Peter Gunn
Master Sergeant
Quite possibly, thanks, I'll look it up and try to snag a copy.
XP-39 II - The Groundhog Day Thread
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It is quite interesting that even though this A6M2 was pretty beat up and bent before repairs, it still had no aborts or malfunctions during the testing. The same could not be said about some of the US aircraft in the test report (IIS 85).
They were a bit lucky that this was a fairly new aircraft and had not seen much service before the crash.
Here is a list of the repairs that were done just so folks can get a feel for how "intact" the A6M2 actually was:
A 15 August 1942 memo from the Commanding Officer of the U.S. Naval Air Station, San Diego, to the Chief of the Bureau of Aeronautics, listed repairs that Zero 4593 needed to make it airworthy. The following is a text of that memo, start:
1. Subject airplane can be put into flying condition in six weeks, provided no unexpected trouble is encountered. It will be necessary to manufacture numerous replacement parts, particularly bolts, machine screws, etc., as they appear to be metric. Work has commenced and will be expedited by day and night shifts, seven days a week.
2. The engine appears to be in good general condition. The bottom front cylinder was dented, apparently by the bullet, which severed the forward sump oil line. The Station will straighten and re-hone this cylinder, and it is believed that it will be in satisfactory condition. The carburetor and possibly other engine accessories are in bad shape internally from corrosion, and will need considerable reconditioning. No undue difficulty in accomplishing this is anticipated.
Structural Repairs Necessary to Fuselage and Wings:
1. Rebuild fin.
2. Repair both elevators.
3. Repair rudder.
4. Rear section of fuselage out of line and bulkheads buckled necessitating considerable repair.
5. Repair fuselage belt frame at stations 9 and 11.
6. Replace top fuselage skin and stringers
7. Rebuild sliding cockpit enclosure
8. Repair seat
9. Straighten fuselage adjacent to cockpit both sides at stations 2-5.
10. Repair fuselage skin at station 4.
11. Repair fuselage at top forward of pilot at station 1.
12. Rebuilt entire engine cowling
13. Repair cowl flaps.
14. Rebuild both sides of landing gear (both main attaching fittings sheared off).
15. Rebuild left landing flap.
16. Replace all ribs on right landing flap.
17. Cut and splice main left wing beam at landing gear attachment.
18. Rebuild one wing tip.
19. Repair left bottom wing skin at station 2.
20. Repair bullet holes in left wing at station 0.
21. Repair leading edge skin on right wing at stations 1.4 and 2.
22. Remake gun cover in right wing between stations 2 and 2.25
23. Patch right wing leading edge skin at station 3.
24. Patch skin and splice main wing bulkhead at station 3.7.
25. Manufacture two aileron fittings which have been sawed off.
26. Replace pilot tube located on left wing.
27. Manufacture various nuts, bolts, etc. which are missing and patch various small holes in skin.
28. Check all wiring. It may be necessary to replace fifty percent of wiring in ship.
29. Test oil and gas tanks. Overhaul is probably necessary.
30. Re-rig all surfaces and other controls.
Necessary Engine Repairs:
1. Straighten and repair nine push rods.
2. Repair one cylinder.
3. Rewire and overhaul harness.
4. Replace two missing spark plugs with LS321 plugs.
5. Completely overhaul carburetor (badly corroded - all springs and some other parts to be replaced)
6. Recondition magnetos (badly corroded).
Instruments:
1. Overhaul all instruments, hydraulic units.
2. If necessary, replace instruments and other small units with Navy standard articles.
End.
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Shortround6
Major General
Two stage Allison -47 was running in the P-39E in April 1942. Problem was the extensively revised E model weighed 8900lbs. Had six .50cal MGs AND a 37mm cannon. And didn't have a 4 blade propeller.
Let's see.
Two stage Allison -47 was running in the P-39E in April 1942.
Yep, true, sort of, an Allison -47 was running in the P-39E in APril of 1942, but in what configuration?
There were 3+ Allison -47 built. over 4000 on order at one point but either canceled or changed to other versions.
The -47 was eventually turned into the -93.
The -47 was initially built with an auxiliary supercharger using the same diameter impeller as the engine supercharger and fixed speed (single) drive. This was while still on test bench.
The drive system was modified a number of times to finally get to the configuration used in the P-63, hydraulic coupling with variable speed.
The -47 was rated at 1150hp at 21,000ft at some point (not April of 1942, they had not finalized the drive system yet, they decided to use the automatic hydraulic coupling in July of 1942) engine weighed 1525lbs in Feb of 1942.
