[twoblink]

I'm eating dinner and there's an old movie on TV. A WWII movie of sorts..

I'm assuming it's the Battle of Midway.. But here's my question..

They are flying prop powered planes... and the machine guns are behind it.. So how is the timing done so you don't get the bugs bunny shoot my own prop off effect?

And the follow up question would be, what kind of machine guns were they that are mounted on those planes?

[Orthonym]

read some (technical ) history! Ever hear of Roland Garros? Or Tony Fokker?

Alright, I'll try and enlighten you. In the first World War, once the aviators decided that it was ok to shoot at each other they immediately ran into problems. It's VERY difficult to hit something moving in 3 dimensions while doing the same oneself. Pistols were tried, rifles were tried; didn't work.
Garros had an inspiration, that flying an airplane and aiming a gun at the same time were too much, so he thought, "Why not aim the airplane and the gun together?" So he had a Hotchkiss mounted on his Morane-Saulnier with some hardended steel deflectors on the propeller in way of the bullets. He figured that most of the bullets would miss the prop and the deflectors would catch the rest.

Well, that worked for a while until he was shot down and captured. The Germans hired Fokker to duplicate the system. He, being a a good engineer , thought the Garros system was revoltingly crude and proposed something that would stop the gun when it had a prop blade in front of it.
Here is where historians differ. Some say Fokker invented an interrupter gear, some say he cribbed it from unused apparatus in Garros' plane.

[Mk VII]

There is no mystery about a machine gun firing through a propeller without hitting the blades. Nearly everyone understands the principle by which the valves of a gasoline motor are timed so as to open and close at a given point in the revolution of the engine. In the same way a machine gun may be timed to shoot. On the end of the cam shaft of the motor is placed an additional cam. Next to this is a rod connected with the breech block of the gun. When the gun is not being fired the rod is held away from the cam by a spring. pressing the trigger brings the two in contact , and each time the cam revolves it strikes the rod which in turn trips the hammer of the gun and causes it to fire. The cam is regulated so that it comes in contact with the rod just as each blade has passed the muzzle of the gun which can therefore fire at this time only. The engine revolves at least 1,000 turns per minute and as there are two chances for the gun to fire for each revolution, this would allow the gun to fire 2,000 shots per minute. The rate of fire of a machine gun varies from about 400 to 1,000 shots per minute according to the type of gun and the way in which it is rigged. The gun therefore has many more opportunities to fire between the blades of the propeller than its rate of fire will permit it to make use of. Consequently, the gun can work at full speed regardless of ordinary variations in the number of revolutions of the engine.
Of course this depends on the ammunition having a high degree of immunity to misfires and hangfires and some users made higher grade stuff for airplane use.

[Orthonym]

Well, as all sorts of famous people like Albert Ball, Werner Voss, and Eddie Rickenbacker demonstrated, this was the best way to arrange mgs in a fighter. (given flimsy aircraft construction at the time) Up through the 30s and 40s almost all high-powered aero engines came with accessory drives for one or more gun synchronizers. About 1938-40 or so air forces wanted to put more guns on the planes. This coincided with stronger (metal) structures. They could thus put LOTS of guns in the wings, outside the propeller arc, without worrying about synchrony.

Even so, lots of planes had guns firing thru the prop all through the 2nd World War. Examples: Mitsubishi Zero, Messerschmidt ME-109, Douglas SBD. Hope that helps.;)

[Mike Irwin]

Essentially it was done with a series of cams and linkages that kept the machine gun from firing while the prop was in the arc.

With most American fighter planes this wasn't much of a problem, as wing mounted guns were the norm, firing outside the arc of the propeller.

Some American dive bombers did have guns mounted in the fuselage that would fire through the propeller arc.

The Bell P-39 Air Cobra and the P-63 King Cobra both used above-engine guns, but they weren't front-line US fighters. Most went to the Soviet Union.

The Curtis P-40 Warhawk may have been the last front-line American fighter to use guns mounted in the cowling above the engine.

The Douglas SBD dive bomber, one of America's most lethal weapons during the war, sinking more Japanese shipping than any other weapon, had two .50s mounted in the engine cowling and firing through the propeller arc.

