# USAAF Attack & Light Bombers: Needs & Desires



## Zipper730 (Apr 22, 2018)

I was thinking about the various attack planes and bomber concepts whipped up during WWII and how they conformed with what we needed and wanted.

I could be missing a few designs here and there, but I remember a few off the bat

USAAF

A-26 Variant(s)
There was one variant which had a redesigned spinner and a jet-engine in the lower rear fuselage for increased speed over target
Another just had the redesigned cowlings

XA-39: Single engine attack/dive-bomber
Crew was a single pilot, no rear-gunner
Powerplant was 1xR-2800
Equipped with 2x37mm+4x0.50 fixed
Top speed listed as 357 mph @ 16,600'
Range: 1400 miles
Could carry 3000-3200 lbs (6 x 500, or 2 x 1600) internally, probably a total of around 4000-4500 lbs total

XF8B-1 Derivative: Single-engine level-bomber
A/C was originally intended for use as a fighter-bomber
Crew was a single pilot
Powerplant was an R-4360 driving a contra-rotating prop (2 x 3-blades)
Could carry up to 6400 lbs of ordinance including 2 x torpedoes; 3200 lbs of ordinance could be carried internally at maximum (2 x 1600 AP).
Top speed was around 450 mph with wartime emergency-power providing it had the same supercharging as the USN layout (2-stage, variable-speed).
Considering the proposal for use as a level bomber, I'm not sure if it was fitted with some kind of bombsight, or merely dropped at low altitudes.
Armament could either come in the form of 6x0.50, or 6x20mm

XA-41: Single-engine attack/dive-bomber
Crew was a single pilot, no rear-gunner
Equipped with 2x37mm and a few 0.50's
Top Speed was 363 mph
Range: 800 miles while carrying 1000 lbs
Could carry 3200 lbs internally, 3200 lbs externally, with a maximum total load ranging from 4000-6000 lbs

XB-42: Twin-engined level-bomber
Crew of 3
Powerplant were 2 x V-3420 driving three-bladed propeller-blades
Could carry up to 8000 lbs bombs normally, up to 10000 lbs (single bomb) if the bay doors were held open 6"
Defensive armament consisted of 2xturrets behind each wing, each with 2x0.50 with 500 rpg.
Armament could include a bombardier nose with 2 x 0.50" also present, as well as nose arrangements that included 8x0.50, 2x37mm+2x0.50, or 1x75mm+2x0.50
Had a defensive armament consisting of twin 0.50 in each wing pointed aft.
Top speed was 410 mph
Range or Radius (I forgot, it's been awhile) was 2500 miles with unspecified load
Notes: Double-Bubble canopy was replaced with single-bubble; to improve safety of bail-out, the propellers were rigged with an explosive charge to blow the blades off; XB-42A featured a pair of J30's under each wing.

XA-43: Twin-engined attack/level-bomber
Crew of at least two
Jet powered: 4 x J35
Payload of 10000 to 12000 lb. if I recall right
Defensive Armament: Remotely controlled tail-turret
Offensive Armament: 6 x 15mm or 6 x 20mm + 4 x rocket-tubes
Radius at 35000 feet: 1000 miles
Radius at 10000 feet: Failed to meat the 600 mile figure
Notes: Was NOT the same as the XP-87; funding was used from the XA-43 to fund the XP-87

I'm probably missing a few designs, I omitted the XA-38 because it was cancelled simply because of engine demand.


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## MIflyer (Apr 26, 2018)

In Europe, when they got the A-26 they found it was just as fast as a P-47 at low altitudes and cold carry a much heavier load of ordnance. They thought it might be possible to replace the P-47 in CAS with the A-26. But when they tried using A -26's on P-47 type fighter bomber missions they found it was a lot larger and therefore easier for the enemy to hit it with ground fire. I think the A-26 ended up being used more or less as a medium bomber, like the B-25 and B-26 and replaced both those airplanes starting at the end of the war. It replaced the A-20 during the war. I recall reading when they brought in the A-26's the A-20 crews deployed at forward bases in Europe were told to fly their A-20's to an airstrip in Scotland, where they stopped, advanced the throttles, jumped out, and let the airplanes run off the end of the runway and over a cliff into the ocean. No wonder we saw so few of those airplanes after the war. 

At least one of the XA-41 aircraft had 4X37MM guns in the wings. It amounted to a USAAF AD Skyraider. It was not adopted because the USAAF found that the XA-41 needed a fighter escort, while P-47's and P-51's equipped with bombs could provide their own escort as well as act as attack aircraft. Of course, as fighters advanced in performance they got further and further away from the needs of the attack mission and in the 60's the the Air Force once again acquired dedicated attack aircraft, ironically starting with the A-1.

The XB-42 used two V-1710 engines driving a V-3420 gearbox. I guess they did that to keep a catastrophic failure of one engine from taking out the whole airplane as might occur with a single V-3420. It was designed for the long range heavy bombardment mission, as a cheaper and faster alternative to the B-29, operated rather like the DH.98. Of course the jet engine doomed it; although they did build a jet powered version that proved to be a nice airplane for testing engines, outrunning jet fighter interceptors was no longer possible. I posted some 1940's vintage articles on it a while back.


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## Zipper730 (Apr 26, 2018)

MIflyer said:


> In Europe, when they got the A-26 they found it was just as fast as a P-47 at low altitudes and cold carry a much heavier load of ordnance.


True, but it was larger and probably less maneuverable when loaded (maximum g-limit) though I could be wrong. I'm curious which costed more, a P-47D & N, or an A-26?


> I think the A-26 ended up being used more or less as a medium bomber, like the B-25 and B-26 and replaced both those airplanes starting at the end of the war.


Basically the B-26 was a medium bomber, the B-25 was originally conceived as a light bomber, then respecified into a medium bomber and classified as such; the A-26 was basically designed for the A-20's mission, though better defended, with a heavier load: It was still classified as a light-bomber because the bomber guys always wanted every new bomber design to be bigger, faster, and further flying.

For heavy bombers, and medium-bombers this sort of made sense, but for the lighter bombers: It seemed to produce designs that were excessively large, and expensive.


> A-20 crews deployed at forward bases in Europe were told to fly their A-20's to an airstrip in Scotland, where they stopped, advanced the throttles, jumped out, and let the airplanes run off the end of the runway and over a cliff into the ocean.


If that's true, it's such a waste. A lot of the metal used in that A/C could be recycled.


> At least one of the XA-41 aircraft had 4X37MM guns in the wings.


I'm curious why they'd use such heavy ammunition -- it didn't have enough firepower to be effective against tanks as far as I know.


> It amounted to a USAAF AD Skyraider.


Not exactly, it was slower, had less range, though an internal bay was a nice touch.


> It was not adopted because the USAAF found that the XA-41 needed a fighter escort, while P-47's and P-51's equipped with bombs could provide their own escort as well as act as attack aircraft.


I'm not sure if that was true, the XA-41 and could turn inside of the P-51B (not sure if the XA-41 was unarmed or loaded). Regardless, the P-47's often flew with top-cover, so they profited from escorts as well.

As for acquiring attack aircraft again, that sort of came out of McNamara, it seems at least...


> The XB-42 used two V-1710 engines driving a V-3420 gearbox.


Actually, I thought it was 2 x V-1710 at first; but I remember being told it was V-3420


> Of course the jet engine doomed it; although they did build a jet powered version that proved to be a nice airplane for testing engines


Actually 2, the XB-42A and the XB-43...


> I posted some 1940's vintage articles on it a while back.


That's cool


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## tomo pauk (Apr 27, 2018)

[QUOTE="Zipper730, post: 1399994, member: 67843"

XB-42: Twin-engined level-bomber
Crew of 3
Powerplant were 2 x V-3420 driving three-bladed propeller-blades
[/QUOTE]

XB-42 was powered by two V-1710 engines.

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## MIflyer (Apr 27, 2018)

See a










ttached

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## Zipper730 (Apr 28, 2018)

MIflyer said:


> See


Regarding the XA-41: Was this combat-range figure based on payload or not? Most sources I got specify a range of 800 miles with 1000 pounds of bombs.

