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Air X 340 at Brasil...

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Air X 340 at Brasil...

Old 15th Sep 2018, 08:09
  #21 (permalink)  
 
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Lead sled, something Id expect to see OEI on a balanced field length. Not AEO.

Im trying to rack my brain as to how this would happen AEO allowing for a V2 over speed for the second segment.i cant get past the fact there is clearway, and only a small amount of stopway so TORA vs TODA variance wouldnt be that much.

I feel something is amiss. There is no chance of accelerating to Vr from V1 following a engine failure and getting airborne if this video is AEO.

However, looking at it again, a >10 second rotate will do that. She didnt want to fly intitually by the looks of it. An underpowered pig it would seem.
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Old 15th Sep 2018, 14:48
  #22 (permalink)  
 
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Originally Posted by LeadSled View Post
Folks,
All I can say is most of you are obviously talking about matters of which you have no relevant knowledge. That is, takeoff performance calculations and accountability, and the used of reduced thrust takeoffs.
That the aircraft becomes airborne close to the end of the pavement signified nothing.
The Antonov at Canberra is nothing exceptional
Whenever you about to accuse others for lack of knowlegde, you better be sure to have your facts right. So let me tell you the facts: 1) it is not Antonov, it is Ilyushin Il-76; 2) there is no flex/reduced thrust take off procedure (or equivalent) on Il-76.
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Old 16th Sep 2018, 09:03
  #23 (permalink)  
 
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Originally Posted by ACMS View Post
Yep looks like a 340 takeoff...........Ive heard many stories about EGT redline exceedences out of JNB and a terrible climb performance.

Horrible Aeroplane
ACMS ... a wonderful display of total ignorance. Ive seen takeoff like that in 777 in high temps.
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Old 20th Sep 2018, 03:24
  #24 (permalink)  
fdr
 
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Originally Posted by LeadSled View Post
Folks,
All I can say is most of you are obviously talking about matters of which you have no relevant knowledge. That is, takeoff performance calculations and accountability, and the used of reduced thrust takeoffs.
That the aircraft becomes airborne close to the end of the pavement signified nothing.
The Antonov at Canberra is nothing exceptional.
The video that is your "primary evidence" shows nothing exceptional, and it looks like a very well controlled rotation and initial climb, to me. The initial rotate attitude may have been a little low, based on the slight increase toward the end of what appears to be clearway. Without a runway survey, I cannot assess the runway plus stopway plus clearway, so I have no way of judging where the screen height should have been achieved in the video.
Tootle pip!!

LEAD, Absolute rubbish, and dangerously so.

Aircraft performance for takeoff is part of the PSCP certification process for the approval of the TC. The aircraft must (not maybe, MUST) comply with it's Type Certificate, and also be in a safe condition on order to be deemed AIRWORTHY.

When you derate a takeoff, you are effectively making a performance case for a higher temperature environment than you actually have. That permits a reduction in thrust setting and saves on engine wear from high rotor speeds and EGT's. Turbine wear is highly non linear as it approaches higher temperatures.

At ALL not just when you think it might be nice to, you are required to meet the requirements laid out in the certification 14CFR PART25/CS25 which are repeated in the local regulations under appropriate sections such as CAO 20.7.1.B.

FYI, and note the reality check on this:

YOU must comply with the most limiting case of either the all engines case, which is factored, or the engine out case. Both have screen heights that must be attained. We usually (and very luckily so) get to see the all engine cases. That is great. For the all engines, there is a 115% margin applied to the outcome, so pretty much the aircraft is required to achieve the screen height of 35' at 100/115 or 87% of the TODA. (OK, 86.96%). So on a 11500' long runway, any aircraft is absolutely required to achieve the 35' screen height without a failure at 10,000' down the runway. If it doesn't, and there is no specific cause of the perofrmance failure, e.g., crew setting wrong power, wrong data/temp, wind change etc, then it is NOT AIRWORTHY. An aircraft that is at 35' and operating at V2+10 or thereabouts, in the second segment has a minimum gradient that it must achieve dependent on the number of noise makers, but it is also in a steady state condition more or less, so it is relatively easy to ascertain what the additional height should be when the aircraft passes the fence (TODA). A heavy jet on all engines will achieve a couple of thousand FPM on all engines at V2+xx, or about 10m/sec, or 33', whatever... it will also be doing some where between 140-180KIAS which is more or less also TAS. In still air, that is ground speed more or less, and yes you can work it out from the info that is historically recorded for the airports. 1 Knot = 1.68781 Feet per second. 140Kts is 236FPS, 180 is 303... At the higher speed, it takes 5 seconds to pass 1500', after the screen height. in that time the plane will climb 5x33 =165 feet higher than the screen height, which is now a height of 200', at the end of TODA. That is without an engine failure.

