Accidental discharge of weapons while onboard an aircraft can and has happened in peace time and combat situations. In all cases it was the result of the weapon not being cleared properly. We are not aware of any such incidents that resulted in injury to crew members or major aircraft damage.
After RTB from a mission we had just taxied in and were about to unload the team into the step van.. As we were unloading the team one of them fired an M-79 round between Max Schiffman & myself & it lodged in the hoist control panel. Lucky that it didn't go far enough to arm, so it didn't explode.
When the M-79 went off, I turned around & the guy was leaning on the door M-60 that was pointed down at the floor & there was a lot aluminum honeycomb material flying around in the cabin. I thought that I had somehow unloaded the M-60 and left a round in the chamber & it went off.
After the team was loaded in the step van, one of the ground crew said, hey the bullet is in the side of the chopper. I went back in & he showed it to me. I said that's not a bullet it's an M-79 grenade you need to get away from it & call EOD, which they did.
(NOT AN INADVERTENT DISCHARGE BUT WORTH TELLING)
We were flying one of the "cats & dogs" Base Flight missions going up to Lincoln, NB to bring back the WAF Bowling Team, when this event occurred. Steve Masur was flying as AC/IP with me as CP with Ron Earheart & Jim Foster downstairs. Suddenly there was a loud bang from below, and Steve immediately went into full autorotation heading for a farm field straight ahead. As a farm boy, I knew what it was, and after checking the gages, over road the throttle grip and brought the engine back in while yelling at Steve, it was a gun not the engine. Back in control, Steve landed in the field, and gave me the controls, climbed down and reamed out both of the Lts below. When he got back in, I asked him who fired the gun and he told me it was Ron. But fumed a bit telling me, "But that dammed 2/Lt had the balls to tell me, '"Hey! If you think you were shocked! You oughta seen that cow run he shot at!"
And there is another time I remember very well. When we were climbing out after our first NVN pickup in 65, I was flying the High Bird and Walt Turk was clearing his weapon by taking the clip out and firing off the chambered round, like the guys in back did. As he put it back in the gun well and at the same second his gun butt hit the bottom of the well, a shot went off. Already on one helova adrenalin high, I swear we both looked up for a hole in top figuring we had just shot ourselves down. Needless to say we hadn't. The guys that came over with me from Kirtland got M-16 training, but the PJ's hadn't. The first time they had fired one was when we went across the line in to Laos that day. So he didn't pull the clip out first and had to fire it off twice. Funny now, but not then!
For those of us who flew the cabin of the 53 back then, you remember what a bear it could sometimes be to have to unsecure the right gun when prepping for a rope ladder or hoist, in combat, where timing was critical. For those who haven't had the honor, or us with cobwebs cluttering brain matter, you had to get the right gun's big safety pip-pin removed to free it to swing inside for door work. When the pin was out, we were supposed to confirm the gun power at the gun and the cockpit master arm switches were "off" before swinging the gun inside. Supposed to. We would then stow it in its mount aft of the door until after the door work. Removing the pip-pin that secured the main crossbar to the door's forward support tube "U" mount also disabled the firing circuitry because when properly installed, the pip-pin would go through the support tube and engage a microswitch mounted below the cross tube. Well, when/if it was a hot infil/exfil, whatever enabled getting the gun back on line the quickest, became standard procedure, unless (in rescue) 41 ARRW was in from Hawaii for check rides. Locally, in the 21st it was normal procedure, stan/eval or not.
The problem was that although you could muscle out the pin (I used my K-bar as a prying device - I know, I know...), you had to be able to re-secure the pin (if it didn't break apart) in the mount you just cursed into submission. That was the other half of the problem. If doing a hot infil or recovery by the door (rope ladder, hoist or nose wheel landing, you naturally busted your butt to get the gun back on line as soon as possible. As often as not in my experience, no matter how well the supporting cross tube sway brace was adjusted for fit, it was an, on the ground adjustment by our trusty gun plumbers. In flight, all bets were then off.
So, trustier FMs came up with a work around, of course. I'm pretty sure now that it was in the Dustys or we would have had the PJs pushing us aside to try and prove they could pull it out easier than the FM. Anywho, as I recall, this particular flight happened to be a training mission with, a young FM getting mission training on gun operations with an Instructor FM behind him. As fate would have it, the IFM (was getting a checkride that same flight by wing stan/eval FM.
Now to our clever(?) work-around. Our old gunners belts had a leather swatch buffering the metal from us (or over the survival vest as I wore mine). It was about 4" square and we would cut off a corner of it, fold it over and use it as a wedge to pry between the bottom of the "U"mount and the microswitch. That way, we had a way to get around using the pip-pin to lock in and keep the gun power microswitch engaged at all times, as long as the leather stayed in. Some guys used their Zippo.
We then had a gun that didn't require a pip-pin to secure it or enable power to the mini-gun. Pip-pin problem solved. Only issue then was keeping the gun tube 'secured' in the forward mount. Duh! Screwdrivers! So, we all carried, close at hand a 6" screw stick that we would put into the aligned holes that the pip-pin would otherwise be mounted into. Gun power assured by the leather piece, gun 'secured' in the door with a screw stick, good to go. Standard MO was to get to a hover, pull the screw driver out, turn off gun power at the gun, swing it inside (aft...), do your hoist/ladder, swing the gun back to the door, put the screwdriver back in, power switch on, "Going hot" brrrpppppp...
Well, on that training mission, as with any training mission, evasive maneuvering was also required..."Gunfire 2 o'clock, break left," etc. As well as wheel chocks being pounded on the floor to simulate incoming fire and for added adrenalin push. As I recall, it was during such maneuvering with the new FM hot at the gun returning fire, breaking left, that the screw driver (no guarantee it was the expected 6") vibrated out, FM was pulled back into cabin, pivoting aft at gun mount, holding on to his grips, which happened to include triggers, power enabled.
Maybe someone had this scenario in mind when they shielded the pilots in full height armor seats, thinking possible mutiny from the back. Whatever the reason, the 6 or seven rounds that I'm told made it through the forward cabin to the cockpit missed any pink parts. No blood, other that what may have been drawn at de-brief. I wasn't on-board but was at the hootch bar that night. No more personal screw drivers and more emphasis on adjusting sway bars in consideration of in-flight torqueing of the crossbar. Hey, nobody got hurt...with 7.62 anyway.