Wait I'll get my dueling pistols, The only reason we got to see the picture of the hispano with the cannon in between the cylinder banks. Was because of the actions of trying to prove me wrong

I said PROVE IT, he did . .

Someone read it somewhere, but didn't know if it was true . . now we all know it was true

I notice from looking at the pictures, there was 2 sparkplugs per cylinder. Does anyone know if that was how engine speed was controlled, two seperate ignition systems

I notice from looking at the pictures, there was 2 sparkplugs per cylinder. Does anyone know if that was how engine speed was controlled, two seperate ignition systems

No, engine controlled via throttle and mixture controls, using a conventional carburettor ~ the dual spark plugs are most likely due to dual magnetos for durability, reliability and damage resistance... remember these engines had lives of only 50-100 hours before rebuilding, some substantially fewer, some a bit longer...

Within rotaries, the Monosoupape engines sometimes had variable coupé where different proportions of cylinders would not spark their fuel/oil load on every power stroke, the whole taking multiple complete revolutions of the four stroke cycle to fire each cylinder. Other rotaries had coupé switches that cut sparking completely. Most had some limited control of engine speed via fuel and air throttles. Rotary idle speeds were usually higher than those sustainable by in-line or v-engines, although I gather that idle was rougher for many in-lines at moderate 'high-idles'.

I should think that if the engine was used in high altitude work it would need rebuild quicker as a lean mixture means higher heat which translates to a faster oil breakdown, Had they progressed to a dry sump yet ?

The problem with above cannon: it is not a machine cannon.
So you had to load it after each shot.
That requires hitting with the first shot - otherwise the enemy either ran away,
or he would turn tight and get behind your bus.

In WW2 the Germans used 30 mm machine cannons in fighters,
but still their rate of fire was rather slow, and then the projectiles didn't
go straight at all, but rather into a noticably descending curve.

The Me262 jet fighter combined 4 (!) 'Rheinmetall MK-108' 30 mm machine cannons.
Now, that was a devastating firepower indeed - a few hits could cut off whole wings
from Allied bomber, or destroy their engines.

The Allies rather put on the concentrated firepower of six machine guns.
This way they could unite six fast-sequenced streams of rounds in one point somewhere
in front of your aircraft. If the E/A was at that convergence spot when hit, it must
have been quite effective. The big plus: even far behind this point of convergence,
where the rounds were more straying again, some rounds might hit the E/A.
A single cannon projectile would either hit - or miss.

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Thats a nice set of pictures. Sorry did mean to start a debate. but the truth is out, I guess thats a bonus. Sorry for delay in reply also i had no internet today, I read this just now but this wasn't my source for my orignal post can't remember where i read about Guynemer intially http://militaryhistory.about.com/od/airforce/p/guynemer.htm

Olham i guess if you missed with the first shot you just nosed down and hoped you could pull up before you hit the ground

That's basically the way I look at it. After the dust settled, and the smoke cleared, we were treated to some damn fine pictures, which we would've never seen otherwise

That Cannon used ammo that was designed to achieve maximum velocity when fired out of weapon with a much longer barrel. If they used the same technique as was utilized with the Vickers. the amount of bullet drop didn't matter, but if a somewhat longer shot was attempted, a miss is totally understandable

I think I read somewhere that the SPAD XII didn't have "normal" controls. I think it had something to do with the fact that the breach of the hub mounted cannon would get in the way of a normal joystick or something of that ilk.

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Quite correct castiglione, (how's that for alliteration). The SPAD XII used a Deperdussin-style control yoke which looked like an inverted 'U' with a hand wheel fitted to the top. This allowed room for the cannon which came so far back into the cockpit that the breech ended up between the pilot's legs. Imagine sitting there straddling a 37mm Hotchkiss which, when you fired the first round and missed, had to be reloaded as you guided your plane using your feet and knees whilest reaching down under your seat to remove the empty casing and insert the fresh round, during which time the cockpit filled up with all the spent gasses being pushed out through the back of the breech. Oh, and let's not forget the gunner/obs blasting away at you from the office of the two-seater you just took the errant potshot at. Good times ... good times.

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