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Calling V1 early

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Calling V1 early

Old 11th Feb 2006, 19:48
  #81 (permalink)  
 
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Originally Posted by mutt
With all respect to Wiley and JW411...... continue your chat...... otherwise..
Gentlemen i knew the answer to the question prior to asking...... the problem here is that people are quoting from FAR/JAR.Exam questions rather than actual certification limits for a certain aircraft...
Please please get to know YOUR aircraft;;;;;\\\
mutt
The comment was made that better training would have prevented the accident.The comment was not correct.

Would you rather just ignore it?
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Old 11th Feb 2006, 19:59
  #82 (permalink)  
 
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The crew were trained so that, in the event of a failure above V2, they were to reduce speed to V2 and, as you say, they performed exactly as trained. You think that was a good technique to teach?

Last edited by Alex Whittingham; 11th Feb 2006 at 20:14.
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Old 11th Feb 2006, 21:05
  #83 (permalink)  
 
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Originally Posted by john_tullamarine
I didn't mean to come of as some german efficiency/precision expert
Pass, friend ..
The technology is now available to abandon the use of the IAS for the go/ no-go decision
Been the case for a great many years .. but the ASI is still a simple predictor .. especially if one has runway marker boards or uses the stopwatch to monitor acceleration.
Typical tollerances on speed indicators are +/- 3kts that is a spread of 6 kts. Throw that in the RTOW computer and you will see what happens.
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Old 11th Feb 2006, 22:48
  #84 (permalink)  
 
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Originally Posted by Alex Whittingham
The crew were trained so that, in the event of a failure above V2, they were to reduce speed to V2 and, as you say, they performed exactly as trained. You think that was a good technique to teach?
As I understand it, that was *procedure*, not *technique*. So that was what the syllabus and the instructors passed along to the students as part of the curriculum.

But it is not a good procedure as demonstrated. Early on, I was taught you don't change anything if you have a damaged airplane or an airplane with a control problem. You stay at the speed until you have enough altitude and control to find out what the limits of control are. The odd thing is that same concept is taught for an emergency descent, ie.. you descend at max speed unless you have a damaged airplane and then you descend at that speed.

It is unfortunate but we continue to see examples where normal procedures are confused with emergency events, sometimes with disastrous consequence.
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Old 12th Feb 2006, 02:04
  #85 (permalink)  
 
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Originally Posted by mutt
Nope.... I didnt want to talk about it at all..... you are talking about a specific case, I wasnt!
Mutt
My apology. I will try to behave better in the future and not offend you.
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Old 12th Feb 2006, 11:13
  #86 (permalink)  
 
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mutt:

"With all repect to Wiley and JW411.....continue your chat....otherwise".

Otherwise what? Otherwise you will cut off my allowances or otherwise punish me?

Or do you perhaps mean "continue your chat.....elsewhere"?

In any event, I think you are being less than fair. The Chicago disaster was raised by john_tullamarine who, I believe, is the moderator.

Alex Whittingham then made the amazing statement that the accident could possibly have been prevented with better training.

Wiley disagreed with that and so did I.

I don't know where Alex Whittingham (or you for that matter) was 27 years ago but reducing speed to V2 if already above it in the event of engine failure WAS what was taught in those days. The contention was that the net flight path was based on maintaining V2 and that was what we were exhorted to do.

It was largely as a result of this disaster that we arrived at the "climb at V2 but if you are already at V2+10 then maintain V2+10" situation that exists today. A lot of water has gone under the bridge in 27 years.

The crew of the Chicago DC-10 was doing exactly what they were trained to do and that was the conventional wisdom of the day. Their aircraft was ultimately unflyable and even V2+50 would only have given them a few more minutes.

Finally, if you are complaining about thread creep, then remember that it was the moderator that started it! In any event, going from a discussion about V1 to a discussion about V2 is not much of a creep. All in all, I think you are out of order.

Last edited by JW411; 12th Feb 2006 at 13:04.
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Old 12th Feb 2006, 14:07
  #87 (permalink)  
 
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I really have to learn not to post when I'm drunk.... Sorry

I meant to say that i wasnt passing any comment on your discussion, which I actually found extremely interesting.... My comments were jumping back to the posts before yours....

Apologies for the confusion, I will delete the posts so the thread can get back to the topic...

Mutt.
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Old 12th Feb 2006, 19:33
  #88 (permalink)  
 
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mutt:

Thanks for that - apology accepted.
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Old 12th Feb 2006, 19:33
  #89 (permalink)  
 
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JW411, I'm not suggesting your colleagues in the hot seat did anything contrary to their training. I'm suggesting that they were taught the wrong technique for speed control in a jet and that the application of that incorrect technique, by coincidence, killed them as they reduced speed towards V2.

The NTOFP is based on a V2 climb at that stage but V2 as scheduled is often, in fact usually, V2min which is neither the best angle of climb speed nor the best rate of climb speed and can even be on the wrong side of the drag curve. The NTOFP also assumes an engine failure at VEF. Teaching pilots to reduce speed to V2 following an engine failure at a speed above V2 displayed a lack of understanding of both the certification procedures and aerodynamics. It was not the accepted technique on all aircraft or in all companies, just on some DC10 fleets.

