Malcolm Hood Inst'l AAF in ETO

[drgondog]

RAF Warton became the primary Base Air Depot (2) for B-24 and P-51. Each Fighter Group in the 8th and 9th Air Force had an on base Service Squadron/Group capable of implementing tech orders and significant repairs.

I have heard that the Malcolm Hood required between 85 and 135 hours to install and I am unclear where the primary installation took place.. conceivably it could have also been modified at BAD1 Burtonwood which had responsibility for B-17 and P-47... BAD2 Warton or each local Service Group - I suspect tooling required so I suspect centralized process in which the Mustang was flown to a specific location, modified and returned to the combat unit. Ditto the first 250+ 85 gallon fuselage tanks for the P-51B-1, -5-NA and P-51C-1NT that arrived without them.


Can anyone shed light on this subject? BTW, according to The Mustang Story by Ken Delve (pg 35), the NAA engineers in UK in 1942 designed the Hood for the Mustang IA AG618 and Malcolm tweaked it for the blown hood and manufactured the canopies. The RAF modified very few Mustang I and IA but performed the modification on all Mustang III and IIIA at RAF Henley before inserting them into combat ops, whereas the 8th AF typically received their P-51B/C's with the birdcage canopy - then had them modified.

 

[bobbysocks]

i dont think any of the crew cheifs or maintence men i know are still around but i will check and see....and if they can remember.

 

[GregP]

I'll ask at the Planes of Fame next weekend.

Interesting subject as I would NOT think it would take that long, but I also haven't tried to do one, so I must be underestimating the work required.

 

[Edgar Brooks]

The Malcolm hood, for the Mustang, was not "blown." Known as "drape moulded," it was produced in Maidenhead/on White Waltham airfield, where a friend of mine worked many years ago.
While there, he got to know a former Malcolm employee, who told him that they would have a sheet of Perspex (in a frame,) which was heated until soft, then six of them would pull it down over a former, holding it until it cooled.
White Waltham was also the centre for the Air Transport Auxiliary, so there would have been a plentiful supply of pilots to fetch and deliver aircraft if necessary.

 

[kool kitty89]

I thought 'blown' referred less to the process for making the hood and more the final shape itself.

 

[Edgar Brooks]

The canopies for the Spitfire XVI, 22 24, plus Seafires 17, 46 47, were (literally) blown by air introduced from below, until the top hit a "stop" (or stops)which arrested the airflow, but allowed the air to remain (like a balloon) until the canopy cooled. Supermarine and Westland made their own blown canopies, but, due to manufacturing limitations, Westland's items were slightly smaller.
I've since found that the Malcolm canopy was supplied, as a kit of parts, for user units to fit themselves.

 

[drgondog]

Edgar - my terminology referred not to the process but the bulged shape as differentiated with flat sides. As to kits, the Kits were surely manufactured by Malcolm as far as the canopy, front latch and rails are concerned but the references I have for RAF stipulate RAF Henlow as the first stop from Speke(?) just for that Modification. Do you have a contra references?

Greg - all of my crew chief friends from Steeple Morden have passed. I can find zero reference however to any Service Group involvement at SM in any engineering report, nor can I find a before (birdcage) and after (Malcolm) that would indicate that a ship had been modified after arriving at the 355th.

 

[drgondog]

I'll ask at the Planes of Fame next weekend.

Interesting subject as I would NOT think it would take that long, but I also haven't tried to do one, so I must be underestimating the work required.

Greg - the man-hour source(s) conflict with each other but I also scratch my head as is seems that jig to position the canopy rail to drill and position the rail for riveting is the only part of the process that requires or suggests complications, and maybe the canopy latch mechanism... I think POF would be easily able to perform the mod.

You might take a look on the inside of the cockpit of the P-51A that you have there and maybe QP-B or one of the other 'Hood' P-51B's that come into POF.

 

[Edgar Brooks]

my terminology referred not to the process but the bulged shape as differentiated with flat sides.

And I used the terminology of the manufacturing company, to assist those who are reading this thread, and might get the wrong impression of how things were done at the time.

the references I have for RAF stipulate RAF Henley as the first stop from Speke(?) just for that Modification.

