Advanced French Fighters vs 1942/1943 contemporaries (2 Viewers)

[MiTasol]

Thank you both for those diagrams.

Am I correct that the PS system has three rows of inlet guide vanes with only the first being variable (and the other two locked and rotating with the centrifugal wheel while the Russian only had one set of inlet guide vanes.

EDIT - I have just read the USAAF report and realise I have misinterpreted the PS system - the PS system on the 12Z is downstream of the comprssor, not upstream as I was envisaging.

For the 12Z, I have these curves too.

And a personal pic of the (big) 12Z Turbomeca supercharger, with well-known twin inlet, but single outlet :

Nice photo. That distributor on the RH cylinder head - is it fuel injection or pneumatic starting?

Is there an on line manual for that engine?

 

[Bretoal2]

Thank you both for those diagrams.

Am I correct that the PS system has three rows of inlet guide vanes with only the first being variable (and the other two locked and rotating with the centrifugal wheel while the Russian only had one set of inlet guide vanes.

EDIT - I have just read the USAAF report and realise I have misinterpreted the PS system - the PS system on the 12Z is downstream of the comprssor, not upstream as I was envisaging.



Nice photo. That distributor on the RH cylinder head - is it fuel injection or pneumatic starting?

Is there an on line manual for that engine?

There is only one row of radial inlet mobile vanes - but before the impeller you have three separate wheels that rotate locked on the S/C axis. In other words, at the same rpm than impeller.

I don't understand your assertion about down or upstream of the S/C on the 12Z. The Planiol-Szydlowski superchargers for HS 12Y or 12Z are identically designed and situated in th engines, the differences are only on dimension (12Z is bigger to get bigger flow !) and 12Z has only one inlet (central induction system ont the 12Z such as Merlin, Allison, etc.). 12Y had 6 carburetors on the sides of the engine, so 2 inlets for its PS S/C.

Distributor on the right side is starter system (carbureted air).

No documents on line for the 12 Z !

 

[bf109xxl]

No one disputes that these two superchargers are constructed differently.

However, their operating principle is identical

No one claims that the principles were different.
I can't rule out that Stechkin and Polikovsky could have familiarized themselves with the French patent, but knowing the inertness of the Soviet system, I estimate such a probability as relatively low. Both Stechkin and Polikovsky had sufficient experience in supercharger aerodynamics to reach on their own approximately the same solutions as Szydlowski and Planiol.
But, I repeat, I cannot completely exclude the borrowing of principles - the development of Hispano-Suiza 12Y could be more closely monitored by Soviet technical intelligence or simply by structures engaged in analyzing scientific/technical publications.

 

[Elan Vital]

Something relevant to this thread: if all goes right I intend to go to the French archives again in the first week of October.

Among the documents I will be looking for are 1937-40 docs on the 33 mm APX and 30 mm MAT aircraft autocannons. This will be a nice opportunity to know more about these obscure guns and whether the French already airframes or engines (if motor-cannon) in mind for them.
If the documents on 30 mm and under AP ammo discuss ammo for aircraft autocannons, I will discuss those here as well.

 

[Bretoal2]

Something relevant to this thread: if all goes right I intend to go to the French archives again in the first week of October.

Among the documents I will be looking for are 1937-40 docs on the 33 mm APX and 30 mm MAT aircraft autocannons. This will be a nice opportunity to know more about these obscure guns and whether the French already airframes or engines (if motor-cannon) in mind for them.
If the documents on 30 mm and under AP ammo discuss ammo for aircraft autocannons, I will discuss those here as well.

The "moteur-canon" arrangement would have been ideal owing to the recoil expected from a weapon with a caliber significantly larger than the 20 mm HS 404.

With these, an aircraft such as the Bloch 152 initially had structural problems, and the wings had to be reinforced with Bloch's famous diagonal ribs. But of course, two canons out of the propeller circle provided exceptional firepower compared to synchronized, and therefore necessarily slowed, cowl-mounted weapons.

Returning to the "moteur-canon", the Hispano 12Y's hollow propeller shaft had an internal diameter of 61 mm. Was such a dimension sufficient for a 30 mm caliber weapon?

 

[Shortround6]

With these, an aircraft such as the Bloch 152 initially had structural problems, and the wings had to be reinforced with Bloch's famous diagonal ribs. But of course, two canons out of the propeller circle provided exceptional firepower compared to synchronized, and therefore necessarily slowed, cowl-mounted weapons.

????
Motor cannon were not synchronized. They shot through the hub so it didn't matter where the blades were.
On the other hand, the HS 404 was never synchronized. Perhaps the time between sear release and shell exiting barrel was too variable?
It any case it was never "cowl mounted".

