Concorde depressurization procedure
 

Curious to know what drills were followed with a rapid depressurization at it's normal cruising levels between FL500-600.



Was it possible to go to idle power prior to starting a descent, and with no spoilers would reverse have been used to achieve a higher rate ?

Just happened to look in, and saw this thread was active again.

No trouble getting down from the CRZ:

Idle power would be used (the ramps should cope with the change of airflow). Idle power at M2 resulted in a most impressive rate of deceleration (anyone standing in the aisle would probably find themselves sitting), which translated into a very high RoD. Well over 10 000fpm initially.

As such, reverse would be neither needed nor desirable; you would be well outside the envelope of idle reverse use anyway. (This function was quite rarely used as it was a bit of a faff).

The pilots would select the fuel fwd transfer override switch initially to cope with the decel, and the FE would set the fuel panel up shortly after the descent was steady.

All very dramatic, and never needed in pax service afaik.

Thanks Exwk, is it accurate that FL600 was the Concorde's regulated ceiling due to the time required to descend in the event of a depressurization or were there other factors involved ?


It sounds like you could get down pretty quickly when needed. I believe it was capable of higher altitudes and sometimes reached FL600 in cruise, I forget the highest achieved during flight test although that is probably in this thread !


Incidentally what was the envelope for using reverse ? Your description of it's operation makes it sound less than practical ?


Why was that ?


Best wishes.

Time for descent may well have been a certification requirement for max FL - others will know better than I…

I don't believe the ramp schedules were designed to operate far above FL600, I vaguely recall that FL635 was the highest reached during testing but, again, others will know better. A typical LHR-JFK or JFK-LHR would get to between 570 and 590 depending on weight and OAT, LHR-BGI almost invariably ended up level at FL600 due to lower weight and much lower outside temps.

As for reverse inflight, off the top of my head the limits were; Max FL300, speed 250-380kts, max use 4 mins. It didn't make a vast difference to RoD, although it was noticeable.

Inflight rvs was limited to engs 2 and 3 but to enable sufficient air to deploy the reversers, engs 1 and 4 spooled up slightly (in fwd thrust) to help deployment. While this is going on the primary nozzles open fully (for the same reason) but after reverse position is reached, the 2 and 3 primary nozzles have to close to 15% otherwise you get a 'CON' light which means reverse has to be cancelled on that engine (this was not a rare event).

Common sense and airmanship also dictated that you had an escape plan if one or both the engines didn't get the secondary nozzles out of reverse, so you didn't want to do this if fuel was tight.

All-in-all it was far better to make sure you didn't need reverse inflight!

EXWOK:
Did they have to pump the fuel forward? Or did it just move on its own due to the decel?

……it was pumped.

Tank 11 also had two hydraulically-powered fuel transfer pumps to cater for other failures which may deprive you of elex power to the usual pumps, just to cover all eventualities.

Did LHR-BGI always tech stop in SNN ?

Nope. Don't remember ever doing that.

Occasionally tech stopped ANU or SMA if tight for fuel.

Phew! What a fantastic read.
 

After about a week of 3-hour nights (not much on the telly) I have finally got to the end of this thread. Let me echo others in praising the patience and technical openness of the main engineering contributors, along with the excellent recollections of the pilots, cabin staff and many others.

I am afraid I have only been on Concorde around a dozen times, and as I live a few miles from Duxford, you'll probably guess that's 101 now in Hangar 1. Standing in the cabin I can only imagine the experience of actually flying in her, but you guys have certainly bought her back to life in my mind at least.

While reading the thread I came up with many questions (around ten or so) and these have been answered in later exchanges on the thread, however I do have a few left over:

1. The speed freak in me always wants to know "how fast"? Notwithstanding the principles outlined on p.55 by CliveL and M2Dude, if the intake system were somehow made "more leaky" and reheat were applied, in theory at least, how much more thrust could the 4 engines produce, in "ideal" conditions (I saw somewhere that -80C had been encountered)? If you then extrapolate the drag, what sort of peak Mach number might be attainable in short bursts (ignoring for now the detrimental effect on the airframe?)

2. There was a discussion or two of the (highly theoretical, expensive and unlikely) prospect of restoring one of the airframes back to flight around p22. However I don't think I saw 101 or 102 mentioned in any of these discussions, are these even further 'gone' (101 having sat outside for 20 years)? On the other hand, would the lack of sponge-like insulation mean less corrosion might have set in?

