What would a "best of lot" heavy bomber from 1943 look like?

Alan J,

XB-42, Los Angeles to Washington DC nonstop at 433 MPH on a day when winds at altitude were below expectation (flightplan for 445)

I've always admired the aerodynamics of the DH 98 series and the way its performance was improved over the five years of development and engine uprating. I'm also aware that its loss rate attributable to structural failures was approximately three times that of the next worse RAF aircraft (attributed in reports to poor glue bond design)

The Douglas XB-42 did not benefit from a comparable long period of flight testing and improvements, and flew only with its original Allison V-1710-125 engines of 1325 HP. The Mosquito prototype with 310 more horsepower and half the weight of the XB-42, after nearly a year of development showed a maximum speed of 388 MPH , the Mixmaster demonstrated 410 MPH on its fourth test flight. With the ultimately intended turbocharged variants, speed at altitude was expected to exceed 470 MPH. Long range (3600 miles) cruise with the single stage Allisons was 312 MPH lugging 4000# half way. (Edit- I don't know where in a mission the 312 would be measured. Even with the single stage Allisons, the flight would be a step climb, with altitude increasing as weight diminished to maintain constant lift coefficient.- possibly throttling back as well for the same reason. Let's assume the speed is just prior to the over-target dash, with payload and return fuel load on board.)

Maybe we should have defined "Bomber" in this thread. The '42 was designed to deliver a bomb load of between 4000 and 8000 pounds over a distance (for the smaller payload) of 1800 miles -this is out and back. I understand that a modified Mosquito could carry a 4000 pound payload, but how far?

Dynasoar
 
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Alan J,

XB-42, Los Angeles to Washington DC nonstop at 433 MPH on a day when winds at altitude were below expectation (flightplan for 445)

Adjusted for the 60 mph tail wind the speed was ~375 mph, figure by Douglas, per 'Vee's for victory' pg. 179.

I've always admired the aerodynamics of the DH 98 series and the way its performance was improved over the five years of development and engine uprating. I'm also aware that its loss rate attributable to structural failures was approximately three times that of the next worse RAF aircraft (attributed in reports to poor glue bond design)

Is there some tabulated source for this?

The Douglas XB-42 did not benefit from a comparable long period of flight testing and improvements, and flew only with its original Allison V-1710-125 engines of 1325 HP. The Mosquito prototype with 310 more horsepower and half the weight of the XB-42, after nearly a year of development showed a maximum speed of 388 MPH , the Mixmaster demonstrated 410 MPH on its fourth test flight. With the ultimately intended turbocharged variants, speed at altitude was expected to exceed 470 MPH. Long range (3600 miles) cruise with the single stage Allisons was 312 MPH lugging 4000# half way.

2295 miles, with 1153 gals (6918 lbs) of fuel used from Long Beach to the D.C, no bombs carried. Mixmaster used 2-stage V-1710s. The turbochaged P-38L was under 430 mph, there was no chance for the much bigger & heavier ixmaster to beat that on same powerplants. The V-1710-125 was not flown in a Mixmaster. The war emergency power, on 3200 rpm, of the -103 was 1820 HP, the -129 was at 1900 HP.

Mixmaster was empty at ~20900 lbs, max TO 35000 lbs, leaving 14000+ lbs for fuel, oil, bombload, ammo, crew - quite an useful figure to mix & match bomb load with fuel load.

Maybe we should have defined "Bomber" in this thread. The '42 was designed to deliver a bomb load of between 4000 and 8000 pounds over a distance (for the smaller payload) of 1800 miles -this is out and back. I understand that a modified Mosquito could carry a 4000 pound payload, but how far?

Dynasoar

A 4000 lb bomb load and 6000 lb (1000 gals) fuel load indeed offers possibility for long range and sizable bang. Seems like 6000 lbs was the max bomb load.
Mosquito's best was 4000 lb cookie + 2 x 500 lbs, with ~600 US gals of fuel.
 
Alan J,

XB-42, Los Angeles to Washington DC nonstop at 433 MPH on a day when winds at altitude were below expectation (flightplan for 445)

I've always admired the aerodynamics of the DH 98 series and the way its performance was improved over the five years of development and engine uprating. I'm also aware that its loss rate attributable to structural failures was approximately three times that of the next worse RAF aircraft (attributed in reports to poor glue bond design)

The Douglas XB-42 did not benefit from a comparable long period of flight testing and improvements, and flew only with its original Allison V-1710-125 engines of 1325 HP. The Mosquito prototype with 310 more horsepower and half the weight of the XB-42, after nearly a year of development showed a maximum speed of 388 MPH , the Mixmaster demonstrated 410 MPH on its fourth test flight. With the ultimately intended turbocharged variants, speed at altitude was expected to exceed 470 MPH. Long range (3600 miles) cruise with the single stage Allisons was 312 MPH lugging 4000# half way.

Maybe we should have defined "Bomber" in this thread. The '42 was designed to deliver a bomb load of between 4000 and 8000 pounds over a distance (for the smaller payload) of 1800 miles -this is out and back. I understand that a modified Mosquito could carry a 4000 pound payload, but how far?

