As a former Mechanical engineer this situation is something that is often glossed over, maintenance heavy equipment is a massive burden on your crews and the more they have to do it the more pissed off they get and the reliability suffers as a consequence. Having to constantly work, on a plane in this case causes resentment and the care factor starts to wane especially having to remove so many plugs so often resulting in the chances of damaging the threads likely meaning more work to fix it and more swearing and more resentment and moral suffers. Lastly looking at the fuel system, ammunition and supercharger layout the plane is ''full'' of things to be hit, all late war German and British aircraft had switched over to cannons and there's very few places on a Thunderbolt that a API/SAPI round can hit that won't cause a fire or explosion, the things a flying fuel tank surrounded by ammunition.
Sea fang vs Sea fury vs XP-72
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- #22
I just realized something
I don't think the U.S.A. was "much better" at developing weapons than anyone else. Our airplanes were good, at least the post-1942 versions were, but so were everyone else's. Anyone who says the Germans didn't develop good warplanes never got into a fight with one (or more) of them. British aircraft and pilots were renowned for having a go at anything flying. The actual airframe performance of the Spitfire (and others) was always outstanding. The Japanese pilots and airplanes were excellent, at least early-on in the war, before they lost a lot of veterans and failed to update their front-line equipment in greater numbers. The same can be said of most any air force that got to fight enough to learn aerial combat tactics and employ them correctly. The Soviet Union took a little longer just due to outdated aircraft at first and inability to let their pilots think for themselves. In the end, Soviet pilots and aircraft were right up there with anyone else.
We got a good one in the XP-72, but it came right when a better airplanes was not particularly needed as the war was winding down, so it never got adopted. Had it been adopted, it would have shown sparkling performance at the cost of heavy maintenance. Have you ever tried to change 56 spark plugs? Just getting an R-4360 started after it sits for a week or two is several hours of oily labor to drain the bottom cylinders. You'd likely have to remove 18 - 20 spark plugs from the bottom cylinders and turn it over by hand to clear the oil accumulation.
But, when it is running right, it CAN and DID give pretty decent performance. The numbers I showed above came from a quick online lookup of performance, not actual flight test reports. I don't think I've ever seen an actual flight test report on the XP-72. But, when we want to compare, we use the numbers we can find.
Do you have information that the numbers above are incorrect? If so, post it, by all means. I'd love to see flight test reports showing the performance seen during testing rather then reported in reference books with backup data cited but not shown.
The 5 blade XP-51G prototype is even faster than the XP-72.
How?. 
FLYBOYJ
"THE GREAT GAZOO"
It was lighter for starters.I just realized something
The 5 blade XP-51G prototype is even faster than the XP-72.
North American P-51 Mustang variants - Wikipedia
I just realized something
The 5 blade XP-51G prototype is even faster than the XP-72.
Low-drag airframe with an next-gen Merlin in the nose.
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- #25
The spiteful , sea fang and sea fury were also much lighter than XP-72
spiteful and seafang are pretty low drag as well
GregP
Major
Anything with a single Merlin or Griffon was lighter than anything with a single R-4360 in it!
Let's see:
Merlin 61, 2-stage: Dry weight: 1,640 lbs.; 1,580 hp.
Griffon 65, 2-stage: Dry weight: 1,980 lbs.; 2,035 hp (2,220 hp if 150-Grade fuel was used).
R-4360-51 VDT, 1-stage: Dry weight: 3,720 lbs.; 4,300 hp.
So, you get to choose what you want to fly. But ... the XP-72 had very competitive wing loading with any of the late-war piston fighters.
Let's see:
Merlin 61, 2-stage: Dry weight: 1,640 lbs.; 1,580 hp.
Griffon 65, 2-stage: Dry weight: 1,980 lbs.; 2,035 hp (2,220 hp if 150-Grade fuel was used).
R-4360-51 VDT, 1-stage: Dry weight: 3,720 lbs.; 4,300 hp.
So, you get to choose what you want to fly. But ... the XP-72 had very competitive wing loading with any of the late-war piston fighters.
wuzak
Captain
The R-4360 VDT never went into service.
GregP
Major
It's the engine with the easiest to find data, at least for me. Check Wiki.
The actual R-4360 in the XP-72 was more like 3,500hp, but the jump to 4,000+ hp took place VERY rapidly and the engine was in service in the B-29D rapidly, too.
The actual R-4360 in the XP-72 was more like 3,500hp, but the jump to 4,000+ hp took place VERY rapidly and the engine was in service in the B-29D rapidly, too.
