USA produces a Mosquito-like bomber: pros and cons

[davparlr]

Point of Order: even the earliest Mossie bombers did 380 minimum. FB Mossies also replaced Havocs on the Intruder squadrons - the difference in effectiveness speaks for itself, have a look at 418 Squadron, the 23 Sqn ORB is also online. From memory, it took 418 a year and a half to accumulate seven kills with the Havoc, doubled that in just over a month and a half with the Mossie.

Spitfire Performance test show Mk II and IV with a top speed of around 366 mph.

 

[mhuxt]

Not sure what to tell you - all the data cards I've seen for the PR.I and the B.IV give a top speed of 380 or above. Sharp and Bowyer give the same numbers both for the prototypes and early production B.IVs.

Only test I've ever seen with a B.IV top speed less than 380 was on DK290, when +9 lbs boost was used. Those tests were done starting December '42, despite 105 Squadron using +12 to give German fighters the slip from July '42 at the latest. Sharp and Bowyer also have a chart of Merlin power increases with the XX at +12 by mid-1940.

 

[Greyman]

Not quite.

The earliest bomber Mosquitos, the B Mk IV with Merlin 21 engines, managed around 365-370 mph. This was due to the effect of the ducted 'saxophone' exhausts to hide the exhaust flames during night.

When these were ditched in favour of multi ejector stubs, and a few minor other aerodynamic refinements were incorporated, speed went up to about 380 mph when loaded and about 385 mph with stores out.

Keep in mind the 380 figure is with +9 boost.

With +16 boost in 'S' gear a fully loaded Mosquito IV with ejectors would probably go about 390 mph at roughly 14,000 feet.

EDIT: Though I suppose +14/16 boost doesn't help the 'earliest' Mk.IV sorties as described by mxhut.

Not sure what to tell you - all the data cards I've seen for the PR.I and the B.IV give a top speed of 380 or above. Sharp and Bowyer give the same numbers both for the prototypes and early production B.IVs.

Only test I've ever seen with a B.IV top speed less than 380 was on DK290, when +9 lbs boost was used. Those tests were done starting December '42, despite 105 Squadron using +12 to give German fighters the slip from July '42 at the latest. Sharp and Bowyer also have a chart of Merlin power increases with the XX at +12 by mid-1940.

Make sure to check the date on those data cards. They often reflect modification/limitations that took place well after introduction. The original +12 boost wouldn't help the Mosquito's best top speed as it was permitted in 'M' gear only.

 

[mhuxt]

Hmm, might well have to read up on my Merlins then, either that or find earlier data cards...

(Can you recommend a good Merlin book?)

 

[tomo pauk]

Mosquito (actually, a Mosquito-like aircraft) would be operated mostly during the day, so the flame dampers at the exhausts would not be needed. Unless it's a night fighter version, of course.

Any takers on this: how good/bad would've been an DB-7/A-20-based aircraft with Packard Merlin or Allison on-board?

 

[Shortround6]

Depends on what you want it to do, and when.

An A-20 with R-2600 engines picked up about 4,000lbs of weight empty over a DB-7 with R-1830s. Going back to Allisons or Merlins is going to be hard once you have the R-2600 powered planes. Cutting your take-off power by 20-25% isn't going to help take-off, climb out or single engine ceiling much.

I know I have harped on the 22% difference in drag between a P-40 and a P-36 but that is for a single engine plane with the fuselage behind the engine. On a twin engine bomber changing the engines does nothing to change the drag of the fuselage. The engine drag is a much smaller percentage of the total. The early planes (R-1830 powered and some R-2600s) used unprotected integral tanks. Fuel capacity is not always the same in some accounts but 325 gals seems pretty common. You now (using Allisons) have a much bigger, higher drag airplane than a P-38 (without turbos?) with little more internal fuel.
Merlins rather depend on WHICH Merlin but the American single stage Merlin is going to leave you lacking in power for a bomber.

Ranges and bomb loads for the A-20 need careful looking at because ranges are some times given at widely different cruise speeds and different bomb loads.

