Aviation safety investigations & reports

Amateur built aircraft - Smythe Model S Sidewinder

Investigation number:
Status: Completed
Investigation completed


The homebuilt aircraft had been completed over a period of about 22 years and was in flying condition. The aircraft, known as the Smyth Model S Sidewinder, was designed in the USA in 1958. The designer was aiming to produce a sporting monoplane that was reasonably easy to build, easy to fly, stressed to 9g for aerobatics, and economical in operation. The first flight of this aircraft type was made on 21 February 1969 and it received the Outstanding Design Award at the 17th Experimental Aircraft Association Fly-in that year. Plans became available to amateur constructors and in 1973 the plans for the accident aircraft were purchased by the owner.

By 1978, the fuselage construction was well advanced and the initial inspection was carried out. The project proceeded slowly and in 1985 the owner moved from NSW to live in Qld. The aircraft was nearing completion in 1994 when the owner made an application to the then Civil Aviation Authority (CAA) to reserve the registration VH-LKV. The aircraft was a first of type in Australia, and the necessary certification processes were incomplete. At the time of the accident, the aircraft was unregistered and did not have a certificate of airworthiness or a permit to fly. However, the pilot on the accident flight had flown the aircraft some weeks earlier on its first flight.

It had not been the intention of the owner to fly the aircraft on the day of the accident. The pilot arrived at the aerodrome and found the owner and his friend working on the aircraft. After some discussion, the pilot suggested to the owner that they should take the aircraft for a flight. The owner initially declined the offer but the pilot persuaded him to accede to the suggestion. Subsequently, the pilot added 20 L of fuel to the main fuel tank, which had contained about 6 L of residual fuel. The pilot then assisted the owner and his friend to replace panels and cowling and to prepare the aircraft for flight.

The weather was fine with a light south-easterly wind. Witnesses observed the aircraft taking off from runway 06. After takeoff, the aircraft initially flew low down the runway with a tail-down attitude, and then began a shallow climb. A flight of about 30 minutes was conducted, during which the pilot demonstrated some of the handling characteristics to the owner. The pilot also carried out circuits and landings during this period. The aircraft was then landed and taxied back to the hangar. While the engine was running and the owner was getting out of the aircraft, the pilot motioned to the owner's friend to come over to the aircraft. The friend indicated to another person he was with at the time, that he did not wish to go flying as he would be late getting home. However, he boarded the aircraft and the pilot taxied out for another takeoff.

The aircraft became airborne, again from runway 06, and headed north-east for about 2 km before turning left and heading back towards the aerodrome. When the aircraft was over the aerodrome at about 1,000 ft, witnesses saw the aircraft descend in a shallow dive and then perform what appeared to be a steeply banked manoeuvre or barrel roll to the right. One witness said he remembered seeing the belly of the aircraft faced towards him. Another witness said the aircraft rolled completely over in what appeared to be a controlled manoeuvre. During this manoeuvre, a third witness heard the engine noise increase and then completely cease. The aircraft recovered to a level attitude but immediately flick-rolled to the left and adopted a steep nose-down attitude. The aircraft continued to flick-roll or spin and struck the ground. The aircraft was descending almost vertically at impact with a 30-degree nose-down attitude. There was no fire and the impact was not surviveable.

Aircraft particulars

This was the first aircraft of its type to be constructed in Australia. Another builder in WA had commenced construction of a Sidewinder at about the same time, but the project was not completed. The aircraft was powered by a Lycoming Model 0-290-D2B engine which had a take-off power rating of 140 h.p. at 2800 r.p.m. The aircraft was designed with a fixed tricycle landing gear but the subject aircraft had been fitted with retractable gear. The gear was not retracted on the accident flight because the alternate gear extension system was not operative. The main fuel tank had a capacity of 65 L. The two wing tanks each had a capacity of 49 L, and were empty on the accident flight. The fuel consumption quoted by the engine specifications was 6.5 US gal or 24.6 L/h for economical cruise. Fuel consumption for the pre-accident flights could not be determined but would have been significantly higher than the economical cruise consumption because of the nature of the flights.

The aircraft was fitted with fully functioning dual controls and side-by-side seating for two persons. The constructor's manual quoted a stalling speed of 48 kts and a maximum speed (Vne) of 174 kts. The flight characteristics of this aircraft were unknown as a flight test schedule had not been carried out. The empty weight of the aircraft was approximately 477.5 kg but a final weighing of the aircraft had not been carried out as was required for certification of type. The aircraft had been test flown in December 1996 by the accident pilot. After that flight, the pilot had expressed his dissatisfaction with the aircraft's stalling characteristics, and said that he would not fly it again. It was discovered that the aircraft had 26 L of fuel in the left wing tank and no fuel in the right tank. This may have affected the stalling characteristics.

Damage to aircraft

The aircraft impacted the ground whilst rotating to the right with a nose-down attitude of approximately 30 degrees. The cockpit area was destroyed by the impact. The engine was embedded in the ground to a depth of about 0.5 m. One propeller blade was sheared off and fragmented by impact. The fractured surface indicated no powered rotational movement at the time of impact. The remaining propeller blade was intact and undamaged. The cockpit structure and floor had been compressed forward against the rear of the engine. The force of impact against the rear of the engine had fractured the engine gear housing. The throttle was found in the fully open position, the mixture fully rich and carburettor heat control in the cold position. However, the position of the cockpit controls before impact could not be positively determined due to the extent of damage. The main fuselage fuel tank had disintegrated and there was no evidence of fuel at the accident site immediately after the accident.