As for the guns themselves, early in the war some American fighters were still using .30 Brownings (.30-06, the standard service cartridge) but the United States recognized very early that a heavier weight of firepower was needed, and pretty much adopted the .50 BMG as the universal aircraft armament for the duration of the war.

Most American fighters carried 6 of these guns, while the P-47 Thunderbolt carried 8. The Lockheed Lightning carried 4, but boosted that by mounting a 20mm cannon.

The 20mm was used in some aircraft, such as the some versions of the Curtis SB2C Helldiver, and some very late war Marks of the Vought F4-U Corsair and the F6-F Hellcat were armed exclusively with 20mms, but these versions saw very little wartime use.

The F7-F Tigercat, introduced just as the war ended, would have been a real slugger, with 4 .50s and 4 20mm guns.

I THINK there was some thought later in the war to arm P-47s with either 4 or 6 20mm cannons as a way of dealing with heavier German armor, but that was never done, and the T-bolt pilots generally attacked armor with machine guns and the 5" rockets.

The British made much heavier use of the 20mm gun, though, and the Hawker Typhoon, mounting 4 20mms as well as rockets, became the real Allied tank killer of the war.

[Orthonym]

Don't forget the cannon firing through the propeller hub in the P-39 & Me-109! (gears, y'know)

Edit: Mike, that's not Air Cobra, it's Airacobra!

[Mike Irwin]

Didn't forget them.

Wasn't pertinent to the question...

As for the American 37mm in the P-39 and P-63, I have an empty casing for one of those sitting on my desk as I type this...


"Aircobra, not Air Cobra..."

I know... Same with Kingcobra.

Stupid moe-rons at Bell. Crappy aircraft, crappy naming conventions.

[Orthonym]

Yeah, but it was like, comfy. Doors on both sides, roll-up windows... no that was the P-38?

[Orthonym]

We just might convert this into an aerophile board yet, Oleg Willing.:p

[Mike Irwin]

P-38 couldn't be classified as comfy by any stretch of the imagination. The cockpit was roomy enough, by the pilots complained bitterly (literally) about the inadequate heating in the cockpit.

While seemingly a small creature comfort, it could actually be a problem if you didn't have enough heat getting into the cockpit to keep the canopy frost and mist free.

As for the doors, that must have been the P-39, as in the P-38 the pilot was actually sitting in the middle of the spar, with mid chest apparently about level with the top edge of the spar.

My scoutmaster when I was a kid was a P-38 pilot and first told me about the heat problem. He said that otherwise it was a great aircraft.

[Orthonym]

Yeah, I've heard about that . Not so bad in the Pacific, maybe, but hellacious in Northern Europe in winter. P-39s really did have car doors on each side, though. And an amazing, annoying mix of guns. One 37mm, 2 .30cal, 4 (?) .50 cal. What fun for the supply guys.

[Orthonym]

My last post reminds me that this ought to be about guns, and also about common cartridges for us common people. Special guns/cartridges for airplanes or soldiers? Nahh! I don't own a rifle, but before I get one I will inquire about the numbers of different sorts of cartridges sold.Then I'll think very seriously about buying one which uses the most common, universally available ammo. But that's probably already been discussed to death on some other thread here.

[dinosaur]

If you watch The Discovery Wings channel, they have an episode on how these were developed plus other not so well known military aircraft subjects.

[telewinz]

The P-39 was popular with just one country, Russia. Early in the War they had great faith in the HAND LOADED 37mm cannon, they loved it and used it early against German tanks and vehicles, but this is for another forum.

[Nando Aqui]

As stated above, originally a French development. But before that, metal deflectors had been attached to the propellers to keep bullet from damaging them!

In the fall 1914, MS23's Roland Garros, famed prewar flier and Morane-Saulnier test pilot, renewed Raymond Saulnier's unsuccesful prewar attempts to develop and patent a synchronized gear for a machine gun to fire through the propeller arc. By that November, Garros and his mechanic, Jules Hue, experimenting with a Hotchkiss gun fixed to fire through the arc of a specially armored propeller, had found that only 10% of the bullets hit the airscrew. Although that 10% caused breakages on the ground that would have wrecked the plane in flight, Garros remained confident of his scheme's feasibility and was released from MS23 during the winter to work with Saulnier to improve the steel deflectors on the propeller blades. In the spring, he entered MS26 at Dunkirk, equipped with a Morane with channeled deflectors. Within three weeks, from 1 to 18 April, he shot down three german airplanes, an astounding feat for the time.

