I'm puzzled about V1, V2 and Vr speeds. I do understand that these settings are calculated as a result of such things as Aircraft total weight, runway length and condition weather. Once those nembers are available, what decisions confront the PF on 'brakes off'? - e.g V1 decision time, Go or abort? At what point can the PF decide to continue the TO if a failure occurs? I'm sorry for my clumsy explanation, I hope you will understand the point I'm making :) Ken

Not too sure what you are asking, so two answers.1. You already answered your own question. V1. Hence the name decision speed.2. At V1, for most people, power loss, fire or flight control failure are what one would abort for. Some abort for any malfunction. Some only abort for any malfunction below say, 80kts.

Say you're in a 737:You're rolling down the runway with power set. If a problem occurs you have until V1 to stop the aircraft on the runway with maximum braking and reverse thrust. Beyond V1 you are better off taking the problem into the air, unless it's catastrophic - in which case running off the end of the runway may be the preferred option. Vr is the rotation speed of course, and is calculated so that if an engine fails you can still reach V2, which is the best climb rate with one engine out. So even if you loose an engine after V1 you can still take-off safely.That's how I understand it. I'm sure others will correct or expand on it.Ian

>2. At V1, for most people, power loss, fire or flight control>failure are what one would abort for. Some abort for any>malfunction. Some only abort for any malfunction below say,>80kts.Unless you've had a wing fall off, you're taking whatever problem you have into the air after V1 to deal with it there. There are many fatal accidents caused by aborts after V1 that would have been much safer to takeoff with. Our pilots are trained to remove their hands from the thrust levers at V1 to reduce the possibility of reflex action to close the throttles due to a situation that would cause an abort below V1.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

>>2. At V1, for most people, power loss, fire or flight>control>>failure are what one would abort for. Some abort for any>>malfunction. Some only abort for any malfunction below say,>>80kts.>>Unless you've had a wing fall off, you're taking whatever>problem you have into the air after V1 to deal with it there.>There are many fatal accidents caused by aborts after V1 that>would have been much safer to takeoff with. Our pilots are>trained to remove their hands from the thrust levers at V1 to>reduce the possibility of reflex action to close the throttles>due to a situation that would cause an abort below V1.>>Cheers,>>John>>Boeing 727/737 & Lockheed C-130/L-100 Mechanic>>http://www.precisionmanuals.com/images/forum/ng_driver.jpg1. Aborting above V1 is not allowed and goes against the definition of V1 and any sort of approved training.2. Did you mean "reflex action to close the throttles due to a situation that would cause ONE TO abort ABOVE V1."3. If your wing fell off, there wouldn't even be a chance for a decision, would there?

>>>2. At V1, for most people, power loss, fire or flight>>control>>>failure are what one would abort for. Some abort for any>>>malfunction. Some only abort for any malfunction below>say,>>>80kts.>>>>Unless you've had a wing fall off, you're taking whatever>>problem you have into the air after V1 to deal with it>there.>>There are many fatal accidents caused by aborts after V1>that>>would have been much safer to takeoff with. Our pilots are>>trained to remove their hands from the thrust levers at V1>to>>reduce the possibility of reflex action to close the>throttles>>due to a situation that would cause an abort below V1.>>>>Cheers,>>>>John>>>>Boeing 727/737 & Lockheed C-130/L-100 Mechanic>>Your first post wasn't clear and it appeared that you had made reference to aborts above V1. >1. Aborting above V1 is not allowed and goes against the>definition of V1 and any sort of approved training.>Correct!>2. Did you mean "reflex action to close the throttles due to a>situation that would cause ONE TO abort ABOVE V1."There is no abort above V1. The reflex action is just that, a reflex. It has been proven that if the PF left their hand on the power levers after V1, the likelyhood of an abort above V1 for a failure that would cause an abort 'BELOW V1' is very high.>>3. If your wing fell off, there wouldn't even be a chance for>a decision, would there?That was the point I was making. V1 and you're flying regardless of the failure.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

Would it be clearer if I rearranged the wording from the first post this way. "You can abort for a malfunction at or below V1. Some people are trained to only abort for power loss, fire or flight control failures between 80kts to V1. Some are trained to abort for any malfunctions up to V1."

Many thanks for all your replies everyone; my question was not very clear, but you have helped me sort it out, in my mind at least:)What we are saying is - up to the V1 speed, in the event of any failure, the take off can be aborted in the knowledge we have enough runway left to do so? At V1 and after, the T/O should continue (assuming the "wings falling off" or other catestrophic failure has not occurred). Is that about right?Ken

My company pilots explained it this way:Up to V1 - it's a ground problemAt or above V1 - it's an inflight problem - even if the wheels are still on the runwayThey also added this - at or after V1 - attempting to abort a take off WILL result in the aircraft crashing through the end of the runway and into what every happens to be on the other side of the fence. No maybe - you will crash the aircraft if you abort at / after V1.My company also requires pilots to take their hands off the throttles at V1.The aircraft are 2 G-200's and 2 CL-601's.

