Forced/precautionary landing

The pilot reported that while flying at 4,000 ft, engine operation began to deteriorate. Initially this was manifested by intermittent coughing/missing but over the next few minutes RPM and power output decreased to the point where altitude could no longer be maintained. Engine instrument indications were all normal and throttle movement or carburettor heat application did not rectify the problem.

The engine finally lost all power, and the pilot was committed to a forced landing. The aircraft finally came to rest in a rough rock-strewn paddock, with substantial damage to the right main landing gear support structure.

A subsequent inspection of the engine revealed no internal faults that could have contributed to the power loss. However, the engineer who conducted the engine strip had been associated with the aircraft for a number of years. He said that the engine has no oil cooler and tends to overheat especially on hot days or with too lean a mixture. The carburettor/associated fuel lines are located such that when the engine does overheat, the system is highly susceptible to fuel vaporisation. In the absence of any other obvious reason for the failure, it was his opinion that the power loss was due to fuel vaporisation.

The tug pilot released the glider from tow shortly after take-off because the glider did not appear to be climbing. The tug pilot advised that he had lifted of at approximately 55 knots, allowed for drift, let the speed stabilise at 70 knots, then commenced to climb. After he had climbed to about 100 feet above the strip he noticed that the glider was very low behind him. He stated that he made a radio call to the glider telling him to "come up". He noticed the speed was deteriorating below 55 knots, he had full forward elevator applied and the stall warning had activated. The tug pilot considered that the glider was excessively out of station and that if the tow continued it would affect the safe operation of the tug. He therefore released the tow rope. The tug completed a circuit and landed safely.

The glider pilot stated that he selected negative flap during his preparation for launch. He stated that the tug commenced its tow and lifted off after a normal ground run. The glider was skipping and not lifting off. He moved the flap back two notches, looked at the airspeed indicator and it showed around 55 knots. He stated that the "tug went up like a rocket" and climbed well above the glider. He pulled back on the control column to try to catch up with the tug. Shortly after this he heard the tow rope release.

After being released he turned left, flew for a few hundred metres before turning right, and then outlanded into a small field covered in stubble. Once on the ground the glider ground looped in the stubble and slid backwards into a fence. The glider was substantially damaged.

After the accident the glider was found to be configured with the flaps in the "negative flap" setting. This setting is a feature that is used to reduce drag during high-speed cruise. The negative flap setting can also be used in the first segment of a take-off roll to increase the low-speed effectiveness of the ailerons. When this procedure is employed the flaps are reconfigured to the take-off setting as soon as the wings are levelled and under positive aileron control. The continued use of the negative flap setting during take-off and climb seriously degrades the climb performance of the glider.

The pilot was not able to explain to the investigator from the Gliding Federation of Australia (GFA) why the flaps were still selected to an inappropriate setting. 

There is no evidence of the flaps having moved as a function of the accident sequence therefore it can be concluded that the pilot did not apply landing flap during the approach into the stubble field. It is probable that the flap setting was not changed during the take-off run. This would explain the lack of climb performance experienced during the take-off sequence.

The balloon with 1 pilot and 10 passengers on board departed at about 0650 from Royal Park for a flight over Melbourne city. The pilot intended to land at Port Melbourne, a distance of approximately 7 kilometres. The pilot said that he was advised that at Essendon, 4 kilometres to the northwest the weather was overcast with a 1 knot northerly wind at 1000 feet and the surface wind was calm. After take-off the balloon climbed to 900 feet and the pilot estimated that he was drifting south at 2 knots. As the flight proceeded across the docks he noticed significant ripples on the water surface and significant movement of trees. He estimated that a surface wind of 10 knots had developed in his planned landing area. Because of the wind speed the pilot was forced to make a rapid descent and land before reaching the shore of Port Philip Bay. He force landed the balloon onto the third floor of a building under construction adjacent to the shoreline of the Bay. Although the balloon dragged across the concrete construction and skidded into a safety railing there was no injuries to the persons on board. The pilot disembarked 6 passengers and attempted to lift off and descend to ground level alongside the building.

During this manoeuvre the vent line snagged and the canopy started to deflate. As the canopy deflated it was ripped by construction materials resulting in the basket having to be manhandled to the ground. Weather station readings taken at 0300 indicated that the wind at 1,000 feet was from the northwest at 10 knots. Actual weather readings taken from automatic weather stations around Melbourne approximately 45 minutes prior to departure of the balloon showed the surface winds were generally from the north to northeast averaging 5 knots. By 0900 the surface winds had increased to 10 knots The pilot considered that the incident occurred because of an extremely rapid and localised katabatic wind had developed in the landing area. He plans to increase the volume of his balloon and to increase his fuel capacity to allow him to overfly Port Philip Bay should he experience increasing winds again. The police advised that this is not the first time that this operator has had problems landing in Port Melbourne. The balloon had landed on the same building site some weeks prior to this event, and in a previous event the balloon with passengers on board had overshot the landing area, flown out over the Bay, and was subsequently towed back to shore by a police vessel.

