Advantages & Disadvantages: Nations & Doctrine, Aircraft and Technology of WWII

[Shortround6]

To fit all those 250lb bombs?

Think about it.
2in of clearance between the nose of the torpedo and the bomb bay, 2in between the torpedoes and 2in from the rear of the 2nd torpedo and the back of the bomb bay. Of course this wouldn't be the first time the right hand (aircraft design) didn't know what the left hand (torpedo design) was doing.

A Wellington could carry two torpedoes.

 

[Koopernic]

Not sure what the advantage of carrying the torpedoes end to end would be in a bomb bay that was 5 feet wide.

you had 33 ft of length and a MK XII torpedo was 16ft 3 in long which sounds like a tight fit. Perhaps the slightly older MK XI was shorter?

British air dropped torpedoes were 18 inches and about 17 feet long. Surface launched Torpedos were 21 inch and about 22 feet long.

Perhaps they had in mind carrying two of the larger torpedoes or 4 of the smaller ones.

 

[Zipper730]

The size and weight of bombs that could be carried in each bomb bay was different.

The Wellington, for example, had two racks creating 3 bays in its bomb bay.

The racks could, and were, removed to carry the 4,000lb HC "Cookie".

Were any structural changes needed?

I believe the Stirling's bomb bay restricted the diameter and length of ordnance that could be acrried.

I believe those are the 2,000lb HC bombs being loaded into the Stirling. I don't believe the Stirling could carry the 4,000lb HC bomb.

So a 2000 is like... a baby-cookie?

 

[wuzak]

Were any structural changes needed?

At least one - the two bomb beams were removed.

So a 2000 is like... a baby-cookie?

In that it was a High Capacity (HC) thin case blast bomb. It was developed at around the same time as the 4000lb HC bomb, but was not a scaled version. It was longer than the 4000lb HC bomb and of smaller diameter.

 

[stona]

The HC bombs developed in WW2 were a development of the 1,650 lb SN high explosive blast bombs first used in 1918. The placement of the order for the original 4,000 lb HC 'cookie' came as a direct result of the devastation caused by the German parachute G mines dropped on London, Coventry and Birmingham during the 'Blitz'.
Initially the British struggled to find the right, or even available, explosive for HC bombs. Early versions contained Amatol, but this was already being supplanted by Cyclonite (RDX/TNT, which filled many of these earlier devices), Torpex, Amatex and Minol. It was the addition of aluminium powder in the composition of Minol in 1943 that really increased the blast effects and the secondary incendiary effects of the HC bombs.
Though the initial requirement was for a 4,000 lb bomb, a 2,000 lb version was ordered within weeks. Production of the 2,000 lb HC bomb started in late 1941 and continued into 1943. The early Mk 1 featured a conical nose and a parachute drogue (like the German mine), but this was soon abandoned in favour of a simple cylindrical tail.This weapon was used in the raids on Lubeck and Rostock in the spring of 1942. The Mk II and Mk III versions were in service by 1943, neither had side pockets for delayed fusing as low level use of this type of bomb had been abandoned. The Mk I had three bomb pistol pockets in the nose to guard against possible pistol defects, but rather optimistically two were blanked off on the Mk II. Bomber Command's dissent led to them being re-instated on the Mk III.
During the war 28,633 2,000 lb HC bombs were dropped, mostly Mk IIIs.

Cheers

Steve

 

[stona]

Here's a picture showing the 2,000 lb HC bomb with its 4,000 lb and 12,000 lb cousins. In the foreground are the ubiquitous 500 lb MC bomb and its big brother, the 1,000 lb MC bomb.

The 2,000 lb bomb has a diameter of 18.5", it was a requirement that it be possible to carry it in all aircraft capable of carrying the 1,900 lb GP bomb.
The 4,000 lb HC bomb had a diameter of 30"
The sections that made up the 8,000 lb or 12,000 lb HC bombs had a diameter of 38". Contrary to popular belief the sections making up these 'super cookies' were not the same as that of the 4,000 lb 'cookie'.

Cheers

Steve

 

[Zipper730]

At least one - the two bomb beams were removed.

So, I would assume they weren't load bearing?

 

[Shortround6]

I am puzzled about removing what I think are the bomb beams ( I must be mistaken?) in the photo.
Are they the longitudinal divisions that split the bomb bay into three sections?
It seems that there are 3 sets of doors attached to the beams?
5 sets of doors total? the outer doors on each side hinged to the outer fuselage walls and curved. A short inner door on each side hinged to the 'bomb beam". And a 5th door hinged to the port beam (on the right in the photo) that closed off the middle bay?

