The pilot of the Piper PA 32-260 was conducting the return sector of a charter flight for five passengers from Rottnest Island to Jandakot, WA.
The pilot reported that a strong and gusty southerly wind was blowing almost directly across the runway, but favoured a departure from runway 27. He used the indications from the aerodrome's windsock to assess the wind strength and determined that it was within acceptable limits for his aircraft.
Shortly before 1600 WST, the pilot taxied the aircraft to the threshold of runway 27. The pilot reported that he used a conventional crosswind technique for the takeoff, with full aileron deflection into wind and use of rudder to maintain the aircraft on the runway centreline. The pilot reported that the airspeed indicator was reading about 65 - 70 kts when he positively rotated the aircraft nose for the initial climb. However, the aircraft did not respond to these control inputs and started drifting to the right. Despite applying full deflection of the rudder and aileron controls, the pilot reported that he was unable to maintain directional control of the aircraft.
The aircraft continued to diverge from the runway centreline, departing to the right of the runway strip and passing over a sealed taxiway and sandy scrub terrain. The right main landing gear collided with a tree stump on the edge of a shallow salt-water lake adjacent to the aerodrome. The aircraft briefly became airborne before coming to rest in the lake, in water that was less than 1 m deep. The pilot and passengers were not injured and vacated the aircraft without assistance. Although the aircraft was carrying an inflatable life jacket for each person on board, nobody was wearing one at the time of the accident and nor was this required by regulation.
Examination of the aircraft did not reveal any defect that could have affected its normal operation. Damage to the propeller blades was consistent with the engine operating at a high-power setting on impact with the water. Marks on the lower surface of the right wingtip were consistent with the tip of the right wing dragging across a hard sealed surface. The outboard portion of the right aileron also exhibited evidence of contact with a hard sealed surface.
The passengers recalled that the aircraft started to become airborne at a ground speed that seemed slower than the speed achieved during takeoff from Jandakot earlier that day. They also reported that the ground roll along the runway seemed shorter. One of the passengers also described seeing a flashing red light on the instrument panel during the takeoff attempt.
The pilot reported that following the accident he returned to the terminal building and was watching the aerodrome's windsock. During this period he reported that the wind direction occasionally seemed to favour a departure from runway 09.
Examination of the runway revealed marks that indicated the aircraft commenced diverging from the runway centreline approximately 270 m from the threshold of runway 27. The aircraft's ground track was evident as it departed the runway strip and crossed the sealed taxiway. The ground track included abrasion marks from the tip of the right wing and the trailing edge of the right aileron, together with the track of the right main wheel. The marks on the right wingtip indicated that the aircraft was in a sideslip at the time and the nose was displaced right of the actual track across the ground. The aircraft came to rest about 530 m from the runway threshold and 120 m to the right of the runway centreline.
The aerodrome forecast issued by the Bureau of Meteorology (BoM) and current at the time of the accident forecast a wind from 190 degrees true (T) at 25 kts. BoM also issued routine half-hourly weather reports of the recorded conditions at the Rottnest Island automatic weather station (AWS). The report issued at 1530 indicated that the wind was 190 degrees T at 30 kts, gusting to 38 kts. These conditions were consistent with other reports issued on the afternoon of the accident.
The AWS for Rottnest Island is situated approximately 2 NM to the west of the aerodrome, on higher terrain about 160 ft above the aerodrome elevation. The site for the AWS is an exposed part of the island, and consequently, the recorded wind speeds could be expected to exceed those that would be experienced at the aerodrome.
Information from the AWS was not broadcast on either a discrete very high frequency radio or the Rottnest Island non-directional beacon navigation aid. The half-hourly reports issued by BoM could be obtained by pilots during pre-flight briefing and on request in-flight from air traffic services' Flightwatch frequency.
Minute by minute data from the Rottnest Island AWS indicated that during the 5 minutes prior to the accident, the maximum recorded wind speed was 38 kts, minimum wind speed 25 kts, from directions between 181 and 198 degrees T.
The east-west orientation of the runway at Rottnest Island and a series of sand hills to the south of the runway can significantly influence operations at the aerodrome, particularly at times when strong southerly winds prevail. This can include the effects of low-level wind shear, low-level turbulence in the lee of the sand hills and other conditions due to the behaviour of strong winds as they flow over and around the terrain.
Climatology studies of Rottnest Island conducted by BoM indicate that the runway is not aligned with the prevailing winds, and consequently, pilots can expect to frequently encounter crosswind conditions when operating at the aerodrome. In general terms, the strongest southerly crosswind components are more prevalent during the afternoons of the summer months. Strong northerly crosswinds appear to be more prevalent during the afternoons of the winter months. Records indicate that the runway crosswind component regularly exceeds 20 kts.
The pilot reported that he did not obtain a weather forecast for the day of the accident, but had received an operational briefing by telephone from the company chief pilot, prior to departing Jandakot on the first flight of the day. This briefing had included information obtained by the chief pilot on the weather conditions forecast for the day. The pilot did not obtain additional information or update the briefing received from the chief pilot during the course of the day.
