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The central entry supercharger was not Hookers Idea. Rolls Royce was experimenting with it before Hooker joined the firm.I like to look at how things could have been done different with different decision. And try not use hindsight.
I may be using hindsight when I look at lessons from WW I that were forgotten or ignored at the beginning of WWII.
Somethings developed they way they did because in many cases you had to follow the chain.
It didn't do much good to try to build two stage superchargers in the mid 30s because the fuel wasn't going to make anywhere full use of them.
The Merlin (just using it as example, Pick R-1830 if you want) was limited to about 6lbs of boost using the original fuel and supercharger ( with a lower gear ratio and slower impeller it could use more at lower altitude). Now if you stick a two stage supercharger on it several things are going to happen using 87 octane fuel. If you try to get 6lbs of boost at say 24,000ft you are making a more heat in the superchargers and you cannon hit the 6lb boost limit without detonation unless you use a really, really big (read huge) intercooler system. You also have to look at the power being made in the cylinders. Instead of 1030hp at 16,000ft to prop with around 100hp going to friction and somewhere around 150hp (WAG) driving the supercharger you have the same friction, the same 150hp (or a bit less) driving one stage and now you have another 150hp or more driving the 2nd stage. So now you have about 900hp to drive the prop. The standard Merlin III was going to loose about 2% per 1000ft or give you around 900hp at 21,000ft without any extra 'stuff' hanging off of it.
Hooker did several things.
1, he realized that some of the formulas used to design superchargers had errors. This was somewhat masked by the low boost used and the lack of good instrumentation to correlate measured results to theory.
2. He straitened out the intake on the Merlin supercharger and got several thousand feet out of the rest of the design because the whole supercharger was more efficient. He got more compression from the supercharger while using less power to drive it and heating the intake charge less. Gets you to the Merlin XX and 45.
Now you can go to the 2 stage supercharger because you have a more efficient base supercharger and you are being given higher PN fuel that will give you higher performance.
P & W spent years trying to get a 2 stage supercharger to work and in 1938-39 they were using US 100 octane fuel. The performance they were getting in 1938-39 was better than the single stage supercharger but the cost was high.
Two stage engine was good for 1200hp at sea level, single stage engine was good for 1100hp at sea level
...............................................................1050hp at 17,000ft, .........................................................................950hp at 14,300ft
Single stage engine was about 200lbs lighter and didn't need the intercooler
View attachment 689525
see duct under the fuselage. It took a while to get the engine to be the one used the F4F.
Hooker probably could have helped them quite a bit but until you get 100/130 fuel you are not going to get a big increase in power over the single stage superchargers.
Is any more money being made available and if so when? More money earlier would enable more Battles and Blenheims, whether it would also deliver their replacements in a timely manner is more problematical. Now for some statements of the obvious.how the RAF's doctrine and procurement should've looked like in the time frame between 1934 and 1940. Fighters, bombers, trainers, transports, plus how to use them and how many to buy to cover the possible threats, all on the technology of the day Engines, guns, electronics - what to make and buy and use, what to avoid? Deployment on the Continent once the political decision is made?
Overseas supply:What to buy abroad, from components to whole aircraft? Cooperation between the friendly countries?
Some dead wood to cut + rationalization:
New 2-engined heavy bombers need to be able to hold a torpedo in a bomb bay: a 4-engined heavy bomber needs to have a bomb bay to hold two torpedoes. 1-engined bombers need to be trialed with an underslung torpedo.
That removes the need to have separate torpedo bomber types. The Botha debacle (1100+ engines and props invested at the end, plus a lot of other material, as well as man-hours) is thus removed, Blackburn can move on to make useful aircraft (Hampden, Wellington, what you have). Battle will need a better power-to-weight ratio to lift the torpedo, so now is time to install the Pegasus on it (saves ~500 lbs vs. Merlin III, can offer 130 HP more for take off).