I am not saying it wasn't done but I can't seem to find any pictures of a 4,000lb cookie actually in a Wellington. Several pictures of a 4000lb bomb in front of a Wellington (usually blocking the bomb bay from view.)

Can't find any pictures of an alternative set of bomb bay doors ( at least open).

If someone could supply such photos I would appreciate it.

 

[MiTasol]

Oh boy..............

At times there was a fumble, Dr Sanford Moss describing the failure of GE to put a combustion chamber between the compressor and turbine of a standard turbo charger as "Just dumb, just dumb".

Stanford Moss ran his first gas turbine around 1914 and that was a turbo shaft engine designed to power an electrical generator. Like the first turboshaft engine ever built, by the French around 1896, it did not produce the power in practice that it did in theory. The French engine weighed some 600 tonnes. Another Frenchman designed and patented an axial flow jet engine that looked very like the early Jumo engines around ww1 but never built it. The concept was excellent apart from the hand crank starter.

When the US started into turbocharger design Moss was the man chosen to develop the technology as it was an offshoot of his gas turbine work. He soon developed a test rig that took the discharge from the compressor, ran it through a combustion section and into the turbine, in essence a jet engine in WW1.

Several people reputedly suggested this would make a great engine but his response was, in modern parlance, been there, done that, don't work. On the positive side, once he got the Whittle plans he was able to build a better engine than Whittles team in very short order as he had far more advanced compressors and turbines in production.

I have an old wordperfect file with the full dates etc but no way to read it or I could name and date the French engine and give the dates of Moss's first engine.

A quick web search could not produce a program to open it but I shall keep trying.

 

[stona]

I am not saying it wasn't done but I can't seem to find any pictures of a 4,000lb cookie actually in a Wellington. Several pictures of a 4000lb bomb in front of a Wellington (usually blocking the bomb bay from view.)

Wellingtons certainly dropped the 4,000 lb HC bomb, with a 30" diameter. I'm not sure exactly how the bays were modified to fit the weapon, but have seen a reference to strengthening the bomb beam (singular, maybe just the central beam?). I seem to remember that the ability for the bomb to be carried by the Wellington was a requirement in the specification, though I can't find a reference for that. It might explain the larger diameter of the heavier HC bombs which did not have this restriction. A Lancaster bomb bay is 5' wide !

It was two Wellingtons, one from 9 squadron and one from 149 squadron, that dropped the first two 4,000 lb HC bombs of the war on Emden on the night of 31st March/1st April 1941.

Cheers

Steve

 

[wuzak]

I am puzzled about removing what I think are the bomb beams ( I must be mistaken?) in the photo.
Are they the longitudinal divisions that split the bomb bay into three sections?
It seems that there are 3 sets of doors attached to the beams?
5 sets of doors total? the outer doors on each side hinged to the outer fuselage walls and curved. A short inner door on each side hinged to the 'bomb beam". And a 5th door hinged to the port beam (on the right in the photo) that closed off the middle bay?

I am not saying it wasn't done but I can't seem to find any pictures of a 4,000lb cookie actually in a Wellington. Several pictures of a 4000lb bomb in front of a Wellington (usually blocking the bomb bay from view.)

Can't find any pictures of an alternative set of bomb bay doors ( at least open).

If someone could supply such photos I would appreciate it.

This is the bomb bay of the Wellington at Brooklands.

You can see the two bomb beams either side of centre, forming 3 bomb bays as such. The port beam has 2 doors and the starboard 1 door. I believe the port beam could carry bombs on both sides. Maybe the starboard beam could too.

The bomb carriers are hung of the sides of those beams.


View: https://www.flickr.com/photos/16329449@N05/8912428411


One of those bomb beams was modified to fit the Mosquito with bulged bomb bay, with the purpose of allowing the carriage of 8 250lb TIs.

 

[stona]

Is that a 1000lb MC bomb hanging in the bay? That had a diameter just shy of 18", which means a 30" diameter cookie might just have fitted in the outer bays. If its a 500 pounder with a diameter just shy of 13" it probably wouldn't
Cheers
Steve

 

[Shortround6]

Thank you for the pictures.
I do have one reference saying the ability to carry 4000lb bombs was the type 423 modification but have zero details on what that was. I don't know if the Wellingtons with such modification were general issue or confined to a few specialized squadrons. Some pathfinder squadrons (like Nos 109 and 156?) were equipped with Wellingtons,at least for part of the war.

