YFM-1 Airacuda

[ThomasP]

Hey Zipper730,

I do not know all of the history of the 37mm M4 gun, but this is what I have:

M4E1 used a 5-round clip (the 5 rounds were held in a stripper clip, and each 5-round clip was loaded individually into the loading tray, as shown in the photo I posted upthread) This was the gun fitted to the XFM-1 and YFM-1 prototypes.

M4E2 used a 15-round magazine (with the rounds in a disintegrating link belt, as below) I think the links and casings were ejected from the aircraft, but I am not sure.

M4E4 used a 30-round endless belt magazine (basically a 30-round flexible stripper clip, the belt moved along the inside of the bow shaped magazine - similar to a conveyer belt - with the rounds being stripped from the belt, fired, and the case ejected into a spent casing box below the gun)

The P-39C and some early P-30D used the 15-round magazine. As far as I know all P-39D-2 and later marks used the 30-round magazine.

 

[XBe02Drvr]

The F-16 has a fly by wire flight control system, so if you lose the engine or just the IGD you are going to lose everything. So it has an Emergency Power Unit powered by hydrazine to enable them to get it on the ground before the pilot ends up being like a guy in lawn chair at 20,000 ft with a only a Nintendo game for company.

What, no RAT?

 

[MIflyer]

I've spoken with long range ferry/delivery pilots who carry a rig like that with them on long flights.

Well, that sounds like a good idea. The early P-38 models had only one generator. If you lost that engine it was all over; the Curtiss Electric props did not like not having electricity. On the Martin B-26 they had two generators, one on each engine, but if you lost just one generator it was an abort situation because loss of the other generator or the other engine itself meant the Curtiss Electric props would quit working properly.

What, no RAT?

That's what I thought. Apparently not. The A-7D has one, but I guess the F-15 does not, because it has two engines and I assume both have IGDs. You'd think the F-16 does but maybe it was too tight of a fit.

 

[XBe02Drvr]

The early P-38 models had only one generator. If you lost that engine it was all over; the Curtiss Electric props did not like not having electricity. On the Martin B-26 they had two generators, one on each engine, but if you lost just one generator it was an abort situation because loss of the other generator or the other engine itself meant the Curtiss Electric props would quit working properly.

Ya know, looking back down the tunnel of time with my retrospectroscope, I sometimes wonder how Curtiss stayed in business so long, and how electric props stayed in the mainstream so late. Given all the electric's shortcomings, it's a wonder hydraulic, and especially hydromatic, props didn't drive them out of the market way earlier.
After the P40, Curtiss didn't come up with any plane you could call a winner, despite a few that did get into production (Helldiver, Commando, Seagull) due to their shortcomings being overlooked under the stress of wartime. I was born early enough to have spoken with some SB2C and C46 pilots before they died, and had an uncle who was a TBM pilot who got transitioned to SB2Cs. His TBM squadron was training to use their Avengers as CAS bombers, but no sooner did they get worked up for deployment than the word came from on high to convert to Helldivers and be redesignated a VB squadron. So he got checked out in the SB2C which he hated. "Grumman always built a pilot's airplane. Curtiss built a pandora's box of gotchas! Nasty stall, ridiculous speed and G limits, squirrelly as hell in a dive, and a bastard getting onto the boat! I could glide bomb more accurately with the TBM than I could steep diving with the HELLbox!" Come deployment time, he was yanked from his VB squadron and sent to a composite squadron to fly TBMs off a jeep carrier in the Atlantic. His new CO told him he had been chosen because he was a high time nugget and because of his TBM carrier qual landing scores on the Wolverine, a tiny Lake Michigan paddle wheeler converted to a training carrier. Avenger pilots who qualed on the big boats were having trouble on the CVEs. He became the highest time Ensign and instant flight lead in his new VC squadron.

 

[nuuumannn]

nly in a twin with feathering props does a failed engine consistently stop turning. Fixed pitch and most constant speed props on singles will windmill when they quit unless the pilot goes to great lengths to stop them by hovering on the edge of a stall and waiting for it to wind down. Only worthwhile if you've got plenty of altitude and need to maximize your glide distance to the nth degree. Otherwise, your increased sink rate during your ultra slow flight to get your prop stopped will likely negate your improved L/D from eliminating the windmill.

Yeah, I know this, and it's not gonna get you any useful electrical power. Best off concentrating at the job at hand and landing the aircraft.

 

[nuuumannn]

So it has an Emergency Power Unit powered by hydrazine to enable them to get it on the ground before the pilot ends up being like a guy in lawn chair at 20,000 ft with only a Nintendo game for company.

Concorde was the same, didn't have an APU but had a little emergency generator in the tail, a wee rocket-fuelled engine for emergency systems use only, although it did have a RAT, a rather large one, as expected.

MoF 18

and especially hydromatic, props didn't drive them out of the market way earlier.

Yup, and the basic concept is still in use today, ATRs, Dashes and their 14SF Sundstrand props work on exactly the same principle.

 

[MIflyer]

Well, unless you used a Curtiss Electric prop I don't think you could have a gun firing through the prop hub. There may be other technical reasons why electric props are better for some applications.

 

[nuuumannn]

Well, unless you used a Curtiss Electric prop I don't think you could have a gun firing through the prop hub.

Not really a requirement on a 50 to 70-seat regional airliner, but whatever floats your boat...

 

[nuuumannn]

There may be other technical reasons why electric props are better for some applications.

It's just another means of altering the blade angles, and was fine when it worked. It required a bit of electrickery to maintain though. The Hydromatic props are
mechanically much simpler.

