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EK407 Tailstrike @ ML

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EK407 Tailstrike @ ML

Old 22nd Mar 2009, 23:35
  #181 (permalink)  
 
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That was a huge contact area along the bottom rear of the aircraft.
Does anyone model the braking effect of that sort of drag, if the aircraft is
trying to nose up so actually pressing down on the tarmac at the rear?
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Old 23rd Mar 2009, 00:36
  #182 (permalink)  
 
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How do you judge correct acceleration?

I'm not for a minute pre-judging the cause of this incident, however for a llong time now I've held a view that very few pilots have any way of judging whether acceleration is correct for the runway in use.

In my former life, we used to have a speed we expected to achieve by a point on the runway (it was a fighter jet, and we expected to achieve a minimum speed by 2,000ft down the runway..otherwise you'd abort the take-off).

I've always been surprised there is nothing similar on bigger acft (despite the complexities involved).

I ask many of my FOs (and other Capts) what they use to assess correct acceleration. Most people reply "just a feeling" That doesn't work for me! I've watched the trend vector on the 777 speed tape on just about every takeoff I've done in the last few years. At 100kts or so, it's a minimum of 30kts..sometimes more if you're using higher than normal thrust on a shorter runway.

But given a normal 3500m+ runway, heavy jet, normal derate (or indeed full thrust if needed...it takes about the same acceleration rate to get to rotate speed on the appropriate distance, in particular if you're using balanced field figures). So, if you're taught awareness of what you expect to see on the speed tape for acceleration, you may be better placed to pick up abnormal (reduced) acceleration. To me, its far more likely to pick that up than "sensing" that the aircraft is not accelerating fast enough..especially in the myriad conditions we operate in (the Potomac river incident comes to mind...slow acceleration in low vis ops)

Curious to see what others think of my theory? (again..not saying this is necessarily relevant to this incident, but it brings up the subject I've been passionate about for some time.)
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Old 23rd Mar 2009, 00:45
  #183 (permalink)  
 
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No Speed Checks?

In my former life, we used to have a speed we expected to achieve by a point on the runway (it was a fighter jet, and we expected to achieve a minimum speed by 2,000ft down the runway..otherwise you'd abort the take-off).
I brought this up in another thread and got the same response. I, too, have a military background and don't understand why airlines don't do this. I'd consider it essential to have at least one such check. More when you expect to have a very long roll.
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Old 23rd Mar 2009, 00:56
  #184 (permalink)  
 
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Acceleration Check

I used to fly Falcon 50's and 900's. We had an accelerometer on the PFD that read out in real time, as well as a time to 90 knots that we could figure out. Upon brake release you would look for a certain value. If you did not have at least that number something was wrong.(Not enough thrust, brake dragging, heavier than calculated, not enough tire pressure, etc).

We could literally abort takeoff at 5 knots based on the G number displayed. Or we could wait until we hit 90 knots. If it was at or less than computed time, go. If more, abort. Shouldn't be to hard to calculate and display on these airplanes as well.
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Old 23rd Mar 2009, 01:01
  #185 (permalink)  
 
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flex temp

PJ2 & Wiley
refreshing to see there's a couple of sensible/intelligent contributors to this thread!
Keep up the good effort.
w.r.t. the FCOM, explanation:
whatever flex temp one enters can only be higher than the actual OAT. This is the adjustment/pilot input, to fool the Fadec into thinking it is a much hotter day/conditions than actual, therefore causing it to calculate reduced thrust settings primarily to protect against expected EGT limits or exceedances, & Secondly preserving unneccessary fuelburn & extending the engine life, & noise abatement etc. In short, Big Savings for the company, compared to the 'old days'!
If no flex temp is inserted into the MCDU, then the fadec will by default use the sensed OAT(actual) to determine the T.O. parameters for the given ambient conditions, which will be higher thrust than any Flex take off roll, same as TOGA, if you were to select that detent during the roll for any required reason.
Difference between Flex to Toga, is nowadays ones reserve thrust, available at the push of the thrust lever from one detent to the next, if one gets into trouble & needs it, otherwise the engines on almost all big jets these days very seldom ever use/need use, max take off power that they are capable of delivering, for normal conditions! Wet runways & unusual circumstances excluded, naturally.
I expect you know all this, I am elaborating for the benefit of all.
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Old 23rd Mar 2009, 01:19
  #186 (permalink)  
 