The developed -93 engine was designed in the fall of 1942, not fully prepared for model testing until May of 1943.
Yep, lets use a near vaporware engine.
Had six .50cal MGs AND a 37mm cannon
No, it didn't. That armament was proposed by Larry Bell in a letter to General Echols in the spring of 1942 when they were asking for funding for a 3rd XP-39E to be built after the first one crashed. He also proposed a low altitude version of the engine with 1500hp at 3000ft. to power this version which Larry Bell envisioned as an attack plane for use against invasion forces attacking the United States. WEP ratings had not been approved for US engines at this point.
Please find any photo or drawing of an XP-39E with any wing guns, even the .30 cal ones.
need for 4 bladed propeller to handle 1325hp for take-off and 1150hp at 21,000ft seems a little iffy. Need for a 4 blade propeller won't show up until some time in 1943.
Let's see.
Two stage Allison -47 was running in the P-39E in April 1942.
Yep, true, sort of, an Allison -47 was running in the P-39E in APril of 1942, but in what configuration?
There were 3+ Allison -47 built. over 4000 on order at one point but either canceled or changed to other versions.
The -47 was eventually turned into the -93.
The -47 was initially built with an auxiliary supercharger using the same diameter impeller as the engine supercharger and fixed speed (single) drive. This was while still on test bench.
The drive system was modified a number of times to finally get to the configuration used in the P-63, hydraulic coupling with variable speed.
The -47 was rated at 1150hp at 21,000ft at some point (not April of 1942, they had not finalized the drive system yet, they decided to use the automatic hydraulic coupling in July of 1942) engine weighed 1525lbs in Feb of 1942.
The developed -93 engine was designed in the fall of 1942, not fully prepared for model testing until May of 1943.
Yep, lets use a near vaporware engine.
Had six .50cal MGs AND a 37mm cannon
No, it didn't. That armament was proposed by Larry Bell in a letter to General Echols in the spring of 1942 when they were asking for funding for a 3rd XP-39E to be built after the first one crashed. He also proposed a low altitude version of the engine with 1500hp at 3000ft. to power this version which Larry Bell envisioned as an attack plane for use against invasion forces attacking the United States. WEP ratings had not been approved for US engines at this point.
Please find any photo or drawing of an XP-39E with any wing guns, even the .30 cal ones.
need for 4 bladed propeller to handle 1325hp for take-off and 1150hp at 21,000ft seems a little iffy. Need for a 4 blade propeller won't show up until some time in 1943.
Peter Gunn
Master Sergeant
Hi Ivan,
Excellent info, gives a whole new meaning to the words "almost intact" when reading the "to do" list. That it was rebuilt was a testament to both its initial design and high manufacturing standards but also the the Navy guys at the San Diego Naval Air Station. To fly after all that and not have any aborts or malfunctions really says something about the aircraft.
P.S. I snagged a copy of "Luftwaffe Test Pilot" off Amazon for twelve bucks, should be here next week. I'll be interested to see how good my memory is, I'll make any corrections to my post (if it matters) if I find I was wrong. Many thanks again.
Excellent info, gives a whole new meaning to the words "almost intact" when reading the "to do" list. That it was rebuilt was a testament to both its initial design and high manufacturing standards but also the the Navy guys at the San Diego Naval Air Station. To fly after all that and not have any aborts or malfunctions really says something about the aircraft.
P.S. I snagged a copy of "Luftwaffe Test Pilot" off Amazon for twelve bucks, should be here next week. I'll be interested to see how good my memory is, I'll make any corrections to my post (if it matters) if I find I was wrong. Many thanks again.
Peter Gunn
Master Sergeant
Ach... double post, see post #104, apologies.
I think George made a typo, omitting the words "two stage" ahead of supercharger.
Nope - the article is wrong.
Plus, there was a lot of aircraft that were effective way past 17000 ft despite having just 1 stage of supercharging.
P-39 Expert
Non-Expert
Did weigh 8900lbs though, right? Wonder how it would have performed in a regular P-39 at 7900lbs?
Needed the 4 blade prop for high altitude thin air.
-93 was in production in April 1943.
Was the same engine as any 1325HP V-1710 with 8.1 supercharger gears. Only thing new was just the mechanical first stage. Just an impeller in a diffuser with a hydraulic coupling turned by a shaft from the starter. Pretty simple, just took forever.