I have, in the past, been one who is aghast at the Firebrand program but the brickbats are to be directed at the changes in requirements from the Admiralty. Blackburns themselves did a good job under the ever changing circumstances and the Firebrand went on to serve for six years as the principal anti shipping resource of the Home fleet tasked with sinking the major Soviet naval vessels. Being retained at home for that task despite the Korean War. Even to be fair to the Admiralty they asked for good in the future but knew they needed good enough now for fighters. Hence the retasking of the Firebrand once they squeezed their pre war request for Sea Hurricanes and Sea Spitfires out of the powers that be.! Don't give Blackburn any work!
Sums it up...
The P.13/36 Spec that led to the Avro Manchester and HP Halifax, initially contained a number of requirements including the ability to carry torpedoes, which partially accounts for the long bomb bay in the Manchester as the indications are that they would be carried one behind the other.Some dead wood to cut + rationalization:
New 2-engined heavy bombers need to be able to hold a torpedo in a bomb bay: a 4-engined heavy bomber needs to have a bomb bay to hold two torpedoes. 1-engined bombers need to be trialed with an underslung torpedo.
That removes the need to have separate torpedo bomber types. The Botha debacle (1100+ engines and props invested at the end, plus a lot of other material, as well as man-hours) is thus removed, Blackburn can move on to make useful aircraft (Hampden, Wellington, what you have). Battle will need a better power-to-weight ratio to lift the torpedo, so now is time to install the Pegasus on it (saves ~500 lbs vs. Merlin III, can offer 130 HP more for take off).
I have, in the past, been one who is aghast at the Firebrand program but the brickbats are to be directed at the changes in requirements from the Admiralty. Blackburns themselves did a good job under the ever changing circumstances and the Firebrand went on to serve for six years as the principal anti shipping resource of the Home fleet tasked with sinking the major Soviet naval vessels. Being retained at home for that task despite the Korean War. Even to be fair to the Admiralty they asked for good in the future but knew they needed good enough now for fighters. Hence the retasking of the Firebrand once they squeezed their pre war request for Sea Hurricanes and Sea Spitfires out of the powers that be.
With no Gladiators we are back to flying Gauntlets in a few 1st line squadrons in Sept 1939.
Gladiator production numbers are deceptive.
Wiki says 747 built. however
The RAF ordered 231 MK Is ( with just over 200 on order in 1935?) and 300 Mk IIs in 1938 (with 98 of them being Sea Gladiators.)
Gloster exported 222 (?) Gladiators to 10 different countries before the war (some ex RAF aircraft included)
94 (?) ex RAF machines were exported to a further 5 countries after the war started.
At the time of the Munich crises in Sept 1938 the RAF had 6 Gladiator squadrons on strength, 2 Hurricane Squadrons and 0 Spitfire squadrons. The rest of Fighter Commands strength was Gauntlets, Furies and Demons.
What machinery?
Unless you are trying to get around the labor (union) difficulties.
Castle Bromwich was a brand new factory with new machinery. Sending it's machinery elsewhere doesn't add production.
And besides, the problem with Westland producing any fighters of any sort was that they were busy building 4-7 Lysanders a week.
Priorities
French fighters, even the MS 406, weren't using fixed pitch props. If you are trying to take-off with your cannon armed Hurricane and you can only use 2000-2100hp from your Merlin engine without overspeeding the prop and loosing whatever thrust you do have you have nowhere near the "book" 880 hp.
The above requires a surplus of fighters before they can be allocated to the sort of activities that did happen in 1918, along with the discovery of how survivable bombers were in contested airspace, even relatively close to the front line, yet the allies did field large numbers of light and medium bombers usually doing medium altitude level bombing, the fighter bombers adding to that firepower. Given the 1940 doctrine was more about targets behind the front line the use of Battle and Blenheim level bombers were the intended equivalent of the later war A-20/A-26/B-25/B-26 operations. The 1940 doctrine had plenty of peace time- army cooperation aircraft, including the fighter bombers, or perhaps let's call them 'fast frontline bombers'; proper light transport aircraft for army (sorta pre-An-2, or something like Norduyn Norseman, or someting like Bellanca Aircruiser); small utility aricraft (rather a Storch equivalent, than a Hs 126 equivalent) for artillery spotting, frontline reconnaissance and to shuttle around important people
Well, trying to take-off In a Hurricane with about under 700hp going to the Prop (with the wrong pitch) is a lot different than taking off with over 1200hp and prop with a much better pitch angle. You can get some of the early planes in the air but you are going to have more accidents.It will still take off, no worries.
