| Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation. |
What happened
The occurrence
On 24 November 2021, the pilot of a Cirrus SR22 aircraft conducted a business flight from Northern Peninsula to Darnley Island (Erub), Queensland, with one passenger on board. The flight was conducted under the visual flight rules[1] and in visual meteorological conditions.[2]
At 0913 local time, the aircraft joined the downwind leg of the circuit for runway 10 at Darnley Island. The pilot reported conducting a stabilised approach. Once aligned with the runway, the pilot reduced the airspeed to about 3 kt slower than normal, to compensate for encountering less headwind than anticipated.
The aircraft landed long and ballooned,[3] touching down about 100 m beyond the runway threshold. The pilot initially assessed that there was still sufficient runway remaining to stop. However, when the nose wheel contacted the runway, it started to ‘wobble’. In response, the pilot pulled back on the elevator control to lift weight off the nose wheel and reduced pressure on the brakes. The pilot then realised the end of the runway was approaching and applied full braking, and the wheel wobble resumed.
The aircraft overran the runway and rolled down a steep embankment beyond the eastern threshold. The aircraft flipped over, coming to rest inverted (Figure 1). The pilot sustained minor injuries, and the passenger sustained serious injuries. Both were wearing the fitted four-point harness. The aircraft was substantially damaged.
Figure 1: Darnley Island aerodrome and accident site
Source: Babcock Aviation & Critical Services
Pilot qualifications and experience
The pilot was appropriately qualified for the flight and held a private pilot licence (aeroplane). The pilot’s aeronautical experience totalled nearly 5,000 hours, including about 1,600 hours in SR22 aircraft. The pilot had landed at Darnley Island 17 times previously, 5 of which were in the accident aircraft.
Darnley Island aerodrome
The runway on Darnley Island is 528 m long, 18 m wide, has a 2% slope down in the landing direction and lies 220 ft above mean sea level.
Airport reporting officer comments
The airport reporting officer (ARO) was at the aerodrome at the time of the accident and assisted in extricating the pilot and passenger from the aircraft. The ARO commented that there was no wind at the time and the windsock was drooping down. The ARO observed the aircraft touch down long and the nose wheel ‘wobbling all over the place’.
Nose wheel wobble
The pilot reported that the nose wheel wobble previously occurred on about 1 in 10 landings in the aircraft and had been investigated by aircraft maintainers. The recommended action in response to the wobble was to pull back on the elevator control and stop braking, then release back pressure and recommence braking. In this occurrence, the pilot performed those actions but in doing so, was distracted from initiating a go-around. The pilot also assessed that when braking heavily, the wobble had contributed to reduced braking effectiveness.
Pre-flight planning
Based on the area forecast, the pilot expected, and planned for, an easterly wind of 7–15 kt. The pilot calculated the aircraft’s weight and balance to be in the middle of the operating envelope. The aircraft landing distance charts did not specify a required runway length for the calculated landing weight, so the pilot used the closest (higher) available weight. Based on nil wind and a landing weight 226 kg heavier than the actual landing weight, the landing distance required was 378 m. This reduced to 340 m with a 15 kt headwind. Factoring in the 2% downslope increased the landing distance required to 524 m (with a 15 kt headwind). The pilot used this figure for planning, having assessed the wind would likely be stronger than forecast based on previous experience with the local conditions. The pilot therefore anticipated that with a stronger headwind and lighter landing weight than used for planning, there would be a safe margin between landing distance available and required.
Density altitude
The pilot reported the conditions at the time of the accident included an easterly wind of about 7 kt and visibility greater than 10 km. The nearest Bureau of Meteorology weather station was at Coconut (Poruma) Island, 89 km to the south-east, where the temperature at 0900 was 32 °C and the atmospheric pressure 1,009 hPa at sea level.
Assuming the conditions at Darnley Island were similar to Coconut Island, the pressure altitude at the aerodrome was about 340 ft above mean sea level and the density altitude about 2,380 ft. Effects of increased density altitude include increased landing roll distance and reduced performance in the event of a go-around.
Runway end safety areas for aircraft landing areas
Darnley Island aerodrome was uncertified and unregistered. Aerodromes that have not been approved to the regulated requirements are referred to as aircraft landing areas (ALA). An ALA is not required to comply with any aerodrome standards, and it is a pilot’s responsibility to determine the aerodrome’s suitability for the intended flight.
The Civil Aviation Safety Authority’s Civil Aviation Advisory Publication 92–1 Guidelines for aeroplane landing areas, provides guidance for pilots operating at ALAs and considerations for ALA owners regarding obstacle clearance proximal to the runway. The publication does not include guidelines regarding an overrun area beyond the runway ends. In this occurrence, the steep embankment at the eastern end of the runway increased the risk of aircraft damage and occupant injury in the event of a runway overrun. There was also an escarpment beyond the runway’s western end.
Previous accident
In 1993, a Piper PA-23 aircraft overran the western end of the runway at Darnley Island (ATSB investigation 199303915). The pilot initiated a ground loop to stop the aircraft falling down the 50 ft escarpment beyond the western end of the runway strip.
Safety message
Pre-flight preparation includes understanding the destination aerodrome and environmental conditions and establishing a plan to manage identified hazards. The United States Federal Aviation Administration’s Advisory Circular 91-79A Mitigating the risks of a runway overrun upon landing listed the following hazards associated with runway overruns:
- unstabilised approach
- high airport elevation or high-density altitude, resulting in increased groundspeed
- excessive airspeed or height over the runway threshold
- airplane landing weight
- landing beyond the touchdown point
- downhill runway slope
- delayed use of deceleration devices
- landing with a tailwind
- a wet or contaminated runway.
The circular recommends that once the actual landing distance is determined – taking into consideration the compound effects of multiple factors – a minimum 15% safety margin should be added.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
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- Visual flight rules (VFR): a set of regulations that permit a pilot to operate an aircraft only in weather conditions generally clear enough to allow the pilot to see where the aircraft is going.
- Visual Meteorological Conditions (VMC): an aviation flight category in which visual flight rules (VFR) flight is permitted – that is, conditions in which pilots have sufficient visibility to fly the aircraft while maintaining visual separation from terrain and other aircraft.
- Ballooning occurs when the pilot flares and the aircraft climbs instead of descending onto the