This is why I said that, if the crew were better trained, the accident might have been prevented. If they had been taught the correct technique they would not have reduced speed and the wing would not have stalled at that point.
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Old 12th Feb 2006, 19:46
  #90 (permalink)  
 
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Alex Whittingham:

You don't seem to understand that the DC-10 crew were not taught an incorrect technique. 27 years ago it was considered to be the correct technique and it is only with your first class honours degree in 20/20 hindsight that you are able to say now that it was an incorrect technique.

The training given to the crew concerned was approved by the FAA, the CAA and God knows how many other national authorities.

I would guess that you have as many hours on the DC-10 as I have on the Handley Page 42 so let me assure you that whether they had V2 or V2+20 did not affect the outcome - it only speeded up the inevitable. This was confirmed to me by a McDonnell Douglas DC-10 test pilot but then, what the hell would he know?
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Old 12th Feb 2006, 19:50
  #91 (permalink)  
 
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OK. Suit yourself.
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Old 12th Feb 2006, 21:45
  #92 (permalink)  
 
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V1 is an arbitrary number in most cases, set to save money and time in computing the takeoff limits. The minimum V1 would be to satisfy the case of continuing the takeoff, so that the airplane just reached screen height at the end of the takeoff distance (also limited by Vmcg). The maximum V1 would satisfy the case where the airplane rejected the takeoff and just stopped at the end of the emergency distance (also limited by Vr or V2).
The only time this is likely to give the same V1 is for a perfectly balanced field, something that rarely exists.
So it is possible to calculate a range of V1s for every takeoff and for the pilot to choose a figure somewhere in the middle, or, if she sees a reason to use the minimum (obstacles close in, poor runout surface, contamination etc) would choose the minimum V1 and for a longer runway or obstacles further out, or for considerations of wind shear, traffic etc would choose the Maximum V1.
In practice leaving this decision to pilots is hazardous, not to say contentious, so most companies use Boeing takeoff figures that use a standard V1/Vr ratio for the whole chart, or in the case of the CDU calculations, the entire program. Sure it is within the range, but is it the best speed to use?
You can figure the maximum V1 by looking at the speed appropriate for the runway for a takeoff at maximum TOW (up to the Vr speed for the current weight of course). If you are equal to or lighter than that, that V1 speed will work for you and will also cover the continued takeoff case. I hesitate to suggest an easy way to calculate the Min V1, but if a takeoff is acceptable when the runway is contaminated and the V1 is 20 knots or so below standard speeds, then it should also be OK when the runway is in good condition.
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Old 12th Feb 2006, 21:52
  #93 (permalink)  
 
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JW411

I think that you are perhaps being a little aggressive here. At least Alex Whittingham is using his name on this forum. He is one of the most well known and highly respected trainers in JAR ATPL subjects in the UK.

His point is well put but perhaps you are undestandably sensitive and 'close' to the particular example discussed on this subject, hence the tension. Have a think about it and perhaps come back with your thoughts when things are a bit calmer.
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Old 12th Feb 2006, 22:04
  #94 (permalink)  
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Gents,

A bit of heated discussion here .. a chap goes off for the weekend and these things generally happen ... Perhaps we ought all to take ten deep breaths and start again.

For one, I see the basis of a very useful and rational discussion in this thread and the ideas being canvassed are important for folk to contemplate.

Just to throw a few more comments into the pot ..

(a) Sorry J_T, although the takeoff can be continued at a Flex/Derated thrust

Mutt,

Granted, but IF the hapless pilot pushes the levers up too far (or, in some cases, too quickly), the situation can be very different ... as we suspect was the situation in the accident vaguely alluded to ... crash, burn, die for crew and numerous folk behind them ... It is noted that my comments depend on the engine control systems.

(b) I don't believe it 'better training' would have changed it

Wileydog3,

Probably the discussion was getting a little bogged down in semantics along the way.

The general thrust of pilot training programs needs to be (and is) driven by pragmatic (and defensible) risk assessment, control, and management considerations. That is, the training has, as its aim, to condition pilots to respond to situations in a manner which, on the great majority of occasions, will have a high probability of a successful outcome. It is for this reason (why confuse the issue ?) that many training programs shy away from training exposure to low probability emergency scenarios .. while I don't agree with that, personally, it is a very logical and defensible argument.

Training then, and now, still emphasises the very sensible option of flying it in a manner which is consistent with the certification. I suggest that Alex and I have no criticism of the crew in the O'Hare accident .. they did the best they could in the circumstances of the day (and, indeed, no doubt as they had been trained)... it is a matter for extreme regret that things didn't quite work out for them as they would have hoped. As to what the outcome might have been had they hung onto the speed delta at the time is a moot point .. but it may have been better than that which ended up in the historical record ..

And we probably ought not discount the part played by Lady Luck (call it what you will) in all of this .. in the other example raised, the Sioux City outcome could conceivably have been far better had the crew not been caught out by the phugoid on late final .. it all comes back to the numbers game.

