Cessna Aircraft Company 172F, VH-ECT

As a result of this investigation, the Australian Transport
Safety Bureau simultaneously issues the following Safety Advisory
Notices:

SAN 200100223

The Civil Aviation Safety Authority note the safety deficiency
identified in this report relating to single-engine Cessna aircraft
seat stops and, as a matter of some urgency, alert aircraft owners,
aircraft maintenance engineers and pilots to the potentially
dangerous consequences of using other than the specified seat stops
and to the importance of correctly locating those seat stops and
ensuring that the seat pin securely engages a locating hole on the
rail.

SAN 200100224

The Aircraft Owners and Pilots Association of Australia note the
safety deficiency identified in this report relating to
single-engine Cessna aircraft seat stops and consider communicating
through the association's journal the potentially dangerous
consequences described in this occurrence.

SAN200100225

The Australian Licenced Aircraft Engineers Association note the
safety deficiency identified in this report relating to
single-engine Cessna aircraft seat stops and consider communicating
through the association's newsletter the potentially dangerous
consequences described in this occurrence.

Flight instructors reported that the pilot had demonstrated his
ability to satisfactorily perform go-around manoeuvres in this
aircraft. Therefore it was unlikely that the out of trim elevator
forces experienced during the full flap go-around were beyond the
physical capability of the pilot.

The possibility of an inadequately secured seat sliding back
along the seat rails during the go-around was examined. The pin on
the unoccupied right front seat was bent, indicating that it was
properly engaged into the seat rail locating hole at impact.
However, neither the locking pin on the pilot's seat nor any of the
seat rail holes exhibited damage consistent with a properly engaged
locking pin. The full flap go-around required considerable forward
elevator control input by the pilot to counteract out of trim
forces. This would have transferred pressure to the seat backrest,
lifting the front of the seat and reducing pressure on the front of
the worn seat rail and locking pin. Acceleration forces and the
aircraft's nose high attitude may have allowed the locking pin to
ride up the chamfered front end of the rail, and the unrestrained
seat to move rearward to the aft seat stop.

During takeoff, as the pilot applied back elevator control
input, postural forces on the seat would have held the pin against
the end of the rail and secured the seat. This may explain why the
seat did not move rearward during takeoff.

The possibility of aircraft mishandling during the initial
stages of the go-around and the subsequent loss of control at a low
height above the ground cannot be discounted. However, the event as
described by witnesses, and confirmed by ground and flight tests,
was consistent with the pilot seat sliding back and denying the
pilot adequate control input to avoid an accident.

The pilot of a Cessna 172 was conducting a solo navigation
flight from Essendon with planned landings at Latrobe Valley and
Leongatha. At approximately 1030 EST the pilot broadcast on the
Latrobe Valley common traffic advisory frequency (CTAF) of 126.0
MHz his intention to make a full stop landing on runway 03.
Witnesses at the airfield heard the sound of engine power
increasing and saw the aircraft commence what appeared to be a
missed approach from about 100 ft on short final. They reported
that the aircraft entered a steep left climbing turn onto a
reciprocal heading with flaps fully extended. At an estimated
height of about 300 ft the wings were seen to roll level and the
aircraft, with a nose high attitude, "fishtailed". Then with the
engine noise unchanged, the aircraft pitched nose down and impacted
the ground adjacent to the runway. The pilot was fatally injured
and the aircraft was destroyed by impact forces. The reason for the
go-around was not determined.

Weather at the time of the accident was clear sky and unlimited
visibility with a light north easterly breeze. There was no other
aerodrome traffic.

Examination of the wreckage found no evidence to suggest that
the aircraft was not capable of normal operation. The ancillary
controls were configured for the approach; that is, flaps set to
approximately 40 degrees, elevator trim at a position corresponding
to the position for that flap setting, approach speed and power,
and carburettor heat ON.

Although there was wear to the rollers, seat rails and the
locating holes, the pilot seat locking mechanism was capable of
normal operation. The pilot seat stops were fitted to the inboard
rail and were of inverted "U"-shaped metal design. They were placed
over the rail and secured by a split pin that passed through a slot
in the rail. They were similar to seat stops used in many Cessna
aircraft.

An inspection of the Cessna 172 parts manual revealed that the
seat stop locations were specified differently, depending on
aircraft serial number. The stops specified in the parts manual
consisted of a flat metal section with a threaded hole in the
centre that passed through the slot in the seat rail and secured by
a screw inserted through the locating hole in the rail, and screwed
into the stop. The forward stop was secured through the most
forward slot in the rail and, unlike the specified part, was able
to lie forward over the front end of the rail. That installation
permitted the seat to be adjusted forward beyond the first locating
hole. Marks on the left seat rail indicated that the pin of the
pilot's seat might have been incorrectly secured forward of the end
of the seat rail. There would have been no indication to the
occupant of the seat that the locking mechanism had engaged in that
manner, or that the seat was not properly locked into position,
other than by close visual inspection.

The rear stop of the pilot's seat was located at a point 410 mm
forward of the door rear pillar. The seat of a similar aircraft was
set to a corresponding position and when seated at that distance
from the controls, a pilot of similar stature to the accident
pilot, was unable to reach the flap switch, carburettor heat or
elevator trim controls. That pilot was unable to apply any
significant forward elevator control and only by pulling back on
the control wheel was the pilot able to lean forward sufficiently
to reach the throttle in the fully open position.

Flight tests were conducted using a similar aircraft. The
aircraft was configured for an approach with a flap setting of 40
degrees and the aircraft trimmed to an approach speed of 60 kt.
After applying full power and then using limited elevator and full
aileron control inputs only, it was possible to fly a manoeuvre
similar to that described by witnesses.

The accident pilot held a Student Pilot Licence and was
appropriately qualified to undertake the flight. He held a valid
Class 2 medical. Instructors who had trained the pilot reported
that although his flying did not reflect the level of skill
commensurate with his flying experience, he had satisfactorily
demonstrated missed approach manoeuvres in the Cessna 172. They
reported that he was able to achieve full control input with the
seat adjusted well forward despite his short physical stature.