212man: I thought that TDP was time based precisely because of the lack of accurate IAS values at low airspeeds. What types have TDPs which are IAS based?
Civil IAS gauges typically are invalid below 25 kts and on some older types are inaccurate below 40 kts. That's without introducing crosswinds, where the errors are compounded. So, yes, on some types where a low TDP airspeed is used, the method of determining that point is to count down. That relies on a given acceleration and an accurate time, so is inherently inaccurate in itself, but seems to be "close enough for government work!"
Types that have a TDP based on IAS? Well, I can personally vouch for the AS332, S-76, B212, EC-155, S-61 and S-92, and I know other types do too.
Brom and 212man: Have you, or anyone else used a TDP equating to 70kts, or 60kts, or even 50kts?
On the EC-155 the TDP range was from 30 KIAS to 70 KIAS, resulting in Vtoss values from 40-80 KIAS. 60 KIAS was the change over point from first segment to second segment limiting, i.e. there was no further payload benefit from higher 70 or 80 KIAS Vtoss, but it left your decision till later. Precisely for the reasons stated (going IMC etc.) On the S-92 the TDP range is 30 - 55 KIAS with Vtoss values of 45-70 KIAS.
In these cases, a reject just prior to TDP would be interesting.
And, soggyboxers: You must have observed during your training/checking on short runways that quite a few pilots negate the parameters of their (calculated) TDP by, for example, reducing the effect of the flare during a reject by over leveling the aircraft, or flaring insufficiently etc etc. How do you ensure consistency in this area?
I have always taught maximum performance reject technique (as described in the RFM) so that it is the instinctive first reaction if the failure occurs for real. If, you decide that with 2000m of runway left you'd like to back off the flare, or not droop the guts out of it, that fine, on the day. But, if you have always been taught the gentle, run it on with 30 kts type technique, then come the day you really are RTDRH limited (short runway, big trees at the end) then you don't want to be learning it as you go along (though the big trees will help the learning!) Same applies for landing.
(No, LDP is not the point of loss of ETL, either
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