Curious, do the runway takeoff length charts in Boeing/Airbus' ACAP documents include lengths calculated assuming a shutdown?

Or are they just standard day (+XX), sea level, flaps, packs on, etc?

Anyone?

IIRC, the ACAP charts are based on the FAA definition of runway required. That would be a balanced field where there is an engine failure at V1 and takeoff with a screen height of 35 feet or reject in the remaining runway. But if you read the ACAP pages it should have the criteria and I think it should have the details there.

mom is correct. Generic takeoff performance is full thrust, balanced field length.

OldAeroGuy wrote:

mom is correct.

How? He said balanced field with failure @V1, you're saying balanced field at full thrust.

Which one?

They're the same thing. All engines at full thrust until the V1 engine failure. Remaining engine(s) at full thrust through 35' or idle thrust at full stop.

(Actually, an engine is assumed to fail slightly before reaching V1 but I urge you to read AC25-7C for a full appreciation of how takeoff performance is calculated.)

And I meant mmo rather than mom.

OldAeroGuy wrote:

They're the same thing. All engines at full thrust until the V1 engine failure. Remaining engine(s) at full thrust through 35' or idle thrust at full stop.

(Actually, an engine is assumed to fail slightly before reaching V1 but I urge you to read AC25-7C for a full appreciation of how takeoff performance is calculated.)

And I meant mmo rather than mom.

What is AC25-7C?

EDIT: nm Google is my friend. https://www.faa.gov/documentLibrary/med ... -7C%20.pdf

This is a pretty cool resource; thanks for mentioning.
It would be great if the document contained hyperlinks to the portions of regulatory code that contain the critical conditions referenced. The regulators probably remember offhand what Section 25.109(a)(1)(ii) says but...
Then again textual complexity here probably helps make work for lawyers.
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Given the criticality of runway stopping distance, have designers/regulators ever considered a dragging mechanism for emergency rejected takeoff conditions?
I'm thinking of like a claw that you just throw down bury into the runway. Maybe attached to the landing gear or something. Seems like that would stop a plane pretty quickly (maybe too quickly?). If it only "scraped along" the runway it maybe wouldn't destroy the frame and/or whiplash the passengers but would decelerate faster than breaks.
That would damage the runway of course but maybe only superficially, allowing quick repair. And I can think of only one rejected takeoff from a big airliner in the few years (BA 77E at LAS), so maybe it's not a huge systemic cost if it improved field performance significantly.
Anyway just spitballing I can think of other obvious reasons not to do this...

Uh, stopping mechanisms come factory installed on all Boeing and Airbus MLG assemblies..

Matt6461 wrote:

This is a pretty cool resource; thanks for mentioning.
It would be great if the document contained hyperlinks to the portions of regulatory code that contain the critical conditions referenced. The regulators probably remember offhand what Section 25.109(a)(1)(ii) says but...
Then again textual complexity here probably helps make work for lawyers.
-------------------------

Given the criticality of runway stopping distance, have designers/regulators ever considered a dragging mechanism for emergency rejected takeoff conditions?
I'm thinking of like a claw that you just throw down bury into the runway. Maybe attached to the landing gear or something. Seems like that would stop a plane pretty quickly (maybe too quickly?). If it only "scraped along" the runway it maybe wouldn't destroy the frame and/or whiplash the passengers but would decelerate faster than breaks.
That would damage the runway of course but maybe only superficially, allowing quick repair. And I can think of only one rejected takeoff from a big airliner in the few years (BA 77E at LAS), so maybe it's not a huge systemic cost if it improved field performance significantly.
Anyway just spitballing I can think of other obvious reasons not to do this...

As Redbellyguppy says, stopping mechanisms are standard equipment. The brakes are massively powerful. Far better at slowing you down than the engines are at speeding you up. To quote SlamClick.

Add to that, automatic ground spoilers that are going to kill the lift upon wheel spin-up, thrust reversers that no one has said I cannot use, and the mind-boggling multi-disc, multi-puck, anti-skid protected brakes and I'm beginning to think that the last thing I'd see before sliding to stop in a cloud of tire and brake smoke is my own paint job sliding off the nose of the airplane.

Starlionblue wrote:

The brakes are massively powerful. Far better at slowing you down than the engines are at speeding you up.

Sure. Brakes plus a claw would still be better at slowing down than brakes alone. Like I said, just spitballin for fun.

Is there any handy reference for accelerate and stop distances (as opposed to accelerate+stop=balanced field) for different models?

Using a drag chute would be lighter than a claw and chain and less damaging to the runway.

Still, carrying around a drag chute that would be used very sparingly if
at all creates an unnecessary operating expense/payload limit.

In the airline operational world, brakes, spoilers and thrust reversers stop an airplane just fine.

OldAeroGuy wrote:

Using a drag chute would be lighter than a claw and chain and less damaging to the runway.

Still, carrying around a drag chute that would be used very sparingly if
at all creates an unnecessary operating expense/payload limit.

In the airline operational world, brakes, spoilers and thrust reversers stop an airplane just fine.

There's the rub. Braking chutes, claws or other such devices are just wasted weight on almost every flight. The number of runway overruns is vanishingly small.

If we want to continue the thought experiment, though, I think a claw would have a hard time getting a grip. It would just skip off the top.

Starlionblue wrote:

OldAeroGuy wrote:

Using a drag chute would be lighter than a claw and chain and less damaging to the runway.

Still, carrying around a drag chute that would be used very sparingly if
at all creates an unnecessary operating expense/payload limit.

In the airline operational world, brakes, spoilers and thrust reversers stop an airplane just fine.

There's the rub. Braking chutes, claws or other such devices are just wasted weight on almost every flight. The number of runway overruns is vanishingly small.

If we want to continue the thought experiment, though, I think a claw would have a hard time getting a grip. It would just skip off the top.

Plus with the inevitable cost of deploying such a system there would almost be hesitancy on the part of the crew to deploy, similar to that experienced by military pilots ejecting (more likely to die when they should have ejected during training than during combat). The weight added by the fact that a parachute/Claw are added which creates new load paths and packaging requirements might actually make it more dangerous to have one...

Fred