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Flying on the 'step'

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Flying on the 'step'

Old 3rd Dec 2004, 00:18
  #41 (permalink)  

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Many years ago I was an FO on the 747-100 with -7s. The last 2-300' was a real struggle. In fact the last 500' to crz alt was at about 100fpm. if you just let it level at the crz alt it sat nose high for ages going nowhere with the engines at full chat. So.... the technique was to climb 200- 300' higher than crz alt and "dive" it down to the level. It accelerated just nice and sat "on the step".

It seemed to work.... but then I was only the FO.

With the engineer grumbling behind me.

Eating my chicken.

Happy days.

L337
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Old 3rd Dec 2004, 03:47
  #42 (permalink)  
 
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Much the same on the 'ole straight-pipe 707's, L337, the climb 'n dive worked quite well at really heavy weights.
Don't expect the younger guys will ever have the chance, with the reduced separation margins in favor now.
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Old 3rd Dec 2004, 13:12
  #43 (permalink)  
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Fascinated by the debate this is causing! Got in touch with my old PoF tutor (someone of considerable experience and low bulls**t index):

His view is in broad agreement with Milt/ Astra driver - the step does exist but is a phenomenon associated with older wings, which have a much more 'u-shaped' total drag curve than modern ones. I guess that may explain why Gann talked about the effect and why posters who've flown older stuff also confirm something like a step. He couldn't give me a detailed explanation now but said he would next week - will post it here when I get it...
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Old 3rd Dec 2004, 17:30
  #44 (permalink)  
 
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I think Airbus does that trimming adjustments automatically to reduce drag, like OVERTALK has pointed out, does it not?
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Old 3rd Dec 2004, 20:17
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a phenomenon associated with older wings, which have a much more 'u-shaped' total dra

Would disagree.

Not the 'older design' wing, but plain and simply, a lack of thrust at higher altitudes, with the older straight-pipe engines, and the early fans as well.

If you operated these, you would positively know....first hand.

Been there, done that.

Now of course, much has been learned in the meantime, but I personally consider some of the original wings (B707 for example) were first rate. And yes, vortex generators were employed to steady the low speed laminar flow over the ailerons (both inboard and outboard) but all this considered, the original designers did a very remarkable job, and certainly had the fatigue issue under control, to a large extent.

The fuselage skin crown was a whole 'nother matter altogether....

Been there, done that also...and sadly, a Boeing ain't a Douglas, and never has been.

Donald W. built very fine aeroplanes.

Just ask UPS...they still have a bunch.

Last edited by 411A; 3rd Dec 2004 at 20:36.
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Old 3rd Dec 2004, 20:57
  #46 (permalink)  

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411A's nailed it. (Cheezes cripes, man; you seem to have flown a lotta different planes, eh?)
Lack of thrust/power is it. Nuthin' fancy 'bout it!
I only fly the DHC8, and cannot speak on behalf of any jets, but I tried both techniques the other day -ENBO-ENEV-ENBO- with the *exact* same TOM (OK -granted, 'twas a few pounds +/-, but not than many!). The "step" method (when approved by ATC, of course) used about 10-15sec longer to reach cruise TAS, as opposed to just levelling off and waiting for cruise TAS, maintaining climb power of course... It'sjust a matter of energy management. The psychological effect is the greater...
Modern aircraft have no problems with power/thrust vs. power/thrust req'd, and hence the "step" is just a load 'o bollocks...
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Old 3rd Dec 2004, 21:18
  #47 (permalink)  
 
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L337,

You offer some interesting observations but if you think them through you would see the following;

A/C climb rate = 100fpm
Altitude climbed above desired = 200 - 300ft
Time to achieve this = 2 - 3 minutes
Time to descend back down to desired alt. = 2 - 3 minutes

Total time to establish cruise airspeed, approx 5 minutes

I would suspect that if you had just leveled at desired altitude and waited 5 minutes the speed achieved would have been the same.

Of course, I wasn't there to witness any of this but I also doubt anyone has ever been able to show results for the two methods using the exact same aircraft at the exact same gross weight at the same altitude and OAT. If someone has managed to do this and in each case started their stopwatches the moment the aircraft first reaches cruise altitude and stopped them when the aircraft reached desired cruise airspeed I think they would find that the conventional level off would be slightly better.
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