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BBC TU144 / Konkordski article - for interest

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BBC TU144 / Konkordski article - for interest

Old 2nd Jun 2016, 17:57
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Great response John, very insightful. I had not appreciated the hammering that the Concorde tyres had to endure. Am I right in thinking that much of the low speed lift on Concorde was achieved through the small "whiskers" ahead of the forward doors ? Do they help generate the low pressure vortex above each wing ? If so, then what amount do they contribute ?
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Old 2nd Jun 2016, 18:17
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Hi B

I think they were there to locate the vortices so that their origin did not wander about fore and aft and cause big trim changes by doing so.

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Old 2nd Jun 2016, 18:35
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Strakes are there to generate vortices at high AoA (they do nothing in cruise). These vortices sweep up to the upper section of the fuselage and keep the airflow attached so the fin works in clean air at high AoA (landing and T/O). Some of the Concorde books show dye flow photos that illustrate this.
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Old 2nd Jun 2016, 20:36
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Thank you both, every day is a day in the classroom.

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Old 2nd Jun 2016, 20:58
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IIRC the small strakes are there to keep the flow attacked for the fin, while the extended leading edges (what we would now call "LERX") generate huge vortices over the top of the wing to increase the lift coefficient at high AoA to reduce approach/landing speeds (already discussed in much detail here).

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Old 2nd Jun 2016, 22:48
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Originally Posted by DaveReidUK View Post
Yes, you'd have thought that over the years the Russians would have thought of some new places to stick the wings, tail and engines
Well they certainly did with choppers ...
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Old 3rd Jun 2016, 02:12
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Old 3rd Jun 2016, 05:02
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Originally Posted by DaveReidUK View Post
Yes, you'd have thought that over the years the Russians would have thought of some new places to stick the wings, tail and engines, rather than the same old boring, conventional locations.
If you've ever tried to design an airplane from scratch, you'll quickly realize there is a reason they all tend to look the same.

Back when I was in college, we had a class on aircraft design - a really interesting class literally taught by the guy who wrote the text book . For our grade, we had to design an aircraft - either individually or as teams of two. One guy took some promotional materials for a "new kind of airplane" - STOL using ducted fans and such - from a startup company trying to raise funding. Short story, he simply couldn't make it work - things like CG and CP were all wrong, it would have been extremely heavy and very fuel inefficient. At least the guy had a sense of humor - when he did his presentation at the end of the class he put up a slide of 'the vision' from the promotional materials, followed by a slide of 'reality' - literally a streamlined brick Not surprisingly the company quickly disappeared without a trace - it wouldn't surprise me if it was scam.
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Old 3rd Jun 2016, 10:21
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At risk of straying too far from the topic, the Russians were accused of simply repeating the Space Shuttle Orbiter design with the Buran. If you wanted to design a re-entry vehicle with a payload bay which would be capable of performing "cross range" manoeuvres then it is very difficult not to come up with the same answer. A blended wing / body would be far more challenging.


Cross range was a US military requirement for Vandenberg single polar orbit launches. The plan was to launch a shuttle, retrieve an object from orbit and then land. The earth will have rotated 20 degrees or so east during the 90 minute flight hence the need to fly cross range on the return. I guess the Russians wanted to do the same so the design was a foregone conclusion.
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Old 3rd Jun 2016, 11:22
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@WHBM -
Well they certainly did with choppers ...
What was the name/no of this pterodactyl-like Soviet machine?
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Old 3rd Jun 2016, 11:40
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Originally Posted by Phoenix1969 View Post
@WHBM -

What was the name/no of this pterodactyl-like Soviet machine?
Mil-12. A 4-engined helicopter. It is really two Mil-6 twin engine choppers bolted side by side. It was designed to carry ICBMs which had been distributed by the Antonov 22 heavy cargo aircraft onward into remote launch locations in the forest.


https://www.youtube.com/watch?v=hdiXJZjZ5Cs
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Old 4th Jun 2016, 02:42
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If you've ever tried to design an airplane from scratch, you'll quickly realize there is a reason they all tend to look the same.
Then why doesn't a VC10 look like a DH Comet like a B707/DC8, a F28 like a Bae146, a DC9 like a B737, a SF340 like a Do328 like a Shed360 like a DHC8, a DC10 like a B747 and WTF was a BAe ATP supposed to look like?
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Old 4th Jun 2016, 06:14
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Phileas, once someone comes up with a better idea, well it's hard to keep a secret when it's in plain view.
Boeing decided putting the engines on pods under the wing worked better back on the B-47. It's been a long time since anyone has designed a new subsonic airliner with the engines buried in the wing.
Similarly, putting engines in the tail works well so long as you precisely know the weight of the engine package. The problem is, engines have a bad habit of gaining weight - especially when the thrust ratings get bumped up. As a result, late production 727s carried several hundred pounds of ballast in the nose. The MD90 was much worse - fan blade out loads drove massive weight into the engines late in the program, and the required nose ballast was around a ton. That's a lot of lost payload/increased fuel burn and even ex McD engineers that worked on it admit the MD90 is not a very good airplane due to the extra weight. As a result, it's been decades since anyone designed an entirely new subsonic airline with engines in the tail (MD11, MD90, and MD95/717 all being derivative designs).
So, the A380 looks a lot like a 747 (but with an ugly fuselage), the A350 is hard to distinguish from a 787, and a 777 looks a lot like a 767 that got scaled up.


