Fighter-Bombers in the late 1930s and the Fw 187

[kool kitty89]

Continued from the line of discussion that developed following my post here:
http://www.ww2aircraft.net/forum/aviation/horton-ho-229-vs-vampire-43105-5.html#post1199522

The P-40 was often touted as a ground attack fighter to explain it's lack of altitude performance. Yet it was never rated as having an external bomb load until the C model. Perhaps (personal conjecture here) the Army was afraid that if Congress thought the pursuit planes could carry bombs they would NOT fund attack bombers?

According to Curtiss XP-40
"The XP-40 flew for the first time on October 14, 1938, with test pilot Edward Elliot at the controls. Armament was two 0.50-inch machine guns located in the upper fuselage deck and synchronized to fire through the propeller arc, standard armament for US pursuit aircraft at the time. Wing racks could be fitted for six 20-pound bombs."

So the initial prototype at least had provisions for installing bomb racks similar to the P-36. Perhaps some of the production P-40s retained such provisions as well, but weren't ever fitted? (prior to the adoption of the belly shackle, the bomb load limit was pretty light, even compared to the USN's 200~232 lbs)

As for the Fw 187, In 1937-39 such aircraft as the Do 17 and Ju 88 were viewed as Schnellbombers, and against such things as PZL P11 they were. And if you had enough spare DB601 engines to build Fw 187 "bombers" why not build Do 215s instead?

Even assuming the advantages of a multi-role aircraft were ignored, the Fw 187 still had the advantages of being faster than the Ju 88 or Do 215 while using stocks of existing older Jumo 210 engines. (possibly using the Bramo engines of the Do 17 as well) Though Focke Wulf never attempted using alternate engines, Bramo and (especially) Jumo 211 engines would seem quite useful. (the Bramo would help more for climb and take-off performance than top speed, so attractive for potential high takeoff weights of bombloads as well as reduced engine vulnerability)


On the issue of American 1930s fighters having both bomb AND drop-tank carrying ability that disappeared with the P-40, P-39, P-38, F2A and F4F-3 (at least initially -and no drop tanks on the F2A) may have been due to greater focus on internal fuel capacity alone. The P-40C got its drop tank not to extend range, but to match the range the P-40B had managed on internal fuel. The XP-39 had originally carried 200 US gallons in its wings but the later self sealing cells nearly cut that in half. The P-38 took a major cut as well, though still managed a very long range. (still obviously much improved by drop tanks)

However your idea about a "fighter bomber" version of the Fw 187 also stands up. The early German radios for single seat fighters were crap (so were most other countries). The ability to communicate with base and ground troops was minimal at best at any but short ranges. Pretty much a single frequency set. One reason for the 2nd crewman was to operate the long range radio. This also had multiple frequencies or was tunable to different frequencies. For a close support plane to depend on signal panels laid out on the ground (large arrows made of sheets of cloth) for targeting instructions is hardly the way to go. The guy in the back of the Ju 87 did more than wave that MG 15 around.

Ability to carry the second crewman was significant and a trade-off to consider in the long range patrol or escort role as well. (the performance trade-offs may have been worth the added communication abilities)

But the requirement for said crewman to also be an effective gunner (rather than relying on maneuverability, acceleration, and speed of a fighter) is another matter and tied to RLM doctrine, at least for the Zerstörer role. After all, the Mosquito fighter-bombers still carried a dedicated radio operator. Americans abandoned the 2-seat day fighter concept with the P-30, but considering 2-seat variants of the P-38 earlier (at least for specialized roles where the radio equipment was especially advantageous) may have been worthwhile. Even as an interceptor, the better radio performance may have been significant and have solid advantages over the Bf 109 or early 190 even with a similar armament. (with better later radios, single seat variants would make much more sense -along with more powerful engines, heavier armament, etc)

 

[wiking85]

The second seat in an escort fighter is actually pretty helpful, especially given that it was rearward facing, as the second pair of eyes could scan the horizon to the rear and warn of looming threats while also handling the radio.

 

[stona]

First testing of drop tanks by the USAAF in the ETO wasn't until July 1943. The 108 gallon metal tank wasn't even tested until September 1943. It took a long time to sort out. Attempts to use ferry tanks in August were not a success. I'm not sure that drop tanks were used operationally anywhere by the USAAF until late 1943, not really relevant to a thread about 1930s fighter bombers.

Everyone dropped the ball on drop tanks. The Luftwaffe introduce the plumbing on the Bf 109 E-7, just too late for the BoB where it would have been useful to put it mildly. The British did no better in 1941/2 either, falling into the same trap as the Luftwaffe had earlier as the RAF 'leant forward' into NW Europe.

The Fw 187 was designed as a single seat fighter, then beefed up as a two seat Zerstorer. As far as I know no Fw 187 was ever built or tested with external stores, be they bombs or drop tanks. I've never seen a photograph or report showing that any Fw 187 was ever so equipped.

Drawings of proposals for a dive bomber (BMW 801 powered) and a 'Kamfzerstorer' (DB 605 or BMW 801 powered), the latter capable of carrying 2,000Kg of external stores exist, but they are just drawings.
It is impossible to draw any firm conclusions from such proposals. This returns us to a problem that crops up time and time again when aircraft like the Fw 1897, which were built in very small numbers and never entered the service of any air force in a meaningful way, are discussed. People can draw very different conclusions from the limited data available. There is NO solid data for a Fw 187 fighter bomber or 'Kamfzerstorer' because it NEVER got off the drawing board.

