The pilot reported that soon after take-off at a height of 150 to 200ft the engine spluttered and then stopped. The aircraft was landed on the remaining runway. The left main landing gear was torn off and the right wing was damaged during the landing. The cause of the engine stoppage was apparently caused by fuel flow interruption, however extensive post flight examination could find no fault with the engine or fuel system.

VH-OJD was cleared to track inbound via the 229 VOR radial on descent to 6,000 ft. The Approach South radar control sector controller (APP S) was processing the aircraft for landing on runway 16R. Due to operational requirements, the APP S controller delayed turning the aircraft onto a right downwind for that runway.

VH-OLN had departed runway 16R, cleared initially to climb to 5,000 ft. The Departures South radar control sector controller (DEP S) cleared the aircraft for an early right turn and an unrestricted climb to its planned cruising level.

The APP S controller was about to instruct the crew of VH-OJD to turn onto right downwind for runway 16R when he recognised that VH-OLN was climbing through 5,000 ft. In an attempt to maintain lateral separation, he instructed the crew of VH-OJD to turn left immediately and advised them of the traffic ahead to their right. At this time, the crew of VH-OJD advised that they were complying with a TCAS Resolution Advisory and climbing to 7,000 ft.

Recorded radar information indicated that the aircraft had closed to approximately 2.1 NM, with 400 ft vertical separation when the minimum separation should have been 3 NM or 1,000 ft vertically. Each had penetrated their respective airspace boundary buffer.

The runway 16 airspace agreement has a narrow corridor in the APP S airspace to the west of the airport. This airspace design limits the flexibility available to APP S when vectoring aircraft to downwind for runway 16. The latitude that DEP S may apply when vectoring departing aircraft onto south-westerly headings, and providing climb, is also restricted.

Separation was not ensured before VH-OLN was cleared for an unrestricted climb. The situation was worsened by the high rate of climb achieved by VH-OLN.

Findings

1. The unrestricted climb instruction provided to VH-OLN by the DEP S controller was premature.
2. The vectoring of VH-OJD onto right downwind for runway 16R by the APP S controller was initiated late.
3. The airspace agreement boundary for runway 16 operations restricted flexibility in the processing of both arrival and departure aircraft.

Factors

1. The radar surveillance techniques used by both controllers were inadequate to prevent the loss of the prescribed separation standards.

Safety action

As a result of occurrence 9503423, the Bureau of Air Safety Investigation made interim recommendation IR950212. As the interim recommendation is also applicable to this investigation, it is reproduced below.

IR950212

The Bureau of Air Safety Investigation recommends that Airservices Australia amend the runway 16 airspace agreement boundaries to ensure that arriving and departing aircraft cannot be on, or near, reciprocal tracks. The amendment should address excursions into either buffer area.

The pilot reported that shortly after departure from Jandakot the engine lost power and then stopped altogether. He attempted to carry out a forced landing in a grassed paddock, but the aircraft was damaged in the process.

An inspection of the aircraft's fuel system disclosed that the fuel filter, lines and carburettor were contaminated by a significant amount of rust-coloured water. However, no water was evident in fuel obtained from the drain points on either the main or auxiliary fuel tanks. The pilot reported that he had drained a significant amount of water from the main fuel tank prior to departure.

The main fuel tank was constructed of corrugated metal. The longitudinal corrugations were not connected to each other, and most were not connected to the single drain-sump. Water had collected in the corrugations, and some was still evident after the accident. The drain-sump was not located on the lowest part of the tank and undrainable water could accumulate in the tank, aft of the sump, with the aircraft in the ground attitude.

An experienced Tiger Moth engineer reported that inadequate fuel tank drain systems was a known problem, and an Airworthiness Directive (AD) had been issued which required that fuel-drain points, fitted to some aircraft types (including the Tiger Moth), be designed so that water could not be conveyed to the engine in any normal attitude for the aircraft. These drain points were usually fitted to the lowest point on the tank. That is, along the rear edge. The AD was withdrawn when a number of requirements, covered by several ADs, were incorporated into Civil Aviation Orders Part 100. Transfer of the fuel-drain requirements to the CAOs was incomplete because, whilst similar fuel-drain requirements exist for aircraft constructed in accordance with the amateur-built category of aircraft there is no longer any requirement to retrofit similar systems to existing aircraft, such as the Tiger Moth.

