Posts about: "Afterburner/Re-heat" [Posts: 110 Pages: 6]

Something that I'm wondering about.

The reheat thrust increase is only about 6,000 lb per engine, so why is the fuel flow increase so large for a less than 20% thrust increase? Proportionally I think I remember it being mentioned that the fuel flow about doubles.

Feathers, these are the joys of afterburning; a totally gas guzzling way of extracting some more thrust from an engine. With Concorde, at 15 degrees TAT, you got a 78% increase in take off fuel flow for, as you say, about a 6000lb increase in thrust. Normaly adding an afterburning/reheat system is a fairly complex and heavy affair; you need both the system itself plus a variable exhaust nozzle. Because Concorde already required the primary nozzle for N1 control, the addition of reheat was at least a relatively simple and lightweight afair. The original Olympus 593-22R engine was really a little lacking in terms of dry thrust, and the addition of the reheat system was deemed essential. Concorde only had a single reheat spray ring and flame-holder, military systems often have several, with a corresponding increase in thrust growth as well as a hyper increase in fuel burn.
Further development plans for the Olypus 593 included a large increase in dry thrust; the reheat being retained only for transonic acceleration. It is such a pity that it was not to be.

Dude

From what I know (mostly quoting fromTrubshaw's book), things would have been even better than that.

Reheat on the existing aircraft supplied about 25% extra "wet" thrust.

The Olympus 593 "B" engine was going to have about 25% more "dry" thrust, so the reheat could most likely have been deleted altogether.
This was achieved mostly by increasing the diameter of the LP compressor, hence increasing the mass flow, and adding a second LP turbine stage.

The "B" engine was destined for the "B" Concorde which, thanks to several aerodynamic improvements, would have had increased performance and more range, allowing direct flights from Frankfurt and Rome to New York.

Concorde #17 would have been the "prototype" for the "B" model... sadly, as M2dude says, it was not to be.

CJ

DavvaP
There was one small part of the 'B' model that did find it's way into the production aircraft by way of a retro-fit in the late '70's.: The leading edge of the dorsal fin was re-profiled, taking out the original 'dog leg' and the flying control surfaces were slightly extended. The whole exercise was one of supersonic drag reduction, although I never saw the actual gains quantified. (It was due to the extensions of the elevons and rudders that water ingress caused failures in later years. I just hope the fuel, if any, we saved was worth the trouble ).
As far as ChristiaanJ's point about the Olympus; the only plans I ever saw were for the Olympus 593 Mk 622, which gave a thrust increase of around 4,000 lbs static thrust but retained reheat. I know there were definate plans for a larger diameter engine (not just the LPC) that would have naturally required a larger intake. As far as the intake irself went, believe it or not, the plan was to remove the rear ramp altogether.
The 'B' would have been a hell of an aeroplane; but the 'A' was still absolutely amazing in any case.

Dude

1) How many Concorde airframes were built?

22 total. 2 test, 9 BA, 9 AF, 2 spares (1 BA, 1 AF).

2) As far as the British constructed aircraft went, name the destinations that were served?. Regular flight numbers only, excludes charters etc.

JFK, Dulles Intl., Barbados, Miami, Bahrain, Singapore.

3) What was the departure time for the ORIGINAL morning LHR-JFK Concorde services? (Not called the BA001 then either).

No idea.

4) Further to question 3 above, what WERE the original flight numbers for the BA001 and BA003? (The morning and evening LHR-JFK services?).

No idea.


13 tanks, 2 main pumps each (except tank 11 which had 4 pumps) = 28
Main and aux engine feed pumps (3 per collector, 4 collectors for a total of 12)
Fuel pumps from aux tanks to mains = 4
Fuel dump = 2


BAC 221. Flying test bed for the wing design.






Filton.


27 L/R, 09 R.

Each engine had associated with it a set of lights , Blue, Amber, and Green

BLUE reverse light --- this reflected the correct operation of the
reverse thrust.

