WI more motor cannons were installed in fighter planes in 1930?

[riggerrob]

Consider that by the Battle of Britain, most air forces admitted that rifle-calibre machine guns were not powerful enough to shoot down modern, all-metal airplanes. Even 8 MGs firing .303 struggled to stop German bombers during the Battle of Britain. Most air forces scrambled to perfect 20 or 30mm auto-cannons to the point they were small enough and reliable enough to install in wings.

Another option was installing motor cannons that fired through the Center of the propeller shaft .... aka: motor-cannons.

OTL Russia and Germany used motor cannons extensively during WW2, but hardly any other combatants.

OTL Russia installed 20mm motor cannons in Lagg 3, Yak 1,3 and 9. Russia also flew hundreds (thousands?) of American-made Bell P-37 and P-63 with 37mm cannons. P-36 Airacobra had a unique engine installation behind the pilot with only armament, drive shaft and Propeller Speed Reduction Unit in the nose. The 37mm cannon only fired through the final PSRU. Russian pilots loved P-37 and downed hundreds of German airplanes with them.
Meanwhile Yaks were powered by Klimov V, inline engines that had been developed from Hispano-Suiza V12 engines. Klimovs' 20mm cannon lay between the cylinder banks and only fired through the PSRU.

Germany installed 20mm motor cannons in the thousands of Messerschmitt 109 single-seat fighters that were equipped by DB 600 series engines. Since DB 600 series were inverted V engines, the cannon nestled in between cylinder banks - below the crankshaft - and only fired through the PRSU. MG151 cannons downed thousands of Allied airplanes.

Hispano-Suiza built the first MC during WW1 when they installed a Lewis MG (.303) to fire through the PRSU of a V8, HS-36 engine that was mounted on a SPAD fighter. A later version included a 37mm cannon, but that had to be manually reloaded by the pilot (1 shot at a time).
By the onset of WW2, HS had developed V12 engines producing up to 1,000 horsepower and sporting HS 20mm auto-cannon firing through the prop hub.
The French built about 900 Moranes with HS motor cannon, but they did not participate in many WW2 battles.

WI other engine manufacturers could have modified their engines to accept motor-cannons?
Could you install a MC in a RR Merlin?
Consider how many different Merlin variants were developed and most of the changes were to induction systems.
RR Griffon?
Allison V-1710?
Radial engines ..... consider the transfer case on the R975 radial engine installed in M18 Hellcats. The transfer case displaced the drive shaft down to the outer circumference of that radial engine. If you install a motor cannon in any other radial, the prop shaft - and cannon - will stay on the centre-line but will be displaced up or down until there is sufficient clearance between cylinders. Try to picture the small Pobjoy radials built during the 1930s.

 

[Just Leo]

From War Thunder, the La-5 mounts two 20mm ShVAK over the 14 cyl Shvetsov. The Hispano didn't work with synchro, and Rolls Royce made a choice to value induction efficiency over a motor cannon. I can't imagine a cannon firing through a mighty Pobjoy Niagara.

 

[FBKampfer]

I don't think much would change. The US relied on larger banks of heavy machine guns anyway, but I digress.

But piston engines were on the way out in the late 1940's, and there would likely be very few and incredibly minor butterflies.

And as far as combat, you might actually reduce the effectiveness of planes like the Spitfire, or hellcat, or Fw 190.

 

[riggerrob]

Dear FBKampfer,

We can agree that Browning .50 calibre machine guns were only a minor improvement on the rifle calibre (.30") used by most other nations.

OTOH I disagree with your second point since 99% of WW2 airplanes were powered by piston engines.

As for your third point: by late war, Spitfires, Hellcats and FW 190 all had wing-mounted cannons. ...... but they could only carry the extra weight because they had more powerful engines.

My OP question was aimed more at early WW2 fighters with much smaller engines (1,000 horsepower range) that struggled to lift a few .30 cal. MGs.
Could more motor-cannons change the outcome of early WW2 battles?

 

[FBKampfer]

The .50 cal was actually quite effective. It would punch through armor, and engine blocks, and anything else solid in a way that 20mm HE rounds wouldn't.

