1991 RAAF Boeing 707 crash

The 1991 RAAF Boeing 707 crash occurred on 29 October 1991, resulting in the loss of the aircraft and all five crew members. The aircraft, serial number A20-103 with the callsign Windsor 380, was on a training flight involving a demonstration of the aircraft's handling characteristics at minimum control speeds in a "double asymmetic" condition, with two of its four engines at idle power. During the non-approved manoeuvre, the aircraft stalled and entered a spin before crashing into Bass Strait off Woodside Beach, Victoria. The subsequent inquiry highlighted serious deficiencies in the RAAF's documentation and training, as well as operational knowledge of the aircraft type. It was the first fatal accident of a swept-wing jet transport in the country and remains the largest aircraft to have crashed in Australia.

Background

On the morning of 29 October 1991, Windsor 380 was on a multi-leg training flight from RAAF Base Richmond to Avalon Airport on the outskirts of Melbourne. As the RAAF's only 707-rated Qualified Flying Instructor, Lewin was conducting conversion training to qualify Ellis, already a 707 captain, as an instructor on the aircraft type. Lewin's workload was further increased by the lasting effects of the 1989 Australian pilots' dispute, which resulted in many pilots leaving the Air Force for favourable pay and conditions in the airlines.

The training flight was intended to practice unusual situations that could not be achieved in a simulator due to limitations of software fidelity. This included asymmetric thrust conditions resulting from the loss of one or more engines at the same time. The flight departed Richmond at 1038 and proceeded normally to RAAF Base East Sale, where the pilots performed a touch-and-go landing with a simulated failed engine before continuing south towards the ocean at an altitude of 5000 ft.

Accident

Lewin briefed the next exercise, which would involve flying the aircraft at the minimum controllable airspeed (VMCA) with both engines on the left wing at idle thrust and without hydraulic assistance available to operate the flight controls. In this condition, aerodynamic loads on the rudder limited its travel to half of the normal deflection and required a very significant amount of force to be exerted on the rudder pedals by the pilot for a prolonged period to maintain control. In preparing for the manoeuvre, Ellis, the pilot under instruction, first turned off the rudder boost, configured the aircraft with flaps 25 and began reducing speed to VMCA.

The flight engineer and instructor both expressed surprise at the reduced effectiveness of the rudder with the hydraulic boost disabled, but there was no discussion of discontinuing the exercise. Instead, as the aircraft slowed to 148 knots, Ellis banked the aircraft to maintain heading, placing the aircraft into a sideslip, and increasing power on the right-hand engines. At this point, the cockpit voice recorder (CVR) indicated Ellis was struggling with the physical workload required to maintain control, followed by Lewin telling him to "wrestle with the beastie!"

Shortly after, the pilots began to discuss how to "get out of" the situation; at around this time, the sound of the stick shaker could be heard on the recording as the aircraft stalled and entered a spin. The aircraft, now descending close to vertically, completed two full revolutions as the crew successfully attempted to re-engage the hydraulic rudder boost, but there was insufficient altitude remaining to recover and the aircraft impacted the sea about 1 km from the shore.