Ryanair uses all the runway.
Wiggy ; I never got it, still don't. If you are going to reduce your power (we used to call it EPR) in order to increase payload (still don't get it), how much do you reduce ? Got any charts, figures etc ? And, you then want to "take off at Y plus a bit" . How much is a bit ? By getting a reduced V1, I am just beginning to acknowledge a increased VMCG but the rest of the argument has always left me very cold without specific charted info. Digging backwards through charts that give you an increased payload with reduced thrust is for the very brave. As you wipe out the ILS aerials, treetops and blow off a couple roof tops, have more evidence than "reduce" and "a bit", ready for the tea & biscuits.
As described earlier, Boeing suggest crossing the opposing threshold at 150'. It's in the Boeing training manual
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In line with the last few posts, yes the latest Boeing performance thinking does allow optimisation of assumed temp/de-rate/improved climb all at the same time.
It's unlikely you'd get improved climb on a short runway, though unless there's a howling headwind.
Rummaging through the book, I doubt you'd get de-rate or assumed temp reduction at BRS. *
V1 split would be less than 5kt so the answer to the "would it have flown with a V1 cut?".
Probably.
At our place we have expressed surprise at the amount of runway we seem to be using these days, but if the book says it's fine, eh...?
(Not getting drawn in to the rotation technique in this case).
* That's assuming we are close to perf limiting mass.
It's unlikely you'd get improved climb on a short runway, though unless there's a howling headwind.
Rummaging through the book, I doubt you'd get de-rate or assumed temp reduction at BRS. *
V1 split would be less than 5kt so the answer to the "would it have flown with a V1 cut?".
Probably.
At our place we have expressed surprise at the amount of runway we seem to be using these days, but if the book says it's fine, eh...?
(Not getting drawn in to the rotation technique in this case).
* That's assuming we are close to perf limiting mass.
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Quote "With Normal takeoff thrust, the airplane should easily reach a height of 150 feet over the end of the runway,"
This clearly indicates that the takeoff in the video was not normal.
Is your opinion that the video shows a normal takeoff?
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The formula for constant acceleration is v = 2 * d/t - final velocity is twice the average
(Your formula using 3/2 is true for constant power).
The lowest final speed without deceleration is achieved by being catapulted to average velocity at the start of the takeoff run and then maintaining it.
The important point is touched on in posts above. How much money is saved by using all the runway, compared with using all the available power? Would pssengers be happy about this calculation if they know of it?
Gordo
As I mentioned to Dan earlier that statement was my 
, so I'd refer you to my post to him earlier[/quote]
Nope there's an "app " of sort for that, 
, now whether that app is picking figures out of the wind? BEtter ask the performance engineers, but certainly reduced power and improved climb is a combination in use on Boeings in certain circumstance.
SStreeter..
Would they be happy about the fact we rarely fly anywhere with full tanks?
Wiggy ; I never got it, still don't. If you are going to reduce your power (we used to call it EPR) in order to increase payload (still don't get it),
, so I'd refer you to my post to him earlier[/quote]
how much do you reduce ? Got any charts, figures etc ?
, now whether that app is picking figures out of the wind? BEtter ask the performance engineers, but certainly reduced power and improved climb is a combination in use on Boeings in certain circumstance.SStreeter..
Would pssengers be happy about this calculation if they know of it?
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This is usually where a cadet would shine brightly explaining all the ins and outs of the takeoff requirements but i remember many years ago that you need to clear the screen by 35 feet if dry one engine inoperative and that can include a clearway, if there is one. Also assuming the youtube video would have a different name if they were indeed flying single engine, so one issue with what looks like a late two engine takeoff is if they would have the thrust to go single engine from a earlier point than this takeoff and still clear the screen. All in all i wouldnt take poision on either or before knowing more...
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Of course, if they've any sense: it reduces the takeoff roll (or, as LookingForAJob points out below at 14:49, the thrust required for a given amount of runway).