Cheers

Steve

 

[Shortround6]

"The XP-40 flew for the first time on October 14, 1938, with test pilot Edward Elliot at the controls. Armament was two 0.50-inch machine guns located in the upper fuselage deck and synchronized to fire through the propeller arc, standard armament for US pursuit aircraft at the time. Wing racks could be fitted for six 20-pound bombs."

So the initial prototype at least had provisions for installing bomb racks similar to the P-36. Perhaps some of the production P-40s retained such provisions as well, but weren't ever fitted? (prior to the adoption of the belly shackle, the bomb load limit was pretty light, even compared to the USN's 200~232 lbs)

Perhaps but no mention is made of bombs for the P-40 no letter and the P-40B. Ammo for the cowl .50 cal guns was increased from 200rpg to 380rpg. a 108lb increase in ammunition load. What is puzzling for the ground attack story of the P-40 is 1, the Army had decided it wanted radial engines for ground attack planes back in the early 30s.

and the army stayed with air cooled engines for "attack" planes until the A-36.

2, the army had pretty much standardized on four .30 cal mgs for attack planes from the planes pictured though the early A-20s. Two synchronized .50s aren't really good strafing armament.

3, the bomb load of six 20lb bombs was about 1/3 the bomb load of the P-35 which went into service in 1937 with final deliveries in 1938.

AS a fighter to protect/escort the attack planes it makes more sense and what makes the most sense is that it was simply the best "altitude" fighter the Army could get at the time with the Allison engine using the highest gear ratio and FTH available at the time the planes were initially ordered and production started and the 'story' about the P-40 being designed/intended for ground attack is just wrong. What they were used for 2-3 years after being ordered is another story.

Even assuming the advantages of a multi-role aircraft were ignored, the Fw 187 still had the advantages of being faster than the Ju 88 or Do 215 while using stocks of existing older Jumo 210 engines. (possibly using the Bramo engines of the Do 17 as well) Though Focke Wulf never attempted using alternate engines, Bramo and (especially) Jumo 211 engines would seem quite useful. (the Bramo would help more for climb and take-off performance than top speed, so attractive for potential high takeoff weights of bombloads as well as reduced engine vulnerability)

We get into some real "what iffies" here. Will the Fw 187 be faster than the Ju 88 or Do 215 if it is carrying external bombs and the and the Ju 88 or Do 215 are carrying internal? With about 1400hp for take-off being available on an 11,000lb (clean) aircraft how much of a bomb load can you hang off it before you have to start cutting back on filling the fuel tanks? What kind of bomb load are you interested in? A single 250kg or 500kg bomb? four 50kg bombs? eight 50kg bombs? one big bomb has a lot less drag than a bunch of little ones. Using the Bramo 323 gives you power but at the cost of carrying around a pair of masonry sanitary facilities as far as drag goes. The Bramo 323 was bigger in diameter than a R-2800 and about 10mm smaller than an R-2600 (depending on models. While the Jumo 210 installation on the FW 187 may not have been all that good sticking a pair of 16.3 sq ft engines on the FW 187 is going to be like flying around with flaps permanently down. The DO 215 picked up around 60-65mph over the Do 17z and all that speed did NOT come from just the increase in power.

On the issue of American 1930s fighters having both bomb AND drop-tank carrying ability that disappeared with the P-40, P-39, P-38, F2A and F4F-3 (at least initially -and no drop tanks on the F2A) may have been due to greater focus on internal fuel capacity alone. The P-40C got its drop tank not to extend range, but to match the range the P-40B had managed on internal fuel. The XP-39 had originally carried 200 US gallons in its wings but the later self sealing cells nearly cut that in half. The P-38 took a major cut as well, though still managed a very long range. (still obviously much improved by drop tanks)

All this is true but one wonders why it took so long to bring /external/drop tanks back since they had been so common on early 1930s aircraft. Even the attack planes pictured had them.

Ability to carry the second crewman was significant and a trade-off to consider in the long range patrol or escort role as well. (the performance trade-offs may have been worth the added communication abilities)
But the requirement for said crewman to also be an effective gunner (rather than relying on maneuverability, acceleration, and speed of a fighter) is another matter and tied to RLM doctrine, at least for the Zerstörer role.

From the German view point, once you have a rear seater, and a large radio and oxygen equipment and...... adding a lousy 10kg gun and mount and 1/2 dozen or so 75 round magazines is no big deal from a weight stand point. drag increase from trying to give the gunner a a decent field of fire may be more important.

ANd you are correct, radio development did not stay static and later radios (or different countries radios developed at different rates) affected requirements. British radios for Fighters during the BoB could switch between 4 different channels I believe from the cockpit? 109 pilot had one frequency once he took off? This is in addition to range questions.

 

[stona]

British radios for Fighters during the BoB could switch between 4 different channels I believe from the cockpit?

The HF TR9 radio fitted to many British fighters, even during the BoB operated on one channel. The VHF TR 1133 started to be fitted in June 1940 to some Spitfires, but the conversion was on going throughout the BoB. With the TR 1133 and then TR 1143 there were four channels selectable on a push button panel, by the pilot.

IIRC the FuG 7 did indeed operate on one preset frequency, but I can't check at the moment.

Cheers

Steve

 

[Shortround6]

Thank you.
This brings into question what the "fighter bomber" will be used for.

Battlefield support/army co-operation(attacking strong points holding up advance or breaking up enemy attacks of troops/vehicles in the open.
Slightly further back 'battlefield support/army co-operation" as in the attack/suppression of enemy artillery positions/reserve deployments/near front line fuel-supply dumps.
Interdiction of enemy supply routes, rail lines, roads, bridges and other routes of supply close enough for the fighter bomber to reach.
Enemy airfield attack/suppression to stop the enemy from doing the same things back.
Strike missions against ships or more rear area fixed air fields (as opposed to temp or front line), harbours, major bridges, etc. Taking over from light/medium bombers.

