Incident Overview
On January 29, 2016, at 1303 eastern standard time, a Eurocopter France EC130 B4, registration N133HN, operated by Air Methods Corporation, sustained substantial damage when the left rear entry door departed the airframe during flight near Shoals, West Virginia. The commercial pilot and two medical flight crewmembers were not injured. Visual meteorological conditions prevailed. The helicopter was operating on a company visual flight rules flight plan from Cabell Huntington Hospital Heliport (WV27), Huntington, West Virginia, to a helipad at Three Rivers Hospital, Louisa, Kentucky, under 14 CFR Part 135.
Flight Crew Observations
According to the pilot, about five minutes after takeoff, while in cruise flight at an airspeed of about 125 knots, he felt and heard an increase of wind in the cockpit. He scanned both front windows to check if they were ajar and, as he faced forward, heard and felt a rush of air, initially thinking the left rear sliding door had opened. As the pilot turned to look, he heard a "whoosh" and saw what he thought was a clipboard depart the helicopter and angle away from the tail.
The pilot slowed the helicopter and instructed the specialty nurse to try to close the door. She appeared to have difficulty, so the pilot suggested the door may have "locked back" and advised using the lock release to slide the door forward. After a few seconds, the specialty nurse announced that the door was missing, at which point the pilot realized the object he saw was the door.
With no abnormal flight characteristics, the pilot diverted to nearby Tri-State Airport (HTS), Huntington, West Virginia, and landed uneventfully. After shutdown, a visual inspection revealed damage to the left transmission hatch, one rotor blade, and the plastic sliding door guide on the left side baggage door.
The flight nurse reported that she observed the specialty nurse slide and latch the door before takeoff. During the flight, when she heard a loud wind noise, she looked left and saw the door was open. She then heard the specialty nurse announce to the pilot that the door was gone.
Post-Incident Examination
An examination by a Federal Aviation Administration Inspector revealed that one of the rotor blades was punctured from the leading edge to the trailing edge. The lower door track exhibited signs of "forced removal" of the attaching hardware. Both upper and lower track lips contained radial damage and missing paint. The middle door track showed similar damage. The plastic door stop bracket exhibited impact damage, and a portion of the stop was missing.
Examination of the recovered door showed signs of damage along the frame. The door stop was missing from the door, and the upper rail arm was loose. The attachment fitting on the arm had chipped paint.
The detached left rear passenger door was recovered and examined by the airframe manufacturer under NTSB supervision. The door's handle and latching mechanism looked and functioned normally, displayed normal wear, and showed no deformation around the brackets that held the latches or latch pins.
Performance Limitations
According to the helicopter's flight manual, the power-on never-exceed speed with all doors closed was 155 knots. With the left rear sliding door open and free to move, the never-exceed speed decreased to 70 knots. The never-exceed speed was 80 knots with the door locked in the open position and 110 knots with the door removed.