Author Topic: P38J - 14 rockets? (Read 1848 times)

Guppy35 · « **Reply #15 on:** October 06, 2005, 10:55:35 PM »

Quote

Originally posted by Ack-Ack
Is this a D or an E model?

ack-ack

That's a D model. Just the 4 MGs.

Also note the lack of the curved fillet where the wing meets the cockpit pod. That apparently made a huge difference when they added it as it prevented the tail buffet they'd been dealing with previously.

Guppy35 · « **Reply #16 on:** October 06, 2005, 10:57:43 PM »

Quote

Originally posted by Ack-Ack
Anything that shows that this gun package was more effective than the quad .50s and 20mm Hispano?

ack-ack

According to the 8th FG history, the 80th FS said it was devestating in it's effectiveness but was dropped for some reason.

I suppose it was just to much work to modify more, or use it on a larger scale?

Ack-Ack · « **Reply #17 on:** October 06, 2005, 11:41:19 PM »

OK, so all the design specs that I've seen for the D that showed the default guns package as a 37mm or 23mm and 4x .50 cals was only on paper and in practice the D only had 4x .50's correct?

One more question for you, why would they go in favor of the 20mm Hispano instead of the 37mm Oldsmobile cannon? Was the Hispano that much better than the larger Oldsmobile cannon?

ack-ack

Guppy35 · « **Reply #18 on:** October 07, 2005, 12:56:20 AM »

Quote

Originally posted by Ack-Ack
OK, so all the design specs that I've seen for the D that showed the default guns package as a 37mm or 23mm and 4x .50 cals was only on paper and in practice the D only had 4x .50's correct?

One more question for you, why would they go in favor of the 20mm Hispano instead of the 37mm Oldsmobile cannon? Was the Hispano that much better than the larger Oldsmobile cannon?

ack-ack

Yep the D was supposed to get that cannon but it never did.

I'm guessing they went with the 20mm for the rate of fire. The 37mm probably wouldn't have been too effective in air to air, with the slow rate of fire and velocity.

Seems like I recall P39 drivers who had that gun, saying they could see it almost drop out of the end of the barrel some times.

Captain Virgil Hilts · « **Reply #19 on:** October 07, 2005, 06:02:37 AM »

Quote

Originally posted by Ack-Ack

One more question for you, why would they go in favor of the 20mm Hispano instead of the 37mm Oldsmobile cannon? Was the Hispano that much better than the larger Oldsmobile cannon?

ack-ack

Everyone I talked to who flew anything with the 37MM said it sucked, the velocity was low, the trajectory was terrible, and it jammed constantly. The 20MM was light years ahead.

killnu · « **Reply #20 on:** October 07, 2005, 01:52:16 PM »

fly a yak9t and they have the 37mm...maybe not same company, but same trajectory and such...what ive read about that was that the 37mm was unreliable and was succeptable to malfunction more than the 20mm.

Murdr · « **Reply #21 on:** October 07, 2005, 02:32:11 PM »

Quote

Originally posted by Ack-Ack
OK, so all the design specs that I've seen for the D that showed the default guns package as a 37mm or 23mm and 4x .50 cals was only on paper and in practice the D only had 4x .50's correct?

One more question for you, why would they go in favor of the 20mm Hispano instead of the 37mm Oldsmobile cannon? Was the Hispano that much better than the larger Oldsmobile cannon?

ack-ack

US policy makers didnt buy into needing a cannon of a size suitable for platforming on a plane between ww1 and ww2. When the war in europe finally caused a concern they were behind the curve. If I remember correctly that particular cannon was a knock off of an older french gun, and wasnt up to par with the contempary technology. I think there were supply issues too.

Murdr · « **Reply #22 on:** October 07, 2005, 02:46:47 PM »

Akak, if you have Bodie's book, there are a couple of pages devoted to the politics of finding a cannon armament for US planes. Ch 8 Weapons of War. (Took me a bit to remember where I had gotten my fuzzy details from

)

Karnak · « **Reply #23 on:** October 07, 2005, 03:35:12 PM »

Quote

Originally posted by killnu
fly a yak9t and they have the 37mm...maybe not same company, but same trajectory and such...what ive read about that was that the 37mm was unreliable and was succeptable to malfunction more than the 20mm.

