Excel aborted t/off at MAH

[Gorgon]

According to a passenger Excel flight from MAH to LGW last Sunday aborted T/Off almost on lift off. The flight deck eventually told the pax that it was an airspeed indication problem.
Obviously it took some time for the problem to manifest itself .

[Notso Fantastic]

Please beware the way you report incidents. Pilots always check Airspeed indicators at some point around 80 kts when they are indicating something sensible, and this is where the problem would be noticed and the stop decision made, not 'almost on lift off'. Where did that estimate come from? It was not 'the flight deck' that told the passengers what it was, it was 'the pilots'. You have made a false report then finished off with a conclusion: 'Obviously it took some time for the problem to manifest itself'- well, it takes time if there is an airspeed indication problem because they take a little while to start indicating correctly, and by 80 kts the pilots will check them.
Please stick to basic facts without drawing any uneducated conclusions.

[2 Liter Peter]

Thanks for reporting this, Gorgon. Interesting to read.

Don't worry about Notso Fantastic getting antsy. She may have some valid points, but I personally couldn't get excited about the difference between pilots and flight deck.

And of course, pilots don't always check airspeed indications. Alas there have been failures to check when the indications were wrong or missing, resulting in getting airborne without good air data, so most of us these days concentrate real hard for the 80 or 100 knot call and the cross-check.

Of greater import might be the problem one might have at Menorca on the southerly runway if one decides late to try and stop. The cliff just beyond the runway end is particularly uninviting. Anyone know which runway was in use ?

[Paracab]

I think Notso has made some very vaild points.

How can the 'almost on lift off' (?) point/speed be judged anywhere near accurately from the cabin.

[Fred4000]

I wouldnt get so over critical about little points in an otherwise interesting post.

[Joyce Tick]

Why are pilots so terribly touchy - are you all a bunch of girls?

I heard farmers on Radio 4 this morning being called a load of moaners (bit like pilots, I suppose), for whom the weather is never right, while they all drive around in new Range Rovers... However, they all took the flak and continued to argue their point without crying over the insults.

Why can't pilots be REAL MEN, so to speak?

[AngleAndAttack]

Tick As A Brick ,

Suggest you stick to your farmers.






:yuk:

[rosario]

Excel did not have a/c in MAH on Sunday -so again more incorrect infomation
It might useful to know what type of a/c was it? and of course a flight number.

[toon]

i can see it now -

'jet seconds from disaster as pilots struggle with stricken aircraft '

'a passenger was reported to say that they were "nearly airborne" !

what a load of crap. stick to farming.

[prb46]

Surely to ask a question based on a passengers comment,who
obviously knows little about aviation,and to make a heading
that states 'Excel aborted t/o at Mah' should have some further back up.I was on shift that day,and as previously said,Excel did
not have any 737,757,767 and hopefully not a 747 in MAH,otherwisewould be an interesting thread.If any flight was involved with an abort at point before lift off I would suggest that tyres and brakes would need to be looked at.It also would have been on pprune long before a passenger makes such a comment.
A bit of Excel bashing perhaps,or did the passenger not know
what airline he/she was flying with,or perhaps the mind was a bit
of a blurr,and didn't know what day it was,or was it actually MAH?Such an incident would have been reported to engineering and operations,otherwise the pilots must have been brilliant at doing
a great cover-up.

[Old King Coal]

2 Liter Peter w.r.t. your comment 'Of greater import might be the problem one might have at Menorca on the southerly runway if one decides late to try and stop. The cliff just beyond the runway end is particularly uninviting'

Come on mate, reading some of your other postings it would seem that you’re a professional aviator piloting large jet aircraft for Public Transport, so at some point you’ll have studied Performance ‘A’ and similarly you’ll possess a thorough understanding of what Perf ‘A’ both provides and limits you to upon a daily operational basis, i.e. as implied through, and courtesy of, your ‘Airfield Analysis’ ( e.g. the pages in your Ops Manual / Part C, which you consult prior to every departure ) which contain a tabulated equivalent of your Aircraft Flight Manual, with appropriate ( i.e. as required by Perf ‘A’ ) performance assessments and safety factors built-in ( i.e. net versus gross, climb gradients, max take-off weight that will allow a RTO to be initiated at or below V1 and bring the aircraft to a stop on the runway / stopway, etc ).

Needless to say, and as I’m sure you'll appreciate, 'if one decides late to try and stop' [sic] is total anathema.
Indeed, professional airline pilots are tested in the simulator ( every six months ) where part of that testing process includes a requirement for us to demonstrate that we will not attempt to stop when going faster than V1 - wherein this assumes that one knows what V1 is, and understands the how, why, wherefores and relevance of V1 to airfield performance data calculations – which you do, of course.

Accordingly – and regardless of whichever runway is in use – I fail to understand your comment about a cliff being at one end ( or not ) at MAH; wherein, w.r.t. professional aviation and conducting an RTO, just what has a cliff, or indeed a mountain, or a brick wall, or a terminal building, or etc..... being at any end of any runway got to do with the price of fish ?! :rolleyes: It’s an irrelevance, one which is taken care of in the performance calculations; surely ?