The US .50 cal in cowl mountings suffered a huge loss in rate of fire.

 

[bf109xxl]

Returning to the "moteur-canon", the Hispano 12Y's hollow propeller shaft had an internal diameter of 61 mm. Was such a dimension sufficient for a 30 mm caliber weapon?

It is sufficient even for 45 mm caliber.

 

[Elan Vital]

The "moteur-canon" arrangement would have been ideal owing to the recoil expected from a weapon with a caliber significantly larger than the 20 mm HS 404.

With these, an aircraft such as the Bloch 152 initially had structural problems, and the wings had to be reinforced with Bloch's famous diagonal ribs. But of course, two canons out of the propeller circle provided exceptional firepower compared to synchronized, and therefore necessarily slowed, cowl-mounted weapons.

Returning to the "moteur-canon", the Hispano 12Y's hollow propeller shaft had an internal diameter of 61 mm. Was such a dimension sufficient for a 30 mm caliber weapon?

We will see if the docs say how it was supposed to be mounted or how large the barrel is.

I would be surprised if it was a wing mount given how large and heavy such a gun would be in WW2 aircrafts let alone French ones, so a motor cannon or nose mount for twin-engine fighters would make sense.

 

[Bretoal2]

????
Motor cannon were not synchronized. They shot through the hub so it didn't matter where the blades were.
On the other hand, the HS 404 was never synchronized. Perhaps the time between sear release and shell exiting barrel was too variable?
It any case it was never "cowl mounted".

The US .50 cal in cowl mountings suffered a huge loss in rate of fire.

I probably expressed myself too imprecisely.

Of course, guns mounted in the "moteur-canon" arragnement had not to worry about the position of the propeller blades. Cowl-mounted ones were the ones found above the engine in some fighters, such as the Zero, Yak 3 or other single-engine aircraft where two or more synchronized machine guns were mounted in the cowling, firing over the top of the engine.

And indeed, depending on prop rpm, the loss in rate of fire could be considerable for these synchronized weapons. That's what I meant in my message, recalling that the Bloch 152 was, along with the older Dewoitine 371, among the first mass-build fighters to have cannons in the wings outside the propeller circle. And the recoil of these large-caliber weapons was a novelty at the time !

These two planes (MB 152 and D371) had radial engines, unable to be converted to the "moteur-canon" concept.

 

[Bretoal2]

It is sufficient even for 45 mm caliber.

Really? And what about the thickness of the gun barrel?

 

[bf109xxl]

Really? And what about the thickness of the gun barrel?

The NS-45 had a barrel wall thickness of 4 mm (!!!) at the muzzle.
The NS-37 had barrel diameter at the muzzle is about 58-59 mm - estimated from the available sketch.
The NR-30: ~52 mm at the muzzle (last 150 mm), ~47 mm before the wall thickening.

 

[Elan Vital]

For preliminary info, this is what the small status reports on weapon studies noted about these guns:

- 33mm APX "machinegun", developped after the 120 rpm cannon tested in a Farman aircraft, firing through the propeller hub: 900 m/s, 250 rpm, in 1936 260 rpm was tested without trouble, updated in 1937 to 800 m/s and 300rpm, and finally 900m/s, 400rpm, 100kg weight without loader and ammo, still in development as of 1940.

- MAT (Tulle arsenal) 30x167mm aircraft gun: started development in 1936, 1000 m/s and 320 MPa pressure

So the 33mm was indeed probably a motor-cannon, though I suspect that its integration to an Hispano-Suiza 12-cyl engine would look rather different to 20mm mountings. Then again, some Yaks with similar engines got to use 30 or 37mm ACs?

 

[Airborne2001]

Here is a table from the old War Thunder forum that has a summary of further D.520 variants and their planned entry dates (not mine):

I would personally imagine that designs like the D.553/D.554 would take longer than 1941 to enter service due to the early issues with the HS-12Z.

 

[tomo pauk]

So the 33mm was indeed probably a motor-cannon, though I suspect that its integration to an Hispano-Suiza 12-cyl engine would look rather different to 20mm mountings. Then again, some Yaks with similar engines got to use 30 or 37mm ACs?

37mm, and even the 45mm cannons.

 

[TM06]

- 33mm APX "machinegun", developped after the 120 rpm cannon tested in a Farman aircraft, firing through the propeller hub: 900 m/s, 250 rpm, in 1936 260 rpm was tested without trouble, updated in 1937 to 800 m/s and 300rpm, and finally 900m/s, 400rpm, 100kg weight without loader and ammo, still in development as of 1940.

