One reason for arming aircrew in the cold war was to guard the jet rather than fight off 3rd SA.
Arming a Nimrod crew with 9mm pistols was hardly going to scare a Sverdlovsk cruiser or capture an SSN.
I wrote up the case to put secure lockers in to the Nimrod to hold 4xSMG with 4 mags each purely for armed guarding. Fair old weight to be added down the back end. I left shortly after so don't know if it ever happened.