P-400 Airacobra In North Africa

[MIflyer]

Allison never added a second speed to the V-1710 single stage supercharger. It would have been trivial for them to have done so and it would have helped the high altitude performance of the P-39, P-40, and V-1710 equipped P-51. And ironically, the first aviation work that Allison did was a geared Liberty engine, so they knew what gears were. But I strongly suspect that the 2nd speed for the V-1710 would have required a whole new rear accessory section, a new casting, and so that part would not have been interchangeable on all of the V-1710's, a disadvantage in production. When they added a mechanically driven second stage to serve as a turbosupercharger alternative they coupled it to the starter drive and used what amounted to a hydromatic transmission to vary the speed of it. Of course the lack of an intercooler/aftercooler would have been a serious disadvantage, anyway.

R-2800 supercharger drawing attached. It must have been a real challenger to remember to turn that stuff on and off while people were shooting at you.

 

[MIflyer]

Okay, I just found something in the Hurricane II manual that clears some things up. The Hurricane II had a manual control to switch between high speed and low speed supercharger. That was what my friend was referring to. And the author of the Killer Cobra article had used that control before moving on to the P-400, which had no supercharger controls at all, leading him to assert the P-400 did not have a supercharger.

The Merlin equipped Mustang originally had a switch to put the supercharger in low speed, in automatic, where it was controlled by an aneroid device and switched to high speed at about 18,000 ft, and a momentary contact spring loaded switch to enable the high speed to be engaged at lower altitudes for test purposes. When P-51's escorted B-29's over Japan the Japanese were wise enough to often refuse to fight above 15,000 ft, since their aircraft were at a distinct disadvantage above that. They tried to lure the P-51's down lower, where the Merlin's high speed supercharger had not engaged yet and the low speed was getting maxed out. At least one Mustang squadron commander instructed the maintenance people to replace the spring loaded switch with a regular toggle switch so he could engage the high speed setting at lower altitudes. The Packard people objected, since the engine could be damaged from such low altitude use of the high speed setting, but the squadron commander was well pleased with the results, which enabled him to nail some Japanese fighters that otherwise would have escaped.

 

[Shortround6]

Allison never added a second speed to the V-1710 single stage supercharger. It would have been trivial for them to have done so and it would have helped the high altitude performance of the P-39, P-40, and V-1710 equipped P-51.

No and quite possibly no.
Allison had trouble making the supercharger drive gears wide enough to handle the load of the 9.60 gears in the space available. I believe the gear case was cast in there rear of the crankcase, They made the auxiliary case deeper to allow for the thicker gears. finding room for the "clutches/planetary gears" and the 2nd gear set might not have been bossible without a substantial change, disrupting production.
Not talked about is the the fact the Merlin production was segregated into factories that made two speed Merlins (both single and two speed) and the home factories that made both.

The problem with the Allison was the actual supercharger, once you stuck a set of 9.60 gears on it it wasn't going to do much better, the tip speed of the impellers was very close to the tip speed of if a Merlin XX supercharger. The Merlin impeller had a 10.5% greater circumference but the Allison impeller was turning 5.6% faster.
You can only turn an impeller so fast before the tips go supersonic inside the supercharger (different conditions than outside air) and the shock waves screw everything up.
They needed a whole new supercharger to really take advantage of a two speed drive.

A two speed drive would have allowed around 1375 -1425hp for take-off (low gear) and kept 1150hp at 15,500ft (high gear) but nobody was asking for that

 

[GreenKnight121]

A two speed drive would have allowed around 1375 -1425hp for take-off (low gear) and kept 1150hp at 15,500ft (high gear) but nobody was asking for that

Exactly... the US Army controlled all military engine production in the US, and they had decided before WW2 that there would be high-altitude fighters with turbosuperchargers (P-38 & P-43/47) and low-medium altitude fighters (P-35, P-36, P-39 [after removal of TS due to drag issues], P-40, and P-51 [until the British fitted it with Merlins]).

Only the USN/USMC were looking for supercharged fighters for all-altitude work, thus the USN's initial single-stage two-speed superchargers on the F4F, then two-stage two-speed superchargers on the F6F and F4U.

 

[MIflyer]

Absurd! The USAAF was not interested in anything but high altitude fighters and made no decision to develop low/medium types and high altitude ones on parallel paths. The P-36 brought up to world standards was supposed to be the P-37, with a V-1710 and a turbo. The upgraded P-35 was supposed to be the XP-41, with a two stage mechanically supercharged R-1830 (like the F4F), but when Seversky demonstrated that the same airplane with a turbo was even better with its AP-4, that yielded the P-43. The P-39 was supposed to have a turbo. Trouble is most of this did not work out as planned. The YP-37 was a huge improvement over the P-36, 50 mph faster at over 20,000 ft, but the cockpit had to be so far back as to be unworkable; the next best thing was the same airplane without a turbo, the P-40. The P-39 had its turbo deleted not because they wnaed a low/medium altitude fighter but because it made the airplane slower than just using the single stage mechanical supercharger, so they again went with the best they could come up with at the time. The P-43 they built, with a turbo up upscaling the airplane with an R-2800 was a much better idea.

The P-51 was not a factor, not even being on the horizon. Presented with the fact it was better than the other single engine fighters they were building, they grabbed some off an RAF order but when they put in their own order it was for the airplane as a dive bomber, not a fighter. The P-51A was built because at the start of A-36A production the news on the Merlin 61 installation came out. The P-51A was built only to keep the production line hot between the end of A-36A and start of P-51B production; all the P-51A's were built in a single month and not because they wanted low/medium altitude fighters. And besides, they had to pay back the RAF for the P51-1/Mustang Mk 1A's they swiped off their contract.

The follow on to the P-39 was the P-63, another high altitude fighter, which solved the lack of a turbo by putting in the auxilliary supercharger; the first one flew in 1942.

One thing everybody in the world figured out by late 1941 was that single engined fighters powered by engines under 2000 cu inches were not going to cut the mustard. So the P-38 and the P-47, were the favored fighters, as well as new beasts such as the XP-58 and P-61. Stanley Hooker's two stage Merlin was a happy surprise, built for a highly specialized application, but enabling the smallest displacement front line fighter engine of the war to be world beater. Even the A6M3 had 1700 cu inches, 50 more than the Merlin.

The US Navy made a decision to go with both low altitude and high altitude fighters, with the single stage FM-2 as well as the two stage F4U and F6F. Ironically, both the F7F and F8F had single stage superchargers, and that was because the USN found out that the Japanese were not a high altitude threat and all those big two stage supercharged bombers high overhead had big white stars on them.

As for the impeller diameter on the V-1710, well, now, they could have fixed that too when they built a new two speed accessory section.