When Garros himself fell victim to antiaircraft fire, the Germans captured him and his plane and quickly produced a Fokker monoplane armed with a synchronized machine gun, which appeared at the front in July. Though few in numbers (only 40 at the front by December), the Fokkers gave the Germans aerial ascendancy. (from "The Great War in the air")

Fokker's "Eindecker" (single-wing or monoplane, below) was the first German airplane that could fire a forward-facing machinegun through the propeller without having the bullets hit it.

http://www.aviation-central.com/1914-1918/images/acg6d-ef.jpg

[Apple a Day]

P-39 had the side door.
There was one British Squadron equipped with the P-39, No. 601, which hated it so much they sold them to the Soviets and Australians. Half of the 9,585 built went to the Russians. Russians and Czechs used them from rough airfields as ground attack aircraft. The American versions went to training and saw some action with Americans in the Pacific. I also have a pic of one in the Portugese Air Force. There were some Free French and co-belligerent Italian units that used them.
The P-39D had a 37mm cannon, two .50s, and four .30s.
Gen. Chuck Yeager trained on the P-39 and said that he'd have gladly taken it into combat. IIRC he described shooting the 37mm 'like chucking flaming grapefruit out the front of the aircraft'. It only carried max 30 rounds of 37mm. He and the other trainees used to 'hunt' with the P-39, reportedly. A couple of guys would go out in a jeep and one in the Aircobra. He'd charge only one machine gun, spot a mule deer or whatever from the air and shoot it, then the guys in the jeep would pick up the carcass for chow. That's one of those things on the growing list of "Stuff You Would Never Be Able To Get Away With Nowadays".
Maybe that last part should go under the hunting forum? Favorite techniques for stalking game with a WWII fighter!:what:

Is anyone else uneasy at the idea of having deflectors right in front of you and blasting away at it with a machine gun? Did anyone get hit with a ricochet? Would that be considered 'French roulette'?

[Kharn]

Twoblink, imagine a cam attached to the shaft of the propeller, with a bump in the cam leading the prop blade (timed so a bullet wouldnt hit the prop), and then an inverted 1911 disconnector-ish looking thing running from the cam to the machine gun. Whenever the cam pushed the disconnector up the gun couldnt fire; but as soon as the disconnector returned to the low point of the cam the gun would resume firing.

During WWII, I believe the most common US-mounted aircraft gun was the M2 .50.

Kharn

[seeker_two]

If you keep an eye on the "Mail Call" and "Conquest" reruns, they've done shows on this question too...

[Gewehr98]

See all those bombers with upper turrets that swivel 360 degrees? They had an interruptor the prevented the gunner from shooting off his own vertical stabilizer and rudder when he was firing aft at a target while traversing. Darn good idea, that. :what:

[NRA Instructor]

I think next we should explain to the younger members about origin of "the whole nine yards".

[twoblink]

In my mind, I always imagined it as like a Gatling Gun, only, it's cammed directly to the prop. So the prop keeps rotating the gun in sync, and when you depress the trigger, it fires, but always in sync.

Good, glad I wasn't so far off..

[Sean Smith]

Whole 9 yards = the total length of the linked ammo belts that fed the .50 Browning machine guns in a P-51 Mustang, allegedly. This saying has also been attributed to the Brit's Supermarine Spitfire, though the Spitfire and Mustang had different armaments... the Mustang had 6 .50 Brownings, while the Spitfire had 8 .303 machine guns (and later a mix of 20mm and .50 or .303 machine guns).

Note that the source of that saying is VERY disputed. Some think the whole WWII origin of the saying is bunk.

[Art Eatman]

P-39. Bell Aircobra. Liquid-cooled engine.

The photo is of one upon landing in early 1942 at what finally became Managua Intl Airport, Nicaragua.