Dynasoar

LOL ... we were asked about "best in show" in 1943 .. even if we had to create a "mongrel" from many existing designs.

However

the XB-42 did not exist even on paper till May 43
it did not fly till Mid 1944 and was not ready for production even by VJ day
exactly 2 were built (basically by hand.. so no real indication of produceability ... is that a real word :p)
the design proved unstable in flight... and other faults as might be expected with a radical design,
and very difficult to take off, land or even taxi on the ground
one prototype crashed
the other had to be fitted with jet engines to be considered useful

Most importantly for the projected cost of one B-42 you could have 3 or more Mossie B
so the theoretical payload advantage is moot.

Since most air forces, especially the USAAF were dropping lots of smaller bombs not single large ordinance
there are no advantage in one heavy over two mediums

Ironically only the RAF developed and deployed effective large ordinance - and they were wedded to area bombing.

BTW your definition of a "heavy bomber" would basically exclude the B-17, so I should watch your back from the Doolittle/Spatz cabal :rolleyes:
 
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Tomo and Alan

Dealing with structural issues- from Wiki DeHavilland Mosquito entry:

In November 1944, several crashes occurred in the Far East. At first, it was thought these were as a result of wing structure failures. The casein glue, it was said, cracked when exposed to extreme heat and/or monsoon conditions. This caused the upper surfaces to "lift" from the main spar. An investigating team led by Major Hereward de Havilland travelled to India and produced a report in early December 1944 stating that "the accidents were not caused by the deterioration of the glue but by shrinkage of the airframe during the wet monsoon season". However a later inquiry by Cabot & Myers definitely attributed the accidents to faulty manufacture and this was confirmed by a further investigation team by the Ministry of Aircraft Production at Defford, which found faults in six Mosquito marks (all built at de Havilland's Hatfield and Leavesden plants). The defects were similar, and none of the aircraft had been exposed to monsoon conditions or termite attack. Thus the investigators concluded that there were construction defects at the two plants.

They found that the "...standard of glueing...left much to be desired.”[87][88] Records at the time showed that accidents caused by "loss of control" were three times more frequent on Mosquitos than on any other type of aircraft. The Air Ministry forestalled any loss of confidence in the Mosquito by holding to Major de Havilland's initial investigation in India that the accidents were caused "largely by climate"[89] To solve the problem of seepage into the interior a strip of plywood was set along the span of the wing to seal the entire length of the skin joint.[87]

As for the engine selection for the XB-42, also from Wiki.


Specifications (XB-42)[edit]
Data from McDonnell Douglas Aircraft since 1920[8]

General characteristics

As for the cross country flight I am relying many conversations with one of the Douglas project engineers on the XB-42 and the subsequent CloudsterII, also a tail prop pusher configuration; Peter Soule'.- as well as discussions with Jack Norris, Burt Rutan's Director of Propulsion during the design and throughout the flight of the Voyager. Norris is also the author of an AIAA paper on Propeller efficiency as a function of location on the airframe. I have not read "Vees for Victory, but have no reason to doubt there was disappointment at the slower than planned X-C flight. As i go through my files, if I find any more data, supporting or contradictory, Ill be glad to add it to the discussion.

Dynasoar
 
Tomo and Alan

Dealing with structural issues- from Wiki DeHavilland Mosquito entry:
...

Thank you.

As for the engine selection for the XB-42, also from Wiki.

Specifications (XB-42)[edit]
Data from McDonnell Douglas Aircraft since 1920[8]

General characteristics


1325 HP was the take off power on 3000 rpm and 54 in Hg - power and settings frequently found on many V-1710 non-turbo engines. WER 'wet' (= used water-alcohol injection) was done at 3200 rpm and 75 in Hg, for 1820 HP at low level.
As for the cross country flight I am relying many conversations with one of the Douglas project engineers on the XB-42 and the subsequent CloudsterII, also a tail prop pusher configuration; Peter Soule'.- as well as discussions with Jack Norris, Burt Rutan's Director of Propulsion during the design and throughout the flight of the Voyager. Norris is also the author of an AIAA paper on Propeller efficiency as a function of location on the airframe. I have not read "Vees for Victory, but have no reason to doubt there was disappointment at the slower than planned X-C flight. As i go through my files, if I find any more data, supporting or contradictory, Ill be glad to add it to the discussion.

Dynasoar

The cruising power total was probably around 2000 HP - not much for an aircraft with 555 sq ft wing and wide fuselage.
 
Tomo,
The reason for my interest in the XB-42 is the location of the propeller in the accelerated wake of the fuselage. Installed efficiency of the contra props in this example can substantially exceed that of a propeller-nacelle-wing combination and depending on inflow, can actually exceed that of a propeller tested on a spindle.

Rather than set myself up for another long typing session, I'll try to locate Jack Norris' AIAA paper so anyone interested can download it. 2000HP into a 65% efficient system is considerably less than the same power into 92 or 93%, which was the basic consideration in selecting the configuration iin the first place.

Dynasoar
 
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