 

[Shortround6]

Pretty much.

The high altitude fighters were what they wanted.
The low/medium altitude fighters were what they could actually get (build).
In the Spring of 1939 the Army figured that the P-39 and P-40 were around one year away from start of delivery.
The planes with turbo chargers were 2 years away from squadron service. (and they missed on that one).

The US had built more planes with turbochargers than the rest of the world put together by a large margin. The Turbos and turbo controls were not ready for normal squadron service.

We use impeller diameter as sort of a short hand. The Allison needed an entire new supercharger. Inlet, impeller, diffuser capable of handling a both a greater air flow mass and a higher pressure ratio.
The supercharger in the P-40N could pressurize the air at 15,500ft 2.69 times the outside air and deliver the pounds of air per hour needed to make 1150hp at the prop (several hundred HP more in the cylinders).

If you want 44.5 in of pressure at 20,000ft you need to pressurize the air 3.23 times and flow enough air to not only make the power you did at 15,500 but the extra power the supercharger needs to do the extra work.

Next thing that is often ignored is the efficiency of the supercharger.
You can spin it faster, up to a point, but the faster you spin it the worse the efficiency gets (you do have to spin a centrifugal compressor some (5,000-10,000rpm) to get them to work.)
Which means you get less compression for the amount of power you put in and you get more heat in the intake charge. A supercharger that is 70% efficient, which is actually pretty good, is turning 30% of the power of the supercharger shaft into pure heat, over and above the work of compressing the air and that temperature rise. Push the Supercharger past it's limits and you could drop to 60% efficiency or below.

 

[GregP]

I think Greenknight is correct. The U.S. military specified what they wanted and the only turbocharged fighter of the ones we went into the war with was the P-38 except for the P-39 prototype. So, they got what the ordered ... low to medium altitude fighters. They may have desired high-altitude aircraft, but they didn't exactly order them that way, and the very certainly didn't COME that way except for the P-38. And it wasn't fully debugged when it was first deployed.

The P-43 was an abortive attempt that didn't really go anywhere except to the development of the P-47, which turned out to be a VERY good development. They only built 242 P-43s and they never really DID anything in service, the turbos were unreliable and the wet wing weeped constantly. Most of them either went to China or were used in training after being modified for PR work.

That basically left us with the P-38 that needed the pilots trained better, needed cockpit heaters and the intake and incompatible fuel issues fixed. All that took about 9 months to fix. By then, the P-47 was out and the P-51 wasn't too far away from making itself felt on the front lines.

 

[Alex Smart]

Here is a list I made a while ago of those a/c that were Transferred to the USA before export and after export . (c/n = construction number).

AH579 - Crashed in USA 41/07/10, F.H.Kelly, 1/2 mile NE Niagara Falls.
AH580 - Transfered to the Americans after export to the UK.
AH587 - Transfered to the Americans after export to the UK.
AH589 - Transfered to the Americans after export to the UK.
AH594 - Transfered to the Americans after export to the UK.
AH597 - Transfered to the Americans after export to the UK, accident in UK 421218 P.S.Martin 350 FS
AH600 - Transfered to the Americans after export to the UK.
AH609 - Transferred to the Americans after export to the UK. Accident in UK 421221 - R.J.Drayton.
AH637 - Transferred to the Americans after export to the UK.
AH648 - Transferred to the Americans after export to the UK.
AH701 - Transferred to Americans after export to the UK ( salvaged 431220 ).
AH713 - Transferred to Americans after export to the UK - To USSR (?)
AH728 (c/n 14-159) transferred to USSR. Reports that it was lost at sea, but other reports have it
actually having been delivered. There are reports of this plane being diverted to Austraila
and condemed there Sept 3, 1944.
AH732 - Transferred in the USA.
AH735 - Transferred in the USA.
AH736 - Transferred in the USA.
AH737 - Transferred in the USA - Not delivered to Britain, To USSR. There are reports of this plane being diverted to Australia in March 42 and condemned there on 430413.
AH738 - Transferred in the USA.

AP266/268 to USAAF
AP274 to USAAF
AP278 to USAAF
AP280 to USAAF
AP287 to USAAF
AP290 to USAAF
AP291 to USAAF
AP295 to USAAF
AP297 to USAAF
AP300 to USAAF
AP304 to USAAF
AP305 to USAAF
AP319 to USAAF
AP322 to USAAF
AP326/346 to USAAF
AP335 to USAAF. crashed landed Aug 2, 1943 at Lakekamu River, PNG
AP347 to USAAF. force landed Aug 20, 1943 at emergency strip with 36th FS of 8th FG. Retrieved by RAAF Chinook and now rests at the Jackson's Airport Pilots Club in a fenced enclosure.
AP348/357 to USAAF
AP359/360 to USAAF
AP361 to USAAF. Pilot bailed out near 14-Mile Drome PNG Jun 18, 1942.
AP362/383 to USAAF

BW100/105 to USAAF
BW107/108 to USAAF
BW110/117 to USAAF.
BW114 was c/n 14-306 and came to Australia Apr 1942 for conversion for RAAF. Damaged
Feb 10, 1943, condemned Apr 1, 1944.
BW118 delivered to RAF and returned to USAAF
BW119/130 to USAAF
BW134/148 to USAAF
BW150/168 to USAAF
BW169 to USAAF. pilot bailed north of Port Moresby PNG Jun 18, 1942.
BW170/183 to USAAF