Two Tiger Moth fuel tank modifications, designed to meet the requirements of the AD before it was withdrawn, were available to overcome the lack of drainage found in this tank. Both incorporated drain points along the rear edge. Neither of these modifications had been incorporated in VH-HPH's fuel tank. It is probable that in-flight aircraft movement allowed some of the water that had collected in the corrugations, and at the rear of the tank, to make its way into the fuel system and cause the engine stoppage.

An inspection of the ground marks at the accident site indicated that the aircraft touched down whilst it was still in a sideslip to the left. Touchdown was followed by a partial ground-loop as the aircraft tipped up onto its nose and left upper wing. The aircraft was approaching a fence on touchdown. It is possible that the pilot used the sideslip manoeuvre in an attempt to lose height quickly and touchdown earlier but did not stop the sideslip in time for the landing.

An inspection of the lower left wing during the post-accident investigation disclosed that one spar had fractured some time prior to the accident. It was also evident that reconstruction of the wing, also carried out some time prior to the accident, was not in accordance with the manufacturer's specifications.

A Squirrel AS 350B helicopter, and a Jetranger 206B helicopter, were conducting scenic flights in the Sydney area on the afternoon of the occurrence. These flights usually passed over Middle Harbour but, because runway 25 was in use, they were cleared to track in company via the less familiar St Peters route. The Squirrel, being the faster of the two aircraft, flew in the lead.

Nearing the end of the flight, both aircraft were asked to hold for ten minutes at Rose Bay. Both pilots later said that they became concerned because it was almost at the end of daylight, and neither helicopter was certificated to undertake commercial night operations. After holding for about seven minutes the tower cleared both aircraft to track to Sydney Airport via St Peters and requested the pilots to expedite their return.

Whilst tracking inbound, the Jetranger began to fall behind the lead helicopter. The pilot of the Jetranger did not advise the tower, nor the pilot of the Squirrel, that he had fallen behind. As he approached to cross runway 25, the pilot of the Jetranger observed a fixed wing aircraft on final for that runway and slowed his helicopter because of wake turbulence concerns. The tower, on hearing the Squirrel report on the ground at Helipad H1 on the southern side of runway 25, assumed that the Jetranger was also about to land. At the same time a Sikorsky S-76A helicopter was inbound from the Harbour Bridge for Helipad H4, on the northern side of runway 25. A short time later the pilot of the Sikorsky reported that a Jetranger had passed in front of him from right to left, within a distance of about 150 ft, near Helipad H4.

All three pilots subsequently reported on the difficulties of sighting other aircraft against the city lights. Although the pilot of the Squirrel was aware of the proximity of the Sikorsky, the pilot of the Jetranger was not. Nor was the Sikorsky pilot aware of the proximity of the other two helicopters. The aerodrome controller did not see the Jetranger against the background of aircraft and city lights and was consequently unaware of the potential traffic confliction.

The pilot reported that he started the pre-landing checks as he joined the circuit and not on the downwind leg which is where he would normally start them. He selected full flap earlier than normal on the base leg and checked the throttle was at idle because the aircraft was not descending as quickly as he expected. He could not work out why. At no stage did the landing gear warning horn sound. After he flared the aircraft for the landing the propeller began to strike the runway, and the aircraft settled onto its fuselage. It slid to a stop to one side of the runway. The pilot indicated that he had forgotten to select the gear down prior to landing and had not noticed the lack of gear indications during his checks.

The pilot further advised that the gear warning horn had been reported as unserviceable on previous flights and although he had been told that it had been repaired it was apparently still unserviceable.

One factor often identified during inadvertent wheels-up accidents is the interruption of the pre-landing checks, usually because they have been started too early and the pilot is not ready to extend the gear when he gets to that item on the list. Universally recommended practice is to restart the checks from the beginning if they have been interrupted for any reason. The pilot in this accident reported that he had started his checks early and had stopped at the gear item.

The student pilot, operating under the remote supervision of an instructor had been conducting circuits in his own aircraft. Whilst conducting a glide approach, the pilot noticed that the aircraft was at a lower altitude than desirable and decided to delay extending the landing gear until late on the approach. The aircraft subsequently landed with the landing gear retracted.