We can leave out such things as P-38 mass formation level bombing for the most part

Just like "strategic bombing" the weapons(bombs) and weapons loads (bomb loads) thought to be useful in the mid/late 30s were shown to be woefully lacking in actual combat in 1939/40/41. Single or paired 100-110lb bombs or 5-6 20lb/10kg bombs just didn't pack enough punch to make the missions worthwhile. Later P-40s were flying with six 250lb bombs instead of six 20lb bombs.

AS for a Fw 187 in 1039/40 using Jumo 210 engines, you have a plane with a similar wing area to a Ju-87, a bit more power but heavier empty and loaded weights (before bombs added) and costing more (you don't get two 20 liter V-12s for the price of one 33 liter V-12). As a sort of dedicated 'light' bomber it really doesn't make much sense unless also adopted as a fighter and with the Jumo 210 engines that wasn't going to happen.

 

[stona]

Thank you.
This brings into question what the "fighter bomber" will be used for.

Despite some early attempts by the British to use them as the Germans had done against pin point targets (airfields, electrical installations) the fighter bomber developed as a tool to support the Army. For the British it started with the Desert Air Force in 1942 and evolved into the complicated system in place by the time of the D-Day landings. Later they did operate further behind the front in an armed reconnaissance role, attacking targets of opportunity which in 1944/5 meant anything that moved on land, sea or in the air.
As far as I can tell the Americans developed a similar system, though with notable differences. The Americans also didn't have to contend with the inter service rivalry that so dogged British development, mainly at senior level.
I think the fighter bomber as developed in WW2 as literally a fighter that could carry bombs, evolved from the inability of light bombers, Army cooperation aircraft, and in the case of the Germans their principal dive bomber, to survive in contested air space. It was an expedient brought about by circumstance. It's also why none of the combatant air forces mentioned above had a suitable aircraft for the role before the war.
Cheers
Steve

 

[buffnut453]

Steve,

I think all those points are valid. However, Shortround's comment about Governments not funding bombers if fighters can carry bombs has a grain of truth to it. During the interwar period, many believed that "the bomber will always get through", a concept staunchly supported by advocates of the strategic bomber because it was that weapon which largely drove the formation of independent air forces. As late as the early 1930s, fighters were the Cinderella component within many air forces. Allowing fighters to carry bombs would divert resources from the "real" function of air forces which was the delivery of strategic bombing.

One side issue is the relative performance of fighters in the interwar period. Many fighters were simply incapable of carrying more than just guns until the advent of the "modern" monoplanes of the Hurricane, Spitfire, P-36 ilk. No point specifying a role for a fighter bomber if the available fighters can barely carry 4 guns into the fight.

 

[stona]

One side issue is the relative performance of fighters in the interwar period. Many fighters were simply incapable of carrying more than just guns until the advent of the "modern" monoplanes of the Hurricane, Spitfire, P-36 ilk. No point specifying a role for a fighter bomber if the available fighters can barely carry 4 guns into the fight.

I think that is not only a pertinent point but goes to the heart of the problem. The British struggled through the 1930s to get a S/E fighter capable of lifting four 20mm cannon, let alone bombs.

Cheers

 

[Shortround6]

Many of the minor countries used "fighter-bombers" in the 20s and 30s because they weren't going to get very many planes to begin with. Perhaps a few squadrons total, some some sort of multi-role tasking had to go on. The Navies with Aircraft Carriers were also much more interested in multi-role aircraft as the Aircraft Carrier, operating hundreds if not thousands of miles from an aircraft resupply point, had to have a maximum of flexibility in it's fixed (mostly) number of aircraft embarked. AS in Courageous at one point having "16 Flycatchers would serve alongside 16 Blackburn Ripons and 16 reconnaissance aircraft." The Flycatchers having "provision" for four 20lb bombs under the wing. The Flycatchers were replaced by Hawker Nimrods which kept the provision of the four 20lb bombs. With a pair of synchronized .303 Vickers guns for armament even four 20lb bombs could be useful against Chinese pirates on wooden junks.

The budget problem may not have been Hurricanes vs Whitleys in 1937 but Hurricanes vs Blenheims or Hurricanes vs Lysanders. For the US it might have been P-39/40s with bomb racks vs the twin engine attack bomber the Army wanted.
The first contest between the Douglas DB-7, the Stearman X-100, the Martin 167 (Maryland) and the North American NA-40 was held about the same time as the 1939 fighter contest that selected the P-40. Spring of 1939. Initial specification had been issued March of 1938. Congress was over 2 years from opening the flood gates of money from the treasury. Remember the Army (and congress) bought B-18s because they were cheaper than B-17s and Boeing was making A-20s under subcontract to Douglas in 1940 because they had spare factory space due to a lack of orders for B-17s. Even the American congress could figure out that the P-40 couldn't replace the B-17 but the army "attack" planes were supposed to take part in the "land battle" including laying smokescreens. Let too many congressmen know that single engine fighters could carry 500lbs worth of bombs and the twin engine "attack" plane could only carry 1200lbs (initial specification) and there might have been a lot of arguing about using 'cheap' fighter bombers instead of 'expensive' twin engine bombers. Please Remember that in the Spring and Summer of 1939 the Army owed Allison over $900,000 for work already done and this debt had NOTHING to do with engines for the production P-40s. (engines for YP-37 and Airacudas and development, etc).

