Runway excursion

The pilot with three passengers intended operating the Warrior in the training area for about one and half hours. During the take-off roll, the pilot became concerned with the apparent lack of aircraft acceleration. Immediately after liftoff, the aircraft settled and, suspecting a reduction of power, the pilot closed the throttle. During the landing the aircraft overran the end of the runway sustaining minor damage. A subsequent engineering inspection found that the engine was capable of normal operation.

The pilot was making his first flight in the aircraft which he had just completed building. He was using runway 17 right and the wind was a light southerly of about five knots, tending to the southwest. He reported that he misjudged the first approach to land, so made a go-around. On the next attempt he touched down about halfway along the runway. There was plenty of runway remaining after landing so the pilot decided to let the aircraft run through to the end rather than to brake for a shorter turn off. At this stage the stick was full back.

Suddenly the aircraft started to veer to the left. The pilot said he was unable to correct the situation. The aircraft continued the swing and was almost sideways by the time it entered the grass on the left of the runway. The right main landing gear leg buckled in the soft ground and the right wing hit the ground.

The pilot diverted to Ballarat due to poor weather enroute. He noted smoke from a nearby chimney and estimated the wind was from 160 degrees. Runway 18 was selected for landing. On touchdown the aircraft bounced, touching down again near the right side of the runway. The pilot applied power to go around as the aircraft ran off the right side of the runway into a wet and boggy grass area. The aircraft did not become airborne. The nose leg collapsed on the soft surface and the aircraft quickly came to a stop.

Significant Factors

The following factors were considered relevant to the development of the accident:

1 The pilot probably misjudged the landing flare.

2 The pilot probably did not apply the appropriate technique to ensure that directional control was maintained during the attempted landing and go around sequence.

The pilot reported that the aircraft was landed off a normal full flap approach. The strip slopped down from the touchdown point. After lowering the nosewheel the pilot applied the brakes; however, they did not work, and the aircraft's speed did not reduce. He shouted to the passengers to brace themselves and, as the end of the strip was approaching rapidly, he attempted to steer the aircraft into a fence to bring it to a stop. There was insufficient room to complete a go-around. Shortly after turning the aircraft towards the fence the brakes operated, locking the main wheels. The pilot was unable to establish any further directional control, and the aircraft collided with a tree.

A post-accident inspection of the braking system did not disclose any reason for the brake problem.

The pilot stated that during the take-off run with both engines at full power, the aircraft veered to the left. At 40 kts the aircraft did not respond to full right rudder, so the pilot aborted the take-off. The aircraft came to rest in an adjoining cultivated paddock with the nosewheel broken off and both propellers damaged.

The right side of the strip was temporarily unavailable for take-off due to a glider with an unserviceability returning for a landing. A tug aircraft was parked off the left side of the strip. Following a discussion with the pilot of the parked tug a decision was made to take off on the left side of the strip. During the ground run the left wing dropped to the ground, the glider veered to the left and the wingtip struck the left main gear tyre of the parked tug. The glider was substantially damaged.

The pilot completed an airfield inspection prior to joining the circuit for landing. He noted from the movement of the trees that there was a crosswind from the right on runway 30 but he was unable to find the windsock to determine its strength. The pilot flew a normal crosswind approach, with the aircraft yawed into wind, selecting full flap (300) at a speed of 70 kts on short finals. He applied left rudder and right aileron, during the landing, to counter the crosswind. The aircraft bounced on touchdown and began to drift to the left. The application of full right aileron failed to stop the drift, and the pilot applied full power in an attempt to go-around. By this time the aircraft had left the runway and was heading towards a gravel mound. The aircraft appeared reluctant to get airborne and the pilot retracted the flaps to 200 in an attempt to improve performance. The aircraft collided with the gravel mound before it became airborne.

A video of the landing and accident indicated that a strong wind was blowing and that there were significant gusts. The aircraft was affected by one such gust as it touched down the first time and it was evident that the pilot was unable to counter its effect. There was insufficient room following the application of power for the aircraft to become airborne before it collided with the mound. The windsock had been shredded by strong winds and was unusable as an indication of wind strength. The pilot had completed crosswind refresher training on the weekend before the accident flight and had assessed the conditions as difficult but safe.

The student pilot, who had very limited flying experience, was on his third solo training circuit for the flight when the accident occurred. The aircraft was in the ground-run phase of a touch-and-go landing when it began to veer to the left. The pilot applied opposite rudder, in an attempt to correct the situation, with no apparent effect. Realising that the aircraft would run off the strip the pilot closed the throttle and applied the brakes. However, the aircraft ran into a ditch, damaging the propeller and nosewheel leg before it stopped moving. The student pilot had completed three successful dual circuits prior to commencing solo training.

Factual Information

Following landing gear retraction after take-off, the pressurization system failed to operate. The aircraft was flown to Darwin in an unpressurized mode, where a normal approach was made.

As the weight came on the wheels the right main gear collapsed. The wheel became jammed between the gear door and leg, which prevented it from rotating and caused the tyre to blow out. The aircraft then swung to the right through approximately 90 degrees, continued sideways off the bitumen runway edge and dropped 150 mm onto the flight strip, striking a runway light cement base with the main landing gear. It then turned through a further 90 degrees before coming to a stop, approximately 800 m from the threshold and 20 m to the right of the runway.

The right landing gear shock strut lower attachment cap had separated from the cylinder, probably just after take-off. The trailing arm and wheel assembly could then pivot freely, allowing the metering pin, nitrogen charge and hydraulic oil to escape from the cylinder. When the gear was retracted, the wheel, which was now hanging down, possibly fouled the squat-switch preventing cabin pressurization. Without the shock strut support between the leg and the trailing arm the wheel collapsed upward at landing.

When the aircraft ran off the runway and dropped onto the flight strip, it was subjected to a severe vertical load which caused the right wingtip top attachment rivets to shear and the right engine mount to distort.

Analysis

The shock strut cylinder threaded section had belled, indicating that the shock strut had been subjected to a high compression force, possibly by a heavy landing on a previous flight, but this could not be confirmed. The extent of belling was not ascertained due to grinding of the area to facilitate dismantling.

Partial stripping of the threads and separation of the now loosened cap from the cylinder occurred when a medium downward load was applied to the cap, such as when supporting the weight of the wheel assembly after take-off.

A thread locking compound was found to have been correctly used in the assembly of the shock strut lower attachment cap to the cylinder, and impressions in the compound indicated that the cap had been tight before the belling occurred.

The reason why the threaded section of the shock strut cylinder belled could not be positively established.

Safety Action

The Civil Aviation Safety Authority, Federal Airports Corporation and the Royal Australian Air Force recognised that a problem existed with the runway edges at Darwin Airport and have undertaken work to remedy the situation.

This work was completed in mid-November 1995, and it is reported that the runway edges and flight strip now meet the requirements of the rules and practices of aerodromes.

The instructor completed ten dual instructional circuits with the student pilot whom he assessed as competent for a first solo flight.

The instructor vacated the aircraft and observed the solo circuit from the ground. The take-off, circuit and final approach appeared normal until the flare, which appeared low, and the aircraft touched down earlier than expected. The pilot instinctively raised the nose causing the aircraft to balloon to about 1.5m above the runway.

The nose was then lowered and the aircraft touched down heavily on the nose wheel, bending the nose leg and allowing the propeller tips to strike the runway and destroy the nose wheel fairing. The aircraft settled back on its three wheels then veered left vacating the runway. The pilot shut the engine down and the aircraft stopped with no further damage or injury.