If you are at 35' at the end of the TODA on all engines, you would be DEAD if you have an engine failure anytime around V1 through to liftoff, and possibly later as well, dependent on the causal factor.

That holds true for DERATED or FULL THRUST cases, the only difference is a trade off towards the limit case as indicated above every time you derate.

Take the same runway, and look at the speeds for rotate, and consider when Vr MUST occur in order to be legal. This is simple DF maths, nothing special.. The aircraft achieves a Vr of say 170 for the V2 case of 180, some distance before the screen position. The plane has to alter its attitude, generate lift and continues to accelerate until achieving a stable target speed. For simplicity, take the average speed (plane is required to achieve V2 by 35' as well in the OEI case). So the mean speed is 175KIAS, 295FPS. How long does it take to rotate, achieve the attitude and get to 35'. Good question. The FCTM or FCOM will provide that guidance, as does the data of all the takeoffs that get done. And it happens to be about 5 to 6 seconds for the wheels to be off the ground, and about another 2-2.5 seconds to achieve 35', being generous. So using the shortest possible figures, you have 5+2= 7 seconds at 295FPS=2065' from "ROTATE!" to getting to 35'. It could also be as much as 2500'. What is ain't is instantaneous, we don't levitate, we rotate. So now on the 11,500' runway we get to be at rotate at 10,000-2,000 to 10,000-2,500 = 8,000' to 7,500' down the runway.

On an instrument runway, assuming there is no clearway of interest, then there are touchdown zone markings in the last 3,000' of each end of the runway, so you get to see the departure end stuff under your nose (vertically below, not visual cutoff) at 8.500' down the runway.

IF YOUR RUNWAY DOESN'T INCLUDE STOPWAY, on a limit takeoff on the assumed 11,500' runway, you get to rotate well before approaching the 3000' markers. By well before, enough that if you have already lost sight of the first marking, you have a compromised takeoff performance case.

For any one interested, go and stand across from that exact point, (use Google Earth... check where it is, use the Jepp or declared distances to ascertain the applicability of CWY etc to the TODA... but you can go and look at that point and see if the nose of the aircraft commences to rise anywhere near that.

Alternatively, you can just watch the aircraft pass the TODA distance, and look at the relative height above ground reference using the wingspan, tail height, wheel diameter, door heights etc as gnomons. Sometimes you don't need to do that, as there is no vertical distance to be discussed. I did this once for an A340-300 taking off on 07R at VHHH, and the measuring yard stick was the Toyota taxi that it was no higher than the roof height above the Toyota as it passed overhead. The main wheels came off the ground within 500' of the end of the runway. The windsock showed a headwind throughout, and it agreed with the ATIS at that time. (Nothing against the A340, but it does love runway, but it is not even close to being alone in that regard).

We have engine failures at the worst position very rarely, as in almost never. The legal case remains the legal case, and if your plane is not making the numbers, then that is a mandatory reportable event. Read your airlaw.

Do/Don't as you see fit. But as an operator, normalisation of deviation doesn't make the world safer, and certainly doesn't make the problem go away.

The causes of failure are various, and sometimes they are not within the purview of the crew, they may be much deeper than that. As a pilot, don't believe that you have lots of additional padding to waste on runway line up and similar, or that there is additional reserves for messing about, there is not. I have been in seat 1A of a B744 that perfectly aligned with the centerline and I had the 1500' markers outside of my window, then we took off. That was a limit case takeoff, and we didn't get close to remaining legal on it. Does the FOQA system pick up such items? NO.

