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Balanced Field Length, V-speeds

GravityHater

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I am trying to figure out why we do not adjust anything with respect to V speeds, when the runway is huge as in multiple so of the BFL.
Lets say the BFL is 3500' and the actual length is 12000' (I have experienced something similar).
Just past V1, still on the ground, you lose one - or have a fire. You are probably 2500' down the runway (CJ). All the training says Go..... but it seems like we ignore the fact that you can easily stop in these circumstances.
Tell me what I overlooked.
 

TransMach

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Overlooked? Nothing. You're right.

V1 decision speed only comes into play on an abort critical or obstical critical runway. If you've got room ... you've got room!. I like room ...

Just be certain you know what you're doing. Most folks don't.

In many of the advanced FMS/Perf systems you can adjust V1 to account for an abort critical or obstical critical situation. Older "Tab Data" on a checklist won't do it.

TransMach
 
Last edited:

Hugh Johnson

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Yep
It may also depend on what type of aircrat you fly. On the F900, V1/Vr are the same speed, so at the V1 call, you are removing your hand from the throttle, starting rotation and are effectively flying. When there is a significant delay between the two speeds, I have heard of pilots matching V1/Vr on a long runway.
 

BoilerUP

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You've overlooked nothing....but you are applying common sense and critical thinking to a situation.

Doing that removes you from the "train like you fly, fly like you train" mindset and could possibly cause you issues if you hesitate on a runway that is shorter.

If I bang an engine at V1 1/4 down a long runway, I know I'll have PLENTY of runway to return to for a OEI approach and landing...and I'll take those odds over the proven higher risk from a high-speed RTO any day.
 

fu69atacafyeah

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You've overlooked nothing....but you are applying common sense and critical thinking to a situation.

Doing that removes you from the "train like you fly, fly like you train" mindset and could possibly cause you issues if you hesitate on a runway that is shorter.

If I bang an engine at V1 1/4 down a long runway, I know I'll have PLENTY of runway to return to for a OEI approach and landing...and I'll take those odds over the proven higher risk from a high-speed RTO any day.


agreed! a high speed abort is no good on any runway.
 

ackattacker

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hah!
V1 can also be brake energy limited. Abort past V1 and you're no longer in the realm of the calculated and tested and certified performance. Prang it up and the FAA will crucify you. High speed, high weight abort, you don't really know what will happen. Blow the tires, depart the paved surface etc.
 

siucavflight

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I am trying to figure out why we do not adjust anything with respect to V speeds, when the runway is huge as in multiple so of the BFL.
Lets say the BFL is 3500' and the actual length is 12000' (I have experienced something similar).
Just past V1, still on the ground, you lose one - or have a fire. You are probably 2500' down the runway (CJ). All the training says Go..... but it seems like we ignore the fact that you can easily stop in these circumstances.
Tell me what I overlooked.
You become the test pilot if you abort after V1. If you continue the takeoff single engine after V1 the plane has proven to perform if you continue. High speed aborts can lead to some very ugly things.
 

sleepy

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It may also depend on what type of aircrat you fly. On the F900, V1/Vr are the same speed, so at the V1 call, you are removing your hand from the throttle, starting rotation and are effectively flying. When there is a significant delay between the two speeds, I have heard of pilots matching V1/Vr on a long runway.

Don't you mean V2 and Vr are the same speed in the DA-50 or DA-900? we always rotate at V2, not V1.
 

gear_guy

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You are referring to balanced field length. I am not sure what type airplane you fly, but V1 is adjustable in my airplane (G4).

If you are field limited you can use V1min (shortest accelerate stop-longest accelerate go).

Or when using a contaminated runway for example you may use V1max (longest accelerate stop-shortest accelerate go).

Check the AFM and see if it allows for changing V1. Using balanced field is fine most of the time, but it is not always the safest option. If you are not runway limited and don't feel good about high speed aborts you can use V1 min every time if you want. But I agree that you would be crazy to disregard the training you have received and choose to do something in the test pilot realm during an emergency. That is not the time to be jumping "outside the box", so to speak.
 

gear_guy

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Don't you mean V2 and Vr are the same speed in the DA-50 or DA-900? we always rotate at V2, not V1.