However, the point still remains that normal training programs do not offer an iron-clad guarantee of a happy outcome .. only that the odds are very heavily weighed in that direction. In fact it is not unreasonable to suggest that there are no hard guarantees in life ... only probabilities.

It is interesting to note that the test flying fraternity ... the training these folk get is a tad different to the airline line pilot's .. probably would side with the suggestion that when something goes bang generally it is preferable to leave other parameters as they are rather than potentially increase the problems associated with whatever it was went bang ... and I note that you side with this argument yourself in a later post. I suggest that Alex's comment about better training probably should be read in terms of better understanding ?

Should crews pitch up to the V2/V2+whatever target in the event of a perceived engine failure ? ... of course ... in general .. as that action will give a high probability of a desirable outcome .. but not a guarantee.

At the end of the day, one of the big problems we face in the training arena is how much information to give and how best to control outcomes .. there is no simple or easy answer.

(c) thread creep

Not at all an undesirable thing, in my view. A significant value of tech log is the potential for education in that we have some highly qualified, experienced and knowledgeable folk in this sandpit. Often a turn in discussion can entice some of these folk out from the sidelines to offer valuable comment.

(d) OK. Suit yourself

Are we all going to agree all of the time ? Of course not. Main thing is to keep the discussions alive and the civility high so that people are encouraged to participate and, hopefully, learn a bit here and there along the way.

Last edited by john_tullamarine; 12th Feb 2006 at 22:31.
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Old 12th Feb 2006, 23:15
  #95 (permalink)  
 
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Thumbs up

John, very integrated understanding of reliability and diagnoses in aviation. Salute!!! Would maybe worth it to mention that:
Climb Gradient Relative to Speed in a Specific Flaps’ Configuration
If one engine is lost before reaching V2, then the initial climb is flown at V2. If thrust is lost at a speed between V2 and V2+10, then the current speed is maintained, to ensure the most efficient climb speed. It is not necessary to increase pitch, in order to reduce the speed to V2, when a higher speed has already been reached.
Cheers.
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Old 12th Feb 2006, 23:53
  #96 (permalink)  
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.. or, to take it a step further in description .. in general,

(a) V2, even with an overspeed schedule (improved climb performance for the Airbus folk), will not produce the best OEI climb gradient performance. (If your bird doesn't have these refinements, then V2 will be linked directly to RTOW).

(b) the best OEI climb will occur at some higher speed which will vary with Type.

(c) to get the best climb will require an unacceptable speed delta above minimum V2 (considering distances required to get to this speed, whether on the ground or inflight)

(d) a reasonable and practical upper limit seems to be around minimum V2 plus 20-25 kt.

(e) the normal V2 and V2+10 guidance is based on a sensible balance of good climb and distance taken to accelerate to a better climb performance speed.

(f) hence ..

(i) if below V2, things are really bad, so let's get to V2.

(ii) if a little above V2, things are good (better ?), let's hang onto it.

(iii) if a substantial margin above V2, let's split the difference and hang on to a bit of it but not so much that we might invalidate some aspects of the takeoff calculations. The actual margin used as the target is a matter for OEM guidance and operator SOPs.

.. and, if there are very unusual noises, bangs and the like... or the aircraft is flying decidedly differently to what you would expect ... let's do things in a measured sort of way so that there might be some useful indication if we are heading towards a more perilous circumstance ..

Last edited by john_tullamarine; 13th Feb 2006 at 00:09.
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Old 13th Feb 2006, 03:36
  #97 (permalink)  
 
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Just to clarify!

We call V1 five KNOTS early not five seconds...
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Old 13th Feb 2006, 19:21
  #98 (permalink)  
 
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deeceethree:

I thank you for your input and I thought I would get back to you when the dust had settled as you requested. After long consideration I don't really think that I owe Alex Whittingham an apology for we are all entitled to our opinions and just because he is a wonderful groundschool instructor doesn't mean that I cannot disagree with him.

I have been training pilots to fly three and four engined aeroplanes since 1967with a great deal of success but that doesn't mean that Alex is not entitled to disagree with me.

Indeed, the late Sandy Thompson, who was a great groundshool guru and for whom I had the utmost admiration, used to be one of my navigators but I still reserved the right to disagree with him.

Finally, most of us on this forum prefer to remain anonymous for obvious reasons but some folks who are not worried about the possible implications for their employment are happy to use their real names. In this case it can pay to advertise.

In your case I am pleased to see that you are following Alex's example but I am wondering how your future wife is going to enjoy being called Mrs deeceethree!
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Old 13th Feb 2006, 19:33
  #99 (permalink)  
 
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No apology required. For the record, PPRuNe asks people involved in the flight training industry to make their identities known when they post so that there can be no suggestion of sneaky advertising under a pseudonym. As you see, it's always a bit of a double edged sword.
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Old 13th Feb 2006, 20:00
  #100 (permalink)  
 
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Alex:

Thanks for that; I had no idea that Danny demanded a "handle" but I can now see why.

For the moment we can consider the hatchet well and truly buried but that is not to say that we might have a disagreement in the future!
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