Bob Kells and his investigation team had arrived at the accident site by helicopter. It had been at least a day since the Twin Otter had struck trees nine kilometres south west of Simbai in the Bismark Ranges, Papua New Guinea, when the crew had tried to fly it out of a steep valley. It was an incredible sight. The fuselage was intact. The wings had been taken off by the trees. Ahead of it was a precipice -- a steep drop from which there may have been no survivors had the aircraft gone over. It was a unique situation. Bob had been able to interview the crew in hospital and they talked openly…

The pilot of a Sikorsky S76 helicopter was left with only lateral cyclic control when a loose screw lodged at the base of the cyclic stick. During transition from normal cruise flight to the approach to land the pilot found that the cyclic could not be moved aft. He also found that with any further forward movement of the cyclic stick it could not be moved aft of the new position. The pilot froze the cyclic longitudinal position and the helicopter stabilised in a level pitch attitude at about 85 knots indicated airspeed. Using only lateral cyclic movements to manoeuvre the helicopter, the…

One of the most dangerous situations a pilot operating under Visual Flight Rules (VFR) could be faced with is the complete loss of visual reference. In the last five years, 28 people have been fatally injured in such circumstances. VFR flight into IMC Year Occurrences Accidents Fatalities 1995 38 7 13 1996 34 1 2 1997 33 1 3 1998 39 4 3 1999 36 4 7 On 14 October last year, a VFR pilot with 220 hours flying experience set off from Lightning Ridge for Caloundra in a Cessna 182 in VFR weather. Although the weather forecasts looked reasonable when he took off, by the time he was…

The Avgas contamination event that happened over Christmas 1999 caught everyone by surprise. It had not been seriously considered as a potential hazard to aviation anywhere in the world, therefore the consequences had not been considered. The reasons behind why the fuel became contaminated were unexpected. Mike Watson, one of a team of transport safety investigators who had the task of sifting though an overwhelming amount of data and publishing the final report, gives some insight. No one was hurt as a result of contaminated aviation fuel, and there were no accidents that could be attributed…

In 1991 ATSB's predecessor (BASI) published a research report titled Limitations of the See-and-Avoid Principle. This report concluded that 'the see-and-avoid principle in the absence of traffic alerts is subject to serious limitations'. Unalerted see and avoid has a 'limited place as a last resort means of traffic separation at low closing speeds', and is 'completely unsuitable as a primary traffic separation method for scheduled services'. Nevertheless, operations in a number of types of airspace currently require the application of see-and-avoid techniques by the pilots of both visual…

ATSB's air safety investigator, Mike Watson, in his unique style, discusses the insidious dangers of carburettor icing. The aircraft was on short final for runway 29L when the pilot made a brief Mayday call. The aircraft was then observed to land in a car-yard, short of the runway. Both occupants managed to evacuate without injury. The pilot later reported that the engine did not respond when an increase in RPM was required, as the aircraft was undershooting the approach. The aircraft subsequently collided with a fence, short of the runway. Weather conditions at the time were conducive to…

In Australia, mountain waves are commonly experienced over and to the lee of mountain ranges in the south-east of the continent. They often appear in the strong westerly wind flows on the east coast in late winter and early spring. Mountain waves are a different phenomena to the mechanical turbulence found in the lee of mountain ranges, and can exist as a smooth undulating airflow or may contain clear air turbulence in the form of breaking waves and 'rotors'. Mountain waves are defined as 'severe' when the associated downdrafts exceed 600 ft/min and/or severe turbulence is observed or…

With the development of airborne collision avoidance systems (ACAS) and their fitment in aircraft since the mid-nineties it has become possible for pilots to know if their aircraft is on a collision course with another. When an ACAS warning is received the pilot or crew has time to take avoiding action. Some of the systems fitted in aircraft today will advise what to do - climb or descend away from a conflicting aircraft. Future developments will also give turn advice. The effectiveness of ACAS is totally dependent on the presence of an operating Mode C or Mode S (altitude encoding)…

The ATSB collects and analyses data from accidents and incidents involving aircrew, ground personnel and passenger safety. In this issue of the ATSB Supplement, a selection of Australian cabin safety occurrence briefs are summarised and one from the Transportation Safety Board of Canada. Photographs of the burnt out Saudi Arabian Airlines Lockheed Tristar at Riyadh on 19 August 1980 following an emergency landing. All 287 passengers and 14 crew on board died from smoke inhalation from a fire in the aft cargo hold which started shortly after takeoff. Despite the successful landing the crew…

There has been an aircraft accident. Debris from the wreckage is scattered throughout a 200-metre radius. Tragically, the aircrafts crew and its passengers have been fatally injured. The sound of sirens permeates the scene as police and ambulance services attend. Soon, media representatives arrive to speculate as to its causes with cameras poised to document the wreckage. That this could happen so suddenly and wreak such devastation strikes at the heart of many people. An occurrence like this is always associated with a sense of urgency to understand its underlying features. But aircraft…