Regarding the XB-42: I have heard some figures for the XB-42 having a having a radius of action of 1800 miles


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## fubar57 (Apr 28, 2018)

I have the XB-43 having a *range *of almost 2,500 miles


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## Zipper730 (Apr 28, 2018)

fubar57 said:


> I have the XB-43 having a *range *of almost 2,500 miles


The XB-43 is a different aircraft than the XB-42, particularly in that it is jet powered.


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## MIflyer (Apr 28, 2018)

First flight of the XA-41 was on 11 Feb 44 at Lomita, CA. That would have to be Lomita Flight Strip, later Torrance airport and now known as Zamperelli Field. I got my pilot's license there in 1982. I am surprised that was the airfield used. It was a training base for P-38's and then P-51's. I guess the XA-41 must have been built near there.


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## Zipper730 (Apr 28, 2018)

While a little off topic, I was curious about something regarding a comparable aircraft to the XA-41: The A-1 Skyraider

According to Joe Baugher's website...

XBT2D-1: Range 1430 -w- 1 x Torpedo
AD-1: Range 1940 -w- 2000 lbs of bombs
This would be combat range right (i.e. 2 x combat radius)?


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## Shortround6 (Apr 28, 2018)

Not quite. If it doesn't say COMBAT RANGE, then it probably isn't. 
Combat radius will include reserves, a combat allowance, and perhaps a few other things (like climb to operational altitude)

"Range" unless it specifically says so, does not include any of those things. 

For instance see:
http://www.alternatewars.com/SAC/XBT2D-1_ACP_-_10_August_1944.pdf

Please note Joe Baugher is not listing the conditions of that range, like gross weight and if drop tank/s are being used while carrying bomb/torpedo load.


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## MIflyer (Apr 28, 2018)

The XB-42 was envisioned by Douglas as an alternative to the B-29 for the Marshall Is to Japan mission, although using more aircraft flying at a somewhat higher speed. The Aviation article says it has a 5000 mile range, so that sounds about right. I have already posted the B-42 design analysis that provides more data.







Note that the XA-41 uses an R-4360 rather than the AD's R-3350..

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## Zipper730 (Apr 28, 2018)

Shortround6 said:


> Not quite. If it doesn't say COMBAT RANGE, then it probably isn't.


I also think Joe Baugher miswrote the 1940 mile figure, because none of the other designs are that high up. I think he meant "1490" and got 4 & 9 backwards.


> Combat radius will include reserves, a combat allowance, and perhaps a few other things (like climb to operational altitude)


The listed figures on the chart you gave me seems to indicate that combat range is 80% of normal range, so combat radius is 40% of the range.



MIflyer said:


> The XB-42 was envisioned by Douglas as an alternative to the B-29 for the Marshall Is to Japan mission


I thought the specification was to do what the Mosquito could do, or faster, with twice the load and self-defending armament? So the idea was actually an alternative to the B-29 that could do what I basically wrote? Why was it classified as a light and not a medium bomber with an 8,000 pound bomb load?


> The Aviation article says it has a 5000 mile range, so that sounds about right.


If the combat radius of a bomber is 0.4 that of the range that would yield a range of 2000 miles...


> Note that the XA-41 uses an R-4360 rather than the AD's R-3350..


I'm aware of that, how do the SFC figures compare? From what I remember, the R-3350's used on the AD-1 used a twin-speed supercharger?


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## Graeme (Apr 29, 2018)

Zipper730 said:


> I also think Joe Baugher miswrote the 1940 mile figure, because none of the other designs are that high up. I think he meant "1490" and got 4 & 9 backwards.



No, Baugher hasn't got it wrong - look at his bibliography - he's using Wagner....


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## MIflyer (Apr 29, 2018)

Check out the cruising speed on the AD versus that on the XA-41.


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## Zipper730 (Apr 30, 2018)

MIflyer said:


> Check out the cruising speed on the AD versus that on the XA-41.


The XA-41's listed cruise is 294 mph; the AD-1 has a listed indicated airspeed of 185 mph which would at 15000 come out to 233 mph and, with 164 mph as one of the SAC sheets listed, would come out to 207 mph. With ingress altitude listed at 15000 and egress at 5000 feet: You would see speeds that would be around 177-199 mph

Sea level maximum for the AD-1 is 357 mph, and 333 mph for the XA-41

*Edited 5/2/21: Really botched the IAS/TAS conversion.*


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## MIflyer (Apr 30, 2018)

I would assume that performance figures would use true air speed, not IAS.

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## Zipper730 (Apr 30, 2018)

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## MIflyer (Apr 30, 2018)

Well an airplane can "cruise" at just about any speed, from just above stalling to full power. I would guess that the XA-41 speed given is maximum cruising speed while the AD speed given is economy cruise. 

I just read where in WWII a Mossie night fighter was caught in a massive thunderstorm and could not climb. Finally the radar op yelled at the pilot, "Go through the gate with the throttles so we can climb. We can't go any lower! We don't even know where we are!" The pilot replied, "I did that ten minutes ago and we still can't climb!"


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## Zipper730 (Apr 30, 2018)

MIflyer said:


> Well an airplane can "cruise" at just about any speed, from just above stalling to full power. I would guess that the XA-41 speed given is maximum cruising speed while the AD speed given is economy cruise.


Apparently the XA-41 had a three-speed single-stage supercharger, I'm not sure why you'd gear the high-speed setting for around 15,000 feet.


> I just read where in WWII a Mossie night fighter was caught in a massive thunderstorm and could not climb.


Ice on the wings?


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## Shortround6 (Apr 30, 2018)

It used a variable speed drive. The "high" altitude gearing for single stage supercharger was often around 15,000ft, give or take. Gear ratio was 7.52 max. 

Please note that the boeing XF8B-1 used a two stage supercharger but the engine weighed about 350lbs more, this includes the contra rotating prop gear box. You pick your intended altitude band and get an engine with supercharger to suit. 






Big intercoolers need lots of air.


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## wuzak (Apr 30, 2018)

Zipper730 said:


> Apparently the XA-41 had a three-speed single-stage supercharger, I'm not sure why you'd gear the high-speed setting for around 15,000 feet.



I don't know about the XA-41's engine specifically, but Pratt and Whitney superchargers often had high and low gears, plus neutral, for the auxiliary compressor.


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## Zipper730 (Apr 30, 2018)

Shortround6 said:


> It used a variable speed drive. The "high" altitude gearing for single stage supercharger was often around 15,000ft, give or take.


Understood, though in my personal opinion, it would have probably been best to have pushed it up to at least 24,000-25,000 feet based on the need to deal with improvements in enemy fighter aircraft.


> Gear ratio was 7.52 max


What was the minimum for the design?


> You pick your intended altitude band and get an engine with supercharger to suit.


True, but I figure the fighters that were doing this mission were largely able to fly faster because of their higher altitude capability (with jets this would become more extreme), so designing this plane to go up a bit higher would compensate for the nature of changing air-defenses would probably be fairly smart. 


> Please note that the boeing XF8B-1 used a two stage supercharger but the engine weighed about 350lbs more, this includes the contra rotating prop gear box.


All that only added 350 pounds?


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## wuzak (Apr 30, 2018)

Zipper730 said:


> Understood, though in my personal opinion, it would have probably been best to have pushed it up to at least 24,000-25,000 feet based on the need to deal with improvements in enemy fighter aircraft.



I think it was more of a limitation of the supercharger design than the desired altitude.


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## Zipper730 (May 23, 2018)

wuzak said:


> I think it was more of a limitation of the supercharger design than the desired altitude.


If I recall right, the F7F Tigercat could do around 24000 feet with a single-stage supercharger


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## Shortround6 (May 23, 2018)

Zipper730 said:


> If I recall right, the F7F Tigercat could do around 24000 feet with a single-stage supercharger


 Please be more specific.
F7Fs did not all use the same engine. 

However the F7F-1 & -2 used R-2800-22W engines , these were single stage "C" series engines and were good for 1600hp at 16,000ft in high gear, _*no ram*_. 
With RAM the critical altitude goes a somewhat higher and the Navy arranged for water injection to be used at any altitude. This helped at the higher altitudes but nowhere near what it did at heights below the critical altitude. 

The F7F-3 used the R-2800-34W engine and these were capable of 1700hp at 16,000ft dry without RAM. The -34 engine used a new diffuser and had better high altitude performance than the -22 engine, but that still meant critical altitude with no RAM was below 20,000ft. 

