered ZK-NEB. The work was conducted on behalf of the Transport Accident Investigation Commission (TAIC) of New Zealand, in support of their investigation into the collapse of the aircraft's nose landing gear during landing at Blenheim Aerodrome, New Zealand, on 30 September 2010.

The TAIC is responsible for investigating this occurrence and requested assistance from the ATSB to download and replay the CVR. To facilitate the ATSB's involvement, an accredited representative was appointed to the investigation, in accordance with clause 5.23 of Annex 13 to the Convention on International Civil Aviation.

To protect the CVR audio and other information supplied by the TAIC to the ATSB, the ATSB initiated an investigation under the Transport Safety Investigation Act 2003. The CVR was downloaded at the ATSB's technical facilities in Canberra and a copy of the recovered audio was provided to the TAIC on 7 October 2010.

The TAIC is responsible for releasing a final investigation report regarding this occurrence.

Contact details for the TAIC are available at www.taic.org.nz

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Released in accordance with section 25 of the Transport Safety Investigation Act 2003.

On 16 July 2009 the pilot of a Beechcraft King Air C90 aircraft, registered VH-TAM, departed Perth Airport on a flight to Wiluna, Western Australia with one passenger on board.

Sometime after becoming established at flight level (FL) 210, the pilot became affected by hypoxia, which resulted in him becoming fixated on the 'distance-to-run' figures on the aircraft's Global Positioning System equipment display and incorrectly interpreting those figures as the aircraft's 'groundspeed'. That confusion resulted in the pilot interpreting the lower-than-expected figures as a significant headwind and in him descending the aircraft to escape the winds. Once established at FL150 for a significant period of time, he realised that that he had been affected by hypoxia. The pilot descended further before landing at his destination.

The investigation identified problems with the aircraft's left landing gear squat switch that prevented the aircraft from pressurising in flight. In addition, the cabin altitude warning system was non‑operational due to the incorrect connection of the switch wiring during previous maintenance.

Following this occurrence, the aircraft manufacturer changed the aircraft type's maintenance manuals and documentation and the Civil Aviation Safety Authority (CASA) issued a letter to owners and operators of Australian-registered pressurised aircraft that proposed mandating the fitment of aural cabin pressure warning systems in those aircraft. As a result of that industry consultation, CASA determined that a uniquely Australian installation requirement could not be justified.

Notwithstanding, as a result of the ongoing risk of serious incidents and fatal accidents in which the occupants of single-pilot, turbine‑powered, pressurised aircraft have been affected by, or have succumbed to unrecognised hypoxia in an unpressurised cabin, the Australian Transport Safety Bureau has issued a safety advisory notice. That notice encourages all operators of such aircraft to consider the installation of an aural cabin altitude pressure warning system that operates separately to their aircraft's visual warning system.

Following landing at Melbourne Aerodrome on 20 October 2009, the crew of a Boeing 737-8FE aircraft, registered VH-VUI, reported that the aircraft was difficult to taxi, requiring more power and steering input than usual. A subsequent visual inspection revealed the number 4 wheel to be oriented at an angle with respect to the axle and, following disassembly, it was discovered that the inner wheel hub and bearing mount had broken away from the wheel assembly.

Examination of the wheel revealed that the inner hub had failed from fatigue cracking that had initiated in the area adjacent to the bearing cup.

Fatigue cracking of the inboard bearing cup bore was an emerging issue for the 737 wheel type at the time of the failure. In May 2009, the wheel manufacturer issued a temporary revision to the Standard Practices Manual, with an updated inspection method for the susceptible area, and the aircraft manufacturer had issued a service letter in August 2009 with a periodic inspection requirement. The operator was in the process of reviewing and incorporating the changes into their own maintenance schedules at the time of the incident.

Immediately following the occurrence, the operator performed a fleet-wide examination, identifying those wheels potentially at risk of a similar failure. Subsequently, ten wheels were removed from service for immediate inspection. The operator also implemented an ultrasonic inspection program for wheels with over 4,000 cycles at every tyre change.

The manufacturers of both the aircraft and the wheel released updated information to operators and maintainers in early 2010, which included a revision to the recommended inspection interval.