drgondog
Major
Incomplete reference to P-39. Lots of 4+ shooters in P-51and F6F. Also in F4F and P-47 and P-38. Zero in P-39.
Help with understanding a deflection shot?
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Thumpalumpacus
Captain
But it makes for a good story, especially if the author is providing the reader accurate bits of info during the action (something the movies could learn from).
It also gives us a groundhog sighting! No thread is complete without one.
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WriterGirl
Recruit
- 7
- Apr 20, 2021
Everyone has been so incredibly helpful in their explanations. Much appreciated.
Well, spill the beans, what are, or will you be writing?
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- #25
WriterGirl
Recruit
- 7
- Apr 20, 2021
Ha! Can't spill yet, but it's an article for Memorial Day. If it's published in the paper, I'll post a copy. Two of the men I'm writing about were WWII pilots, both KIA.
A few authors post here, good luck, keep us posted.
One Soviet ace (can't remember his name) has described his preferred attack against He 111. It was an attack from either side, "flat", gunfire buttons pressed just before the Heinkel's nose crosses the gunsight. The trick was to apply the rudder in the direction of the bomber's flight (probably compensating with the ailerons?). Shells/bullets would either damage the engine or rip the fuselage disabling the crew or both. Perfect 90-degree deflection, I think.
drgondog
Major
That is close to classic beam to stern "Pursuit Curve Approach" to gunnery instruction for towed target where the attacking aircraft breaks off firing at 630 to 7 o'clock. Otherwise closer to a snap shot with a small amount of 'swing. along target track - but neither rudder or co-ordinated rudder/aileron flight would work at close range to keep the burst ahead of the target for a good deflection shot. At 200mph the target is traveling ~300 feet per sec - the point in front where the burst has to be directed for a hit on the nose. The 'just before nose crosses' would in fact have to be more than 300 feet in front of the nose to compensate for time the bullet(s) travel to hit.
With a gyro sight there would be a continuously curving approach I believe. It would be difficult to adjust the range (I imagine a thumb switch would be used)
drgondog
Major
Set to Wingspan - most targets have nearly same length as span
As I understand it the problem with deflection shooting wasnt the basic principle of a deflection shot, it was that almost all pilots misjudged the range. So the "deflection" may have been correct for 200 yards but they were actually 800 yards away, as per drgondog's post the gyro sight helped with both issues.
That was from the memoirs of about 80 y.o. man, so his "just before" can be interpreted widely.
I see your point. Just not sure about 300 feet, since it depends on the firing distances, isn't it. Muzzle velocity is many times higher than the target speed and those pilots learned to fire at the closest range possible.
With the Allied sights you adjusted the size of a ring in the reflector sight that enclosed the wing span of the target (or length). Tables were used to get the scaling right.
Early German non gyro reflector sights had a circle. If the targets wing span filled the circle it was ten wing span away. 31.6m for a B17 would mean 316 meters. The pilot was expected to know the wing span of his targets and judge.. The allied sites allowed adjustment of the ring. This was a stedometric range finder.
I just don't know how the ring size was adjusted. Through a servo motor drive connected to a switch set on the joy stick would be best.
It didn't really work well till radar was used to range. The Luftwaffe did have a program to link a microwave range only radar to their gyro sights the Z42 and EZ45.
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Gentlemen
Certainly misestimating the range was/is a chronic problem with air-to air gunnery. The following is from "Combat Tactics in the Southwest Pacific Theater" by Capt. Thomas B McGuire Jr, dated May 4, 1944.
"Using the 70 mil sight, an enemy bomber will fill the sight at 300 yards, a fighter will fill half the sight. Unless he fills the sight to that extent, hold your fire, it just does not count beyond 300 yards." …. "If you take a shot in deflection, pull your sight through the enemy's line of flight. Misses are due more to shooting over or under than to improper lead." (bolded not in original)
As for the range, McGuire stressed that the closer to the target before firing, the better, and gave a rule of thumb to help estimate the range.
While McGuire is noted for his flying skills in the P-38, he did fly combat sorties with the P-39 in the Aleutians, so I suspect his comments on gunnery would apply to both single and twin engine fighters. Also, with the May 1944 publication date, this would be before the use of gyro gunsights.
FWIW
Eagledad
Certainly misestimating the range was/is a chronic problem with air-to air gunnery. The following is from "Combat Tactics in the Southwest Pacific Theater" by Capt. Thomas B McGuire Jr, dated May 4, 1944.
