Incidend during take off in Doha
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There goes you just said it yourself and it is not most it is all manufacturers and almost all SOP.
By the way what happen about this incident
any lead people ? Someone must know something! 
By the way what happen about this incident
any lead people ? Someone must know something!
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The problem with calling V1 at V1 is that if a moment before V1 there IS an issue, by the time your brain processes the information and action taken by reducing the throttles to idle, you will be in a situation that you are above V1 by the time the abort is initiated. Now all the data goes out the window and you can bet the final report will state that pilot aborted above V1.
That's why MANY carriers throughout the world have a practice of calling V1 at V1-5 kts. By doing this, you are reducing that window of decision making at highspeed to be in your favor. If in those 5 knots something DOES happen, by the time you process it and decide, you will be above V1.
There have been far too many accidents with high speed aborts, and the majority of times, taking off and coming back around would have resulted in a better result.
By the time your aural nerve processes the master warning, your eyes send the signal to your brain for an engine fire, your brain processes the signal to the hand to pull the throttles back to abort, you will be above V1. Take your life experiences in flying for what you will, but if I have a single engine fire at V1 - 5kts, we're taking off.
That's why MANY carriers throughout the world have a practice of calling V1 at V1-5 kts. By doing this, you are reducing that window of decision making at highspeed to be in your favor. If in those 5 knots something DOES happen, by the time you process it and decide, you will be above V1.
There have been far too many accidents with high speed aborts, and the majority of times, taking off and coming back around would have resulted in a better result.
So clowns, you would be happy to call V1 5 kts early and take a fire into the air. How bad is that ?
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And for those interested in high speed aborts near V1, look up the Columbia SC Learjet accident in 2008. Near V1 some of the main tires blew out. The FO, much more experienced than the CA in this case, instintively called out "Go, Go GO!" and the CA, much younger and lower time in experience, said "what have we got?" "uh, go?" "no" By the time the abort was initiated, they were FAR above V1. Of course, didn't help the thrust reverser squat switch was taken out by the tire rubber shrapnel, and pulling the TRs out actually resulted in forward thrust, killing all but two onboard.
The problem with calling V1 at V1 is that if a moment before V1 there IS an issue, by the time your brain processes the information and action taken by reducing the throttles to idle, you will be in a situation that you are above V1 by the time the abort is initiated. Now all the data goes out the window and you can bet the final report will state that pilot aborted above V1.
There is sufficient time to recognize and take the first action of an RTO built into V1, such that you may in fact slightly exceed it during the actions, but still have sufficient runway to stop.
Similarly you may have a failure BEFORE V1, but with insufficient time to start the RTO, and still have enough runway to accelerate to Vr and achieve 35ft over the far threshold.
Being able to react within those time buffers is a skill required to pass your type rating.
Put it this way- if you are going to call V1 5 knots early, why not BUG a speed 5 knots slower and call THAT V1?
Well, the speed we calculate as V1 effectively does just this. Even on what we calculate as a perfectly balanced field, there is "Fat" on either side of V1 for a late RTO decision, or an early lack of detection and "Go" decision.
Adding fat to the fat doesn't make a lot of sense, as you are now in no-mans land. Do you KNOW you can make Vr before the end of the runway if you make an early "Go" decision?
Your Learjet example was an example of not achieving a timely or correct decision- firstly because "Go" is the recommended decision if you lose tires (as you also lose braking ability) and "What have we got" is not an appropriate question at any time during a takeoff roll!!
Where they between V1-5 and V1 when the tires blew?
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That is why you only abort for a few major failure at high speed, indeed you brief it if it's above 70knts or 100knts. We brief any red lights and lost of directional control. Otherwize GO!
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Sittingidly, where are you getting 5 Seconds from?
At that stage in a takeoff you are accelerating at approx 7kts per second, so the concept is that as you finish saying V1, you will have reached that speed. During training in Seattle, Boeing told us that Lufthansa had introduced this procedure.
Mutt
If you call V1 early and something nasty happens in those 5 seconds, and you continue the takeoff
Mutt
Last edited by mutt; 10th Nov 2011 at 11:01. Reason: Correction of acceleration
so 420knts/min... 
anyway this threat has turn to a real smart ass conversation. 
At that stage in a takeoff you are accelerating at approx 7kts per second per second, so the concept is that as you finish saying V1, you will have reached that speed. During training in Seattle, Boeing told us that Lufthansa had introduced this procedure.
Surely if the manufacturer wanted the V1 call to start prior to the speed, it would have installed a device that did just that?
