Introduction
This publication is the first in a pilot education series by the Australian Transport Safety Bureau (ATSB) on avoidable accidents. In this report, we will focus on accidents involving unnecessary and unauthorised low flying; that is, flying lower than 1,000 ft (for a populous area) or 500 ft (for any other area) above ground level without approval from the Civil Aviation Safety Authority (CASA).
Between 1999 and 2008, there were 147 fatal accidents reported to the ATSB involving aerial work, flying training, private, business, sport and recreational flying in Australia. Of those fatal accidents, at least six were associated with unauthorised and unnecessary low flying. Those six accidents, along with a seventh non-fatal accident, presented here as case studies, were chosen by aviation safety investigators at the ATSB to highlight the inherent dangers of unauthorised low flying and to offer some lessons learnt from each case. It is hoped that these lessons learnt will help pilots make more accurate risk assessments and better decisions before electing to fly at low levels.
Before you decide to conduct low-level flying, ask yourself whether there is a legitimate or operational reason for you to do so.
At low altitudes, there are many obstacles to avoid and there is a lower margin for error. Recognising the risks and hazards of low-level flying, CASA requires pilots to receive special training and endorsements before they can legally conduct low-level flying. In the accidents described in this booklet, most of the pilots had neither of these, and none had a legitimate reason to be flying below 500 ft. Some legitimate reasons for flying at low level include aerial stock mustering, crop spraying, and firefighting operations. For most private pilots, there is generally no reason to fly at low levels, except during take-off and landing, conducting a forced or precautionary landing, or to avoid adverse weather conditions.
What is sad and unfortunate about the accidents described in the following case studies is that they were all avoidable.
Read the ATSB research report.
Conclusion
These case studies serve as salient reminders of the risks associated with low-level flight. Out of the seven accidents documented in this report, only one had survivors. Low-level flying is inherently unsafe for a number of reasons, so it should be avoided at all costs when there is no operational reason to do it (regardless of whether you have been trained and/or approved to do so).
Flying at low level is unsafe because:
- there are more obstacles to avoid, many of which are hard to see until it is too late (e.g. powerlines and birds)
- pilots have a higher workload because there are more hazards to negotiate in the environment
- there may be turbulence and windshear that pilots do not encounter at higher levels and
- there is very little time to recover control of the aircraft if something goes wrong.
From the accidents described here, it is apparent that the two major hazards of low flying are wirestrikes and pilots’ reduced opportunity to recover their aircraft from a stall or loss of control.
It is important to keep in mind that powerlines also exist in remote areas where you least expect. For example, the pilots of the Stuart Highway accident probably did not expect powerlines in the remoteness of the Northern Territory, and the pilot of the Lake Eildon accident probably did not expect to encounter powerlines above the expanse of a large lake.
The effects of wirestrikes at low level are obvious — significant damage to the aircraft, usually leading to a loss of control and, because of the lower margin for recovery, subsequent impact with the ground or water. Pilots must keep in mind that not only do powerlines exist at low levels and in remote areas, they are also not easy to identify. Even against a clear blue sky, wires are difficult to spot for a number of reasons. Wires can oxidise to a blue/grey tinge and may blend into the background (ATSB, 2006), or the wire may be obscured by terrain. Single wires are difficult to detect from the air and can be encountered in the most unexpected places in rural areas. Even if a pilot has spotted a powerline, his or her ability to judge its distance from the aircraft can be distorted by optical illusions or a lack of nearby visual reference points.
Pre-flight assessment and planning is an important part of any flight. Make sure you have maps of your intended flight path with you when you fly, and study them before you get into your aircraft to identify any terrain, wire, or other obstacles that you need to avoid should operational circumstances necessitate flight at low level. If you have been trained and are qualified for low flying, and low flying is necessary, ensure that you conduct an aerial survey of the area from an appropriate height before you conduct any low flying.
Low-level flying also presents fewer opportunities to recover from a loss of control compared to flight at higher altitudes. It takes time to react and to regain control of an aircraft, and the closer to the ground you are, the less time and distance you have. Flying at low altitudes is not only risky when things are going right; it becomes downright perilous when things are going wrong.
Before you decide to conduct low-level flying, ask yourself whether there is a legitimate or operational reason for you to do so.