These are pretty much post war engines. Please note both engine were good for 2100hp at low altitude in low gear.


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## Zipper730 (May 24, 2018)

Shortround6 said:


> Please be more specific.


What I was trying to point out was that with ram, the critical altitude of the F7F was around 24,000 feet. The point is that even with a properly designed single-stage, twin-speed supercharger, and a good intake, one should be theoretically able to achieve 24,000 feet.

As for the XA-41, with a variable speed set-up it seems easier to do...


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## Shortround6 (May 24, 2018)

The critical altitude, even with ram, was under 24,000ft. Nobody picked up 8,000ft of altitude with RAM. 
P & W says the -34W engine had a critical altitude of 16,000ft in high gear, US Navy says 16,600ft, performance charts show max speed of a F7F-3 was at 23,000ft using military power. 

The -22W engine gave the F7F-2 max speed at about 22,500ft in Military power and using WEP it was a bit over 20,000ft. At 20,000ft the F7F-2 was about 20mph faster than using military power but at about 22,500 and up the difference was about 10mph. The WEP required water injection.


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## Zipper730 (May 26, 2018)

Shortround6 said:


> The critical altitude, even with ram, was under 24,000ft. Nobody picked up 8,000ft of altitude with RAM.
> P & W says the -34W engine had a critical altitude of 16,000ft in high gear, US Navy says 16,600ft, performance charts show max speed of a F7F-3 was at 23,000ft using military power.
> 
> The -22W engine gave the F7F-2 max speed at about 22,500ft in Military power and using WEP it was a bit over 20,000ft. At 20,000ft the F7F-2 was about 20mph faster than using military power but at about 22,500 and up the difference was about 10mph. The WEP required water injection.


Thanks for the correction in figures

I'm curious if you know how the performance would compare with a variable-speed supercharger with good ram?


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## Shortround6 (May 26, 2018)

Zipper730 said:


> Thanks for the correction in figures
> 
> I'm curious if you know how the performance would compare with a variable-speed supercharger with good ram?


You have two components to the supercharger, the supercharger itself which is just an air compressor. and the drive system, which can be simple, a single fixed gear ratio. or complicated as in multiple gear ratios (although more than 2 almost never saw service) or hydraulic/variable drive.

P & W didn't seem to use the variable speed drives with the same compressors (or indeed on the same engines ) as they used with the single speed, two speed and even the two stage engines so it gets very difficult to say. 
The R-2800-22/W engine used a two speed drive and the gears were 7.29 and 9.45. The -30W used a variable speed drive with 7.29 being the lowest speed and 10.55 being the high limit. However the -30 wasn't a "C" series engine, it was an "E" series and further complicating things it used a new supercharger and a new carburetor. It also weighed 200lbs more than the -22W. 
There were only two "E" series engines built. The -30W used in the F8F-2 and the -32W used in the F4U-5 which used a variable speed drive to the TWO impellers running in parallel in the first stage of the two stage system. 
The New Supercharger gave the -30W a considerable increase in altitude performance, much more than can be attributed to just the change in impeller speed due to the different top limits. The supercharger on the -32W engine is quite possibly the most sophisticated mechanical drive supercharger used on a piston engine fighter in squadron service.


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## Zipper730 (May 30, 2018)

Shortround6 said:


> You have two components to the supercharger, the supercharger itself which is just an air compressor and the drive system, which can be simple, a single fixed gear ratio. or complicated as in multiple gear ratios (although more than 2 almost never saw service) or hydraulic/variable drive.


What gear-ratios do variable-speeds usually work along?


> P & W didn't seem to use the variable speed drives with the same compressors (or indeed on the same engines ) as they used with the single speed, two speed and even the two stage engines


Why?


> The R-2800-22/W engine used a two speed drive and the gears were 7.29 and 9.45.


Ratio difference is 2.16


> The -30W used a variable speed drive with 7.29 being the lowest speed and 10.55 being the high limit.


Ratio difference is 3.26


> the -30 wasn't a "C" series engine, it was an "E" series


Which seemed to be available in 1945 at best?


> The supercharger on the -32W engine is quite possibly the most sophisticated mechanical drive supercharger used on a piston engine fighter in squadron service.


Is there any advantage in having two impellers working in parallel than in seres?


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## swampyankee (May 31, 2018)

Zipper730 said:


> What gear-ratios do variable-speeds usually work along?
> Why?
> Ratio difference is 2.16
> Ratio difference is 3.26
> ...



The advantages may be related to packaging and gearing; there are disadvantages, in greater parts count and possibly lower achievable efficiency; dynamic compressors tend to be less efficient as size decreases.


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## Shortround6 (May 31, 2018)

I would note that the centrifugal compressors tend to both flow air and require power to drive in relation to the _square _of the tip speed.
So the Change from 7.29 to to 9.45 is more like the change from 53 to 89 or about 68% more airflow and 68% more power required to drive the supercharger. 
Please note that most of these compressors operated in the 70% range for efficiency with the extra 25-30% of the power driving going directly into heating the air over and above the heat generated by the simple compression of the air. 
This may be one reason they didn't shift to the high gear ratio of the variable speed drive until they redesigned the supercharger itself. This is supposition on my part. The variable speed drive was used an a different base model of engine and a different compressor design. I think they changed the diffuser but I am not sure and have no other details on what else may or may not have been changed. This makes it very hard to draw comparisons or to say "they should have done......." sooner. 
Using an intake charge (air and fuel) 100-200 degrees hotter in high gear than in low gear can really push you closer to detonation limits and put an extra load on the engine cooling requirements.


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## Zipper730 (May 31, 2018)

swampyankee said:


> The advantages may be related to packaging and gearing


When you say packaging, do you mean volumetrics? As for the gearing, it would be simpler in layout?


> there are disadvantages, in greater parts count and possibly lower achievable efficiency; dynamic compressors tend to be less efficient as size decreases.


The greater parts count, I get.



Shortround6 said:


> I would note that the centrifugal compressors tend to both flow air and require power to drive in relation to the _square _of the tip speed.
> So the Change from 7.29 to to 9.45 is more like the change from 53 to 89 or about 68% more airflow and 68% more power required to drive the supercharger.


I follow...


> Please note that most of these compressors operated in the 70% range for efficiency with the extra 25-30% of the power driving going directly into heating the air over and above the heat generated by the simple compression of the air
> 
> . . .
> 
> This may be one reason they didn't shift to the high gear ratio of the variable speed drive until they redesigned the supercharger itself.


Which had to do with the shape of the compressor and the diffuser? What's the diffuser do exactly?


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## fubar57 (May 31, 2018)

Internet...."A diffuser -- a set of stationary vanes that surround the impeller -- converts the high-speed, low-pressure air to low-speed, high-pressure air. Air molecules slow down when they hit the vanes, which reduces the velocity of the airflow and increases pressure."

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## Zipper730 (Jun 2, 2018)

fubar57 said:


> "A diffuser -- a set of stationary vanes that surround the impeller -- converts the high-speed, low-pressure air to low-speed, high-pressure air. Air molecules slow down when they hit the vanes, which reduces the velocity of the airflow and increases pressure."


So basically, the redesigned diffuser was able to better increase the pressure without increasing temperature?


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## swampyankee (Jun 2, 2018)

Zipper730 said:


> So basically, the redesigned diffuser was able to better increase the pressure without increasing temperature?



Kind of.

The impeller increases the velocity of the air; the diffuser slows it down and increases pressure. See this site for some more detail.

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## Zipper730 (Jun 4, 2018)

Done, though I personally prefer the image on page 1




I know exactly what the function is... I'm kind of a person who has to see things


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## wuzak (Jun 4, 2018)

Zipper730 said:


> Ratio difference is 2.16
> Ratio difference is 3.26



What would we do without you Zipper?


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## wuzak (Jun 4, 2018)

fubar57 said:


> Internet...."A diffuser -- a set of stationary vanes that surround the impeller -- converts the high-speed, low-pressure air to low-speed, high-pressure air. Air molecules slow down when they hit the vanes, which reduces the velocity of the airflow and increases pressure."



The vanes are there for guiding the air. 

The diffuser is the expansion of volume.