Fact is, I doubt the second or so difference 5 knots is going to make would ever be the difference between success or failure.
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Fack5:
You are correct in pointing out that 7kts/s/s represent
However, I would presume the second '/s' was simply a typo.
You'll notice Wizofoz made the same assumption and correctly converted a 7kts/s (ie nautical mile/second/second) acceleration into a meter/second/second acceleration. Comparing this to 9.8 m/s^2, the acceleration due to earths gravity (ie 1g), I tend to agree with the statement that
You are correct in pointing out that 7kts/s/s represent
an increase in the rate of acceleration
You'll notice Wizofoz made the same assumption and correctly converted a 7kts/s (ie nautical mile/second/second) acceleration into a meter/second/second acceleration. Comparing this to 9.8 m/s^2, the acceleration due to earths gravity (ie 1g), I tend to agree with the statement that
a little over 1/3g, so no, nothing neck-snapping.
Fact,
I see where you're coming from, yes I assumed (and did my figures) based on Knots/sec (thanks TCOC, It would be NM/hr/s in fact!!)
Yes, DELTA acceleration of 7kts/s/s would be pretty spectacular, and achievable only by the after burning vesion of the GE-90!!!!
Still, as all I did was turn the figures into what the poster originally meant, do you really think the derogatory comment was necessary?
Mutt,
No probs!
I see where you're coming from, yes I assumed (and did my figures) based on Knots/sec (thanks TCOC, It would be NM/hr/s in fact!!)
Yes, DELTA acceleration of 7kts/s/s would be pretty spectacular, and achievable only by the after burning vesion of the GE-90!!!!
Still, as all I did was turn the figures into what the poster originally meant, do you really think the derogatory comment was necessary?
Mutt,
No probs!
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It would be NM/hr/s in fact!!
You're right. As for the alleged incident: The lack of posts providing insight and details to the even suggests perhaps this was a rumour, and nothing but.
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V1 calculations take this into consideration.
There is sufficient time to recognize and take the first action of an RTO built into V1, such that you may in fact slightly exceed it during the actions, but still have sufficient runway to stop.
Similarly you may have a failure BEFORE V1, but with insufficient time to start the RTO, and still have enough runway to accelerate to Vr and achieve 35ft over the far threshold.
Being able to react within those time buffers is a skill required to pass your type rating.
Put it this way- if you are going to call V1 5 knots early, why not BUG a speed 5 knots slower and call THAT V1?
Well, the speed we calculate as V1 effectively does just this. Even on what we calculate as a perfectly balanced field, there is "Fat" on either side of V1 for a late RTO decision, or an early lack of detection and "Go" decision.
Adding fat to the fat doesn't make a lot of sense, as you are now in no-mans land. Do you KNOW you can make Vr before the end of the runway if you make an early "Go" decision?
Your Learjet example was an example of not achieving a timely or correct decision- firstly because "Go" is the recommended decision if you lose tires (as you also lose braking ability) and "What have we got" is not an appropriate question at any time during a takeoff roll!!
Where they between V1-5 and V1 when the tires blew?
There is sufficient time to recognize and take the first action of an RTO built into V1, such that you may in fact slightly exceed it during the actions, but still have sufficient runway to stop.
Similarly you may have a failure BEFORE V1, but with insufficient time to start the RTO, and still have enough runway to accelerate to Vr and achieve 35ft over the far threshold.
Being able to react within those time buffers is a skill required to pass your type rating.
Put it this way- if you are going to call V1 5 knots early, why not BUG a speed 5 knots slower and call THAT V1?
Well, the speed we calculate as V1 effectively does just this. Even on what we calculate as a perfectly balanced field, there is "Fat" on either side of V1 for a late RTO decision, or an early lack of detection and "Go" decision.
Adding fat to the fat doesn't make a lot of sense, as you are now in no-mans land. Do you KNOW you can make Vr before the end of the runway if you make an early "Go" decision?
Your Learjet example was an example of not achieving a timely or correct decision- firstly because "Go" is the recommended decision if you lose tires (as you also lose braking ability) and "What have we got" is not an appropriate question at any time during a takeoff roll!!
Where they between V1-5 and V1 when the tires blew?
"Built in" , but no specific numbers and guidance on exactly how much it's built in. Our book specifically states that by latest at V1, you have to take the first action (throttles to idle) and brake. Anything other than that, the NTSB will make note, and the media will drag you, your name, and your family, to hell.