BX135 to USAAF. condemned Sep 3, 1944
BX136 to USAAF. condemned Nov 25, 1942
BX137 to USAAF. wrecked at Tontouta AB, New Caledonia Jun 7, 1942
BX138 to USAAF. wrecked at Tontouta AB, New Caledonia Jun 9, 1942
BX139 to USAAF. condemned Oct 27, 1943
BX140 to USAAF. condemned Sep 3, 1944
BX141 to USAAF wrecked Jan 28, 1942 at Margualo Station. Pilot bailed out OK.
BX142 to USAAF. condemned Sep 3, 1944
BX143 to USAAF. condemned Apr 27, 1943
BX144 to USAAF. condemned Sep 3, 1944
BX145 to USAAF. to CL-26 Mar 19, 1942
BX146 to USAAF. condemned Sep 3, 1944
BX147 to USAAF. condemned Sep 3, 1944
BX148 to USAAF. condemned Sep 3, 1944
BX149 to USAAF. condemned Mar 23, 1943
BX150 to USAAF. wrecked Jun 8, 1942 at Tontouta AAB, New Caledonia.
BX151 to USAAF. condemned Nov 25, 1942
BX152 to USAAF. wrecked Jun 8, 1942 at New Caledonia.
BX153 to USAAF. condemned Sep 3, 1944
BX154 to USAAF. condemned Nov 25, 1942.
BX155 to USAAF. condemned Sep 3, 1944
BX156 to USAAF. condemned Nov 25, 1942
BX157 to USAAF. condemned Nov 25, 1942
BX158 to USAAF. condemned Mar 23, 1942
BX159 to USAAF. condemned Nov 25, 1942
BX160 to USAAF. condemned Nov 1, 1942
BX161 to USAAF. condemned Nov 25, 1942
BX162 to USAAF. condemned Mar 23, 1943
BX163 to USAAF. Ernest J Sharp, USAAF, 81 FG. condemned Dec 28, 1942
BX164 to USAAF. surveyed Jan 24, 1944
BX165 to USAAF. With 8th Fg, 36th FS, engine cut out and crashlanded short of runway, Durand, NG May 24, 1943. Condemned May 27, 1943
BX166 to USAAF. condemned Sep 3, 1944
BX167 (c/n 14-359) to USAAF. surveyed Jul 14, 1944
BX168 to USAAF. condemned Oct 27, 1943
BX169 to USAAF. condemned Sep 3, 1944
BX170 to USAAF. condemned Aug 30, 1942
BX171 to USAAF. surveyed in USA Jul 15, 1945
BX172 to USAAF. to RFC in Cincinatti Feb 10, 1945
BX173 to USAAF. condemned Sep 3, 1944
BX174 (c/n 14-415) to USAAF. condemned Nov 23, 1942
BX187 ended up with USAAF in UK in 1942
BX192 to USAAF. to RFC at Rome, NY Aug 8, 1945
BX204 to USAAF. off inventory Feb 29, 1944
BX206 to USAAF. to RFC at Yuma AAF, AZ Mar 20, 1945
BX209 to USAAF. salvaged Aug 17, 1944
BX210 to USAAF. to RFC at Yuma AAF, AZ Feb 29, 1945
BX216 to USAAF. to RFC at Yuma AAF, AZ Apr 4, 1945
BX227 to USAAF. to RFC at Yuma AAF, Mar 16, 1945
BX245 to USAAF. to RFC at Rome, NY May 8, 1945
BX247 to USAAF. off inventory Aug 26, 1944
BX270 to USAAF. to RFC at Yuma AAF, AZ Feb 29, 1945
BX279 to USAAF. to RFC at Yuma AAF, AZ Mar 24, 1945
BX290 to USAAF. condemned Jul 8, 1944
BX302 to USAAF. Shipped overseas after Oct 1943. Returned to USA Jul 30, 1944.
To RFC at Rome, NY May 8, 1945. There is a photo of this aircraft in Soviet AF colors.
BX310 to USAAF. to Italy Feb 11, 1946
BX320 to USAAF. crashed May 27, 1944
BX323 to USAAF. surveyed in USA Mar 2, 1944
BX326 to USAAF. to RFC at Yuma AAF, AZ Mar 20, 195
BX327 to USAAF. to RFC at Yuma AAF, AZ
BX345 to USAAF. salvaged Jun 12, 1944
BX348 to USAAF. to RFC at Yuma AAF, AZ Mar 16, 1945
BX409 to USAAF. to reclamation at Luke AAF, AZ Mar 13, 1946
BX424 to USAAF. salvaged Nov 9, 1944.

Refs :
Air Britain RAF Serial number series. And The British Air Commission and lend-Lease.
And Joe Baughers USAAF Serial number website.

 

[MrSmoothie]

I read the Air Classics article with great interest. Aside from the first-person content, I realized it was the same author who wrote a similar article about the Northrop P-61 Black Widow that was in the first issue of Air Classics I ever got my hands on, in 1970, at age 10. Evidently Davidson thought it was an amazing fighter in the right hands, and quite counter to a recent article I read (online) from Aviation History, which pretty much dismissed the P-61 as a failure. If anybody is interested, I will upload the P-61 article so you can see Bob's opinions for yourselves (if a PDF can be uploaded on this site).

A couple of things -- how is a 20mm cannon (that works sometimes), two fuselage-mounted (and thus non-converging) .50's, plus four wing-mounted .303's "inferior" to the armament of a Spitfire or Hurricane (I assume he was referring to the eight .303 armament)? Maybe he was thinking of later versions incorporating 20mm cannon which was what they had by 1943?

I was interested in (and enlightened by) the reasons why visibility out of the cockpit was so bad, since at a glance, it looks like a later bubble canopy. This is something I've been thinking about since the unfortunate collision of the P-63 and B-15 in Texas. But how is this different, exactly, than seeing rearwards in a Spitfire, which only had a bit of a bulge in the canopy sides, and from what I've read, was a very tight cockpit as well? Maybe the P-39's framing aside the headrest made it worse than the Spit or Hurricane.

There was also a caption that caught my eye (surely not written by the author): "...this Airacobra had its wings clipped for early postwar racing by Tex Johnston. Giving a fine performance, it still couldn't keep up with its contemporary P-51s and P-38s."

First, I don't believe the wings were clipped on Cobra II (there was a heavily clipped P-61), although it was highly modified for racing. Secondly, um, it won the 1946 Thompson Trophy race. Surely the pilot was important, but he couldn't have done it going slower.

 

[tomo pauk]

Disengaging it is easy. It is a device called a "Clutch" and the F4F, F6F, F4U, and P-61 had the ability to manually engage the supercharger speeds. The Merlin Mustang had the option to manually engage the high speed supercharger, but except for modified airplanes that switch was spring loaded and had to be held in position. As for the Spitfire having that option a friend of mine, who joined the RAF and went to the UK prior to Pearl Harbor, described that. But I have not checked the pilot's manuals.

There was no option to un-clutch (or to disengage) the S/C on any Merlin. Same with V-1710, and same with any 1-stage supercharger on the ww2 engines worth speaking about. Even the V-1710s could not un-clutch any of the two supercharges.
On the Merlins with 2-speed drives, clutch was there in order for drive ratio to be changed, still there was no option for pilot to un-clutch S/C.

 

[gingerbob]

Spun in while taxiing?

Maybe he got too high.

 

[PAT303]

There was no option to un-clutch (or to disengage) the S/C on any Merlin. Same with V-1710, and same with any 1-stage supercharger on the ww2 engines worth speaking about. Even the V-1710s could not un-clutch any of the two supercharges.
On the Merlins with 2-speed drives, clutch was there in order for drive ratio to be changed, still there was no option for pilot to un-clutch S/C.

