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Ryanair uses all the runway.

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Ryanair uses all the runway.

Old 12th Oct 2017, 23:29
  #81 (permalink)  
 
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You can market it any way you want however from start of rotation to end of runway is 5 seconds. Three seconds rotating till airborne (10 degrees pitch ish) then airborne for the 2 seconds before end runway. Whichever way you look at it that’s not cool!
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Old 12th Oct 2017, 23:32
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If my physics is correct, the formula for constant power from standstill is v=3/2*d/t, plug in d=2000m runway and t=38 seconds and we get a threshold speed of 153.5kt, plus/minus measuring error. That's the theory, anyway.

See later posts for criticism.

Last edited by Musician; 13th Oct 2017 at 14:22. Reason: corrected "acceleration"->"power", calculation is not as useful as I thought it was
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Old 12th Oct 2017, 23:32
  #83 (permalink)  
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I think that it is disappointing that so many professionals fail to recognise that this was not a normal take off.
Cannot understand why so many posters here are prepared to accept, as prima facie evidence, pictures from a hand held smart phone taken by a passenger, through a side window, without any hard evidence to back up their highly speculative conclusion, hope they are never in a jury, anywhere. Personally I seriously doubt the professional status claimed by these posters, as well as doubting their exposure to limiting, but totally legal, conditions.
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Old 12th Oct 2017, 23:34
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ASD
Sum of the distances necessary to:
Accelerate the airplane with all engines operating to V1 (assumes that first stopping actions are taken at V1)
With all engines still operating come to a full stop
Plus an additional distance equivalent to 2 seconds at constant V1 speed
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Old 12th Oct 2017, 23:52
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Originally Posted by parabellum
Cannot understand why so many posters here are prepared to accept, as prima facie evidence, pictures from a hand held smart phone taken by a passenger, through a side window, without any hard evidence to back up their highly speculative conclusion, hope they are never in a jury, anywhere. Personally I seriously doubt the professional status claimed by these posters, as well as doubting their exposure to limiting, but totally legal, conditions.
You clearly didn't pass your performance 'A'...Mate.
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Old 13th Oct 2017, 00:01
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...and when a thread runs to 5 pages, you just get the feeling something ain't right!
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Old 13th Oct 2017, 02:23
  #87 (permalink)  
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kungfu panda - as well as passing Perf 'A' I also operated heavy aircraft under hot and high conditions. Of all posters here you are the biggest worry, making absolute declarations, e.g. "I think that it is disappointing that so many professionals fail to recognise that this was not a normal take off."
Based on nothing more than an amateur filming a take off from a passenger seat through a passenger window with a smart phone! Think about it man, it is so ridiculous to not even bear thinking about, you have no supporting technical evidence for your wild claims, for that is all they are. As I said in my first post on this thread, we are largely spoilt by having much more runway than we need, it is only when we get into the heavy aircraft/shorter runway/high temp/humidity/altitude that we start to realise that some runways are just, and only just, long enough. Try Johannesburg, (14000'), on a summers afternoon heading off on a ten hour sector, or Singapore, (13150'), any evening, heading to Europe only a few kilos below the limit for the conditions, both in a B747-400, believe me, runway ahead never disappeared so fast.
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Old 13th Oct 2017, 06:05
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And in any of those places, a takeoff like this with all engines running would be a concern. As I'm sure you know. It's quite basic, if an engine had failed at V1 would they have made it? Nom

One thing I know, if this video had been taken on a plane in Indonesia no-one would be saying nothing to see here.
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Old 13th Oct 2017, 06:28
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It's quite basic, if an engine had failed at V1 would they have made it?
There's no guarantee!

You do the performance calc's, cross check them with your offsider and away you go.
If you both make the same error in the calc's and then have an engine fail right at V1, you've having a crap day indeed!

You can't second guess everything. You'll never get airborne.
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Old 13th Oct 2017, 06:48
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Based on nothing more than an amateur filming a take off from a passenger seat through a passenger window with a smart phone!

That would include the smart phone video taken out of the window of the B737 going off the end of Thessaloniki on landing, then.

You can market it any way you want however from start of rotation to end of runway is 5 seconds. Three seconds rotating till airborne (10 degrees pitch ish) then airborne for the 2 seconds before end runway. Whichever way you look at it that’s not cool!

