Thread: ASDA < TORA?
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Old 3rd Mar 2012, 04:50
  #15 (permalink)  
Join Date: Sep 2004
Location: Wichita Kansas USA
Posts: 31

As stated in these replies and in the AIM, airport design standards may require adjustments to the runway’s declared distances. In the event that the full, standard Runway Safety Area (1000’) cannot be obtain, a portion of the runway may be used to obtain the require RSA length. In this case, ASDA and LDA will be reduced as required to obtain this 1000’. The US is the only country currently applying this method to obtain full RSA; however, other countries and ICAO are considering adopting this practice. Another factor that may affect declared distances is the Runway Protection Zone (RPZ), which is designed to limit undesirable activity immediately beyond the runway. To obtain the required RPZ, the TORA may be reduced below the physical runway length. For example, see Concord, CA (KCCR).

True stopways, where ASDA is > TORA & TODA are rare in the US. Glasgow, MT (KGGW) is one airport that has an honest-to-goodness stopway on three of the runway ends. This is one of the few (only?) airport in the US with fully documented and declared stopway, declared being the operative word for use in accelerate-stop distance calculations. To be declared a stopway, the runway must have the stopway noted in the A/FD remarks and have published declared distances for that runway (ref: AC 150/5300-13).

Unfortunately, there are some aberrations in declared distances at some US runways. Detroit Metro (KDTW) being the latest:

02/451 (A1568/12) - RWY 22L TODA 11300. 28 FEB 17:00 2012 UNTIL 03 MAR 20:00 2012. CREATED: 27 FEB
19:45 2012

Declared Distances
Take Off Run Avbl. (TORA) 12,003/12,003
Take Off Dist. Avbl. (TODA) 12,003/12,003
Actl. Stop Dist. Avbl. (ASDA) 12,003/12,003
Lndg. Dist. Avbl. (LDA) 12,003/12,003

For the purpose of takeoff planning, accelerate-stop distance must be less than ASDA, takeoff distance must be less than TODA, and takeoff run must be less than TORA. Use of declared distances that differ from the full, physical runway length requires takeoff data that can take advantage of an un-balanced V1 speed and unbalanced field length calculation. For those airplane types that provide only balanced field takeoff data based on a balanced field V1 speed (within certification limitations), then the balanced field takeoff distance or runway limited takeoff weight must limited by the most restrictive of the ASDA, TORA, or TODA length.

Rich Boll
Wichita, KS
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