Last edited by SStreeter; 14th Oct 2017 at 14:47. Reason: add bit in brackets
There is a question I am fully qualified to answer ;-)
I am sure that any pax that thinks about it understands the principle of not carting around needless fuel while making appropriate allowance for alternatives. And fans of cabin pressure understand that max landing weight may be less than the actual takeoff weight!
Similarly, I am sure most would be perfectly happy that takeoff runs are based on appropriate calculations and that you guys don't just blast into the air in the shortest possible distance.
On the other hand, we get a little twitchy when the safety margins seem to be pushed to their limits as in that video. Almost as twitchy as when they run out red wine in business class (KQ, that's you)
I am sure that any pax that thinks about it understands the principle of not carting around needless fuel while making appropriate allowance for alternatives. And fans of cabin pressure understand that max landing weight may be less than the actual takeoff weight!
Similarly, I am sure most would be perfectly happy that takeoff runs are based on appropriate calculations and that you guys don't just blast into the air in the shortest possible distance.
On the other hand, we get a little twitchy when the safety margins seem to be pushed to their limits as in that video. Almost as twitchy as when they run out red wine in business class (KQ, that's you)
Sorry but that does seem very tight, I don't see why everyone is bagging the kid.... the video is titled 'Ryanair uses the whole runway' and guess what they sure did.
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I've seen Boeing OPT I-pad and what it can do, but I've never used to operationally. I was the last dinosaur with RTOW tables. I'd looked at what weight we could get off with 29c and then see what ASS Temp was available and note the difference in weights. If the ASS TEMP gave e.g. a 5-6ton decrease then that told me there were plenty of margins and I could choose anywhere between 29c & full reduction. I put my finger in the wind and thought about it. The wind was variable across, perhaps might be a little tail as we reached the hold: it was dampish or worse and there was a lot of rubber - probably- at the other end in the stopping zone; etc. etc. A reasoned judgement was made. The tables allowed you to see the rate at which the weight reduced as temp increased. You had a feel for what was going on.
Then came wiz-bang iPads. Punch in the numbers and with no 'feel' out came the most optimum answer and max reduction and so that's what the guys do, now. No feel, no understanding, no decision. It's max reduction or none, nothing in between. Is that correct?
I was sitting on a 3000m runway, with tables, and the F/O asked if I wanted to use reduced. We looked at the numbers and at max ASS Temp we were still not runway limited. So why not. On our return the runway was shorter, same question. We looked at the table and saw that at 29c we were OBS. This continued until about 38c when it changed to RWY limited. He said we could go to 38c. I said that at 29c we had a LONG runway; at 38c we had converted that into a SHORT runway. Was that wise? OK, we had more thrust at ambient temp than actual assumed, but...To show the company we had thought about it we chose 32c, still OBS. I doubt guys think that way with I-pads. I suspect it is max reduction most of the time with no thought.
Then came wiz-bang iPads. Punch in the numbers and with no 'feel' out came the most optimum answer and max reduction and so that's what the guys do, now. No feel, no understanding, no decision. It's max reduction or none, nothing in between. Is that correct?
I was sitting on a 3000m runway, with tables, and the F/O asked if I wanted to use reduced. We looked at the numbers and at max ASS Temp we were still not runway limited. So why not. On our return the runway was shorter, same question. We looked at the table and saw that at 29c we were OBS. This continued until about 38c when it changed to RWY limited. He said we could go to 38c. I said that at 29c we had a LONG runway; at 38c we had converted that into a SHORT runway. Was that wise? OK, we had more thrust at ambient temp than actual assumed, but...To show the company we had thought about it we chose 32c, still OBS. I doubt guys think that way with I-pads. I suspect it is max reduction most of the time with no thought.
Last edited by RAT 5; 14th Oct 2017 at 08:06.
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I didn't say that the 150' is any part of the performance application. What I wish I could do was copy and paste the Boeing training manual. I can not but the reference is page 3.25 Go/Stop decision near V1.
