V1 rejects with decreasing performance

V1 is an accelerate go or stop. The key is which is longer. Your tab data will give you a v1 with a take off field length. That field length will allow go or stop. You just don't know which one is the limiting distance.
 
As stated earlier in this thread V1 is V1. Most tab data will show you when a balanced field is not available but won't necessarily tell you is it's because of Accelerate-Stop or Accelerate-Go.

Let’s take a non-specific multi-engine airplane (because the actual numbers are irrelevant) during the takeoff phase:
Using my Operating Manual, I figured based on the temp, PA, Wt, wind, etc. that I need 1,800’ of runway to make my takeoff. The available runway is 2,000’ but I have a 1,000’ clearway (total of 3,000’ for takeoff calculations).
Do I have Accelerate-Go distance? Absolutely. Do I have Accelerate-Stop distance? Maybe.

If hit V1 about 1,600’ down the runway and abort the takeoff at exactly V1, do I have the runway distance to stop? Not a chance. V1 does NOT “guarantee” that I’ll have the distance to stop on the runway. It’s just a speed at which I should make the decision to try to stop or go airborne.

If I have a RUNWAY that is 3,000’, then I might have both Accelerate-Stop AND Accelerate-Go…That would be a Balanced Field. These distances will vary based on the specifics of the plane and runway and environmental conditions.

Many operators will only utilize airfields that will meet balanced field criteria regardless of the plane’s operating weight, environmental and runway conditions. In these situations, you could consider V1 as a “guarantee” that you can stop on the runway.

Also, some certification requirements (Part 25 comes to mind) and some aircraft manufacturers place limitations on runway distances. They specify the reaction time of the pilot(s), all engines are operational, runway conditions and that the brakes are at the overhaul limit when stating the runway distances required. The certification requires that you’ll have runway available to stop if you abort at V1.

However, that’s not V1 specific as much as it is operational specific. If you step out of the protection of these operations, then you would have to compute the required distances as the conditions change.
 
Dugie8 said:
We are talking part 25 jets.
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Let me expand on that. I have a little time in King Airs so my memory may be off. I seem to recall you had to have accelerate stop ability but no accelerate go, this via the AFM. Now with part 25 jets (I say jets to simplify the discussion) your AFM will limit you to a take off weight that allows you to either:
A 115% of the take off run, both engines
B Accelerate to V1, lose an engine and stop
C Accelerate to V1, lose an engine continue the take off and climb to 35 by the departure end of the runway/clearway
D Structural limit

Your required runway is the longest or A, B or C. The book never really tells you which one your take off data is predicated on. But, knowing that the take off distance in the tab data (or performance computer output) is giving you the longest of those three, at V1 you are "guaranteed" to stop on the runway, assuming you used a runway that was at least as long as your data says.

Balanced field lenght is when accelerate go and accelerate stop are the same distance. I've been taught that changing v1 and/or engine power (flex power) achieve this. This gives you a more manageable high speed abort and also gives you, I'm not sure how to word it, more options when takeing off. ie, you can lose the engine at lower speeds and still go, not having to delve into that danger zone of aborts above 80 knots.

All runways and conditions aren't static or the same day to day, the BFL is the "SHORTEST" runway you have this, runways longer than that are just gravy.
 
Our paper take off and landing data each flight (if we don't have ACARS) shows us the limiting factor for our MAX V1. If the speed book gives us a lower speed, it's all good, but if it's higher, we are restricted to using the MAX V1 off the TLR. It also says what causes the restriction. There are 4 categories, which I can't remember right now, but I think they are things like "field" and "obstacle".

Also, do you have that documentation that says a clearway can't be used for a takeoff calculation for a part 25 certified aircraft? I had that very discussion with a sim guy once (after we rejected 10 prior to V1 in the sim and still went off the end of the runway by a whole bunch). He said it was fine because there is a 1000 foot clearway we are allowed to use per our calculations. All our books say is that the "runway" must accommodate the V1 number for accelerate stop/go and 115% of the takeoff run. It doesn't define "runway" anywhere.
 