Plenty of books say the Wellington carried the 4000lb cookie on some mark IIIs but even much later Marks used the 3 bay bomb bay.

 

[stona]

Typically a modification like that would have been applied to all aircraft produced after a certain date and possibly retroactively to aircraft from earlier production blocks. I strongly suspect that all Wellingtons from late 1940 onward were adapted to carry the 4,000lb HC bomb.
Cheers
Steve

 

[Greyman]

Bomber Command Wellingtons dropped 1,927 'cookies'.

From the manual:

Loading of 4,000 lb. bombs

40. The 4,000 lb. bomb can only be installed in aeroplanes specially modified for its accomodation and support. The bomb is slung centrally from a tubular beam, mounted above the flooring between the fuselage leading edge frame and the spar centre section; the beam incorporates a suspension bracket for a type F (W) bomb release unit and two crutches at each end, adjustable within small limits. The bomb compartment is enclosed above by a fabric housing but is open at the base, through which the bomb slightly projects. The hydraulically operated doors for the outer cells of the original long bomb compartment are retained, enabling access to be gained to the crutch adjusting screws. The central portion fore and aft of the 4,000 lb. bomb compartment is sealed by fabric.​

 

[stona]

I doubt that all Wellingtons were modified in that case.
Cheers
Steve

 

[Shortround6]

so it sounds like the the two bomb beams were removed along with the doors attached to them and the resulting gaps, except where the bomb actually was, were covered by fabric panels?

 

[tomo pauk]

From a good friend:

 

[wuzak]

Is that a 1000lb MC bomb hanging in the bay? That had a diameter just shy of 18", which means a 30" diameter cookie might just have fitted in the outer bays. If its a 500 pounder with a diameter just shy of 13" it probably wouldn't
Cheers
Steve

At best it is a 500lb MC bomb. Quite possibly it is a 250lb GP bomb. I have a side view, but it is horribly out of focus.

 

[MiTasol]

Stanford Moss ran his first gas turbine around 1914 and that was a turbo shaft engine designed to power an electrical generator. Like the first turboshaft engine ever built, by the French around 1896, it did not produce the power in practice that it did in theory.

Well the above shows how bad my memory is, Moss started earlier and the French later than I remembered.

Many thanks to Cherry Blossom for providing me a link that was able to convert the WP file to a MS file.

I typed the following from a library book that I had for a few days around 1990 when scanners either did not exist or were not known to me.

I did not, unfortunately, record the book name or author.

Reaction propulsion was discussed as early as the seventeenth century, and numerous devices were patented during the First World War. In 1921 a Frenchman named Charles Guillaume patented a complete axial flow turbojet in very nearly its modern form. There was one difference: Guillaume's patent drawings, in addition to showing the expected compressor, combustion chamber, and turbine, also show, protruding from the front of the engine, a very large manual starting crank. One wonders how aeronautical engineers would have streamlined that. Guillaume's concept, although the same configuration as a turbojet, was never built and did not have the valid scientific assumptions that made the turbojet practical. To say that he "invented" the turbojet in any meaningful sense is absurd.



The first man to design a turbojet in accordance with sound aerodynamic insight and pursue the concept through to reality was Frank Whittle. Turbojets, however, emerged independently from the work of four men: Frank Whittle in England; Hans von Ohain, Herbert Wagner and Helmut Schelp in Germany. Only Whittle and von Ohain directed their efforts toward a turbojet from the beginning. Wagner started with a general inquiry that led directly to the turbojet. Schelp, an engineer in the German Air Ministry, separately arrived at the turbojet conclusion and initiated a government supported turbojet program. These four men were the leading players in the turbojet revolution.



Intertwined with development of the first industrial centrifugal compressors was the development of the first internal combustion gas turbines, mainly for power generation.



Like the water turbine or the steam turbine, the gas turbine has remote origins. Mediaeval Europe knew the gas turbine as a "smoke jack" installed in a chimney: rising hot smoke turned a windmill like turbine geared to a cooking spit. The first design for an internal combustion gas turbine proper is attributed to John Barber in England, who was granted a patent in 1791. The idea of the gas turbine was kicked around for most of the nineteenth century, but with little attention and no serious development. The impetus for gas turbine development came, quite naturally, from the success of the steam turbine.