> A diffuser is "a device for reducing the velocity and increasing the static pressure of a fluid passing through a system”. Diffusers are used to slow the fluid's velocity while increasing its static pressure. The fluid's static pressure rise as it passes though a duct is commonly referred to as pressure recovery. In contrast, a nozzle is often intended to increase the discharge velocity and lower pressure while directing the flow in one particular direction.





> A typical, subsonic diffuser is a duct that increases in size in the direction of flow. As the duct increases in size, fluid velocity decreases, and static pressure rises. Both mass flow rate and Bernoulli's principle are responsible for these changes in pressure, and velocity.



Diffuser (thermodynamics) - Wikipedia


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## Zipper730 (Jun 5, 2018)

MIflyer said:


> See a
> View attachment 491273


Okay, I did some looking in a book I recently got: "Convair Advanced Designs II: Secret Fighters, Attack Aircraft and Unique Concepts, 1929-1973", and the entry on the XA-41 basically lists an early armament consisting of the following

Payload
Maximum Internal
1,000 lbs (4 x 250)

Maximum External
5,500 lbs

Maximum Total: 6400 lbs
Typical Load: 3200 lbs
Internal: 1,000 lbs
External: 2,200 lbs


Armament
2 x 37mm M-9
4 x 0.50 caliber

Performance
Range
800 miles with 1,000 pounds
3000 miles with external tanks (and possibly a bomb-bay filled with fuel)

Speed
Maximum: 363 mph @ 15,500 feet


The original design was based on an inverted gull-wing for weight reduction, and after this produced directional and lateral stability, it was replaced with a tapered wing with dihedral in the outer panels. It was evaluated on 4/29/43, and specifications were modified for low level ground attack rather than dive-bomber, which resulted in the removal of dive brakes, bomb-displacing gear, change to load-factor (no idea how much), and reduced load by 1,600 pounds.

If I read the cost figures right, it was $110,000 a plane.

The design was not really liked because it's speed and altitude didn't give it the ability to defend itself (I'm not sure how good the A-26 did in that department, though they were working on improvements with redesigned cowls and a jet engine in the back), which may or may not be pre-textual. On 10/22/43, they decided they would eliminate the requirement for single-engined, single-place ground attack planes: I'm not sure if the rationality of this was the performance or the fact that they just preferred twins.


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## Zipper730 (Jul 4, 2018)

Shortround6 and wuzak: Do you have any idea what the typical maximum gear-ratios were for variable speed superchargers?


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## Shortround6 (Jul 4, 2018)

Somewhere between 10.0 and 11.0 to 1.

Please remember that the actual physical speed limit is the tip speed of the impeller. Once the tip speed goes supersonic the resulting shock waves inside the supercharger disrupt the air flow. While due to the pressure/temperature inside the supercharger compared to free air the speed of sound it higher there is still a limit.


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## Zipper730 (Jul 4, 2018)

Deleted


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## Zipper730 (Jul 15, 2018)

Shortround6 said:


> Somewhere between 10.0 and 11.0 to 1


What's the maximum spread between minimum and maximum?


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## Shortround6 (Jul 15, 2018)

Zipper730 said:


> And the minimum gear-ratio is around 4-8 less right with a variable speed in theory right?


I believe the DB engines on the 109 had a low speed of just over 7 to 1. 

The R-2800 in the F8F-2 had a minimum of 7.29 and max of 10.55

The R-2800 in the F4U-5 may have used a min of 6.70 and a max of 9.66.


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## Zipper730 (Jul 15, 2018)

Shortround6 said:


> I believe the DB engines on the 109 had a low speed of just over 7 to 1.


And the maximum was like 10.3?


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## Zipper730 (Jul 19, 2018)

I'm curious if it would have been possible to have developed any piston-powered, single-engined tactical bomber with the ability to do at least one of the following things?

Radius of action: 800 miles with 1,000 pounds of bombs
Radius of action: 575-775 with 2,000 pounds of bombs
Radius of action: 500-550 with 3,000 pounds of bombs
Maximum level speed of at least 395-405 mph at critical altitude, presumably between 15,000 - 25,000 feet


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## Shortround6 (Jul 20, 2018)

Zipper730 said:


> I'm curious if it would have been possible to have developed any piston-powered, single-engined tactical bomber with the ability to do any of the following things
> 
> Radius of action: 800 miles with 1,000 pounds of bombs
> Radius of action: 575-775 with 2,000 pounds of bombs
> ...


When?
1943 or 1945 or 1949?

But I would say it would be pretty hard. An AU-1 Corsair can only do about 388mph clean (with empty pylons and rocket launchers) at 14,000ft with a post war R-2800 running on 115/145 fuel (engine making 2270hp at 11,000ft ). 
Combat radius of 380 NM (437 statute miles) with a single 1000lb, six 500lb bombs and two 150 gal drop tanks. average cruising speed 190mph. 

You left out desired cruise speed and cruise altitudes for your desired wish list. The AU-1 was cruising to target at 15,000ft and returning at 5,000ft.

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## swampyankee (Jul 20, 2018)

Zipper730 said:


> I'm curious if it would have been possible to have developed any piston-powered, single-engined tactical bomber with the ability to do any of the following things
> 
> Radius of action: 800 miles with 1,000 pounds of bombs
> Radius of action: 575-775 with 2,000 pounds of bombs
> ...



I suspect it’s not possible with pistons. Probably, an internal bomb bay would also be needed.


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## Zipper730 (Jul 20, 2018)

Shortround6 said:


> When? 1943 or 1945 or 1949?


First flight around 1944 based on the XA-41's first flight.


> But I would say it would be pretty hard.


I'm not sure if the top-speed figures for attack/bomber aircraft are based on them flying clean or with a bomb-load of some sort.

I actually know very little about the AU-1 other than it was an F4U variant, and had a different supercharger: I didn't know 388 could be achieved at only 14,000 feet but that sounds pretty impressive. Are the cruising speed figures indicated or true airspeed?


> You left out desired cruise speed and cruise altitudes for your desired wish list.


As for cruising speed I'd say somewhere from 240-250 mph, as for cruise altitudes

From what I remember with altitudes

The A-1 would cruise to target at 15,000 feet and return at 5,000 feet
The P-47N would cruise to target at 10,000 feet and return around sea-level
I assume the A-1 would dive from 15,000 feet down as low as they dare, release the bombs; then climb back up to 5,000 feet on the ride back home right? I'm curious honestly as to the merits of cruising at 20,000-25,000 feet versus 10,000-15,000 and exiting at 10,000-15,000 feet versus 5,000 feet or sea-level? It seems like it would make for superior range and allow a higher cruise-in speed.



swampyankee said:


> I suspect it’s not possible with pistons.


I wouldn't be shocked.


> Probably, an internal bomb bay would also be needed.


That kind of goes without saying. Using the XA-41 as a starting point, it's internal bay could carry 4 x 250 pound bombs. I'm curious if the dimensions would also allow 1 x 1600 AP as well. I figure the rest would be carried on external pylons with at least one hard-point on each wing plumbed for a drop-tank if need be.


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## swampyankee (Jul 20, 2018)

Generally, best range is not strongly affected by altitude for piston-engined aircraft.


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## Zipper730 (Jul 20, 2018)

swampyankee said:


> Generally, best range is not strongly affected by altitude for piston-engined aircraft.


I figured it would because the air gets thinner and it makes it easier to chop through the thinner air allowing higher speeds for the same amount of power, or less power for the same speed.


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## Shortround6 (Jul 20, 2018)

Actually range does go up with altitude for Piston powered planes. Otherwise there were be no market for Turbocharged/pressurized Cessna's and Beechcrafts 

However it almost always involves more complicated engine set ups with higher maintenance regardless if you have a flat six or a radial 28 cylinder. Dag at 20,000ft is only a little of 1/2 the drag at sea level so if you can keep sea level power or close to it at 20,000ft you get much more range.

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## swampyankee (Jul 20, 2018)

Shortround6 said:


> Actually range does go up with altitude for Piston powered planes. Otherwise there were be no market for Turbocharged/pressurized Cessna's and Beechcrafts
> 
> However it almost always involves more complicated engine set ups with higher maintenance regardless if you have a flat six or a radial 28 cylinder. Dag at 20,000ft is only a little of 1/2 the drag at sea level so if you can keep sea level power or close to it at 20,000ft you get much more range.



