Bell 47G-3B-1 N73998

Summary

On 9 August 1991 at about 12:50 local time, a Bell 47G-3B-1 registered N73998, operated by Churchill, Scott, was involved in an accident near Maple Grove, Minnesota, 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

9 August 1991 at 12:50

Classification

Accident

Location

Maple Grove, Minnesota, United States

Coordinates

45.1305, -93.4503

Aircraft

Bell 47G-3B-1

Registration

N73998

Category

Helicopter

Engines

1

Operator

Churchill, Scott

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Minneapolis → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CHI91DER13

Nobody was injured.

THE PILOT'S FAILURE TO MAINTAIN DIRECTIONAL CONTROL OF THE HELICOPTER DURING THE FORCED LANDING. RELATED FACTORS ARE THE LOSS OF ENGINE POWER, LOSS OF ROTOR RPM, THE ERODED COMPRESSOR BLADES, THE PILOT'S OPERATION WITH KNOWN DEFICIENCIES IN EQUIPMENT AND INADEQUATE AIRCRAFT PREFLIGHT, AND THE BLOCKED SPRAY EQUIPMENT.

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

Read the full NTSB narrative

THE PLT SAID HE HAD COMPLETED AERIAL APPLICATION OF MOSQUITO CTL TREATMENT & WAS RTRNG TO THE LOAD SITE. THE HELICOPTER WAS IN CRUISE FLT AT 300 FT ABV THE GND WHEN THE PLT '...NOTICED IT WAS REQUIRING MORE RIGHT CYCLIC CONTROL TO KEEP THE HELICOPTER LEVEL, ALSO BEGAN TO EXPERIENCE A LOSS IN ALTITUDE.' THE PLT NOTED THE ROTOR RPM HAD DROPPED TO 90%, BUT THERE WERE NO WARNING LIGHTS OR HORNS. THE ENG OUT AUDIO WARNING WAS PLACARDED 'INOPERATIVE' & THE PLT WAS AWARE THE OIL CHIP WARNING LIGHT WAS INOP. THE PLT MADE A FORCED LANDING IN AN ALFALFA FIELD. HE STATED '...DUE TO THE RIGHT CYCLIC INPUT I HAD TO LAND WITH A DRIFT TO THE RIGHT...THE RIGHT SKID GEAR SNAPPED, ROLLING OVER TO THE RIGHT.' AN INV REVEALED THE LEFT HOPPER WAS BLOCKED & STILL CONTAINED AN ESTD 100 TO 300 LBS OF MOSQUITO CONTROL AGENT. THIS LOAD RESULTED IN AN IMBALANCE WHICH WAS COUNTERED BY EXTREME CYCLIC INPUT. EXAM OF THE ENG REVEALED 'SEVERE EROSION' OF THE COMPRESSOR BLADES, AND HORSEPOWER PRODUCTION 'SIGNIFICANTLY BELOW PRODUCTION TEST SPECIFICATIONS.'

Quoted verbatim from the NTSB record.