Flashing, rev selected but buckets in transit
On steady reverse selected and achieved

Amber Configuration
[CON] light----------- ON if reheat fails with no loss of engine RPM
On if reverse selected and primary nozzle greater
than 15%

Green Go light---------- This light monitored the engine for correct power
for take-off in that

Fuel flow and P7 had to match or exceed a pre
calculated figures, which were preset on their
individual gauges prior to take off.

The secondary nozzles had to within their
take-off limits

The CON light is off

In the case of No 4 engine the N1 limiter has
returned to normal position

Now normally there was a call of 100kts and at that point there had to be 4 green GO lights illuminated otherwise the t/off would be aborted. There was a concession to this in that if runway/ conditions /weight allowed the takeoff could continue with only 3 green lights illuminated at 100 kts as long as the
affected basic engine was OK[ this covered the loss of one reheat]

The green lights were considered necessary if the aircraft was using a rough runway and nose nodding could interfer with correct engine instruement monitoring and were also handy as the pilots could at a glance check whether they had at least minimum eng power for t/off.

To keep things simply their use was standard on all T/offs rough or otherwise

OK guys, here are the answers. If you disagree about any of them then fire away, the old memory certainly 'aint perfect.
As many of you have guessed, there were 22: The 14 production airframes, the 2 production series development aircraft (201 & 202), the 2 pre-production airframes (101 & 102) and the 2 prototypes 001 & 002. PLUS, the major fatigue test specimen at the RAE Farnborough and the static test specimen at CEAT in Toulouse. The CEAT tests actually tested the wing to destruction; I seem to remember it was something like a 200% overload before the wing failed at the root. And great but rather sad pictures VOLUME , never seen these before.
OK, from MY memory , we have: London LHR (duhhh!!), Bahrein BAH, Singapore SIN, New York JFK, Washington IAD, Dallas DFW, Miami MIA, Toronto YYZ, Barbados BGI, and Riyadh RUH. As well as charters being ommited, so are some of the special 'surprise' shuttle appearances that Concorde would make, substituting a subsonic to and from destinations such as Manchester and Edinburgh.
11:15
The BA193 and BA 195.
OK, there were 12 engine feed pumps (3 per engine) 8 main transfer tank pumps (2 each for the transfer tanks 5, 6, 7 & 8), 4 'A' tank pumps (2 each for 5A & 7A), 8 trim-transfer tank pumps (2 electric pumps each for tanks 9, 10 & 11 PLUS 2 hydraulically driven pumps for tank 9), 4 electric engine start pumps (there was a single electric start pump per engine that delivered fuel to it's own dedicated start atomiser in the combustion chamber. The pump automatically ran when the engine HP valve was set to OPEN and would continue running for 30 seconds after the DEBOW switch was returned to the 'normal' position), 4 engine first stage pumps (a single mechanically driven pump per engine), 4 second stage pumps (a single pneumatically driven pump, sometimes termed 'the turbopump, per engine. This would cut out at around 20,000'), our scavenge tank pump (triggered automatically when there was 7 US gallons in the tank; pumping it back into tank 2. This pump was identical to an 'A' tank transfer pump), and FINALLY, a single de-air pump for tank 10. The pump would drive the fuel through a mesh, removing air bubbles from the fuel. Tank 11 used the L/H trim pump for de-air (similar principle)and would be switched on during take-off. This is why the tank 5 trim inlet valve being set to over-ride OPEN would result in the tank being highly pressurised in the case of the Gonesse disaster; the pump would obviously pressurise the L/H trim gallery and any tank on that side with an open inlet valve!!!
G-AXDN, aircraft 101. (A production wing, fuselage, droop nose and intakes, but with the short tail section and secondary nozzles of the prototypes.
Ready ChristiaanJ? There were 18....Yes, the single SFENA standby horizon, 9 INS gyros (one per X,Y and Z platform in each of the 3 INUs), 8 autostab' rate gyros (one per axis for each of the 2 autostab' computers PLUS a monitor gyro for the pitch axis). The radar by the way used attitude signals from the INS.
9. One per main wheel plus the single 'in flight braking' nose wheel brake.
Mach 0.7!!! Between this and Mach 1.26 the intake surfaces were positioned as a function of engine N1 if the engine was shut down for any reason. (Otherwise of course the intake surfaces were fully up). You needed a sub idle N1 of 57% and below for all this to happen, and it was to assist relight performance and reduce buffet. Between Mach 1.26 and 1.32 the ramps were driven down slightly to about 5%, full supersonic scheduling itself commencing at Mach 1.32.
Already brilliantly answered by Brit312 (as well as the FSLabs diagram). Yep, Geen GO, T/O monitor armed, fuel flow and P7 at or above datum, A/C on ground, reverse not selected and CON light not on. Amber CON (Reheat selected and not detected, N1 OK or reverse selected and primary nozzle (Aj) not at minimum. Blue REV; steady buckets at reverse, flashing buckets in transit.
Fairford, followed by Brize Norton, and then a host of airfields from Prestwick and Shannon to Chateauroux.
OK, probably no surprises now:
Landing - 27L & R, 9L & R (prior to LHR mag' deviation update were 28L & R & 10L & R) together with 23/05.
Take off - 27L (28L), 9R (10R) and 9L. (10L never happened as take offs on this runway only occurred in 2003).
It was FedEx, they planned to operate two stripped out aircraft, leased from BA, between Shannon and JFK as high value parcel carriers. The idea was that parcels would be flown in from all over Europe by small FedEx feeder aircraft and the parcels transferred to Concorde which would then speed on to JFK in around 2 1/2 hours. It never happened because of a combination of economics appraisal by FedEx and BA deciding that it could would not release the aircraft anyway.
A/C 101, G-AXDN first flew on 17th December 1971 with FIXED INTAKES!! (101 was going to be the launch vehicle for the new digital intake control system, but the 'boxes' were still being designed). This placed an operating limit of Mach 1.5 on the aircraft, limiting her ability with such a restricted flight envelope. She returned to Filton in late 1972 for installation of the system, as well as the new Olympus 593-602 engine. (The engine, very similar to the production Mk 610 version, used a quite revolutionary annular combustion chamber, and eliminated at a stroke the thick smoke exhaust that had up to then been Concorde's unwanted visual signiture). The aircraft flew more or less smokeless on 15 March 1973, achieving Mach 2 soon afterwards. As ChristiaanJ pointed out, the British prototype 002 had a similar gap, actually significantly higher, of 19 months. (The French aircraft 001 had an even longer gap of some 20 months).