I do remember reading in not much of an engineer? that the S/C could be de-clutched but that was incase the pilot cut the throttle allowing it to free spin, the pilot had no control over it at all, it was just to stop the impellors from exploding going from thousands of RPM to idle. If someone has a copy of Hookers book at hand they could possibly find where Hooker explainad it.

 

[Geoffrey Sinclair]

Here is a list I made a while ago of those a/c that were Transferred to the USA before export and after export . (c/n = construction number).

Nice list, this is the RAF view of things from the Serial Registers, plus some checking of the USAAF Delivery Logs. Exports to Russsia were first shipped to Britain from the US, the month and dates are when the RAF said the aircraft was exported.

Order 218, Serials AH, Retained in Britain 29, To USAAF in USA 6, Crashed in USA 2, To Russia from Britain 122, To USAAF in UK 11, Total 170, Lost at Sea en Route to Russia 10
Order 1326, Serials AP, BW, Retained in Britain 1, To USAAF in USA 150, To Russia from Britain 38, To USAAF in UK 16, Total 205, Lost at Sea en Route to Russia 14
Order 1476, Serials BX, Retained in Britain 2, To USAAF in USA 40, To Russia from Britain 106, To USAAF in UK 152, Total 300, Lost at Sea en Route to Russia 30
Totals, Retained in Britain 32, To USAAF in USA 196, Crashed in USA 2, To Russia from Britain 266, To USAAF in UK 179, Total 678, Lost at Sea en Route to Russia 54

Of the 196 P-400 retained in the US, 177 arrived in Australia February/March 1942, along with 3 P-39, 62 P-39C and 81 P-39D.

The list, AANA = Air Arsenal North America. TOC/SOC Taken/Struck Off Charge.