- MAT (Tulle arsenal) 30x167mm aircraft gun: started development in 1936, 1000 m/s and 320 MPa pressure

So the 33mm was indeed probably a motor-cannon, though I suspect that its integration to an Hispano-Suiza 12-cyl engine would look rather different to 20mm mountings. Then again, some Yaks with similar engines got to use 30 or 37mm ACs?

Yaks were fitted with 20 mm, 23 mm, 30 mm, 37 mm and 45 mm motor cannons. Khazanov and Gordon in Red Star Volume 5 note a single Yak-9 that was converted to use a 57 mm motor cannon as well. Considering this, it's a pretty reasonable conclusion that the MAT and APX motor cannons would work reasonably well in something like a D.520.

Although I do wonder if they would be better suited for specialized aircraft like interceptors, or some kind of variant of a D.520 meant for bomber-busting. A 3 x 20 mm setup (especially if they get the belt feed for the 404's in service faster) is more than enough to deal with any fighter, and still quite solid against twin-engined aircraft; which raises the question of why a 30/33 mm with limited ammo capacity would be necessary.

 

[z42]

Although I do wonder if they would be better suited for specialized aircraft like interceptors, or some kind of variant of a D.520 meant for bomber-busting. A 3 x 20 mm setup (especially if they get the belt feed for the 404's in service faster) is more than enough to deal with any fighter, and still quite solid against twin-engined aircraft; which raises the question of why a 30/33 mm with limited ammo capacity would be necessary.

3x20mm Hispanos would likely be the heaviest armed single engine fighter in the world in 1941 (assuming they would work reliably at that point). And still perfectly respectable in 1945.

 

[Bretoal2]

Yaks were fitted with 20 mm, 23 mm, 30 mm, 37 mm and 45 mm motor cannons. Khazanov and Gordon in Red Star Volume 5 note a single Yak-9 that was converted to use a 57 mm motor cannon as well. Considering this, it's a pretty reasonable conclusion that the MAT and APX motor cannons would work reasonably well in something like a D.520.

Although I do wonder if they would be better suited for specialized aircraft like interceptors, or some kind of variant of a D.520 meant for bomber-busting. A 3 x 20 mm setup (especially if they get the belt feed for the 404's in service faster) is more than enough to deal with any fighter, and still quite solid against twin-engined aircraft; which raises the question of why a 30/33 mm with limited ammo capacity would be necessary.

The "moteur-canon" concept assumes a hollow propeller shaft with an internal diameter larger than that of the integrated weapon.

Yes... but that's not enough!

The propeller hub and the entire blades control system must also have a large-diameter central hole. This isn't simple.

And in any case, this concept remains a single-weapon system. Ultimately, the choice of a twin-engined, multi-gun aircraft in the nose isn't such a bad one.

In France, this could have been the Sud-Est 100 with G&R 14Rs, but without its unnecessary complications (landing gear, wooden wing structure, etc.).

 

[tomo pauk]

The "moteur-canon" concept assumes a hollow propeller shaft with an internal diameter larger than that of the integrated weapon.

Yes... but that's not enough!

The propeller hub and the entire blades control system must also have a large-diameter central hole. This isn't simple.

Agreed.

And in any case, this concept remains a single-weapon system. Ultimately, the choice of a twin-engined, multi-gun aircraft in the nose isn't such a bad one.

In France, this could have been the Sud-Est 100 with G&R 14Rs, but without its unnecessary complications (landing gear, wooden wing structure, etc.).

Having the working G&R 14R means they can have a single engine per a fighter and still have a lot of firepower, while not sacrificing the performance.

 

[bf109xxl]

The propeller hub and the entire blades control system must also have a large-diameter central hole. This isn't simple.

This is relatively simple, compared to other problems encountered when mounting a large caliber gun on a motor - primarily, ensuring structural strength at high recoil. In general, any gun larger than 23mm caliber was redundant against German aircraft. How important big guns were for ground attacks is a question. Judging from Soviet pilots' accounts, they (ok, the most of them) were not thrilled with the heavy guns on Soviet fighters and ground attack aircraft, with perhaps one exception, the P-39.

 

[Bretoal2]

Having the working G&R 14R means they can have a single engine per a fighter and still have a lot of firepower, while not sacrificing the performance.

A single-engined fighter with a G&R 14R, that is a Bloch 157... A radial engine is obviously not compatible with the "moteur-canon" concept, but with its two wing guns firing outside the prop circle - therefore firing at maximum rate since not slowed down by synchronization - the Bloch could have remarkable firepower, like its predecessors, the MB 152 or 155.