It is necessary to fly low for takeoff and landing. The low-flying risks are managed by using circuit patterns at aerodromes, with any obstacles known, so that there is less chance of colliding with other aircraft or unexpected terrain.
Low flying at other times is risky because of the chance of colliding with terrain, or things on the terrain. Collisions happen when pilots cannot see obstacles, do not see obstacles in time to avoid them, or are aware of obstacles but become distracted by another task and fail to avoid the obstacles. Wires are the most common type of obstacles, and pilots collide with them for all of the reasons described above. Low flying also further adds risk because if something does go wrong there is less time or opportunity to fix what has gone wrong.
At flying speed, sufficient visibility is needed to allow pilots to see and to avoid obstacles. Visibility is also required to maintain orientation, so pilots know which way is up and can maintain control (the exception is when an aircraft is being controlled using instrument flight techniques). Visibility is reduced by cloud, dark, or materials in the air such as rain, smoke or general haze. Two main risks are associated with flying in limited visibility:
loss of orientation, leading to loss of control of an aircraft and an uncontrolled flight into terrain
insufficient visibility to enable a pilot to see and avoid obstacles while remaining under control, known as a controlled flight into terrain.
The same hazards can also apply during night flight because less can be seen, even though the visibility may be just as good.
There are many ways for the engine fuel supply to be interrupted. The supply may run out because of not knowing the actual amount of fuel on board, or the rate of fuel consumption. The fuel supply may be switched off, particularly in aircraft with more complex fuel systems. The fuel supply may also be stopped by a filter blockage, water in the fuel tank, or a blocked fuel tank vent system. Thorough use of procedures is required to manage the various risks. Hazards increase when a flight is planned to use all the available flight fuel, particularly when the pilot is unfamiliar with the necessary procedures because shorter, non-fuel-critical flights are normally flown.
Management of common threats and errors
Operational problems can develop gradually, like deteriorating weather conditions or increased fuel consumption. Problems can also be sudden, like an unexpected power reduction or an obstacle looming in front of an aircraft in flight. A range of procedures and requirements exist to enable pilots to manage the hazards associated with all the common avoidable accident types.
The ATSB’s Avoidable Accidents booklets feature case studies on regularly occurring accidents that could have been prevented with good flight management and preparation. The booklets also provide helpful hints and strategies to help pilots stay safe when flying.