serial \ User \ Month \ Date \ Note
AH570 \ Russia \ 194205 \ 18-May-42 \
AH571 \ Russia \ 194205 \ 18-May-42 \
AH572 \ Britain SOC 5-Oct-46
AH573 \ Britain SOC 11-Feb-42
AH574 \ Britain Admiralty
AH575 \ Russia \ 194209 \ 22-Sep-42 \
AH576 \ Britain SOC 22-Aug-42
AH577 \ Russia \ 194209 \ 9-Sep-42 \
AH578 \ Britain Instructional 2808M
AH579 \ Not Delivered Crashed in US on test flight 10 July 1941
AH580 \ USAAF in UK
AH581 \ Britain SOC 1-Dec-41
AH582 \ Britain SOC 26-Oct-41
AH583 \ Britain SOC 20-Jul-42
AH584 \ Russia \ 194207 \ 4-Jul-42 \
AH585 \ Britain SOC 22-Feb-42
AH586 \ Russia \ 194209 \ 9-Sep-42 \
AH587 \ USAAF in UK
AH588 \ Britain SOC 20-Jul-42
AH589 \ USAAF in UK
AH590 \ Britain SOC 16-Apr-42
AH591 \ Britain SOC 2-Jul-42
AH592 \ Britain SOC 20-Jul-42
AH593 \ Britain SOC 20-Jul-42
AH594 \ USAAF in UK Earmarked
AH595 \ Britain SOC 20-Jul-42
AH596 \ Britain SOC 14-Oct-41
AH597 \ USAAF in UK
AH598 \ Britain SOC 15-Nov-41
AH599 \ Russia \ 194111 \ 16-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH600 \ USAAF in UK
AH601 \ Britain SOC 2-Feb-42
AH602 \ Britain SOC 10-Mar-42
AH603 \ Britain SOC 21-NOv-41
AH604 \ Russia \ 194111 \ 16-Nov-41 \
AH605 \ Russia \ 194111 \ 23-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH606 \ Russia \ 194206 \ 21-Jun-42 \
AH607 \ Russia \ 194111 \ 16-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH608 \ Russia \ 194111 \ 16-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH609 \ USAAF in UK
AH610 \ Russia \ 194111 \ 10-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH611 \ Russia \ 194205 \ 18-May-42 \ Russia <date> crossed out, but Russia rewritten
AH612 \ Russia \ 194112 \ 12-Dec-41 \ Russia <date> crossed out, but Russia rewritten
AH613 \ Russia \ 194202 \ 14-Feb-42 \ Russia <date> crossed out, but Russia rewritten
AH614 \ Britain SOC 16-Aug-42
AH615 \ Russia \ 194201 \ 27-Jan-42 \
AH616 \ Russia \ 194204 \ 2-Apr-42 \
AH617 \ Russia \ 194202 \ 8-Feb-42 \
AH618 \ Russia \ 194201 \ 24-Jan-42 \
AH619 \ Russia \ 194203 \ 24-Mar-42 \
AH620 \ Russia \ 194201 \ 27-Jan-42 \
AH621 \ Not Delivered Crashed in USA.
AH622 \ Russia \ 194111 \ 27-Nov-41 \
AH623 \ Russia \ 194111 \ 27-Nov-41 \
AH624 \ Russia \ 194111 \ 20-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH625 \ Russia \ 194111 \ 20-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH626 \ Russia \ 194111 \ 20-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH627 \ Russia \ 194201 \ 3-Jan-42 \
AH628 \ Russia \ 194111 \ 19-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH629 \ Britain SOC 6-Nov-41 Instructional 2796M
AH630 \ Russia \ 194111 \ 27-Nov-41 \
AH631 \ Russia \ 194111 \ 27-Nov-41 \
AH632 \ Russia \ 194111 \ 16-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH633 \ Russia \ 194111 \ 23-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH634 \ Russia \ 194111 \ 18-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH635 \ Russia \ 194111 \ 27-Nov-41 \
AH636 \ Russia \ 194201 \ 17-Jan-42 \ Russia <date> crossed out, but Russia rewritten to same date
AH637 \ USAAF in UK
AH638 \ Russia \ 194112 \ 9-Dec-41 \ Russia <date> crossed out, but Russia rewritten
AH639 \ Russia \ 194112 \ 19-Dec-41 \ Russia <date> crossed out, but Russia rewritten
AH640 \ Russia \ 194111 \ 20-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH641 \ Russia \ 194111 \ 19-Nov-41 \
AH642 \ Russia \ 194111 \ 19-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH643 \ Russia \ 194112 \ 18-Dec-41 \ Russia <date> crossed out, but Russia rewritten
AH644 \ Russia \ 194111 \ 18-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH645 \ Russia \ 194111 \ 27-Nov-41 \
AH646 \ Russia \ 194201 \ 6-Jan-42 \
AH647 \ Russia \ 194112 \ 9-Dec-41 \ Russia <date> crossed out, but Russia rewritten
AH648 \ USAAF in UK
AH649 \ Russia \ 194111 \ 21-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH650 \ Russia \ 194201 \ 30-Jan-42 \
AH651 \ Russia \ 194209 \ 10-Sep-42 \ Lost At Sea
AH652 \ Russia \ 194112 \ 12-Dec-41 \ Russia <date> crossed out, but Russia rewritten
AH653 \ Russia \ 194111 \ 27-Nov-41 \
AH654 \ Russia \ 194112 \ 20-Dec-41 \
AH655 \ Russia \ 194112 \ 28-Dec-41 \
AH656 \ Britain
AH657 \ Britain
AH658 \ Russia \ 194201 \ 16-Jan-42 \
AH659 \ Russia \ 194112 \ 31-Dec-41 \
AH660 \ Russia \ 194112 \ 17-Dec-41 \
AH661 \ Britain
AH662 \ Russia \ 194202 \ 26-Feb-42 \ Lost At Sea
AH663 \ Russia \ 194112 \ 15-Dec-41 \ Russia <date> crossed out, but Russia rewritten
AH664 \ Russia \ 194201 \ 17-Jan-42 \
AH665 \ Russia \ 194201 \ 3-Jan-42 \
AH666 \ Russia \ 194201 \ 6-Jan-42 \
AH667 \ Russia \ 194205 \ 18-May-42 \ Russia <date> crossed out, but Russia rewritten
AH668 \ Russia \ 194201 \ 30-Jan-42 \
AH669 \ Russia \ 194112 \ 12-Dec-41 \
AH670 \ Russia \ 194201 \ 10-Jan-42 \
AH671 \ Russia \ 194202 \ 9-Feb-42 \
AH672 \ Britain
AH673 \ Russia \ 194112 \ 19-Dec-41 \ Russia <date> crossed out, but Russia rewritten
AH674 \ Russia \ 194201 \ 13-Jan-42 \
AH675 \ Russia \ 194201 \ 9-Jan-42 \ Russia <date> crossed out, but Russia rewritten
AH676 \ Russia \ 194201 \ 3-Jan-42 \
AH677 \ Russia \ 194111 \ 20-Nov-41 \ Russia <date> crossed out, but Russia rewritten
AH678 \ Russia \ 194202 \ 9-Feb-42 \
AH679 \ Russia \ 194201 \ 16-Jan-42 \
AH680 \ Russia \ 194202 \ 10-Feb-42 \
AH681 \ Russia \ 194201 \ 8-Jan-42 \
AH682 \ Russia \ 194201 \ 16-Jan-42 \
AH683 \ Russia \ 194201 \ 3-Jan-42 \
AH684 \ Russia \ 194205 \ 18-May-42 \ Russia <date> crossed out, but Russia rewritten, TOC same date as export
AH685 \ Russia \ 194111 \ 15-Nov-41 \ TOC same date as export
AH686 \ Russia \ 194111 \ 15-Nov-41 \ TOC same date as export
AH687 \ Russia \ 194111 \ 15-Nov-41 \ TOC same date as export
AH688 \ Russia \ 194201 \ 13-Jan-42 \
AH689 \ Russia \ 194201 \ 27-Jan-42 \
AH690 \ Russia \ 194201 \ 8-Jan-42 \
AH691 \ Russia \ 194205 \ 18-May-42 \
AH692 \ Russia \ 194201 \ 24-Jan-42 \
AH693 \ Britain SOC 16-Aug-42
AH694 \ Russia \ 194202 \ 9-Feb-42 \
AH695 \ Russia \ 194202 \ 9-Feb-42 \
AH696 \ Britain SOC 18-Aug-42
AH697 \ Russia \ 194201 \ 15-Jan-42 \
AH698 \ Britain
AH699 \ Russia \ 194205 \ 23-May-42 \ Lost At Sea
AH700 \ Russia \ 194205 \ 18-May-42 \ Russia <date> crossed out, but Russia rewritten, TOC same date as export
AH701 \ USAAF in UK
AH702 \ Russia \ 194201 \ 10-Jan-42 \
AH703 \ Russia \ 194201 \ 16-Jan-42 \
AH704 \ Russia \ 194201 \ 13-Jan-42 \
AH705 \ Russia \ 194203 \ 2-Mar-42 \ Lost At Sea
AH706 \ Russia \ 194201 \ 13-Jan-42 \
AH707 \ Russia \ 194201 \ 24-Jan-42 \
AH708 \ Russia \ 194201 \ 21-Jan-42 \
AH709 \ Russia \ 194201 \ 17-Jan-42 \
AH710 \ Russia \ 194201 \ 9-Jan-42 \
AH711 \ Russia \ 194205 \ 18-May-42 \ Russia <date> crossed out, but Russia rewritten, TOC same date as export
AH712 \ USAAF in UK
AH713 \ Russia \ 194201 \ 17-Jan-42 \
AH714 \ Russia \ 194202 \ 14-Feb-42 \
AH715 \ Russia \ 194202 \ 14-Feb-42 \
AH716 \ Russia \ 194202 \ 9-Feb-42 \
AH717 \ Russia \ 194202 \ 9-Feb-42 \
AH718 \ Russia \ 194205 \ 18-May-42 \ TOC same date as export
AH719 \ Russia \ 194201 \ 27-Jan-42 \
AH720 \ Russia \ 194201 \ 17-Jan-42 \
AH721 \ Russia \ 194205 \ 18-May-42 \ Russia <date> crossed out, but Russia rewritten, ToC at Speke
AH722 \ Russia \ 194202 \ 26-Feb-42 \ Lost At Sea
AH723 \ Russia \ 194203 \ 24-Mar-42 \
AH724 \ Russia \ 194203 \ 24-Mar-42 \
AH725 \ Russia \ 194205 \ 18-May-42 \ Russia <date> crossed out, but Russia rewritten, ToC at Speke
AH726 \ Russia \ 194201 \ 24-Jan-42 \
AH727 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
AH728 \ USAAF in USA AANA says to Russia
AH729 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
AH730 \ Russia \ 194205 \ 18-May-42 \
AH731 \ Russia \ 194205 \ 12-May-42 \ Lost At Sea
AH732 \ USAAF in USA
AH733 \ Russia \ 194205 \ 18-May-42 \
AH734 \ Russia \ 194205 \ 12-May-42 \ Lost At Sea
AH735 to AH738 USAAF in USA

AH739 \ Russia \ 194205 \ 12-May-42 \ Lost At Sea
AP264 \ Russia \ 194205 \ 18-May-42 \
AP265 \ Russia \ 194205 \ 18-May-42 \
AP266 to AP268 USAAF in USA