There is no doubt the Mosquito was faster and longer ranged but the size of the fuselage on the A-20 means that without changing the whole fuselage it doesn't have a prayer of coming close to the Mosquito in speed or range.

 

[tomo pauk]

(data for the DB-7/A-20 I'm using is here)
Well, I was thinking about the C series V-1710 instead of R-1830 (1040 HP for TO and at 13800 ft vs. 1100 for TO and 1000 at 14500 ft). The DB-7 was good for 322 mph at 15300 ft. The lower drag (10%, if I'm reading JtD's data right) and useful exhaust thrust makes another 20-30 mph - call it 350 mph? We don't have any gunners nor guns/ammo now, that should keep the weight in check. Due to faster cruise for same power/consumption, the range should be better, too.
The DB-7 was credited with 462 miles with 2080 lbs of bombs, with 325 gals of fuel. Or 875 miles max range.
Later, the F series V-1710 is available, 1150 for TO and at ~12000 ft, and starting in 1942 the V-1650 (1300 HP for TO) and the improved, 1325 HP for TO V-1710 are available. Should help both to carry more fuel/bombs, along with better overall performance. Especially with 1500-1600 HP once WER is approved (mid/late 1942).

You now (using Allisons) have a much bigger, higher drag airplane than a P-38 (without turbos?) with little more internal fuel.

AHT gives the combat radius of 250 miles for a P-38J/L with two underslung 1600 lbs bombs, 410 gals of fuel. We know that, with tanks attached, the P-51 was ill able to escort Mossies. The late A-20Gs (Boston V, still 1600 HP for TO) were able to carry either 4000 lbs + 390 US gals (wings tanks only; range 690 miles), or 2000 lbs + 726 US gals (wing + bomb bay fuel tank; range 1530 miles). Aircraft data sheet for the Boston V was kindly provided by Neil Stirling some time ago, along with many other bombers ADS.

added: Boston IV is capable for same things as Boston V, according to the ADS provided by Neil

added 2: the Mosquito IV was able to take off with 12 lbs boost (1300 HP) when weighted 21462 lbs (2000 lbs + 643 US gals), with Merlin 21; same TO power was available for the V-1650-1. Take off power of the Merlin 22 and 23 was 1400 HP, with 14 lbs boost (here), enabling a Cookie to be lifted off by the Mk.IV, but with reduced fuel (600 US gals).

 

[Greyman]

Hmm, might well have to read up on my Merlins then, either that or find earlier data cards...

(Can you recommend a good Merlin book?)

I'm a dunce when it comes to engines. My knowledge mostly taps out after the official Pilot's Notes publications.

But, I made a quick estimation graph to show you what's basically happening with the Mosquito IV and the Merlin 21:

Green is +9 boost (full throttle, boost cut-out not pulled) in 'M' and 'S' ratio - the lower portion and upper portion of the curve, respectively.
Brown is +12 boost (cut-out pulled), this was cleared for 'M' ratio only.
Red is +14/+16 boost (cut-out pulled). This was the new engine limitation in late 1942. When the cut out was pulled it allowed +14 boost in the lower 'M' ratio and +16 boost in the upper 'S' ratio.

 

[mhuxt]

Thanks for that - I re-checked all the data cards and pilot's notes I have, they all give the M21 with +14 in M gear and +16 in S for everything that uses the Merlin 21. The pilot's notes say +12lbs was available by pushing back the spring catches on the throttle, which otherwise held the throttles at climbing boost (+9 lbs), but that this +12 was available at sea level only. Greater boost levels (+14 and +16, as above), were available through pulling the boost control cut-out, which was located on the top-left of the instrument panel.

I know for a fact the cut-out was available in early September at the latest, as a weather recce Mosquito was jumped by two 190s at high level - the Mossie got away with it but the pilot was noted to have failed to pull the boost control cut-out, which would have increased his speed below 22,000 feet. That's precisely where DK290's speed peaks, and where it's boost lilne goes "flat" on the test report. Pretty much identical to the W4076 test. The data cards for the Merlin 21 aircraft show a maximum speed at 14k (S gear) at or just above 380 m.p.h.

Do you have a source for me re: boost on the 21?

