LY744
Topic Author
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V1 Speeds Out Of A Speedbook

Sun Feb 08, 2009 9:17 pm

How come V1 speeds are depicted in speedbooks as a function of TOW only, shouldn't the length of the actual runway used play a part in figuring out the appropriate V1? Do the tables just assume accelerate-stop distance = take-off distance at that particular weight?


LY744.
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Goldenshield
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RE: V1 Speeds Out Of A Speedbook

Sun Feb 08, 2009 10:31 pm

The actual runway length IS is used to determine V1. However, it is only a baseline V1. Other factors, such as runway slope, wind, etc., will influence V1.

Of course, for the purpose of this topic, the number in the flip books are all based on weights, as the maximum weights for the flight (which includes maximum takeoff weight for a given runway, 2nd segment climb, enroute driftdown, and maximum landing weight) are figured out during the pre-flight planning stage. And to answer your second question, ASDA is NOT used for takeoff distance, but rather the takeoff distance required is 115% that of the takeoff runway distance available where the plane must reach a minimum of 35 feet above the runway plane.

That's with U.S. regs. Other counties may vary.

[Edited 2009-02-08 14:46:12]
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tdscanuck
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RE: V1 Speeds Out Of A Speedbook

Mon Feb 09, 2009 3:26 am



Quoting LY744 (Thread starter):
How come V1 speeds are depicted in speedbooks as a function of TOW only, shouldn't the length of the actual runway used play a part in figuring out the appropriate V1?

If you have more runway than you need for a balanced-field takeoff, you can take it into account. Then it's an improved climb takeoff. That's usually done via computer, not by books.

Quoting LY744 (Thread starter):
Do the tables just assume accelerate-stop distance = take-off distance at that particular weight?

The normal approach is accelrate+RTO distance = accelerate+single-engine takeoff distance. That's the normal definition of a balanced field takoff...this is why airplanes almost never use the whole takeoff-distance-required length (the accelerate+two-engine takoff is shorter than either of the balanced field lengths).

When you throw all the other regulations in there, you may be limited by something other than the balanced field length (e.g. V1 can't be higher than VR, you may have an engine-out climb gradient limit, an obstacle limit, V1 can't be lower than Vmcg, etc.).

Tom.
 
LY744
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RE: V1 Speeds Out Of A Speedbook

Mon Feb 09, 2009 4:16 pm

Alright, I threw a spreadsheet together and I see what you guys are saying. Thanks!


LY744.
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411A
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RE: V1 Speeds Out Of A Speedbook

Mon Feb 16, 2009 1:09 am



Quoting Tdscanuck (Reply 2):
That's usually done via computer, not by books.

Improved climb (overspeed takeoff) speeds are available in the AFM (on Lockheed and Boeing airplanes) if one cares to look.

Also, on specific runway analysis charts.

'Computer' not necessary...only an ability to read and understand.
 
tdscanuck
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RE: V1 Speeds Out Of A Speedbook

Mon Feb 16, 2009 4:17 am



Quoting 411A (Reply 4):
Improved climb (overspeed takeoff) speeds are available in the AFM (on Lockheed and Boeing airplanes) if one cares to look.

True, but I've never seen or heard of the AFM being used to do an improved climb takeoff calculation in normal commercial service. It's either the FMC, the EFB, or dispatch using a software tool.

Tom.

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