I'll reserve judgment due to lack of facts about the takeoff performance calculation, but the above is true. The photo is referenced ground markings and they do not lie. The numbers might well have been correct, but the rotation technique not. If PF was fixated on the runway, and also PM, who then forgot to call "V1" or "Rotate" it could be that no-one was looking the ASI. PF saw the runway end closer than ideal, glanced inside, said WTF and rotated. It was not a 'haul off' the runway, but still a normal rotation suggesting no panic. But the CVR would have been interesting in those few seconds, and perhaps during a discussion once in crz.
Reference my earlier point about monitoring; I watched nearly every F/O, when PF, on CAVOK calm days, just fixated on the runway with blinkers and never once glancing around. It was if they had no idea what else was going on, anywhere, other than the tarmac rushing by. I expect there will be divergent opinions about that so let's not start a topic drift; I just throw it out there as to why there might have been a late rotation, because that seems to be the case.
There was one poster who was concerned about derate, assumed temp, and improved climb all together. Is that possible? I thought improved climb required full umph, or did I misunderstood the comments? I doubt improved climb was in play here, as excess runway is required, and I doubt 2011m gives any excess.
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Old 13th Oct 2017, 07:04
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Parabellum

Try Johannesburg, (14000'), on a summers afternoon heading off on a ten hour sector, or Singapore, (13150'), any evening, heading to Europe only a few kilos below the limit for the conditions, both in a B747-400, believe me, runway ahead never disappeared so fast.
Agreed, and before anyone goes "ah yes but that is a four holer" I'll add NBO at RTOW on a heavy twin using improved climb to that list....the runway end looks to be getting darned close after V1 but before rotate...I have no idea what that looks like down the back because I am generally looking forward.

As for the video that started all this..As for the long take off claim..... Looking at the RHS window frame and the horizon I still think rotation started at or before 1500 feet to go...as for the rate, pitch attitude, and height over the end of the clearway I'd suggest the only objective arbiter is the FDR.

As for the general issue of videos such as this.., OK, the "producer" may have feel he or she has made an interesting observation,..OK, "air" it, for comment such as we have had, but absolutely no attempt has been made to redact the flight number/destination, the date is probably genuine, and if you look at his narrative he/she also grumbles about the flight ending in a hard landing....frankly some of these videos are starting to look less like an attempt to highlight something of interest and more like the work of somebody who gets satisfaction out of shouting "sir, sir" and who also twitches the curtains in their spare time.

Last edited by wiggy; 13th Oct 2017 at 07:22.
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Old 13th Oct 2017, 07:32
  #92 (permalink)  
 
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Modern times

Quote (RAT5)
There was one poster who was concerned about derate, assumed temp, and improved climb all together. Is that possible? I thought improved climb required full umph, or did I misunderstood the comments? I doubt improved climb was in play here, as excess runway is required, and I doubt 2011m gives any excess.[/UNQUOTE]

Yeah Rat, in days of old, improved climb was only used with full thrust, to improve one engine out climb performance by using excess available runway length to accelerate to a higher Vr, and thus to a higher V2.

Today, the bean counters have invented the method to use excess runway length for a greater reduction of thrust, so that takeoff performance only JUST satisfies regulations.

As far as derate plus assumed temperature is concerned, that sounds more frightening than it is: if the situation calls for e.g. 85 percent N1, that could be achieved with e.g. Derate 2 at 35 degrees assumed, or Derate 1 at 48 degrees assumed, but e.g. Full rated at maximum assumed might for instance not be below 87 percent N1. So, in all cases, used thrust would be at least the same.
Biggest consequence of a derate would be subsequent automatic use of derated Climb thrust after thrust reduction point.
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Old 13th Oct 2017, 08:07
  #93 (permalink)  
 
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+1 to the above

Within the last year or two to improve payload we have started routinely using reduced thrust ( if circumstances allow) and improved climb and if that wasn't enough also aft C of G performance if possible. That really does remove most of the fat and hidden margins people were used to in the "olden days". As EMIT says the figures are designed to just satisfy regulations...and guess what, whilst legit it can certainly look "close".....
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Old 13th Oct 2017, 08:09
  #94 (permalink)  

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No doubt the jungle drums have by now reached the AAIB.

If they are in anyway concerned, an investigation will begin. Should this launch be classified as "abnormal", a published report will appear in the fullest of time.
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Old 13th Oct 2017, 08:19
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No doubt the jungle drums have by now reached the AAIB.

Some of the similar scenarios mentioned, including the Canadian airbus in BFS, was it, caused ATC to notify the powers that be, as they were mighty concerned. What did ATC see on this occasion? Did they also think it was 'normal procedure and non-event'.?
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Old 13th Oct 2017, 08:25
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Originally Posted by wiggy
+1 to the above

Within the last year or two to improve payload we have started routinely using reduced thrust ( if circumstances allow) and improved climb and if that wasn't enough also aft C of G performance if possible. That really does remove most of the fat and hidden margins people were used to in the "olden days". As EMIT says the figures are designed to just satisfy regulations...and guess what, whilst legit it can certainly look "close".....
Excuse me if i seem a bit slow, as i am a simple person.