3. Again on p.55 there is mention of (naff) paint schemes and their bad effect on skin temperature. Was the paint on Concorde specifically chosen to radiate infrared (for example) to help cooling? The SR-71 (which I also visit at Duxford regularly - how lucky am I!) of course is matt black, which presumably radiates even better? When the airframe attained thermal equilibrium at the top of the cruise, what were the relative contributions to cooling of: radiation, cold uncompressed air passing over parts of the skin, the internal aircon (cooling from the inside), etc?

4. M2Dude referred a couple of times to robbing spares from other airframes. Spares that may have been 5-8 years old? What sort of testing regime must these spare parts go through to ensure they are still fit for flight? Is it labour-intensive?


If I can opine (at the risk of having M2Dude chastise me if he still reads this - as I am not staff) the computer he mentioned on page 37 sounds to me very much like a "bit slice" computer. These were typically constructed from discrete logic and quite often had very long words - 64 or 128 bits. I only ever saw one of these in my 30-year career in computing, a rare beast indeed. And yes I remember that Mil Spec TTL - back in the day I used to pop the lid off the ceramic packages and you can look at the gates, and even watch the silicon glow if you apply a bit too much Vcc! But I digress.

Thanks again for a fascinating thread.

@EXWOK


There was a certification requirement for descent time from FL600 down to FL100 if I recall correctly. Can't remember the value though. In flight reverse was developed to trim some fraction of a minute off the time to get inside the requirement


@ a_q

Not sure what you mean by a "leaky" intake. At about 2.2M the first shock would hit the intake lower lip and from that point on the total intake mass flow was frozen. Increased engine mass flow could only be obtained by reducing bleed flow and that gave higher engine face flow distortions driving the engine towards surge and lower intake recovery. So engine mass flow was effectively fixed also.
Then the amount of "dry" fuel which could be added was limited because the higher Mach number increased the engine entry temperature but the maximum turbine entry temperature was fixed.
You could add thrust by using reheat, but you would not get as much as you would like because the final nozzle, being designed for 2.0M would be too small for optimum efficiency at higher Mach numbers.
Overall, IIRC we got to 2.23M in flight test. If you pushed me I would say it might be possible with reheat etc to get to 2.25 or 2.26M, but it would be a blind guess!

Did Concorde have Autobrakes or manual? What was typical stopping distance and did reverse play a big part once it was back on the ground?

Leaky?
 

Thanks CliveL,

as you said on P.55 a fair few moons ago:

Your engineering "finger in the air" seems quite reasonable, so that answers one question, thanks.

I have a new project, on my next visit to Duxford to find out if the front wheel brake disk is the vented style, or solid. For on one of my cars I have Cortina solid front disks, and on another the vented ones, and I'd like to know which one has a "Concorde" front brake :) Do I have to look in between the front wheels?

This thread is absolutely amazing and blimey me if I wouldn't buy it as a book!

Leaky
 

@a-q


Ah yes, page 55 from 4 years ago ...... It's my age you know!


What threw me was your reference to a leaky intake - on 101 it was all the nacelle aft of the intake that leaked not the intake itself

Ruddman -

No autobrakes.

(And - with my pedant's hat on - no 'manual' brakes either. Pedal brakes, yes. I know that the 'manual brakes' has become an accepted term, but the nonsense of it just bugs me….)

Stopping distances were good; from a higher Vapp we stopped rather shorter than a 'classic' 747. Filton was tightish, Bournemouth was worse….

First gen carbon brakes did not like being 'feathered' so we used them pretty firmly on every landing. At Filton, Bournemouth, E Midlands etc. you'd put the pedals to the floor after nose wheel touchdown. Allegedly no more wear doing this than feathering them along a long runway.

Reverse was pretty effective - more so than a modern bypass engine. We idled the outboards at 100kts and the inboards at 75kts so they weren't in play for the whole landing (reverse is most effective at higher speeds anyway).

It was a good 'stopper'. Thankfully.

Was pilot selection purely on seniority?

Great information Exwk.


Didn't the early prototypes have a braking parachute ?

@stilton


Yes they did. I tried to post a photograph but the Dropbox link doesn't seem to work any more (neither does the "quote" icon)

EXWOK?
 

Much appreciated. :ok:

May I assist........

http://i16.photobucket.com/albums/b9...psir7n35aw.jpg