.50 cal machine guns vs 20 mm autocannons on US aircraft (1 Viewer)

Some aircraft use differential ailerons to combat adverse yaw. The ailerons go up more than the aileron going down, making the inside wing on the turn have more drag.
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The T-38 and C-141 were both flat footed aircraft except cross controlling when landing the C-141 in a cross wind.

Gliders are definately not feet off machines. More than once I have had to take control off an experienced pilot because they have totally lost their co ordination when first flying gliders.

I have read that if you can fly a sailplane, you can fly anything! I have been skiing at Sun Valley and it is amazing how much noise a sailplane makes when he makes a run overhead and you are on Mt Baldy.

renrich said:

I have read that if you can fly a sailplane, you can fly anything! I have been skiing at Sun Valley and it is amazing how much noise a sailplane makes when he makes a run overhead and you are on Mt Baldy.

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I tend to agree. I think sail plane pilots are more attune to the aerodynamics of flying that is obscured by an engine. I believe Sullenberger was a glider pilot. I have never flown in a glider.

One big advantage to being a sail plane pilot is that if you are in a light plane and lose the engine, you are used to flying without an engine.

davparlr said:

I have never flown in a glider.

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Try it, even if you only go up once I promise there is nothing like it.

You know, not a bad idea making pilots train to fly them first. I think you'd get a better understanding and feel of flying.

davparlr said:

I agree. Certainly the armor penetration appears off. I have tried to find ballistics tables for velocities of the .50 and 20 mm, but have been unsuccessful to my satisfaction. If the velocities are near correct, then so are my calculations, if they are not, then neither are my calculations.

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Ballistics tables are going to vary by projectile in each caliber. I have a few old figures. For a 753gr. BT projectile with a Mv of 2900fps(?) the times of flight to 600yds. and 1000yds. Are given as 0.72 and 1.32 seconds. Angle of departure is given as 14mins and 30 mins for the two ranges. Remaining velocity is given as 1950fps and 1575fps.
For a 20mm projectile of 2000gr. And a MV of 2750fps (?) the corresponding figures are: Time of flight, 0.84sec and 1.71 sec. Angle of departure, 17 min and 42 min. Remaining velocity- 1650fps and 1210 fps.

The longer the range the better the .50 looks but at practical air to air ranges in WW II or Korea the difference in flight times or trajectory between the US .50 and the 20mm Hispano are less than the difference between various 20mm guns used by different nations or less than the difference between the the US .50 and some 12.7-13 mm machine guns.

According to Tony Williams the Germans did some tests and found that the .50 slowed down by about 15 percent at 300 meters and 29 percent at 600 meters. The HS 404 HET shells slowed from 880 m/s to 675 m/s at 300meters (23 percent) and to 500 m/s at 600 meters (43 percent).

For comparison the German 7.92 slowed by 57 percent at 600 meters while the 13 mm slowed by 55 percent. The 20mm mine shell fired by the MG/FFM slowed 60 percent, the 20mm HET (117g) slowed 41 percent and the 30mm mine shell from the MK 108 slowed by 47percent. The 15mm MG 151 was one of the best at 39percent.

The drag on a projectile does vary with the speed of the projectile. As the projectile slows down the drag falls. While doubling the sped will quadruple the drag ( in theory) once the speed falls to the original speed the drag will fall to the original drag.

The difference between percentage of velocity loss and flight time should be noted though. While many of the German rounds seem to show good velocity retention they started out at lower velocities and so had lower drag at the beginning of their flights. Time to 600 meters (compared to 600yds given earlier) being about. 1.16 seconds, 1.22 seconds, 1.43 seconds, 1.10 seconds and 1.66 seconds with the 15 mm MG 151 coming in at 0.816 seconds.

I find much of the info to date misleading. Comparing energy of chemical (explosive) vs mechanical is pointless. The do not have the same affect on a target.

A .50 solid bullet can destroy a water cooled engine in 1 shot. A 20mm thin shelled round may explode on the engine's surface and essentially do nothing.

A .50 cal bullet can punch a .50 hole through Aluminum skin and do nothing, a 20mm thin walled shell can strip whole sheets of skin off a target aircraft when the aircraft is moving at high speed.

Many of the write ups to date are too simplistic.

There are several important categories that must be considered that a round needs to deal with, air vs water cooled engine, self sealing vs non sealed fuel tanks, small vs large aircraft (or lightweight vs robust). Also important are pilot or other armor, and round dispersion (based on distance to target and, gun positions and muzzle velocity/round drag).

In the Pacific 6x.50 cal in the wings was perfectly acceptable to shoot at non sealed fuel tanks and unarmored aircraft. Very few bullets and the plane was in flames
In the Europe 6x.50 cal in the wings also worked enough. And the P-47 damage reports with its 8 fifties were never questioned.

But 4x20mm the FW-190 and other aircraft used were also very effective. May of the Russian aircraft used 1 or 2, 20-23 mm centerline (or near to) in their fighters and found them to work on German aircraft.

Also many of the expert German pilots found the 1x 20mm center line to work well for them.

The .30 cal was universally scoffed at but in the beginning (BOB) 8 per aircraft was standard in England. They would use typically half there load to bring down 1 German but it worked.

Before a serious comparison can be made the conditions must be understood.
Shooting down a Zero vs B-17 are not the same in terms of gun needs. I have seen reports of many pilots taking down 3, 4, 5 even 7 Japanese aircraft in 1 battle. The best the Germans ever did was 2 B17's no matter what armament/airplane they used (in one battle).

When asking the question we must make sure the comparison is valid when the results are in.

Can I ask how many times on how many threads have you made this posting?

Uhm.... that would be exactly four posts of verbatim text.

Yup cause the misused old quoted old data is in on over 20, threads I stopped at 4.