"Using the 70 mil sight, an enemy bomber will fill the sight at 300 yards, a fighter will fill half the sight. Unless he fills the sight to that extent, hold your fire, it just does not count beyond 300 yards." …. "If you take a shot in deflection, pull your sight through the enemy's line of flight. Misses are due more to shooting over or under than to improper lead." (bolded not in original)
As for the range, McGuire stressed that the closer to the target before firing, the better, and gave a rule of thumb to help estimate the range.
While McGuire is noted for his flying skills in the P-38, he did fly combat sorties with the P-39 in the Aleutians, so I suspect his comments on gunnery would apply to both single and twin engine fighters. Also, with the May 1944 publication date, this would be before the use of gyro gunsights.
FWIW
Eagledad
33k in the air
Staff Sergeant
- 1,219
- Jan 31, 2021
Note that the P-38 had the advantage of nose-mounted armament, and thus no complications in terms of harmonization/convergence distance.
Greg Boeser
1st Sergeant
Ditto the P-39. The wing guns were just there to make the plane less maneuverable.
Shortround6
Major General
WriterGirl,
First, welcome aboard. This is a great place to visit, share and learn. Second, I will attempt to answer your questions with regards to deflection shooting.
To start let's define a few things, like what exactly is the 90' (degrees) he is talking about. In the context of aerial combat there is a sort of common language used to describe aircraft in relation to each other. To begin imagine you are behind your target, looking right down his tail, you would be on the zero degree line or tail aspect in today's terms. Your target aircraft is the reference, and every 10 degrees is 1 aspect angle. 90' is a 9 aspect, and 180' (nose to nose) is a 18 or H aspect (depends on what your radar displays). This is also USAF, Brit, German, and pretty much everyone in the worlds definition, EXCEPT the USN and those who fly Hornets (looking at you Wes). Now to further define things, the aspect has a Left or Right, or L or R. Target A/C is heading north, and you are attacking from the West (of the target, which is sort of the sun in your universe), or heading Easterly, which means the aspect would be Left, or from the targets left side.
In your example, the attacker starts at 90', or 9 aspect angle and closed to 10', or 1 aspect. Imagine you are going East down a straight road in the desert, which has a crossing road ahead that runs perpendicular. As you are driving down your road, you notice a North bound car on the crossing road off to your right about 45 degrees. If that car is moving forward in your windows (from side window to corner of front window) that means he will get through the intersection before you. If he isn't moving fore or aft, you are going to get there at that same time, and if he is moving aft you will get through first. This is called Line of Sight (LOS). The road he is traveling down is his plane of motion, as the road you are on is yours. Since planes can maneuver in 3D, just imagine there is a rod going out the nose of his plane and that is where he is going. Same for you.
To gun someone you need to be in plane, in range, and in lead. This is the foot stomp information that your professors / teachers wanted emphasized!
In the example above, the attacker gets in "plane" (puts his plane of motion to intersect or cross that of the adversary), in order to cause closure to gun range. The attacker will be looking out the side window, doing small maneuvers to make sure adversary is moving forward (so they won't collide) to arrive at a point where his nose is in lead, in range, and in plane. The gun sight isn't used for this (in the F-15 there is a + sign where the gun is pointed, known as the gun cross) and this is put in front of the target (on his plane of motion). When in range you come down on the trigger, however prior to the target getting to your nose you come off the trigger as those bullets will pass behind the target.
In the example your offender starts at 90', or 9 AA, and finishes his intercept at 10' or 1 AA. That tells me he came on the trigger early (probably out of range) as it doesn't mention him overshooting to complete the intercept. I don't think he could be in range at 90', and turn tight enough to finish at 10' off the bandits tail.
From the Vals perspective and assuming straight and level flight, if he saw the inbound fighter it would be near the horizon, and in a series of small check turns (he would see the wing going up / down as the attacker sets up the shot). At some point the attacker would set his wings (finish maneuvering) and concentrate on any micro corrections and when to come down / pull the trigger. The Val would see the muzzle flashes and probably tracer if it's loaded. He has the option of pulling / pushing in an attempt to spoil the shot or crossing his fingers and hoping it's a big sky.
Also realize that as the Val flies along, the attacker will due to the intercept, flow / point towards the enemies tail which will put him into a tail chase, or at low angle off / aspect.
I hope this answers your questions.
Cheers,
Biff
Greg Boeser
1st Sergeant
I stand corrected.
Ring size was adjusted by twisting the throttle handle (like a motorcycle) for the Mk.IId pilot's sight and by using right/left foot pedals in the Mk.IIc gunner's sight.
In regard to how well it worked -- not as good as the radar sights but a hell of a lot better than everything that came before it.
