Ground to Air combat

[Shortround6]

The method was used, it varied according to which army and what year. WW I aircraft were doing 80-120mph near ground level (with few exceptions) and had little or no armor (again with a few exceptions) so they needed about 1/3 to 1/5 the amount of lead of most WW II aircraft. In Vietnam The Helicopters were back to WW I aircraft speeds.

Even early WW II aircraft might be engaged by rifles depending on type, Lysander? Hs 126? assorted other early tactical recon/army co-op planes (read slow). Fighters and fast bombers are much harder to hit (nothing is impossible) but proper AA guns, even rifle caliber MGs with proper sights and mounts were much more effective than scores if not hundreds of rifles.

Some officers encouraged the practice more as a means of keeping up morale than with any real expectation of stopping the air attacks. Seeing plane go down was very encouraging even it was actually hit by a machine gun 500-800yds away

BTW hits to the radiator take a number of minutes to take effect and the ground troops would rarely, if ever, see a plane force land they they had hit in a radiator or oil cooler. It would come down miles away.

 

[The Basket]

The anti aircraft sights on the Type 99 is not that crazy as it was a late 1930s design and so plenty of biplanes in China. Certainly could get a few rounds at a P-26. The pilot was exposed so even a head shot was on the cards.

not every aircraft in a war zone is a 400 mph fighter

 

[Juha2]

When serving in the Finnish Army in mid 70s (shortly after Vietnam War) we were trained to use our assault rifles against a/c and helicopters. A squad would fire together a short burst following orders of the squad leader who would give the nature of the target, its flight direction and the amount of the lead and then order "Fire". We were not suppose to fire at oncoming aircrafts or attack helicopters but at those flying past us.
During the WWII Finnish light AA batteries had also two? twin rifle calibre AA mgs, in 1944 they were used to fire departing Il-2s in order to kill the rear-gunners.