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Subject: Aircraft Weapons and launch platforms, P-51 Mustang and P-38 Lightning.
heraldabc    12/22/2010 4:13:04 PM
Hypothesis: within the detection range of an engagement envelope there are two operation and decision cycles that are separate local events and that are mutually dependent upon each other. One local event is the launch platform which is the carriage and deploy mechanism. The other local event is the weapon as it operates across the interval from the launch platform to the target. The nature of the launch platform and the nature of the weapon act upon each other as an effectiveness ratio in doing work on the target. For this hypothesis we will use two concrete examples, the P-51 Mustang and the P-38 Lightning and discuss the shortcomings each platform had to the ideal solution that each tried to solve from its common military user perspective. Preliminary comments and questions welcome. H.
 
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doggtag    Luftwaffe heavies   12/23/2010 7:26:24 PM

I know this is O/T but i'd be interested to hear Herald's/Yelli's view on whether the germans should have developed a heavy bomber? Having done so would it have fundamentally altered the dynamics (range and payload) of the Battle of Britain, or more importantly the Eastern Front.


 





The Germans did have some heavy bomber designs,
He-177 (had follow-on designs such as the -277, with four props instead of two),
some of which certainly could've created severe headaches for British and Russian industry
if longer-ranged German heavies (in large numbers) 
could've flown deeper into Allied territory...
but there again, the Germans could've suffered at the hands of Allied fighters (especially thanks to British radar) 
and have had no long range fighter support, just like the Allies initially discovered early in the War when doing heavy raids into Germany.
 
A question on that could be: as a defensive measure, would British and Russian re-allocation of resources and hardware into defending industrial sectors from heavy bombers (the need for point fighters and flak)
have diverted precious resources and hardware away from areas where it was more desperately needed,
enough to make German operations in those areas where they were defeated,
be perhaps less of a victory there then for Allied forces?
 
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YelliChink       12/23/2010 7:46:22 PM

Quote Herald:
Compared to British, Italian, Japanese, and French supercharger tech, the Germans were a full development cycle behind. If you noticed, I already said that US supercharger tech was crap? Turrbo-chargers  were a different story.

===================
 
Any readings on this?
 
Japanese Ki-61 with Japanese version of DB 601 isn't any better than German version ones. Italy's best fighter MC202 and MC205 use essentially Italian version of DB601 and DB605. I'm not sure about French, but wasn't their development ceased after Dewoitine 520 and that aircraft was slower than BF-109E3? I don't doubt that they might all have better and newer design of superchargers than ze Germans, but Germans have improved their superchargers overtime. By 1944 the superchargers used in DB605 might have roots in the same one used in 1938, but it was revised only God knows how many times.
 
Since I have never seen drawings of the actual design. I'm open to accept that my observation may be flawed.
 
BTW, the F7F is unfair. It wasn't flying and hasn't been deployed until 1943 and 1944.
 
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heraldabc       12/24/2010 1:03:03 AM



Quote Herald:

Compared to British, Italian, Japanese, and French supercharger tech, the Germans were a full development cycle behind. If you noticed, I already said that US supercharger tech was crap? Turrbo-chargers  were a different story.

===================

Any readings on this?

 
The problem is that some might confuse the German solution to their inferior supercharger tech with the baseline engine tech itself. The Germans tended to build larger  displacement engines to obtain equivalent kilowatts work output.as compared to a British or American or Japanese engine. The packages that the Germans sold their allies of course included the mated superchargers to the specific engines.
Japanese Ki-61 with Japanese version of DB 601 isn't any better than German version ones. Italy's best fighter MC202 and MC205 use essentially Italian version of DB601 and DB605. I'm not sure about French, but wasn't their development ceased after Dewoitine 520 and that aircraft was slower than BF-109E3? I don't doubt that they might all have better and newer design of superchargers than ze Germans, but Germans have improved their superchargers overtime. By 1944 the superchargers used in DB605 might have roots in the same one used in 1938, but it was revised only God knows how many times.

