Hi Joel,“JAR/FAR 25.107V1, in terms of calibrated airspeed, is selected by the applicant; however, V1may not be less than VEF plus the speed gained with the critical engine inoperativeduring the time interval between the instant at which the critical engine is failed, andthe instant at which the pilot recognises and reacts to the engine failure, as indicatedby the pilot's initiation of the first action (e.g. applying brakes, reducing thrust,deploying speed brakes) to stop the aeroplane during accelerate-stop tests.”Regards,

so I guess you never read my post to the end or you would reply differently.please refer to my "Definition of V1" section, then you would understand what I am talking about.what I am reading (even now in Airbus Official Flight Operations Briefing Note), is that V1 is not selected by the applicant, but committed.

Now, to add a further level of complication to your little argument; Brake Energy.Even if you have a 40km runway, if you're going to fast and proceed to slam on the brakes, you run the risk of bursting a tire and going off the runway. V1, is always less than or equal to Vr. Imagine it like being on a motorway, the speed limit is 140kmph, you could do 160-180kmh if you wanted, it's possible due to the width and level surface, but that doesn't change the fact that 140kmph is still the maximum allowed speed for that road...Capt. Rónán O Cadhain.

Now, to add a further level of complication to your little argument; Brake Energy.Even if you have a 40km runway, if you're going to fast and proceed to slam on the brakes, you run the risk of bursting a tire and going off the runway. V1, is always less than or equal to Vr. Imagine it like being on a motorway, the speed limit is 140kmph, you could do 160-180kmh if you wanted, it's possible due to the width and level surface, but that doesn't change the fact that 140kmph is still the maximum allowed speed for that road...Capt. Rónán O Cadhain.

to refute that claim that it is somehow related to V1 definition, if I have 40Km of RW , I don't need/have to slam my brakes, I can just revert my throttles to idle and sit back and relaxuntil my plane comes to a complete stop without even touching my brakes (My Cessna Example above - Cessna on a 14,572ft RW at JFK)therefore this claim is not arguable for the definition of V1.

to refute that claim that it is somehow related to V1 definition, if I have 40Km of RW , I don't need/have to slam my brakes, I can just revert my throttles to idle and sit back and relaxuntil my plane comes to a complete stop without even touching my brakes (My Cessna Example above - Cessna on a 14,572ft RW at JFK)therefore this claim is not arguable for the definition of V1.

You're arguing with an airline pilot with 23 years experience, you do know that, don't you???

You're arguing with an airline pilot with 23 years experience, you do know that, don't you???

I do know that , but you never provided an answer to my claims/point I made. and I am sure you are the probably the most reliable answer (and probably could dig it out) that I can get, when it would be provided to my derect point I just made/asked.let's start with what is the definition of V1 , is it No.1 or No. 2? (my above post).if it's No.1 then you are right V1 is lower or equal to Vr.if it is No.2 then I am right and V1 could be grater then Vr, unless you provide me a logical answer that would refute it.or let's put it in simple words, is V1 a direct influence to the RW length or not? (enough RW to stop or not Enough RW to stop)

Straight from the Airbus manuals;V1: Decision SpeedV1 is the maximum speed at which a rejected takeoff can be initiated, in the event of anemergency. Additional information on this “Go/No-Go” decision can be found in theFlight Operations Briefing Note entitled: “Revisiting the Stop or Go Decision”.V1 is also the minimum speed at which a pilot can continue a takeoff after an enginefailure.If an engine failure is detected after V1, the takeoff must be continued. This implies thatthe aircraft must be controllable on ground. Therefore, V1 is always greater than VMCG.Happy Now?Edit: Although reading that definition, I'm not entirely satisfied by it, oh bother....

Edited November 18, 201114 yr by Rónán O Cadhain

HI Joel,V1 can never be greater than VR and it's by definitionJAR/FAR 25.107(e) VR, in terms of calibrated air speed, […] may not be less than:• V1,• 105% of VMCA• The speed that allows reaching V2 before reaching a height of 35 ft abovethe take-off surface, or• A speed that, if the aeroplane is rotated at its maximum practicable rate,will result in a [satisfactory] VLOF”The V1 you may select (the applicant) will be between V1min and V1max. With V1min you'll be limited by the TOD with an engine failure. V1max you're limited by your ASD.So what you are saying that if you have a 40km runway your V1max will be limited by Max tire speed or VMBE and indirectly VR.