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RE: above

B.T.W my statement there excludes the A340-300, which for any lucrative load in any warm environment only knows TOGA!
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Old 23rd Mar 2009, 01:45
  #187 (permalink)  
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A380-800 driver, easyduzzit;
Your above statement is incorrect. You won't get any warnings if you stuck a higher flex temp in when the actual performance require a lower Flex temp (or none at all).
No, I know you won't get a warning if you stick a higher temperature than the proper flex temp - my comment was in reference to the position of the thrust levers - if they're not in either the TOGA or FLX/MCT detent, the warning I described will sound. Thanks to both of you for sorting out the higher flex temp item; yes, the engines will run "at the flex temp entered".
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Old 23rd Mar 2009, 02:40
  #188 (permalink)  
 
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Having ploughed through the 10 odd pages of this post I'm surprised nobody has mentioned the CX A340 tailstrike at Auckland some time back. After a lot of speculation about the flight crew's ability (or lack of it), incorrect aircraft handling etc it was found the tail strike was due to underinflated main gear struts which had been brought to the attention of the ground engineer, by the crew, who had dismissed it. It was found the flight crew handled the rotation absolutely correctly & the tail strike could not have been avoided given the underinflated main gear struts.
I just mention this for those "armchair" investigators who may be suggesting it's the fault of the crew. It may well be, however I don't know & neither does anyone else so maybe waiting for the investigator's report could minimise "egg on face" & give the crew the benefit of the doubt they deserve.
Just a thought
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Old 23rd Mar 2009, 03:37
  #189 (permalink)  
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As a mere SLF can I ask what may seem a very stupid question? And that is what was so different in this case to the Ryanair tail strike at Dublin last year? I seem to recall the captain of the Ryanair flight declaring a mayday after that and
even discussion about leaking hydraulic fluid,what is so different between the two aircraft types that the amount of damage sustained in this event doesn't seem to have involved that sort of issue and was the Ryanair incident and the reaction of the captain an over reaction?
BTW I'm not saying the Ryanair captain did anything wrong-just asking.
I also seem to recall that in the Ryanair case there was even questions about pressurising the airframe after the event,why was that not an issue here?
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Old 23rd Mar 2009, 03:40
  #190 (permalink)  
 
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Nobody dragged the tail of the plane through some aerials 300 metres off the end of the runway in Auckland or Dublin - I don't think these incidents are comparable......

I feel for these guys and never want to be in this situation - These things are always more complicated than you think - but the only way I can think you don't get off the runway is if you are overloaded / have too little thrust or if you under-rotate initially - time will tell.
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Old 23rd Mar 2009, 03:42
  #191 (permalink)  
 
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Originally Posted by helen-damnation
Like all Airbus FBW, there is an audio/visual warning of dual input. If either pilot takes control with or without saying so (take over PB), there is also an audio/visual warning for that as well. They won't stop PIO/CIO but should reduce the chances/time. Having said that, if you're running out of runway, everyone pull together!
That’s what I call the nice theory behind Flight Crew Operation or Flight Crew Training Manuals but when time runs out and stress level sharply increases there are 2 independent humans trying their best on 2 independent sidesticks and the final mixed output can be very undesirable and therefore counterproductive …

The figures will come out in the report but at this stage that is not something you need to know. In the good old days is was called "commercial in confidence". I've seen the figures and they are correct. You can do the maths if you need to.
A gross error on the TOW could explain what happened by selecting inappropriate high FLEX temp …
To me 225 pax add up for a payload of 25 tonnes but not the double as you indirectly mention. But as you seem to be pretty sure of your figures, is it possible the crew was not made aware of an extra 25 tonnes of cargo … ?
Just one of the possible scenarios …
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Old 23rd Mar 2009, 05:13
  #192 (permalink)  
 
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I'm not for a minute pre-judging the cause of this incident, however for a llong time now I've held a view that very few pilots have any way of judging whether acceleration is correct for the runway in use.


Our rule of thumb is 80kts by 1000" markers or you are heavier than estimated. This would also work for selecting wrong power as the power setting is not sufficient for a/c weight. Works pretty well.

Any others use this?
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Old 23rd Mar 2009, 05:41
  #193 (permalink)  
 
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any cctv footage?

just like the a320 landing on the hudson in the US, any cctv footage of the EK tail strike?
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Old 23rd Mar 2009, 06:06
  #194 (permalink)  
 
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CONF iture

Those figures were the original ones given to the crew on the flight plan. They are used for initial input into the MCDU and are then updated when the flight closes and a final ZFW is given. The fuel requirements are then finalised, inserted in the MCDU & then the performance figures are computed. Any significant change after that should be advised to the crew who would then get new performance figures. You would also check the loadsheet to confirm the ZFW, T/O wt & Ldg wt.
I don't know the cargo set up to catch errors but as I said before, until details emerge, all bets are open: human and/or technical.