 

[Shortround6]

I think that is not only a pertinent point but goes to the heart of the problem. The British struggled through the 1930s to get a S/E fighter capable of lifting four 20mm cannon, let alone bombs.

They might have had better luck if they had gotten their thumbs out of their bums earlier on the constant speed props. Or had priority over bomber production for the existing supply of props.

From Mike William's web site: Hurricane L-2026 Trials Report

Aeroplane.....Weight lb......Airscrew....Take-off run 'yds' zero flap......Distance to clear 50 ft. screen (yds)
L.2026...........6316.............Rotol.............240................................ 420
L.2026...........6750.............Rotol.............280 ................................465
L.1547...........6363.......2-pitch metal........280................................ 480
L.1547...........6040.....Wooden fixed pitch..370................................ 580


Hurricane can take-off in 100yds less distance while weighing 700lbs more than with the fixed pitch prop.

 

[GregP]

From the other thread, I'm not sure the AR 240 had any issues that couldn't have been solved satisfactorily.

The main issues seem to have been marginal stability and that should not be "unfixable" for any design. The performance potential was certainly there and I think it could have been a good one ... but I'm also not sure it would have been, of course. But stability issues are correctable. perhaps it also had system or airframe problems that, taken together with the rest, made it seem not worth the effort.

In fact, I have bever seen a choerent explanation of why they didn't proceed with it. The closest I can come with an educated estimate is that the design team was asked to fix the stability issues and was given time to do it but they didn't succeed at it. If that happened, it might be the end of it in a wartime situation despite the obvious potential.

In wartime asd in peacetime, politics also plays a part and the third Reich was fond of letting people and companies "fight it out." Perhaps Arado was beaten in a conderence room.

 

[buffnut453]

They might have had better luck if they had gotten their thumbs out of their bums earlier on the constant speed props. Or had priority over bomber production for the existing supply of props.

When were constant speed props added to the Bf109? I thought it only came in with the E-4 variant which doesn't put it too much ahead of the constant speed prop installation on the Spitfire MkII. If my timeline is correct, I see little opportunity for "them" to get their thumbs out any sooner than "they" did in reality.

As for your second point, that's the whole issue in examining this period. The interwar period was dominated by the bomber obsession. The interwar senior officers were the flag rank officers in the late 1930s...odds of shifting the needle on priorities to create an entirely new aircraft role of fighter-bomber? Pretty slim, methinks.

As t

 

[kool kitty89]

Perhaps but no mention is made of bombs for the P-40 no letter and the P-40B. Ammo for the cowl .50 cal guns was increased from 200rpg to 380rpg. a 108lb increase in ammunition load. What is puzzling for the ground attack story of the P-40 is 1, the Army had decided it wanted radial engines for ground attack planes back in the early 30s.

Aside from the low/medium altitude tactical escort and intercept role, might it not have been considered that the combination of heavy and light machine guns were more effective anti-material/personnel and anti-light armor weapons than those 20 lb bombs? (I'm not sure when AP/I rounds were first introduced on the .50 Browning, but that would have been a significant factor)

and the army stayed with air cooled engines for "attack" planes until the A-36.

This is somewhat curious since continued development of production of the P-36 would have fit that role and (while not as fast as the P-40) would at least have been much less vulnerable and capable as a fighter than contemporary attack planes.

And even with the more limited (typical) 250 lb bomb capacity of the P-40C's belly rack, similar mountings on the P-36 would have been very useful.

2, the army had pretty much standardized on four .30 cal mgs for attack planes from the planes pictured though the early A-20s. Two synchronized .50s aren't really good strafing armament.

Might the increased armament on the P-40B be at least in part for ground attack and not just air to air performance? (insisting on 4x LMGs in the P-39's wings against Bell's own wishes seems like it may have been for strafing as well, particularly with the ammo capacity and firing time far exceeding the nose guns)

AS a fighter to protect/escort the attack planes it makes more sense and what makes the most sense is that it was simply the best "altitude" fighter the Army could get at the time with the Allison engine using the highest gear ratio and FTH available at the time the planes were initially ordered and production started and the 'story' about the P-40 being designed/intended for ground attack is just wrong. What they were used for 2-3 years after being ordered is another story.

If ability for tactical/close support use AND high altitude performance were the main considerations, might not a 2-stage R-1830 powered P-36 be more attractive? (slower below 15,000 ft, but likely better power/weight, better climb at most altitudes, shorter take-off run, better able to cope with weight of external stores, and significantly better acceleration/climb/speed around 20,000 ft, and potential further gains once the fan-cooled cowling set-up of the XP-42 were refined) More akin to the Hurricane II with much better high speed control and dive acceleration.

Granted, unless they later switched to the R-2000, a radial engined Hawk would dead-end with the 2-stage R-1830 where the V-1710 saw considerable increases in emergency power as well as unapproved overboosting. (I'm not sure if such was ever attempted on the R-1830)

A single 250kg or 500kg bomb? four 50kg bombs? eight 50kg bombs? one big bomb has a lot less drag than a bunch of little ones.

Given the Ju-88 had to resort to external racks to carry any large bombs would seem to be the area a fast fighter-bomber/dive bomber would be attractive. (and much faster and longer ranged than the Ju-87)

A 500 kg capacity seems realistic, perhaps 1000 kg with additional modifications to later models. Part of that is just speculation using the P-38 as a comparison. (with the P-38F rated for 2x 1000 lb bombs)

Using the Bramo 323 gives you power but at the cost of carrying around a pair of masonry sanitary facilities as far as drag goes.