There are advantages to flying higher, one being that there tend to be fewer clouds stuffed with rocks at 20,000 ft than at 5,000. Another is that the ground speed for best range increases with altitude. I don't know how an air force chooses the airspeed / range combination, but I suspect that for aircraft which are not dominated by either maneuver or runway demands, the designer will try to get that airspeed as close to that for best productivity, which is VL/D.


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## Zipper730 (Jul 22, 2018)

Shortround6 said:


> Please be more specific.


F7F-1, R-2800-22W


> However the F7F-1 & -2 used R-2800-22W engines , these were single stage "C" series engines and were good for 1600hp at 16,000ft in high gear, _*no ram*_. . . . Nobody picked up 8,000ft of altitude with RAM.


According to this source, which I have found to be highly reliable...










_Images courtesy: WWII Aircraft Performance_

... figures clearly show a critical altitude of 24,000 feet on normal power, and 23,400 on military power settings.

*Addendum: It would appear that some of the charts on the F7F-1 indicate different critical altitudes, most of which match yours. It is my suspicion that they might very well have re-geared the supercharger for one reason or another. One possible reason could be to increase maximum speed at critical altitude, and sea-level. Oddly climb-rate was decreased on these.*


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## Zipper730 (Jul 25, 2018)

While, this is a slight detour from topic, it still regards bomber and attack aircraft...



MIflyer said:


> The XB-42 . . . was designed for the long range heavy bombardment mission, as a cheaper and faster alternative to the B-29


To avoid any ambiguity, was the XB-42 classified at any point as a medium-bomber, or was it always considered a light-bomber?


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## Zipper730 (Oct 29, 2020)

Graeme said:


> No, Baugher hasn't got it wrong - look at his bibliography - he's using Wagner....


Why the discrepancy in Wagner's figures and others?


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## Zipper730 (Jun 13, 2021)

C
 CORSNING

S
 Shortround6

T
 ThomasP


I was thinking of something about a WWII-era design achieving a combination of high speed and good range with one engine and I was thinking about the power output of the R-4360 (3400 hp with WEP, 3000 hp with military rated power, and 2550-2700 hp with normal rated power).

That power output is about twice the output of some RR Merlin variants, and that got me thinking of the De Havilland Mosquito with the RR Merlins removed and an R-4360 put up front (and this is, of course, grossly over-simplified): While the Mosquito isn't capable of the normal-rated g-loads demanded by either the USAAF (8-9) or USN (7-8), I figure something with the strength of the Tempest scaled-up to the Mosquito's size with a R-4360 could probably deliver some remarkable performance in terms of both speed and range.


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## Shortround6 (Jun 13, 2021)

And fuel consumption. 






*Empty weight:* 13,519 lb (6,132 kg)
*Gross weight:* 20,508 lb (9,302 kg)
*Max takeoff weight:* 21,691 lb (9,839 kg)
Internal bomb bay was not as big as Mosquitos.


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## pbehn (Jun 13, 2021)

Zipper730 said:


> C
> CORSNING
> 
> S
> ...


The success of the Mosquito as a design was its high speed, two man crew and useful but not huge internal load capacity. Depending on use it could have huge range, or good range with bombs or cannon and all sorts of combinations. It was never developed to the fullest of any performance because fitting Griffons would improve some parts of performance and lose on others, because the Griffon is heavier and uses more fuel. By the end of its life the Merlin was producing 2,000HP so two would be 4,000HP and the Griffon was circa 2,500HP so 5,000 in an uprated Griffon Mosquito. The thing is, whether you use one or two engines or four engines to produce 5,000 HP you still consume similar amounts of fuel, so you have to put fuel somewhere.

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## ThomasP (Jun 13, 2021)

Hey Zipper730,

The only maybe I can think of is a late-war Sabre powered single-engine detail improved kinda-Mosquito (wood or metal). By the late-war the Sabre was reliably putting out around 2x the power of the mid-war Merlin (non-WEP in both types). 1x Sabre installation would incur more drag than 1x Merlin, but less drag than 2x Merlin. And since you could get rid of the drag producing engine nacelles, you would be able to significantly reduce drag even further. Or maybe redesign the nacelles for landing gear only, in a more streamlined form? If IIRC the very late Sabre's sustained (Normal) power was 2x the Merlin sustained (normal). I do not know what could have been done relative to the development of higher altitude rated models, in terms of practicality. The immediate post-war Sabre model being worked on was putting out 3500 BHP with WEP and water injection.

As has been mentioned up-thread, there were other engines with similar power output, but all of them would have had significantly higher drag installations (I think). Also the Sabre installation should have greater fuel efficiency than the other similar power engines (I think) - although as SR6 and pbehn pointed out above, higher power incurs higher fuel usage in similar proportion.


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## Zipper730 (Jun 14, 2021)

C
 CORSNING
, 
P
 pbehn
, 
S
 Shortround6
, 
T
 ThomasP


I want to make sure that everybody understands that I'm not literally saying that the idea I was thinking of was exactly a De Havilland Mosquito with an R-4360 in the nose: It was merely the basic idea from which everything else would come out of. After all the aircraft has a number of redeeming qualities from an aerodynamic standpoint.

1. The wing-cross section and overall planform was very efficient and played a role in the aircraft able to achieve it's high speeds. It's maximum mach number also seemed to be pretty good too, though I'd have to check that out. By the time the universal wing was adopted, the stations used to mount drop-tanks and bombs seemed to do a pretty good job of blending in the tank or the bomb with the wing.​​2. The aircraft had a decent overall internal volume which makes it possible to store a considerable amount of fuel internally, and carry a decent internal load (typically 4 x 500 pound bombs), while still achieving a respectable range in the process.​
The most basic changes would be that

1. It would be constructed out of metal instead of wood: This might actually free up more internal volume, but weight would probably be the same for the same g-load.​​2. The R-4360 would eliminate the need for radiators: Oil coolers would need to remain, and they'd probably remain in basically the same place as before. To maximize performance, I figure you'd need a tight cowl with as much a bell-mouthed shape as possible.​​3. The aircraft would only have a single crew: The canopy could be made smaller, and that would improve aerodynamics. There'd also be a weight reduction of around 200 pounds.​​


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## Zipper730 (Jul 10, 2021)

M
 MIflyer
,

Two issues, the first is the A-26: From what you said, it was felt to be about as fast at low altitude as the P-47, but nobody realized it's larger size would make it easier to hit. I assume this was before it entered operational service?

The second is the 37mm M9 cannon: While I remember hearing the length was 104" and weighed 405 pounds, was there any figures for the width and height of the gun? This has to do with the XA-41's design as it had really thick wings.


S
 Shortround6
, given that you seem to be the resident gun expert, I figured I should tag you on this one.


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## MIflyer (Jul 10, 2021)

They found out about the speed and vulnerability of the A-26 when they actually introduced it into service in the ETO. They mainly switched A-20 units over to the A-26, the A-20's being flown to Scotland and run off a cliff, but I read of one B-26 unit going over to A-26 as well. I think they retained one of their B-26's for use as a transport.


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## Zipper730 (Jul 10, 2021)

MIflyer said:


> They found out about the speed and vulnerability of the A-26 when they actually introduced it into service in the ETO.


So, it was kind of a retroactive detail they learned after the fact? I'm surprised nobody noticed this issue with the A-20's (they were used in the ETO right)


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## MIflyer (Jul 11, 2021)

A-20's were not used as CAS, as far as I know. They were used on more medium bomber style missions in the ETO.


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## Zipper730 (Jul 11, 2021)

MIflyer said:


> A-20's were not used as CAS, as far as I know. They were used on more medium bomber style missions in the ETO.


So, the A-26's were to be used for CAS & Interdiction?


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## MIflyer (Jul 11, 2021)

I think that by then the USAAF's concept for light and medium bombers had changed. They cancelled the high altitude B-28 medium and in the Pacific the B-25 and A-20 had proved to be mainly valuable for low altitude attacks. In contrast the mediums seemed to have done almost no strafing in the ETO; many of the B-26's had four a package guns aside the nose and almost never used them - and the nose gun for the bombardier could not be used without first removing the Norden bomb sight. The A-26 was supposed to replace the A-20, B-25, and B-26, and with its interchangable noses could be configured either for level bombing or low altitude attack.

