Simviation Forum

Feb 24^th, 2005 at 2:30pm

MarcoAviator Offline
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For what I know V1 (for big planeys) is the speed past which you can't abort takeoff.

Past V1 you have to lift off.

V1 is a function (I am sure) of runway lenght and weight.

But suppose that you have a 12 miles runway.

Is there still a V1? is V1 also (perhaps) dependent upon the fact that past V1 brakes won't work and the gear won't last long or something like that?

In other words is V1 a mechanical limitation besides being a "logistical" limitation (runway lenght, weight)?

I know that in some cases you can have Vr past V1 (which is interesting because past V1 you cant' abort takeoff and if you find out that you can't lift off you are up a Teteroboro creek without a philly cheesesteak).

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Reply #1 - Feb 24^th, 2005 at 6:15pm

beaky Offline
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I think a 12-mile runway would be considered a highway ... Grin

Seriously, I think V1 is based on some sort of assumed average runway length, probably the minimum safe length for the aircraft in question.

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Reply #2 - Feb 24^th, 2005 at 10:13pm

Nexus Offline
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V1 is also based on runway conditions.
Wet and snowy runway pavement will result in lower V1, since the contamination decreases braking efficiency. Then we will add weight and temp. to the mix, and our v-speeds will be neatly found in the QRH etc.

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Reply #3 - Feb 24^th, 2005 at 10:34pm

Saratoga Offline
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Ya, many small planes with low runway requirements have a standard V₁ for all flight weights, weather conditions, et cetera. But on airliners, the V₁ can have as much as a 50 knot range!

Pretty much, at V₁ the pilots take their hand off the throttles and are dedicated to the takeoff. Some airports, even if you abort before V₁ you will run out of space, others you could start slowing down way after it and make it.

I dunno where you heard the mechanical aspect. Brakes work perfectly at this speed, though the heat can build up quickly slowing down from 140 or so. The landing gear are ALWAYS stressed to maintain V₁ without any problems.

The low-down on all the speeds:
V₁: the plane is committed to fly no matter what happens.
V_r: At this point the pilot flying begins a smooth rotation to the appropriate attitude.
V₂: the minimum safe speed if an engine were to fail. This is when the plane should leave the runway. Though often pilots hit this speed while still rotating from V_r and therefore will not lift off until several knots later.

Hope it helps! Wink

Pilot for a major US airline certified in the: EMB-120, CRJ, 727, 737, 757, 767, and A-320 and military, T-38, C-130, C-141, and C-5 along with misc. other small airplanes. Any questions, I'm here for you.

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Reply #4 - Mar 11^th, 2005 at 1:29pm

N556EP Offline
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Well iv heard a couple of stories of aircraft RTO past v1. A beech jet Powered up rolling dowen the runway, Passes v1 all of a sudden a crowd of birds come in to view and they hear "thump thump thump" they Retarted the throttles full reserve and full braking still ran off the runway, but no one was hurt, but when they inspected the aircraft One engine ingested birds and dents in the leading edges. They said it was A gutys call by the capitan but a good one. Captians call for an RTO pass V1.

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Reply #5 - Mar 12^th, 2005 at 9:17pm

Saratoga Offline
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At V₁ we remove our hands from the throttles so we have to inclination to abort the takeoff. There are some special circumstances that would allow a post-V₁ abortion. Those being, small planes with low weights and a long runway. I know of a company 737 that aborted a takeoff at 5 under V₂ at JFK and managed to stop long before the end of the runway. Every situation is different, but for the most part, it's highly discouraged to abort anywhere close to or above V₁.

Pilot for a major US airline certified in the: EMB-120, CRJ, 727, 737, 757, 767, and A-320 and military, T-38, C-130, C-141, and C-5 along with misc. other small airplanes. Any questions, I'm here for you.

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