Summary:
  • DERATED operations should never result in a lower screen height, the aircraft is still required to have met the performance of the assumed higher temperature. Don't confuse that with a wet V1 accepted reduction in screen height (reducing the wet V1 not below VMCG by a specified value improves the reliability of the rejected takeoff case, but results in the lower screen height being accepted. The lower screen height is not an acceptable height to achieve without a damn good reason, like having a wet runway, applying a reduced V1 and having a failure at Vef.).
  • Getting to 35' on all engines at the end of the TODA and no more, proves conclusively that you did not have the ability on that takeoff to accept an engine failure, deal with that knowledge as you see fit.
  • The only people identifying performance failures are the flight crew, and as a group we grossly fail to meet our moral obligations, but then, that makes us no worse than the rest of the system that doesn't give a damn either.
  • It's your life, and those of your passengers, family and friends.
  • A failure doesn't occur in the critical condition often, but they do on occasions (stuff happens to marines... ) but that doesn't make it right.
  • Do not waste runway, the margins may be less than you think for reasons outside of your direct control, and some due to your own actions.
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Old 20th Sep 2018, 03:42
  #25 (permalink)  
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Originally Posted by JayMatlock View Post
Rotation is a bit slow.. It took about 6s from what I see, whereas it should be done at around 3s per second, which would give about 3s between nlg and mlg takeoff
Jay, you can't get 3 degrees a second instantaneously, it takes a time to establish the rate, and then the rate has to be reduced to avoid over-pitching, and that means that the rate of 2.5-3 degrees a second only occurs for a part of the rotate, The actual pitch obtained vs time is an S curve, so the underlying rate is more or less a Poisson/normal curve, or in other words, an upside down U. Each part of the pitch.dot change takes time, and that adds to the overall time to achieve the required attitude which will also occur (AOTBE) at a target IAS.

Additionally, once you rotate and lift off, you then have to get to 35'. That takes around another 1.5 seconds to 2.0 seconds to occur.

You are going from 0 to 3 degrees a second rate, and to get that in one second would take a 6 degree a second rate to have been achieved at the end of the second, which will get your eyes watering. the pitch.dot.dot is closer to 3 degrees a second max, and that means it takes a couple of seconds to achieve 3deg sec. If there was a square wave input, (which we don't do) then that would add 2 seconds to achieve 3 sec, and at the end of 3 seconds you would have 6 degrees attitude. At that rate, you are now starting to wash out the input so the rate reduces, and so the next 6 degrees takes about the same time to achieve. Liftoff will occur passing through between 9-11 degrees depending on what brand of plane you are flying, if you are on speed. If you are fast, rougly each 5 KIAS fast will result in liftoff pitch being about 1 degree lower than on speed. Same for low speed.

As a note, be aware that while ground effect increases lift, it also reduces stall AOA... excessively fast rotates can spoil your day. Not a major problem if you have leading edge devices, more interesting if you don't, or if your wing LE is contaminated. Slow rotation adds take off distance. Under-rotation adds lots of distance.

In the video, the A340 commences rotate at 18 seconds into the video, and is over the end of runway at 27 seconds, and the cliff at 28 seconds. That is 10 seconds maximum to the TODA, and that is beyond the DER which is 10.600'. The plane should have been at 35' 1,382' before the end of the runway, 92,17' from the start of the runway on all engines. From achieving 35' there should have been another 4 seconds of climbing at V2+xx, for additional height above 35', so that is around... another 100-120' (its a Babe...). At is got to the end of the runway (not the cliff) it should have been at around 135-155'.

taking the latest time that the aircraft could be at 35' from the end of the TODA (cliff) then the aircraft should be at 35' at 24 seconds. At that point, its main wheels are still WOG.

Last edited by fdr; 20th Sep 2018 at 03:59.
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Old 20th Sep 2018, 11:02
  #26 (permalink)  

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fdr thank for the time and effort put into providing us with the two above posts. Most helpful and refreshing to see such qualified piece of work.
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Old 20th Sep 2018, 13:58
  #27 (permalink)  
 
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I wonder if TOGA was considered when they realised the main gear was rather keen on remaining earth bound?
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Old 20th Sep 2018, 21:12
  #28 (permalink)  
 
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Looks like a much slower than normal rotation to less than the target 12.5 degrees pitch

A340 lifts off at around 10 degrees and that appears to be what happens here.

My guess would be the pitch stays around 10 degrees instead of 12.5 degrees which is why the aircraft barely climbs.

Difficult to tell from a video but it looks like a Config 1+F take-off instead of Config 2 which is standard at my Airline.
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Old 21st Sep 2018, 06:23
  #29 (permalink)  
fdr
 
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Originally Posted by Eric Janson View Post
Looks like a much slower than normal rotation to less than the target 12.5 degrees pitch

A340 lifts off at around 10 degrees and that appears to be what happens here.

