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Pacific Blue Tail Scrape in Sydney

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Pacific Blue Tail Scrape in Sydney

Old 4th Jan 2008, 09:47
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thread drift (sorry)

Indeed.

Ozzies have had 10 years of looking over the ditch at that shambles and yet they still voted for a rosy future of over zealous legislation, do-gooders with no idea of what "good" actually is & pc-ism gone mad.

Maybe it's the new immigration reversal policy in anticipation of aunty and her cronies getting the shaft next year.
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Old 4th Jan 2008, 11:07
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the end result is usually the final hole of the cheese lining up. Brilliant man DR reason
This chap Reason has a lot to answer for. As soon as the smallest incident occurs someone quotes his hole in the bloody cheese thingie which has become the worst repetitive cliche apart from mumbled condolences whenever someone gets knocked off..
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Old 4th Jan 2008, 11:09
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...... but is he wrong????
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Old 4th Jan 2008, 21:22
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...... but is he wrong????
Of course he is not wrong though I do agree with the cliche comments. Like the word "Safety", quotations of Reason often get used for the wrong reasons, for political purposes to win a debate or to polish the outside for public perception. Cry or decree safety to the public eye and you will have all your nay sayers silenced. Managers of airlines, especialy the cheap budget type ones, hate the Reason model as it lays a fair bit of personal responsibility directly at their feet. In the current pilot skills shortage climate, they need to sharpen up and review their responsibilities, perhaps put their hands a little deeper into their pockets as the cracks in their wonderful little, shiney on the outside, airlines are definatly starting to show.
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Old 5th Jan 2008, 00:07
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My point exactly!
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Old 5th Jan 2008, 01:39
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Having used the HGS in QF 73ngs for some time I can imho give creedance to the impending tail scrape warning which I have seen several times on rotate. We didn't have a tail scrape but it did occur at heavier weights with derated power set. We were told that tail scrapes can cost about 1/2 mill if serious to check. Perhaps the business case was valid after all. Any QF drivers care to comment on similar experiences?
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Old 5th Jan 2008, 02:54
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There is absolutely no reason why anyone should have a tail scrape! This mindless need to maintain a constant rate of rotation from 0 to 15-18 degrees nose up that is drummed into us is the cause of these tailscrapes and is completely unnecessary.

My understanding is that as the tailplane descends towards the runway surface as the nose rises from 0 to 10 degrees nose up, the downward force from the tailplane is reduced due to ground effect (pressure between the runway and the underside of the tailplane increases). The pilot feels this as a pause in the rotation at about the 10 degree mark and is countered by pulling back even further on the control column.

As I said this mindless yanking back of the control column to maintain this rate of rotation at any cost is completely unnecessary. Rather than maintaining the rate of rotation at 3 degree per second through the whole manoeuvre, simply reduce the rate while the the attitude is passing through 10 - 12 degrees. It will only increase the time taken to reach the take-off attitude by a second or two. Big deal. It will also prevent a tail scrape.
Remember, the take-off (go) performance is predicated on an engine failure at V1! The fact that you are continuing the take-off on two engines means you have that much more margin over the minimum performance and therefore it is not critical if you reduce the rotation while the aircraft is passing though that point where the aircraft is most vulnerable to runway contact. And the all engine take-off performance has a factor of 15% does it not?

Remember also that:
1. Most runways are longer than required.
2. Most take-off's are done with reduced thrust which have margins built in.
3. Also in my experience, we always enter the take-off charts with NIL wind, regardless of the fact that there is always some headwind available. If there was tailwind, we would enter the take-off charts with a tailwind component much greater than the actual tailwind. For example if there was 3 kts tailwind reported, we would enter the charts with 5 kts tailwind. Again there is extra margin built in over the existing 50% headwind/150% tailwind margin already built in to the take-off performance charts!

I can tell you, if I was flying and my wheels were still on the ground while the attitude was rotating through 11 degrees nose up, I would relieve the pressure on the control column and reduce the rate of rotation to very little until the bird was airbourne. If I was to continue to pull back on the control wheel, I would simply be driving the tail into the ground.