For the record, I'd like to make abundantly clear that I'm not trying to "pull a Crumpp" and cling desperately to an illusion of my own infallibility despite massive evidence to the contrary. Just trying to learn whatever I can.

 

[Greyman]

Thanks for that - I re-checked all the data cards and pilot's notes I have, they all give the M21 with +14 in M gear and +16 in S for everything that uses the Merlin 21. The pilot's notes say +12lbs was available by pushing back the spring catches on the throttle, which otherwise held the throttles at climbing boost (+9 lbs), but that this +12 was available at sea level only. Greater boost levels (+14 and +16, as above), were available through pulling the boost control cut-out, which was located on the top-left of the instrument panel.

Yep, sounds right ... after late 1942. Before that time the +14/+16 was unavailable.

I know for a fact the cut-out was available in early September at the latest, as a weather recce Mosquito was jumped by two 190s at high level - the Mossie got away with it but the pilot was noted to have failed to pull the boost control cut-out, which would have increased his speed below 22,000 feet. That's precisely where DK290's speed peaks, and where it's boost lilne goes "flat" on the test report. Pretty much identical to the W4076 test. The data cards for the Merlin 21 aircraft show a maximum speed at 14k (S gear) at or just above 380 m.p.h.

I'd be careful with pilot anecdotes. Though it's not likely the pilot remembered using a boost cut-out when none existed, I've often seen them remember the effects of the emergency power incorrectly. A Battle of Britain Hurricane pilot remembering that he 'pulled the tit at 20,000 feet to get extra speed', or something to that effect.

Anything's possible though. Maybe he used the cut out in 'S' ratio when he wasn't supposed to, and it had the desired effect? Not sure. As I said, engines aren't my forte.

Data card speeds agree well with an aircraft fitted with saxophone exhausts.

Do you have a source for me re: boost on the 21?

Quickest ones I could find, via the wwiiaircraftperformance site.

 

[mhuxt]

Thanks for that. Begs the question why A&AEE were testing at +9 from December '42 to April '43 when +16 had been approved in November. Maybe absolute speed itself wasn't the main issue - more the differential 'twixt saxophone and stubs, matt and gloss.

The encounter with the 190s went rather beyond the level of anecdote. I first read about it in Sharp Bowyer's history of the Mossie, turns out the pilot involved also wrote a book, in which the encounter takes up a couple of pages. He chose to evade by doing flick stalls, using open radiator slats as a means to increase nose-up. His combat report went to de Havilland's. Geoffrey de Havilland Jr. himself went up to test it. de H's view was that the forces involved would likely tear the aircraft apart, they recommended closing the rads and pulling the tit, both for speed. A week after the encounter it was published in Tee Em, the RAF pilots' rag, with the recommended course of action.

Still really don't know what to make of timing re: boost and ejectors. The Mossie history has nineteen Mossies on 105 Sqn by the end of September '42, "all with 14 lb. boost." It seems they were doing their own testing in situ, including substituting stubs for saxophones, which took place on DK336 at Marham, the 105 Sqn base, as opposed to Boscombe Down. (DK336 GB-P appears with stubs in a number of the pics taken at the "press day" at Marham, IIRC 5 December '42.)

Tantalisingly, the conclusion is that stubs were good for daylight ops, "as on reconnaissance aircraft". As you know doubt know, the original PR Mossies had the one-piece cowlings, however DK310 force-landed in Switzerland with radiator and engine strife in August had saxophones, and was photographed there (next to a German 109!). The first PR VIII (Merlin 61s) also had stubs in October '42.

Thanks again for the info.

 

[CobberKane]

I wonder if part of the reason the USA never built the Mosquito was a disinclination to adopt another nations designs. As the world's pre-eminent industrial power the US politicians and procurers might have found it a little hard to accept that someone was doing a better job of producing a particular type of aircraft than they were. I seem to recall there was a fair bit of teeth gnashing when the USMC adopted the Hawker Harrier. That said, the US did use Spitfires and Mossies and doubtless a few others I haven't mentioned, so perhaps they never really saw a need for the wooden wonder

 

[Greyman]

Still really don't know what to make of timing re: boost and ejectors. The Mossie history has nineteen Mossies on 105 Sqn by the end of September '42, "all with 14 lb. boost." It seems they were doing their own testing in situ, including substituting stubs for saxophones, which took place on DK336 at Marham, the 105 Sqn base, as opposed to Boscombe Down. (DK336 GB-P appears with stubs in a number of the pics taken at the "press day" at Marham, IIRC 5 December '42.)

