NTSB Factual Report

On March 6, 2003, at 1615 central standard time, a Bell 206L-3 helicopter, N793CA, was substantially damaged following a loss of tail rotor drive during cruise flight near Kingsland, Texas. The helicopter was registered to and operated by Critical Air Medicine, Inc., of San Diego, California. The airline transport pilot, and the two medical crewmembers were not injured. Visual meteorological conditions prevailed, and a company visual flight rules (VFR) flight plan was filed for the 14 Code of Federal Regulations Part 91 positioning flight. The cross-country flight originated from a private helipad in Marble Falls, Texas, at 1604, and was destined for Llano, Texas.

According to the pilot and the two medical crewmembers, they were dispatched to a hospital in Llano to pick up a patient. The pilot walked to the helicopter and started the engine. Prior to boarding the helicopter, one medical crewmember opened the aft cargo door, removed medical equipment, and then closed the door. He then checked the auxiliary power unit (APU) door and boarded the helicopter. During this time the second medical crewmember had boarded the helicopter.

The pilot reported that the takeoff was normal, "except for a notable vertical [vibration] in cruise flight." Ten minutes after takeoff, while in cruise flight at 700 feet agl (8 miles from Llano) a loud bang was heard. The helicopter yawed right and the nose dipped. The pilot lowered the collective and moved the throttle to flight idle. The pilot then began searching for an area to land; however, within the surrounding area there was a river with rocks, a green sloping field with trees and stumps, and an orchard of pecan trees. Subsequently, the helicopter landed hard on soft terrain, amongst the pecan trees, and came to rest upright. The pilot applied the rotor brake to stop the main rotor blades and the pilot and medical crewmembers exited the helicopter. During the landing, the tailboom separated from the helicopter.

According to an FAA inspector, who examined the helicopter and the accident site, a medical blanket, which was in the aft cargo compartment, was found in a tree upstream along the helicopters flight path. Additionally, a section of the tailrotor drive shaft, and other items, which were in the aft cargo compartment were located between the tree that the blanket was in and the accident site.

The helicopter and blanket that was in the tree was examined by the NTSB Investigator-In-Charge. The examination revealed that the aft cargo compartment door and its locking mechanism was not damaged and operated normally. The blanket was torn in multiple areas and contained a dark area, which was consistent with the size of the surface of a tailrotor blade. One tailrotor blade and the blanket were sent to and examined by the Bell Helicopter Engineering Laboratory in Hurst, Texas. The examination revealed that the tailrotor blade was buckled aft and to the inside (as positioned on the helicopter). Imprints of the blanket's weave pattern were observed on the sooty surface of the tailrotor blade. The soot and dirt was also observed on the surface of the blanket. Two areas of the blanket contained an amber colored grease. A comparison of the grease (using FTIR spectroscopy) found on the inboard end of the tailrotor blade and on the blanket, showed it to be of similar composition. Additionally, two fibers, one polyester and one non-mercerized cotton, were found on the tailrotor blade. These fibers are similar to the fibers that comprise the blanket; 82% cotton and 18% polyester.

NTSB Probable Cause

The loss of tail rotor drive as a result of a blanket coming in contract with the tailrotor blades, after the aft cargo door was left unsecured. Contributing factors were the lack of suitable terrain for the forced landing, and the failure of the medical crewmember to properly secure the aft cargo door.