Originally posted by Gabriel
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V1 is or is not a LOCATION on the runway...
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Seriously, what could be the holdup on this?
Gabriel, perhaps you could help me out here. Your maths and physics is far superior to mine. Firstly, are you able to tell me an approximate reduction in acceleration that would be required to remove the takeoff case buffer for an aircraft such as the EK Melbourne incident? So, in the case of the takeoff, that instead of the aircraft being at 35ft it is now at 0 ft at the end of the runway?
I'm interested to know in how small the change in acceleration has to be to make the aircraft use up all the buffer and actually become a real problem.
If we're talking very small accel changes between the two cases, I can imagine significant technical difficulty particularly in gusty conditions when the ground speed acceleration may not be uniform. The technical implementation may prove to be quite a challenge, and may be some of the reason we don't already see it.
Also - I think I started everyone off on the 'marker' idea. Please, please do not suggest this for operations. It was purely a theoretical idea that, while it would work in some cases, probably wouldn't have the safety effect needed to make it viable. I would, however, be very happy to see a 'hands off' "configuration" style warning in the cockpit. We don't need to increase workload any more in that phase of flight, but a "background" system that only alerts if something is wrong would be a good safety addition, if technologically feasible. It must be done at a low speed - something below 80kts.
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Originally posted by 3WE View PostActually, you need to read the original post...the thread title is only a headline designed to spark interest in what's inside.
Better ?
It's still a speed though. It just happens somewhere on the runway ? This from Wikipedia and verified .......
V1 is the critical engine failure recognition speed or takeoff decision speed. It is the decision speed nominated by the pilot which satisfies all safety rules, and above which the takeoff will continue even if an engine fails.[9] The speed will vary between aircraft types and also due to aircraft weight, runway length, wing flap setting, engine thrust used, runway surface contamination and other factors.
V1 is defined differently in different jurisdictions:
The US Federal Aviation Administration defines it as: V1 means the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.[7]
Transport Canada defines it as: Critical engine failure recognition speed and adds: This definition is not restrictive. An operator may adopt any other definition outlined in the aircraft flight manual (AFM) of TC type-approved aircraft as long as such definition does not compromise operational safety of the aircraft.[8]If it 'ain't broken........ Don't try to mend it !
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Originally posted by brianw999 View PostThe US Federal Aviation Administration defines it as: V1 means the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.
In other words, if V1 speed is not achieved by the V1 distance(*), then V1 doesn't comply with the definition of V1. That is, V1 becomes meaningless.
So yes, by definition, V1 is a speed, not a distance. But the "distance" part of it is critical to safety and has been grossly overlooked so far.
(*) The distance at which the plane is supposed to achieve V1.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View Post...by definition, V1 is a speed, not a distance. But the "distance" part of it is critical to safety and has been grossly overlooked so far...
I have to be honest that this thread really surprised me.
I expected a professional pilot to come on here and acknowedge that there was a theoretical flaw with V1, but to also cite procedures and statsitics that would assure that the V1 decision/process was ridicuolously safe.
Instead one professional pilot comes on and says, "yeah, there's a genuine technical flaw and we really ought to have an electronic acceleration check" while another professional pilot proclaims "this is how I've always done it, so therefore it's fine" while displaying some disturbing ignorance of the concept and other bits of aviation knowledge.
Amazing.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by MCM View PostGabriel, perhaps you could help me out here. Your maths and physics is far superior to mine. Firstly, are you able to tell me an approximate reduction in acceleration that would be required to remove the takeoff case buffer for an aircraft such as the EK Melbourne incident? So, in the case of the takeoff, that instead of the aircraft being at 35ft it is now at 0 ft at the end of the runway?
In the EK case, the airplane was 28% heavier than the TOW entered, so it was accelerating 28% slower. That alone made that it achieved any given speed farther down the runway than expected. But that was only part of the problem. The other part was that, being heavier, the speed needed to lift off was also faster. So it was accelerating slower and needed to achieve a faster speed.
BUT, EK had all its engines operative. Imagine if an engine had failed anytime after V1 (what is what V1 protects you from). We would be still counting bodies. So the margin over the engine failure case was much, much lower than 28%. And it's very difficult to calculate from the desk the distance it takes from Vr to lift-off to V2 and 35ft with an engine inoperative.