Source for the bolded part?
wuzak
Captain
Variants[edit]
Pratt & Whitney R-4360 Wasp Major
- R-4360-4 - 2,650 hp (1,980 kW)
- R-4360-17 - 3,500 hp (2,600 kW) XB-35 and YB-35 outboard engines with 8-bladed contra-rotating propellers[5]
- R-4360-20 - 3,500 hp (2,600 kW)
- R-4360-21 - 3,500 hp (2,600 kW) XB-35 and YB-35 inboard engines with 8-bladed contra-rotating propellers[5]
- R-4360-25 - 3,000 hp (2,200 kW)
- R-4360-41 - 3,500 hp (2,600 kW)
- R-4360-45 - 3,500 hp (2,600 kW) YB-35 outboard engines with 4-bladed propellers[5]
- R-4360-47 - 3,500 hp (2,600 kW) YB-35 inboard engines with 4-bladed propellers[5]
- R-4360-51 VDT - "Variable Discharge Turbine" 4,300 hp (3,210 kW). Intended for B-36C. Used on Boeing YB-50C Superfortress. 2-Power recovery turbines.
- R-4360-53 - 3,800 hp (2,800 kW)
- R-4360-B3 - 3,500 hp (2,600 kW)
- R-4360-B6 - 3,500 hp (2,600 kW)
Only the VDT had over 4,000hp according to Wiki.
GregP
Major
The XB-44 flew in May 1945 with R-4360s of 3,000 hp or so. In Dec 1945, the B-44 name was changed to B-50 and orders went from 200 to 60. In 1947, the YB-50C was ordered with turbo-compound engines. It was under construction when it was decided to order the B-36 instead, but the engines were developed for it. That's pretty rapid for peacetime development ... what a year and a half or so NOT under wartime development schedules. I call that rapid.
Boeing built 370 aircraft in the B-50 series with 10 – 12 major improvements over the B-29 progressively being added, not the least of which were the R-4360s, none of which had the turbo-compounds in it.
The B-36 started with the 3,000 hp engines but progressed to the 3,800 hp, not 4,000 hp as I said above, units with the B-36F. This was about the 1950 - 51 timeframe. The delay from when the engines were developed to when they flew was the switch from the B-50C to the B-36, not the R-4360 turbo-compounds.
Boeing built 370 aircraft in the B-50 series with 10 – 12 major improvements over the B-29 progressively being added, not the least of which were the R-4360s, none of which had the turbo-compounds in it.
The B-36 started with the 3,000 hp engines but progressed to the 3,800 hp, not 4,000 hp as I said above, units with the B-36F. This was about the 1950 - 51 timeframe. The delay from when the engines were developed to when they flew was the switch from the B-50C to the B-36, not the R-4360 turbo-compounds.
FLYBOYJ
"THE GREAT GAZOO"
Actually the XB-44 led into the development of the B-29D. The B-29D received the B-50 designation so the program can be funded as a "new" bomber program. The rest is history.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The B-54 was intended to have the R-4360-51 VDT engines.
Clayton Magnet
Staff Sergeant
- 902
- Feb 16, 2013
Like W wuzak said, the XP-72 only ever existed as a couple of prototypes, so the high speed attained in the test machines would almost certainly have been lower if it had ever made it to production. I think the prototype Spiteful made close to 500mph as well, but the production aircraft did not, not that they made very many anyway.
The geneses of the Sea Fury was the "Fury", which first flew in 1944 as well, but took a back seat to more pressing matters. The British didn't have the same capacity to develop multiple expensive projects simultaneously, and during war-time, development projects often got abandoned to focus resources on existing types already in production.
I for one would love to see what could have been, if the Spitfire Mk.III had actually made it into service. Or Tempests without chin scoops
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Shortround6
Major General
Immm, what was unit cost of the Me-262???
GregP
Major
Me 262 was 6,400 man-hours in the only place I found it.
P-47 started off at 22,000 man-hours and fell to 9,600 man-hours by the end of the war.
I'd say the XP-72 was back up in the 20,000+ man-hour area because it was a prototype and not a production airframe, but I have never seen an actual man-hour number for it. Hand-built airplanes aren't quick to assemble.
P-47 started off at 22,000 man-hours and fell to 9,600 man-hours by the end of the war.
I'd say the XP-72 was back up in the 20,000+ man-hour area because it was a prototype and not a production airframe, but I have never seen an actual man-hour number for it. Hand-built airplanes aren't quick to assemble.
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Shortround6
Major General
Test speed of the P-72 could be either way.
The propeller had not been finalized yet. Not sure the supercharger system had been finalized yet either.
Not sure the armament had been truly determined either. That was a lot of airplane for less armament than a P-51.
The P-47N wasn't that much slower than than the P-72 considering the two extra guns, the under fuselage hard point and the rocket racks. Not to mention only using 18 cylinders instead of 28 cylinders.
wuzak
Captain
The VDT was tested in an airframe - as one of the 4 engines on a B-50, IIRC.
There was no suitable control system at the time, so the flight engineer had to control the exhaust nozzle manually.
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