If you check a map, you'll see that Henley is just a few miles from Maidenhead, and, as well as building Spitfires, it was a relief landing ground for RAF White Waltham (on the outskirts of Maidenhead.)

 

[GregP]

Bill,

I can tell you this myself, having seen it many times.

We have a shop at Chino called Aerotraders. One of the owners is Carl Scholl. As it happens, making plexiglass canopies is a skill they could not seem to find, so they created their own canopy shop. Not surprisingly, warbird owners come to them on a regular basis.

The Planes of Fame has an F4U-1d Corsair that started life as an F4U-1, was "upgraded" to an F4U-1a, and then an F4U-1d. So it went from birdcage, to 3-panel blister canopy, to 1-piece blister canopy. We decided to bring the Corsair back to F4U-1a status and located the old 3-panel canopy frame in our stash. I prepped it and handed it over to the guys at Fighter Rebuilders. They are currently prepping it for installation and need canopy panels.

So, they went to Carl Scholl. His crew does the same as you describe above. They make a mold, put a big square of plexiglass into a frame that holds the outer edges, and heat it until it is soft. Then it is like a timed rodeo event. You have to pull the plexi out of the oven, remove the frame, place it over the mold, and ... with heavy gloves on ... bend it to shape over the mold. They have maybe 25 seconds to get all this done. If they don't, they start again.

Not surprisingly, they sometimes have to attempt one several times before they get a "good" canopy. Hence, the cost ... they ain't cheap. A new baby Corsair canopy will be about $10,000, but the world-wide supply is zero, so I suppose it isn't really all THAT expensive to a Corsair owner.

The real work comes in making the canopy fit the frame. So I can fully understand the labor you mention above if it includes fitting the new "blown" canopy. It isn't easy to find the holes, overdrill them to allow for expansion, and get them all correct and in place. The Plexi expands at an entirely different rate than the Aluminum canopy frame, so the holes have to be oversize.

Anyway, I'll ask, assuming anyone is around the weekend after airshow. They might all be taking the weekend off, but they will BE there sooner or later.

 

[pbehn]

Not surprisingly, they sometimes have to attempt one several times before they get a "good" canopy. Hence, the cost ... they ain't cheap. A new baby Corsair canopy will be about $10,000, but the world-wide supply is zero, so I suppose it isn't really all THAT expensive to a Corsair owner.

That maybe cheap, a windscreen for a car with a production run of 10 would probably be more which is why the modern super car costs balloon toward $1,000,000.

 

[drgondog]

Bill,

The real work comes in making the canopy fit the frame. So I can fully understand the labor you mention above if it includes fitting the new "blown" canopy. It isn't easy to find the holes, overdrill them to allow for expansion, and get them all correct and in place. The Plexi expands at an entirely different rate than the Aluminum canopy frame, so the holes have to be oversize.

Anyway, I'll ask, assuming anyone is around the weekend after airshow. They might all be taking the weekend off, but they will BE there sooner or later.

Thanks Greg - The WWII Malcolm had a contiguous bead front and back - but no frame. As retold to me (no claim on accuracy but came from a crew chief) they sometimes glued a leather strip on the front edge to develop a better seal against rain and high speed airflow.

 

[bobbysocks]

Bud Anderson is still alive. he had a B model (B6*S 324823 ) with a malcolm. i will try to contact him or his son Jim. i just checked out his site....He is still touring!

so if you are going to be near one of these places you might be able to ask him...

May 16, 2015 - Dedication/unveiling of Bud Anderson Statue at the Auburn Municipal Airport, CA

May 20, 2015 - American Fighter Aces Congressional Gold Medal Ceremony

American Fighter Aces Fly Into History â€" Once Again | Business Wire

June 19-21, 2015 - Ray Fagen Memorial Airshow, Granite Falls, MN

i am digging to see if his B had a birdcase before being fitted with the MH..or what the story was.

 

[tyrodtom]

Are you sure there's not a decimal left out in that time estimate ?