Quote "With Normal takeoff thrust, the airplane should easily reach a height of 150 feet over the end of the runway,"
This clearly indicates that the takeoff in the video was not normal.
Is your opinion that the video shows a normal takeoff?
Quote "With Normal takeoff thrust, the airplane should easily reach a height of 150 feet over the end of the runway,"
This clearly indicates that the takeoff in the video was not normal.
Is your opinion that the video shows a normal takeoff?
Happy to "help"?
From a B777 FCTM:
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.
Making the Go/Stop decision starts long before V1. Early detection, good crew coordination and quick reaction are the keys to a successful takeoff or stop.
I have been told by finance guys that one of the largest costs involved with the operation of modern airframes is engine maintenance (which can exceed the hull value over its life). The frequency and expense of this correlates very well with thrust/EGT margins on takeoff, so unsurprisingly there is pressure from above to get the job done with the minimum thrust required to meet the regulations.
The performance people have had to get quite creative: we now have AT derates, fixed derates, improved climb, CofG adjustments, packs off, etc. sometimes all used at the same time.
I have noticed over the last few years the end of the runway becoming slightly more prominent on occasions as some of these measures have taken effect but as we are still meeting or exceeding the same requirements as before, it’s more a perception issue than one of safety.
Going back to the video in question, without the FDR and a whole load of other data, I couldn’t definitively say that something was *grossly* wrong with it. A marginally late rotate call followed by a slightly slower rotation rate would produce the effects noticed on the recording, with the correct thrust setting. If they’d carried on at treetop height for the next couple of miles, then yes but that didn’t happen.
The performance people have had to get quite creative: we now have AT derates, fixed derates, improved climb, CofG adjustments, packs off, etc. sometimes all used at the same time.
I have noticed over the last few years the end of the runway becoming slightly more prominent on occasions as some of these measures have taken effect but as we are still meeting or exceeding the same requirements as before, it’s more a perception issue than one of safety.
Going back to the video in question, without the FDR and a whole load of other data, I couldn’t definitively say that something was *grossly* wrong with it. A marginally late rotate call followed by a slightly slower rotation rate would produce the effects noticed on the recording, with the correct thrust setting. If they’d carried on at treetop height for the next couple of miles, then yes but that didn’t happen.
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Ahhhh! It is refreshing to wake up with fresh coffee, a good zigar and the sun out for a change up here at 60 north.
And some common sense on Pprune. Thanks RAT.
I do not want to speculate on this particular video.
But here is a few observations about the 738-800 with 26 000lbs engine in general and short runways.
Assume runway limited no obstacles: 2011 meter.
Try flap 5 standard: no go
Try flap 15 : just possible if wind is the same in 15 min when rotating.
Try flap 25: Margin for a say 5 kt wind change.
If 25 is tight. do a bleeds off that gives you some 1200kg more to play with.
Now as we all know since we have done so many F15 and F 25 takeoffs, the correct V1 and Vr callouts are critical.
And the proper rotation rate even more, as tailstrike is not an issue : get the 3 degrees going . Mind you to a lover initial pitch.
I have to say we are generally spoiled with plenty of runway and or performance. I see slow rotation quite often on long runways and do not mind.
Doing my initial years on a 1070 meters runway with a close in obstacle at one end and a cliff at the other end I appreciate the need for proper performance.
The I-pad generation , I am not so sure.
" Cpt, Ipad says NO"
" Take away 100kg for taxi!"
" Splendid, now it says GO"
I was on the jumpseat with NOR the other day.One of the options I like is the automated V1 call.
I did get a tad crossed the other day when my FO forgot to call V1- Rotate on a short runway.
No drama , and he is not going to do that again.
And some common sense on Pprune. Thanks RAT.
I do not want to speculate on this particular video.
But here is a few observations about the 738-800 with 26 000lbs engine in general and short runways.
Assume runway limited no obstacles: 2011 meter.
Try flap 5 standard: no go
Try flap 15 : just possible if wind is the same in 15 min when rotating.
Try flap 25: Margin for a say 5 kt wind change.