I think the best bet would be to research the individual squadron histories and see if/when they report the modifications.

 

[OldSkeptic]

I wonder if part of the reason the USA never built the Mosquito was a disinclination to adopt another nations designs. As the world's pre-eminent industrial power the US politicians and procurers might have found it a little hard to accept that someone was doing a better job of producing a particular type of aircraft than they were. I seem to recall there was a fair bit of teeth gnashing when the USMC adopted the Hawker Harrier. That said, the US did use Spitfires and Mossies and doubtless a few others I haven't mentioned, so perhaps they never really saw a need for the wooden wonder

You have to remember the US was a very different place back then. Yes it was the world largest economy by that time, but in many technological areas it was very far behind. Aerodynamics, engines, superchargers, electronics, weapons, etc, etc, etc. There was a massive technological transfer from the British which bootstrapped their tech areas to a whole new level. if you look at the list of technological transfer they got for basically nothing during the war you cant help but think that Lend Lease was a bargain.

They had a tremendous potential capacity, because of the large motor vehicle, radio, etc industries, but were well behind Europe technologically. Even post war, the US had to use and/or license Rolls Royce jet engines because it couldn't design/make any itself. Basically it did a Jaapan/China thing. Copy and build foreign designs and then later make its own designs.

In many ways and many areas it was still a 2nd World nation, with areas of concentrated (and very large) industries, but many other areas of incredible poverty and, basically, primitiveness. Take one example, the national road system was virtually non-existent, that came later in the Eisenhower era. If you read, for example, Yeager's biography about the standard of living when he was growing up, not that much different from an (say) eastern European peasant of the time.

Makes you wonder though, if WW2 hadn't happened would it have become so dominant?

 

[tomo pauk]

<grabs popcorn>

 

[Aozora]

Not sure what to tell you - all the data cards I've seen for the PR.I and the B.IV give a top speed of 380 or above. Sharp and Bowyer give the same numbers both for the prototypes and early production B.IVs.

Only test I've ever seen with a B.IV top speed less than 380 was on DK290, when +9 lbs boost was used. Those tests were done starting December '42, despite 105 Squadron using +12 to give German fighters the slip from July '42 at the latest. Sharp and Bowyer also have a chart of Merlin power increases with the XX at +12 by mid-1940.

Thanks for that. Begs the question why A&AEE were testing at +9 from December '42 to April '43 when +16 had been approved in November. Maybe absolute speed itself wasn't the main issue - more the differential 'twixt saxophone and stubs, matt and gloss.

Still really don't know what to make of timing re: boost and ejectors. The Mossie history has nineteen Mossies on 105 Sqn by the end of September '42, "all with 14 lb. boost." It seems they were doing their own testing in situ, including substituting stubs for saxophones, which took place on DK336 at Marham, the 105 Sqn base, as opposed to Boscombe Down. (DK336 GB-P appears with stubs in a number of the pics taken at the "press day" at Marham, IIRC 5 December '42.)

Tantalisingly, the conclusion is that stubs were good for daylight ops, "as on reconnaissance aircraft". As you know doubt know, the original PR Mossies had the one-piece cowlings, however DK310 force-landed in Switzerland with radiator and engine strife in August had saxophones, and was photographed there (next to a German 109!). The first PR VIII (Merlin 61s) also had stubs in October '42.

Thanks again for the info.