The pilot had underestimated the wind speed that he would encounter on this flight. Even though the surface winds were calm at Essendon and Royal Park, the actual wind at 1,000 feet was ten knots (as reported at 0300), and this, coupled with a surface wind of 5 knots increasing to 10 knots as the morning progressed, was not the ideal conditions to undertake a flight into an area characterised by very little open landing spaces adjacent to a large expanse of water. The operator's intention is to increase the flight endurance of the balloon and fly across the Bay. This would need careful consideration as some of the land areas at the south end of the Bay are narrow, and the flight path may put the balloon into the mouth of the Bay. It may be that a take-off more to the north of the city would preclude the need to consider an overwater flight.

The pilot was conducting a routine food and medical supply flight to several outstation settlements. Visual meteorological condition (VMC) existed when he departed, but with storm activity observed along the route, and a cyclone in the area. Approximately 1.5 minutes from the destination a rapid deterioration in the weather conditions to below VMC prevented the pilot from landing so he decided to divert to Oenpelli.

He was again confronted by deteriorating weather conditions making further diversions necessary. He notified Adelaide Flight Service of the diversions and then attempted to return to his departure aerodrome, which also proved impossible.

After spending sometime dodging around storms and heavy rain in an attempt to find a suitable airstrip, then faced with the approach of evening and fading daylight, he decided his safest action would be to find a suitable area for a precautionary landing. He was unable to re-establish contact with Adelaide Flight Service to advise his intentions.

He found a relatively flat area on top of an escarpment, but during the landing roll the aircraft struck light timber causing the right wing to detach and the aircraft to roll onto its right side. The pilot and passenger evacuated the aircraft, then activated the ELT which was monitored by Airservices Australia SAR via satellite, and their location known. Because of the cyclone and adverse weather conditions a search could not be initiated until the next morning.

They spent the night in the aircraft to shelter from continuous heavy rain, then rescued next morning by helicopter.

The aircraft departed Parkes on a VFR flight to Coffs Harbour, tracking via Scone, Mount Seaview and Kempsey. The pilot reported that the weather enroute to Scone had been fine with clear skies and winds from the south at 10 kts, however, active storms were observed developing to the south of the intended track.

Shortly after the aircraft passed over Mount Seaview, the pilot assessed that the weather was unsuitable to continue flight on his planned track. He decided to follow the Macleay River valley to Kempsey, then continue coastal to Coffs Harbour.  However, about 5 NM before Kempsey the weather deteriorated rapidly, forcing the pilot to divert in order to remain in visual meteorological conditions.

An area of high ground, which he had overflown some minutes earlier, was chosen for a landing. The pilot made two precautionary passes over the area and believed that the surface was approximately level. He then approached to land toward the south but discovered upon landing that the surface had a considerable downslope. While attempting to stop the aircraft the wheels locked under braking and skidded on wet ground. The right main landing gear collided with a creek bank, slewing the aircraft at right angles to the landing direction, and resulting in substantial damage.

A visiting pilot was being trained on the motorised glider over a number of days. During this flight the pilot and his instructor intended conducting several circuits. On the climb out after the second touch and go, the engine stopped at 250 to 300 ft above ground level. The instructor took over and elected to land on a cross runway that was situated behind the aircraft, as the terrain off the end of the strip in use was not suitable for a landing. This decision required that he conduct a 180 degree turn to the left, followed by an 80 degree turn to the right, to align with the runway. The second turn was conducted at a low height, and required all the pilot's concentration. He then realised that the aircraft was lined up on the paddock next to the aerodrome. During the landing roll the aircraft struck a ditch and the landing gear was torn off.

The pilot reported that the engine stopped because the aircraft had run out of fuel. He had logged the fuel state but did not check the log prior to this flight. He had forgotten about flying conducted about two days earlier, during which the engine was used extensively. The clear plastic tube fuel gauge was reported to be inaccurate as it often became blocked at the bottom of the tank.

A portable emergency locator transmitter was carried behind the seats but it was not turned on.

Post-accident engine testing indicated the engine should have been capable of normal operation. Inspection disclosed that the internal wall of the air intake duct, located between the filter and the engine, had collapsed restricting airflow to the engine. The restriction in airflow probably led to the reduction in power reported by the pilot. The ducting consisted of an inner and outer cloth-wall sandwich supported by a wire spiral located between the walls. The duct was also bound with string on the outside. The walls were bonded together on either side of the wire. Some of the bonding between the inner and outer walls had delaminated allowing the inner wall to collapse. The ducting did not have the airframe manufacturer’s part number and was a different type to that approved by the aircraft manufacturer.

The ducting fitted was Aeroduct SCEET 16, a duct that is often used in aircraft systems such as air conditioning, but not for negative pressure applications. The manufacturer approved ducting consists of Aeroduct SCAT 16, a heavy-duty ducting suitable for engine intake applications.

