now if RW length has nothing to do with V1 and as was said it is a "Decision Speed", then all the decelerations here at the Forum of V1 being the ability to stop on time or notwithout crashing at the end of the RW are no longer valid.

Runway length has nothing to do with V1. It doesn't even appear in V1 charts. By your definition (2) on a very short runway V1 might be 80 knots, way below flying speed. Where runway length comes into it is if there is not enough runway to accelerate to V1 and then stop. In that case you have to operate at a lower weight so your new V1 is low enough to allow you to stop in the available distance. Reducing weight means lower V1 and shorter stopping distance. Or you could increase flap angle, or use full thrust.So runway length is important and it does inter relate with V1, but V1 does not take runway length into account. As Ronan was saying it must always be less than or equal to Vr. If you are rotating then by definition you are committed to fly, you've already passed V1.Kevin Hall

Runway length has nothing to do with V1. It doesn't even appear in V1 charts. By your definition (2) on a very short runway V1 might be 80 knots, way below flying speed. Where runway length comes into it is if there is not enough runway to accelerate to V1 and then stop. In that case you have to operate at a lower weight so your new V1 is low enough to allow you to stop in the available distance. Reducing weight means lower V1 and shorter stopping distance. Or you could increase flap angle, or use full thrust.So runway length is important and it does inter relate with V1, but V1 does not take runway length into account. As Ronan was saying it must always be less than or equal to Vr. If you are rotating then by definition you are committed to fly, you've already passed V1.Kevin Hall

I hope you don't fly for real - that is totally inaccurate!Best regards,Robin.

@Joel: V1 is a very specific speed. It is semi-related to runway length, only insofar as, let's say, the maximum weight of the aircraft requires an 8000 ft runway, and we only have a 6000 ft runway, meaning we are PERFORMANCE LIMITED. In this case, V1 is computed for the characteristics of the runway, airport elevation, prevailing conditions, airport altitude, and aircraft performance.If we required 8000 ft of runway at MTOM, and we had 15000 ft available, then V1 would be affected by runway contamination, weather and airfield elevation. In fact, V1 and Vr can be at unity under these conditions (there would be no V1 call, only "STOP STOP STOP" OR "ROTATE", as applicable).At NO TIME does V1 exceed Vr - it would be nonsense for it to. Above Vr, and you should be flying. Below Vr, and you should be on the ground, but maybe in that zone between V1 and Vr, where you are too fast to stop and too slow to fly.Maybe it would help you to look at the definition of V2 (1.2 Vs or 1.1 Vmca). This gives you some safety margin for the takeoff.If we take the extreme example of an infinite runway length, then V1 will still, at best, equal Vr. It will never exceed Vr, and neither will V1/Vr (or V2 for that matter) ever keep rising perpetually. At some point, irrespective of runway length, the aircraft will be at a safe speed to fly. Anything after that is arguing a moot point. You really want to stay on the ground until 300 kts?In summary:V1 is the takeoff decision speedVr is the rotate speedV2 is the minimum climb speed that must be reached at a height of 35 feet above the runway surface, in case of an engine failure.That is it, in a nutshell.Best regards,Robin.

that is what I thought, however no one said that in that way ofV1 would be a limitation of RW length (not enough RW to stop behind that point), however if RW length is not an issue the V1 definitionis changed and it becomes the Decision To take off or not only! (which would be Vr probably).all that was said is "that is the rule"no one said anything about the "if V1 NOT = RW length to stop issue THEN V1 = pilot Decision to take off" condition.that is why I continued trying to make my point herebut now you made it clear.Thanks.

Runway length has nothing to do with V1. It doesn't even appear in V1 charts. By your definition (2) on a very short runway V1 might be 80 knots, way below flying speed. Where runway length comes into it is if there is not enough runway to accelerate to V1 and then stop. In that case you have to operate at a lower weight so your new V1 is low enough to allow you to stop in the available distance. Reducing weight means lower V1 and shorter stopping distance. Or you could increase flap angle, or use full thrust.So runway length is important and it does inter relate with V1, but V1 does not take runway length into account. As Ronan was saying it must always be less than or equal to Vr. If you are rotating then by definition you are committed to fly, you've already passed V1.Kevin Hall

I think you got it all wrong m8

I think you got it all wrong m8

Joel, I think you've misunderstood what I said. Tell me what you think I've got wrong and I'll try and explain.Kevin Hall

Hi Joel,Can you rephrase this part. My friend Robin made it clear for you, but this is not very clear."that is what I thought, however no one said that in that way ofV1 would be a limitation of RW length (not enough RW to stop behind that point), however if RW length is not an issue the V1 definitionis changed and it becomes the Decision To take off or not only! (which would be Vr probably).all that was said is "that is the rule"no one said anything about the "if V1 = no RW length to stop issue THEN V1 = pilot Decision to take off" condition.that is why I continued trying to make my point herebut now you made it clear."

all that was said is "that is the rule"no one said anything about the "if V1 not = RW length to stop issue THEN V1 = pilot Decision to take off" condition.

