cptkrell
Posts: 3186
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Concorde Subsonic Cruise

Tue Jun 10, 2003 11:08 pm

Since it's been announced that BA will keep one Concorde operational (and I'm assuming it will be for airshow and display purposes), would it be desirable to fly subsonic at lower flight levels to go long distance? I am thinking in terms of less stress on the aircraft to vist, say, Oshkosh in the future. Thanks...Jack
all best; jack
 
LHR340
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RE: Concorde Subsonic Cruise

Tue Jun 10, 2003 11:49 pm

No the aircraft is not designed for low level flying it would use up to much fuel - the delta wing is made for supersonic flight not subsonic it would cause to much drag on the a/c (I think).
And even at subsonic flight the engines are still LOUD so if the aircraft was to fly over land there would be a lot of complaints from the houses it will fly over.

I bet I am completely wrong  Smile/happy/getting dizzy

LHR340
A340 LoVeR! EC-GQK - LHR The Bussiest International Airport & 3rd Bussiest In The World!
 
bobrayner
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RE: Concorde Subsonic Cruise

Wed Jun 11, 2003 1:31 am

Personally, I would be very surprised if there were more drag - or noise - when subsonic.

Anybody with appropriate concorde experience who can enlighten us?  Smile
Cunning linguist
 
LHR340
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RE: Concorde Subsonic Cruise

Wed Jun 11, 2003 4:29 am

Bob - I hear concorde fly over everyday, when it is hot it echoes and rumbles around for ages, it would be enough to annoy anyone at subsonic alt. Concorde is designed for supersonic not subsonic!

LHR340
A340 LoVeR! EC-GQK - LHR The Bussiest International Airport & 3rd Bussiest In The World!
 
cptkrell
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RE: Concorde Subsonic Cruise

Wed Jun 11, 2003 4:40 am

I am questioning if it would be a benifit to the airframe to eliminate the supersonic flight cycles. Thanks...Jack
all best; jack
 
XXXX10
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RE: Concorde Subsonic Cruise

Wed Jun 11, 2003 6:08 am

I think you'll find that supersonic cruise actually helps the airframe.

The high skin temperatures eliminate almost all of the corrosion
 
B2707SST
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RE: Concorde Subsonic Cruise

Wed Jun 11, 2003 10:27 am

Concorde does actually consume more fuel per mile when flying subsonically. As LHR340 pointed out, the delta wing is suited to supersonic cruise. Due to the thin wing's low aspect ratio and camber, subsonic flight requires a higher angle of attack than a subsonic airliner, creating more drag (although total drag at Mach 2 is much higher than at Mach .95). Initial cruising altitude is somewhat low (around FL290) to keep the AOA down.

The Olympus turbojet engines are the main problem, however. They are designed for Mach 2 flight and take full advantage of the precompression of the air stream created by the intake system, which dramatically increases efficiency and offsets the higher drag during supersonic cruise. Just as the 707-120's turbojet engines weren't as efficient as the -320's turbofans, Concorde's engines are at a disadvantage at subsonic speeds. When all is said and done, Concorde's range is reduced substantially when flying subsonically. I can't find the exact figure, but about 3,200 miles comes to mind. Even the swing-wing Boeing SST, which was (on paper) quite a bit more efficient than Concorde in subsonic flight, suffered a subsonic range penalty due to its turbojet engines.

--B2707SST
Keynes is dead and we are living in his long run.
 
ConcordeBoy
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RE: Concorde Subsonic Cruise

Wed Jun 11, 2003 11:12 am

I am questioning if it would be a benifit to the airframe to eliminate the supersonic flight cycles.

Absolutely not!

As XXXX10 already stated, Concorde's supersonic abilities is one of the reasons it's been able to live on so relatively healthily despite the temporal age of its airframe
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!
 
jetdoctor
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RE: Concorde Subsonic Cruise

Wed Jun 11, 2003 1:26 pm

Slightly off the topic of the Concorde airframe, but I have been away from aviation for a week.

