Posts about: "PPRUNE" [Posts: 45 Page: 1 of 3]¶

I beg to differ Christiaan. I am certain your Concorde participation story would be of great interest to the aviation community. The project was a considerable undertaking and is made even moreso when you consider that almost 50 years after its' inception there has never been another aeroplane that has come within a mile (1,852mts) of having the performance of her; military included.

I would hate for all the little tit bits of this important part of aviation history be lost.

There is a thread in the Military Forum called Gaining An R.A.F Pilots Brevet In WWII where we are privileged to share some the personal stories of the heroes involved in that war. It is critical for our future generations that these stories are known and the participants, their stories and contributions are not forgotten. While Concorde was not part of any military conflict it is still important that the personal side of this massive engineering feat is not lost.

The technical information that you and M2dude are providing is absolutely absorbing but equally so are the personal contributions. An example is the mention above of the Air France and British Airways Concordes passing each other. Anecdotes like that are unlikely to be in the Concorde history books and I am sure there are thousands of other pieces of information like that from both the ground and air that will eventually be lost for all time unless we can get it written down somewhere. Where better than here.

Quick link to Bellerophon 's post #66 and photo to save you having to 'leaf' back...
G-BOAE at Mach 2

Much as I look at that picture, I can't see the groundspeed.....

Ah, oh, ooooops!!!! Of course it's there, in the little window on the top right of the HSI (Horizontal Situation Indicator, the lower one of the two big central instruments).

Shanewhite , in a way, that illustrates that for flying the aircraft things like TAS and GS are not really that important... that's why there are no big instruments indicating TAS or GS, but only IAS and Mach, with only a little digital window for GS, which IS important for navigation (largely handled by the inertial navigation system, which is the system where the GS display comes from), but not for the minute-to-minute handling of the aircraft.

Bellerophon , dumb question from a techie... the 373 miles is presumably just the distance to the next INS waypoint?

CJ

I was Googling to see if I could find some info on how the CG indicator on Concorde functioned and found the following two links. The first one is an AAIB report from 2003 regarding a minor fire aboard G-BOAC whilst in transatlantic cruise which resulted in misreadings and failure flags on fuel guages. The second one is from the PPrune archives also dated 2003.

The last two comments at the bottom of that old PPrune thread are interesting since as evidenced by this ongoing thread (as well as the others running in the tech forum), seven years later, many many people are still fascinated by this gorgeous aircraft.

http://www.aaib.gov.uk/cms_resources...pdf_029047.pdf

http://www.pprune.org/archive/index.php/t-109948.html

Nick Thomas


... on shorter charter flights was there a mininium ammount of fuel that had to be loaded just to always have enough fuel for CofG movement...

Yes, 35,000 kgs, at take-off, for a short supersonic flight. This would allow sufficient fuel to be transferred rearwards in order to achieve a CG approaching 59%.

If the flight was to remain subsonic, the fuel figure dropped to 25,000 kgs, as the required CG for subsonic cruise was 55% not 59%.

Both these figures were at take-off, so the estimated taxy fuel had to be added to these figures in order to arrive at the minimum fuel figure required to be loaded.


...was it possible to be in a position where trip fuel, fuel to an alternate etc was less than the fuel required for CofG movement after take off?...

No, at least it should not have been!

However, a situation was sometimes reached in flight, generally only towards the end of the planned supercruise portion of a LHR-BGI sector, where, with the aircraft at M2.00 and FL600, it was no longer possible to maintain a CG of 59%, as the "ballast" fuel, which had been transferred aft into tank 11, was now required forward again as "fuel" fuel, to top up other tanks which had reached their minimum permitted levels.

In this case, once the forward transfer of fuel had begun, the CG would also be slowly moving FWD, and one would be compelled to commence the decel and descent earlier than desired, something EXWOK touched on here much earlier in this thread.

Best Regards

Bellerophon

I believe a "Near Zero Fuel" landing was successful....by a certain Chief Pilot

There were several appropriate cartoons at the time.

http://www.pprune.org/where-they-now...n-walpole.html

jodeliste ,
That question already ended up in a separate TechLog thread... LOL.

Concorde engine intake "Thrust"

Have a look there first, then if things still aren't quite clear, feel free to ask more questions!

CJ

Not surprisingly there are other threads on here about Concorde, found this stunning picture on page 4 post #76:

http://www.pprune.org/aviation-histo...ircraft-4.html


H wie

Hi Guys, quite a few little points here, so here's my angle(s):
Pedalz
Ooo yes. The biggest problems we ever had associated with the ramps themselves were wear in the seals at the sides of the forward ramp. Even a few thou' over the maximum allowable side gap was enough to make the intake unstable and susceptible to surging. (It is quite interesting that the rear ramp side gaps were not in the least bit critical, and if Concorde intake development had continued, the rear ramps were going to be deleted altogether). Other failure factors were control unit malfuntions, rapid sensor drift; all of these causing either ramp/spill door drift or runaway. Primary nozzle misbehaviour could also result in intake surges. Having said all that, the monitoring of the intake system was truly superb, and surface runaways, themselves quite rare, would usually be picked up by the control system monitors causing either a lane switch or if that did not work, a total 'red light' failure with the surfaces frozen. No surge was treated as 'just one of those things', and much midnight oil was burned and hair pulled out (so that's what happened to mine ) to try and find the cause of the surge.
My friend EXWOK perfectly answered the intake hydraulics allocations.
EXWOK was right on the ball here as usual, in fact above Mach 1.6 an interactive surge was more or less guaranteed. The cause of interactive surge had nothing to do with the wing leading edge position, but to the radially generated distortion field coming out of the FRONT of the surging intake, severely distorting the adjascent intakes airflow. It mattered not if the originating surge was an inboard or an outboard intake, the other guy would always go also, above Mach 1.6.
You might want to take a look at 'When Intakes Go Wrong Part 1:
http://www.pprune.org/tech-log/42690...-thrust-5.html
and Parts 2 & 3:
http://www.pprune.org/tech-log/42690...-thrust-5.html
Not to mention Part 3:


dixi188
I can never recall this particular event happening with BA , certainly not as a result of a ramp failure. Although in the near 28 years of operation we had quite a few SNN diversions, none that I can ever recall were as the result of a ramp structural failure. The two major SNN diversions that I can recall were G-BOAF in the early 80s when an LP1 blade failed and resulted in a totally wrecked engine (although a completely contained failure) and G-BOAA in 1991, with another wrecked engine due to running in rotating stall. (Both of these events were covered previously in our thread). ChristiaanJ has mentioned quite rightly the event with A/C 001 spitting a ramp out, and Air France had a ramp failure going into JFK. (Covered previously in our thread, due to certain 'human foul ups'). I am not sure, but I think that this one in JFK DID require a double engine change in JFK. (Usually from SNN a BA aircraft would be 3 engine ferried back to LHR).

ChristiaanJ
Nope, you are quite right, no more French or British development aircraft ever suffered a ramp linkage failure again. The 001 ramp failure was a salutary lesson to the design team, and the intake assembly became tougher than old boots after that, nomatter WHAT you threw at it.


Due to the lateness of the hour (and me being up at 4 ), that will have to do for now guys.

Best regards to all
Dude

In case anybody is interested, I just started off a separate thread
Concorde Books .
Probably too late for Christmas, but maybe useful just the same.

CJ

As with any aircraft the 71 was subject to any number of limitations, but airframe temperature was not one of them. The crew had no info on skin temp in any event. However compressor inlet temperature was the major limiting item (427\xb0C).

Thread on the Concorde inlets here http://www.pprune.org/tech-log/42690...ke-thrust.html

ChristiaanJ
Not quite right I'm afraid here my friend. The superb Vulcan used self-contained electro-hydraulic PFCUs, similar in concept to the VC10. The pilot signalling from the fighter type joystick to the PFCUs however was still mechanical, no FBW here.

EXWOK
Oh Amen to that. Although quite complex in its concept, at least 'our' system was logical and intuitive, with full pilot control throughout.

Best Regards
Dude

Christian, is this the video you are refering to? YouTube - PHY NYC Concorde breaks sound barrier (double bang)

Post #879 http://www.pprune.org/tech-log/42398...ml#post6129540 - Just guessing now, but Bellerophon were you a Concorde Pilot by any chance.

I read your vivid description and realised that I must have been peeling onions at the same time. Thank you for that sensational work of art, drawing us a picture of that take off while at the same time making it sound like it was no harder than taking a breath, though I have no doubts this was an extremely complex and demanding proceedure that required a level of crew synergy unknown of at that time. Again, my THANKS for that precious insight into your world.

This in no way excludes all the other contributors to one of the two best threads on this Forum. All you guys made and were part of a very special piece of history and now like the famous "Few" will never be forgotten partly as a result of this thread.

I do hope Landlady posts back with pieces that didn't make it into her book.

A picture is worth a thousand words they say, but the bathtub joints can't be the fairings showing just outboard of the nacelles as they (the bathtub joints) are flush

CliveL

Christian asked if there was an aerodynamicist in the house - I guess that would be me!

The original question was whether there was any vortex activity in subsonic cruise, but the discussion went on to ask about designing for subsonic drag I think.

The answer to the first bit is that the vortex flow started in a gentle manner from about 6 or 7 deg AoA and got steadily stronger. Depending on the chosen cruise speed and the aircraft weight, the subsonic cruise AoA would have been in the region of 4.5 to 5 degrees, i.e. below any significant vortex development. 6/7 deg would correspond to something in the range 250 to 280 kts probably (I haven't done the sums)

What we were trying to do for subsonic cruise was to have what is known in the trade as 'leading edge suction' acting on a nice bit of forward facing area so that it tried to drag the aircraft forwards as it were. As you can see from the diagram the prototype aircraft had a much more cambered LE so that both suction and forward facing area were very reasonable. This prototype shape was nicely rounded so that LE separation and top surface vortex generation started at a higher AoA than on the production aircraft. Unfortunately this shape, which featured a rather sharp LE on the undersurface, generated a vortex on the undersurface of the wing in supersonic flight and low AoA (near zero 'g'). This vortex got into the intake and caused the engine to surge, so we had to redesign the LE ahead of the intakes as shown. This cost us a little subsonic drag, so you can see from the diagram what you need to do to keep subsonic cruise drag down.