V1 is defined as the takeoff decision speed/safety decision speed. There is no other definition for it.An example:You are below V1. You have an engine failure. You have an option: stop or go? Statistics show a GO is safer under this condition.You are below V1. You have an engine failure/fire. You would STOP in this condition - a fire in flight could be deadly.You are AT V1. You have an engine failure. You have an option: stop or go? Statistics show a GO is safer under this condition.You are AT V1. You have an engine failure/fire. You would STOP in this condition - a fire in flight could be deadly.You are 2kts above V1. You have an engine failure/fire. You would GO in this condition - stopping now could result in an overshoot.There was an accident with a Boeing 707 years ago. They suffered an engine failure at V1. The decision was taken to reject the takeoff. By the time they set idle thrust and started braking, they were 30 kts over V1. The aircraft required 7000 ft for the takeoff. They had 12000 ft ahead at the start of the takeoff run. They ran off the end, collapsing the gear. The crash investigators discovered the aircraft was 4 tons over MTOW. They did a computation - at 4 tons over MTOW at the actual reject speed, they calculated they needed 15000 ft to stop from the rejection point.Best regards,Robin.

Joel, I think you've misunderstood what I said. Tell me what you think I've got wrong and I'll try and explain.Kevin Hall

Hi Kevin,The part that was wrong is this "V1 does not take runway length into account". It does.regards,

Hi Joel,Can you rephrase this part. My friend Robin made it clear for you, but this is not very clear.

Robin did make it clear, however he is the 1st to do so, that is what I meant.

Hi Kevin,The part that was wrong is this "V1 does not take runway length into account". It does.regards,

Clearly runway length affects the V1 you end up with but traditional paper V1 charts don't have runway length as an input, that's what I meant. No doubt with EFBs and laptop based takeoff performance applications the process is more integrated and automated.Kevin Hall

V1 would be a limitation of RW length (not enough RW to stop behind that point), however if RW length is not an issue the V1 definition

Look up balanced field takeoff and then get back to me.

Clearly runway length affects the V1 you end up with but traditional paper V1 charts don't have runway length as an input, that's what I meant. No doubt with EFBs and laptop based takeoff performance applications the process is more integrated and automated.Kevin Hall

Kevin,here's a traditional take off data chart. As you can see you can enter this chart in two ways. Both ways starting at the top with runway lenght. Now you can go down to your actual temperature and find you Runway Take Off Mass limit. Or go down to you actual TOM and find you assumed temperature. (this does require a few more steps) This is a general runway chart. You need to correct these general take off charts for wind, slope and then you would take the conservative approach.

I

Kevin,here's a traditional take off data chart. As you can see you can enter this chart in two ways. Both ways starting at the top with runway lenght. Now you can go down to your actual temperature and find you Runway Take Off Mass limit. Or go down to you actual TOM and find you assumed temperature. (this does require a few more steps) This is a general runway chart. You need to correct these general take off charts for wind, slope and then you would take the conservative approach.

A different presentation from charts I've seen which have field elevation and temperature as the inputs, no runway length input but with a separate chart being used to compute the weight limited performance. I don't recall the name of that second chart, it was to do with balanced field length. I'm not a pilot so don't use them frequently, never use them in flightsim, but have used them occasionally as part of my job. Maybe everybody presents the charts the way Airbus do these days. I'm happy to concede I generalised where I shouldn't have.Kevin Hall

I'm sorry, but all this stuff made me head blog long ago.V1 is what the books tell you it is. Use your aircraft performance manuals, add your obstacle clearance factors/runway condition etc etc... And that's your V1.Follow the books, and your &@($* is covered. Pilots can't argue with that.In the meantime, take your arguement to pprune or something like that... Plenty of RW pilots able to chime in and help ya out.

I'm sorry, but all this stuff made me head blog long ago.V1 is what the books tell you it is. Use your aircraft performance manuals, add your obstacle clearance factors/runway condition etc etc... And that's your V1.Follow the books, and your &@($* is covered. Pilots can't argue with that.In the meantime, take your arguement to pprune or something like that... Plenty of RW pilots able to chime in and help ya out.

Please don't take it to pprune! already way too many simmers over there pretending to be pilots and arguing with 10000 hour captains. It is embarrassing.

Please don't take it to pprune! already way too many simmers over there pretending to be pilots and arguing with 10000 hour captains. It is embarrassing.

The irony is, there's pilots here arguing with an 18,000 hour captain...