You might want to define an Acceleration Check Point. At half the ground roll (TORR) your should have achieved 2/3 of your lift-off speed. (simple mathematical equasion) Otherwise you won’t make your expected TODR.
Thanks all. We’re definitely planning on an acceleration check point.
This morning we’ve had confirmation of our fuel in Addis, we’re getting a ~ 55 gallon drum (unfortunately it can only be ordered by the drum and is very expensive). That will give us full tanks (we should have landed in Addis with at least 20 – 25 gallons) and with two people will be still be well below our MTOW.
If anyone is interested you’re more than welcome to follow the trip on my Instagram account, just request to follow (https://www.instagram.com/nicolassharp/)
Archie wrote:
You might want to define an Acceleration Check Point. At half the ground roll (TORR) your should have achieved 2/3 of your lift-off speed. (simple mathematical equasion) Otherwise you won’t make your expected TODR.
This is an approximation which is valid if acceleration is more or less constant. I would not rely on that on a departure from Addis Abbeba.
A_A agree, it is a good rule of thumb, but at some point your excess power becomes negligible and you may not climb out of ground effect.
Flying at dawn or at night in the coolest possible air will create some safety margin.
I don’t know about the Dakota specifically (so check the POH!) but all other constant-speed non-turbocharged piston aircraft I have flown have a “best power” mixture at 100F rich of peak. Assuming you’ve got an EGT, I’d do a static full-power runup and lean to that EGT value.
When doing such a runup make sure you’re not on gravel or loose ground, but on solid and clean concrete or tarmac. It’s all too easy to pick up small stones, debris, sand and so forth. This can damage the prop and even clog up your air filter. And in those situations you don’t even want to think about carb heat or other alternate air checks that bypass the air filter.
Check your tyres – they’ll be working quite hard.
Oh, and all the stuff above. The lift fairies that give you IAS are exactly the same ones that tickle the wing. Stick by book speeds.
Fortunately, the runway appears to be long enough that you will get airborne simply due to the runway dropping from below you due to the curvature of the earth.
Joking aside – for the abort, pick an abort point of the approximate factored landing distance from 50ft – if you haven’t achieved 50ft at that point, you can still land back. No point in barreling down the runway to get airborne only to find out you won’t climb.
