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Johan_Dees

Why isn't V1 depending on the RWY length?

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As I understand V1, it is a kind of point of no return. Once the aircraft has reached V1, there is no way to stop the take off roll in order not to overshoot the runway. But isn't this depending on the rwy length? E. g. to bring a 737 to a standstill from V1 might not be possible on a 6000 ft rwy, but I guess it is possible on a 13000 ft rwy.So wouldn't it therefor be logical to consider the rwy length when calculating V1?Wolfgang

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Boy Wolfgang, did you open a can of worms.... (smile)The FINAL V1 speed is dependant on a number of enviromental and operational concerns. The key concern being weight of the aircraft. In the US, major airlines produce charts (our carrier calls them "Runway Analysis") for each runway at each airport served in line-operations. In it there are charts for weights and temperatures for each runway as well as the "V" speeds. For off-line operations the dispatcher and Captain will walk through the calculations.To work within the parameters of a particular runway the aircraft may be "weight-limited" not only to meet rejected T/Off limits but also obstruction clearance, noise abatement, etc, etc.The V speeds are adjusted for runway conditions, slope, head-winds and some other voodoo. If the speeds don't match the minimum required then there are really only three adjustments we can make, different runway, different configuration or reduce weight.Timothy(Please don't ask about calculating "Balanced Field Lenght")

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Hey Timothy, you forgot the BFL stuff and the accelerate-go and accelerate-stop distances and the 115% and Vfail and....Oh.....you said "don't ask".....sorry. :-lol :-lolI am outta here. :-outta

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Thank you for your very detailed infos Tim!But considering everything you mentioned, couldn't it then happen that V1 is higher than Vr in some odd cases? ;)Wolfgang

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Well, it wasn't THAT detailed. I could have posted the full Flow Chart that looks like it was designed by a committee with too much time on their hands and too much caffiene in their blood.Southwest gived their crews laptop pc's (that could be used as a dinner tray if SWA ever gets around to meal service) for doing all the mental gymnastics.On the "line" I have never run across a point where VR was less than V1 (or Va was greater than Vr) that I can recall. However on the 727s it was very common that Vr and V2 where the same value.Timothy(Going back to planning on how to cut infront of Kathy in the pattern-CAUTION WAKE TURBULENCE)

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It is in the FARs somwhere - I think FAR105 ?? It states that VR cannot be less than V1. Hey, I have a great memory but it is short :)(Now going back to 3 mile separation - he's 1.5 miles from me - I'm 1.5 miles from him - that's 3 miles....right???)

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Is there a FAR 105? LOL-since when does the Legal World, Real World and Virtual World intersect in flying? Short memory??? you looked average height to me.....Of course Kathy is thinking that Wolfgang is in the United States and covered by FARs.....think global.As far as separation, I think Kathy's tiny Baron(?) needs 5 mile-in-trail from my "heavy". Of course if you are in front, I may be hanging on the flaps, but the view would be better for me (VBG-Wink) Timothy(If you aren't the lead sled-dog, the view never changes!)

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You could also look at it under the denomination perspective. V1 belongs to the aircraft's properties and depends on parameters dealing with flight dynamics, like the other Vs. What you are talking about would belong to the operations perspective. Not that the 2 are independent of course, but they are separated for convenience. Like the standard atmosphere thing, which nearly never happens, it's a conventional basis for comparisons and computations.

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It is what it is....Its matching the airplane's properties to the airfield's reqiurementsTimothy (diem Carpe or Daily Carp)

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Wolfgang,Your question is perfectly logical. I asked this question myself before too. I can see no one gave you a straight answer. Many pilots are not even aware of precise technicalities involved - they use precomputed tables, charts prepared by their airlines.Imagine 20,000 ft runway. It is easy to see that on such runway V1 could be a lot higher than V2 since there is so much room to stop !So what we are really talking about is not the absolute length of the runway but the so called "balanced-field" regime. What is the balanced filed ? It is the point during your takeoff roll when the amount of space required to stop your aircraft is EQUAL to the amount of space required (in case of a single engine failure) to reach VR and rotate. As you see from the above sentence runway length is not needed to calculate this point. Obviously you can only attempt takeoff when the runway is long enough that the balanced-field is satisfied. In other words the length of your runway must at least meet balanced-field criteria.I only speculate (I don't know for sure) that airlines do not take advantage of extra long runways that would allow for artificial increase of V1 - therefore your observation that v1/Vr is independent of runway length. Michael J.

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http://www.flightsafety.org/members/servem...d/fsd_oct98.pdfIt needs registration, but is free.or check here for quick access:http://people.zeelandnet.nl/johd/index2/FlightOps/v1.pdfHave fun flying!Johan[A HREF=http://www.phoenix-simulation.co.uk]Phoenix Simulation Software[/A]Unofficial PSS website:www.people.zeelandnet.nl/johdMy help may not me much usefull, or usefull much..eh?

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I know it is all very technical but at least the main principle:"accelerate-to-go" = "decelerate-to-stop"still holds.Thanks for the link.I am a technical kind of guy so "straight" answer for me may not be so straight for other. *:-*Michael J.

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As I recall, in the AIM (somewhere) it states that if Vr is reached first that V1 be called (even though V1 may not be yet attained).Bruce.

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>if Vr is >reached first that V1 be called (even though V1 may not be >yet attained). >Such scenrio is impossible if Balanced Field rules are adhered to (and this is what I believe everyone uses).Michael J.

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Surely you meant that V1 and Vr are the same on the 727.;)

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