Cobb EXEC 90 N7656T

Summary

On 22 May 1992 at about 18:30 local time, a Cobb EXEC 90 registered N7656T, operated by Cobb International, Inc., was involved in an accident near Glendale, 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

22 May 1992 at 18:30

Classification

Accident

Location

Glendale, Arizona, United States

Nearest airport

Glendale Muni Airport (GEU)

Coordinates

33.5297, -112.3106

Aircraft

Cobb EXEC 90

Registration

N7656T

Category

Helicopter

Engines

1

Operator

Cobb International, Inc.

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX92LA214

Nobody was injured.

THE IMPROPER CARBURETOR IDLE ADJUSTMENT BY COMPANY MAINTENANCE PERSONNEL. CONTRIBUTING TO THIS ACCIDENT WAS THE CFI'S INABILITY TO ATTAIN ADEQUATE RPM AND THE SOFT DIRT.

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

Read the full NTSB narrative

THE FLIGHT DEPARTED THE AIRPORT ON A LOCAL INSTRUCTIONAL FLIGHT. WHEN THE FLIGHT RETURNED TO THE AIRPORT THE CFI INSTRUCTED THE NONCERTIFICATED STUDENT PILOT TO EXECUTE A SIMULATED ENGINE OUT AUTOROTATION. THE STUDENT PILOT ENTERED THE AUTOROTATION AT A LOW MAIN ROTOR RPM, BUT DURING THE DESCENT THE RPM INCREASED TO THE LOW SIDE OF ITS NORMAL OPERATING RANGE. THE CFI ATTEMPTED TO TERMINATE THE AUTOROTATION AT 200 FEET AGL BECAUSE OF THE MARGINAL LOW ROTOR RPM, BUT WHEN HE APPLIED RAPID FULL THROTTLE THE ENGINE FALTERED AND THEN FAILED. THE CFI EXECUTED AN EMERGENCY AUTOROATIVE LANDING. ON TOUCHDOWN THE HELICOPTER BOUNCED, THE SKIDS DUG INTO THE SOFT DIRT ON THE SECOND TOUCHDOWN AND THE HELICOPTER CAME TO AN ABRUPT STOP AND ROLLED OVER. THE POST ACCIDENT ENGINE EXAMINATION DISCLOSED THAT THE ENGINE OPERATED NORMALLY THROUGHOUT ITS NORMAL OPERATIONAL PARAMETERS BUT WHEN THE THROTTLE WAS RAPIDLY APPLIED AFTER A PROLONGED IDLE THE ENGINE FALTERED. THE IDLE RPM WAS MARGINAL AND THE CARBURETOR HAD RECENTLY BEEN REPLACED.

Quoted verbatim from the NTSB record.