They certainly would have been inferior to the DB-601 or Jumo 211, and less fuel efficient than the Jumo 210, but external load carrying ability should have been significantly better than the 210 along with maximum climb rate, take off performance, and perhaps a more modest increase in top speed. (obviously much less than the DB 600 or 601 offered, but perhaps enough to put it slightly ahead of the Bf 109 and well ahead of the DB powered Bf 110 -and as a bomber, much faster than the Ju 87, though possibly not much advantage in speed over the 215 or 88 carrying internal bombs -more an advantage after dropping bombs and certainly compared to carrying external bombs)

The drag situation may have been similar or somewhat better than the case for the XF5F with its big R-1820s.

The most logical role is as a fighter/interceptor, and most of these suggestions also would be competing with possible fighter-bomber configurations for the 110 itself. (on top of the bomber-destroyer role) But while performing far better on similar engines, the airframe still should allow reasonably competent performance with older/lower priority engines that were available in existing stock ending their production runs soon. In the Jumo 210's case, it would pretty much be limited in use for the Bf 110B which was extremely poorly suited to active deployment and mostly useful as an advanced trainer. The Bramo engines were still useful for transports and patrol aircraft, and the only real advantage of the Fw 187 on either of those lesser engines is logistical availability. (less attractive as the main intended powerplants and more as selling points of being able to still function in useful roles in spite of shortages of the DB-601 or Jumo 211 -though added advantage of damage resistance in the Bramos)

Competing with the Ju-88 and Do 215 seems less reasonable than offering a potent alternative to the Bf 110 (already failed due to politics), Ju 87, and quite possibly displacing development of the Hs 129 entirely as well. (with ventral gun pods on the centerline better than the underwing mountings on the Ju 87 and much faster and longer ranged than either that or the Hs 129 -honestly, I'd argue the Soviets would have been better off with armored twin engine heavy fighter/bombers in place of Il2s as well, or the british with over the Hurricane IV -even if half the number of individual aircraft, but that's probably getting too far afield given those are early 1940s designs/requirements with anti-armor/anti-rail/anti-shipping cannon)


Additionally, given opposite-hand rotating engine models were never forthcoming in Germany, the advantage of eliminated torque with counter-rotation is mostly moot. (barring changes to engine production)

All this is true but one wonders why it took so long to bring /external/drop tanks back since they had been so common on early 1930s aircraft. Even the attack planes pictured had them.

Increasing altitudes may have been an issue as well, given the need for pressurized fuel tanks and such problems less likely to arise with tanks used on biplanes. The P-40C and Bf-109E-7 may be some of the earliest operational combat aircraft in WWII with properly combat-capable drop tanks.

From the German view point, once you have a rear seater, and a large radio and oxygen equipment and...... adding a lousy 10kg gun and mount and 1/2 dozen or so 75 round magazines is no big deal from a weight stand point. drag increase from trying to give the gunner a a decent field of fire may be more important.

Further cramping the already limited space for the radio operator could be a concern as well, hampering their ability in the radio capacity as well as possibly being less effective as a lookout. (more distracted, less attentive, and possibly a more obstructed field of vision due to the gun mounting -at least compared to the same area being glazed over rather than fared over with aluminum)

 

[kool kitty89]

AS for a Fw 187 in 1039/40 using Jumo 210 engines, you have a plane with a similar wing area to a Ju-87, a bit more power but heavier empty and loaded weights (before bombs added) and costing more (you don't get two 20 liter V-12s for the price of one 33 liter V-12). As a sort of dedicated 'light' bomber it really doesn't make much sense unless also adopted as a fighter and with the Jumo 210 engines that wasn't going to happen.

Aside from the cost of the Jumo 210, given production is slowing down/ceasing anyway, it would be a short-term powerplant with cost of production already fixed. Logistically speaking, it's a matter of where to best allocate those supplies of engines. (fuel consumption might be a real operational cost consideration though, and single vs twin engine training)

Speed range are advantages as a fighter or fighter-bombeer/attack ship, but doctrine focusing on close air support and at short ranges would make the latter less appealing, as would the lacking cooperation with the navy (as a long range patrol fighter-bomber would be useful there too).

It seems like most of the practical advantages and uses in the foreseeable roles in 1937-39 would have been compromised by politics. I'm not sure the idea of external gun pods for strafing or cannon pods for anti-armor/vehicle/rail/shipping would be attractive or obvious at the time either. (or even an MG-FF pack added for anti-bomber strikes)

And any direct order from Hitler with particular interest in the Fw 187 would be somewhat by chance of the right sort of attention given by those in direct contact with him. (in as far as an Me 262 type situation, which granted was a Messerschmitt design and thus likely to have more sway with the Nazi elite anyway)


In the line of thinking though, in terms of politics of the high ranking LW officials early war, Udet did seem to be one of the more reasonable (if obsessed with dive bombing) and was apparently mostly wary of a twin engine design failing to compete with single engine contemporaries in fighter vs fighter combat. But with the idea of a dive bombing capable fighter there, he may have taken more interest on top of the potential for a sheer high-speed fighter (he was after all intrigued enough by the He 280 to make an agreement with Heinkel in spite of his reservations with the radical design). Of course to BE high speed, they'd have needed access to the high performance engines, especially earlier in testing to make the full potential obvious. (that is something that appealing to Udet may have benefited closer to the later Heinkel negotiations)

Finally, Udet was known for personally test-flying prototype aircraft, and allowing him to do so with the Fw 187 may have been the best way to free him of misgivings over the performance as a fighter. (particularly if allowed to perform a mock dogfight -for the early prototypes, the Jumo 210 would still likely be used due to across the board scarcity of alternatives in 1937, but against the contemporary production 109s it would have been dramatically superior) Still, the advantage of adding the second crew member would be significant.

