Concorde power setting on landing
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Concorde power setting on landing
I just read that when a Lightning lands because of the high alpha and being on the back side of the drag curve etc that 30% of the aircrafts lift is being provided by the engines.. .. .Does concorde need lots of power to land for the same reason? If so what are the power settings on landing and how much lift are the engines producing? And is this why it is so loud on landing or is it just loud anyway?
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Concorde is also flown very much on the back of the drag curve on final approach, hence the very high power setting. (c86% N2, quite a lot of thrust at low altitude).. .. .Owing to the nose-high attitude the lift vector from the engines' thrust is significant, but very very much less than 30%.. .. .The practical effects of the above are that you do not consider thinking about even contemplating taking power off above 15ft on landing - the loss of lift vector combined with rapid deceleration from the massive drag will not provide a happy outcome!. .. .Also, when flying with an engine out at low speeds (>350-400kts at tow, say less than 320kts at lw) there is a marked roll input caused by power changes again due to the lift vector proportion of the thrust. This effect is more noticeable as speed reduces.
As WOK appears to have mislaid his calculator, allow me to help with the maths! <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> . .. .A typical Concorde approach attitude, on a 3° glideslope, at the target threshold speed, is around +10.5° PA. The vertical component of the thrust is therefore T x Sin10.5°, which comes out to 0.1822T.. .. .Thus around 18% of the total thrust used on approach is acting in a vertical direction.. .. .Coupled with a thrust line which is well below the C of G, providing a considerable nose up pitch, you can see that it is quite easy for the engines to "push you around" on final approach, an effect that must be anticipated and resisted.. .. .Likewise, with the drag being around double that of a subsonic aircraft of similar weight, this is definitely not the aircraft to get low and slow in.. .. .This doesn’t quite answer your question - which asked what percentage of the total lift is provided by the thrust - but that is a bit more difficult to work out. My guess, for what it’s worth, is that it would be a similar figure.
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I seem to recall something about Concordes using a decelerating approach as far as possible to reduce the thrust requirement and hence the noise.. .. .Over say a 7 mile final and assuming a 250 knot max to start off with, I guess the effect is quite small.. .. .Does anyone have more details about this?
The standard approach on Concorde is the Reduced Noise Approach (RNA), which is flown, usually manually, whenever we have an ILS glideslope available, expect to see the runway by 500R, and can comply with some other minor equipment and runway limitations.. .. .Once on the glideslope, the latter stage of the approach is flown at Vref + 30kts, (min 190kts), down to 800R, where the speed is further reduced to Vref + 7kts, which must be achieved by 500R.. .. .Keen spotters may be able to detect the aircraft pitch attitude increase by about 3° to 4° during this manoeuvre. <img border="0" title="" alt="[Wink]" src="wink.gif" /> . .. .The NHP checks that the approach parameters are stabilised at 500R, and calls "Stabilised". If not, then like any other BA aircraft type, a Go-Around will ensue.. .. .The noise reduction comes from the fact that, being so far up the back of the drag curve on approach, we use less thrust to fly at 190kts than at 160kts, and less thrust whilst decelerating to Vref + 7kts, so, above 500R, we are a bit quieter than if we flew a constant speed approach.
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Hi all,. .. .I may be asking a really thick question (likely), bu can Concorde use its reverse thrusters in the air? I seem to remember someone telling me this or reading it somewhere, or am I talking cr@p ??. .. .Cheers. .. .CP
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At risk of being shouted at from all directions, I understood that reversers are used in flight, during descent, at flight idle power, to help get the aircraft down from height, and slower. If I recall correctly, 2 engines are put into reverse, and on the next sector, the "other" pair are used.
crazypilot. .. .Remarkable, isn't it, just how often those who post vehement and dogmatic replies to questions end up with egg on their face!. .. .Concorde can use reverse thrust in the air.. .. .Irish Steve has it nearly right, however only the inboard engines are used in the air, never the outboards. Reverse Idle only, Subsonic only, plus a few other limitations.. .. .The descent profile is planned without the use of reverse thrust, but it is available, and used, if required.
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DC8-63's used to reverse the inboards on descent for added drag as the speedbrakes were kinda puny. Had a wonderfull system called "bucket dump" which would ensure that the ****** would un-reverse when you wanted it. In the early days of the 747 as the sun rose over the cold dark Atlantic, a P&W rep asked one of the drivers when they had shutdown Nr 4 engine. He said they hadn't, and the P&W guy pointed out that the NR 4 aft sleeve was in reverse. The driver scarpered back to the cockpit as this was news to them, they hadn't felt a thing. I think that this incident and that stupid push-pull cable system prompted Mr Boeing to take the aft reversers off the Queen of The Skies.
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In fact the use of revese at Idle was first used in anger on Concorde's 1st ever commercial flight. . .. .On the trip back from LHR to Bahrain they were getting to ahead of where they needed to be during the decent due to the fact that cooler air was allowing the engines to produce more thurst and that the tail wind was stonger than expected. . .. .So apparently at the suggestion of Test Pilot Brian Trubshaw, who was a CAA observer on the flight, they used the engines in idle reverse to increase the rate of decent so a straight-in approach could be made to the runway and hence no delay on the foirst ever BA service!. .. .-Edited to correct the details, once I found then in a book.. . . . <small>[ 27 March 2002, 17:54: Message edited by: Gordo. ]</small>