I hope you guys had fun with this one, regards to all

Dude

Hey Dude

Saw your posts about the Concorde reheat spray bar and flame holder assembly in another thread, might it be worth reposting it in this thread to keep it all in the same place?

On a related note, what changed in the engine parameters if the Contingency mode was entered on take-off? And what would trigger that mode?

Oh yes, and once engaged, is there a time limit on how long it can be maintained? I'm assuming in an engine out case that at heavy weight the reheats have to remain engaged on the remaining engines until the speed has built up to get off the back of the drag curve.

Consider it done Feathers.
As promised, here are a few diagrams of the Concorde reheat (afterburner, for our American friends) system. The ORIGINAL design was done by SNECMA, but due to them getting into all sorts of trouble with the fuel injection system and flame stabilisation, Rolls Royce baled them out, and it became a Rolls Royce/SNECMA design. (The core engine was a 100% Rolls design, with no French input whatsoever. However some engine sub-assembles were manufactured by SNECMA).
The basic way the afterburner worked was by spraying the fuel FORWARDS intially at high pressure, against the jet stram about one inch, until it hit the anvil. . As the fuel strikes the anvil it is blown back by the jet stram and atomises, passing over the of the spray ring and the over the flame holder. The ignition operated by passing 15KV across a dual cylindrical tube, the resulting arc was 'swirlied' into the fuel stream by blowing engine 5th stage HP compressor air into the tube (there were 7 stages in all).
The key to successful ignition was a healthy spark, a good supply of air to the ignitor and accurate scheduling of fuel flow. (This was scheduled against dry engine flow as a funtion of total temperature). The other important factor (as with any afterburner) was correct and rapid operation of the exhaust nozzle. Fortunately, Concorde used it's primary nozzle for control of engine N1 anyway, so adapting this to operate as an afterburning nozzle also was a relative walk in the park, and it operated superbly.
During the light up phase of 3.5 seconds, the fuel ratio is a fixed 0.45 (ie. reheat fuel is 45% of dry fuel). After the light up phase the full scheduling commenced. As far as the FLIGHT RATING figures go (not take-off) the ratios were 0.6 at a TAT of 54 deg's C, falling linearly to 0.3 at 107 deg's C and above. (Remember that Concorde used afterburning really sparingly, just for take-off and then transonic acceleration; cut off at Mach 1.7 altogether.

