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.
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.
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.
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.