AP269 \ USAAF in UK
AP270 \ USAAF in UK
AP271 \ Russia \ 194206 \ 21-Jun-42 \
AP272 \ Russia \ 194207 \ 4-Jul-42 \ S.105
AP273 \ USAAF in UK
AP274 \ USAAF in USA
AP275 \ Russia \ 194206 \ 21-Jun-42 \
AP276 \ Russia \ 194205 \ 14-May-42 \ Lost At Sea
AP277 \ USAAF in UK
AP278 \ USAAF in USA
AP279 \ Russia \ 194206 \ 22-Jun-42 \
AP280 \ USAAF in USA
AP281 \ USAAF in UK
AP282 \ Russia \ 194207 \ 4-Jul-42 \
AP283 \ Russia \ 194206 \ 15-Jun-42 \ Lost At Sea
AP284 \ USAAF in UK
AP285 \ Russia \ 194209 \ 10-Sep-42 \
AP286 \ USAAF in UK
AP287 \ USAAF in USA
AP288 \ USAAF in UK
AP289 \ USAAF in UK
AP290 \ USAAF in USA
AP291 \ USAAF in USA
AP292 \ USAAF in UK
AP293 \ Russia \ 194205 \ 18-May-42 \
AP294 \ USAAF in UK
AP295 \ USAAF in USA
AP296 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
AP297 \ USAAF in USA
AP298 \ Russia \ 194205 \ 17-May-42 \
AP299 \ Russia \ 194206 \ 3-Jun-42 \
AP300 \ USAAF in USA
AP301 \ Russia \ 194205 \ 18-May-42 \
AP302 \ Russia \ 194205 \ 23-May-42 \ Lost At Sea
AP303 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
AP304 \ USAAF in USA
AP305 \ USAAF in USA
AP306 \ Russia \ 194205 \ 14-May-42 \ Lost At Sea
AP307 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
AP308 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
AP309 \ Britain
AP310 \ USAAF in UK Arrived 9 July 1942, last import?
AP311 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
AP312 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
AP313 \ Russia \ 194205 \ 29-May-42 \ Lost At Sea
AP314 \ Russia \ 194206 \ 22-Jun-42 \
AP315 \ Russia \ 194207 \ 4-Jul-42 \ S.105
AP316 \ Russia \ 194207 \ 4-Jul-42 \ S.105
AP317 \ Russia \ 194209 \ 10-Sep-42 \ Lost At Sea
AP318 \ Russia \ 194206 \ 3-Jun-42 \
AP319 \ USAAF in USA
AP320 \ Russia \ 194205 \ 29-May-42 \
AP321 \ Russia \ 194206 \ 21-Jun-42 \
AP322 \ USAAF in USA
AP323 \ Russia \ 194205 \ 29-May-42 \ Lost At Sea
AP324 \ Russia \ 194206 \ 3-Jun-42 \
AP325 \ USAAF in UK
AP326 to AP357 USAAF in USA

AP358 \ Russia \ 194206 \ 26-Jun-42 \
AP359 to AP383 USAAF in USA

AP384 \ Russia \ 194206 \ 26-Jun-42 \
BW100 to BW105 USAAF in USA

BW106 \ Russia \ 194206 \ 15-Jun-42 \ Lost At Sea
BW107 \ USAAF in USA
BW108 \ USAAF in USA
BW109 \ Russia \ 194206 \ 22-Jun-42 \
BW110 to BW117 USAAF in USA

BW118 \ USAAF in UK
BW119 to BW130 USAAF in USA

BW131 \ Russia \ 194206 \ 21-Jun-42 \
BW132 \ USAAF in UK
BW133 to BW148 USAAF in UK

BW149 \ Russia \ 194206 \ 3-Jun-42 \
BW150 to BW183 USAAF in USA

BX135 to BX174 USAAF in USA

BX175 \ USAAF in UK
BX176 \ Russia \ 194207 \ 26-Jul-42 \
BX177 \ USAAF in UK
BX178 \ Russia \ 194207 \ 24-Jul-42 \
BX179 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX180 \ USAAF in UK
BX181 \ USAAF in UK
BX182 \ Russia \ 194209 \ 9-Sep-42 \
BX183 \ USAAF in UK
BX184 \ Russia \ 194209 \ 9-Sep-42 \
BX185 \ Russia \ 194209 \ 22-Sep-42 \
BX186 \ USAAF in UK
BX187 \ USAAF in UK
BX188 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX189 \ USAAF in UK
BX190 \ Russia \ 194209 \ 10-Sep-42 \ Lost At Sea
BX191 \ Russia \ 194209 \ 10-Sep-42 \ Lost At Sea
BX192 to BX205 USAAF in UK

BX206 \ Russia \ 194209 \ 10-Sep-42 \
BX207 \ Russia \ 194209 \ 9-Sep-42 \
BX208 to BX211 USAAF in UK

BX212 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX213 \ USAAF in UK
BX214 \ Russia \ 194209 \ 10-Sep-42 \
BX215 to BX220 USAAF in UK

BX221 \ Russia \ 194209 \ 10-Sep-42 \ Lost At Sea
BX222 \ USAAF in UK
BX223 \ USAAF in UK
BX224 \ USAAF in UK
BX225 \ Russia \ 194206 \ 3-Jun-42 \
BX226 \ Russia \ 194206 \ 23-Jun-42 \
BX227 \ USAAF in UK
BX228 \ Russia \ 194207 \ 4-Jul-42 \
BX229 \ Russia \ 194209 \ 7-Sep-42 \
BX230 \ USAAF in UK
BX231 \ USAAF in UK
BX232 \ Russia \ 194205 \ 13-May-42 \ Lost At Sea
BX233 \ Russia \ 194206 \ 3-Jun-42 \
BX234 \ Russia \ 194206 \ 20-Jun-42 \
BX235 \ Russia \ 194206 \ 21-Jun-42 \
BX236 \ Russia \ 194206 \ 24-Jun-42 \
BX237 \ Russia \ 194205 \ 17-May-42 \
BX238 \ USAAF in UK
BX239 \ Russia \ 194205 \ 12-May-42 \ Lost At Sea
BX240 \ Russia \ 194206 \ 24-Jun-42 \
BX241 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX242 \ Russia \ 194206 \ 26-Jun-42 \
BX243 \ USAAF in UK
BX244 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX245 \ USAAF in UK
BX246 \ Russia \ 194209 \ 9-Sep-42 \
BX247 to BX251 USAAF in UK