Wow your rotation and single engine climb speed are the same? I have never heard of that.
 

caseyd

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Wow your rotation and single engine climb speed are the same? I have never heard of that.

Long runway, light weights and computer generated speeds.... happens often. Not every time, but it happens.

We make the V1 call at V1 minus 5 so as to complete the call by V1 (premise being that as one approaches V1 the risks favor continuing).

I agree with previous posters that returning to a 10,000 runway is preferable to attempting to stop on what remains after a problem at V1, recognition occurs, action is taken and whatever result the circumstances allows occurs.

There is a value to having certain decisions made before one even climbs out of bed in the morning. No approaches unless minimums exist, no dispatch into icing worse than moderate, operable radar required when TRW's forcast, and no abort above 80 for anything except fire, failure, configuration warning or the unlikely perception that she won't fly are but a few examples. At V1 we are going flying no matter what lights or bells are going off.

caseyd
 

macdu

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Wow your rotation and single engine climb speed are the same? I have never heard of that.
Quite often have the same speeds. Just yesterday punched in the same V1, Vr, and, V2 speeds in a A320.
 

gear_guy

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Quite often have the same speeds. Just yesterday punched in the same V1, Vr, and, V2 speeds in a A320.

Hmm...Falcon..Airbus...

me thinks this has something to do with being french. Am I on to something?

Anyway that would be a mouthful to say at one time.
 

sleepy

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You are referring to balanced field length. I am not sure what type airplane you fly, but V1 is adjustable in my airplane (G4).

If you are field limited you can use V1min (shortest accelerate stop-longest accelerate go).

Or when using a contaminated runway for example you may use V1max (longest accelerate stop-shortest accelerate go).

Check the AFM and see if it allows for changing V1. Using balanced field is fine most of the time, but it is not always the safest option. If you are not runway limited and don't feel good about high speed aborts you can use V1 min every time if you want. But I agree that you would be crazy to disregard the training you have received and choose to do something in the test pilot realm during an emergency. That is not the time to be jumping "outside the box", so to speak.

Yes, we do the same thing in the Falcon, but normally V2 and Vr are the same speed for us. V1 and Vr are not normally the same speed. But I see the point.
 

snow-back

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Certification under FAR 25 requires that V1 must not exceed VR or the Max brake energy limit speed.
 

Gear Up!

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Enough
Regardless in any situation If you shell one at V1 you go. Even If you have a long runway and you THINK you have enough room to stop, I always go. This way there is no mind set in taking split second decisions and debating to go or stop. You could have a blown tire and take out the squat switch which would prevent t/r, ground spoilers, ect from being utilized. It prevents the risk of running off the end or departing the side of the runway. What is the harm of just taking it in the air? She will Fly, If you are within your weight limitations. On Shorter runways 5000 or less 90 knots is my abort speed. Anything after I take it in the air. But once again, I guess until we are in the situation, thats how the story goes..
 

snow-back

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Regardless in any situation If you shell one at V1 you go. Even If you have a long runway and you THINK you have enough room to stop, I always go. This way there is no mind set in taking split second decisions and debating to go or stop. You could have a blown tire and take out the squat switch which would prevent t/r, ground spoilers, ect from being utilized. It prevents the risk of running off the end or departing the side of the runway. What is the harm of just taking it in the air? She will Fly, If you are within your weight limitations. On Shorter runways 5000 or less 90 knots is my abort speed. Anything after I take it in the air. But once again, I guess until we are in the situation, thats how the story goes..

Unless your VR is 100 kts, if you lose an engine at 95 kts, you may not have the runway to take it in the air, especially if you're operating at or near a BFL condition. Otherwise, I agree with everything else you wrote.
 

NCherches

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You've overlooked nothing....but you are applying common sense and critical thinking to a situation.

Doing that removes you from the "train like you fly, fly like you train" mindset and could possibly cause you issues if you hesitate on a runway that is shorter.

If I bang an engine at V1 1/4 down a long runway, I know I'll have PLENTY of runway to return to for a OEI approach and landing...and I'll take those odds over the proven higher risk from a high-speed RTO any day.

Exactly... I have been known to increase my V1 to my VR speed at airports with 10K runways but NEVER reduce your V1 because of Ice, short runways, etc... I have seen guys do that too many times!
 
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