Calling V1 five knots early?

ibumblebee said:
I always thought that technique was the personalized/company-centric method in which you accomplish a procedure.
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Yeah... I'm not sure what he's getting at. If company poi approves V1 instead of V1-5 as Boeing recommends that's what you do.

My God I have too many Mesaba stories... at Mesaba FOs did the aborts on the Saab (and avro i believe) because the FOs had been there forever, some were ex captains, and Mesaba embraced an egalitarian culture of a benevolent dictatorship. Now, about 07 one of our FOs aborted at 95ish knots for a failed oil pressure gauge so we changed that procedure to the recommended procedure of CA always does abort.

Anyhow, i think the FO was a new FO just out of seminole diapers or some such stuff. For all I know he was a Ameriflight CA... *rimshot* too soon?
 
Have had a gander back into the 737 FCTM - this discussion is particularly pertinent:

When the takeoff performance in the AFM is produced, it assumes an engine failure or event one-second before V1. In a runway limited situation, this means the airplane reaches a height of 35 feet over the end of the runway if the decision is to continue the takeoff.

Within reasonable limits, even if the engine failure occurs earlier than the assumed one second before V1, a decision to continue the takeoff will mean that the airplane is lower than 35 feet at the end of the runway, but it is still flying. For example, if the engine fails 2 seconds before V1 and the decision is made to go, the airplane will reach a height of 15 to 20 feet at the end of the runway.

Although training has historically centered on engine failures as the primary reason to reject, statistics show engine thrust loss was involved in approximately one quarter of the accidents, and wheel or tire problems have caused almost as many accidents and incidents as have engine events. Other reasons that rejects occurred were for configuration, indication or light, crew coordination problems, bird strikes or ATC problems.

It is important to note that the majority of past RTO accidents were not the result of an RTO initiated because of an engine failure. Full takeoff thrust from all engines was available. With normal takeoff thrust, the airplane should easily reach a height of 150 feet over the end of the runway, and the pilot has the full length of the runway to stop the airplane if an air turnback is required.
 
I have it handy on the shelf for a reason. Always thought one should intimately understand what your performance means in reality.

I understand an eBook is in development for it. It was mentioned by the publisher on PPRuNe a while back.
 
Joshwa said:
I have it handy on the shelf for a reason. Always thought one should intimately understand what your performance means in reality.

I understand an eBook is in development for it. It was mentioned by the publisher on PPRuNe a while back.
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I'm going to look for something similar and equally authoritative; I'm curious.
 
Joshwa said:
When the takeoff performance in the AFM is produced, it assumes an engine failure or event one-second before V1. In a runway limited situation, this means the airplane reaches a height of 35 feet over the end of the runway if the decision is to continue the takeoff.

Within reasonable limits, even if the engine failure occurs earlier than the assumed one second before V1, a decision to continue the takeoff will mean that the airplane is lower than 35 feet at the end of the runway, but it is still flying. For example, if the engine fails 2 seconds before V1 and the decision is made to go, the airplane will reach a height of 15 to 20 feet at the end of the runway.
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thank you and this was my point (not so eloquently stated) that in an engine failure scenario, that the performance isn't guaranteed if take off is continued.
 
It is also worth noting that these issues are particularly critical on a wet runway. In the engine failure case on a wet runway, the screen height is only 15ft, and although you are guaranteed to be at V2 by 35ft, there is no assurance how far past DER you will be by then. Wet performance limits runways are much more marginal than you might think.
 
Joshwa said:
It is also worth noting that these issues are particularly critical on a wet runway. In the engine failure case on a wet runway, the screen height is only 15ft, and although you are guaranteed to be at V2 by 35ft, there is no assurance how far past DER you will be by then. Wet performance limits runways are much more marginal than you might think.
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Agree. This kind of stuff makes one realy miss arresting gear and a drag chute, luxuries indeed. While its always been known that wet runway numbers were marginal like you say here, it took having some in-depth example computations shown to me long ago to demonstrate just how marginal they are and can be.
 
NewYorkophile said:
Procedure = mandatory technique.
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You don't have SOTs, you have SOPs. That statement is a very far reach by the definition of technique.

@MikeD you're making complete sense, @Seggy is just arguing language semantics.

Before the manuals were written, Boeing/Airbus/whoever tried different techniques for flying the airplane. When they established the best ones, they made it procedure. /end
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If they established 'the best ones' then why doesn't everyone do it that way?
 
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Bumblebee said:
I always thought that technique was the personalized/company-centric method in which you accomplish a procedure.
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You can have different techniques within the company to accomplish a procedure.

Another way to look at this is that in a check ride environment you can't be held accountable for a technique as long as they accomplish the procedure. Hence why procedures are more fundamental than a technique is.
 
NewYorkophile said:
Again, language semantics, and I find it very difficult to believe you don't understand what we're all talking about.
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You (and others) are missing the point that procedures are more fundamental than techniques.



They do. Putting the gear down before landing is a *procedure*...or, should I say, a mandatory technique that the manufacturer decided would be a good idea.
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The Boeing manual feels it is 'best' to call V1 really at V1-5. They feel that is the best procedure and by your line of thinking should be a 'mandatory technique'. However, some airlines call V1 at V1. @MikeD would argue because that is their technique. Not sure what you would argue.

I would argue that the airlines feel that in their overall operating procedures, which ties into other aspects of their Flight Operations and operating philosophy, they have adopted the procedure to fit their need.
 
My guess, just to add fuel to the fire...

Boeing manual says "make V1 call no later than actual V1."

In the days of 707s and what not, it may have been UALs procedure to call V1 no later than actual V1. Then some guy moved up the rank and file, whose technique was to call V1 at V1-5. When he became director of training, he transformed his technique into procedure.

Now, whose side am I arguing for or against? Because I'm lost.
 
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