( 2 Liter Peter, this is not aimed at you ) Imho, PPRuNe’s become overrun with people who seem to be neither professional pilots ( or even pilots at all ) and / or not professionally involved in aviation, but for whom it seems quite the case that they (strangely) seem to think themselves qualified to pass comments upon subjects which they plainly know little or nothing about – and then feel they have the right to ridicule the genuine professionals who point out their error(s). :mad:

Above edited for typos.

[Final 3 Greens]

Old King Coal

I quite understand your frustration. As a PPL with several hundred hours on light singles and twins and 15 hours in a sim (with TRE), I have enough understanding of line ops to know how little I know ;)

It's a shame that pax don't have access to a "flying for dummies" type of guide, that would explain in simple terms things like what V1/Vr is and how runways are factored etc.

The guide could also explain why it's important to observe the seat belt sign etc and generally create a low level of airmanship that would help the cabin crew.

If there's an upside to your frustration, it must be that you and your airline colleagues are educating some of your pax, as irritating as the process can be at times :D

[eal401]

feel they have the right to ridicule the genuine professionals who point out their error(s).
Sorry, but a genuine professional would explain in a manner that would not require such behaviour.

And many individuals do explain in such manner and therefore are of great benefit to the industry and those who use the industry. Regretably there are some whose egos do not allow such behaviour or consider themselves of higher intellect etc. who feel the need to patronise.

[2 Liter Peter]

Well thanks, OKC, for your tribute and picking up the point about the over-run at Menorca. You are of course absolutely right to declare the basics of performance mean that there is never a problem, and that decisions to stop above V1 are anathema. Might one perhaps explain a slightly different angle of view ?

There is a school of thought that goes that V1 is all about engines failing. If they haven't failed, but something else has, you don't actually have a performance problem with a "go" decision, even from way below V1 - the jet will still eventually fly, and very comfortably clear obstacles, like on every other normal take-off. You may of course have other problems, as would be the case with all your pitot heads full of bees.

By contrast, the closer you get to V1, the more you do have a performance problem with trying to stop. Especially with all the factors that can insidiously prejudice V1 - worn brakes, extra luggage weights, tarmac air temperatures way above tower quoted temperatures, you can probably name a few more. Even more especially if your airspeed readout is unreliable : who knows at what real speed that 80-knot or 100-knot call came ?

Flying off over a cliff still with all engines running might perhaps seem like a good idea in decent weather, even with dodgy airspeed readouts, compared with the alternative of trying to stop from a decision necessarily taken at an unknown speed close toward V1 faced with that slope down to the uninviting cliff to topple over if you got it wrong.

So one was interested to know which runway was in use, and whether it was a factor. This all might be a little academic, as prb46 and rosario have pointed out that this incident has not happened.

[Old King Coal]

Thanks for that 2 Liter Peter, wherein I hope you don’t mind if I pursue this a little more – if only for the enlightenment of some of the laymen in our midst, w.r.t. the thought processes and actions involved in a take-off.

NB. The following is plagiarised from various sources but is, hopefully, fairly succinct wherein it contains a revision of some of the Perf A principles w.r.t. take-off and V1 stop / go decisions.

Enjoy........

The regulations require that the risk of an event occurring is defined and wherein those definitions are as follows:

Frequent - Up to 1 / 1,000
Likely to occur often during the life of each aeroplane.

Reasonably Probable - 1 / 1,000 to 1 / 100,000
Unlikely to occur frequently but may occur several times during the life of each aeroplane, e.g. Engine Failure.

Remote - 1 / 100,000 to 1 / 10,000,000
Unlikely to occur to each aeroplane during its life but may occur several times during the life of the fleet, e.g. Low speed over-run, or Failure to achieve Net Take-Off Flight Path (NTOFP).

Extremely Remote - 1 / 10,000,000 to 1 / 1,000,000,000
Unlikely to occur in the life of the fleet but still possible, e.g. High speed over-run, Ditching, Double engine failure in twin engine aircraft, Hitting an obstacle in the NTOFP.

Nb. The use of ‘Fleet’, both in the above and what follows, refers to all the aircraft of a particular type, as produced by the manufacturer ( and not to a particular airline’s fleet of that type ).



In early stages of an aircraft’s development there will only be a few pre-production aircraft to test, all usually flown by test pilots. The data produced from these test flight is known as ‘Measured Performance’.

Given: The newness of the airframe & power plant
The skill levels of the Test Pilots
The accuracy of the test parameters, e.g. precise measurement of aircraft weight, etc
The need to deliver a commercially viable / saleable aircraft - measured performance is invariably better than the fleet average.