My guess would be the pitch stays around 10 degrees instead of 12.5 degrees which is why the aircraft barely climbs.

Difficult to tell from a video but it looks like a Config 1+F take-off instead of Config 2 which is standard at my Airline.
And an under-rotate. Notwithstanding either of those factors, the runway length was tight, as in just as well they didnt lose a donk at V1-1sec (Vef). Had they, they would have benefitted from the carrier bow shot out into space.

In rough terms, each degree of error in attitude (AOTBE) is worth the mach number x1000FPM, i.e., 180KIAS @ 2000' PA, ~ 0.28M, 1 degree is 280PM. Under rotating messes up the ROC, and the excess speed (if no shear) makes the gradient worse as well.
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Old 21st Sep 2018, 14:12
  #30 (permalink)  
 
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After having read most posts, I recall a similar incident I experienced in an A340 ca. 20 years ago in ... GRU... right next door to VCP.

Our problem then, was that the aircraft was - in hindsight - obviously overweight and a varying light wind was not helping either.
OAT was reported as being 36C - which resulted in a TOGA take-off.
Initial acceleration was normal (i.e. the aircraft started moving), but just after(!!) V1 the IAS acceleration arrow went from 5 knots up, to 3 knots down, 5 knots up etc. and a veeeeerrrry slow further increase in speed.
Thrust levers were at their physical forward detent, A/C on APU and WTF-grunts where heard as we lumbered down the runway and tried to figure what to do.
And then, as the centerline lights turned from white to read-white the "old man" flying ever so gently pulled on the stick, got it flying in ground effect, but kept the very gentle rotation going as the speed increased, and when we were sure it was actually flying, we raised the gear lever.
Behind RWY 07 (?) there was a large white warehouse that produced an updraft that helped us over the hills to the East.

Next time around I told the local mech about our experience and he said. "Everybody knows, you have to had 3-4 degrees to the reported OAT when calculating the T/O performance in this heat."
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Old 5th May 2019, 15:33
  #31 (permalink)  
 
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Armchair analysis of the take off

Over here: https://github.com/paulross/pprune-c...ster/A340-SBKP It concludes that the aircraft became airborne with 198 25m of runway left.

Specifically:
  • The takeoff started 34.2 1.4 seconds before the beginning of the video with the aircraft 75 159m from the start of the runway.
  • At the start of the video the ground speed is 113 5 knots. The aircraft is 1110 25m from the start of the runway with 2130 25m of runway remaining.
  • When the nose wheel comes off the ground speed is 159 5 knots with 865 25m of runway remaining.
  • The rotation rate at this point is +1.4 degrees/second for the next 5 seconds to +7 degrees.
  • When the main wheels come off the ground speed is 176 5 knots with 198 25m of runway remaining.
  • The takeoff roll took 59.8 1.4 seconds.
  • The aircraft crosses the end of the runway 2.2 seconds later at a ground speed of 180 5 knots.
  • At 29 seconds there is a further pitch increase of +1.4 degrees/second from +7 to +12 degrees.
  • The useful part of the video ends at t=35.7 seconds, the ground speed is 193 5 knots and the aircraft is 755 25m beyond the end of the runway 15.
  • The observer is within 25 metres of Latitude -23.011945, Longitude -47.115872

Here is the data plotted on an image of Viracopos International Airport from Open Street Map. The red boxes illustrate the accuracy of the position estimate. The probable location of the observer is also shown, the black lines are transits that establish that position.

The annotations in blue contain:
  • v= The ground speed in knots.
  • t= The time as video time, followed by [...], the estimated time from start of takeoff.
  • d= The distance from the start of the runway, followed by [... to go], the distance to the end of the runway.

Annotated OpeStreetMap image of Viracopos International Airport
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Old 5th May 2019, 16:00
  #32 (permalink)  
 
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Seen this jet do the same on departure from EGSS. All the way by road. Climb looked so poor it could have probably suffered a birdstrike from behind!
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Old 5th May 2019, 18:12
  #33 (permalink)  
 
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Airbus use a “potato” type of graph to calculate take off performance, this uses the full Rwy length at heavier weights. On a FOUR engine aircraft this will always look odd compared to a 2 engine aircraft. Performance A refers.( note screen heights of 35 feet dry (15wet?) should still be met.