Let too many congressmen know that single engine fighters could carry 500lbs worth of bombs and the twin engine "attack" plane could only carry 1200lbs (initial specification) and there might have been a lot of arguing about using 'cheap' fighter bombers instead of 'expensive' twin engine bombers. Please Remember that in the Spring and Summer of 1939 the Army owed Allison over $900,000 for work already done and this debt had NOTHING to do with engines for the production P-40s. (engines for YP-37 and Airacudas and development, etc).

Would that have been a bad thing, though? At least in as far as any fighters actually capable of managing competitive ranges with close to the same number of bombs (ie at least double the number of aircraft). Granted, these latter points are what Congress may have overlooked as well given the B-18 vs B-17 scenario. (they also likely wouldn't be fond of the P-38's cost -which itself may have been a very potent fighter bomber early-war, but production delays and other problems prevented that anyway, as was also discussed somewhat recently)

Still, fighter bombers with a number of bombless fighter escorts as the primary tactical bombing force may have had overall advantages in flexibility and cost effectiveness compared to early war light bombers. (though again, 2-stage P-36s may have been better overall in this role)

From the other thread, I'm not sure the AR 240 had any issues that couldn't have been solved satisfactorily.

The main issues seem to have been marginal stability and that should not be "unfixable" for any design. The performance potential was certainly there and I think it could have been a good one ... but I'm also not sure it would have been, of course. But stability issues are correctable. perhaps it also had system or airframe problems that, taken together with the rest, made it seem not worth the effort.

In fact, I have bever seen a choerent explanation of why they didn't proceed with it. The closest I can come with an educated estimate is that the design team was asked to fix the stability issues and was given time to do it but they didn't succeed at it. If that happened, it might be the end of it in a wartime situation despite the obvious potential.

I'm not so sure it would have been that much better a design overall than the Fw 187 itself, better than the Me 210, 410, He 219, and Ta 154 yes, perhaps a better heavy day interceptor (the 187 would need to resort to cheek/belly pod mountings for a really heavy armament) and night fighter better than hypothetical or real Ju 88 derivatives with similar engines, but compared to a late-war Fw 187 with compact radar? I suppose it at least would allow a roomier position for the radar operator and more flexible options for armament. (Still, the Fw 187 seems like it might manage to be similar to the P-38M, and given the altitudes of night bombers, DB-605AM engines would likely be perfectly acceptable -reserving DB-603s for Fw 190s would seem more sensible at that point, though prior to the AI radar coming online, diverting 603s to Ju 88s and possibly Ar 240s would make plenty of sense, though 603s to 190s and more 801s to twins might be more useful)

As to the Ar 240's development cycle, the other explanation I've seen is shift in development emphasis to the Ar 440 to correct the flaws and produce an even more advanced aircraft. This may have set things back considerably compared to more modest alterations to correct the existing design and ended up much more pie in the sky like so many follow-on developments of canceled designs. (this goes for both aircraft and engines -Heinkel's order to cancel engine development and direct all work to a follow-on class 2 design -the ill fated HeS 011- comes to mind as does the ever shifting design requirements of the Ju 222, the DB-603's temporary cancellation is somewhat in line with this too given the DB-604's development, but I'm not sure the 604 wasn't halted along with the 603)

During the interwar period, many believed that "the bomber will always get through", a concept staunchly supported by advocates of the strategic bomber because it was that weapon which largely drove the formation of independent air forces. As late as the early 1930s, fighters were the Cinderella component within many air forces. Allowing fighters to carry bombs would divert resources from the "real" function of air forces which was the delivery of strategic bombing.

True for strategic bombing, but not tactical and Germany was all about tactical bombing and close cooperation with advancing ground forces. This makes fighter-bombers very attractive for similar reasons to dive-bombers, but the generally short range of operations required and apparent interest in converting level bombers to dive bombers yet not fighters makes the Fw 190 less appealing.

Jabo 109s should have materialized sooner as well, hell, using the larger 109T wing might have meshed well with that role too. Mating Jumo 211s to 109 airframes may not have been ideal, but might have still made for aircraft with advantages over the Ju 87 and quite possibly still a potent enough fighter to out-perform anything short of the Spitfire. (for that matter, if the larger wing proved to decrease landing accidents, that combined with the improved turning ability may have outweighed increases in drag even on the DB powered models, modifying the larger wings to include fuel would have been another consideration -especially with losses in range when carrying a bomb)

That's not to say the Ju 87 should have been supplanted pre-war. The lower wing loading and general flight characteristics (including accurate dive bombing) for the early stages of the war made it very attractive, but hedging their bets with an earlier emphasis on dive bomb-capable fighters could have made phasing it out practical and attractive much sooner. (employing the aging 109, larger-winged in a more Hurricane/P-40-like role including possible underwing-mounted heavy cannon may have been better suited than the Ju 87 as well)

When were constant speed props added to the Bf109? I thought it only came in with the E-4 variant which doesn't put it too much ahead of the constant speed prop installation on the Spitfire MkII. If my timeline is correct, I see little opportunity for "them" to get their thumbs out any sooner than "they" did in reality.

I think the point was less constant speed props, and more any sort of useful variable pitch props. The fixed pitch 2-bladed wooden propellers were hindrances to all the British fighters using them, be it the sptifire, hurricane, or even the Gladiator.