As can be seen ( and as would be expected ) some aircraft will achieve a better than average Rate of Climb, some worse, but most cluster around the average.

http://www.honesthorses.com/images/BellCurve1.gif

From the context of aeroplanes, this average performance of an aircraft fleet is called ‘Gross Performance’.

Gross performance assumes that the fleet is properly maintained and flown in accordance with the techniques described in the Aircraft Flight Manual (AFM).

You are as likely to not achieve Gross performance as you are to achieve it.

Whilst Gross performance is a good reference datum for the performance calculations, it does not however provide an adequate safety margin for Public Transport operations as, by definition, half of the fleet will not attain Gross performance.

Putting it another way, if you were to base your performance calculations using the average of the aircraft fleet ( i.e. Gross performance ), when an engine fails during your take-off roll, you’ll have a 50:50 chance of getting away with either stopping on the runway / stopway or climbing safely away !

We could of course build and operate an aeroplane so that the risk of accident was infinitely small; this would be exceptionally safe but the cost of air transport would then be moved beyond realistic limits. That said, as safety margins are reduced profits increase ( to a degree ;) ).

So, given that Gross Performance is not always going to be safe enough, just what is an adequate safety margin ?

The risk level considered acceptable is that there should only be a one in one million ( 1 : 1,000,000 ) chance of a system failure that is then followed by a failure to achieve the regulated required level of performance.

This level of performance is called ‘Net performance’.

Net performance is Gross performance that has been reduced by an amount to allow for such things as, e.g. variations in piloting technique.

If an event is statistically highly likely occur, e.g. a normal climb conducted without an engine failure, there will be a large margin between the Gross and Net performance levels ( i.e. equating to a high safety margin existing between the two levels of performance ).

On the flip-side, if an event is statistically unlikely to occur, e.g. an engine failure at an exact point in the take-off run, then the difference between the Gross and Net performance will be very small ( i.e. a low safety margin between the two levels of performance )

It is worth noting that performance planning to ‘net performance standards’ keeps the risk of an accident to an acceptable ( read, ‘very low’ ) level, but it does not reduce it to zero, even if the correct techniques have been followed !

This bell curve shows the difference between net & gross performance for a likely event, e.g. All Engines Rate of Climb.

Nb. As a ‘likely event’ it has a high level of safety… i.e. 1 : 1,000,000, and thus had it been drawn to scale, the (red) shaded area would represent just one millionth of the total area of the bell curve.

http://www.honesthorses.com/images/BellCurve2.gif

If an event is unlikely then the improbability of the event is used as part of the safety factor.

This following bell curve graph shows the reduced safety factor in the engine-out case:

http://www.honesthorses.com/images/BellCurve3.gif

However, if an event is so unlikely that the probability of it happening is assessed as being already less than one in a million then the safety margin between Net and Gross performance reduces to zero.

A less obvious, though much more important, example is the engine failure on take-off, i.e. if you have an engine failure during take-off, there are no safety margins remaining !
I.e. the implication of the lack of safety factors, following an engine failure at V1, is that if you lose an engine at V1 you are now down to Gross performance, i.e. you have a 50:50 chance of making 35ft ( and / or 15ft with a wet V1 ) at the end of the Take-Off Distance Available / TODA.

This in itself this is not particularly disturbing, however looking at the factors considered when working out the Take-Off Distance Required / TODR ( and ergo the Emergency Distance Required ) The all engines gross distance to 35ft multiplied by a factor of 1.15 ( a likely event therefore large / 15% safety margin )
The gross distance to 35ft, an engine having failed at dry V1[i] ( note no safety factor ); or
[i]The gross distance to 15ft, an engine having failed at wet V1 ( note no safety factor )…… we find that, w.r.t. the Emergency Distance Required, there are no safety factors built into this; beyond the improbability of an engine failure at V1.

Ultimately this means that, if you have an engine failure at V1 at your MTOM ( RTOM ), you only have a 50:50 chance of stopping by the end of the stopway.

This is very significant and accordingly has lead to shift in philosophy to avoid high speed aborts ( albeit except in certain exceptional circumstances, e.g. aircraft won’t rotate / jammed controls ).

As 2 Liter Peter correctly surmises above, it’s considered much safer to take-off when close to V1 sort the problem out and then land with all of the runway in-front of you, than attempt to stop with much of the runway behind you. :eek:

[Farrell]

Ummmmm.........thanks for that! :E

[2 Liter Peter]

Well, OKC, there must be many of us simply awed by your level of scholarship - and by your ability to write or scan it all in without error so quickly.

Thank you - have not seen such a fulsome dissertation since the famous well-copied Airworld Performance booklet of the mid-nineties. You have added comprehensive chapter and verse to the reasons why one needs to be careful about high-speed aborts.

[Old King Coal]

Wasn't the AirWorld booklet cripped from Air Europe's ? - wherein I only have a few bits of those AE years left-over as keepsakes, and that tome ain't one of them.

[password]

How do these people get to be so clever ???

[normal_nigel]

Password

Since when has boring people to death been clever?

NN