Last edited by IcePack; 5th May 2019 at 22:50.
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Old 5th May 2019, 20:11
  #34 (permalink)  
 
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Ah, I see. I guess four engined aircraft can have tighter limits as loosing one out of four is less worse than one out of two.
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Old 6th May 2019, 07:36
  #35 (permalink)  
fdr
 
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Originally Posted by IcePack View Post
Airbus use a “potato” type of graph to calculate take off performance, this uses the full Rwy length at heavier weights. On a FOUR engine aircraft this will always look odd compared to a 2 engine aircraft. Performance A refers.( note screen heights of 35 feet dry (15wet?) should still be met.

Yes, 35' (15' wet) apply but are to be met with an engine failure from V1- 1 second... Assuming that the A340 in question was still running on all 4 blenders, then they should be nowhere near 35' (it wasn't raining...). They should be well above that height, in fact, about 150-180' AGL passing the end of the runway. Now for anyone who has watched a 340 doing a heavy weight TO, you will be ROFL. Same applies to B747's, etc. The plane is required to meet 35' at 87% of the TODA... not a couple of feet over the grass without an engine failure. If you are below 35' without having had a reduced V1 for wet conditions and suffering a failure at V1- 1 second, then you didn't perform IAW the TC. If you are on all donks, then you are expected to be at 35' at 87% of the TODA, and so will be higher than 35' by the time to traverse the remaining 13% at your all engine initial ROC. That gives a large addition for the 4 engine case. The 4 burners look odd only compared to 2 burners, where on a normal TO without failure there will be considerably more margin remaining. Both cases have the all engine and the engine out cases to be met. Achieving an OEI outcome particularly a wet OEI (only pertinent for the reduced V1 case which will lead to a reduction in screen height crossing), when you don't have a problem IS a BIG A$$ problem. Logically, if you scrape off the ground on all bunsens, barely making the engine out case, then on what planet are you going to suddenly do better when you have an engine failure? You may be lucky and never lose a noise maker on a TO roll, it is not a common event but it does happen, and some poor schmuck is going to be in an invidious position. Recall a certain B747 at BRU, it did have a donk call it time out on a takeoff and the plane blocked the railway for a few days, and was in about 3 main pieces. That data shows the plane was already compromised before the failure, there was no way it was going to have a happy ending without a visit to BKK.

Using a derated TO or similar reduced thrust does not reduce the requirement to meet the regulatory requirements. The aircraft is merely approximating a heavier aircraft/warmer conditions, and so should not compromise the minimum altitudes without an external reason.

If you don't perform correctly, the plane is not compliant with the TC, unless the cause is external to the plane, e.g., the temp is hotter, the wind was worse, the plane was heavier, the runway was shorter, the thrust target was incorrect, the flaps were wronger... etc.... all of the usual suspects. Sometimes, there are no obvious excuses, and the plane doesn't do it's thing very well. Occasionally that has a bit of a history.
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Old 6th May 2019, 15:41
  #36 (permalink)  
 
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FDR lots of numbers and "facts" but DERATE and FLEX are TOTALLY different in the Airbus. Where on earth do you get this
If you are on all donks, then you are expected to be at 35' at 87% of the TODA
. Having flown various versions of the A340, hot heavy etc the end of the runway can be very close. V1 decision allows for 2 seconds not 1, and V1 is a long way behind the aircraft.
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Old 7th May 2019, 00:34
  #37 (permalink)  
 
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I was trying to see whether the flaps were at the correct setting.
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Old 7th May 2019, 07:21
  #38 (permalink)  
 
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Never flown 4 engine aircraft, but isnt the limiting factor for take off on these aircraft the all engine scenario?
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Old 7th May 2019, 07:46
  #39 (permalink)  
 
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Reminds me of flying the SQ Singapore - Newark route when it was the longest commercial flight in the world (circa 18.5 hours). There was zero 'push in the back' on take off and it felt like we were going to drive there!
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Old 8th May 2019, 02:25
  #40 (permalink)  
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Originally Posted by ManaAdaSystem View Post
Never flown 4 engine aircraft, but isnt the limiting factor for take off on these aircraft the all engine scenario?
Sorry, but how could that be?
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