Wreckage examination

Examination of the airframe did not reveal any failure or defect which might have contributed to the accident. The engine exhaust pipe was metallurgically tested and was at less than operating temperature at impact. The engine was bulk stripped and no defects or failures were discovered other than those caused by impact damage. The retractable landing gear was in the extended position at impact. During the investigation the possibility of propeller or spinner failure was considered, but there was no evidence to support this hypothesis. The possibility of a bird strike was also considered, but again there was no evidence found during the wreckage examination to support this theory.

Weight and balance

The aircraft had been weighed on 10 January 1994 to determine the empty weight and centre of gravity. A final weighing was required after fitting of the radio and other equipment but this had not been carried out. The actual weight and balance at the time of the accident could not be determined. However, based on the initial weight and balance determination, the aircraft was within the weight and balance envelope and the centre of gravity near the prescribed aft limit. The summary showed that with two persons on board and no fuel, the centre of gravity was 0.55 inches forward of the aft limit.

Personnel information

The pilot was the holder of a senior commercial pilot licence (aeroplane) and was qualified and endorsed on the aircraft category. He had flown the aircraft on one other occasion some three weeks before the accident, but otherwise had no experience on the particular aircraft type. He was, however, widely experienced with over 38 years as a flying instructor, airline pilot and general aviation pilot. He had previously test flown a home-built aircraft for the passenger on the accident flight. The passenger held a student pilot licence and had accumulated about 267 hours aeronautical experience.

Medical information

The pilot was medically fit and qualified to perform the flight. He had a current class one medical certification status. There was no evidence found to indicate that there were any physiological or medical factors which may have contributed to the accident. The passenger was medically fit and held a valid medical certificate for his licence category.

Meteorological conditions

Witnesses reported conditions at the time of the accident as fine with a light easterly breeze. There was an insignificant amount of high-level cloud and the temperature was 24 degrees C.


The aircraft was fitted with a VHF radio. The Caboolture aerodrome is outside controlled airspace but within the Caloundra/Redcliffe Common Traffic Avisory Frequency area. The frequency is used for inter-aircraft and advisory communication and is not recorded. There was no other known flying activity in the vicinity of Caboolture aerodrome at the time of the accident, and it is not known if there were any transmissions made from the aircraft immediately before the accident.

Aerodrome information

The Caboolture aerodrome is unlicensed. The grass runways are 06/24 and 12/30, and are 900 m and 1,350 m in length respectively. The aerodrome is 40 ft above sea level. The aircraft impacted the aerodrome on the southern side the runway 06 flight strip near the north-eastern end of the runway.


The investigation established that the aircraft performed a barrel roll or similar manoeuvre to the right, followed immediately by a series of flick rolls or a spin to the left. (A barrel roll is a manoeuvre where the nose of the aircraft is made to travel around a spiral path which is some distance from the axis of the roll. A flick roll is a manoeuvre where the aircraft is induced into a stall at a higher than normal speed and the aircraft rotates or rolls rapidly about its longitudinal axis. A spin is characterised by the same rotational movement but the axis of a spin is usually vertical.) The investigation could not establish any reason for the manoeuvre. During the course of the roll, the engine noise was heard to cease, and this was most probably due to fuel starvation. The investigation established that the centre of gravity may have been near the aft limit and this would have accentuated the uncontrolled manoeuvre and reduced the chances of recovery by the pilot. During the recovery from the rolling manoeuvre, the aircraft then stalled and rolled rapidly left two or three times before ground impact.

The engine was estimated to have been running for approximately 50 minutes before the accident. As a result, the fuel quantity remaining may have been insufficient to allow continued fuel supply to the engine when the aircraft was banked steeply, and may have caused the engine to cease operating due to fuel starvation.

Significant Factors

  1. The aircraft was flown before necessary certification processes were completed.
  2. The aircraft performed a barrel roll or similar manoeuvre for reasons undetermined, and the engine stopped during the manoeuvre.
  3. The engine stoppage was most probably due to fuel starvation.
  4. The pilot lost control of the aircraft and was unable to regain control before the aircraft struck the ground.
General details
Date: 07 January 1997   Investigation status: Completed  
Time: 1712 hours EST    
Location   (show map): Caboolture, (ALA)    
State: Queensland   Occurrence type: Fuel starvation  
Release date: 01 November 1998   Occurrence category: Accident  
Report status: Final   Highest injury level: Fatal  

Aircraft details

Aircraft details
Aircraft manufacturer Amateur built aircraft  
Aircraft model Sidewinder  
Damage to aircraft Destroyed  
Departure point Caboolture, QLD  
Departure time 1630 hours EST  
Destination Caboolture, QLD  
Crew details
Role Class of licence Hours on type Hours total
Pilot-in-Command ATPL 2.0 15500
  Crew Passenger Ground Total
Fatal: 1 1 0 2
Total: 1 1 0 2
Last update 13 May 2014