 

[XBe02Drvr]

Yeah, I know this, and it's not gonna get you any useful electrical power. Best off concentrating at the job at hand and landing the aircraft.

Well, I did a fair bit of unauthorized experimentation with various single engine planes with an eye to enhancing my emergency skills and discovered that at best windmilling glide speed their alternators could handle any reasonable electrical load including flaps, gear, lights, trim, and avionics. The one main drawback was that the vaccum gyros would start to precess after awhile, as the pump wasn't maintaining rated vaccum.
Later on when I was teaching IMC emergencies, I would have the student put soap dish suction stickers over the AI and DG if I gave them an engine failure under the hood. If you've been using those two for primary attitude reference they're awfully hard to ignore when they start lying to you and you have to go needle-ball-airspeed.
When I flew single engine charter or corporate, I always had soap stickers in my bag.

 

[nuuumannn]

Later on when I was teaching IMC emergencies, I would have the student put soap dish suction stickers over the AI and DG if I gave them an engine failure under the hood.

Ah, those. I remember that from when I learned to fly and was doing instrument failures. I actually enjoyed instrument flying and got into the swing of it quickly. Was never rated, but as part of the PPL we had to do an hour or so's instrument training, which, I can remember part of which took place during a particularly cloudy day. Didn't require the foggles at all, a complete blank outside the aircraft. Very eerie and true-to-life instrument flying. Really enjoyed it.

 

[NVSMITH]

Per the manuals, the 37mm guns were clip fed. There were 22x 5-round clips per gun, so 110 rpg.

View attachment 632300

Like the Japanese Type 11 LMG but writ large??

 

[unkated]

Fully functional remote control turrets were still nearly a decade in the future. I suspect the only viable option might've been fixed forward firing cannons as in conventional fighters of the time.

IIRC, the guns were limited traverse forward; the pilot's gunnery controls were range setting to adjust the gins to converge on the target at range. In local control, they are still firing within a 15-degree cone forward.

Uncle Ted

 

[ThomasP]

Hey NVSMITH,

Not the same, but similar in concept. The 6.5mm Type 11 LMG used a base mounted stripper clip similar to the one below:

The 37mm M4 & M10 used a side mounted 5-round stripper clip like the one for the 37mm M1 AA gun (which held 10-rounds). The drawing below is for the 37mm M1 AA gun. IIRC the construction of the 5-round stripper clip for the 37mm M4 was basically the same. This would make sense since the guns were designed by the same men/company.

 

[Zipper730]

When were reliable flexible cannon caliber stripper clips made that could carry 15, 30, 60 and 110 rounds of ammo which didn't break under g-load?

 

[ThomasP]

Hey Zipper730,

I am not quite sure what you are asking.

The FM-1 prototypes used 5-round stripper clips (As far as I know there were no 10-round stripper clips used in any US aircraft system.)

The XP-38A used the 15-round disintegrating link belt.

The P-39C and some early production P-39D used the 15-round disintegrating link belt, but most(all?) P-39D-2, and all subsequent 37mm armed US P-39 models were delivered with the 30-round endless belt (ie flexible stripper clip) magazine. (There are photos of Soviet aircraft in the field equipped with the 15-round belt but I do not know how common this was. There are also description and maintenance sections in the Soviet manuals,)

The early P-63A models used a 30-round endless belt magazine, but from the P-63A-9 model on they used a 58-round disintegrating link belt.

I have read that the installation for the XP-59 was tried with a couple of different arrangements, but the only photo/description of the system I have seen used a 59-round endless belt magazine as below:

 

[Zipper730]

What was the biggest disintegrating cannon belt-link used in terms of rounds in 1939-1941

 

[ThomasP]

The Beaufighter Mk II switched from 60-round drum to 240-round(I think) belt feed after the first few airframes (mid-1941?), but they also used a servo assisted feed system. In effect the servo mechanism (basically an electric motor driven set of gears that grabbed the belt) was doing 90% of the work lifting the belt out of the ammo box and pushing/pulling the weight of the belt to the 20mm. From what I have seen/read the system was a pretty good one, but I have never seen anything official on it except in an AM memo saying that it was reliable.

If you are asking specifically about a 37mm belt feed, I do not think there was anything larger than the 15-round belt for the US 37mm in that time frame

The Soviets had the Sh-37 and NS-37. The Sh-37 entered limited service in late-1941 on the LaGG-3, and the NS-37 was in service on the LaGG-3 by late-1942. In the LaGG-3 the engine mounted Sh-37 and NS-37 both used a 20-round endless belt magazine. In the later Yak-9T the engine mounted NS-37 used a 30(32?)-round disintegrating link belt.

The RN had the 2pdr (40mm) AA gun on board ship, which in the 8-barrel mount used 115-round disintegrating link belts. I do not remember reading about any problems with the belt breaking, but it was not subjected to increased g forces like an aircraft gun system is.

 

[Zipper730]

The Beaufighter Mk II switched from 60-round drum to 240-round(I think) belt feed after the first few airframes (mid-1941?), but they also used a servo assisted feed system. In effect the servo mechanism (basically an electric motor driven set of gears that grabbed the belt) was doing 90% of the work lifting the belt out of the ammo box and pushing/pulling the weight of the belt to the 20mm. From what I have seen/read the system was a pretty good one, but I have never seen anything official on it except in an AM memo saying that it was reliable.

How many drums did the Beaufighter have?

 

[ThomasP]

16x 60-round drums (info from the Weight and CG Diagram page of the Beaufighter Mk I manual)