How are you able to improve payload and performance using reduced power? This is the way I have read the beginning of your post.

I am aware things have moved on somewhat since I was involved. But that advanced?
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Old 13th Oct 2017, 08:41
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Originally Posted by Musician
If my physics is correct, the formula for constant acceleration from zero is v=3/2*d/t, plug in d=2000m runway and t=38 seconds and we get a threshold speed of 153.5kt, plus/minus measuring error.
Your physics is fine, but it doesn't apply here - acceleration isn't a constant, for a start.
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Old 13th Oct 2017, 09:10
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How are you able to improve payload and performance using reduced power?
Very very badly worded to the point of being wrong on my part and since you rightly picked me up on I'll offer the following but you probably know this already.

Say I need to lift XXX tones..If I use some reduced thrust and normal climb I'll lift off Y metres down the runway...if I plan to lift off at Y plus a bit down the runway and use improved climb to meet the performance criteria I can perhaps carry the same payload and use a larger reduction in power ( power by the hour costs, etc now coming into play) ...or carry a bigger payload with the same power reduction.., or something between the two, or really haul the post with full power and improved climb ...etc etc...... (and if you'll excuse me I'll stop digging now).

Whatever the physics as a result you very much do end up further down the runway at rotate (and a bigger V1/Vr split) than in days of yore. On our Triple Operation we didn't used to see a V1/Vr split very often.....nowadays, except, at very light weights, it quite common to see a 10 knot or more split due to the higher Vr..

I've probably fouled up the above explanation but I certainly second the comment made previously that the bean counters love improved climb and other gems such as aft C of G for payload/engine cost reasons..but it can remove some of the "fat" we were used to seeing out of the window..

Last edited by wiggy; 13th Oct 2017 at 09:54.
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Old 13th Oct 2017, 09:36
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Originally Posted by DaveReidUK
Your physics is fine, but it doesn't apply here - acceleration isn't a constant, for a start.
Yes, I'm aware of that: engines need to spin up, drag increases with velocity and when the aircraft rotates. The nice thing is that any nonlinearities in acceleration make the final velocity (ground speed!) be higher than 153.5 kt -- constant acceleration is the "most efficient" way to cover the distance and ends up with the lowest final speed of all possibilities (unless deceleration is involved). Edit: this paragraph is nonsense.

So it's very much a back-of-the-envelope kind of thing (I doubt the take-off roll started an exact 2000m from the threshold, either); I don't claim to know what the actual speed was (hence my comment, "in theory").

Last edited by Musician; 13th Oct 2017 at 14:20. Reason: correction by SStreeter below, thank you, SStreeter and DaveReid!
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Old 13th Oct 2017, 10:06
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Originally Posted by parabellum
kungfu panda - as well as passing Perf 'A' I also operated heavy aircraft under hot and high conditions. Of all posters here you are the biggest worry, making absolute declarations, e.g. "I think that it is disappointing that so many professionals fail to recognise that this was not a normal take off."
Based on nothing more than an amateur filming a take off from a passenger seat through a passenger window with a smart phone! Think about it man, it is so ridiculous to not even bear thinking about, you have no supporting technical evidence for your wild claims, for that is all they are. As I said in my first post on this thread, we are largely spoilt by having much more runway than we need, it is only when we get into the heavy aircraft/shorter runway/high temp/humidity/altitude that we start to realise that some runways are just, and only just, long enough. Try Johannesburg, (14000'), on a summers afternoon heading off on a ten hour sector, or Singapore, (13150'), any evening, heading to Europe only a few kilos below the limit for the conditions, both in a B747-400, believe me, runway ahead never disappeared so fast.
Mate- You are clearly the biggest worry on this thread. You appear to have similar experience to me. Both 747 classic, 747-400, DC-10, 777. At hot high airports throughout the world, south America, Africa, Asia, China, Europe.

I have scared the heck out of myself with an overloaded aircraft. As I said in my first post. I was overloaded by 15 tonnes (as it turned out after a re-weigh in Istanbul) out of Dhaka (747-200). We got to 2000' from the end of the runway, still below V1 and Vr. It was clear that at that point, the only option was rotation. At an estimate we crossed the threshold of the opposite runway at 50' and then cleared the roof tops of the city by a little more than that. To me that was very, very close. It is indelible in my memory.

It's just very obvious that the video certainly appears to be much closer than the situation which I had. If company policy is causing these situations to occur it must be looked at.

As described earlier, Boeing suggest crossing the opposing threshold at 150'. It's in the Boeing training manual.
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