The concept they came up for the A-26 apparently was it would be used like a fighter bomber with a much greater load of ordnance, and then they found out it was so much bigger it was easy for ground fire to hit. I think the A/B-26s in Korea were used mainly at night and I have not read of them being used for CAS. I was told they fired 5 inch HVAR rockets at night, too. 

I read of one Douglas B-26 in Korea chasing a N Korean PO-2 down a river bed, the bombardier yelling directions to the pilot, since he did not have a gun sight that was effective at night and thus they had to make an "X" with the nose while firing the wing guns in hope of hitting the target. Later the pilot of that same 26 decided to sneak up behind about 50 Yak-9's in daylight and pick a few off, which sounded like a really dumb idea to the bombardier (and I tend to agree with him). The Yaks spotted them before they could fire and scattered wildly.


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## Zipper730 (Jul 12, 2021)

MIflyer said:


> I think that by then the USAAF's concept for light and medium bombers had changed. They cancelled the high altitude B-28 medium and in the Pacific the B-25 and A-20 had proved to be mainly valuable for low altitude attacks. In contrast the mediums seemed to have done almost no strafing in the ETO; many of the B-26's had four a package guns aside the nose and almost never used them - and the nose gun for the bombardier could not be used without first removing the Norden bomb sight. The A-26 was supposed to replace the A-20, B-25, and B-26, and with its interchangable noses could be configured either for level bombing or low altitude attack.
> 
> The concept they came up for the A-26 apparently was it would be used like a fighter bomber with a much greater load of ordnance, and then they found out it was so much bigger it was easy for ground fire to hit. I think the A/B-26s in Korea were used mainly at night and I have not read of them being used for CAS. I was told they fired 5 inch HVAR rockets at night, too.
> 
> I read of one Douglas B-26 in Korea chasing a N Korean PO-2 down a river bed, the bombardier yelling directions to the pilot, since he did not have a gun sight that was effective at night and thus they had to make an "X" with the nose while firing the wing guns in hope of hitting the target. Later the pilot of that same 26 decided to sneak up behind about 50 Yak-9's in daylight and pick a few off, which sounded like a really dumb idea to the bombardier (and I tend to agree with him). The Yaks spotted them before they could fire and scattered wildly.


The USAAF really liked things big. While the A-26 wasn't trivial in terms of maneuverability, it wasn't able to pull the g-load a fighter could, and would likely be less accurate than an P-47 or A-36


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## MIflyer (Jul 12, 2021)

Zipper730 said:


> The USAAF really liked things big. While the A-26 wasn't trivial in terms of maneuverability, it wasn't able to pull the g-load a fighter could, and would likely be less accurate than an P-47 or A-36


They did use them for CAS in Vietenam and in the early days there tried what amounted to dive bombing with them - and pulled the wings off a few. That resulted in the B-26K Counter-Invader.


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## Zipper730 (Jul 12, 2021)

MIflyer said:


> They did use them for CAS in Vietenam and in the early days there tried what amounted to dive bombing with them - and pulled the wings off a few.


Yeah, that's what happens when you build up too much speed and then pull up too abruptly. The plane wasn't really built for dive-bombing. It seemed to be built for about 30-degree glide-bombing, maybe 45-degrees.


> That resulted in the B-26K Counter-Invader


They strengthened the wings?


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## Shortround6 (Jul 12, 2021)

Zipper730 said:


> Yeah, that's what happens when you build up too much speed and then pull up too abruptly. The plane wasn't really built for dive-bombing. It seemed to be built for about 30-degree glide-bombing, maybe 45-degrees.
> They strengthened the wings?


From Joe Baughers website.
"The B-26K could carry 4000 pounds of bombs internally, plus up to 8000 pounds on the underwing racks. Besides the fixed wingtip tanks, two 230-gallon drop tanks or a 675-gallon bay tank could be carried. These changes increased the maximum cruising speed from 240 to 265 knots, the combat radius from 210 to 500 nautical miles, and increased the armament load from 7500 to 12,000 pounds."

yes they strengthened the wings. 

"Unfortunately, these B-26s began to suffer frequent wing failures, forcing them out of service. Those that remained were provided with a strengthening wing strap along the bottom of the wing spars to prolong service life. The success of these modifications led the USAF to order a remanufactured version of the Invader from the On Mark Engineering Company of Van Nuys, California that would be specifically adapted to the counterinsurgency role."

"The Counter Invader was powered by a pair of 2500 hp Pratt & Whitney R-2800-103W water-injected engines driving a set of fully-reversible automatic feathering propellers. The wings were entirely rebuilt and strengthened by the installation of steel straps on the top and bottom of the spars. The rudder was enlarged to improve single-engine handling. Permanent 165 US gallon wingtip fuel tanks were installed. An anti-skid wheel braking system was adopted. Deicer boots and anti-icing equipment was added. The instrument panel was revised and provision for dual controls was made. New electronic equipment was adopted. Eight new underwing pylons were added for a variety of external stores. The dorsal and ventral defensive turrets were eliminated, and fixed armament consisted of a set of eight 0.50-inch forward-firing machine guns in the nose. Alternatively, the aircraft could be fitted with a glazed nose for photographic reconnaissance."

The P & W R-2800-103W engines were not used on the production versions. The 2500hp R-2800-52W engines were substituted.

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## MIflyer (Jul 12, 2021)

A friend of mine that got to fly them in Thailand and Laos said the B-26K flew significantly different than the original models. The CG had changed. It felt different and was a bit harder to trim up. Note the "butter paddle" props.

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## Zipper730 (Jul 13, 2021)

Shortround6 said:


> yes they strengthened the wings.


Do you have any idea how much, if it's not classified?


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## MIflyer (Jul 13, 2021)

The friend described the spar mod and I'll ask him about it if I see him today. The book "Foreign Invaders" says the 40 B-26K's had the fuselage re-manufactured with a larger rudder and the wings replaced, using only some of the original spar. They installed new brakes using KC-135 parts and 2500 HP water injected engines as well as all new weapons pylons built by Baldwin Locomotive.

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## Zipper730 (Jul 20, 2021)

While I should have covered this earlier...​


MIflyer said:


> in the Pacific the B-25 and A-20 had proved to be mainly valuable for low altitude attacks. In contrast the mediums seemed to have done almost no strafing in the ETO


While I assume low-altitude attacks over the ETO (in particular, Germany) would have been more dangerous than over the PTO judging by what you wrote, though I'm still surprised they wouldn't have realized a bigger plane would be easier to hit.

While this might sound like a strange question: Did the USAAF have the same guys issuing requirements for fighters, attack planes, and bombers? Or were there different guys for fighters (or fighter & attack), attack planes, and bombers? I'm also curious if there was much communication between them as to what would and would not work (i.e. I know during the pre-war years, there was a hostile relationship between the fighter and bomber guys) during the course of the war itself.

As an additional matter: I was thinking about g-load figures for aircraft that had been employed in dive-bombing attacks and, unfortunately there's not a lot of figures I have, so there's a bit of guesses from various sources, and I'm not sure all of them are accurate


.....*Aircraft**Normal Rated Load Factor*​*Ultimate Rated Load Factor*​.....Douglas SBD6g​9g​.....Junkers Ju 877.2g​10.8g​.....Vultee Vengeance9g @ 11040 lb.​13.5g @ 11040 lb.​.....Fairey Barracuda6g @ 12000 lb.​9g @ 12000 lb.​.....Curtiss SB2C9g​13.5g​.....Bristol Beaufort6.27g @ 17000 lb.​9.4g @ 17000 lb.​.....Bristol Beaufighter5.67g @ 21000-22100 lb.​8.5g @ 21000-22100 lb.​.....Junkers Ju 884.95 - 5.4g​8.1g​.....Heinkel He 1774.8g​7.2g​

Regardless, the figures for the A-26 indicate a normal rated maximum g-load of 4.27g @ 26000 lb. which is below the combat weight and bombs-off. Even if that included a small bomb-load with fuel burned down a lot, it'd still be less than the He 177 which is the lowest figure in the group. The fact that the Ju 88 were sometimes fitted with dive-brakes for dive-bombing missions (some Beaufighters also) also seem to work against the A-26 as well.