It's amazing how many are contemplating a high speed abort and justifying it that it is okay and stoppable as long as I pull the power back a hair after V1. Not sure what your book states, but ours has constantly changed when they learned that pilots will abort for stupid reasons. They even took out "master warning" as a reason for abort. Now the only criteria is "the preception that the aircraft is UNABLE or UNSAFE to fly." Some people really need to think deep and hard about that. In my particular airplane, there isn't a single master caution I'd abort for in the highspeed regime. As for Master warnings, I wouldn't abort for one in the V1-5knot regime. As for your suggestion of bugging V1 to V1-5, I would say leave V1 as V1. Problem is when you bug a speed, people take that speed as the new measure and act accordingly for callouts. For example, for landing, we used to bug Vref "+ factor" during gusty winds, factor would be +5 knots. If landing speed was Vref 140, then 145 would be bugged with the factor. But what FOQA found for the most part, people would always stay a little above the speed bug during gusty winds. One runway overrun incident later, the procedure was changed to just "bug Vref" and fly up to 5 kts faster if necessary but cross over runway at vref.
"Built in" , but no specific numbers and guidance on exactly how much it's built in. Our book specifically states that by latest at V1, you have to take the first action (throttles to idle) and brake. Anything other than that, the NTSB will make note, and the media will drag you, your name, and your family, to hell.
There are in fact very specific numbers buit in,and the guidance is exactley as you state-you must be able to perform the first action of the RTO by V1 or continue. I don't think anyone is suggesting otherwise.
But, similarly, if you take an Engine Failure into the air, having detected the failure sufficiently early to initiate by V1, you are now eating into the safety factors in THAT side of your performance.
Out of interest, how often do you have a performance limited Take-off in your operation? If you are well below performance limited RTOW, you may well be confident you can achieve the necessary performance. When field length limited, remember it's only 35ft over the end of the clear way, and 15 when it's wet!
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Sitting ildly,
"It is a critical call. "
And you are right. It is! But imagine this scenario. Your V1 is 140. At 138 knots, you have a master warning for an engine fire. Both you and the FO will undoubtly take at least a quick peak at the screen to see the failure. By that time, you will be already above V1. Your initial action of pulling the throttles back will come 'late' as defined by NOT having them pulled by 140 knots (V1) in your case.
The closer you get to the V1 value itself, the less time you have to decide and initiate the abort. That is again why many carriers have you call out V1 at V1 - 5kts. That is a good value in which if you catch your engine fire at 134 knots, there's a good chance you can have the throttles to idle by 140 knots (V1) and now be "legal" (at least on paper) to stop.
Anyone entertaining a stop at V1 needs to keep in mind the law of kinetic energy. It is equal to mass times velocity squared. Your energy increases at the square value of your speed. That graph shoots off the charts at high speed values. You better have pulled the throttles back at V1 and not a knot late. There is what's written on paper, and then there's real world as you watch the runway go right by you as you attempt to stop. A RJ crew tried a high speed abort on a 6,300 ft runway. EMAS saved them. Otherwise, had that not been there, they would have been a smoking hole at the bottom of a cliff.
"It is a critical call. "
And you are right. It is! But imagine this scenario. Your V1 is 140. At 138 knots, you have a master warning for an engine fire. Both you and the FO will undoubtly take at least a quick peak at the screen to see the failure. By that time, you will be already above V1. Your initial action of pulling the throttles back will come 'late' as defined by NOT having them pulled by 140 knots (V1) in your case.
The closer you get to the V1 value itself, the less time you have to decide and initiate the abort. That is again why many carriers have you call out V1 at V1 - 5kts. That is a good value in which if you catch your engine fire at 134 knots, there's a good chance you can have the throttles to idle by 140 knots (V1) and now be "legal" (at least on paper) to stop.
Anyone entertaining a stop at V1 needs to keep in mind the law of kinetic energy. It is equal to mass times velocity squared. Your energy increases at the square value of your speed. That graph shoots off the charts at high speed values. You better have pulled the throttles back at V1 and not a knot late. There is what's written on paper, and then there's real world as you watch the runway go right by you as you attempt to stop. A RJ crew tried a high speed abort on a 6,300 ft runway. EMAS saved them. Otherwise, had that not been there, they would have been a smoking hole at the bottom of a cliff.
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When a pilot adds his personal preference of making the call 5kts early, then either he has decided to use that number as a standard, regardless of acceleration rates, or he is hopefully following company SOP's. If not, then he is performing an action which is critical, in the wrong manner.
I have never come across any document that says we should call V1 early or even anything that says it is allowable.