Like 8.5-13.5 man hours.

How many man hours to overhaul a Merlin ?

 

[tyrodtom]

edit

 

[bobbysocks]

digging into it i see where John England's G4*H 2106462 ( never noticed these long numbers at the beginning months ) U'Ve Had it had both a birdcage and a malcolm. and i am able to find at least 6 others that had bird cages swapped out for malcoms.

C5*0 2106923 Daddy's Pet
B6*Z 2106458 Doodle Bug
G4*E 36698 Texas Ranger
B6*H 36755 Kalamazoo Kid
B6*E 324842 Blackpool Bat
G4*D Miss Marvel

 

[bobbysocks]

i do know it took 400 man hours for a full wing ( both because bent ) swap....

 

[GregP]

You asked how many hours to overhaul a Merlin. I don't know the British numbers but I have the numbers for the U.S.A. for last half of 1943 through Aug 1945.

For the last half of 1943 the Merlin averaged 464 hours for an overhaul.
For all of 1944 the Merlin averaged 287 hours for an overhaul.
For 1945 through August the merlin averaged 259 hours for an overhaul.

For the entire period the average for an overhaul was 320 hours with a high of 592 and a low of 190 for a month period.

The overall war average for the Allison V-1710 was 191 with a high of 376 and a low of 117.

I suppose the extra fasteners on the Merlin account for a lot of it. The Allison has about 7,000 parts and the Merlin has about 11,000 (very close numbers in both cases). A large number of the "extra" parts in a Merlin are bolts/screws, washers, and nuts. It takes a much longer time to get a major piece off a Merlin than it does an Allison, but it is not more difficult, just more time-consuming due to the "extra" fasteners. Inside the two are remarkably alike.

The lowest overhaul time on average was the R-1340 at 105 hours average and the highest was the R-2800 at 329 hours average. So the Merlin was right near the top as far as overhaul man-hours expended.

Let's recall that the "TBO" didn't mean the engine was "worn out." It just meant that the USAAF decided to overhaul engines at that time point.

Today the average TBO for a civil Merlin in the U.S.A. is 600 hours or so. During the war it ranged from 150 - 350 hours, possibly 400 at the end. As they gained experience and the war went on, the TBO got longer. They started conservatively and then extended the TBO as they gained experience. Same process for all US engines and I imagine for all countries, though I am not positive of that statement as I don't have the data for other countries. But the premise makes very good sense.

Of course if everyone had good sense, we wouldn't have fought the war in the first place.

The data comes from Table 115 of the USAF Statistical Digest of WWII and is applicable for engine depots in the continental U.S.A.. In theaters outside the U.S.A., they probably sent MOST engines back home for overhaul. I don't have the numbers for field overhauls (most likely rings and valves ... top ends) in combat areas.

At the Planes of Fame we can change Merlin piston rings fairly quickly. For major work, we usually send them out. In the 9 years I have been there, there has been little "major work" and I have seen maybe 2 - 3 sets of new rings. While I was at Joe Yancey's shop we did the left Allison for our P-38 two years ago. The right was running fine and still is though it probably needs to be "freshened" sometime soon. We have a freshly overhauled V-1650-7 waiting to be swapped out in our P-51 "Spam Can." Now that the airshow is over, perhaps it will be soon.

 

[drgondog]

digging into it i see where John England's G4*H 2106462 ( never noticed these long numbers at the beginning months ) U'Ve Had it had both a birdcage and a malcolm. and i am able to find at least 6 others that had bird cages swapped out for malcoms.

C5*0 2106923 Daddy's Pet
B6*Z 2106458 Doodle Bug
G4*E 36698 Texas Ranger
B6*H 36755 Kalamazoo Kid
B6*E 324842 Blackpool Bat
G4*D Miss Marvel

That helps re-enforce that AAF more interested in immediate operational status over 'final condition' but doesn't help figuring out whether the base Service group or the Air Depot did the work..

Thanks for the extra data.

 

[bobbysocks]

we'll see if Bud or Jim anderson get back to me ( or here, i gave Jim the forum thread ) and if he knows or remembers anything.