V1 is or is not a LOCATION on the runway...

[AA 1818]

The other side of the coin is that, often too, V1 is the latest where you can reject and stop or the soonest you can accept an engine failure and still go, or you'll likely complete your stop or take-off beyond the runway limits.

Not going off topic any more - just this once; MIND. BLOWN!!!

[MCM]

Seriously, what could be the holdup on this?

I would actually suggest that it is only now (well, relatively recently) that this is becoming practical to implement. It is the way modern aircraft use derated thrust (I know you'll object to this use of the term, but it is a valid use. Just pretend I said Flex or 'Reduced thrust takeoff using the assumed temperature method' ) and increasing use of computer-derived takeoff performance that makes it a go-er so to speak. Although reduced thrust takeoffs have been around for a very long time, we're now being a lot more accurate with their use as the cost savings have become noticeable. The flip side of that is the large buffers that used to exist are not there, and more takeoffs are being done towards their limits.

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.

[brianw999]

Actually, you need to read the original post...the thread title is only a headline designed to spark interest in what's inside.

Ok then, I'll be EVEN MORE accurate.... "V1 is or is not a location on the runway ...where you make a go/no-go decision?

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]

[Gabriel]

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.

The FAA forgot to add: "... assuming that the airplane's performance is the one it should be". If V1 is not achieved by a given point down the runway (the point where the assumed performance indicates it), then aborting before V1 will not guarantee that the airplane will stop within the accelerate-stop distance and continuing a take-off with an engine failure after Vef will not guarantee that the airplane will achieve the required height above the runway 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.

[3WE]

...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...

Not sure about the "grossly" part- That would be another one of those great summary statements.

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.

[Gabriel]

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?

That's impossible for me to answer. There are so many variables.
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]

[BoeingBobby]

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.

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!

[Evan]

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!

The thing is BB, in 2009 an Emirates A340 with 257 items of living breathing self loading freight missed a brick building by less than 2 feet. If it had hit that building we would definitely be rebuilding the wheel. Why does it always have to come to that? Before AF447 we had a score of upper atmospheric UAS incidents, baffled pilots unaware of procedures and nobody wanted to rebuild that wheel. Then a whole lot of people diasappeared into the Atlantic and the industry woke up to a number of problems.

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.

[Gabriel]

It 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.

Fixed.

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.

Don'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.

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.

At this point, with a lot of incidents that compromised safety, several non-fatal accidents, and a few fatal ones, with more than 60 patents filled since 1956, and the NTSB and similar agencies around the world making a lot of recommendations for this since 1971, I'd say that, no matter what, we are already pretty much in reactionary mode.

[Evan]

Fixed.

I 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.

Don'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.

I don't see how that is a defense against all the other causes of degraded take-off performance.

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.

I guess I was assuming he had Sweet Monkey River piloting skills.

[Gabriel]

I 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.

Please 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?

I don't see how that is a defense against all the other causes of degraded take-off performance.

It is not. But I was answering this:

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.

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.

[3WE]

STOP TRYING TO REBUILD THE WHEEL!

Since 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?

[BoeingBobby]

Please 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.

Curious, Are you still in touch with ITS? I would love to have his input on this.

[BoeingBobby]

Since 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?

Not going to go down this path again!! And learn to use spell check would you!

[Evan]

Please 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?

It seems to me that until a large capacity passenger aircraft is involved with hundreds of lives lost, nothing seems to motivate the industry to deal with this kind of issue.