:), Art

[Quartus]

That's an EARLY P-39, Art!


Story time:

Norco Airport, CA, circa '71 or '72. Two high school kids get dropped of by one's dad, and are left to wander the airport. What sights to see! Two B-25's that were used in filming Catch-22, just sitting behind a locked fence. A B-17F sitting out on the tarmac. Got to walk right up and around and under! What's in that hanger? Oh, just the Cox P-51 "Miss America" and an assortment of other vintage pylon racers. Spit polish clean - shiny concrete floors. A (good) mechanics dream shop. IIRC, "Miss" was the reigning champ at the time. Somebody spotted two heads peeking in the door and invited us in. Warm welcome - look but don't touch. Ask questions. Glad to have you. :what:

Two boys in hog heaven! :D :D


Another hangar. Dirty, junky, with the fuselage of a P-39 gathering dust. LOT'S of dust. Again, somebody sopts two heads poking in. Get outta here! :cuss: Can't you see there are valuable aircraft in here? :cuss:

:rolleyes:

Great day! Later it bacame an air museum, when "Cars of Stars and Planes of Fame" folded. What was left moved out to Norco. Still there last I heard.


That's near Riverside, California.

[Stevie-Ray]

Some of the WWI guns were mounted on the top wing, thus eliminating the need for synchro. The Nieuport 17 and the S.E.5a were two sporting this configuration for at least part of their history. They were also two of the best fighters to come out of that war. Canadian ace Billy Bishop, in fact, shot a great number of his 72 planes down while piloting a Nieuport.

[Autolite]

Talking about aircraft guns-and-propellers-and-such, check out a book entitled "Flying Guns of World War II, Development of Aircraft Guns, Ammunition and Installations 1933-1945". The authors are Anthony G. Williams and Dr Emmanuel Gustin. The book is quite detailed and well researched. Mr Williams has another excellent book called "Rapid Fire" that deals with the history and development of automatic cannons used by Armies, Navies, and Air Forces ...

[Mike Irwin]

"the Mustang had 8 .50 Brownings, while the Spitfire had 8 .303 machine guns..."

Incorrect...

All American production Mustangs had 6 .50 BMG guns.

Early ones that went to Britain, with Allison engines, had a more mixed bag. Some had 4 .303 machine guns in the wings and 2 .50s mounted the under nose and some were regunned with 4 20mm cannon.

The A-36 version, adopted in limited numbers for ground attack duties with the US, was the first to carry 6 .50s as a regular tune out, which continued when it was redesignated as the P-51.

The only US fighter to mount more than 6 .50s was the Thunderbolt, which did have 8.


"The Nieuport..."

Had a nasty tendency to shed the fabric from the wings in a steep dive... Never a pleasant thought!

Eddie Rickenbacher, who flew a Nieuport for sometime before graduating to a Spad, said that one of the great graces of the Nieuport was that if the engine quit, it was a very capable glider.

The Spad, on the other hand, was a lead kite.

[Mike Irwin]

"The authors are Anthony G. Williams..."

Ah, Tony Williams. I've come across him on some websites that we've both posted to. Very knowledgable guy. He's got a great website, but I've lost the link for it, unfortunately.

I'd LOVE to have his cartridge collection!

[Detritus]

The Bell P-39 AiraCobra and the P-63 KingCobra both used above-engine guns

mild correction, while the P-39/63 (the 63 being an attempt to take advantage of, build upon and inprove, the utility of the P-39 design as a ground attack plane) had a through the hub 37mm gun, it was NOT (as in the Bf-109) mounted above the engine. this is due to the Aira- and King- cobras having their engine mounted BEHIND the cockpit, and having a 9 foot long "tansmission shaft" running forward along the cockpit floor, between the pilot's legs (and yes a few guys WERE killed by shaft couplings failing at high RPM).
the only things up front other than the end of the drivetrain, were the guns themselves, (in first models) two .30cal brownings and the 37mm cannon (which was full auto but with a low cyclic rate) fed by a 30 round "continous belt" ie a big loop, loaded rounds go in one side, empty brass rides the belt out on the other.

i never can remember if that gun was built by Oldsmobile or Cadilac during the war.....