The first non steam gas turbine to be built did not incorporate internal combustion. The Stolze Hot Air Turbine was designed in Berlin beginning in 1872 but not constructed and tested until 1900-1904 and employed a hot air cycle. The multistage axial flow air compressor fed compressed air to a heat exchanger in which the compressed air was led through a furnace. The heated compressed air turned a multistage axial-flow turbine which powered the compressor and was expected also to provide excess useable shaft output. The axial-flow compressor was among the first ever used, but the lack of adequate aerodynamic theory at the time doomed all such systems to hopeless inefficiency.



In the early years of the twentieth century, many schemes for internal combustion turbines appeared. Innumerable patents were issued, chiefly in England, France, Germany, and the United States. The proposed modes of operation for the internal combustion turbine were as varied as the number of inventors was large. There were designs using rotating combustion chambers, contra-rotating or reverse flow blading, self-compressing turbines, and so on. All proposals were however variations on one of two basic cycle types - "constant volume" or "constant pressure".



Constant volume gas turbines employ combustion chambers that operate intermittently, each in turn exhausting onto on some form of turbine. Constant pressure gas turbines, also called "continuous combustion turbines, use a turbine driven by the steady flow of gas from continuous combustion under pressure in a combustion chamber. All successful gas turbines, and absolutely all turbojet engines, have been of the constant pressure type.



Despite the hundreds of designs only three proposals were subjected to serious full scale experimentation before World War one: the constant volume design of the German engineer Hans Holzwarth and the similar constant pressure designs by Rene Armengaud/Charles Lemale in France and by Sanford Moss in the United States.



The first Holzwarth gas turbine was constructed between 1906 and 1908 and "operated on the explosion cycle without precompression." Based on the results obtained with the experimental engine, a second gas turbine with a nominal rating of 1,000 h.p. was built and tested, between 1909 and 1913. This, however, gave a nett output of only about 200 h.p. This second gas turbine employed a small centrifugal compressor, ten water cooled explosion combustion chambers (essentially pulse jets with exhaust valves) and a two stage Curtis turbine wheel with water cooled nozzles.



Each chamber fired successively, one exhausting while the others were in other phases of the cycle. Combustion temperatures were 1,600° to 2,000°C. The machine was massive: the entire setup weighed 53 1/2 tons. While the Holzwarth design did enjoy limited success until the Second World War its weight, complexity, and inefficiency precluded it from consideration for use in aircraft.



Meanwhile, in 1901, two remarkably parallel, although completely separate, constant pressure internal combustion gas turbine projects were started; that of Sanford Moss, which was conceived at the University of California, begun at Cornell, and extensively developed in the General Electric laboratories and that of Armengaud and Lemale in Paris.



The efforts of Armengaud and Lemale were probably the first elaborate gas turbine experimental work. Charles Lemale had applied for a gas turbine patent in 1901. He and Rene Armengaud began actual operation of a gas turbine in France in 1903. The turbine operated at constant combustion pressure using petroleum fuel which was ignited by a glowing platinum wire.



The promise shown by the first Armengaud-Lemale experiments led to the construction of a larger turbine during 1905-6. This employed a centrifugal compressor with twenty-five impellers in series arranged in three casings, all on the same shaft. Auguste Rateau and Armengaud jointly designed an internal water-cooling system for the entire compressor. The compressor delivered about 2,150 c.f.m. of air at a compression ratio of approximately 3:1; ran at 4,000 rpm, required 328 h.p., at an efficiency of 65 to 70 percent depending upon load. It used a single pear shaped carborundum-lined combustion chamber into which petrol was injected and atomised. Combustion was continuous at a temperature of 1,800° C. A convergent-divergent water jacketed (for cooling) nozzle was fabricated integrally with the combustion chamber which exhausted through a two stage impulse turbine, the disc and blades of which were also provided with internal cooling water passages. The water used to cool the compressor, nozzle, and the turbine was passed through coils downstream from the turbine itself, where the hot cooling water was converted into steam in the exhaust. This steam was exhausted, via separate nozzles, onto the same turbine. By injection of the lower temperature steam, turbine running temperatures were reduced to 400°C.



The engine produced about 300 h.p. nett versus 500 h.p. designed. It was, however, grossly inefficient, burning 3.9 lb. of petrol per brake horsepower hour, compared to 0.5 lb. petrol per brake horsepower hour for contemporary piston engines.