We are covering 6 years or so.Some things not discussed here, that will require change in the RAF's doctrine:
- long-range fighters (even if not declared as needed for Europe, long range is needed for Asian and African commitments - this might be a loophole?)
the British flubbed the whole army co-operation aircraft thing rather badly. So were many other nations.- army cooperation aircraft, including the fighter bombers, or perhaps let's call them 'fast frontline bombers'; proper light transport aircraft for army (sorta pre-An-2, or something like Norduyn Norseman, or someting like Bellanca Aircruiser); small utility aricraft (rather a Storch equivalent, than a Hs 126 equivalent) for artillery spotting, frontline reconnaissance and to shuttle around important people
We are covering 6 years or so.
Local air transport is another subject but it can only be done at the expense of training aircraft
8,800 was total Tiger Moth production worldwide between 1931 and sometime postwar when overseas production ended. Over 2,800 of those were built overseas. And 3,400 were built 1941-45 by Morris Motors after DH transferred production to concentrate on Mosquito production.But if you are building these then you are not building 8,800 Tiger Moths ( used the same engine for one thing)
It is worthwhile taking a moment to consider the political background and attitudes around the start of the 1930s which does have an effect on the starting point of this discussion.
Disarmament
A Conference for the Reduction and Limitation of Armaments ran from February 1932 to November 1934 under League of Nations auspices before falling apart. One of the things it sought to do was to abolish Offensive Aviation.
One of the subcommittees addressed proposals for limiting construction programmes, payloads, and operational ranges of aircraft.
So how is this relevant to the 1934-1940 period? Well 1932-1934 is when the Specs were issued for aircraft like the Battle, Wellington, Hampden, Whitley etc. In ""The British Aircraft Specifications File" in relation to Spec B.9/32 issued in Sept 1932 that led to the Hampden & Wellington is this comment:-
"Four designs were considered against Specification B.9/32, with contracts awarded to Handley Page and Vickers. Both firms made representations to the Air Ministry about the weight limit imposed by the League of Nations, and the insistence that the tare weight of the aeroplane be adhered to as laid down in the specification. This requirement limited the structural weight and power of the engine. An agreement was reached."
In the Warpaint book on the Wellington this is noted as "outmoded thinking by the Air Ministry" and was "overcome".
"The Vickers team circumvented this restriction and the tare weight of the Wellington rose from 6,300 to 11,508 lbs between the time that the tender was first submited and the date on which the prototype first flew in 1936."
So over 3 years elapsed from issue of the Spec until the prototype Wellington & Hampden flew. Then revised Specs for both were issued in Jan 1937 for the production versions ordered the year before. And a Wellington Mk.I weighed 18,556 lbs empty. A Hampden empty weight was 12,764 lbs. How much redesign effort was expended along the way with these aircraft before we get to the next generation arising from B.12/36 and P.13/36 that led to the Stirling, Manchester and Halifax?
I haven't yet been able to track down any detail on these League technical committee limits to judge what other influences that they may have had on aircraft design.
League of Nations
In March 1933 Japan left the League of Nations. Hitler came to power in Jan 1933 and Germany left the League in Oct 1933.
Who is the enemy?
Until 1934, the RAF saw France as the potential enemy and sought to match it in numbers. That only changed at some point in 1934, when Germany becomes the focus of attention.
But the range characteristics for an aircraft needed to bomb France are different from those needed to bomb Germany. So B.9/32 called for a range of 720 miles at 15,000ft (extendable to 1,250 miles with auxiliary tanks). The Wellington Mk.I had a range of 2,250 miles at 15,000ft and the Hampden 1,720 miles.