 

[Shortround6]

They were using variable pitch propellers (at the least) on 109Cs. Variable pitch doesn't always mean constant speed. Variable pitch can mean two pitch, course and fine, with nothing in between. It can mean the pilot can, by means of a control, adjust the pitch anywhere between the two limits. Constant speed propellers have a governor that automatically adjust the pitch to keep the propeller turning at a preset value. Translation of books from one language to another often confuse the terms much like two speed and two stage superchargers. Perhaps the E-4 got a different type of propeller control for the same mechanism? Or different control lever arrangement? When did the Germans go to a single lever control? one lever to control the rpm, boost, and prop pitch?

Hamilton Standard introduced a constant speed propeller to the commercial market in 1935. They had introduced their variable pitch (2 pitch ?) prop in either 1930 or 1932. They were certainly not the first to build such propellers but were the first to achieve commercial success. The idea (and experimental) variable pitch propellers go back to before WW I and pictures show an S.E. 5A with an experimental variable pitch prop (continuously variable?) in 1917. The British had fooled around with several other designs of variable pitch props in the early 20s but all had faults or problems that could not be overcome at the time. This soured the air ministry on variable pitch props and it took a lot time and success by other countries (and a few forward thinking British companies) to change the air ministry's collective mind. It doesn't do a lot of good to licence a design if the air ministry won't buy them. The Air Ministry was changing it's mind by 1939 (if not a bit before) but by then they were facing a rapid increase in production of all types of aircraft and the demand exceeded supply (due to low orders in the mid 30s) for a while until the propeller factories could be expanded.
The US had been using 2 pitch propellers on the Boeing 247 airliner and others in 1933.
Hamilton Standard introduced the Hydromatic propeller in 1937 and this allowed full feathering of the propeller instead of setting the prop on the bad engine to course pitch and was a major change in twin engine safety.

 

[GregP]

Some were ground-adjustable and some were adjustable from the cockpit. Constant-speed came later. The best coinstant-speed I know of was the Hamilton-Standard unit. The big round "spinner" was an oil reservoir and it worled VERY well and still does on our birds at the Planes of Fame.

The prop on the Japanese Zero was a legal, license-built H-S unit. Ours on the A6M5 Model 52 Zero is virtually interchangeable with US units but it stays on the Zero. The blades are identical with US units, as a license-built variant SHOULD be. All in all a very good and reliable unit.

Constant-speed props were the best performance improvement you could make at the time .... until flush rivets came into vogue and 1,500 HP engines showed up. You got more acceleration, better climb, shorter takeoff, and higher speed ... all at the same time. The only real performance-changer left to be invented was better streamlining (lower drag)and reversible-pitch props ... until jets and turbo-props came along.

 

[stona]

I think the point was less constant speed props, and more any sort of useful variable pitch props. The fixed pitch 2-bladed wooden propellers were hindrances to all the British fighters using them, be it the sptifire, hurricane, or even the Gladiator.

Exactly, and earlier Bf 109s did have a variable speed airscrew. The control, like a rocker switch, was positioned on the throttle lever and the pitch indicator was the dial at the lower right of the instrument panel, sensibly next to the engine tachometer.

Whilst a manually controlled variable pitch unit is much superior to a fixed or two pitch system it did need training to be used correctly. There are accounts from the latter stages of the BoB which show that some of the Luftwaffe's inexperienced replacement pilots struggled to operate the system even when flying in formation, never mind under the stress of combat. In this sense a constant speed unit gives an advantage.

Cheers

Steve

 

[Shortround6]

Aside from the low/medium altitude tactical escort and intercept role, might it not have been considered that the combination of heavy and light machine guns were more effective anti-material/personnel and anti-light armor weapons than those 20 lb bombs? (I'm not sure when AP/I rounds were first introduced on the .50 Browning, but that would have been a significant factor)

We are getting into a somewhat tangled timeline between not only different fighters and models but different types of aircraft. Fighters under consideration in Jan 1939 were "Lockheed XP-38, the Bell XP-39, the Seversky/Republic XP-41 (AP-2) and XP-43 (AP-4), and no less than three planes from Curtiss, the H75R, XP-37, and XP-42." + the XP-40. The XP-38 and XP-39 used turbos as did the XP-37 and XP-43. The XP-41 and the H75R both used two stage R-1830s.
The army needed reliable fighters and it needed a lot of them in a hurry. This rather ruled out the turbo planes as the army estimated they were two years away from being usable in squadron service. Army underestimated the time needed on this one. Their experience with the two aircraft powered by 2 stage R-1830s (the XP-41 and H75R) doesn't seem to have impressed them. Please remember that these were essentially experimental engines at the time and P&W didn't even have a two speed single stage engine in service. The extended shaft R-1830 in the XP-42 suffered from both vibration and cooling issues. Something else is that the Army wanted around 500 fighters (it ordered 524 P-40s initially) and Seversky had built under 100 planes in the companies existence and Bell had built under 20. That left Lockheed and Curtiss as established mass manufacturers. Since the P-36, XP-37, H75R, XP-42 and XP_40 all used essentially the same wing, tail and landing gear and Curtiss had built 210 P-36s and had orders for 200 Hawk 75s for France on the books in the spring of 1939 while Lockheed, despite building several hundred twin engine Airliners and Hudsons had no production set up for the P-38. Selection of the P-40 seems to have been a no-brainer, delivers to squadrons could start months if not a year earlier than most of the other contenders. The Army still had a few squadrons flying P-26s at this time.

Getting back to the subject of your sentence. The .50 cal had received an improvement in ammo in the mid 1930s when velocity was boosted from 2500fps to about 2900fps (and even the old ammo had AP rounds but their were no combined AP and incendiary rounds, the incendiary projectiles were a separate round) due to improved propellant. However the .50 never took to synchronization well and the Fuselage mounted guns usually fired at between 400-500rpm rather than the 600rpm of the unsynchronized guns at this time. This is in comparison to the 1100-1200rpm the .30cal guns were achieving. While a single .50cal round was much more destructive than a .30 cal round the low rate of fire of the fuselage mounted guns meant that the combined rate of fire was about 15 rounds per second. Chances of hitting were actually fairly low and the attack planes with four .30s were firing 70-80 rounds per second.

