With respect to performance, different aircrafts are certified at different times and comply with different certification rules. Three major certifications rules were defined as:
- FAR Part 25 – no consideration for reaction time of pilot
- Amendment to FAR Part 25 known as Amendment 25-42 – over consideration of reaction time
- Post Amendment 42 – current undermentioned considerations
We are in the phase of post amendment 42 under which following points are considered:
- following engine failure aircraft continuing for 2 seconds at V1 speed
- runway condition DRY or WET must be taken in account and same should be available for takeoff
- available brake condition for calculation is considered to be worn to their overhaul limit
Following are the regulatory consideration for calculation of TOD, TOR and ASD post amendment 42.
Takeoff Distance (TOD)
TODdry
Take off distance on dry runway is greater of the following values:
- distance covered from brake release to the point when aircraft is 35 ft above takeoff surface assuming critical engine failure at Vef and recognized at V1.
- 115% of the distance covered from brake release to the point when aircraft is 35 ft above takeoff surface with all engine operative
TODwet
Take off distance on wet runway is greater of the following values:
- takeoff distance on dry runway(calculated as above TODdry)
- distance covered from brake release to the point when aircraft is 15 ft above takeoff surface, ensuring V2 speed is achieved before airplane is 35 ft above takeoff surface assuming critical engine failure at Vef and recognized at V1.
Takeoff Run (TOR)
TORdry
Takeoff run on dry runway is greater of following values:
- distance covered from brake release to the point equidistant between Vlof point and point when aircraft is 35 ft above take off surface assuming engine failure of the critical engine at Vef and recognized at V1. Equidistant point is the mid point between Vlof reaching point and 35 ft reaching point.
- 115% of distance covered from brake release to the point equidistant between Vlof point and point when aircraft is 35 ft above take off surface assuming all engine operative. Equidistant point is the mid point between Vlof reaching point and 35 ft reaching point.
TORwet
Takeoff run on wet runway is greater of following values:
- distance covered from brake release to the point when aircraft is at 15 ft above takeoff surface ensuring V2 speed to be achieved before airplane is 35 ft above the take off surface assuming failure of engine at Vef and recognition at V1.
- 115% of the distance covered from brake release to the point equidistant between Vlof reaching point and point at which aircraft is 35 ft above takeoff surface assuming all engines operating.
Accelerate Stop Distance (ASD)
ASDdry
Accelerate stop distance on dry runway is greater of the following:
- sum of distances necessary to accelerate airplane with all engine operating to Vef, accelerate from Vef to V1 assuming the critical engine fails at Vef and pilot takes first action to reject the takeoff at V1, comes to a full stop and distance equivalent to 2 seconds at constant V1 speed
- sum of distances necessary to accelerate airplane with all engine operating to V1 assuming pilot rejects at V1, aircraft comes to full stop with all engine operating ans distance equivalent to 2 seconds at constant V1 speed.
ASDwet
Accelerate stop distance on wet runway is greater of the following:
- ASDdry
- (with wet runway conditions) sum of distances necessary to accelerate airplane with all engine operating to V1 assuming pilot rejects at V1, aircraft comes to full stop with all engine operating ans distance equivalent to 2 seconds at constant V1 speed.
- (with wet runway conditions) sum of distances necessary to accelerate airplane with all engine operating to Vef, accelerate from Vef to V1 assuming the critical engine fails at Vef and pilot takes first action to reject the takeoff at V1, comes to a full stop and distance equivalent to 2 seconds at constant V1 speed
Key Note:
- Delay 1 second is considered between Vef and V1 during which aircraft accelerate to V1
- 2 seconds of constant speed distance is considered
- Terms TODR and TOD, ASDR and ASD, LD and LDR are used interchangeably
https://aviationthrust.com/notes/icao-recommended-airport-signs-runway-and-taxiway-markings/