Dude

Feathers McGraw
Contingency mode could be either manually or automatically selected during take-off. It would automatically be selected if an engine dropped below 58% N2, PROVIDED that the take-off monitor button was set, and reheat was selected. (A small yellow CTY light on the centre dash panel would flash in this case also). OR it could be manually selected by moving the 4 reheat selector switches through a clever little gate, from RHT to CTY. In this case, the yellow CTY light would illuminate steadily.
Actually at entry into service, contingency had a real problem, in that when selected the reheat flame would burn very fiercely, become unstable and extinguish altogether. (So instead of getting more power, you ended up with less; with just the increase in dry thrust, and no reheat at all ). It seems that the reheat flame holder was too small to support the bigger contingency flame, which effectively would just fall over. What we had to do in the early days of service was to isolate the wire that provided the contingency discreet to the reheat amplifier, ensuring that the reheat would hopefully still operate normally when contingency was invoked, so at least you got a small increase in power from the dry engine. The solution was the welding of 7 small 'fingers' to the outer part of the reheat flame holder, this made the flame holder 'appear' bigger than it really was to the flame. It worked perfectly, and we could therefore re-connect our wire again. (Just making the flame holder physically bigger would have had a detrimental impact on the operation of the dry engine).

Dude

I understand that you could continue the takeoff if one reheat failed to light, but two questions. if you will:

• Typically, would the balky reheat light on the next event requiring additional thrust, the transonic acceleration?

• In the event it did not relight for the transonic climb, what was the impact on range with only three afterburners available for acceleration?

TC

I'll leave it to M2dude to answer this fully and properly..
But... yes and no....
Whether you could actually continue the take-off, if one reheat didn't light, depended on several factors, such as t/o weight, runway length, ambient temperature, and suchlike. This was all calculated before take-off, and there was a little tab on the forward panel (I'll have to find a photo), which you would flip to either "3" or "4" as an instant reminder.
If the little tab said "4" and you got only three reheats coming on, you didn't have to think or go through a checklist... you rejected the takeoff.
M2dude probably can quote the speed.... but it was still well below V1, so such a RTO was not nearly as spectacular as a really nasty one around V1.

CJ

100kts

E/O calls "Power set" if you have a minimum of 4 engines and 3 reheats (for a "goer" - your flippy thing set to "3"!) else "Engine Fail" and therefore an RTO. 4-engines and 4-reheats (4 greens) needed at 100kts for a "power set" call for a "stopper" - flippy thing at "4". It was simply how far off TOW was from PLTOW and a concept introduced following a commercially unacceptable number of RTOs which weren't necessary from a perf-A POV...

(A single reheat failure, although rare, could be accepted after 100kts at any weight)

(Just noticed Brit312 covered this earlier - sorry!)

Thanks Dude, very interesting!

As for the 7 fingered reheat flame-holder, do you know of or have any photos? I'm quite fascinated by this, I'd like to see what it looks like. I have never heard of this modification anywhere else so once again this thread manages to surprise by turning up things that one couldn't find out any other way.

Thanks Dude.

Not quite what I was expecting but very interesting all the same. I see that each finger appears to have an inlet at the base to allow gas flow to alleviate some of the turbulence behind it.