BX252 \ Russia \ 194205 \ 18-May-42 \
BX253 \ USAAF in UK
BX254 \ Russia \ 194206 \ 21-Jun-42 \
BX255 \ Russia \ 194206 \ 21-Jun-42 \
BX256 \ USAAF in UK
BX257 \ Russia \ 194205 \ 29-May-42 \
BX258 \ Russia \ 194209 \ 7-Sep-42 \
BX259 \ Russia \ 194206 \ 23-Jun-42 \
BX260 \ USAAF in UK
BX261 \ Russia \ 194206 \ 21-Jun-42 \
BX262 \ USAAF in UK
BX263 \ Russia \ 194205 \ 23-May-42 \ Lost At Sea
BX264 \ Russia \ 194209 \ 21-Sep-42 \ Lost At Sea
BX265 \ USAAF in UK
BX266 \ Russia \ 194206 \ 20-Jun-42 \
BX267 \ Russia \ 194206 \ 23-Jun-42 \
BX268 \ Russia \ 194209 \ 9-Sep-42 \
BX269 \ USAAF in UK
BX270 \ USAAF in UK
BX271 \ Russia \ 194209 \ 22-Sep-42 \
BX272 \ USAAF in UK
BX273 \ USAAF in UK
BX274 \ USAAF in UK
BX275 \ Russia \ 194206 \ 23-Jun-42 \
BX276 \ USAAF in UK
BX277 \ Russia \ 194207 \ 6-Jul-42 \
BX278 to BX281 USAAF in UK

BX282 \ Russia \ 194206 \ 23-Jun-42 \
BX283 \ USAAF in UK
BX284 \ Russia \ 194206 \ 3-Jun-42 \
BX285 \ Russia \ 194206 \ 20-Jun-42 \
BX286 \ USAAF in UK
BX287 \ USAAF in UK
BX288 \ USAAF in UK
BX289 \ Russia \ 194209 \ 21-Sep-42 \
BX290 \ Russia \ 194209 \ 10-Sep-42 \ Lost At Sea
BX291 \ Russia \ 194209 \ 10-Sep-42 \
BX292 \ USAAF in UK
BX293 \ USAAF in UK
BX294 \ USAAF in UK
BX295 \ Russia \ 194209 \ 9-Sep-42 \
BX296 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX297 \ USAAF in UK
BX298 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX299 \ USAAF in UK
BX300 \ Russia \ 194209 \ 9-Sep-42 \
BX301 \ Russia \ 194305 \ 19-May-43 \ Blank Serial Register.
BX302 \ USAAF in UK
BX303 \ USAAF in UK
BX304 \ USAAF in UK
BX305 \ Russia \ 194206 \ 23-Jun-42 \
BX306 to BX313 USAAF in UK

BX314 \ Britain Category E
BX315 \ Russia \ 194209 \ 22-Sep-42 \
BX316 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX317 \ USAAF in UK
BX318 \ USAAF in UK
BX319 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX320 \ USAAF in UK
BX321 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX322 \ Russia \ 194209 \ 9-Sep-42 \
BX323 \ USAAF in UK
BX324 \ Russia \ 194209 \ 20-Sep-42 \
BX325 \ USAAF in UK
BX326 \ USAAF in UK
BX327 \ USAAF in UK
BX328 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX329 \ USAAF in UK
BX330 \ USAAF in UK
BX331 \ USAAF in UK
BX332 \ Russia \ 194209 \ 20-Sep-42 \
BX333 \ USAAF in UK
BX334 \ Russia \ 194206 \ 14-Jun-42 \ Lost At Sea
BX335 \ USAAF in UK
BX336 \ Russia \ 194205 \ 17-May-42 \
BX337 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX338 \ Russia \ 194206 \ 24-Jun-42 \
BX339 \ USAAF in UK
BX340 \ Russia \ 194209 \ 10-Sep-42 \ Lost At Sea
BX341 \ Russia \ 194206 \ 15-Jun-42 \ Lost At Sea
BX342 \ Russia \ 194209 \ 10-Sep-42 \
BX343 \ USAAF in UK
BX344 \ USAAF in UK
BX345 \ USAAF in UK
BX346 \ Russia \ 194209 \ 22-Sep-42 \
BX347 \ Russia \ 194206 \ 3-Jun-42 \ Russia <date> crossed out, but Russia rewritten
BX348 \ USAAF in UK
BX349 \ Russia \ 194206 \ 3-Jun-42 \
BX350 \ Russia \ 194206 \ 3-Jun-42 \
BX351 \ Russia \ 194206 \ 24-Jun-42 \
BX352 \ Russia \ 194206 \ 25-Jun-42 \
BX353 \ USAAF in UK
BX354 \ USAAF in UK
BX355 \ Russia \ 194206 \ 3-Jun-42 \
BX356 \ Russia \ 194209 \ 10-Sep-42 \ Lost At Sea
BX357 \ Russia \ 194206 \ 15-Jun-42 \ Lost At Sea
BX358 \ USAAF in UK
BX359 \ Russia \ 194206 \ 24-Jun-42 \
BX360 \ Russia \ 194206 \ 23-Jun-42 \
BX361 \ Russia \ 194206 \ 21-Jun-42 \
BX362 \ Russia \ 194206 \ 3-Jun-42 \
BX363 \ Russia \ 194206 \ 24-Jun-42 \
BX364 \ Russia \ 194209 \ 8-Sep-42 \ Lost At Sea
BX365 to BX370 USAAF in UK

BX370 \ Russia \ 194209 \ 7-Sep-42 \
BX371 \ Russia \ 194209 \ 19-Sep-42 \ Lost At Sea
BX372 \ Russia \ 194209 \ 8-Sep-42 \ Lost At Sea
BX373 to BX378 USAAF in UK

BX379 \ Russia \ 194207 \ 25-Jul-42 \
BX380 \ USAAF in UK
BX381 \ Russia \ 194207 \ 4-Jul-42 \
BX382 \ Russia \ 194206 \ 23-Jun-42 \
BX383 \ USAAF in UK
BX384 \ Russia \ 194206 \ 25-Jun-42 \
BX385 \ USAAF in UK
BX386 \ USAAF in UK
BX387 \ Russia \ 194209 \ 7-Sep-42 \
BX388 to BX393 USAAF in UK

BX394 \ Russia \ 194207 \ 25-Jul-42 \
BX395 \ USAAF in UK
BX396 \ Russia \ 194209 \ 20-Sep-42 \
BX397 to BX402 USAAF in UK

BX403 \ Russia \ 194207 \ 20-Jul-42 \
BX404 \ Russia \ 194209 \ 20-Sep-42 \
BX405 \ USAAF in UK
BX406 \ USAAF in UK
BX407 \ USAAF in UK
BX408 \ Russia \ 194209 \ 7-Sep-42 \
BX409 \ USAAF in UK
BX410 \ Russia \ 194209 \ 11-Sep-42 \ Lost At Sea
BX411 to BX414 USAAF in UK

