Bell 206B N8533F

Summary

On 20 April 1998 at about 23:15 local time, a Bell 206B registered N8533F, operated by Papillon Airways, was involved in an accident near Grand Canyon, Arizona, United States. 2 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

20 April 1998 at 23:15

Classification

Accident

Location

Grand Canyon, Arizona, United States

Nearest airport

Grand Canyon Airport (KGCN)

Coordinates

36.0295, -112.0196

Aircraft

Bell 206B

Registration

N8533F

Category

Helicopter

Engines

1

Operator

Papillon Airways

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX98LA139

Nobody was injured.

The malfunction and erratic speed control of the engine's governor, and the flight instructor's delayed remedial action.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The instructor pilot and new company pilot were practicing autorotations, which were terminating in a power-recovery. The flight instructor demonstrated a straight-in autorotation and said that the governor lagged behind but stayed in the green range. The instructor stated that this was typical of this particular helicopter and that he didn't consider the governor lag unusual. The instructor then had the dual student set up for a 180-degree autorotation. During the maneuver he told the student that he was ready to roll on the throttle at 200 feet agl. He stated that at 50 feet and 50 to 55 knots, the pilot flared the helicopter and at 15 feet he had the pilot pull in more collective. At this point, the instructor pulled in some collective himself. He stated that the torque gauge did not move and that it sounded like the engine sound was dragging down and the rpm's in the dual tach decayed. The flight instructor proceeded to take the controls and level the aircraft. The aircraft landed hard and came to a complete stop. After the aircraft was shut down, the tail boom was found still attached but hanging to the ground. A Bell Operations Safety Notice advises that tail boom failure can occur in autorotations where touchdown occurs at 70 percent main rotor speed due to a resonance response of the structure to the main rotor. A postaccident test of the governor function was performed. Power checks were done to duplicate an autorotation and the tests revealed that the engine was slow to accelerate and the governor surged with continual fluctuation of Ng readings.

Quoted verbatim from the NTSB record.