Now to find a picture of a Concorde reheat flame rosette to see how the flame matches up to the finger pattern.

Good game!

Better still, I found a picture of the reheat assembly with the fingers fitted:

Google Image Result for http://heritageconcorde.com/wp-content/uploads/2010/03/reheat-picture.jpg

Very good photo Feathers. The reheat really was just about the most fragile part of the powerplant, and gave us numerous headaches throughout the service life of the aircraft. The most unreliable part of all was the ignition side of things; the ignition transformer itself being the main culprit here. Also the swirl ignitor itself was rather fragile, as the smallest blockage in the air supply would render the ignitor useless. The failure of the reheat system resulted in the majority of rejected take-offs in the service life of the aircraft. (Failures during transonic acceleration would sometimes respond to a second selection of reheat, but this was often due to spontaneous llight up, due to the much higher total temperatures at Mach 0.95, rather than a recovery of the ignition system itself).

Dude

Did you need all 4 reheats to go from 0.95 - 1.7 ?

If you got to 1.3 and then one or more failed could you continue (albeit with slower acceleration ?)

I presume if you were unable to get the things lit at 0.95 you just turned round and went home again ? The procedure would take around 90 mins so would you need to burn off fuel or already be at acceptable landing weight by that time ?


Also, once when aboard at about 50K-55K feet the aircraft rolled I would estimate 3 degrees to the left and then came back level again almost immediately. I knew this was a glitch but no one else noticed. An announcement was made of a minor problem about 2 mins later and that was that ?

What might have cause such an event (I would guess an airflow issue with intake or engine ?)

norodnik

...Did you need all 4 reheats to go from 0.95 - 1.7 ?...

No.

Two reheats were the minimum for transonic acceleration, however due regard would have to paid to the additional fuel usage with one or two reheats failed.


...If you got to 1.3 and then one or more failed could you continue (albeit with slower acceleration ?)...

Yes, as above, whilst remembering the 15 minute time limit on the use of reheat.


...I presume if you were unable to get the things lit at 0.95 you just turned round and went home again ?...

Yes, once you were convinced that at least three were not going to light up.


...The procedure would take around 90 mins so would you need to burn off fuel or already be at acceptable landing weight by that time ?...

Not something I ever had to do, fortunately, but even so, 90 minutes would seem somewhat excessive to me, given that the aircraft would still have been over the Bristol channel. On a transatlantic sector, fuel jettisoning would have been necessary to get down to 130,000 kgs (for a fuel saving landing) or 111,130 kgs (MLW) if the nature of the failure precluded a fuel saving landing.


...once when aboard at about 50K-55K feet the aircraft rolled I would estimate 3 degrees to the left and then came back level again almost immediately...what might have cause such an event (I would guess an airflow issue with intake or engine ?)...

Any number of things could have caused this, but probably the most likely one is the one you suspected, a (transient) intake problem.


Best Regards

Bellerophon

hahaha Mike, sorry about that, yes I DID meen $100 MILLION.
norodnik
I can not personally recall a triple reheat fail ever happening, as Bellerophon explained in his answer to your post, but I can recall one occasion several years ago where the 15 minute time limit was inadvertantly exceeded for a couple of minutes. This was reported to both Rolls Royce and SNECMA, but no checks etc were instigated. The reheat ignition system, as I posted previously, was far too fragile; we did some investigations with Rolls Royce about 15 years ago into using 'hot streak' injection as a backup ignition source, but this was ruled out on cost grounds.