Balderdash. The NS-37 on the Yak-9T has a vastly higher muzzle velocity than the Olds 37mm. Saying they are the same is like saying the Hispano is the same as the MG/FF on the Bf109E ot the Type 99 Model 1s on the A6M2 because all three guns are 20mm.

HoHun · « **Reply #24 on:** October 07, 2005, 04:44:42 PM »

Hi Ack-Ack,

>One more question for you, why would they go in favor of the 20mm Hispano instead of the 37mm Oldsmobile cannon? Was the Hispano that much better than the larger Oldsmobile cannon?

Have a look at Tony's site:

http://www.quarry.nildram.co.uk/WW2guneffect.htm

Based on Tony'd data, I calculated the Hispano II's total firepower as 1.06 MW (kinetic and chemical energy at the muzzle), while the 37 mm M4 had only 0.91 MW.

The Hispano cannon only weighed 50 kg compared to 91 kg for the M4, and while I don't know the total cartridge weight for the 37x145R rounds, I suppose an equivalent ammunition supply would have been roughly twice as heavy as the Hispano's, too ... only that the M4 didn't use ammunition belts but a mechanized feed that was yet heavier and only held a limited number of rounds so that it would be impossible to actually load an equivalent supply of 37 mm shells.

So the use of the Hispano cannon appears to be a very good decision.

On the other hand, one has to wonder why only one Hispano was used.

Historical battery:

- 4x .50 Browning M2 - 500 rpg - 336 kg - 100% firepower (38 s of fire)
- 1x Hispano II - 150 rpg - 87 kg - 94% firepower (15 s of fire)
- Total: 423 kg 194% firepower

Cannon-only battery:

- 2x Hispano II - 281 rpg - 238 kg - 187% firepower (28 s of fire)

That would have yielded about the same firepower at just 56% of the weight. In fact, you could have mounted a third Hispano for a substantial firepower increase and still have saved a few kilograms. The nose of the P-38 certainly should have offered enough space!

Regards,

Henning (HoHun)

Murdr · « **Reply #25 on:** October 07, 2005, 05:25:31 PM »

Quote

Originally posted by HoHun

- 2x Hispano II - 281 rpg - 238 kg - 187% firepower (28 s of fire)

That would have yielded about the same firepower at just 56% of the weight. In fact, you could have mounted a third Hispano for a substantial firepower increase and still have saved a few kilograms. The nose of the P-38 certainly should have offered enough space!

HoHun · « **Reply #26 on:** October 08, 2005, 08:51:03 AM »

Hi Murdr,

>http://479th.jasminemarie.com/images/2-20mm.jpg

Wow! :-) Great gun platform! Is there a story behind the photograph? Why didn't they build all P-38s that way?

Regards,

Henning (HoHun)

killnu · « **Reply #27 on:** October 08, 2005, 10:57:24 AM »

sorry karnak, didnt mean to get your panties in a bunch there. point i was tryin to make, yak9t has a 37mm....fly it and you will see what it is like. im thinking the trajectory of the yaks 37mm and the olds 37mm can not be that much different. and if the olds 37mm rof is any slower than the yaks 37mm, guess you would need a sun dial to time it. other than that, like my post said, from what ive read the olds 37mm was succeptable to malfuntion and therefore not as reliable as the 20mm.

HoHun · « **Reply #28 on:** October 08, 2005, 11:04:59 AM »

Hi Killnu,

>im thinking the trajectory of the yaks 37mm and the olds 37mm can not be that much different. and if the olds 37mm rof is any slower than the yaks 37mm, guess you would need a sun dial to time it.

The Yak's NS37 had 230% the firepower, 150% the muzzle velocity and 160% the rate of fire of the P-39's M4 cannon.

Regards,

Henning (HoHun)

Murdr · « **Reply #29 on:** October 08, 2005, 02:22:22 PM »

Quote

Originally posted by HoHun
Hi Murdr,

>http://479th.jasminemarie.com/images/2-20mm.jpg

Wow! :-) Great gun platform! Is there a story behind the photograph? Why didn't they build all P-38s that way?

Regards,

Henning (HoHun)

Its one of a few arrangments they tested for the XP-49 program using modified P-38s (G-5-LO in the photo). The XP-49 program was abandoned after problems getting the envisioned powerplant forced a downgrade that only provided marginal performance over the original P-38.