Stupid moe-rons at Bell. Crappy aircraft, crappy naming conventions. Now now careful there, we owe the X-1 (as well as several other signifigant test planes) and the UH-1 "Huey", to the kind if sometimes ahead of their time folks at Bell...

and just think of what might have happened if a Rolls Royce Merlin had been added to the P-39 like was done the P-51.

another note, the the early versions of the "mustang" ie Mustang Mk1/1A, some P-51As and the A-36 (a mustang with dive brakes) were the last US fighter designs to have through the prop MG installations, having as per the revised british specs two .50cal brownings mounted in the "chin" position ie below the engine.

[Autolite]

I know Pontiac Division built aircraft guns but I wasn't aware of other divisions doing the same. Does anyone else know of a Cadilac or Oldsmobile gun ???

[Roboshred]

Now now careful there, we owe the X-1 (as well as several other signifigant test planes) and the UH-1 "Huey", to the kind if sometimes ahead of their time folks at Bell...


Does this include the Osprey? I hope so because my Textron stock needs to recover. RB

:banghead:

[Mike Irwin]

"this is due to the Aira- and King- cobras having their engine mounted BEHIND the cockpit, and having a 9 foot long "tansmission shaft" running forward along the cockpit floor, between the pilot's legs..."

GAAAAAAAAAH!

You're absolutely right!

I apparently didn't have my brain shaft coupling engaged when I posted that last night!


As for Bell's aircraft, their great contributions came after WW II. Their contributions before and during the war?

Gak.

Even when the P-39 was adopted it wasn't keeping pace of the latest developments, even in the United States.

Bell's problem at the time was that it tried to be forward looking, but with the command structure that it had in place simply didn't know how.

[Mike Irwin]

The Oldsmobile division built the 37mm cannons used in the Bell aircraft.

The same cannon was also used in initial flight prototypes of the P-38 Lightning.

[Detritus]

Does this include the Osprey

not to me it don't, that fulls under the "bell, boeing, textron" (ie crap- built - by committe) aegis.

i only meant to defend the Bell Aerospace of the 20's to early 70's after that the company got taken over by "corporate types" who didn't really understand what was needed. (kinda sux when a good design firm gets taken over by bean counters)

[Orthonym]

= contents of ready-mix concrete truck.

[twoblink]

I'm curious how many shots it takes to shoot a plane down. You see some spray spray spray (Did I mention I love tracers??) and it looks like it hits a few dozen times, you get smoke, and then spray spray spray, a few more times...

It seems to me aerial combat is fairly difficult. Two objects moving in XYZ planes with one trying to establish a straight line on the other..

Without JMB, we would have lost the war!!

[Mike Irwin]

"How many shots it takes to bring a plane down."

Literally anywhere from 1 to a 1,000...

If you get lucky and kill the pilot or hit a critical system, you can bring the plane down with a single shot.

The British found out during the early phases of the Battle of Britain that the German aircraft were tough to bring down with the .303 machine guns that armed the Hurricanes and Spitfires at that time.

Every once in awhile you'll see a picture of a German bomber or fighter just RIDDLED with bullet holes.

Great for moral, but there's a hidden message there -- that it was taking a LOT of hits to bring down those aircraft.

That's one of the reasons why the British went with cannons more and more. A single hit from a cannon could destroy and engine, or strip a wing or tail off a plane.

[Kharn]

P51s, being water cooled, could be brought down with a single hit to the cooling system.
Thunderbolts, on the other hand, were air cooled and would just keep on flying with peices flying off the engine.
Or at least thats what the History Channel told me. :D

Kharn

[Mike Irwin]

Yeah, there's no doubt that aircraft with radial engines tended to be harder to bring down.

That's one of the reasons why every American carrier plane of WW II was powered by a radial engine.

The radials also tended to be somewhat easier to work on, as the cylinders were individual units instead of being covered by a monobloc cylinder head.

[Quartus]

That's why there are plenty of radial engined planes still flying all over the world. And modern piston aircraft engines are almost as good for the same reason. Fry a piston and you just take of that jug (cylinder) and replace it. Much easier than a car-type engine. (Well, other than VW & Porsche engines.)



and just think of what might have happened if a Rolls Royce Merlin had been added to the P-39 like was done the P-51.