Frankly, it would be pretty easy to take down an F-22 with .50 caliber rounds, the only problem is keeping it in guns for long enough when it's hauling ass at 1600mph.

But against WW2 aircraft, the .50 cal offered sufficient firepower in 6+ mountings for both snapshots and tracking shots. As per the USN, the M2 20mm was only 3 times as effective as a .50, however they were much easier to cram into aircraft.

And your argument has no grounds. The turbojet had arrived before the end of WW2, as had the gas turbine engine. Basically anything new post 1950 uses a jet or a turbofan. Additionally, minus the exhaust recovery on the US radials, there wasn't anything particularly groundbreaking done in aero piston engines post 1943.

Thirdly, the engines certainly did not struggle with the extra weight. 37mm's had been in use since the Spad XII, which had less than a quarter of the output of the engines in 1939.

The greater issue was with its effect on maneuverability and handling. Though this was largely mitigated in large engagements, which tended to be determined by numerical and positional advantage more than anything else.

 

[sloreck]

An issue with cannon vice machine guns is ammunition supply, and I'll leave out .30/.303 cal guns as they were relatively ineffective by WWII. In a dogfight, the adb=vantage of 6-8 .50 cal is a lot of lead goes downstream in a short burst and most of the time the attacker will get a good line up for short periods. With fewer rounds on the way with a cannon, the odds of a hit are down. Of course a single cannon shell does more damage than a single .50, this is a subject requiring a lot of math to figure out. Now for bombers, a large target, in the sight picture for longer, and harder to knock down, a cannon is the way to go.

For ground attack, a .50 cal will do a good job on troops, trucks, and even railroad locomotives. Against armored vehicles, a cannon, preferably larger than 20mm, is the way to go.

 

[Riain]

Personally I am a fan of cannon mounted in or attached to the engine: their relatively low RoF means that losses from the interuptor gear are not too bad and their rigid mounting makes them more accurate than wing guns which flex during hard turns.

But space in that part of the plane, right in in CoG, is at a premium and I think guns would have to displace fuel to some extent.

Wing roots is another good place to mount heavy cannons, for similar reasons why engines are good mountings.

 

[riggerrob]

My dear Riain,

The basic definition of a motor-cannon is a cannon that fires through the Center of the propeller hub, obviating the need for Interruptor gear because no propeller blade ever passes close in front of the muzzle.

The French firm Hispano-Suiza introduced the concept of motor cannons during WW1. The first HS36 V8 liquid-cooled engine only had a Lewis LMG (.303") firing through the prop hub. Later versions included up to 20mm cannons firing through the prop hub.

 

[Riain]

Thats a very specific thing, especially when there are other ways to gain the benefits it provides.

 

[marathag]

The French firm Hispano-Suiza introduced the concept of motor cannons during WW1, with their HS engine. The first HS. engine only had a Lewis LMG (.303") firing through the prop hub. Later versions included up to 20mm cannons firing through the prop hub.

SPAD XII had a 37mm, but that was so large, it protruded into the cockpit to the degree that the control stick couldn't be center mounted

 

[tomo pauk]

...

WI other engine manufacturers could have modified their engines to accept motor-cannons?
Could you install a MC in a RR Merlin?
Consider how many different Merlin variants were developed and most of the changes were to induction systems.
RR Griffon?
Allison V-1710?
Radial engines ..... consider the transfer case on the R975 radial engine installed in M18 Hellcats. The transfer case displaced the drive shaft down to the outer circumference of that radial engine. If you install a motor cannon in any other radial, the prop shaft - and cannon - will stay on the centre-line but will be displaced up or down until there is sufficient clearance between cylinders. Try to picture the small Pobjoy radials built during the 1930s.

This thread almost slipped through

For the V-1710, it would've mean that P-39 is concieved properly - engine in the front, turbo at the back. Probably the tricycle U/C goes as well, it's previous space taken by cooling radiators. More space for turbo might mean lower drag than what OTL XP-39, so the turbo remains for production models. No engine and radiators in the center fuselage can allow for extra fuel. Such an aircraft might've been a major boon to the Allied war effort.
Engine cannon on the V-1710 might also mean P-51 with 1-cannon + 2 HMGs - lighter, more firepower and less drag than original 4 HMG + 4 LMG installation.