If 25 is tight. do a bleeds off that gives you some 1200kg more to play with.
Now as we all know since we have done so many F15 and F 25 takeoffs, the correct V1 and Vr callouts are critical.
And the proper rotation rate even more, as tailstrike is not an issue : get the 3 degrees going . Mind you to a lover initial pitch.
I have to say we are generally spoiled with plenty of runway and or performance. I see slow rotation quite often on long runways and do not mind.
Doing my initial years on a 1070 meters runway with a close in obstacle at one end and a cliff at the other end I appreciate the need for proper performance.
The I-pad generation , I am not so sure.
" Cpt, Ipad says NO"
" Take away 100kg for taxi!"
" Splendid, now it says GO"
I was on the jumpseat with NOR the other day.One of the options I like is the automated V1 call.
I did get a tad crossed the other day when my FO forgot to call V1- Rotate on a short runway.
No drama , and he is not going to do that again.
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FullWings, now those are interesting thoughts. In the AF66 discussion, msbbarratt was wondering why the engine fell apart in cruise and not on takeoff, the strain being greater there than on a simple flight level change in cruise. If that flight took off at reduced power, that might have prevented the engine from coming apart there and then, turning an engine failure on takeoff (and the fan disk dropping off over London) into an engine failure at altitude over uninhabited terrain. Reduced thrust is not all downsides, safety-wise!
A marginally late rotate call
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As someone mentioned earlier, perhaps O"Leary likes to get his moneys worth.
https://www.youtube.com/watch?v=_JyEG6FrIKo
https://www.youtube.com/watch?v=_JyEG6FrIKo
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Whilst the PM should make the calls at the correct speed, equally the PF should be taking the correct action at the appropriate speed even if the calls are omitted.
Ref a comment in my post about F/O's as PF not observing the instruments during the roll. They are blinkered on the centreline. Fixated. You could ask them a question and they would not hear you. Not good. Takeoff roll should be sharp, alert and relaxed. Tense is not alert; quite the opposite.
In some of my last operators the 'tick in the box' incapacitation scenario is often no PM call at 80kts. PF rejects. Box ticked; let's all reposition to takeoff and leap into the next box ticking exercise. It makes it more entertaining and worth far more if the PF does not respond to 80kts. Even more entertaining is if PM does not call V1 or Rotate; on a runway limited takeoff. That is really an eye-opener and a huge "I won't do that again moment" for PF. The end of the runway, at that speed, approaches faster than an F1 start grid into the first corner. After watching F/O's do blinkered takeoffs it was shocking to see them carry it over into LHS. This 'startle factor' moment served them both well.
ref bean counters. I wait for the day when the statisticians do the maths and decide that the chance of engine failure at V1 is so negligible as to be ignorable. Hey presto; more weight from runway.
Ref a comment in my post about F/O's as PF not observing the instruments during the roll. They are blinkered on the centreline. Fixated. You could ask them a question and they would not hear you. Not good. Takeoff roll should be sharp, alert and relaxed. Tense is not alert; quite the opposite.
In some of my last operators the 'tick in the box' incapacitation scenario is often no PM call at 80kts. PF rejects. Box ticked; let's all reposition to takeoff and leap into the next box ticking exercise. It makes it more entertaining and worth far more if the PF does not respond to 80kts. Even more entertaining is if PM does not call V1 or Rotate; on a runway limited takeoff. That is really an eye-opener and a huge "I won't do that again moment" for PF. The end of the runway, at that speed, approaches faster than an F1 start grid into the first corner. After watching F/O's do blinkered takeoffs it was shocking to see them carry it over into LHS. This 'startle factor' moment served them both well.
ref bean counters. I wait for the day when the statisticians do the maths and decide that the chance of engine failure at V1 is so negligible as to be ignorable. Hey presto; more weight from runway.
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Obviously statisticians might do the maths and figure out some estimate of the chance of engine failure. Obviously a statistician will never be the one to decide whether that is negligible or not. Those calls are made in a higher office.