While the He 177 was tested by Captain Brown who executed dive attacks in tests, it had a higher maximum g-load than the A-26 as well, and the fact that the probable cruise and maximum speeds would likely exceed the He 177, Ju 88 and Beaufighter, I figure it'd pick up speed faster in a dive which would make it harder to execute the maneuver.


*Notes*

G-load figures for the SBD & Ju-87 were based on the assumption that the ability to routinely execute 6g pull-outs might indicate this to be the normal rated maximum load factor: With the Germans using an ultimate load factor being 180% the normal rated load-factor, the 6g figure would become 7.2g if corrected for the 150% safety factor used by the Allies.
G-load figures for the SB2C were based on a statement that the maximum load the pilot could take was 9g, and the plane was built around that.
G-load figures for the Vultee Vengeance, Fairey Barracuda, Bristol Beaufort, and Bristol Beaufighter are based on this chart, which unfortunately has a number of errors, but is the best information I have available (A flight manual on  covers multiple variants (VI, X & XI) and states the plane should not be violently maneuvered above 21000-22100 lb. depending on modifications implemented).
Figures for the Junkers Ju 88 came from here, with figures from the He 177's figures were from the book "Heinkel: He 177, 277, 274" by Manfred Griehl & Joachim Dressel: The Ju-88 was listed as having a normal rated load of 4.5g with the He 177 being rated for 4g with both rated for safety factors of 180% the listed numbers which, when corrected for allied safety figures produce the specified numbers. The discrepancy with the Ju-88 have to do with the fact that failure occurs at 180% (8.1g) with skin dimpling occurring at 110% (4.95g).

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## Zipper730 (Aug 22, 2021)

Would it have been hard to have designed the A-26 with the ability to pull g-loads similar to the Ju-88 or Beaufighter? This assumes the strength was built into the design from the start, not grafted on.


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## MIflyer (Aug 22, 2021)

I recall reading that the A-26 was the first US airplane designed with the armor built in as part of thee structure rather than tacked on afterwards.

But it was not designed as dive bomber but as a level-in-formation bomber or a low altitude strafer and bomber, In Vietnam they were trying to use it as a dive bomber and that's when the wings started coming off.


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## Zipper730 (Aug 22, 2021)

MIflyer said:


> I recall reading that the A-26 was the first US airplane designed with the armor built in as part of thee structure rather than tacked on afterwards.


I never knew it had integral armor in its construction. Since I don't know how strong the modified A-26's used in Vietnam were, I couldn't determine what could be done then or earlier, but I figured if they won't build a small single-engined bomber, at least they could build a twin that was tough enough to have some dive-capability.


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## Zipper730 (Aug 25, 2021)

drgondog

M
 MIflyer


This is something that was mentioned in another post about how the RAF's Desert Air Force campaigns showed that there was a preference for two types of aircraft: The first was a fast-attack fighter that was agile and capable of air-superiority, recon, and close air support; the second was a fast-attack bomber. 

It appeared that the RAF adopted this around 1941-42: When did the USAAF start to adopt this idea and fully implement it? I'm curious if this was about the same time or significantly earlier (and by that, I mean at 1-3 months as a starting point) that the decision was made to abandon dedicated light-attack aircraft, and if there was a significant difference, if that had to do with bureaucratic inertia or varying points of view?


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## drgondog (Aug 25, 2021)

Zipper730 said:


> drgondog
> 
> M
> MIflyer
> ...


A complex question. The evolution of battlefield air for US morphed from Army doctrine of battlefield Observation/short recon in the mid 30s to fast attack/fast reconnaissance in 1940 with the advent of the A-20 and the implied promise of the P-39 and P-40. That said, the Army still insisted on light s/e observation, while recognizing that the NAA O-47 was a 'tweener' with greater range but increasingly vulnerable - and no bomb capability,

Political pressure on Arnold 1940-41 to adopt Wermacht/LW model of Ju 87 dive bombing and light/medium attack bombers for tactical support. That triggered adoption of the A-24 and A-25, but even without the experience of combat (for US) it was clear that air superiority was required for survival of classic dive bomber - which led to a requirement that the single engine attack aircraft should not only be capable of carrying bombs but be capable of defending itself. 

Coningham's Desert Air Force tactics with heavily armed Hurricanes and various light bombers in the African campaigns was watched closely by the AAF Close Air Support Directorate in 1941 which led to driving Materiel Command to solicit concepts including the selected Brewster XA-32. His (Coningham's) report re: use of fighters in tactical use to Montgomery, landed in CAS Directorate in Dec 1941.

Prior to December, NAA's primary beltway bandit (I have to look up his name) was very well connected to War Department planners and began shaping the argument (with Kindelberger/Atwood) that a modified Mustang design to provide bomb capability, heavy armament and dive bombing capability could compete for Dive Bomber funding remaining for FY 41.

An important 'behind the scene' player was General Lawrence Kuter. He could be considered the most respected 'theoretician' in AAF, shaped the concept that "gaining air superiority is the first requirement for the success of any land based operation'. He was the author of FM 100-20 and shaped the doctrine that the air war superiority must be won by fighters - not bombers. Kuter also was CO of 1st BW, 8th AF and a strong supporter of LeMay's concepts regarding lead crews in Dec 1942, then took command of AAF MTO Allied Air Support Command in Jan 1943.

There were many moving parts in the transition from Observation to Fast Attack. The full implementation could be marked by the introduction of bomb carrying capability for P-39/P-40, replaced by A-36, then replaced by P-51A/P-47 but for a time, the P-51B was scheduled to be the Battlefield Fast Attack/Recon fighter. So the answer to your question of implementation for US? Mid 1943

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## MIflyer (Aug 25, 2021)

The USAAF did not abandon attack aircraft until tests of XA-41, which resembled the AD Skyraider's fatter, uglier sister. They concluded that compared to the P-51, P-47, and P-38 the A-41 could not defend itself nor be used for air superiority. Bombed-up fighters could do just about as good as dedicated attack aircraft and after they dropped their bombs could do air combat. So the "A" designation went away and the USAF found itself in the unfortunate situation of having to scramble to find enough F-51's to do CAS that were already in the theater until a bunch of Mustangs could be referbed and shipped over from the USA.

The Mustang was not at all the best attack aircraft for the mission in Korea but it was all they had. Jets did not have the range or bombload. The USN was much better off with the F4U and AD. The F-47N would have been much better than the F-51 but they had been phased out. P-47's stored at Tinker AFB Ok were sold at prices so cheap that selling the fuel in the airplanes enabled the buyer to pay for them. The F-82 would have been good but all they had were night fighters. 

The A-26 replaced the A-20, B-25 and B-26, but in Korea it was used in strike and interdiction roles rather than strafing and CAS, in other words, level bombing and some rockets. 

Vietnam finally forced the USAF to realize they needed some "A" airplanes.

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## drgondog (Aug 25, 2021)

MIflyer said:


> The USAAF did not abandon attack aircraft until tests of XA-41, which resembled the AD Skyraider's fatter, uglier sister. They concluded that compared to the P-51, P-47, and P-38 the A-41 could not defend itself nor be used for air superiority. Bombed-up fighters could do just about as good as dedicated attack aircraft and after they dropped their bombs could do air combat. So the "A" designation went away and the USAF found itself in the unfortunate situation of having to scramble to find enough F-51's to do CAS that were already in the theater until a bunch of Mustangs could be referbed and shipped over from the USA.
> 
> The Mustang was not at all the best attack aircraft for the mission in Korea but it was all they had. Jets did not have the range or bombload. The USN was much better off with the F4U and AD. The F-47N would have been much better than the F-51 but they had been phased out. P-47's stored at Tinker AFB Ok were sold at prices so cheap that selling the fuel in the airplanes enabled the buyer to pay for them. The F-82 would have been good but all they had were night fighters.
> 
> ...


Materiel Command labored on fat, ugly sisters until an Army Board convened in early 1943 to evaluate attack fighter existing production aircraft (A-24, A-25, XA-32, etc) alternatives to P-39, P-40 and P-51/A-36, recommended that MC 'cease and desist from developing slow battlefield attack aircraft.

The Mustang gets a little too much criticism compared to 'alternative P-47 and P-38' as well as F4U. The loss/sortie rate of the P-51D in Korea was just barely above the F4U and average mission distance was far greater, particularly in first year of Korean War when missions were flown from Japan. In context of 'less vulnerable', the F6F was superior to all of them save the AD.

