McDonnell Douglas MD-600N N630N

Summary

On 21 November 1996 at about 16:01 local time, a McDonnell Douglas MD-600N registered N630N was involved in an accident near Flagstaff, Arizona, United States. One person was 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

21 November 1996 at 16:01

Classification

Accident

Location

Flagstaff, Arizona, United States

Nearest airport

Flagstaff Pulliam

Coordinates

35.2297, -111.7193

Aircraft

McDonnell Douglas MD-600N

Registration

N630N

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Unknown

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX97LA061

Nobody was injured.

The pilot's inattention to the altitude and inadvertent late entry into an autorotation maneuver below the established minimum test altitude with a helicopter operating at maximum gross weight in a high density altitude environment that led to a subsequent hard landing. Contributing were the lack of positive communications between ground test personnel and the pilot regarding the low altitude, and the lack of accurate in-flight and ground altimeter equipment.

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

Read the full NTSB narrative

The helicopter was being flight tested to validate certification criteria for height velocity curves at a maximum gross weight and zero airspeed at a high density altitude airport. On the fourth test profile, the pilot allowed the aircraft to descend below the target altitude of 800 feet agl by almost 70 feet. The ground test engineers observed the drift down and didn't advise the pilot because they assumed he had already begun the autorotation after he had made the 3 second call, and also they believed their ground equipment was inaccurate. The pilot delayed the autorotation for about 8 to 12 seconds and then lowered the collective. The aircraft landed hard exceeding the maximum load for the landing gear system. The horizontal speed at touchdown was 52 knots instead of the target speed of 65 knots. The test helicopter was equipped with standard analog altimeters with pointers that have a lag time instead of the more accurate real time digital altimeters.

Quoted verbatim from the NTSB record.