Might the increased armament on the P-40B be at least in part for ground attack and not just air to air performance? (insisting on 4x LMGs in the P-39's wings against Bell's own wishes seems like it may have been for strafing as well, particularly with the ammo capacity and firing time far exceeding the nose guns)

It could be but again the cowl mount .50s didn't have a high rate of fire so hitting chances were low. The US had NOT done a lot of testing with the .50 in flight and several problems cropped up quickly. One was that initial testing had been done with less than full belts in the ammo boxes and the weight/drag of the longer belts slowed the rate of fire and increased jams. The Army tended to over spec armament on a lot of their fighters and proposed fighters at this time.

Granted, unless they later switched to the R-2000, a radial engined Hawk would dead-end with the 2-stage R-1830 where the V-1710 saw considerable increases in emergency power as well as unapproved overboosting. (I'm not sure if such was ever attempted on the R-1830)

We get into production problems here, how 'useful' a up engined radial Hawk might have been is certainly subject to debate but every radial engine Hawk built is a P-40 NOT BUILT. The R-2000 doesn't show up as a production engine until the beginning of 1942 (and then at the rate of a few dozen per month) at which time P-40s are being fitted with not only Merlin engines but the 1325hp model Allison is not that far off. 600 P-40Ks having been ordered in Oct of 1941. Granted P&W could probably have put a bit more emphasis on R-2000 production had demand been there but it wouldn't have shown up much sooner. R&D was going into the R-2800 and it's three basic configurations. Since a P-40 was about 30-40mph faster than a radial powered Hawk below 15-20,000ft the radial Hawk has a disadvantage right from the start. Over boosting air cooled engines never worked very well as they were already operating close to max temperature. The liquid cooled engines could operate for several minutes as the gallons of coolant heated up. Over boosting of aircooled engines almost always involved water/alcohol injection.

Given the Ju-88 had to resort to external racks to carry any large bombs would seem to be the area a fast fighter-bomber/dive bomber would be attractive. (and much faster and longer ranged than the Ju-87)

They certainly would have been inferior to the DB-601 or Jumo 211, and less fuel efficient than the Jumo 210, but external load carrying ability should have been significantly better than the 210 along with maximum climb rate, take off performance, and perhaps a more modest increase in top speed. (obviously much less than the DB 600 or 601 offered, but perhaps enough to put it slightly ahead of the Bf 109 and well ahead of the DB powered Bf 110 -and as a bomber, much faster than the Ju 87, though possibly not much advantage in speed over the 215 or 88 carrying internal bombs -more an advantage after dropping bombs and certainly compared to carrying external bombs)

The drag situation may have been similar or somewhat better than the case for the XF5F with its big R-1820s.

It seems like you are shopping for missions to justify the aircraft, much like FW did in real life . Are you proposing a fighter bomber/tactical bomber for support of the army in combat, in which case long range is not needed (or even wanted) or a long range light bomber? The JU 87 offers the precision of dive bombing, at least until AA defenses get better. While low altitude fighter bombers did achieve much better results for number of bombs dropped than medium altitude level bombers they weren't as good as dive bombers.
Climb isn't just power to weight, it is surplus power after subtracting power needed for level flight so major changes in drag can suck up some of the higher power. Also which engines were available when? picking and choosing engines from different years to justify a possible use is a luxury the original FW company didn't have. The XF5F didn't fly until almost 3 years after the FW 187 (April of 1940) and had engines (and fuel) unavailable to FW in 1938/39.
BTW, according to one source the Bramo was a whopping 12mm smaller in diameter than an R-1820. 1388mm vs 1400mm. abut 0.3 sq ft smaller in frontal area. The R-1820 offered anywhere from 200hp more HP at take-off and low level to 60hp more 1000ft higher at altitude. And that is compared to the 2 speed Bramo engine without water injection. Single speed Bramos offer either good performance at low altitude or sort of medium performance. The single speed engine that offered 900hp for take-off was rated at 1000hp at 10200ft. However the climb rating was 720hp at sea level and 820hp at 14,000ft. Seems like the power is close to a Whirlwinds in a bigger/heavier/ much draggier airframe? Changing the gear ratio for low altitude gave 1000hp for take-off but the climb power ratings changed to 820hp at sea level and 840hp at 6600ft.
Was the 2 speed Bramo available in 1938/39?
Another BTW, the figures in wiki for the XF5F are way off if that is what you are going by, those are projected figures which were never reached and the plane never flew with armament installed.

 

[buffnut453]

I think the point was less constant speed props, and more any sort of useful variable pitch props. The fixed pitch 2-bladed wooden propellers were hindrances to all the British fighters using them, be it the sptifire, hurricane, or even the Gladiator.

I don't disagree but it was Shortround who specifically called out constant speed props. That said, having variable pitch sooner wasn't going to change fundamental issues in the design of fighters in Europe. Early war European fighters of all nations lacked the range and were typically of smaller size compared to their US equivalents. Both factors limit the adaptability of aircraft like the Spitfire and Bf109 into the fighter-bomber role. In the late-1930s, there was simply no envisaged role for fighter-bombers but the role evolved as the light bomber concept proved flawed and the need for CAS-type missions became increasingly significant. The Hurricane rather fell into that role once it became obsolete as a fighter.