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## MIflyer (Aug 25, 2021)

One F-51 pilot in Korea summed it by saying, "I was ready to buy a P-47 with my own money, if I could have found one."

Another said he would have rather been flying the P-40 in Korea.

But...... Note this is November 1945.

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## SaparotRob (Aug 25, 2021)

A very sad sight.


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## Thumpalumpacus (Aug 25, 2021)

God-_damn_.


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## MIflyer (Aug 25, 2021)

A friend of mine, a lover of old airplanes, said that in the late 50's he went over to a junkyard in SW Florida and they still had P-40's stacked up on their firewalls like that picture shows. What could you have bought some for? Maybe $50 to $100 each? In 1955 the USN sold off their F8F Bearcats for $500 each.

Years later, the early 70's, another friend of mine bought an F-80 in a junkyard in Florida. I think he paid $500 for it.


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## Zipper730 (Aug 26, 2021)

drgondog said:


> The evolution of battlefield air for US morphed from Army doctrine of battlefield Observation/short recon in the mid 30s to fast attack/fast reconnaissance in 1940 with the advent of the A-20 and the implied promise of the P-39 and P-40. That said, the Army still insisted on light s/e observation, while recognizing that the NAA O-47 was a 'tweener' with greater range but increasingly vulnerable - and no bomb capability,


I do remember the USAAC had observation planes that included single & twin-engined designs. I'm guessing the singles were light-observation?

Regardless, I figure the idea was that they preferred to do away with the observation planes and have the role handled by fighters and light-bombers?



> Political pressure on Arnold 1940-41 to adopt Wermacht/LW model of Ju 87 dive bombing and light/medium attack bombers for tactical support. That triggered adoption of the A-24 and A-25, but even without the experience of combat (for US) it was clear that air superiority was required for survival of classic dive bomber


It was also required for the four-engined heavies too (something I could imagine would have been wildly unpalatable) unless they were going to operate at night (and even the RAF used night-fighters to support their bombers).

I'm curious if the USAAF took heavier losses with their A-24's compared to the USN/USMC's SBD's. I'm curious because if the loss rates were higher for the USAAF, it would indicate one of the following.

A-24 tactics and training could be a problem.
The targets the A-24's are sent after may not be the same ones the USN/USMC are sent after.
Fighter cover is not provided in the same way.



> Coningham's Desert Air Force tactics with heavily armed Hurricanes and various light bombers in the African campaigns was watched closely by the AAF Close Air Support Directorate in 1941 which led to driving Materiel Command to solicit concepts including the selected Brewster XA-32.


I assume the Brewster design offered a whole lot more on paper than it did in real life?

Nobody's going to argue with the idea of using fighters, and the timing (12/1941) could not have been more perfect.


> An important 'behind the scene' player was General Lawrence Kuter. He could be considered the most respected 'theoretician' in AAF, shaped the concept that "gaining air superiority is the first requirement for the success of any land based operation'. He was the author of FM 100-20 and shaped the doctrine that the air war superiority must be won by fighters - not bombers.


Usually that implies sweeping the skies of enemy fighters so the bombers can hammer the hell out of what they need to, correct?


> Kuter also was CO of 1st BW, 8th AF and a strong supporter of LeMay's concepts regarding lead crews in Dec 1942


When you say lead crews, you mean the bombardier/toggleer thing?


> So the answer to your question of implementation for US? Mid 1943


And by October, 1943, the single-seat attack plane was officially dead (that said the XA-41 still flew a few months later).



MIflyer said:


> The USAAF did not abandon attack aircraft until tests of XA-41, which resembled the AD Skyraider's fatter, uglier sister. They concluded that compared to the P-51, P-47, and P-38 the A-41 could not defend itself nor be used for air superiority.


The XA-41 had a number of problems (range & speed). The Skyraider was able to carry more payload (2000 vs 1000 lb.) over greater range, though I'm not sure what range the USAAF deemed essential and preferable.


> The A-26 replaced the A-20, B-25 and B-26, but in Korea it was used in strike and interdiction roles rather than strafing and CAS, in other words, level bombing and some rockets.
> 
> Vietnam finally forced the USAF to realize they needed some "A" airplanes.


Yep.


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## drgondog (Aug 26, 2021)

MIflyer said:


> One F-51 pilot in Korea summed it by saying, "I was ready to buy a P-47 with my own money, if I could have found one."
> 
> Another said he would have rather been flying the P-40 in Korea.
> 
> ...





MIflyer said:


> One F-51 pilot in Korea summed it by saying, "I was ready to buy a P-47 with my own money, if I could have found one."
> 
> Another said he would have rather been flying the P-40 in Korea.
> 
> ...


Unfortunately for the guy that said he would rather have flown the P-40 in Korea, his logic engine wasn't working too well. For early FB missions his first trip with a 500 pound bomb puts him in the water between Japan and Korea on his return trip. For the P-47 drivers, you could get there and back to middle S.Korea with one 1000 pound bomb and one 150 gal fuel tank. P-47N could Match load and range of the P-51D w/ 1000# plus 160 gal tank.

The decision to use the P-51D in Korea was simple, actually. There were several FBG/FG equipped with P-51D in Japan as well as ROC on peninsula. SAAF and RAAF were equipped with P-51D. Common training, common logistics (in a pinch) for all four of the theatre air forces.

There were zero P-47N FG - all reserve, closer that US. There were more National Guard P-51 equipped Groups. Training and Logistics once again. I would have to look, but wonder how many depot stored spare parts or engines (R-2800-57) were available for P-47N

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## MIflyer (Aug 26, 2021)

According to the book "F-51 Units Over Korea" FEAF listed no F-51's on its inventory when the Korean War started. They did have Mustangs that had been used for target towing and they managed to round them up; they found about 10. And even in the earliest days of the war there were F-51's in South Korea flying CAS missions barely outside their airfield perimeter; P-40's would have done just fine. Mustangs pretty much flew out of Korea, not Japan.

FEAF quickly brought about 30 retired Mustangs they had had sitting around the Pacific up to operational status and transferred pilots from other units to fly them. Meanwhile, 145 F-51's were quickly referbed and put on the USS Boxer CVE, which headed for Korea with the throttles wired to Full Power. 

There was a NZ unit flying Mustangs in the area; they had been ordered home. That was changed right away.

By the way, in his book Fork Tailed Devil Martin Caiden claims that there were 50 P-38's that had been retired so the unit could equip with F-51's. But the US State Dept objected to the ROK Air Force from being equipped with the surplus Lightnings for fear of offending the North Koreans. And as a result the P-38's were destroyed with bulldozers, which is really too bad since 50 P-38's could have done wonders in the early days of the North Korean invasion. In reality, the 49th FG did have P-38's at the end of WWII and did stay in the far east, but they reequipped with Mustangs YEARS before the Korean War started and in fact had converted to F-80's by the time things got hot, yet another F-51 unit that Was Not There.

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## drgondog (Aug 26, 2021)

MIflyer said:


> According to the book "F-51 Units Over Korea" FEAF listed no F-51's on its inventory when the Korean War started. They did have Mustangs that had been used for target towing and they managed to round them up; they found about 10. And even in the earliest days of the war there were F-51's in South Korea flying CAS missions barely outside their airfield perimeter; P-40's would have done just fine. Mustangs pretty much flew out of Korea, not Japan.
> 
> FEAF quickly brought about 30 retired Mustangs they had had sitting around the Pacific up to operational status and transferred pilots from other units to fly them. Meanwhile, 145 F-51's were quickly referbed and put on the USS Boxer CVE, which headed for Korea with the throttles wired to Full Power.
> 
> ...


You are correct about opening day inventory. Both the 18th and 35th FG had just transitioned from F-51Dto F-80C (I had forgotten that) and all the pilots were Mustang rated - but the US shipped 145 plus and reequipped both groups w/F-51D. The 8th FG also transitioned to F-51 and the 49th transferred to Korea, then western states ANG units with Mustangs were transferred to Korea.


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## Zipper730 (May 26, 2022)

Shortround6 said:


> And fuel consumption.


This is a pure hypothetical: How did the fuel consumption of 1 x R-4360 compare to 2 x Merlin 21/23's (early Mosquitos) or Merlin 61's?


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