Posts about: "MEPU (Monogol Emergency Power Unit)" [Posts: 14 Pages: 1]

Hi Stilton, that is a question that we all used to ask ourselves; not having an APU was a major pain in the butt for the fleet, particularly at charter destinations, where air start trucks, GPU's and air conditioning trucks would all have to be pre-arranged.
One problem with 'Conc' was always one of weight, (for every extra pound you carried, another pound of fuel was required) so any APU installation would have to have been light, and worth the extra weight. But the main problem was one of 'where to put the darned thing. The only suitable space available for an APU was in the tailcone, aft of the tail wheel. Now a ready supply of fuel would have been available either from the aft trim tank, #11, or from one of the two trim galleries. (For stability reasons, tank 11 was invariably left empty during ground transits). The real crunch however, was how to arrange pneumatic services from an APU: Tank 11 was directly forward of the tailcone, so this would have meant either ducting the pneumatics THROUGH the fuel tank (not a particularly good idea ) or externally around the fuselage, which would have been 'draggy' to say the least.
You could still have had an APU powering hydraulics, and in essence electrics too (the emergency generator was powered from the Green System), but without pneumatics for engine starting and air conditioning, it would really have been a waste of weight. Still, it really is a shame that there was no APU.
Historically, there were 'sort of' aux power units fitted to development aircraft: The prototypes had two GTS's (Gas Turbine Starters), one in each nacelle pair, that could start the engines without an air start truck, but these never saw the light of day in later aircraft. The most unusual unit of all was the MEPU (Monogol Emergency Power Unit), located in the tail cone. This was manufactured by Sundstrand, and was fitted to all of the development aircraft. (A derivation of a unit fitted to the X-15!!). The idea was that if you had a four-engined flameout at Mach 2, this thing would fire up, power Green and Yellow hydraulics (plus the emergency generator, again from the Green system), and give you power and control down to a safe relight altitude. The MEPU was powered by Hydrazine rocket fuel (unbelievably unstable) and I seem to remember that the thing would run for about 8 minutes. There was no way that this monstrosity would ever be acceptable on a commercial aircraft, and so a conventional RAT was developed by Dowty for the production aircraft. (Also, the windmilling engines would give you full electrics down to Mach 1.1, and Hydraulics down to about Mach 0.7, so the thing had little practical use when supersonic anyway).
I hope this extended blurb helps answer your query Stilton.

It would be, yes!
I can try asking around, but can't remember my original source - it probably came up during a discussion of the MEPU on Delta Golf or on 01 several years ago. I very much doubt it would be mentioned explicitly in the SRM (Structural Repair Manual).
IIRC the MEPU lived in the tail (I'll look it up), so it's not impossible the APU was planned in the same location.

Just looked up the MEPU in the 01 AFM, and indeed it's located in the tail cone. I'll scan the page this evening.
In the meantime, here's the MEPU exhaust in the tailcone of Delta Golf, courtesy of Neil Walker.



CJ

Hi Christiaan, yes THAT was the MEPU (Good photo of G-BBDG by the way). As far as fitting an APU in the tail cone, I still personally think that UNLESS you are prepared to pass a sizable pneumatic duct through a fuel tank , (Remember that tank 11 occupied the entire rear fuselage between the rear cargo aft wall and the front of the tail cone). then I don't think that this was really on. (It's quite possible of course that I'm missing something here, it comes with age ).
As far as the MEPU goes, all it really did was drive 2 hydraulic pumps; the Green System then powering the 40 KVA emergency generator; unless you are going to use the APU for engine starting and ground air conditioning, then I honestly don't think that there would be much point. It's interesting also to note that the MPU, being a rocket motor, needed no air intake, and as it was not driving any huge loads, the exhaust duct dould be quite narrow.

M2dude,

Nice set of photos of "The Thing" here :
MEPU at MAE at le Bourget .
This one is at the Air and Space Museum at Le Bourget, near Paris. My guess is that is was a spare, since the manufacturing date is 1973. 'SA flew in January '73 and 'SB in December '73.
IIRC, Delta Golf arrived at Brooklands with the MEPU still in place; I might have a photo.

As to the installation, we're obviously thinking along the same lines....

However, there were already several conduits through tank 11, such as hydraulics for the tail wheel, various electrics, and the 'backbone' fuel manifolds, that ended at the fuel jettison port in the tailcone.
A couple of fairly substantial air ducts would only have displaced a few hundred kgs of fuel at the most, out of the more than 10,000 kgs in tank 11.