It's a bit easier to calculate for the ASD, if you have to abort at V1. The buffer there is 2 seconds at V1. You'll lose that margin if your acceleration is degraded about 10% for a heavy aircraft (V1 = 150kts, nominal acceleration 4kts per second) and 20% for a lightly loaded aircraft (V1 = 120kts, nominal acceleration 8kts per second).[/QUOTE]
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by 3WE View PostWhile another professional pilot proclaims "this is how I've always done it, so therefore it's fine" while displaying some disturbing ignorance of the concept and other bits of aviation knowledge.Amazing.
What is REALLY amazing is that this ignorant pilot just managed to fly 102 tons of freight from Cincinnati to Tokyo in 13 hours and didn't have to look at any markers on the side of the runway to make sure I got here O.K.
STOP TRYING TO REBUILD THE WHEEL!
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Originally posted by BoeingBobby View PostWhat is REALLY amazing is that this ignorant pilot just managed to fly 102 tons of freight from Cincinnati to Tokyo in 13 hours and didn't have to look at any markers on the side of the runway to make sure I got here O.K.
STOP TRYING TO REBUILD THE WHEEL!
It is almost predictable that sooner or later a heavy jet is going to mash into something immoveable because the pilots weren't aware of an input error or a takeoff performance issue. Most have far less experience on type than you and we need a line of defense there. Aside from having an experienced 'feel' for a certain type of aircraft under certain conditions, I don't see any.
So preemtive or reactionary? Which is your desired method of dealing with the issue? Because it is going to have to be one or the other.
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Originally posted by Evan View PostIt is almost predictable that sooner or later a heavy jet is going to mash into something immoveable again because the pilots weren't aware of an input error or a takeoff performance issue.
Most have far less experience on type than you and we need a line of defense there. Aside from having an experienced 'feel' for a certain type of aircraft under certain conditions, I don't see any.
And, the "feel" doesn't work except in extreme cases, as BB said, he can tell the take-off of a transpolar flight from one of a 100NM repositioning flight.
But yesterday's take off from today's in the same flight, with more or less the same load, more or less the same pressure, more or less the same temperature, and more or less the same wind? Will he be able to feel if the airplane is accelerating 10% slower than it should (we are talking of an error of half a knot per second), when he doesn't even exactly know how much it should been accelerating to begin with?
So preemtive or reactionary? Which is your desired method of dealing with the issue? Because it is going to have to be one or the other.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View PostFixed.
Originally posted by Gabriel View PostDon't exaggerate there. A good, robust procedure of independent calculations and correctly following it is a good line of defense. Good enough? I think not, but good.
Originally posted by Gabriel View PostAnd, the "feel" doesn't work except in extreme cases, as BB said, he can tell the take-off of a transpolar flight from one of a 100NM repositioning flight.
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Originally posted by Evan View PostI don't know of a massive fatality incident involving a heavy that was directly attributed to compromised take-off performance. That is typically what it takes to wake up the industry.
I don't see how that is a defense against all the other causes of degraded take-off performance.
It is almost predictable that sooner or later a heavy jet is going to mash into something immovable again because the pilots weren't aware of an input error or a takeoff performance issue. Most have far less experience on type than you and we need a line of defense there.I guess I was assuming he had Sweet Monkey River piloting skills.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by BoeingBobby View PostSTOP TRYING TO REBUILD THE WHEEL!Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by Gabriel View PostPlease define "massive" and "heavy". We have, for example, the Air Florida 737 in the Potomac River with a high death toll and a 747 that was luckily cargo so "only" all the 7 crew died. I know, you'll argue that the 737 was massive but not heavy and the 747 was heavy but not massive, so we are still in preemptive mode?
Air Florida was pilot error! Failure to use proper anti-ice procedures.
And the National 74 in Bagram was a load shift on T.O. How would you figure that this had to do with T.O. performance?
It is not. But I was answering this:
Oh, I'm sure he has. I think that BB must be one of the greatest pilots out there, together with ITS who is the original Sweet Monkey River pilot. But there are things that even the best pilot, or one even better than the best one, can't do.
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Originally posted by 3WE View PostSince you are old, I am sure you are aware that in the 1970's and 1980's tire constrtuction changed from predominately bias ply to radial construction...or are we having senility and memory issues?
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Originally posted by Gabriel View PostPlease define "massive" and "heavy". We have, for example, the Air Florida 737 in the Potomac River with a high death toll and a 747 that was luckily cargo so "only" all the 7 crew died. I know, you'll argue that the 737 was massive but not heavy and the 747 was heavy but not massive, so we are still in preemptive mode?
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