Dude

jodelistie
First of all Rod, welcome to our Concorde thread, and thank you very much for your kind words.
Now as far as the rumour goes, I'm afraid that it is nonsense, however the truth is an even more complex story of collusion, betrayal and intrigue. You may read that 'Concorde was retired by BA and Air France purely due to economic reasons', however that is not quite the case (and as far as THIS side of the English Puddle goes, is total poppycock!!). Now BA lost a huge amount of her regular traffic as a result of the 9/11 tragedy and also as a result of the 2003 Iraq war, but things were improving nicely. In her 27 years of operation, Concorde had survived countless dips in her traffic, only to return stronger as market conditions improved.
It is early 2003, and French Concorde traffic to the USA has almost vanished, down to single digit loads. This is due mainly to total French opposition the impending US/UK invasion of Iraq, and US businessmen using BA Concorde almost exclusively. (French business seems to be boycotting the US altogether, so their contribution to passenger loads virtually ceased). Due to the apalling loads, AF are losing absolutely MILLIONS of Euros, at a time when the carrier is trying to privatise itself ... but there is more:
In the same February, AF very nearly lost ANOTHER Concorde, yet again largely down to total incompetence and lack of adherence to established procedures. Aircraft F-BTSD was flying between CDG and JFK when there was a failure of the reheat delivery pipe that runs from the engine 1st stage fuel pump to the reheat shut-off valve. This failure, although not particularly serious, led to a chain of events that very nearly resulted in the loss of the aircraft, and all those onboard. (Air France engines were overhauled seperately to BA, who never experienced this particular failure). What was required in the case of this failure was a precautionary engine shut-down, closing off the fuel supply to the engine totally, and a descent/deceleration to subsonic speed, carefully monitoring fuel consumption all the time. Unfortunately the crew 'forgot' to shut down the fuel LP valve, and this resulted in the fuel continuing to gush out of the failed pipe at an alarming rate. (Oh, and also they forgot to monitor the fuel consumption). Only after the crew FINALLY noticed that they were still losing fuel did they remember to close the engine LP valve, but it was almost too late. The aircraft just managed to land in Halifax, with barely enough fuel left in the tanks to taxi!! So, herer we are, AF are horrified that they have come very close to yet another disaster, knowing full well that yet again human error was a major factor.
But there is more....
One week later another AF aircraft loses part of a rudder panel due to de-lamination of the honeycomb surface, not particularly serious in itself, but it put even more jitters up the trousers of AF. (Rudder failures had happened to BA aircraft many years previous to this, but BA had purchased brand new and improved rudders from Airbus UK in Filton, but Air France chose not too).
So it seems that the chairmen of both Air France and Airbus (who regards Concorde as a waste of its valuable resources) have a 'secret' meeting to plan what was effectively the murder of Concorde. There is no way that AF want BA to carry on flying Concorde while they have to cease operations, so the plan is for Airbus to make a huge hike in their product support costs; these costs would have to be borne by BA exclusively, which they both knew would not be possible. If these support costs were not met, there would be no manufacturers support, and without this there would be no type certificate, and without this, no more Concorde.
Their (AF & Airbus) hope was that BA would not challenge this move legally, and sadly for the world of aviation they did not. At a meeting, BA AND AIR FRANCE!!!! were told by Airbus about the hike in product support costs, and BA would also have to cease operations. BA were not even allowed to continue until March 2004 (the Barbados season was nearly fully booked already), and so would have to cease operations in October 2003.
But the British were far from blameless in all this; a now retired very senior British airline person had always obsessively HATED Concorde, so the French conspiracy was a very early Christmas present for him; he finally got what he had always wanted. The 'end of Concorde' anouncement by both airlines was made in April 2003; AF had got what their executives wanted and finished flying in May, reluctantly leaving BA to fly until late October. If you want a full (and extremely well informed) explanation of what happened in that whole debacle, the article by Don Pevsner is worth reading. It can be found at this website:
THE BETRAYAL OF CONCORDE
There is absolutely no doubt in my mind that without the truly disgusting events in France in early 2003, Concorde would still be proudly flying for BA. (And with modifications and enhancements would fly safely for many more years).
quote** "in the hands of true professionals, Concorde was the safest aircraft that ever flew. and in the hands of BA crews at least, she was always just that..*

Oh and yes you were correct, the Olympus (the world's first ever 2 spool engine) was originally a 'Bristol-Siddeley' design, before BS were absorbed into Rolls-Royce. Stanley Hookers book is in my view totally superb, a true classic.

Dude