Ditto for the P-38. That Allison engine just didn't do well with the cold weather in Europe. (Those cockpit heating problems didn't help.) That's why the P-38 ruled in the Pacific Theatre and did very well in North Africa, but not well in Europe.

[Sean Smith]

All American production Mustangs had 6 .50 BMG guns.

Good eye for the typo. But at least YOU goofed something too! :D

[Mike Irwin]

One of the major problems for the P-38 and the cold weather in Europe was that it tended to kill the superchargers.

It was not unusual for a P-38 to come back with one, or both, superchargers out in winter, or when doing a high altitute mission. One explanation that I've heard is that when the units got really cold the oil pathways would restrict too much, and the supercooler's bearings would starve for oil and simply fry.

When the Superchargers were working, it was a decent sub-15,000 foot escort, reconaissance, and ground attack platform.

That's also why Richard Bong could make 40 kills with it in the Pacific, while in Europe it was only a stopgap aircraft until the P-47 and the P-51 came on line.

[Quartus]

Yeah, but I still want one. Can I have one, Daddy? Can I? I pwomiss I won't fly it in cold weather!

I pwomiss! I pwomiss! :D

[Quantrill]

To the best of my knowledge, there is only one restored and flying P-63. It is owned and flown by the astronaut, Frank Borman. I had an opportunity to talk with him about it at a WWII Fly-in at Reading, Pa. a few years ago. He said that in order to get the "weight & Balance" correct for the restoration, it was necessary to fill a pipe with lead to substitute for the 37mm cannon. Quantrill

[Stevie-Ray]

Now now careful there, we owe the X-1 (as well as several other signifigant test planes) and the UH-1 "Huey", to the kind if sometimes ahead of their time folks at Bell... Yeah, don't forget the P-59 Airacomet. Or wait, maybe we should forget it.:D At any rate, being the plane that brought the U.S. into the jet age brought little fanfare for Bell. Truly disappointing performance as the P-59 wasn't even as fast as our finest piston engine planes. 50 were built in 1944, but were used ultimately for engine development. Orders for 300 more were canceled at the advent of the Lockheed P-80 Shooting Star.

[Mike Irwin]

I was going to say, Stevie!

At the start of the war the British sent a Whittle engine and a team from Powerjets limited to the United States to work on the concept. It was thought that with the American industrial capacity that we could have a jet fighter operational by 1944.

Hehehehehehehe.

Sorry, Charlie.

General Electric "Americanized" the Whittle engine, which resulted largely in a technological dead end for engine. Early GE plants were about as effective as the 1940-1941 engines had been in prototype Glocester Meteors.

Problem was, while the British kept moving the design of their engines forward, GE was chasing its tail, and really didn't start moving in a new direction with the engines until 1944. That's when they got it right, but that was too late for war service, and it wasn't until nearly 1948 that American engines had the performance of 1945 British engines, and a lot of that leap came from meticulous examination of German jet engines.

After that, thought, GE's design teams started moving almost unerringly in the right direction, and by the middle 1950s was producing the most advanced fighter jet engines in the world.

[twoblink]

I'm going to add a WWII fighter plane to my "every growing boy needs" list :D

The best way to learn about the mechanics of how the gun works is to own one right??:p

[Detritus]

there is only one restored and flying P-63

only one i know of flying, it's a restored Air-racer (if you strip all the armor out and keep it below 10,000 feet, and disable the "boost limiter" on the supercharger, P-63s made good post war Bendix racers). so it's painted in a scheme that is mainly bare metal with an anti-glare panel and a few other markings.

last time i saw it it was being housed in a hanger at Elligton field right next to the home of the CAF (comemerative[formerly confederate] Air Force) "tora tora tora" group (the guys who fly the trainers converted to look like Zeroes, vals, and Kate torpedo planes) and the "texas raiders" B-17. the P-63 in question is also on loan to the CAF

there is at least one more on it's way back to flying status, and it is fuly owned by the CAF orginization and is in fact of the two the one with the longer association with the CAF.