To err is human, to really it up just add a computer/stress/more humans/time change/management etc etc
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Old 23rd Mar 2009, 07:56
  #195 (permalink)  
 
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I don't normally get involved on these theads, just a watcher being long retired, but I can't let this on go. When I flew Valiants we had a check time to 100 knots to make sure accel. was OK. If speed was down we aborted, did once, we went off the end, slowly. That check might well have saved Emirates at MEL.

When I converted to civil jets, BOAC VC10s I was surprised that no such check existed, however, it was BOAC so surely they knew best. Some years later as a B737 Capt. I got involved in designing a TOPIS, Take Off Performance Indicator System, it got shelved, not needed, too hard box. The electronics then were not as they are now.

I see no reason why when the performance of a sophisticated electric jet such as an A340, say, is calculated the FMC cannot calculate exactly what the accleration rate should be, considering all parameters such as thrust, temp. flap setting, weight and runway characteristics, and assign THAT rate to one pointer on a scale, on , say, the HSI or ADI The exact acceleration could then be extracted from the IRSs and another pointer driven alongside the other (rather like Concorde's speed/C of G pointers) so a direct comparison could be made between planned accel. and achieved accel. to say, 100k. Should be easy to do AND interpret.

On too many aircraft, certainly those that I have flown, we ASSUME, but do not know, that the tyres (and therefore brakes) are all intact and that the brakes are all cool, and able to accept the energy of a rejected take off at V1.

How many flight manuals contain data on tyre limitations, (although speeds such as TSOC62, 225 mph. if I rememenber correctly are indicated on the tyre mouldings) such as the maximum taxi distance at given weights before the tyres overheat to the risk of possible failure ?

Many years ago I wrote a paper for the International Journal of Flight Safety (only one edition published before the publisher died).

In that I questioned why it was not an airworthiness requirement for ALL jet transports to be fitted with brake temp. guages (sure indicator of a dragging brake as I experienced once on a VC10, ) and tyre failure indicators (like Concorde and even on my BMW) which tells me I have lost one tyre and TWO brakes assuming I want to brake in a straight line. (which I did once in a 737, fortunately during push back when a brand new wheel casting failed).

Does the A340 have brake temp. guages and tyre failure indicators, and what else could cause it to fail to become airborne on a 12,000 feet runway, even at max. gross, except too little thrust or a totally wrong flap setting, assuming the crew (of 4) would have immediately spotted gross overloading or an unexpected large tailwind ?


I believe the lack of information about take off acceleration is one of the last missing pieces in the aviation safety jigsaw, and SO easy to correct with modern electronics. Any constructive comment ?

PS Sorry if I have not used correct AB terminolgy, spent a long time on Boeings, 73, 75, 76, never flown a 'bus.

Last edited by RetiredBA/BY; 23rd Mar 2009 at 10:58.
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Old 23rd Mar 2009, 08:01
  #196 (permalink)  
 
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Retired BA/BY - yes the whole EK Airbus flight has TPIS and wheel temp indications..
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Old 23rd Mar 2009, 08:22
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As for judging the acceleration rate by " feel" , lets not forget that EK MFF policy has the bus drivers flying 3 variants 332/343/345. Each with very unique acceleration qualities. Add a wide variety of weight regimes ( anything from a light 332 going to DOH) to a heavy 345 out of MEL. Also anything from max flex to Toga. Artificial rotation feeling that is different on the 345 to the other two. I recall a ' dead space' at about 2/3 back stick as a result of different rotation logic on the A345.

MFF does have its dangers.
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Old 23rd Mar 2009, 08:33
  #198 (permalink)  
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The Boeing product has a very obvious trend arrow that indicates acceleration during the takeoff roll. Anything under a 15kt acceleration trend and the alarm bells should ring that something is not going according to Hoyle. It is partiularly used for noticing the early onset of windshear. I seem to recall that the Airbus has a similar trend arrow. Someone will correct me if I am wrong.
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Old 23rd Mar 2009, 08:51
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I guess Emirates has a big advertising budget, how else can you explain the lack of any media interest.
Throws into relief what was happening not so long ago to QF, when even a technical delay was enough to generate a "troubled airline" headline.
Very perceptive Capn' Kremin.
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Old 23rd Mar 2009, 08:57
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At 1600Lt MEL today the a/c was in front of the John Holland hangar and being guarded by people sitting on chairs. The damage to the rear 'belly' is covered by tape. A BP tanker was in close proximity. I do not know if the a/c was to be de-fuelled.
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