BX415 \ Britain Category E 12-Oct-42
BX416 \ USAAF in UK
BX417 \ USAAF in UK
BX418 \ USAAF in UK
BX419 \ Russia \ 194209 \ 9-Sep-42 \
BX420 \ Russia \ 194209 \ 9-Sep-42 \
BX421 to BX424 USAAF in UK

BX425 \ Russia \ 194209 \ 22-Sep-42 \
BX426 \ USAAF in UK
BX427 \ Russia \ 194209 \ 8-Sep-42 \ Lost At Sea
BX428 \ USAAF in UK
BX429 \ USAAF in UK
BX430 \ USAAF in UK
BX431 \ Russia \ 194209 \ 10-Sep-42 \
BX432 \ USAAF in UK
BX433 \ USAAF in UK
BX434 \ USAAF in UK
DS173 \ Britain P-39C
DS174 \ Britain P-39C Category E 28-Oct-42
DS175 \ Britain P-39C Category E 7-Jun-42

 

[GregP]

No and quite possibly no.
Allison had trouble making the supercharger drive gears wide enough to handle the load of the 9.60 gears in the space available. I believe the gear case was cast in there rear of the crankcase, They made the auxiliary case deeper to allow for the thicker gears. finding room for the "clutches/planetary gears" and the 2nd gear set might not have been bossible without a substantial change, disrupting production.
Not talked about is the the fact the Merlin production was segregated into factories that made two speed Merlins (both single and two speed) and the home factories that made both.

The problem with the Allison was the actual supercharger, once you stuck a set of 9.60 gears on it it wasn't going to do much better, the tip speed of the impellers was very close to the tip speed of if a Merlin XX supercharger. The Merlin impeller had a 10.5% greater circumference but the Allison impeller was turning 5.6% faster.
You can only turn an impeller so fast before the tips go supersonic inside the supercharger (different conditions than outside air) and the shock waves screw everything up.
They needed a whole new supercharger to really take advantage of a two speed drive.

A two speed drive would have allowed around 1375 -1425hp for take-off (low gear) and kept 1150hp at 15,500ft (high gear) but nobody was asking for that

I read the Air Classics article with great interest. Aside from the first-person content, I realized it was the same author who wrote a similar article about the Northrop P-61 Black Widow that was in the first issue of Air Classics I ever got my hands on, in 1970, at age 10. Evidently Davidson thought it was an amazing fighter in the right hands, and quite counter to a recent article I read (online) from Aviation History, which pretty much dismissed the P-61 as a failure. If anybody is interested, I will upload the P-61 article so you can see Bob's opinions for yourselves (if a PDF can be uploaded on this site).

A couple of things -- how is a 20mm cannon (that works sometimes), two fuselage-mounted (and thus non-converging) .50's, plus four wing-mounted .303's "inferior" to the armament of a Spitfire or Hurricane (I assume he was referring to the eight .303 armament)? Maybe he was thinking of later versions incorporating 20mm cannon which was what they had by 1943?

I was interested in (and enlightened by) the reasons why visibility out of the cockpit was so bad, since at a glance, it looks like a later bubble canopy. This is something I've been thinking about since the unfortunate collision of the P-63 and B-15 in Texas. But how is this different, exactly, than seeing rearwards in a Spitfire, which only had a bit of a bulge in the canopy sides, and from what I've read, was a very tight cockpit as well? Maybe the P-39's framing aside the headrest made it worse than the Spit or Hurricane.

There was also a caption that caught my eye (surely not written by the author): "...this Airacobra had its wings clipped for early postwar racing by Tex Johnston. Giving a fine performance, it still couldn't keep up with its contemporary P-51s and P-38s."

First, I don't believe the wings were clipped on Cobra II (there was a heavily clipped P-61), although it was highly modified for racing. Secondly, um, it won the 1946 Thompson Trophy race. Surely the pilot was important, but he couldn't have done it going slower.

Am interested, definitely. I have heard guys who flew it say that it could out-turn most single -engine fighters. I have some trouble believing that in it's entirety, but it apparently was very maneuverable, never mind the size. One thing is certain, if you inadvertently or otherwise flew into the ammunition stream, you weren't long for this world ... it hit like a ton of bricks when it fired the armament.

 

[Greg Boeser]

I have read memoirs of several pilots who thought it was the hottest ride in town.

 

[GregP]

In the 2-speed, 2-stage Merlin maintenance manual, it says the engine may be switched between low-speed and high-speed by an aneriod or by a manual switch. The manual switch controls a pneumatic valve that changes gears; there is no "neutral." The supercharger is either in low gear or high gear; the only option is whether to manually switch it or set it to automatic gear change.

 

[Joe Broady]

And the author of the Killer Cobra article had used that control before moving on to the P-400, which had no supercharger controls at all, leading him to assert the P-400 did not have a supercharger.

That doesn't say much for his understanding of engines. Surely the P-400 had a manifold pressure gauge. It would have indicated pressures impossible for a naturally aspirated engine.

In many airplanes, part of the drill before engine start was to note the MP reading. During run-up you would adjust the throttle to attain the same MP for some of the checks. But that's only applicable to supercharged engines. A naturally aspirated engine can't attain the static MP after start.

 

[Wild_Bill_Kelso]

Real interesting that they mention the Yo Yo several times. I had been told that WW2 pilots didn't know about this, but it matches what the Soviets seem to have said they did with these ('vertical turns' etc.)

 

[OldGeezer]

This may or may not be helpful, but in reading the Army's Case History Report on the Continental I-1430 experimental engine, an interesting point is made, considering that it was only being developed to power high-performance fighters. During 1943 "a revised XI-1430-9 engine, essentially the same as the I-1430-A, except it had a single stage, single speed supercharger in place of the [original] two-stage, two-speed supercharger, was submitted by Continental in accordance with a request from the Power Plant Section, Wright Field." So even at that late stage, the Army didn't seem to be pushing high-altitude capabilities for what it was developing as its next-generation fighters.

 

[Shortround6]

So even at that late stage, the Army didn't seem to be pushing high-altitude capabilities for what it was developing as its next-generation fighters.

Except that the XI-1430-9 engine was slated to be used in the XP-49 and the XP-67 using a turbocharger and they were planning on getting 1600hp at 25,000ft.

see; https://www.enginehistory.org/References/ModDesig/jpg/I19.jpg

There was a two speed single stage version that was supposed to get to 1600hp at 15,000ft in the XP-53.

The Army and Continental trying to be way cleverer than they should have been. Two speed propeller drives, reversing prop rotation by changing gear box assembly (no new parts) and a few other advanced features. They should have been concentrating on getting the engine to run.