The aircraft had been engaged in low level survey work in very hot conditions. It is probable this led to a deterioration in the bond between the duct walls. On the day of the accident the partially clogged air filter probably increased the negative pressure in the intake duct sufficiently to cause the delaminating inner cloth liner to partially detach and block off the intake airflow. The weakened inner duct wall probably detached before the negative duct pressure reached a level sufficient to open the alternate air door. From that point on the emergency landing was inevitable. If the correct SCAT 16 ducting had been fitted it should have prevented the occurrence. The fitment of incorrect ducting was brought to the attention of the maintenance organisation that carried out the work and the regulatory authority.

The pilot reported that the aircraft was cruising at 7000 feet, when he heard a loud bang accompanied by severe vibration. He immediately transmitted a "Mayday". During a subsequent orbit, clear of cloud, the pilot saw a paddock with a likely landing strip. The throttle was closed and a glide approach commenced.

During the descent, the pilot noticed that the strip was obstructed with irrigation pipes. He then decided that the only viable alternative for a forced landing was on a nearby road. Vehicles were observed (headlights were on) travelling in the same direction and groups were widely spaced. During the landing roll (which was subsequently found to be downwind) the left wing struck a road speed sign at about 60 kts IAS.  The aircraft then slewed left off the road into a fence.

The pilot activated an Emergency Locator Transmitter which was fixed in the empennage. The transmissions were heard by the pilot of an overflying aircraft and reported to Brisbane Air Traffic Control.

The pilot later reported that the loss of power was due to a sudden failure of the No 3 cylinder barrel, occurring at the barrel to cylinder head shrink line.

During cruise flight at 5,500 ft, about 30 minutes after departure, the engine began to run roughly. The RPM dropped to about 1,700 with full throttle and the pilot was obliged to allow the aircraft to descend at about 400 feet per minute. The pilot was able to select a suitable section of a nearby road and carried out an uneventful landing. Initial investigation found oil leaking from one of the cylinders on the engine.

Later detailed examination found that a valve had failed in the no. 2 cylinder.

The aircraft was not fitted with an ELT.

FACTUAL INFORMATION

The aircraft departed Broome on a short-notice charter to transport seven passengers from Derby to Cadjebut. The flight to Derby was uneventful and the passengers were boarded for the trip to Cadjebut. Apart from a small amount of surging from the right engine after start, the start, taxi and line up were normal. The pilot assessed the surging to be the result of low RPM after start and noted that the surging disappeared as RPM increased. He saw no discrepancies during the magneto checks on taxi.

No problems were encountered in the take-off until about 150 ft above ground level, when the pilot assessed that the right engine had failed. The landing gear was already retracted and the pilot commenced emergency drills for an engine failure after takeoff. He stated that there was insufficient time to feather the propeller and that the aircraft did not climb. It eventually impacted the ground and slid to a stop over mud and through low mangrove bush.

The passengers and pilot evacuated the aircraft. After the pilot had notified Air Traffic Services that the aircraft had crashed, he made the aircraft safe, and he and the passengers walked to the airport.

An on-site inspection did not reveal any defects or circumstances which could have contributed to an engine power reduction or the subsequent landing on the mud flats. Impact marks on the ground from the propellers supported the contention that the right engine was not delivering the same power as the left engine. The strike marks indicated that the right engine RPM was approximately half that of the left engine at initial impact with the ground.

The right engine was transported to Perth where it was successfully ground-run on an engine rig. The engine was subsequently dismantled, and extensive tests were performed on components which could have contributed to the perception by the pilot and several of the passengers that the engine had failed or had significantly reduced its power output. These tests centred mainly on the turbocharging, electrics and the fuel systems. Anomalies were only discovered in the dual magneto. However, the anomalies could not be directly connected to the power reduction.

The reason for the power reduction thus remains undetermined.

The aircraft was at, or marginally over, the maximum weight for take off when the power reduction occurred. The density altitude when the pilot commenced his emergency drills was about 2,000 ft and the pilot had not been able to feather the right propeller before the aircraft impacted the ground. The pilot operating handbook performance data suggested that with the right propeller feathered, the aircraft may have been able to climb at a rate of about 180 ft/min under ideal circumstances. The handbook does not provide information on the effect of not having a feathered propeller on the inoperative engine.

Emergency locator transmitter

A NARCO ELT10 was fixed in the rear of the fuselage and was correctly armed. The ELT did not activate, probably due to low-impact forces on the mud flats. The beacon was not needed as the pilot made radio contact with a flight service officer and the crash was observed by another aircraft.

ANALYSIS

Studies have shown that the combination of high weight, high density altitude and added drag from an unfeathered propeller can all reduce the climb performance of a light twin-engined aircraft in the event of an engine failure. Results of some of these studies were publicised during the 1996/97 Civil Aviation Safety Authority Flight Forum Series and the results indicated that an unfeathered propeller could reduce the rate of climb on a representative PA 31 by between 100 and 200 ft/min. It therefore follows that this aircraft was unlikely to have been able to maintain a positive rate of climb if the engine completely failed.

Although it is not known to what extent the engine power was reduced, the propeller marks indicate an RPM reduction in the order of 50% from take-off RPM, which suggests a substantial loss of useful power and possibly a windmilling propeller. This, and the performance data above, would probably explain the inability of this aircraft to climb away.