P-39 Expert
Non-Expert
Was a little faster than 376mph at 15000'. Would outclimb anything in 1943 except a Spitfire IX.
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Hello P-39 Expert,
I take it you must not have seen the testing of Faber's FW 190A-3 or USN testing of a FW 190A-5/U4.
I believe the A-3 was almost a year earlier and the A-5/U4 had a higher rate of climb AND better speed without running Emergency power.
The early Me 109G was also a bit faster and had comparable climb rates but I am not sure when their engines were cleared to run full manifold pressure.
- Ivan.
- Thread starter
- #111
Shortround6
Major General
Yeah, real simple.
It just took Allison two stages, a hydraulic coupling (with variable speed) to do what R R did with one stage on a Merlin 46. And RR did it well before March of 1942.
Getting airflow to match between two compressors wasn't quite so easy.
That shaft from the starter and the hydraulic coupling (torque converter) had to handle 225 hp at a minimum.
and at part throttle or less than full rated height about 25% of the power used drive the auxiliary compressor went to heating up the oil in the hydraulic coupling. At full boost the loss was only 4%. But the oil cooler for the Auxiliary stage had to get rid of around 45hp worth of heat at lower altitudes.
Working out the increased cooling loads for radiators and oil coolers might not have been that simple. As in the engine needs to make an extra 225hp in the cylinders above what was needed for the same power to the prop in a single stage engine. Now if you are flying in thinner air you need even bigger radiators/oil coolers or improved ducts.
Concepts can be simple, getting them to work under varying conditions sometimes isn't simple.
BTW the -47 engine was originally envisioned with an inter-cooler. As was the -93 engine.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Very informative. After having read about the capture of an intact Zero in probably every book about the Battle of Midway, it doesn't look quite so intact.
Yes, but...it's a tribute to the genius of Horikoshi Jiro that the basic airplane was so simple, straightforward, and non-critical that foreigners accustomed to different hardware, structural materials and design practices, and no usable documentation could repair it, rig it, and flight test it with no manufacturer support. And in a manner that delivered bulletproof reliability.
When a twin row radial suffers a prop strike/sudden stop, an awful lot of rotating mass comes to an abrupt halt, deforming internal parts, which under normal circumstances would be replaced. If you have no spares, no drawings, and no table of limits, reconstituting said parts entails a lot of "by guess and by golly" and infinite opportunities for getting it wrong. Ask our Allison Man, Greg P, how critical these things are in rebuilding an engine, especially one with unfamiliar tolerances, an unfamiliar measurement system, unfamiliar design practices, and no documentation.
Wes,
I was wondering about the prop strike until I looked at the pictures. It appears either the motor was rotating very slowly or had stoped. In the previous shots you can see he basically came down in a marsh and the props appear to have no noticeable damage. The amazing thing to me, along the lines or repairing another countries goods, is that the landing gear were ripped out / off and they were able to fix that. Mechanically skilled at repair is an obvious understatement.
Cheers,
Biff
Peter Gunn
Master Sergeant
I must admit, back when I was in middle school in the 19XX's, I remember reading (probably Caiden) about this "Intact Zero" in the Aleutians that was the DIRECT reason the Hellcat was designed and built. Some numb-nuts writer was actually attributing the whole F6F program (beginning to end) as a response to the Zero. I don't remember how long it was (almost a year I think) before I found out that was not the case, at the time I just knew is was true, but then you keep learning new info everyday, especially here.
So as Tommy Lee Jones said in Men in Black, "Imagine what you'll KNOW... tomorrow.".
So I hereby christen this forum... "Tomorrowland".
So as Tommy Lee Jones said in Men in Black, "Imagine what you'll KNOW... tomorrow.".
So I hereby christen this forum... "Tomorrowland".
Quite likely he was at flight idle or slightly above, as he was trying to make a smooth landing in a grassy field of unknown roughness. I have a book about this Zero with pictures in which the third propeller blade is visible, and it clearly took a hit, stopping the engine from maybe 900-1000 RPM in 1/3 revolution to a dead stop. Yes, the con rods were bent, according to the report of the repairs, not unusual for a reduction geared twin row radial. Two master rods, twelve connecting rods, fourteen pistons, a supercharger disk, a planetary gearset, and a propeller, all slammed to a stop at once in less than half a revolution, something's going to give.
Hello XBe02Drvr, BiffF15,
BiffF15 is correct about the engine not running at the time of the landing.
Anti-aircraft fire over Dutch Harbor had cut an oil line and Koga had flown his crippled bird to a previously scouted site to put it down. From the air, it looked like an open field with high grass.
