Some What-Ifs for the First Generation Jets

[riacrato]

I am not sure it's question of being able to hit with the 360 rounds as it is combat persistence. Depending on wither you believe a "burst" is 2 seconds or 3 seconds (or another time) the 262 has 3 or 4 bursts before the lower cannon are out while a Spitfire has 4-6 bursts. A Tempest has even more and both are behind the P-51s and P-47s.
While many planes returned with guns unfired other planes either exhausted their ammo supply on one target or in a few cases engaged multiple targets. Yes it is more important for escorts but the 262 was good for 3-4 firing passes per flight on the bombers, then it is out of ammo.

Some American pilots managed multiple kills in their first combats, in part because they had 20-30 seconds of firing time.

And 3-4 passes on a bomber formation is pretty much on the far end of what was actually done in reality. Much more likely was 2 passes max and then use all energy to go home before escort fighters catch you in a bad position.

 

[davebender]

If you cannot hit something as large and slow as a B-17 on a single pass then how did you pass the fighter pilot course?

 

[Erich]

David that really has nothing to do with passing the pilots course fact is the jet was just that, a jet of tremendous speed even Walter Schuck with his first missions was not able to latch on to the rear of the bomber, take aim and fire his 3cm's before he was long gone past his victim.

Granted it took some getting use to if you outlived the US escorts compared to the prop driven machines the 109 and Fw 190's which could almost sit on their props as they pumped rounds into the tail and inboard engines on the 17's and 24's.

 

[tomo pauk]

Erich, was it easier to hit B-17 in a head-on attack with 109/190 (armed with 20mm mostly), or during tail chase with 262?
Was the meeting speed main hindrance, or the nature of 30mm low velocity shells that required excellent aiming/close-in shots?

 

[glennasher]

As for Bell handling the P-59/59A production, if I hazarded a guess, it's because they had the production capacity lacking in other plants at the time. NA was busy making P-51s, Republic making P-47s, etc. Bell was making P-63s, but not a large number of them, and probably had the room to make the new aircraft.
They were probably the only plant not really busy with other matters.

 

[Erich]

Tomo

the frontal attack was somewhat suicidal with the closing speeds and then having to go from front to rear into the bomber boxes before the LW pilot could bank away up or down he usually got a face full of .50 rounds

the rear attack with prop driven is that the LW pilots could slow down and only deal with the tail gunners position, once this was eliminated and due to the experience of the LW pilot they then could take out the inboard engine or engines on one wing. The 262 attack if not using the R$M was attack or start the attack from above drop down and then a fast upward ascent firing the 3cm into the tail and inboard engines and wing roots if US escorts were not on their tail trying to chase the jet pilot(s).

E ~

 

[davparlr]

As for Bell handling the P-59/59A production, if I hazarded a guess, it's because they had the production capacity lacking in other plants at the time. NA was busy making P-51s, Republic making P-47s, etc. Bell was making P-63s, but not a large number of them, and probably had the room to make the new aircraft.
They were probably the only plant not really busy with other matters.

You are probably correct but I am sure Lockheed would have been thrilled to do the job. Unfortunately I think Bell was the poorest choice. Maybe that was why they were not busy!

 

[davparlr]

I have read where the speed of overtake with the Me-262 was a problem. So climb into the cockpit and see what happens. You are at 30000 ft in an Me-262 flight flying at over 500 mph. 5000 ft. below you is a B-17 formation flying at 220 mph (?). You look around, there are P-51s at your altitude and some below. You start your dive, and since speed is your life, your going balls to the wall, or, as my RR engineer dad would say, balling the jack. Your speed is high, 500+ mph. The P-51 have seen you and are diving down and the ones below are closing in from the side. They are desperately trying to break up your attack by attacking you and crossing in front of you. If you slow down the P-51s above you will be on you. Your closure rate on the B-17s is over 300 mph. You know you must be within 1000ft to be accurate with your slow velocity MK 108 cannons. Also, too long a firing run will result in the destruction of your target along with you and your aircraft. Reaction time and maneuver time to avoid a collision is guessed to be about a second. So at a 300 mph closure speed (440 ft/sec), the time it takes to cover 1000 ft is about 2.5 seconds minus 1 second to avoid collision, you have about 1.5 seconds to steady the plane and accurately fire a burst, one thousand one, one thousand...... BREAK! Oh, did I say that there are a bunch of alligators trying to eat your tail off along with .50 caliber fireballs coming at you from the four ship B-17 formation? You could probably shoot earlier, but still, closure rate does not much allow much time to make corrections or decisions.

I am sure this was no picnic.

 

[riacrato]

davparlr, the MK108 can hit targets beyond 1000ft. It was zeroed at 500 or 550m iirc and I assume for a reason. The tactic was often like Erich described and the Me 262 pilots would start firing the cannons at around 500m distance (I assume most of the time until either ammo was empty or they had to break off because they got too close).

The MK108 still has around 2/3 the mv of the MG151/20 and likely keeps speed and energy better due to the heavier shell. It is shorter ranged, but not as extreme as you make it out to be.

Surely enough there were weapons that could be fired from a more comfortable distance, but even a B-17 is but a speck at ranges beyond 500-600m. Firing a weapon from a moving platform at a moving target at such ranges will make a hit pretty unlikely. So unless you can linger there for a long time (= slowing down to almost the same speed as your target) or can fire extremely rapidly without messing up aim due to recoil it just doesn't make a lot of sense. The LW sure tried that strategy and it turned out to not work (Zerstorer Me 110-410s). I don't think any WW2 era cannon was capable of that. Maybe MG213s (the 20mm version) combined with gyro gunsights, but those were not there yet.