Simultaneously Sanford Moss in the United States was conducting almost identical, although totally independent, experiments on internal combustion gas turbines.



Moss invented his gas turbine while in the thermodynamics and hydrodynamics classes of Prof. Frederick G. Hesse at the University of California in 1895. Moss submitted a master's thesis on gas turbine design, including a proposal for a turbine powered locomotive, to the University of California in 1900. In 1901, Moss began gas turbine research in the Sibley College Laboratory of Cornell University. It took a year of concentrated effort just to get a continuous combustion chamber in stable operation.



Moss's Cornell experiments were not successful. As with many other experimental gas turbines, the power for compression was more than the turbine power. Except for the historical fact that the combustion chamber actually operated the turbine wheel, the experiment was a flat failure.



In June of 1903 Moss went back to General Electric, for whom he had previously worked as a steam turbine draftsman, and continued to pursue his gas turbine research. As was rapidly becoming customary at G.E., their investigations into the various elements of internal combustion gas turbine design were the most thorough and comprehensive to that time. Extensive experiments were begun in the fall of 1903 on centrifugal compressor design, and a 1904 patent application in Moss's name demonstrated theoretically the relation between the velocity of flow of a compressible fluid and diffuser shape. Essentially, Moss showed that for flow velocities below the local speed of sound in a compressible fluid (gas), compressor diffuser design could be treated "just as with an incompressible fluid" (water, for example), and that divergent diffuser passages were appropriate.


On the basis of Moss's theory G.E. began successful development of centrifugal compressors. Moss also performed fundamental investigations of energy conversion in nozzles, using compressed air, steam, or the products of internal combustion as his working medium.



General Electric experiments continued until 1907, when fuel consumption was 4 lb. of kerosene per net hp/hr compared to good oil engines using 1 lb. of oil per net hp/hr. No way then seemed open to do better, and so the gas turbine part of the research was stopped. Moss continued at GE first on centrifugal compressors and the piston engine turbo-supercharger research and development program.



After 1920, Glenn B. Warren joined GE concentrating on steam turbine problems, especially on materials resistant to high temperature creep and vibration, turbine blade and disc design, and, significantly, nozzle design. In all of these areas, G.E. made major progress during the 1920s and 1930s, and this progress played a basic role in their ultimate capacity to adopt and develop the turbojet. In May 1941 GE accepted a US Army contract to build Whittle engines under licence and the first GE engine was run ten months later on 18 March 1942. The Bell XP-59 flew with two GE engines in October 1942.



Several other gas turbine projects, deserve mention. About 1908 A. Barbezat supervised construction of a turbine of the Karavodine "explosion" system. The mode of operation of the Karavodine combustion chamber was identical to that of the "pulse jet" as used later in the German V-1 flying bomb.



Hugo Junkers, professor of mechanical engineering at Aachen Technical University (and soon to be of aircraft fame), together with Otto Mader, worked before the First World War on a free-piston engine, a system in which crank-less opposed pistons are used to produce exhaust gas to run a turbine.



Of the hundreds of gas turbine proposals current in 1900, few were developed, and only those of Holzwarth, Armengaud and Lemale, and Moss, seriously. Most of the projects were terminated outright so the first gas turbine revolution proved largely abortive. Ironically, its most successful results were centrifugal superchargers and turbo-superchargers for piston aircraft engines.



In England in 1926, A. A. Griffith wrote a report for the RAE proposing a new aerofoil theory of axial compressors. Griffith argued that the design of the blading of the compressor should be approached through aerofoil theory in order to get the maximum transfer of energy with minimal losses (the same as lift and drag, respectively). The converse of the same argument would be valid for turbines.



An appendix to that paper applied the new theory to the design of a hypothetical turboprop engine. During 1927 the Aeronautical Research Council authorised a small single-stage test rig which was built and tested under Griffith's supervision yielding stage efficiencies of better than 90 percent.



Griffith continued to develop his axial flow compressor ideas, and in November 1929 submitted a memorandum to the ARC containing a design study for a very complex contra-rotating, contra-flow, 500 h.p. turboprop engine. In his proposal, Griffith sought an engine fully competitive with contemporary piston engines in power, weight, and fuel consumption. Construction was approved but the Depression resulted in cancellation. Griffith eventually designed the Rolls Royce Avon engine.