Until someone makes a new breakthrough that works - such as blending wing/body - it's going to be really hard to tell the difference between any new design twin engine aircraft from a distance, especially when there is nothing to gauge the size by...
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Old 4th Jun 2016, 07:38
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Originally Posted by tdracer View Post
Until someone makes a new breakthrough that works - such as blending wing/body - it's going to be really hard to tell the difference between any new design twin engine aircraft from a distance, especially when there is nothing to gauge the size by...
Some are a bit easier to tell apart.



Originally Posted by Phileas Fogg View Post
and WTF was a BAe ATP supposed to look like?
The ATP is basically a warmed-over Avro/HS/BAe 748, which in turn was intended to be a DC-3 replacement (a role it only partly managed to achieve) and shared the same basic configuration.
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Old 4th Jun 2016, 09:18
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The ATP is basically a warmed-over Avro/HS/BAe 748
Besides them trying to market it as a STOL unpaved strips aircraft, I believe one or more incidents at Portsmouth Airport, the Avro 748 was a good aircraft, still flying today.

By comparison the BAe ATP looked, nor performed, anything like it and was a piece of .....

That said, I did do some contract work for one (one aircraft of the type) ATP operator and they remarked that per bum on seat the fuel economy was remarkably good.
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Old 4th Jun 2016, 09:28
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it's going to be really hard to tell the difference between any new design twin engine aircraft
Ahem:

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Old 4th Jun 2016, 09:28
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I am rather puzzled (it doesn't take much) why manufacturers have not adopted a canard layout. Having an upside down wing at the back seemed daft to me when I first learned about it as a spotty teenager. I hoped that airframe development would eventually see sense, swap the arrangement around and have a foreplane that generated lift instead of wasteful downward force. In general terms, having a vortex above the main aerofoil section appears to be a good thing e.g. the fin / strake / widget on Airbus engine cowlings. Could a lifting foreplane also generate a vortex at the tip which could then be used to enhance the performance of the main wing ? I would be grateful if a genuine expert would please explain to me why this has never been adopted for airliners. Mr Rutan's aeronautical carriages seem to do rather well.


To while away the time before we see blended wing airliners take to the skies and to keep the thread on track, here is another TU-144 article.


TU-144 Flying Laboratory | NASA
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Old 4th Jun 2016, 10:13
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Originally Posted by Phileas Fogg View Post
Then why doesn't a VC10 look like a DH Comet like a B707/DC8, a F28 like a Bae146, a DC9 like a B737, a SF340 like a Do328 like a Shed360 like a DHC8, a DC10 like a B747 and WTF was a BAe ATP supposed to look like?
Because they were all designed to different sets of requirements at different times and different technology states.

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Old 4th Jun 2016, 10:39
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Originally Posted by B Fraser View Post
I am rather puzzled (it doesn't take much) why manufacturers have not adopted a canard layout. Having an upside down wing at the back seemed daft to me when I first learned about it as a spotty teenager.
The problem with the canard layout is making it intrinsicly safe when stalling whilst maintaining efficiency. With a tail-at-the-back design you can arrange the neutral point so that either the wing or the tailplane stalls first and still get safely close to maximum lift coefficient when needed. If the wing stalls first then the nose drops, reducing AoA and promoting recovery. if the tailplane stalls first then the nose drops, promoting recovery.

With a canard layout it's very different. It's ONLY safe if the foreplane stalls before the mainplane. If the mainplane stalls before the foreplane then the aeroplane pitches nose-up (or pedantically "tail-down") and drops into a deeply stalled condition with no available pitching forces that would pull the nose down. recovery would need to wait for it to drop into a tailslide which (hopefully) would then yaw around into a nose-down condition from which it could recover. This will take a LOT of height. To minimise the risk of this condition a canard must be restricted such that it can never get the mainplane close to Cl(max), and as a result a canard needs to carry more wing for a given loading and landing speed, so the drag is higher and the efficiency is less.

There are other, lesser, issues. The foreplane creates a downwash, and it must not be allowed to impinge on the mainplane because it changes the local AoA and stuffs up the efficiency of what should be the most efficient lift-generating area of the wing (the inner wing area). To avoid this you need vertical seperation, which either needs the foreplane to be about eight mainplane root chords higher than the mainplane, or about two below it. The former isn't achievable because of the effect it would have on forward keel area, and the latter is only achievable if the mainplane is mounted like the tailplane of a C5A or VC10. Aside form the weight penalty of a fuselage structure stiff enough to mount the mainplane up there, the result would place fuel tanks and engines a long way off the ground with consequent issues for refuelling and engine maintenance, never mind the required deep maintenance hangar design.

Finally, it's true that a canard generates lift, but you don't really want to generate much of the overall lift with a smaller surface because compared to the mainplane it either has lower aspect ratio, short chord, or both. And that means that the lift it develops comes at a much higher (drag) price than adding the same area to the mainplane would achieve - the same reason why biplanes fell from fashion as soon as we learned how to make cantilever wings that didn't need the extra moment of inertia available from braced-truss multiwing layouts.

There are other reasons, but those are the main ones.

Also "blended wing" configs are very popular as university student projects, but they're not really suitable for line service. One reason is that there's nowhere to put the fuel, but the main reason is that you can't design a "family" (like the A318/319/320/321) as there is nowhere to easily "stretch" then to adapt them for different mission profiles.

0.03 supplied,

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Old 4th Jun 2016, 11:08
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Thanks for that post, PDR. Things are now a little clearer for me too.

I think I'd mentioned it a while back on another thread, but a former Chief Project Engineer with BAe, Roy Braybrook, was firmly of the opinion that ..
"The best place for a canard is on someone else's aircraft".
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