Hope this answers the questions

CliveL

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Dammit! I thought I had read that [xxxxquote] gave me one of those pretty text boxes ah well, back to the drawing board.....

Unfortunately the only flow visualisation pictures I have are taken at AoAs where the tip vortex has been swallowed by the main vortex, but I thought I would paste them anyway as most people would never have seen them. In this one you can see the forebody vortices quite clearly (the bluegreen streaks) but since it is a zero sideslip case they don't go anywhere near the fin.

On closer inspection, maybe you can just see the wingtip vortices as separate bits of curly white smoke very close to each wingtip.

I'm not going to risk losing all that typing trying to attach a second picture, so I will send that separately

CliveL

OK, here is another one .....

CliveL

Have a look here :
Flight envelope
Those are the official certified limits.
I doubt somehow anybody went beyond those "for the press".....
But during certification, yes, each of those limits was exceeded, slowly and carefully, to be able to draw those official operational limits on the document.
For instance, the certified Mmo is 2.04. During certification, G-BBDG (202) went to Mach 2.21....

Even while staying within the limits, she could could exceed Mach 1 just below 30,000 ft.

Also, during the acceptance flights after major overhauls, most of those envelope limits would be exceeded by a given margin, to prove the aircraft still met all the certification requirements. Whether any of that was done 'closer to the deck', I wouldn't know.

The 'issues' would vary. Performance would be one issue... Delta Golf (and 01, who went to Mach 2.23) basically "ran out of steam" at that speed.
Another issue would be that 'going beyond the borders' shortened the fatigue life of the airframe, and it was difficult to assess exactly by how much. It was one of the reasons why Delta Golf and Sierra Bravo (the certification aircraft) in the end never went into service.

CJ

OK Vortex Lift for Dummies!

Lets start with a comparison of the lft on a conventional subsonic wing with that of a slender wing like Concorde:



The subsonic line is linear, the slope depends on the geometry of the wing; high aspect ratio wings have a higher slope than low aspect ratio, unswept wings a higher slope than swept. Concorde, being a low aspect ratio swept wing has no chance!

To get a decent approach speed with a delta wing which has 'conventional' wing sections you need either a long U/C and work with high landing AoA or a large wing area to get the wing loading down. I would put the Avro Vulcan in the latter class. A large wing area is bad news for supersonic aircraft, but the Germans, working during WW2 found that if you give the delta sharp leading edges the flow separates at the leading edge and forms a pair of vortices that flow over the upper wing surface.

A vortex, if you could see it, is like a tornado (twister) turned on its side. The essential feature is that it is associated with low static pressures. As you get closer to the centre of the vortex the pressure drops more and more. The red zones at the centre of that transverse view are very low pressure indeed, but even the outer zones have quite low pressure.

I will have to put it up as a separate posting, but there are pictures that show that as AoA increases not only does the vortex get stronger (more suction) but the area of the wing affected by the vortex also inceases. This 'double whammy' gives the vortex a nonlinear effect. This 'nonlinear' lift is what is sometimes called 'vortex lift'.

It doesn't come for nothing - since by definition the flow is separated from the leading edge there is no alleviating 'leading edge suction' to reduce drag, and you won't go very far wrong if you take the drag of an aircraft with such a wing as Profile Drag plus Lift (times) tan AoA.

Concorde is a bit more subtle - the nose of the wing is drooped so that the flow does not separate until the AoA reaches 6 or 7 deg, giving us a good L/D in subsonic cruise whilst still having a healthy lift at approach speed.

Does this fit the bill?

CliveL

May I echo a plea that ChristiaanJ has already posted on this thread, and respectfully suggest that we try and keep this thread free from opinions and debate about the Gonesse accident and the subsequent withdrawal of Concorde from commercial service?

Most contributors to this thread will doubtless have strongly held opinions and views on both these topics. Some have posted comments here, but whilst I respect their views and their knowledge, are not these topics already more than adequately catered for on other threads and forums? Frankly, I have to confess that I have grown weary with most such threads, and, in general, neither read them nor contribute to them.

I do, however, greatly value having just one Concorde thread devoted purely to technical comments, anecdotes and personal reminiscences. Perhaps, if others feel similarly, we might try and keep this thread that way?

Happy New Year

Bellerophon

I think it is 002 - 101 had a take-off performance camera 'target' painted on the fuselage between wing and cockpit and it looks to me as if the intake doesn't have the cut-back leading edge. In addition, the front of the intake was 'black' on 002 but white on 101 as in roll-out photo below.





And of course a happy 2011 to all!

CliveL