The investigation calculated that the aircraft's operating weight at the time of the accident was below the maximum permitted take-off weight, with the centre of gravity in the vicinity of the published aft limit.
Forces acting on the aircraft during the initial stages of its take-off roll would cause the nose to yaw to the left as engine power was applied. In addition to this effect, at low speed during a crosswind takeoff, the stability of the aircraft was such that the fuselage had the tendency to weathervane into wind. Control of the aircraft in those conditions required the application of a crosswind takeoff technique to safely control the aircraft. From the perspective of aircraft controllability, a crosswind from the left (as was the case for the accident flight) was the more significant. This was due to the tendency of the aircraft nose to yaw left due to the crosswind, combining with the tendency of the aircraft nose to yaw left due to the application of engine power. The tendency of the aircraft nose to yaw is counteracted by the pilot applying right rudder, with the required amount of rudder input generally reducing as the aircraft accelerates and the rudder becomes more effective. During the later stages of the take-off roll, some left rudder input may have been required to maintain the aircraft on the runway centreline.
The investigation could not positively determine the airspeed of the aircraft at the time the pilot attempted to rotate the aircraft's nose to initiate the climb from the runway.
The US Federal Aviation Administration approved flight manual for the PA32-260 indicates that the demonstrated takeoff or landing crosswind component is 20 miles per hour (17 kts). The Civil Aviation Safety Authority approved flight manual for the aircraft type stipulates a maximum permissible crosswind component of 20 kts.
The circumstances of the accident were consistent with the pilot being unable to maintain control of the aircraft, while attempting to takeoff in strong crosswind conditions. On the information available, these conditions were probably in excess of the stipulated crosswind limits for the aircraft. The damage to the trailing edge of the right aileron confirmed that the pilot had applied aileron into wind. However, that control deflection could not prevent the aircraft rolling to the right during the takeoff and the right wingtip struck the ground.
The difficulty experienced by the pilot in maintaining directional control could also have been influenced by the local effects of the strong wind flowing around the sand hills immediately to the south of the runway. The pilot had probably underestimated the strength of the wind when interpreting the aerodrome's windsock prior to deciding to attempt to takeoff, having determined that the crosswind was within the published limits for his aircraft.
The distance between the runway threshold and the point where the aircraft commenced to diverge from the runway centreline, the absence of a significant headwind component and the passenger recollections of a short ground roll and low ground speed were each consistent with the aircraft becoming airborne at a low speed. It was possible that the inability of the aircraft to climb clear of the ground was affected by the aircraft becoming airborne at a lower than normal airspeed, which also contributed to the reported ineffectiveness of the aircraft's flight controls. The passenger recollection of a red flashing light on the instrument panel was also consistent with activation of the stall warning light, which would have illuminated if the aircraft's nose was pitched up to initiate a climb and the airspeed was below about 60 - 65 kts.
The aerodrome forecasts issued by BoM generally described the observed conditions at Rottnest Island for the day of the accident. The forecasts predicted the existence of strong southerly winds during the afternoon, which exceeded the aircraft's maximum permitted crosswind component. The weather reports issued by the Bureau during the day were available to the pilot from a number of sources and could have assisted the pilot to assess the strength of the prevailing wind.
Pilots can expect to regularly encounter strong crosswinds during operations at Rottnest Island. During some months of the year the crosswind component will regularly exceed the stipulated crosswind limits of most light aircraft.
The decision by the pilot to attempt a takeoff was made without access to all available information, which included data from the Rottnest Island AWS. It was probable that the pilot would not have attempted to takeoff had he realised that the wind conditions were so extreme.
Strong crosswinds existed during the attempted takeoff, which on the information available had probably exceeded the maximum permitted crosswind limit for the aircraft type.
The aircraft encountered wind gusts and turbulence during the take-off roll and probably became airborne at an airspeed less than that required for safe flight.
The pilot continued the takeoff attempt without adequate control of the aircraft, and the aircraft did not attain the performance required to avoid collision with objects.
Safety Recommendation R20020232
The Australian Transport Safety Bureau recommends that the Rottnest Island aerodrome operator and the Bureau of Meteorology evaluate the feasibility of transmitting the one minute data from the Rottnest Island AWS on a discrete VHF radio frequency.
|Date:||08 December 2001||Investigation status:||Completed|
|Time:||1600 hours WST|
|Location:||Rottnest Island, Aero.|
|State:||Western Australia||Occurrence type:||Control - Other|
|Release date:||12 March 2003||Occurrence category:||Accident|
|Report status:||Final||Highest injury level:||None|
|Aircraft manufacturer||Piper Aircraft Corp|
|Type of operation||Charter|
|Damage to aircraft||Substantial|
|Departure point||Rottnest Island, WA|
|Departure time||1600 hours WST|
|Role||Class of licence||Hours on type||Hours total|