For Merlin - RAF can have a cannon-armed Hurricanes and Spitfires in 1940 (plus 4 Brownings as back-up), for next to no performance penalty vs. the 8 Browning set-up. Engine cannons don't require extra heating as the wing installations do, one powerful Hispano can kill anything in 1940, there is no 'either 2 or no cannons' equation. Once Merlin has more HP, install 2 cannons in the wings instaed of 4 Brownings, for obvious total of 3 cannons, carry over once Griffon is available.

For Soviets, the MiG-1/3 can have a 20 mm cannon from day one (though I'd install another as a sysnchronised weapon). Or - go with AM-38 + 37mm to scare tanks and aircraft alike. Il-2 can have the 37mm cannon for tank busting + still carry some bombs or rockets.

2-row radials aren't very suitable for engine cannon, and, with engines of 1700-2000 and more HP, the benefits of the engine cannon are moot anyway.

 

[Cryhavoc101]

The motor cannon arrangement while advantageous to a single cannon mount - imparted not insignificant design compromises on the engine and properller gearbox arrangement

And may also impact the placement of fuel tanks etc particulalrly around the point of CoG

IMO the advantages of this type of cannon arrangement is outweighed by the advantages of having a better engine layout un compromised by the need to support said motor cannon.

 

[Archibald]

AFAIK the entire motor-cannon saga started with Hispano-Suiza HS.7 and HS.9, the 12X engine, and the Dewoitine D-501. France saw it as a miracle weapon but it didn't worked too well until the MS-406 in the late 30's.
https://en.wikipedia.org/wiki/Dewoitine_D.500
https://en.wikipedia.org/wiki/Hispano-Suiza_12X
https://en.wikipedia.org/wiki/Hispano-Suiza_HS.404

 

[tomo pauk]

The motor cannon arrangement while advantageous to a single cannon mount - imparted not insignificant design compromises on the engine and properller gearbox arrangement
And may also impact the placement of fuel tanks etc particulalrly around the point of CoG
IMO the advantages of this type of cannon arrangement is outweighed by the advantages of having a better engine layout un compromised by the need to support said motor cannon.

Engine layout of German V12 engines didn't suffered a single bit because they have had provision for engine cannon.

AFAIK the entire motor-cannon saga started with Hispano-Suiza HS.7 and HS.9, the 12X engine, and the Dewoitine D-501. France saw it as a miracle weapon but it didn't worked too well until the MS-406 in the late 30's.
https://en.wikipedia.org/wiki/Dewoitine_D.500
https://en.wikipedia.org/wiki/Hispano-Suiza_12X
https://en.wikipedia.org/wiki/Hispano-Suiza_HS.404

Spad was the 1st, back in the Great War.

 

[Archibald]

Yes and the experience benefited HS in the thirties. The cannon SPAD wasn't really practical, even for Georges Guynemer.

 

[Just Leo]

Engine layout of German V12 engines didn't suffered a single bit because they have had provision for engine cannon.

Rolls Royce made a specific decision to exclude the possibility of a motor cannon, and found substantial benefit in the freedom to optimize supercharger and induction systems for engine performance without thought or consideration to cannon placement. I think it worked out quite well for them.

 

[tomo pauk]

Rolls Royce made a specific decision to exclude the possibility of a motor cannon, and found substantial benefit in the freedom to optimize supercharger and induction systems for engine performance without thought or consideration to cannon placement. I think it worked out quite well for them.

Is there a definitive & readily available source for that?

 

[Just Leo]

Is there a definitive & readily available source for that?

If I hadn't had fifty years of various sources, it would be a lot easier to remember the one source. I also remember never reading that Allison made a conscious decision regarding motor-cannon.

 

[tomo pauk]

If I hadn't had fifty years of various sources, it would be a lot easier to remember the one source. I also remember never reading that Allison made a conscious decision regarding motor-cannon.

I'm at loss at what Merlin had to do with V-1710 here, while again stating that having provision for engine cannons did not seem to hamper German V12s.

 

[Just Leo]

while again stating that having provision for engine cannons did not seem to hamper German V12s.

Do you have a definitive source for that?