Straight from the Airbus manuals;V1: Decision SpeedV1 is the maximum speed at which a rejected takeoff can be initiated, in the event of anemergency. Additional information on this “Go/No-Go” decision can be found in theFlight Operations Briefing Note entitled: “Revisiting the Stop or Go Decision”.V1 is also the minimum speed at which a pilot can continue a takeoff after an enginefailure.If an engine failure is detected after V1, the takeoff must be continued. This implies thatthe aircraft must be controllable on ground. Therefore, V1 is always greater than VMCG.Happy Now?Edit: Although reading that definition, I'm not entirely satisfied by it, oh bother....

that is what I read also "AirbusSafetyLib_-FLT_OPS-TOFF_DEP_SEQ07.pdf"however I also remembering the RW length (enough to stop or not enough RW to stop) is also part of this.now if RW length has nothing to do with V1 and as you 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.

I cannot believe you guys are arguing about this. Ronan, as a professional don't let yourself get dragged into such a pointless argument on a flightsim forum.

So what you are saying that if you have a 40km runway your V1max will be limited by Max tire speed or VMBE and indirectly VR.

that what it seems like... and no one could approve it or disapprove it with a reasonable answerapart from saying "it's the rule", no one could explain why it's the rule especially when I gave the Cessna example here.I don't know about Max tire speed or VMBE , but for sure I know that Vr would not exceed it (normal operation every time you take off, doesn't make scene that Vr would exceed those limitations on a daily bases) , henceit could not be part of the argument of V1 being grater then Vr.to make it more simple, let's say that Vr is 130kt and max tire speed/Vmbe is 150kt and V1 based on the RW i got left is 140kt, so V1 is grater , and Vmbe is not part of the argument, since I never reached it.now you would probably say "but V1 can't be 140 if Vr is 130... so I refer you again to my Cessna Example above on why one is possible)

HI Joel,V1 can never be greater than VR and it's by definitionJAR/FAR 25.107(e) VR, in terms of calibrated air speed, […] may not be less than:• V1,• 105% of VMCA• The speed that allows reaching V2 before reaching a height of 35 ft abovethe take-off surface, or• A speed that, if the aeroplane is rotated at its maximum practicable rate,will result in a [satisfactory] VLOF”The V1 you may select (the applicant) will be between V1min and V1max. With V1min you'll be limited by the TOD with an engine failure. V1max you're limited by your ASD.So what you are saying that if you have a 40km runway your V1max will be limited by Max tire speed or VMBE and indirectly VR.

There you go, that's your definition there for you. As Rob pointed out, I can't believe I'm getting into this discussion [or argument more like], Now, I've a flight to catch, good day to yee all...Capt Rónán O Cadhain.

I cannot believe you guys are arguing about this. Ronan, as a professional don't let yourself get dragged into such a pointless argument on a flightsim forum.

the argument would had stopped if a reasonable / Logical reason was provided.however one could approve it or disapprove it with a reasonable answerapart from saying "it's the rule", no one could explain why it's the rule especially when I gave the Cessna example here.

There you go, that's your definition there for you. As Rob pointed out, I can't believe I'm getting into this discussion [or argument more like], Now, I've a flight to catch, good day to yee all...Capt Rónán O Cadhain.

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.

VMBE is often limiting on some aircraft, particually when operating on runways with a downward slope.Also.... It's wrong and incorrect to think of VMBE being a given tyre speed... EG this aircraft has a VMBE of xx kts.It is a dynamic value that changes for every takeoff, just one of the many items that in the end define the V1 and VR speeds.This is a HUGE topic.... we could get into how the OCTOPUS / BPS software is able to play with these values for an improved takeoff weight, but I think that might be a little deep!

that what it seems like... and no one could approve it or disapprove it with a reasonable answerapart from saying "it's the rule", no one could explain why it's the rule especially when I gave the Cessna example here.I don't know about Max tire speed or VMBE , but for sure I know that Vr would not exceed it (normal operation every time you take off, doesn't make scene that Vr would exceed those limitations on a daily bases) , henceit could not be part of the argument of V1 being grater then Vr.to make it more simple, let's say that Vr is 130kt and max tire speed/Vmbe is 150kt and V1 based on the RW i got left is 140kt, so V1 is grater , and Vmbe is not part of the argument, since I never reached it.now you would probably say "but V1 can't be 140 if Vr is 130... so I refer you again to my Cessna Example above on why one is possible)

Hi Joel,VMBE is maximum brake energy and V1 has to be lower than that in order for the brakes to absorb the energy. Use this formula (1/2*TOW*squared(V1)).Vtire is the maximum tire speed. Vlof must be less than Vtire.now V Lift off or Vlof is the speed at which the tires leave the ground. This one is limited by Vmu. (110%)Now the Cessna example is interesting because first of all it's a single engine piston therefore it doesn't use V1. Second it's certified after a different rule set.it's ALL very well explained in this graf coutersy of AirbusRegards,

@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.