Fixed rearward-facing defensive guns - any worth in it?

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tomo pauk

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Apr 3, 2008
Germans were trying with the fixed MG on the HE 111, while the Fw 187 and Ar 234 were to receive the MG 151s for the same role. Was there anything worthy in this, apart of making pilot/crew feel good?
 
Not much worth as far as causing any enemy casualties.

IF you look at this subject you find at 3 different types of fixed rearward firing guns.
1. Fixed guns with little or no provision for actually aiming. Pilot triggers the rear guns when he thinks a pursuer is getting into a firing position. Lots of tracers may scare the perusing fighter/s off or at least disturb their aim. He 111, Some A-20s were supposed have provisions for two guns in each engine nacelle. Actual number of planes fitted (or flown in combat?)
2. Fixed guns with some provision for aiming, pilot has a periscope? (Ar 234)
3. Fixed rear guns angled down by 15 degrees (wide give or take here) for strafing while keeping the plane fly level. Aiming??? Martin Marylanders and Baltimore's and some French attack planes.

There may be some crossover between the 1st and 3rd categories?

Maybe somewhere some really unlucky fighter pilot was shot down by one of these guns
 
I'm aware that in late 1939 the French started studying fixed (sometimes vibrating) MGs, either 3 under the lower turret ("la cuve") or 2 in the Karman joints on the LeO 451, but this was not implemented before the Armistice, and after it the Italian armistice commission only authorized the Karman joint MGs, which were implemented on some but not all aircrafts.

The Amiot 35X series were also supposed to get 2 or 3 vibrating MGs in the lower fuselage to cover the dead zone not covered by the existing mobile MG.

This is mentionned in the Docavia on the B4 bombers, but no comment is made on their usefulness. I assume that it is obviously inferior to a mobile MG in terms of lethality, but maybe acceptable to stress enemy fighters and force them to abandon their attack, while not ruining aerodynamics as much as a turret.

A lot of the high altitude or high speed French bomber projects seem to forgo mobile armament and go solely for vibrating mounts, so just a step away from the Mosquito which only had an offensive cannon/MG armament.
 
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Even in the days of guns only armament, the only guns that were any use were those that could be truly accurately aimed, either by the flightpath of the aircraft or by gun aiming. Then, the realistic effectiveness of the weapon was a factor and, the simple problem of seeing the target to shoot at it.
Before the end of air to air WW2, rocket projectiles showed the way towards stand-off, and guided missiles with homing went even further.
Today, some people question the need for guns on air to air combat aircraft, but they usually have them because they are a flexible air to air weapon that can be crucial in certain scenario's.

Eng
 
tomo pauk said:
Germans were trying with the fixed MG on the HE 111, while the Fw 187 and Ar 234 were to receive the MG 151s for the same role. Was there anything worthy in this, apart of making pilot/crew feel good?
Click to expand...
If filled with blanks would it give a noticeable acceleration boost? IIRC, the heaviest fixed rear-firing gun ever fitted to an operational aircraft was the 20 mm MG 151/20 cannon on the Dornier Do 335. FWIW, I asked ChatGPT for the thrust of this gun on the Do 225, and it said 4–8% of one engine's effective thrust.
 
Doing a quick and dirty recoil calc on firing one mg 1151/20 round, I got a recoil velocity inpulse on a Do 335 of 0.027 mph. I think ChatGPT might be a bit off.
 
On some B-25's they put a .30 cal machine gun mounted on a jeep spring with lost of tracer ammo sticking out of the plexiglass tail cone. It could be switched on by the pilot and sole purpose was to scare anyone coming up behind them.

Some B-17's tried shooting bazooka rockets out of the tail.

The B-45 was used as a recon aircraft in Korea and for those missions fixed one .50 cal pointing up at an angle and one pointing down, and once again was supposed to scare interceptors. When they crossed the Sea Of Japan on the way home they would switch on the guns, since it saved a lot of trouble in the disarming process.

By the way, has anyone ever heard of those movable rear guns on the Me-210/410 hitting anything?
 
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