NTSB Factual Report

On July 4, 2010, about 0309 eastern daylight time, N520CF, a Eurocopter AS365N3 helicopter, operated by Air Methods Corp., sustained minor damage when one of its door windows separated from the helicopter in-flight near Dayton, Ohio. The emergency medical services (EMS) transport flight was conducted under 14 Code of Federal Regulations Part 135, and was en route from the Lebanon-Warren County Airport (I68), near Lebanon, Ohio, to an automobile accident site near Huber Heights, Ohio, when the incident occurred. Visual meteorological conditions prevailed in the area. All three occupants, including the pilot and two crewmembers were uninjured. The flight originated from I68 about 0304.

The pilot, according to an operator’s incident report, in part, stated:

At 0304 departed I68 for a scene flight in Huber Heights. Around 0309 local heard a loud bang. Asked flight nurse what happened and if she was ok. Flight nurse stated we lost the window and she was ok. At 0310 local, I called the communication center and said we were aborting and landing at Moraine. ... At 0313 local, I called safe on deck at Moraine.

The pilot dropped a flight manual during cruise flight. The flight manual impacted the right front passenger door jettison handle, which was safety wired. However, the handle's required protective guard was not installed. The jettison handle rotated rearward, broke its safety wire, and disengaged its center door’s upper pin. The center door’s middle and lower pins did not disengage. The window bent outward and separated from its frame. The separated window subsequently impacted the horizontal stabilizer.

According to the helicopter’s trainees hand manual, the helicopter is equipped with a door jettisoning system. The system’s description, in part, included:

JETTISONING SYSTEM

A handle, locked with snapwire [and] protected by a breakable cover, makes it possible, should it be necessary, to jettison the doors. Actuating the mechanism releases either the studs or the hinge pins.

The helicopter’s maintenance manual directs that the crew and passenger doors be removed and checked every 600 hours of flight time or every two years. The manual, in part, lists the following steps to reinstall the doors.

FINAL STEPS

- Install the pneumatic strut and check for correct engagement of the ball-joints.

- Make sure that handle is against stop, then safety jettison lever with snap wire.

- Install the plexiglass protective cover.

- Safety and lock the door and check:

- the locking system is correctly engaged,

- the indicating system operation.

A Heli-Dyne Systems Inc. supplemental type certificate, SH921NE, was the basis on which the helicopter was modified to install a medical interior. Airworthiness documents showed that this major alteration was field approved by the Federal Aviation Administration(FAA) on January 21, 2005.

The helicopter's airworthiness was maintained under a FAA Approved Aircraft Inspection Program (AAIP). The helicopter's most recent AAIP inspection, to include the area of the jettison handle, was completed on June 23, 2010.

The helicopter’s illustrated parts catalog identified the Plexiglas jettison handle guard as COVER, JETTISON RH with part number 365A87-3019-87.

In a letter to the FAA, the operator, in part, stated:

Confusion sets in when [the maintenance manual] uses reference drawings with no "Plexiglas Protective Cover" present. It was believed by the questioned mechanics that the 14 [degree] frame decorative plastic trim was the guard; the decorative plastic trim installed on N520CF could have been removed and installed in the same sequence in place of the “Plexiglas Protective Covers” called out in [the maintenance manual]

Subsequent to the accident, the helicopter manufacturer issued Safety Information Notice 2257-S-52 and 2247-S-00. Notice 2257-S-52 described the incident and, in part, stated:

Considering that the in-flight loss of an aircraft component can seriously affect the safety of the flight and/or of the persons on the ground, EUROCOPTER reminds you that the content of the technical documentation issued by EUROCOPTER must be strictly complied with, especially regarding the installation of aircraft components during removal/installation or maintenance operations. Any failure to comply with any rules specified in the EUROCOPTER technical documentation may adversely affect the aircraft continued airworthiness and flight safety. We also recommend you to read the Safety Information Notice 2247-S-00, which covers specifically serious accidents/incidents caused by failures in the basic application of maintenance instructions.

Notice 2247-S-00 indicated that it was a reminder to mechanics that while performing ‘routine’ applicable maintenance procedures, in particular assembly procedures, “it is important to strictly comply with all applicable maintenance procedures, including the most basic and simple ones, to ensure proper helicopter performance and flight safety.”

NTSB Probable Cause

The unintentional movement of the jettison handle in-flight due to the pilot’s dropping of a manual that impacted the handle and released the door window, which then impacted the horizontal stabilizer. Contributing to the accident was the jettison handle guard not being installed by maintenance personnel.