According to the pilot and his instructor the 'gear unsafe' warning horn was not working at the time of the accident, nor had it worked during the endorsement. An engineer had told them that it was a permissible unserviceability. This information was subsequently found to have been incorrect.

The pilot reported that he had selected the landing gear down, and first stage of flap while on the downwind leg of the circuit but did not confirm the gear position during the pre-landing check either by observing the gear down lights or a visual check of the gear position through the window.

Full flap was selected on short final, and power reduced during the flare with the aircraft settling on the runway in a wheels up landing.

An investigation failed to find any problems with the landing gear or its system, and the pilot subsequently admitted that he had forgotten to lower the gear. The gear unsafe warning horn did not activate as the pilot had used a considerable amount of engine power throughout the final approach.

Witnesses reported that after the aircraft came to a stop the landing gear appeared to be partially extended, and the gear lever was in the down position. This gives the appearance that the pilot had realised his mistake too late and attempted to extend the gear just prior to touchdown.

The aircraft was being used to conduct parachuting operations from Hamilton Island. On this flight, an instructor was to carry out a tandem jump and another parachutist was to make a solo jump.

As the aircraft was climbing to altitude the pilot parachute on the instructor's rig opened. The pilot parachute was drawn out of the aircraft and the instructor managed to exit the aircraft and deploy his main parachute. He made a successful water landing. The solo parachutist jumped from the aircraft to render any necessary assistance to the instructor. The parachutist who was to jump in tandem with the instructor remained in the aircraft which was landed successfully at Hamilton Island.

Subsequent inspection of the aircraft found that the right stabiliser and elevator were bent upward, and the elevator horn balance torn off. 

The reason for the inadvertent deployment of the pilot parachute is unknown.

FACTUAL INFORMATION

Sequence of events

The crew reported that the flight had been normal and that the subsequent approach, which was flown by the co-pilot, was stable. The touchdown on runway 16R was smooth. The anti-skid and auto-spoiler systems were armed prior to touchdown. However, the ground spoilers did not automatically deploy but were manually raised by the pilot in command when the aircraft was about 150 metres beyond the touchdown point.

Coincident with the raising of the ground spoilers, the crew became aware of a thumping noise from the rear of the aircraft, and of the right wing beginning to drop. The aircraft deviated about 8 metres to the right of the runway centreline and was brought to a stop at the intersection of runways 16R and 07.

The aerodrome controller activated the crash alarm after observing excessive smoke from the right main landing gear and the shredding of the tyres. The airport RFFS attended the aircraft and confirmed that there was no fire and that the brakes were cold. The only heat present had been generated by the failed tyres. The engines were shut down and the APU was started to maintain the aircraft electrical system. After the pilot in command had confirmed that personnel were available to ensure their safety, the passengers were disembarked via the rear airstair.

On-site investigation

Inspection of the tyres and the tyre markings on the runway indicated that neither right main gear wheel rotated at touchdown. The right tyres produced heavy rubber skid marks from the touchdown point for about 120 metres, until the inboard tyre failed. The outboard tyre then failed about 20 metres further on. The aircraft travelled about 700 metres from the touchdown point. The complete tread section of the right inboard tyre had separated from the casing at some time subsequent to its failure.

Flaying tyre material had detached the landing gear outer door and damaged a trailing edge flap and flap fairing. Prior to touchdown the crew had not been aware of any abnormal technical indications. The wind was from 140 degrees, at 10 to 15 knots, gusting to 20 knots, and the runway was dry.

The aircraft was fitted with auto brakes. However, they were not used for this landing, as the operator's procedure when landing on runways such as 16R at Sydney was to use reverse thrust until the aircraft speed had reduced to below 60 knots. Normal braking would then be used.

Initial inspection of the right landing gear and braking system established that the wheels were able to rotate freely and that the fusible plugs in the wheels remained intact. Both failed tyres appeared to have been in serviceable condition prior to the landing. The inner tyre had accumulated 37 landings, while the outer tyre had accumulated four landings. The brake assemblies appeared to be serviceable.

Engineering examination

Subsequent detailed inspection of the aircraft systems found that with the anti-skid system activated and the right brake applied, the right inboard mainwheel locked. The fault was traced to switch No 480, which was found to be defective, and its mounting twisted. The switch was designed to provide locked wheel protection signalling for the anti-skid system, to ensure full brake release of the inboard pair of wheels at touchdown. The signal is cancelled when wheel speed of 60 mph is sensed, and the anti-skid system is then activated.

