As the title says, in respect of short field ops?
Um….
Is accelerated stop actually a factor?
In terms of a more detailed response whats pilots feelings on parameters? So I had in mind a runway that is pehaps between 10% and 20% of minium operating parameters.
Fuji_Abound wrote:
Is accelerate stop actually a factor?
It depends on your attitude to safety margins. If you don’t think that an engine is going to fail, you can rotate just before the far piano keys, but equally, if you don’t think that an engine is going to fail, why bother with red lines, or, indeed, carrying more speed on take off?
Why would you want to carry more speed on take off? The only reason I can think of would be as Tim wrote to be above red line or possibly at blue line as a safety factor. Unless you are considering whether to adjust your Vr for head or tail winds?
I suppose my point was rather if you are operating within the parameters I mentioned an accelerated stop is porbably not much of an option anyway and therefore that safety margin was abandoned when you landed. However, you might still want to prepare for a failure and mitigate that risk as much as possible given the situation you have accepted.
Take an airfield like Sarlat LFDS for instance. Elevation around 1000 ft rwy length 747 metres tarmac. At the end of the rwy 28 there is a field of antennas approx 50ft agl and a water tower at 1000ft agl about 1Nm further away.
Your twin has a take off roll of 350metres and needs 650 metres to 50ft. The accelerate stop distance is 640 metres.(POH)
The (POH) short field take off technique is one stage flaps and to hold the aircraft on brakes until full power before release.
Temperature is 15degrees C.
What technique would you use and would it involve holding the a/c on the ground for greater speed before rotation?
Disregarding accelerate stop distance means there is no safe way out for an engine failure during some part of the take off run. If you are ok with that go for it. Carrying more speed that Vmca i doubt make any sense performance wise. Twins with both engines operative are somewhat over powered so TODR are usually shorter than LDR so if you managed to get in you are ok getting out for the same DA that is.
Wouldn’t it be more “efficient” to rotate and then fly in ground effect to build up speed? In the Twins I have been flying a bit, the airspeed increases fast after rotation to above blue line. That is if you don’t climb out too steep. The flying in ground effect is sometimes used for short field procedures in SEPs where you can “pop” the flaps to become airborne and then fly straight in ground effect to build up speed.
https://vimeo.com/user99433791/review/340864215/3024a11cb7
A little example. This is Bembridge, not especially short, but serves the purpose, as it is a clip to hand – just turning for a backtrack but this is scene for an Easterly departure. The ground rises quite steeply beyond the far threshold (although the video doesnt quite do this justice) and there is no sensible overrun (other than through the hedge, across the road and up a rising slope). The ground rises more steeply left and right of the far threshold, but falls away after a turn back into the circuit.
