Is the motor- generator set a 400Hz unit?
If so check the attachment plug for 6 pins- 4 larger and 2 smaller. If this is what you have it probably is an aircraft standard power plug. The larger and longer pins should be marked as A,B,C,N and the smaller and shorter should be marked as E and F. If this what is on the MG set and matches up with the aircraft ground power recepticale, then you make sure be ok. The e and f pins are actually part of the aircraft external power relay circuit. Depending on the aircraft bieng served they have continuity between them or e pin will have 24vDC with f pin the return.
The reason for the different length of pins is to drop the aircract external power relay when the cord is removed before the A,B,C,N pins lose contact with the receptacle.
I know way too many aircraft workers from my time in the USAF who did what these guys are doing. Unless one of them was stupid or careless enough to put his hand across the phase pins, I never saw any one hurt or any aircraft damaged by those actions. Just make sure the cable and pin head stay in good repair, especally the insulating rubber around the pins.