Locked wheel protection for the outboard wheel pair is provided by the landing gear accessory unit which is switched by the squat switch on the left main gear. This unit could not be faulted on ground test. Complete testing of the anti-skid system in accordance with the maintenance manual and recommendations from the manufacturer failed to detect any reason for lockup of the outboard brake. The failure of switch No 480 is consistent with inadequate lubrication of the control cable mechanism which activates the switch. Lack of lubrication can cause binding which may lead to disruption of the control. Similar problems with this mechanism have been reported by another operator.

Testing of the auto-spoiler system did not detect any defects. The system, when armed, will automatically deploy at touchdown when wheel rotational speed of 60 mph is sensed by a wheel on each landing gear, or after a time interval of 4 seconds after the squat switch on the left gear is sensed in ground mode. Although both wheels on the right landing gear were locked, the auto-spoilers would have deployed 4 seconds after ground mode was sensed, had the pilot not manually selected them.

The aircraft maintenance manual recommended replacement of the brake metering valve when tyre scuffing was evident. Consequently, the right brake metering valve was changed as a precaution. However, apart from this recommendation, the reason for the outboard tyre failure was not determined. Flight recorder information

The aircraft was fitted with a Sundstrand Universal Flight Data Recorder. Twelve parameters were recorded, including vertical and horizontal acceleration, pitch and roll attitude, magnetic heading, airspeed and engine pressure ratios.

Analysis of the recorded information confirmed that all parameters relevant to this occurrence were normal. The information indicated that a minor heading correction to the right was made immediately before touchdown.

Additional information

About two weeks after the aircraft had been returned to service, with the same flight crew and the co-pilot again handling the controls, the right outboard tyre failed during landing. The evidence indicated that there had not been wheel rotation at touchdown, and the tyre had skidded for about 120 metres before failure. Engineering inspection found that the landing gear lever UP switch No 781, which controls both inner and outer wheel pairs via the anti-skid system, was intermittently inoperative. The area in which the switch was located had been treated with a water dispersant type spray lubricant. This substance appeared to have adversely affected the operation of the switch.

The switch was changed, and the entire system then tested normally. The aircraft was returned to service, and no further incidents have been reported.

ANALYSIS

The initial occurrence was caused by the failure of the locked wheel protection circuitry for both the inboard and the outboard wheel pairs. Consequently, pressure applied to the right brakes during touchdown would have locked both right wheels.

The protection circuitry became inoperative when switch No 480 failed and an intermittent fault developed in switch No 781.

With the auto brakes disarmed, the brakes can only be applied by manual pressure on the brake pedal. It is possible that the handling pilot inadvertently applied right brake pressure when making the slight heading change which occurred immediately prior to touchdown.

The complete loss of the tread from the right inboard tyre may indicate that some rotation of the wheel occurred after the tyre failed.

The circumstances in which the right outer wheel was locked at touchdown when the second incident occurred, could not be fully substantiated. However, the section of switch No 781 which controls the locked wheel protection for the outboard wheel pair had malfunctioned.

CONCLUSIONS

Findings

1. Switch No 480 failed.
2. Switch No 781 malfunctioned intermittently.
3. There was no indication of a problem prior to the touchdown.
4. Immediately before touchdown there was a slight heading correction to the right.
5. The touchdown was smooth.
6. Neither right main landing gear wheel rotated at touchdown.

Significant factors

1. The main wheels' anti-lock systems protection did not function.
2. The right brakes may have been inadvertently applied at touchdown.

The Boeing 737 was tracking towards Sydney at about 250 kts, descending through 6000 ft, following a Boeing 747, when the crew of the 737 reported that they suddenly encountered wake turbulence. The aircraft abruptly rolled about 30 degrees to the left before the handling pilot was able to return the aircraft to straight and level. The crew advised ATC that they required greater separation from the 747.

No passengers were injured, however the purser cut her arm, and the second senior flight attendant grazed her knee, when they fell during the occurrence.

Subsequent investigation revealed that the 737 was 5.8 NM behind and 600 ft below the 747 at the time of the occurrence. The 737 had rolled 38.1 degrees to the left before the roll was stopped. The minimum longitudinal separation standard required for wake turbulence avoidance was 5 NM.