Exactly......and as most people have said, at V1 in most multi crew aircraft one would take ones hands off the power levers to prevent inadvertant rejected take offs.The other two (which so far haven't been mentioned)Vr - Rotate speed, is the speed at which the aircraft can commence a pitch rotation to take off. Note this is not the speed at which the aircraft should or will leave the ground but the speed at which the rotation starts.V2 - is the engine out safety speed. This is the minimum speed at which the aircraft is directionally controllable with the critical engine failed and the other(s) at the take off power being used. If you slow down below this speed then the aircraft will wander off in the direction of the failed engine (despite full rudder and maybe aileron). This may introduce terrain/obstacle clearance issues and is not considered a "good" thing to do. It's nice to be faster than this speed asap after take off.Hope this helps,Ian

Was visiting a pilot friend, and he showed me a good training DVD for the MD-11 on "Loss of an engine at or after V1". One of the things the video emphasized, was at V1 the pilot MUST have the mindset that he is taking off, regardless. The PF's actions involve correcting for the yaw and pitch (determined by the engine failing) before during and after rotation, up through FMC takeover. The PNF is confirming the engine failure and cause. Both pilots concur on engine ident prior to securing the engine.scott s..

Ian wrote:>V2 - is the engine out safety speed. This is the minimum speed>at which the aircraft is directionally controllable with the>critical engine failed and the other(s) at the take off power>being used. If you slow down below this speed then the>aircraft will wander off in the direction of the failed engine>(despite full rudder and maybe aileron). This may introduce>terrain/obstacle clearance issues and is not considered a>"good" thing to do. It's nice to be faster than this speed>asap after take off.No, sorry, V2 is takeoff safety speed, but you have defined Vmca here, not V2. V2 is a compromise speed unique to a particular aircraft, weight, thrust setting, and configuration. It is at least 20% higher than Vs, and 10% higher than Vmca (Vmca ensures directional control with a critical engine failure and no more than 5 degrees of bank away from the dead engine). The most important consideration for maintaining at least V2 is that your obstacle clearance performance is predicated on the climb gradient performance obtained by climbing at V2 or above.On the subject of V1, it's not as absolute as many in this thread have opined. Never say never. V1 is decision speed predicated on a simple...and single...failure. Pilot judgement is always needed, as there are many possible failures which could require either an abort above V1 or continuation of the takeoff from below V1. It is paramount to understand the performance margins that go into computation of the V speeds in addition to knowing what the speeds are. The truth is that up to V1, you know that the airplance has the capacity to stop on the runway, and after V1 you know that the airplane has the capacity to takeoff with a single engine failed. If you are taking off on a very long, dry runway, it's likely you could stop well after V1 speed...but not certain.Consider two examples: In the first, a catastrophic engine failure occurs after V1 and causes a second engine to fail. The V1 speed only guarantees a successful takeoff with a single engine out. If I have significant terrain or a high density altitude situation, my odds of survival may well be better to try the abort.In the second scenario, I am departing an icy runway in flat terrain with a crosswind near limits, and at 2 knots below V1 I lose an upwind engine and with it my primary hydraulic system...which in my airplane is required for anti-skid braking. Do I attempt a heavyweight high-speed abort with the directional control double-whammy of asymetric thrust and weathervaning on an icy runway...and stopping without anti-skid, or do I take the plane into the air where I can burn off fuel and find a nice, long, dry place to put it down?Bottom line...V1 is a decision speed in the most-probable uncomplicated single-failure scenarios. But there are lots of complications that can drive other decisions. In the real world I have aborted above V1 (flock of large birds lifted off the runway into my likely flight path) and continued a takeoff with an impending failure indication below V1 (engine overheat light) and in both cases it was the right call, and the other option presented more risk of a catastrophic unhappy ending.RegardsBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

Bob,Great reply . . . spoken like a true professional. I was about to answer those same questions when I read the last, (your) thread. As usual, you put it into firm, precise, no nonesense terms which makes it easy for the 'non-pilot' to understand.Whenever you think you have found the 'no options' button, Murphy will provide one for you. And, Murphy, it seems was an optimist!Again, great response, couldn't have answerered it better myself.Best to you and yours,Clayhttp://www.dreamfleet2000.com/gfx/images/F...ers/Dopke01.jpgClayton T. Dopke (Clay)Major, USAF (retired)"Drac"

Clay; Right on with Mr Murphy. He has an ugly way of coming up with new twists on every old problem under the sun. We just get to discover and document those new twists as we go along. And the evil genius of man's creativity just provides more fuel for the fire. I used to tell my UPT students that every note, caution, and warning in the Dash-1 ought to have in the caption the name of the poor bloke that brought that issue to our attention.i.e.WARNING (2Lt C. R. Terror)Operation of the canopy unlock lever in flight may result in loss of the canopy due to slipstream forces. In the event canopy is lost, see paragraph 3-15, "Loss of pressurization" and para 3-102 "I'm stupid and it's freezin-a** cold in here.":-)CheersBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

BobI too go with your answers. There was an aircraft at Leeds UK where the Pilot had a severe engine fire and aborted after V1. It was very clear that had he taken off the aircraft would have been a fireball before they had a chance to come back in to land.V1 is a speed not an accelerate stop calculated distance. On some aircraft which have a short takeoff distance and which happen to be on a long runway V1 and way beyond could be achieved with a stop on the remaining runway.I would go further and state that in certain aircraft/runway situations in very rare occasions the best option could be after takeoff to put the aircraft back down.Citations? come to mind where on a runway like Heathrow a Citation could reach V1 brake to a stop and accelerate up to V1 and break to a stop again all on the same runway.Peter