Jack, where did you hear that BA is keeping an operational Concorde. Just curious.....


Jetdoctor
Break ground, and head into the wind. Don't break wind and head into the ground.
 
cptkrell
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RE: Concorde Subsonic Cruise

Thu Jun 12, 2003 1:28 am

Dear JetDoctor: The topic, "British Airways: We Will Keep 1 Concorde Flying", started 2003-06-07, is in the Civil Aviation Forum and uses the London Times as a source. I assume (maybe incorrectly) that the information is valid.

Dear Others: I'm suspicious that my question has been misunderstood as a veiled suggestion that perhaps Concorde could remain in pax service if not flown supersonic. This is not at all the point of the question. I am of the old warbird mentality where we typically operate vintage airplanes below their performance capabilities when flying extended distances between airshow venues. I was questioning if it would be desirable to do the same with Concorde on an occassional transatlantic flight (I had Oshkosh in mind, once a year). The cost in time, refueling, etc. would obviously be excessive, but I'm not talking about normal revenue producing operations, I'm talking about "saving" the airplane.

Now, the "no" answers directly addressing my question leads, then, to another: if it is so important to fly Concorde supersonic, would future flights to airshows in Europe be occassionally supplimented with supersonic operation off-coast to "maintain" the airplane?

I thank all of you for your input and apologise if this topic has become a bit tiresome for some of you. Kind regards...Jack
all best; jack
 
Leezyjet
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RE: Concorde Subsonic Cruise

Thu Jun 12, 2003 6:09 am

I see alot of the armchair experts are replying to this, you might be better off looking at this website for the info you require, or contact GDB or Bellerophon.

http://www.concordesst.com

 Smile

"She Rolls, 45 knots, 90, 135, nose comes up to 20 degrees, she's airborne - She flies, Concorde Flies"
 
Bellerophon
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RE: Concorde Subsonic Cruise

Mon Jun 16, 2003 2:04 am

Cptkrell

... would it be desirable to fly subsonic at lower flight levels to go long distance...

Not from a fuel economy point of view. Concorde’s subsonic range will be roughly about 25% less than her supersonic range.

The most fuel efficient way to operate Concorde is this:

Fly as fast as you can, as quickly as you can, for as long as you can.

To illustrate this point, consider the following fuel flow figures. They are all based on a Concorde at the same weight, in ISA temperatures, flying at the optimum Mach number for her altitude and at the optimum altitude for the number of operating engines.

4e...FL520...M2.00...1,134 kts...5,783 kg/eng/hr...23,132 kg/hr...20 kg/nm

4e...FL290...M0.95......562 kts...3,576 kg/eng/hr...14,304 kg/hr...25 kg/nm

3e...FL270...M0.95......567 kts...5,560 kg/eng/hr...16,680 kg/hr...30 kg/nm

…I am questioning if it would be a benifit to the airframe to eliminate the supersonic flight cycles…

Not from an airframe stress point of view, although this is less clearly demonstrated. The prevailing engineering view is that the heat transmitted to the airframe in SuperCruise is beneficial because it dries out any moisture that may have collected in remote or inaccessible parts of the airframe, and has contributed greatly to the lack of internal corrosion to be found and the longevity of the airframe.

… I am of the old warbird mentality where we typically operate vintage airplanes below their performance capabilities…

You will be familiar then with the difficulties that can be encountered with the licensing authorities getting these aircraft back into the air, and with the extensive and expensive maintenance that can be required.

If Concorde were to continue to fly at airshows, as a vintage aircraft, then the UK CAA would have to be convinced that it was safe for her to do so, and a large part of this would involve close scrutiny of the proposed maintenance schedule.

This maintenance schedule could be simplified greatly if, as part of the certification process, it was accepted by all parties involved that Concorde would no longer fly supersonically.

