Tax reserve
In aviation, the tax reserve ( Steering Margin ) denotes a measure of the possibility of influencing the flight path that is currently available to the pilot ; it therefore indicates how much the pilot can still change the flight path in a certain direction in a certain situation until a control limit is reached. The tax reserve can also be viewed as the difference between the current tax and the tax limit in the respective tax dimension.
definition
“The control reserve describes the possibility of influencing the flight path by means of control inputs that the pilot has at any given moment in relation to a certain control dimension and control direction. When a tax reserve is completely used up, the corresponding tax limit has been reached; this means that at the moment the pilot can no longer change the flight path in the appropriate direction via a control input. "
meaning
The tax reserve remaining until a tax limit is reached has a major influence on a pilot's options for action. Is the knowledge of the present control reserve in the respective control direction of a display control means so that an essential element of the situation awareness (engl. Situation Awareness ).
Problem
For safe manual flight guidance, the pilots' mental model must be aware of the current flight status. The knowledge of the extent to which the flight path can still be influenced by further control inputs, i.e. how high the remaining tax reserve is until a tax limit is reached, is of great importance for the resulting situational awareness as a central factor in flight safety. Problems can arise here, particularly with regard to modern, sidestick-controlled fly-by-wire aircraft: Here, the pilot's control inputs made on the sidestick are not directly converted into fixed deflections of the control surfaces; instead, the modulation of the sidestick is considered as a default value for the adoption of roll rates or load multiples ( rate command ). The actual implementation of these specifications depends on a large number of condition parameters of the immediate environment (e.g. atmospheric condition parameters), the aircraft itself (e.g. current configuration, flight speed and weight, existing control surface deflections) and the operating mode of the avionics (e.g. B. flight phase, already approaching defined limits) and is not immediately visible to the pilot.
This can lead to critical situations in which pilots are not immediately aware that a control input will not be implemented (or not implemented in the usual way) (see for example the storm landing of Lufthansa flight "LH 044" on March 1, 2008 in Hamburg-Fuhlsbüttel ).
See also
Individual evidence
- ↑ Florian JJ Schmidt-Skipiol Haptic feedback when operating fly-by-wire aircraft. Lower Saxony Research Center for Aviation, Braunschweig 2018, ISBN 978-3-947623-01-3 .
- ↑ Federal Bureau of Aircraft Accident Investigations (BFU) Investigation report of the serious incident on March 1st, 2008 in Hamburg - 5X003-0 / 08. Federal Office for Aircraft Accident Investigations (BFU), Braunschweig, 2010, official investigation report.