Check out the picture on page 27 of the Singapore Airlines B744 in Auckland. I bet he was mindlessly trying to maintain the 3 degree per second rate of rotation through 11 degrees nose up. In fact I bet when the rotation stopped at that point, he pulled back even harder!

http://www.taic.org.nz/Portals/0/Ann...rt_2003-04.pdf

<sigh>

Last edited by Blip; 5th Jan 2008 at 11:40. Reason: speling :-)
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Old 5th Jan 2008, 08:35
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I can tell you, if I was flying and my wheels were still on the ground while the attitude was rotating through 11 degrees nose up, I would relieve the pressure on the control column
If you are still on the ground rotating through 11 deg in an -800, its too late - you would have had your tail strike.
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Old 5th Jan 2008, 11:35
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Exclamation

Remember also that:
1. Most runways are longer than required.
2. Most take-off's are done with reduced thrust which have margins built in.
Obviously a short haul pilot!

I agree that a lot of times a mindless rotate is the reason for tail scrapes but I disagree with the rationale that the solution in avoiding them is to use a poor technique simply because the runways are longer than required and there is fat built into the 'p' charts. I'd prefer for the right technique to be trained and flown so that when you are confronted with the worst case scenario (and goodness knows it's always the worst situation when it occurs) it all works as advertised. Flying the incorrect way in QF on the 767 or 737 will do the F/O or Captain no good when they transition to the A330, 744 or A380 and are often taking off at MTOW and max thrust and anything less than the right technique in the event of a mishap can mean the difference between flying away and augering in.

All the docs I've read indicate that the overwhelming majority of tail scrapes happen due to a fast rotate from the very start (poor technique) rather than from a 'snatch' through the dead spot at about 8-10 degrees with decreased elevator effectiveness. The tail scrape with SQ happened because they rotated 30 knots too slow. Using the SQ example is somewhat mischievous as it's a far more complex issue than simply the rotate method.

Further, I use the full headwind component to calculate my derate- as you say there is fat built into it- to go easy on the engines. I also tend to not over extend the downwind limit unless it's a 'flukey' wind or light and variable. Don't read into my comments that I'm in any way relying on the 'fat' to get my way out of trouble I've spoken at some length to performance engineers (who happen to be pilots as well) and so I'm comfortable with not having to add extra layers to what is an already multi layered defence.
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Old 6th Jan 2008, 20:59
  #30 (permalink)  
 
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As I said this mindless yanking back of the control column to maintain this rate of rotation at any cost is completely unnecessary. Rather than maintaining the rate of rotation at 3 degree per second through the whole manoeuvre, simply reduce the rate while the the attitude is passing through 10 - 12 degrees. It will only increase the time taken to reach the take-off attitude by a second or two. Big deal. It will also prevent a tail scrape.
So Boeing got it wrong eh? What ever happened to just doing it the way the manufacturer tells us how to do it?
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Old 7th Jan 2008, 00:28
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Now Hear This - Boeing NEVER, EVER EVER get it wrong!!

Now if we were talking about that OTHER plane builder........

All the manufacturers can do is predicate information which can probably be utilised with no problems (or more to the point without having to use any thinking or commonsense) 99.9% of the time in the benign training environment of the SIM where the current trend seems to be to dumb it down to the maximum amount and minimise "the big picture."

All well and good until you throw them out in the real world of real weather and you have little more than trained monkeys to work the flaps/gear and talk on the radio.

OK here's one from FCTM for 73-8: Boeing recommend "avoid rotating during a gust", so there we are at V1+1 and get a decent old gust of wind.
What to do - abort?? Well no, we're above V1 so some explaining to do.
Hold it on the runway until the gust passes?? Well no, not if we want to maintain obstacle clearance if EFATO (assuming high weights.)

"..but Boeing says.."

If you're in the left hand seat and you've tried to do the "normal" rotate but ambient conditions mean you're approaching 11 degrees with the mains still on the deck and you DON'T modify the body angle - well you're in the wrong game however you'd probably be a stunning success as a public servant!
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Old 16th Jan 2008, 15:11
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Blipe wrote:There is absolutely no reason why anyone should have a tail scrape!

I agree with alot of your post. I trust you are also a good operator. One thing to remember though, never say never. Especially when relating to aviation.
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