Many systems necessary for supersonic flight could then be de-activated, greatly reducing the expense of routine maintenance. For instance, the following systems would no longer be required.

• Computer controlled engine intake ramps (only used above M1.3).

• Re-heats (there is a procedure for a no-reheat take off at light weights).

• Flight crew pressure breathing oxygen apparatus.

• Fuel Tank 11 (used as a trim tank at M2.0).

• Fuel tank pressurisation system (used to stop fuel evaporating above FL440).

• TMO protection (keeps the Nose Temperature below +127°C).

• Several flight modes within the autopilot system.

• Flight crew training/recency requirements reduced.

• A further speed restriction of M0.7 would mean that the entire fuel trim/transfer would not be required.

All of these are areas where a lot of time, effort and money could be saved.

Presumably the main objective would be to display Concorde at air shows, and at sea level her VMO is 300 kts, so why go to all the difficulty of getting her back to M2.0 where no-one can see her?

So, despite what I said earlier about fuel economy, my personal view is that the maintenance costs and licensing difficulties of maintaining a supersonic capability whilst in private ownership would be too great, and that if she ever does fly again, as a display aircraft, it will only be at subsonic speeds

I would, of course, be delighted to be proved wrong!

… I had Oshkosh in mind, once a year…

So did I. I was the next in line to take her there!

Best regards

Bellerophon

 
cptkrell
Posts: 3186
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RE: Concorde Subsonic Cruise

Wed Jun 18, 2003 8:35 am

Dear Bellerophon and others; kind thanks for all the valuable input. I'm sure we are all hoping for her continued operation in some capacity to preserve history. Perhaps my thoughts of an occassional revisit to the USA in the future may be realized. Regards...Jack
all best; jack
 
mirrodie
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RE: Concorde Subsonic Cruise

Wed Jun 18, 2003 10:27 am

dear all, thanks for a great thread. I learn so much here!

Forum moderator 2001-2010; He's a pedantic, pontificating, pretentious bastard, a belligerent old fart, a worthless st
 
GDB
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RE: Concorde Subsonic Cruise

Thu Jun 19, 2003 3:52 pm

Even if, as Bellerphon pointed out, costs and engineering effort were substantially reduced by limiting a preserved Concorde to M0.7, I have to say a lot of our guys are doubtful it could still happen.
But, rumour has it that Rod Eddington (who is really pushing this-no doubt he regrets and is angry about being forced to retire Concorde early), wants a fully functioning Concorde.
So another meeting with Airbus is due, they would have to be involved in any preservation effort, much more so if it was to stay supersonic.
On the other hand, a fully functioning Concorde could also be attractive to Quinteq (the new name for the Defence Research Agency), other European aeronautical agencies, Airbus and even NASA.
Look at all the effort Boeing had to go through to get a TU-144 flying.
It would be a shame to see Concorde's still unrivalled capability being lost, (I remember a few years ago some guys from the USAF F-15 units based in the UK visiting us, when we told them how long we could sustain Mach 2 for their jaws dropped).
Maybe once the A380 is in service, a match for the 7E7 is in the works, the A320 updated, Airbus will look at an SST, they'll need a research vehicle.
But it is early days yet, it will be hard enough keeping a subsonic Concorde flyable.
 
eg777er
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RE: Concorde Subsonic Cruise

Thu Jun 19, 2003 6:33 pm

Brian Trubshaw floats the idea of a Concorde supersonic engine-test vehicle in his book. IIRC, he mentions a speed of M2.2 with development in this role.

Come on Airbus, grab it and give us a new SST! Stuff the yankee doodles once again!! (Just kidding!  Big grin ).
 
GDB
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RE: Concorde Subsonic Cruise

Fri Jun 20, 2003 7:09 am

I typed too soon, BA have spoken to Airbus about keeping one flying for airshows etc, it's not going to happen.
After all, they'd have to provide much of the cash and manpower.

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