The plan for pilots in his situation was to put the aircraft down on this island, destroy the plane and then make it to the beach where he could signal for a pre-arranged pickup of downed pilots by submarine.
When Koga touched down, he found a marsh instead of a grassy field, his landing gear dug in, got ripped off and flipped the plane pretty violently. The canopy was crushed, he ended up with a broken neck and his head under water.
As the great philosopher Gomer Pyle would say: "Sur-prise! Sur-prise! Sur-prise!".
His two wingmen had standing orders not to leave a more or less intact aircraft and had plenty of ammunition but chose not to shoot the plane because they thought Koga might still be alive.
The wreck stayed there for a couple months until it was spotted from a passing PBY.
As for being able to recreate the landing gear mechanism, this probably wasn't quite as difficult as it would seem today because there were other crashed A6M2, notably at Pearl Harbor, that had been studied. Hirano's A6M2 was not even close to repairable, but from photographs, it appears that the canopy was intact enough to serve as a template if not to supply parts.
The thing that makes me wonder is that I would have expected force that is violent enough to rip off landing gear might also seriously deform the wing structure.
- Ivan.
BiffF15 is correct about the engine not running at the time of the landing.
Anti-aircraft fire over Dutch Harbor had cut an oil line and Koga had flown his crippled bird to a previously scouted site to put it down. From the air, it looked like an open field with high grass.
The plan for pilots in his situation was to put the aircraft down on this island, destroy the plane and then make it to the beach where he could signal for a pre-arranged pickup of downed pilots by submarine.
When Koga touched down, he found a marsh instead of a grassy field, his landing gear dug in, got ripped off and flipped the plane pretty violently. The canopy was crushed, he ended up with a broken neck and his head under water.
As the great philosopher Gomer Pyle would say: "Sur-prise! Sur-prise! Sur-prise!".
His two wingmen had standing orders not to leave a more or less intact aircraft and had plenty of ammunition but chose not to shoot the plane because they thought Koga might still be alive.
The wreck stayed there for a couple months until it was spotted from a passing PBY.
As for being able to recreate the landing gear mechanism, this probably wasn't quite as difficult as it would seem today because there were other crashed A6M2, notably at Pearl Harbor, that had been studied. Hirano's A6M2 was not even close to repairable, but from photographs, it appears that the canopy was intact enough to serve as a template if not to supply parts.
The thing that makes me wonder is that I would have expected force that is violent enough to rip off landing gear might also seriously deform the wing structure.
- Ivan.
P-39 Expert
Non-Expert
The climb numbers for Faber's 190A-3 as tested by the British have always been an outlier. No other 190A approached that level of climb. Interesting that the British could only get 375mph at 18000' out of it.
Regarding the Navy test of the 190A-5 it climbed about the same as the Hellcat and Corsair. Attached climb graphs of the 190A-6 and the Hellcat show that the P-39N outclimbed both substantially at all altitudes.
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Hello P-39 Expert,
Why would you consider this an outlier? The 190A-3 had an engine of approximately the same power as later versions but was one of the lightest versions built. Why is it a wonder that it should climb very well? The only issues with this testing were that the plugs were probably not in the best of shape and the engine was de-rated but the British did not run it in that manner.
I was referring to the FW 190A-5/U4 that was captured and tested by the USN. It was a ground attack version and did not carry the two outboard cannon. Even so, it carried enough armament with 2 x 20 mm and 2 x 7.92 mm guns to be pretty dangerous. It weighed substantially less than the typical fighter versions and climbed better.
....and no, it did NOT climb the same as the Hellcat and Corsair. That is pretty good performance for a captured bird that isn't even running emergency power.
Why are you so convinced that the Airacobra was a miracle aeroplane?
Either one of these FW 190s was running in the neighbourhood of 1700 - 1750 HP at Sea Level and 1450 - 1550 HP at 20,000 feet. The Airacobra had a nice slick airframe but that doesn't make that much difference at best climb speeds and its airfoil had a relatively low coefficient of lift.
The only place where any of the Airacobra could possibly have comparable power is very near the ground and running manifold pressures well beyond War Emergency.
FW 190A-3 loaded weight is 3855 Kg or 8500 pounds.
FW 190A-5/U4 was ballasted to 8690 pounds for testing which was about 400 pounds less than the typical A-5 fighter with full armament. The A-6 fighter would weigh about 175 pounds even more than that.
- Ivan.
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