I have to side with Dugie8, here. Part 25 jets are very much required to be able to stop from V1. Part 25.107 defines V1 as:

25.107 said:
(2) V1, in terms of calibrated airspeed, is selected by the applicant; however, V1may not be less than VEFplus the speed gained with critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's initiation of the first action (e.g., applying brakes, reducing thrust, deploying speed brakes) to stop the airplane during accelerate-stop tests.
Click to expand...

25.109 goes into even more detail: http://ecfr.gpoaccess.gov/cgi/t/tex...view=text&node=14:1.0.1.3.11.2.155.12&idno=14

Also, 121.189 is quite clear that accelerate-stop distances must be complied with (see (c)(1)): http://ecfr.gpoaccess.gov/cgi/t/tex...v8&view=text&node=14:3.0.1.1.4.9.2.10&idno=14

BobDDuck said:
Our paper take off and landing data each flight (if we don't have ACARS) shows us the limiting factor for our MAX V1. If the speed book gives us a lower speed, it's all good, but if it's higher, we are restricted to using the MAX V1 off the TLR. It also says what causes the restriction. There are 4 categories, which I can't remember right now, but I think they are things like "field" and "obstacle".

Also, do you have that documentation that says a clearway can't be used for a takeoff calculation for a part 25 certified aircraft? I had that very discussion with a sim guy once (after we rejected 10 prior to V1 in the sim and still went off the end of the runway by a whole bunch). He said it was fine because there is a 1000 foot clearway we are allowed to use per our calculations. All our books say is that the "runway" must accommodate the V1 number for accelerate stop/go and 115% of the takeoff run. It doesn't define "runway" anywhere.
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121.189 also seems to address the use of a clearway/stopway in accel-stop determination (seems that it's legit).
 
Clearway most certainly be used for takeoff calculations for a Part 25 aircraft. For performance calculations, there are 3 lengths that we give a damn about

TODA - Takeoff Distance Available = Length of runway and clearway
TORA - Takeoff Run Available = Length of runway only
ASDA - Accelerate Stop Distance Available - length of runway and stopway

The Runway you're talking about is the TORA.

It sounds like you have AeroData. There are 7 limitation codes you'll usually see:

O = obstacle, where the net flight path clears an obstacle by the required 35 ft margin
F = field length limit, where your accel-stop or accel distances required equal the TORA available
A = AFM limitation
C = 2nd segment climb
V = Vmcg limited (about the only time I see it on my airplanes is when I am anti-skid inop)
T = tire speed limited
B = brake energy limited
 
Dugie8 said:
We are talking part 25 jets.
Click to expand...

That's what I was saying earlier. Your talking about using V1 under a specific operation and I'm talking specifically about V1.

This has been a good conversation as I have learned a lot from this....
 
dispatchguy said:
Clearway most certainly be used for takeoff calculations for a Part 25 aircraft. For performance calculations, there are 3 lengths that we give a damn about

TODA - Takeoff Distance Available = Length of runway and clearway
TORA - Takeoff Run Available = Length of runway only
ASDA - Accelerate Stop Distance Available - length of runway and stopway

The Runway you're talking about is the TORA.

It sounds like you have AeroData. There are 7 limitation codes you'll usually see:

O = obstacle, where the net flight path clears an obstacle by the required 35 ft margin
F = field length limit, where your accel-stop or accel distances required equal the TORA available
A = AFM limitation
C = 2nd segment climb
V = Vmcg limited (about the only time I see it on my airplanes is when I am anti-skid inop)
T = tire speed limited
B = brake energy limited
Click to expand...

Are you absolutely positive about that? I'm not so sure. I don't say that to be confronational, I say that from looking at the 10-9 charts (jepp) that your definitions don't seem to jive with what the chart shows?? BUUUUT my memory could be faulty.
 
Dugie8 said:
Are you absolutely positive about that? I'm not so sure. I don't say that to be confronational, I say that from looking at the 10-9 charts (jepp) that your definitions don't seem to jive with what the chart shows?? BUUUUT my memory could be faulty.
Click to expand...

Those match up with our FOM.
 
Your carrier rules might prevent you from using stopway and clearway, however, those distance definitions are what Boeing and Airbus use in their performance engineering programs when defining runway distances, and non-balanced fields.

And as far as the AeroData definitions, for Part 25 large turbojet powered type aircraft, yes.
 
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