Saturday, September 17, 2022

Eurocopter MBB-BK 117, N987RH: Incident occurred September 13, 2022 in Rockford, Winnebago County, Illinois

Federal Aviation Administration / Flight Standards District Office; Greater Chicago

Rotorcraft had an unsuccessful mast moment during landing at hospital resulting in a broken left windshield and dented main rotor.  

Air Methods Corporation

Date: 13-SEP-22
Time: 16:19:00Z
Regis#: N987RH
Aircraft Make: EUROCOPTER
Aircraft Model: MBB-BK 117
Event Type: INCIDENT
Highest Injury: UNKNOWN
Flight Crew:  1 Unknown Injuries
Pax: 1 Unknown Injuries
Aircraft Missing: No
Flight Phase: LANDING (LDG)
Operation: 91
Aircraft Operator: AIR METHODS


  1. Allright, sports fans - can anyone explain what "an unsuccessful mast moment" is?
    The BK-117 has a rigid rotor system, so it wasn't mast bumping. It would take a lot of control input to have a blade contact the fuselage, I think. Hard landing?

  2. Mast moment is a particular limitation for the BK-117. Due to the rigid rotor, any time the helicopter is in contact with the ground and cyclic is applied, it produces a bending moment on the mast(mast moment). This can also happen in flight if the helicopter is subject to low G flight. In that case, the blades and rotor immediate change flight path, but due to loss of G loading, the fuselage doesn't immediately follow. This can also produce high MMs. How it came to have damage to the blade and forward fuselage is a bit of a mystery if simply caused by a mast moment exceeds. Probably a hard landing, MM exceedance, and some damage.