 

[tomo pauk]

Thanks for the reply, Erich.

Tomo

the frontal attack was somewhat suicidal with the closing speeds and then having to go from front to rear into the bomber boxes before the LW pilot could bank away up or down he usually got a face full of .50 rounds

the rear attack with prop driven is that the LW pilots could slow down and only deal with the tail gunners position, once this was eliminated and due to the experience of the LW pilot they then could take out the inboard engine or engines on one wing. The 262 attack if not using the R$M was attack or start the attack from above drop down and then a fast upward ascent firing the 3cm into the tail and inboard engines and wing roots if US escorts were not on their tail trying to chase the jet pilot(s).

E ~

Despite the risks for a head-on pass, the threat was such it provoked installation of nose turrets for both B-17 -24. I know that it took skill courage to perform it, with closing speeds in order of 500-600 mph.
Which bring us to jet (Me-262) issue - it was closing fast on 4mot, yet closing speed was 300-400 mph, so that was less an issue compared with what Fw-190 drivers were doing from 1942/43 (while performing head on pass).

Now about armament - 262 was equipped with 5-10 times more firepower then German fighters from 1943, yet it was still looking for a 'sweet spot' in order to kill the bomber? If so, 4 x 20mm seem much better choice for the 262, benefiting from greater ammo count better shell trajectory (= greater hit chance).

 

[Shortround6]

For bomber killing the 30mm guns were better. The Germans had calculated that on average about 2% of rounds fired hit. Again that is average for all pilots. Experts do better, new pilots do worse. It took something like 15-20 hits of 20mm to bring down a 4 engine bomber, so 750-1000 rounds of 20mm were needed to to bring one down.
3-4 hits of 30mm projectiles were usually enough to bring down a bomber so an ammo capacity of 150-200 30mm rounds should be enough for one bomber kill, on average. It was easier to get a plane to carry the number of 30mm cannon needed plus their ammo than the number of 20mm cannon and their ammo. especially if you figure in the rate of fire.
Assuming 15 20mm hits needed and 750 rounds fired (best case for 20mm) you need SIX 20mm MG151/20s firing for 10 seconds to deliver the needed rounds.
Assuming 4 30mm hits needed and 200 rounds fired (not worst but not best case) you need TWO MK 108s firing at 600rpm firing for the same 10 seconds.
If you need 20 20mm hits you need EIGHT guns and 1000 rounds carried.

So a 262 needs 4-5 seconds of firing time for a kill (less for a cripple?).
Adjust as you see fit for closing speeds and firing opportunities but the 30mm guns had a big advantage for anti-bomber work.

 

[pbfoot]

I have read where the speed of overtake with the Me-262 was a problem. So climb into the cockpit and see what happens. You are at 30000 ft in an Me-262 flight flying at over 500 mph. 5000 ft. below you is a B-17 formation flying at 220 mph (?). You look around, there are P-51s at your altitude and some below. You start your dive, and since speed is your life, your going balls to the wall, or, as my RR engineer dad would say, balling the jack. Your speed is high, 500+ mph. The P-51 have seen you and are diving down and the ones below are closing in from the side. They are desperately trying to break up your attack by attacking you and crossing in front of you. If you slow down the P-51s above you will be on you. Your closure rate on the B-17s is over 300 mph. You know you must be within 1000ft to be accurate with your slow velocity MK 108 cannons. Also, too long a firing run will result in the destruction of your target along with you and your aircraft. Reaction time and maneuver time to avoid a collision is guessed to be about a second. So at a 300 mph closure speed (440 ft/sec), the time it takes to cover 1000 ft is about 2.5 seconds minus 1 second to avoid collision, you have about 1.5 seconds to steady the plane and accurately fire a burst, one thousand one, one thousand...... BREAK! Oh, did I say that there are a bunch of alligators trying to eat your tail off along with .50 caliber fireballs coming at you from the four ship B-17 formation? You could probably shoot earlier, but still, closure rate does not much allow much time to make corrections or decisions.

I am sure this was no picnic.

well worded and the the math was bang on

 

[davparlr]

davparlr, the MK108 can hit targets beyond 1000ft. It was zeroed at 500 or 550m iirc and I assume for a reason. The tactic was often like Erich described and the Me 262 pilots would start firing the cannons at around 500m distance (I assume most of the time until either ammo was empty or they had to break off because they got too close).

The MK108 still has around 2/3 the mv of the MG151/20 and likely keeps speed and energy better due to the heavier shell. It is shorter ranged, but not as extreme as you make it out to be.

Surely enough there were weapons that could be fired from a more comfortable distance, but even a B-17 is but a speck at ranges beyond 500-600m. Firing a weapon from a moving platform at a moving target at such ranges will make a hit pretty unlikely. So unless you can linger there for a long time (= slowing down to almost the same speed as your target) or can fire extremely rapidly without messing up aim due to recoil it just doesn't make a lot of sense. The LW sure tried that strategy and it turned out to not work (Zerstorer Me 110-410s). I don't think any WW2 era cannon was capable of that. Maybe MG213s (the 20mm version) combined with gyro gunsights, but those were not there yet.

Of course the example I gave has a lot of variables and probably inaccuracies since I am neither a fighter pilot nor a ballistics expert. However this illustration was meant, whether successful or not, to illustrate the rapidity and complexity of high speed combat in contested airspace. Not included here are other factors, pilot exhaustion, g loads, system monitoring (over speeding a jet aircraft in a power-on dive is very easy), etc., that makes the mission even more hazardous. Tick tock, tick tock, a couple of seconds to execute a successful attack, a couple of seconds to live or die. Can you make the right decision; can you make the right maneuver?