And yes, of course, the whole point of the APU would be to have independent ground start and ground airco available, so clearly an APU would have been bigger and heavier than the MEPU (which was only just over 80 lbs), plus the problem of the air intake and bigger exhaust.
I'd have to get the drawings out to see how easy or difficult it would have been to fit one in the available space.

Since the tailcone was BAC, and both 214 and 216 were built at Filton, I wonder if anybody there still remembers?

ChristiaanJ
Thanks for the MEPU link, that really brings back memories (or was that nightmares ). I remember at Fairford, a small drop of Hydrazine leaked onto the hangar floor; the next thing you heard was a really loud crack, and a after the smoke cleared, there was a sizable hole in the floor.
I'd still really like to know what the 'thoughts' on this APU issue actually were. Although as you rightly point out tank 11 already had a fair amount of 'plumbing' running through it, we are talking here about a duct with sufficient size that can provide enough mass flow to turn over an Olympus engine to at least between 10 and 20% N2. You are looking at an least 10" diameter duct, not including the copious amounts of thermal insulation surrounding it, as well as an extremely sensitive overtemperature protection system. (This tank is going to be near empty, filled with fuel vapour). I'm not really convinced that this idea would even be considered by the CAA/DGAC/FAA etc. for safety reasons alone.
Still, it's food for thought though

M2dude,

Re the MEPU at the Le Bourget museum...
The story I just got was that it was taken off F-WTSA or F-WTSB at Roissy for a fault and replaced (both 'SA and 'SB operated out of Roissy around '74 / '75 for things like route proving, etc.).
It got left on a shelf in a store, and was only discovered again in 2003 during the "big clean-out" and was saved 'in extremis' by somebody who recognised it for what it was, stopped it from being 'binned' and took it over to the museum.

Initially of couse it was. It was not until the return to subsonic, towards the end of the flight, that the contents of the n\xb0 11 trim tank were moved forward again to the other tanks.
So yes, you're right, essentially all of it was "useable" fuel, it did not serve only for the trim.

Don't we all....
Jock Lowe seems to have stated there is a photo.... and we all still wonder if there is some footage taken from the Lear Jet during the filming of "Airport 79". But none is publicly known to exist ... we just know it's been done!

I think we already do agree about the story that Iran Air was going to have an APU, that Rotring had already been put to Mylar to sort out the how and where, and that some traces are likely to be left in 214 and 216.

So I happily agree to disagree on the rest... between the two of us, each looking at our own clues, and with the help of anybody else who has more info, we might still find the answer!

One thought I had... with an APU in the forward baggage hold, you'd also have to take the air intake and exhaust through the pressure hull, and provide sound and thermal insulation for the entire APU itself.
From a design point of view, I'd have gone for the same location of the earlier pseudo-APU (the MEPU), and then solved the remaining problems from that starting point.

That's post #1 that started this thread.
The subject was dealt with in some depth, and in the course of the discussion is was described how the two preproduction and the first two production aircraft were equipped with an MEPU (monopropellant emergency power generator).

I've only just found this photo again... it's the MEPU of Delta Golf (202 - G-BBDG).
The photo was taken after 'DG was moved to the Brooklands museum, but before the tail cone was put back into place.





CJ

The blue area at the front is the MEPU firewall. My main memories of the MEPU on Concorde (Apart from the fact that it was always breaking down)was the awful STINK of the Hydrazine insode the tailcone. (Made your eyes water). Good photo though.

Dude

Let's not stop!

Did I understand correctly? This space where the MEPU used to be installed is empty space on production aircraft?

Since DG had a MEPU, that means other production aircraft could have one installed?

Were the charter flights much different from the scheduled ones?

I've seen the 1999 Around the World video, and they took some engineers aboard (They should've taken M2Dude with them, LOL). Did they make the flight-planning on each stop or everything came from the mothership @ London?

