Question regarding field length requirement class B aircraft
Hi,
Me again. Questions regarding the calculation of the field length requirement for class B aircraft, The rule says:Takeoff Field Length Requirements - SEP and MEP
a) When no stopway or clearway is available the take-off distance when multiplied by 1.25 must not exceed TORA.
b) When a stopway and/or clearway is available the take-off distance must:i) not exceed TORAii) when multiplied by 1.3, not exceed ASDA; oriii) when multiplied by 1.15, not exceed TODAI actually have an issue understanding the "and/or" part and when to apply the i), ii), iii). If I take for example an airfield with these declared distance:
TORA = 1500m
ASDA = 1500m
TODA = 1500m
In this case, only a) is applicable. Therefore, for my aircraft, the maximum TOD will be 1500M/1.25 = 1200M
Now, let's assume that the same airfield has now a clearway of 300 m but no stopway (very common layout). The declared distances will be:
TORA = 1500m
ASDA = 1500m
TODA = 1800m
In this case, I assume that b) is applicable because there is a clearway. BUT, b) has 3 conditions:
i) not exceed TORA
ii) when multiplied by 1.3, not exceed ASDA; or
iii) when multiplied by 1.15, not exceed TODA
So if we do the calculation, we will have:
TORA 1500/1 = 1500m
ASDA 1500/1.3 = 1154m
TODA 1800/1.15 = 1565m
Therefore, this time, the limited distance will be 1154m.
And this where I am lost. Knowing that the distances (without clearway, first example) would give a limited distance of 1200M and the same distances with a clearway would give a limited distance of 1154M, Why do we bother declaring a clearway if this will reduce the takeoff weight of the aircraft ?
So, should we always apply all these 3 conditions automatically (everytime there is a clearway or a stopway or both) or should we understand : "if there is a clearway, and no stopway, only apply i) and iii)" ? Which would make more sense for me. because that way, in the second example, the limited distance would be 1565m vs 1200m and then, the presence of a clearway is useful.
Am I correct ?
Thanks !