The A&AEE did test DK290/G at +12 lbs April-May 1943, fitted with de-H multi-fishtail ejector exhausts. The "certain stores" being tested were the Highball bouncing bombs so the top speeds being registered were lower than Mosquitoes with full bomb bay doors http://www.wwiiaircraftperformance.org/mosquito/dk290.pdf

cf the tests done at + 9 lbs boost comparing open vs shrouded exhausts; maximum speeds were 367 mph @ 21,600 ft shrouds vs 380 mph @ 21,900 ejector exhausts: http://www.wwiiaircraftperformance.org/mosquito/dk290-b.pdf

 

[OldSkeptic]

Yes the exhausts made a big difference, especially at altitude.

You look at a Mossie NF 30 with 2 stage Merlins, max (depending on sources) about the 420 mark. But that was with shrouded exhausts. Put in, for a day configuration proper ones and you can add 5-10mph depending on altitude.

 

[OldSkeptic]

<grabs popcorn>

Silly, go back in history and the British were primitive. In the 400s to 1600s it was a primitive little place. Meaningless on the European stage.
EVERY country came from primitive backgrounds, their rises, or falls are usually by luck and/or by the incredible efforts of various individuals/groups against the prevailing elites of the time.
Noting that the elites of any country of the time always, because it suits them, "want to keep thing the same way it was".

And they are even more silly, because things always change.

Better being a 'shockwave rider" (tile of a great book by John Brunner ... get it) rather than a King Canute.

 

[Shortround6]

You have to remember the US was a very different place back then. Yes it was the world largest economy by that time, but in many technological areas it was very far behind. Aerodynamics, engines, superchargers, electronics, weapons, etc, etc, etc.

Bushwa.

Aerodynamics??? P-51, B-29 for starters.
Engines??? P&W and Wright were taking over the world markets for radial engines during the 30s.
Superchargers??? until Hooker showed up everybodies superchargers were crap. British produced how many turbo aircraft?
Electronics??? Yes the British were ahead in some areas.
Weapons??? Gee, I guess I forgot about about the British semi-auto rifle that was standard issue in WW II. The British Semi-auto pistol? The British light machine gun? (designed where?) the Browning machine guns that armed the British planes? Etc,etc, etc.

They had a tremendous potential capacity, because of the large motor vehicle, radio, etc industries, but were well behind Europe technologically.

So behind that Bren carriers were powered by copies of the Ford V-8 car engine? British Motor torpedo boats used Packard engines? Other British launches used Hall-Scott engines? British army used American trucks for heavy hauling?
Please point out these advanced British car and truck engines?

Even post war,the US had to use and/or license Rolls Royce jet engines because it couldn't design/make any itself. Basically it did a Jaapan/China thing. Copy and build foreign designs and then later make its own designs.

Rather ignores the GE J-35 and Westinghouse engines doesn't it?

In many ways and many areas it was still a 2nd World nation, with areas of concentrated (and very large) industries, but many other areas of incredible poverty and, basically, primitiveness. Take one example, the national road system was virtually non-existent, that came later in the Eisenhower era. If you read, for example, Yeager's biography about the standard of living when he was growing up, not that much different from an (say) eastern European peasant of the time.

And just when did the British motorway system come into existence? Pre WWII? I think not.

I also tend to doubt that every Cotswold cottage, Scottish sheep farm or Welsh residence had indoor pluming and electricity in the 1930s either.
Yes there were large areas of poverty in the US in the 1930s ( and some still exist) but in many countries in the 1930s once you got out of the cities, Services tended to go peter out pretty quickly.

The US did have the highest per capita ownership of motor vehicles and radios whicc means that while not every family had one it was much more common than any other country.

The British did many great things in the war and invented/developed a lot of stuff. Claiming the US rode on their coat tails doesn't stand up.

 

[michaelmaltby]

"...Makes you wonder though, if WW2 hadn't happened would it have become so dominant?"

That doesn't stand up either, my Friend.

From the moment the 13 Colonies won their independence from the Crown, the USA was headed for dominance ..... not God-Given dominance ... but nonetheless Manifest Destiny dominance.

All WW2 confirmed was what WW1 had already demonstrated ..... that Europe - aka the rest of the world - was in flux .... leaving an open-wide opportunity for America (industry, finance, military, science, etc) to show what it could do. The world needed an america. And for the most part, the world is a better place for what America has done.

MM
Proud Canadian