Other
I found this study on RAF planning in the 1930s which I found of interest.
Some of this is also relevant to some of the other threads running about the RAF in the 1930s. inforamtive
One of the many clever things Rolls Royce did was to rebuild older Kestrels into Kestrel XXXs for the Miles Master thus conserving production capacity for Merlins.8,800 was total Tiger Moth production worldwide between 1931 and sometime postwar when overseas production ended. Over 2,800 of those were built overseas. And 3,400 were built 1941-45 by Morris Motors after DH transferred production to concentrate on Mosquito production.
Pre-war production at home and overseas totalled 1,424.
Even adding the Miles Magister trainer, produced from 1937, it only adds another 700 or so to the total by the outbreak of WW2.
But without these and other types used as trainers for pilots, navigators and radio operators in the 1930s there is no expansion of the RAF.
This book discusses RAF prewar procurement in great detailFor the RAF idea of the situation.
In particular for this topic, from404
It's possible that the page you were looking for may have been moved, updated or deleted. You could try our search function if you know what you are looking for, or if you typed in a web address please check it was correctwww.raf.mod.uk
404
It's possible that the page you were looking for may have been moved, updated or deleted. You could try our search function if you know what you are looking for, or if you typed in a web address please check it was correctwww.raf.mod.uk
The flying training section and "The Expansion of the RAF 1934-1939"
The above requires a surplus of fighters before they can be allocated to the sort of activities that did happen in 1918, along with the discovery of how survivable bombers were in contested airspace, even relatively close to the front line, yet the allies did field large numbers of light and medium bombers usually doing medium altitude level bombing, the fighter bombers adding to that firepower. Given the 1940 doctrine was more about targets behind the front line the use of Battle and Blenheim level bombers were the intended equivalent of the later war A-20/A-26/B-25/B-26 operations. The 1940 doctrine had plenty of peace time
assumptions, like accuracy and bomb damage expectations, which proved incorrect, but the big gap was intervention around the front line beyond what the Lysanders would do. The RAF actually sent relevant the bomber and reconnaissance assets to France in 1940, but with faulty doctrine and crucially not enough fighter support.
The USAAF did not really like the Norseman, the medical people took advantage of that in 1944 in France to set up their air transport system. Pre war and even Overlord planning did not envisage ground fighting taking place very far from operating rail heads, expecting lots of 1918 style steady advances, so no major need for a big "local" air transport system. No one in the 1930's had the knowledge to come up with a scenario of coping with a heavily damaged rail and port infrastructure with the front line up to hundreds of miles in front of working rail heads. Also air transport is expensive. One benefit of the desired allied airborne army was lots of transports usually available for supply purposes, it is unlikely in Europe at least that big a transport force would be created without the paratroop units being in theatre.
The Lysander was meant as the artillery spotter, local reconnaissance, light attack aircraft and short hop shuttle, remembering the more people you want inside the bigger the aircraft. In any case as was shown the light aircraft in production for civilian uses could be easily adapted and produced. In peacetime it is usually better to spend the money on the bigger aircraft and more combat types, since transports etc. are rather like small ships in the navy, hard to find money for pre war and usually the simplest requirement to fill during the war by cranking up the relevant civil production lines.
Also consider the wartime expansion of the definition of flyable weather, the more often the aircraft could fly the more useful they became, no one pre war had the information to envisage what the 9th Air Force did. Put a high quality radar near the front line and use it to guide aircraft onto targets in poor to bad weather, ground controlled ground attack, similar for the use of radio and radar based bombing aids. Pre war it was all visual bombing and the air forces were all well aware of how often the weather allowed that. Look at all the low activity due to weather, effectively rest, days during the Battle of Britain.
HiThis book discusses RAF prewar procurement in great detail
Expensive but well worth it in my option.
Sinnott's PHD thesis which is the basis of this book is available online somewhere