Aviation safety investigations & reports

Pitts Aviation Enterprises S-1E, VH-SIS

Investigation number:
Status: Completed
Investigation completed


Sequence of events

The pilot of a Pitts aerobatic aircraft arranged to fly to a training area to the south of Archerfield in company with a friend in a Yak aerobatic aircraft. They planned to practise aerobatics for about 30 minutes. The area selected was over a pine forest with a duplicated high-tension power line traversing the forest. North of the power lines the trees had been cleared and grass to about 500 mm high was the only significant vegetation in the area. The terrain was gently sloping up towards the north-west. The pilots agreed to operate on either side of the power line with the Pitts operating to the north of the line.

When the pilot of the Yak aircraft completed his sequence he attempted, unsuccessfully, to contact the Pitts pilot by radio. He also could not see the aircraft. When he flew closer to the power line he observed a small fire and realised that the Pitts aircraft had crashed. The pilot then contacted the Archerfield Air Traffic Controller to alert emergency services.

A resident located north-east of the accident site had observed the Pitts aircraft flying manoeuvres parallel to the power line. During one manoeuvre conducted to the north-west and away from the observer, the aircraft appeared to be flying straight, with the wings vertical, as if in a manoeuvre known as a "knife-edge". The upper side of the fuselage was directed away from the power line. The aircraft appeared to be descending but the person was aware that the aircraft was moving away and thought that the apparent descent may have been an illusion. After a vertical climb and descent involving rolling manoeuvres, the aircraft again flew in a straight line with the wings vertical. On that occasion the aircraft was tracking to the south-east and toward the observer, and the upper fuselage was again oriented away from the power line. The observer stated that the aircraft appeared to be descending, and passed from sight behind a low ridge. He did not see the aircraft again and some time later saw smoke rising from behind the ridge.

Aircraft examination

The aircraft impacted the ground in a wings-level attitude at a speed estimated at more than 100 kts, while travelling in a north-westerly direction. At the time the aircraft was descending at about 30 deg nose down, and appeared to have been in balanced flight and at a low "g" loading. The impact was considered not survivable. The aircraft did not bounce, coming to an extremely rapid stop in the sandy soil. The fire would have broken out immediately, as a result of the ruptured fuel tank and disruption of the electrical system. The aircraft was destroyed by impact forces and the post-impact fire.

The engine was dissassembled and inspected. The crankshaft had moved rearward by about 6 mm relative to the crankcase, a further indication of an abrupt stop. The lack of damage to the cylinders indicated that the propeller and crankshaft had taken most of the deceleration loads, transmitting them through the crankcase to the airframe. There was no indication of mechanical failure prior to impact. The available information suggested that the engine was operating at low to moderate power at impact.

The Pilot

The pilot held a private pilot's licence to fly aeroplanes. His Class Two medical certificate was valid until June 2001. He had commenced flying training in January 1983 and obtained an aerobatic rating in March 1995. The rating was progressively upgraded, and in November 2000 the pilot was approved to conduct aerobatics to a minimum height of 100 ft.

The pilot purchased the Pitts aircraft in September 1997 and had flown it almost exclusively since then. His most recent biennial flight review, which included aerobatic flying, was conducted in May 1999.

Although he normally flew without a parachute, on the accident flight the pilot was wearing a new parachute pack for the first time. The pack thickness was about 4 cm.

Weather conditions

At the time of the accident the sky was clear of cloud, and the wind was a light south-westerly. The pilot of the Yak aircraft assessed that the temperature was in the mid-thirties [Celsius]. The temperature and humidity at the accident site were considered by an experienced pilot to be such that conditions in the cockpit of the Pitts aircraft would have been oppressive.

Aerobatic manoeuvres

One of the manoeuvres the pilot was intending to practise was a "knife-edge" manoeuvre where the aircraft was flown straight and level while banked 90 degrees left or right. That manoeuvre was referred to as a stick-position manoeuvre, because the positioning of the control column and rudder pedals must be precise to place the aircraft in the correct attitude and flight path. Practice and familiarity are the primary means of ensuring accuracy.

In the immediate vicinity of the crash site there were no prominent visual indicators for the pilot to judge the height of the aircraft above the ground. The vegetation was low and devoid of trees, and the terrain was not sufficiently sloping to provide the pilot with good height cues.

Examination of terrain contours and the location of the observer indicated that the aircraft was probably below 30 ft above ground level at the time it was lost from sight behind a ridge.


Why the aircraft impacted the ground could not be determined.

It is possible that the air temperature and humidity affected the pilot's performance, however, the extent of any such affect could not be assessed.

The pilot's new parachute pack would have changed his position relative to the cockpit controls. A possible consequence was that, if the pilot used that relationship as a reference during manoeuvres, without adjusting for the parachute pack, the position of the flight control surfaces would also have changed when compared with previous flights performing the same manoeuvres. That could have resulted in the aircraft being operated outside the parameters previously established by the pilot for particular manoeuvres, such as by descending unintentionally.

Although the aircraft impacted the ground while tracking to the north-west, when the observer lost sight of it behind a ridge the aircraft was tracking in a south-easterly direction at a very low height. It is possible that the pilot discontinued the knife-edge manoeuvre and reversed the direction of flight while hidden from view by the ridge.

General details
Date: 28 January 2001   Investigation status: Completed  
Time: 0945 hours EST    
Location   (show map): Logan Village    
State: Queensland   Occurrence type: Collision with terrain  
Release date: 17 January 2002   Occurrence category: Accident  
Report status: Final   Highest injury level: Fatal  

Aircraft details

Aircraft details
Aircraft manufacturer Pitts Aviation Enterprises  
Aircraft model S-1  
Aircraft registration VH-SIS  
Serial number W69  
Type of operation Sports Aviation  
Damage to aircraft Destroyed  
Departure point Archerfield, QLD  
Departure time 0900 hours EST  
Destination Archerfield, QLD  
Crew details
Role Class of licence Hours on type Hours total
Pilot-in-Command Private 273.1 1073
  Crew Passenger Ground Total
Fatal: 1 0 0 1
Total: 1 0 0 1
Last update 13 May 2014