Performance calcs Vs Reality (Video by AOPA/ASI)

CAO 20.7.4

Or maybe CAO 20.7.4 + 50% (Since the regs take approved flight manuals at their word.)

The advice to roll-your-own perf. charts seems a good idea for homebuilt types without authoritative manuals.

I guess the test flying could be done under any atmospheric conditions and any load if the results are adjusted for all the variables:

Source: Factors Influencing Landing & Takeoff Performance of Aircraft

Take off distance to 50 feet is a more useful real world number, any aircraft can be dragged off the runway but will it out climb any obstacles.

Over an obstacle is more practical. You can lift of in ground effect and then go nowhere fast if you are too heavy for the density altitude or underpowered. Ground effect is often why you float when landing.. Temperature and altiutude are most likely to catch you out if you are not familiar with it's effects. Long grass and soft wet surface will make acceleration difficult also. Special technique required. Nev

Do they still teach minimum ground roll take-off techniques?

It'd be good to incorporate the initial 50' of climb into our own perf. calcs somehow, though a bit harder to do.

None of us wants to be like the guy in the famous video of the hot, high and heavy Stinson crash.

(If you haven't seen it you can google "Airplane Crash In-Cockpit Footage: Stinson 108-3" )

But then, there are still more factors (apart from those listed above) which make the Calcs +50% advisable when ops are looking marginal.

Like in this story from the comments section of another video (about an EFATO in a Piper Lance):

Daniel Hawley

Ome I always have, but if the plane is that poor in the performance department it sort of shouldn't be flying anyhow (if you know what I mean) basic stuff not Cessna's etc.. If your plane won't get to over 3,000 ft. without staggering for ages lose weight or get another plane or fix the engine. Nev

... and/or be stingy with your sums, and/or take off into the dawn's early light, and/or leave a few of your would-be passengers behind:

It's a bit funny as the positive "G" limit is usually much higher than the negative one which is how that's loaded. Must have been a bit of an effort to get them into position. Nev

This is the actual flight testing, though:

Do they still teach minimum ground roll take-off techniques?

You must teach "look after the nosewheel" techniques. Nev

More information about how accurately they flew the book figures would be useful. E.g from an online POH the C182 performance calculation is based on an initial climb at 58 KIAS. If you let the speed build past that it will use a lot of extra runway. Allowing the speed to build to 66 KIAS would account for at least 30% extra ground roll compared to 58 KIAS. (66/58 squared, which assumes constant acceleration. Real life is probably worse)

Likewise the landing figures specify heavy braking. They said they used moderate braking which could easily account for 30%. Another thing to be aware of with braking - braking early when you are still going fast counts the most. Heavy braking when you have already slowed down doesn't make as much difference - the runway is already behind you.

Having said that, the book figures are very short and most of us would be challenged to achieve them. 433 feet is 132 metres. Add 50% and you are still below 200m, which would make you stop and think in a 182 I reckon...

I'm not sure if we've discussed this video here before, but it came up again today on the Tube.

What a shocking reminder of how reality bites when take-off performance margins are zeroed out:

https://www.youtube.com/watch?v=NvjuglBoWO0:936

The consequences of getting it wrong are severe.. If your plane is heavier than you've ever been on a warm day be ready to give the take off away regardless of what the POH says .You could have a dragging brake, soft surface or longer grass than you thought or an engine fault. RPM drop on a fixed pitch. Won't show on a C/S . You might not have given it full throttle. The carb heat may be on. Check both of these early in the run. Have a mental picture of where you will give it away if it's not able to get airborne and flying well, and stick to it. Don't just HOPE. Staggering into the air will only allow continued flight in ground effect and never hope/assume the engine will come good if it seems down on normal power. Some have attempted take off with Flaps at full setting also. Another one is to select flaps up instead of gear up immediately after lift off. Nev