Not the point about the interrupted development due to invasion of German illegal immigrants, but the fact is that the Hispamo Suiza H12Y-47 was a properly clutched and impeller speed band ranged two stage supercharger-boosted engine.
 
   
Since I have never seen drawings of the actual design. I'm open to accept that my observation may be flawed.


A note on the supercharging system.

Compared to the two-stage two-speed and turbo-charged engines of the western powers it is im-pressive what Daimler-Benz could achieve with the single-stage DB 605. By comparison the two-stage Merlin engines had a rated altitude ranging from approx. 5.8 km to 7.9 km. At the combat al-titudes of 1944 the performance of the DB 605 rivalled that of the high altitude Merlins 60 and 70 series of the Spitfire and the Mustang.

While the conventionel mechanical superchargers consisted of one or two compressors driven via a two-speed gear, Daimler-Benz utilised an ingenious barometricly controlled hydraulic clutch which adjusted the compressor speed and thus the charging of the engine according to the needs at a given altitude.

The conventional method results in a relative loss in efficiency below rated altitude, because the compressor uses energy to produce surplus charging. A graphic presentation of engine output relative to altitude would show a "saw-touth" line: the output in low gear rising with altitude until reaching the rated altitude, then output falls until the high gear kicks in, when the output again rises the rated altitude is reached.

In comparison the Daimler-Benz system is more flexible. A graphic presentation would show a smooth shallow curve. A source of efficiency loss with this system being progressive heating of the oil as pressure in the clutch builds with altitude.

 It took them six years and 14 steps to get there.
 
BTW, the F7F is unfair. It wasn't flying and hasn't been deployed until 1943 and 1944.
 
When was the P-51D flying in force? http://www.strategypage.com/CuteSoft_Client/CuteEditor/Images/emsmilep.gif" align="absmiddle" border="0" alt="" /> 1944.
 
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cwDeici       12/24/2010 4:01:45 PM
Just read the first few posts and tuned in to say its a nice read.
Thanks for keeping things simple, I'm just about able to get some of the gist.
 
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cwDeici       12/24/2010 4:04:05 PM
Oh and kudos on the great topic and the civilized discussion here.
 
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heraldabc       12/24/2010 5:12:35 PM
Birch, David. Rolls-Royce and the Mustang. Derby, UK: Rolls-Royce Heritage Trust, 1987.
 
Am reading this. Actually it turns out that the stupid generals (Gemeral Carl Spaatz of the Eighth Air Farce and Vice-Chief of the Air Staff, Air Marshal Sir Wilfrid Freman of the RAF) yelled their heads off at their respective civilian leaderships to Merlinize the P-51. Start around pp87-88 for that story.#
=======================================================================================
#Aside from the Curtiss Wright and the GM lobbies, (the lost GM Allison engine production contracts for Mustang engines were worth a hundred million dollars to Packard and RR and any hopes for a follow on Curtiss fighter went out the window when the Packard engined Mustangs showed up.) there was the machine gun versus auto-cannon question. I seriously doubt that the problems the US had with her bungled copies of the HS 404, which were severely compounded with the Mustang's wing flexion and vibration issues could be fixed. The cannons jammed and overheated because they could not heat dump and their feeds did not like the paths that NAA and British armorers were forced to design into the wings to fit. Even the Brownings jammed, until Army Ordnance decided on NACA advice to tutn the MG feed vertical instead of horizonatal so that gravity and torque [angular acceleration] forces could help eleminate the stove pipe jams. A bigger Browning with more mechanical belt pull action could have solved that problem.
 
There's more, but its Christmas and we need to save something for later.
 
H.
 
           
 

H
 
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heraldabc    Brainfart.   12/24/2010 6:35:16 PM
That should read canted to vertical instead of horizontal to vertical. The belt path in the Browning was corrected to a straight line pull instead of an angle so that the the gun would not hang up during extraction.
 
H..      
 
