P-51 tank busters?

[parsifal]

The niftily entitled 'ORS 2nd TAF/No.2 ORS 21st Army Group joint report No. 3 (1945)' paints a more realistic picture of what happened operationally rather than in trials. It calculated that to have a 50% chance of hitting a German tank (it quotes a Panther) 140 rockets, equivalent to 18 sorties, were required.

Thats roughly the same odds actually. 4% success per sortie is equivalent to 200 rockets per kill on avcerage, whereas 140 rockets means an estimated success rate of 5.8% per sortie, assuming 8 rockets per sortie. Im not disagreeing with the point you are making, Im agreeing with it, but just noting the maths is wrong.

 

[stona]

The arithmetic is a bit tricky. 140 rockets were required for a 50% chance of hitting the tank. How many were needed for a 100% chance? Is it double? I think it might be more, but it's been far too long since I did any statistics
I think that we are all agreed that it required an awful lot of rockets to have a reasonable chance of actually hitting a tank or any other small target !
Cheers
Steve

 

[soulezoo]

Also, within statistical analysis, I will note here that if one were to send those 18 sorties, it does not mean that a tank would be hit. Maybe 3 or 4 tanks are hit; maybe none at all.

With each sortie, before the toggle is moved, there remains that 4% chance. It does not mean that while sorties 1-8 (for instance) were unsuccessful that the next ten have higher odds for success. Each following sortie has just that 4%.

Like with roulette... and you are betting odd/even or red/black. Either choice has a 50% chance of hitting (actually less due to ought and double ought). But that 50% is with each spin. If you hit "odd" 10 times in a row, that does not mean the next spin has a greater chance to hit "even". It is still 50%.

 

[parsifal]

ah statistics....my favourite subject at school

 

[pbehn]

Also, within statistical analysis, I will note here that if one were to send those 18 sorties, it does not mean that a tank would be hit. Maybe 3 or 4 tanks are hit; maybe none at all.

With each sortie, before the toggle is moved, there remains that 4% chance. It does not mean that while sorties 1-8 (for instance) were unsuccessful that the next ten have higher odds for success. Each following sortie has just that 4%.

Like with roulette... and you are betting odd/even or red/black. Either choice has a 50% chance of hitting (actually less due to ought and double ought). But that 50% is with each spin. If you hit "odd" 10 times in a row, that does not mean the next spin has a greater chance to hit "even". It is still 50%.

That is completely true but not the task in question. The tank is the banker and the gambler is the fighter. Someone betting only on red is playing double or quit you must have in the bank enough to cover his statistical luck. In the case of tanks in Normandy the odds wernt 50/50 but 96/4 (or similar) in the tank commanders favour. The problem is each AC carries 8 rockets so it is very easy to be convinced your luck is about to run out.

 

[kool kitty89]

4% chance of hitting a tank comes from Price, but I don't have his source.

The niftily entitled 'ORS 2nd TAF/No.2 ORS 21st Army Group joint report No. 3 (1945)' paints a more realistic picture of what happened operationally rather than in trials. It calculated that to have a 50% chance of hitting a German tank (it quotes a Panther) 140 rockets, equivalent to 18 sorties, were required.

Rockets may not have been effective in destroying armour or other pin point targets, but they could be devastating against larger targets, columns of soft skinned vehicles and troop concentrations. The same ORS report concluded that only 24 rockets (3 sorties) were required for a 50% chance of destroying an 'army hut' for example.

There are many reports of the morale effect of air attacks on defending German units, not just by rocket, strafing could have a similar effect. One report from the US 9th Infantry Division in Normandy sums this up. "Every time we have an air mission the rate of surrender goes up"

Wouldn't those 'soft but large/heavy' targets also be among the most effective for the 40 mm HE shells the Vickers S sported? (or the P-39's M4 cannon for that matter, I'm not sure about the MK 108, particularly with mine shells vs harder cased steel HE shells)

And how much more effective were those 40 mm shells than a higher volume of 20 mm hispano shells? (4 Mk.II hispanos have 10x the rate of fire of 2 Vickers S guns) How would they compare in the anti-rail and anti-shipping roles? (including against the heavier, slow firing 57 mm cannon the Mosquito carried)

For that matter, might it have been useful to install the 37 mm M4 for use against heavy ground targets in the B-25 and A-20? (not the anti-tank role, but rail and heavy transport vehicles or light armored vehicles) The manually re-loaded magazine arrangement attempted on the YFM-1 might have been more useful in a nose/belly mounting on bomber/attack aircraft. (prior to the continuous belt feed mechanism of the M10)

In American service, the M4 also had one other advantage: it was reliable while the Hispano continually proved not to be. (so you've got a wider gap between .50 and 37 mm performance than the British 20 mm vs 40 mm) The 23 mm Madsen gun the USAAF was considering for a time might have been a better option for many uses, but it seems no production license was ever acquired.

 

[stona]

On an average pass 32 of the 120 20mm cannon shells fired by a British four cannon fighter bomber would hit a vehicle sized object. I can't think of any WW2 soft skinned or even semi-armoured vehicle or train that could survive that. I can't see any reason at all to use instead a heavier weapon (like the Vickers with a maximum of 15 rounds per gun) even with the highest probability of hits claimed by the squadrons who used them.
Also, we are talking about fighter bombers here. The four 20mm cannon mounted by the RAF's fighters also proved formidable armament in an air to air role. Every weapon system has to be a compromise and a Typhoon armed with 4 x 20mm cannon was a very good compromise indeed. Any aircraft mounting some of the heavier armament suggested would have itself needed an escort of fighters, denying the force multiplication that the fighter bomber brings.

Whether the Americans might have adopted cannon armament earlier, during WW2, is a moot point. They were happy with the considerably lesser hitting power of their 6 or 8 .50 calibre machine guns, the primary role of their fighters in the ETO being to destroy the Luftwaffe's fighters, for which machine guns were more than adequate. In the ground attack role they did try various options (rockets, bazookas, napalm) but to a large extent their fighter bombers were just that...fighters that dropped a bomb or bombs and strafed.

Cheers

Steve