Cessna Citation Mustang (C510)
Maintenance Airframe; Maintenance Powerplant
Maintenance Lead Technician 6; Maintenance Technician 20
Aircraft Equipment Problem Less Severe
Aircraft Aircraft Damaged
Aircraft
Crew reported the right generator fell offline. They started a descent into ZZZ and the engine started vibrating. The crew elected to keep the engine running (per checklist) due to the weather and winds at ZZZ. The gear box was cracked at the starter pad area and the starter broke off of the engine with the shear point failing to break.  The starter generator was subject to a recommended service letter from Cessna SL510-80-02.  It does not require replacement of the generator. It recommends it due to some prematurely failed starter generators. Cessna informed; that although a 'handful' of the Mod level A;B; or C starter generators did not make it to their 1500 hr overhaul limit. Only one had a failure of this magnitude. In my mind if this was a possibility none of these lower mod level starters should be in service. The starter/gen had approx 300 hours left before overhaul and gave no prior signs of failure i.e. bearing 'dust' on the cowling.
Aircraft Maintenance Technician reported starter generator failed inflight.