BlueConcorde
As far as the MEPU went, yes there was just mainly empty space inside the tailcone, Aside from the tail wheel assembly there was just the power supply for the tail beacon as well as the fuel vent and jettison pipes. (On the forward bulkhead there were pumps and valves for tank 11). Having this great empty void did create problems in the early days of airline operation; there were some internal structural failures inside the tailcone (a low stressed area, so it was never serious). These failures were quickly attributed to acoustic fatigue inside the tailcone, due to resonance with engine and aerodynamic noise. This never occurred during any of the development flying; the prototypes and aircraft 1010 had a far smaller tailcone anyway, and aircraft 102, 201 and 202 had the bulk of the MEPU assembly complete with Hydrazine tank to fill up most of the void. The fix to the cracking problems was both very simple and quick to implement, and it never became a big deal. The MEPU, as has been mentioned a few times previous, was both useless and unsafe as far as a commercial aircraft goes; being replaced by a ram air turbine.
It's funny, but this is how this wonderful thread started over one month ago by stilton , I for one am so glad that it has both progressed and diversified the way that it has.
As far as charters go I'll leave it up to EXWOK or one of the other guys to answer, as far as flight planning goes. Thanks for your comments BlueConcorde, they always took a ground engineer on RTW charters, and although I never had the pleasure of directly participating in one (although I was on the end of a phone several times when problems occurred en-route)I WAS due to go in 2000, but tragic events in Paris caused that charter to be cancelled. I was however lucky enough to participate in various other charters, my most memorable one was in October 1991, when the World Bank chartered Concorde to Bangkok. The most amazing thing about RTW charters (or earth orbiters, as I would call them) was that the aircraft often returned to London with only a very small handfull of minor defects. The thing about Concorde was the more that she flew, the happier she was, and less likely to catch a cold.

PS. oops, EXWOK is already 'there'

Dude

She was a a test airframe only, although in circa 1985/86 we did look at modifications that would bring her up to production aircraft standard. The modifications required to the powerplant alone (mainly engine and intake control logic and management) were truly massive, as well as other things like engine instrumentation and other systems' control management. The total cripler however was the cost of a TOTAL RESKIN of the forward fuselage section (Component 30, made at Brooklands). The production series aircraft had a thicker skin here, and we were told that the CAA insisted on this being done as part of any conversion to airliner standard. Costs of around \xa330 were being banded about for bringing the entire airframe up to production aircraft standard. Also of course she had an MEPU when flying rather than a HYRAT for emergency power and of course a large flight test observers position.
I worked on 202 personally quite a bit during the mid to late 70's, but she never remotely 'felt' like a real production aircraft. Even aircraft 204 (G-BOAC) in her pre-route proving days was a radically different beast. (The OAC post route-proving modifications although at system level were quite extensive, these were miniscule in comparison to the differences between 202 and what we like to call 'the REAL Concorde'. Don't get me wrong, 202 did some absolutely stirring work in terms of route-proving and certification trials, and the restoration done at Brooklands is most impressive indeed, but she is and always was, nothing other than a test aircraft. She was no more a production airframe in reality than the pre-production aircraft 102, and I'm afraid that anyone thinking that she is anying other than this is truly deluding themselves my friend.
I'm sorry if this reality is dissapointing steve-de-s, but if you want to see a Concorde that is truly representative of what the aircraft was really all about I suggest that you pop up to either Manchester or East Fortune. (The only airliner museums in the UK now open to public viewing). The Manchester exhibit in particular is truly superb and beautifully kept by some great people, and shows you exactly what Concorde, THE AIRLINER was actually like, rather than just seeing a test specimin. (A superb specimin 202 indeed she was, but this is ALL she ever was, a test specimin).

Best regards
Dude

agreed Dude...

202 was built as 2nd Production, with a defined role as a test aircraft. Several studies were carried out over the years to see if she could be reused. Initially with the manufacturers, where if Concorde has been a success she could have been refurbished and sold to another airline at a "good" price. Of course here flying outside the certified flight envelope led to a lot of further concerns that really was curtains for any modification.

BA had robbed a lot of parts from her in the 80s, especially to bring G-BOAG back into service, so it was a no brainier in the end to put her in a hangar and rob whatever was required to kept the fleet of 7 in the air.

One little point, in the very late 70s here MEPU was decommissioned and she was fitted with the HYRAT...although the guts of the de-contaminated MEPU is still up in her tail cone.

If you want to see an Concorde as it was in Airline Service go visit MAN or EF, fantastic displays showing an Airline Concorde in the 90s or 00s

If you want to visit a Concorde and want to see the 4 stories in one (Concorde story, the unique story of a development aircraft, the airliner passenger experience and they story of how Concorde pilots were trained).... then visit Brooklands.

We've never been able to prove from a documented drawing perspective at Brooklands that the roof of the forward fuselage was any thiner than that of 204.