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Reactive       12/24/2010 9:04:36 PM
Happy Chirstmas everyone!
 
R
 
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heraldabc    I hope your Christmas was enjoyable.   12/26/2010 6:04:32 PM

Happy Chirstmas everyone!

 

R


Choose your weapon for the P-51. A little mathematics is presented for the armchair air staff out there.

Hypothetical Browning 20 mm cannon (modeled on the Japanese HO-5.)

Effective range with 3 degree fall @ 500 meters.

cyclic rate: 14 rds/sec

mass rate: 1.4 kg/sec

muzzle energy: 472 kW

mass of weapon:35 kg.

projectile velocity at muzzle: 750 m/sec

mass of 30 seconds of ammunition

----------------164 gram per projectile

----------------300 gram all up cartridge

----------------4,200gram per second mass expended (projectile, propellant and case)

36 kg per 100 round belt = 7 seconds of firing time.

155 kg. mass of 30 seconds cyclic of ammunition per gun

35 kg. mass of weapon

190 kg. mass of weapon package

Baseline optimized armament=4 cannon 52 projectiles per second at 6.56 kg/sec mass. With weapon package of 135 kg per mount is ~ 20 seconds

Effective range with 3 degree fall @ 500-550 meters

Hispano AN/M2 .

cyclic: 10 rds/sec

mass rate: 1.354 kg/sec

muzzle energy: 503 kW

mass of weapon: 44 kg

projectile velocity at muzzle: 830 m/sec

mass of 30 seconds of ammunition:

----------------130 gram projectile

----------------300 gram all up cartridge

----------------4,200gram per second mass expended (projectile, propellant and case)

36 kg per 100 round belt = 10 seconds of firing time.

108 kg mass of 30 seconds cyclic of ammunition per gun:

44 kg mass of weapon

152 kg weapon package per mount

Baseline optimized armament=4 cannon 40 projectiles per second at 5.416 kg/sec mass. With weapon package of 135 kg per mount is ~ 25 seconds firing time

Effective range with 3 degree fall @ 500-600 meters

Browning 13 mm AN/M2

cyclic: 15 rds/sec

mass rate: .91 kg/sec

muzzle energy: 230 kW

mass of weapon: 45 kg.

mass of 30 seconds of ammunition:

projectile velocity at muzzle: 850 m/sec

----------------48 gram projectile

----------------105 gram all up cartridge

16 kg for 100 round belt = 6.67 seconds firing time.

91 kg mass of 30 seconds cyclic of ammunition per gun:

45 kg mass of weapon

146 kg weapon package per mount.

Baseline optimized armament=6 machine guns 90 projectiles per second at 5.46 kg/sec mass. With weapon package of 90 kg per mount (total mass available if you haven't noticed is 540 kg for thr P-51 in its wing stations - evenly divided its ~ 15 seconds firing time

Now then we see the tradeoffs in the three weapon choices?

What would you choose if it worked? Pick one and defend your choice.

H.
 
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JFKY    As a traditionalist   12/27/2010 2:16:27 PM
I'll opt for the 6 12.7mm's...As one Website says, it's "Effective", not necessarily "Efficient."  Yes the USN wanted to move to 2cm weapon and failed to do so, but the 12.7mm served the US, well.  For what the US attacked, tanks, trucks, Light/Medium Bombers (Especially the Japanese Bombers), Fighters the 12.7mm HMG was more than adequate.  No need to waste resources on developing a new weapon and a new ammunition trail.  The 12.7mm did what needed doing...
 
Sure if you're a German you need to develop the Mk213C as soon as possible, in the 2cm and 3cm variants.  The Germans were attacking Heavy Bombers and Night Attackers, they needed the extra "oomph" to bring down the Heavies, or the A/c in fleeting attacks.  The US and the RAF. less so.
 
For the RAF the choice is 7.7mm or 2cm, realistically I'd go 2 cm.  And since we have the Hispano-Suiza I'd go with that.
 
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