Grumman G-164A N9724

Summary

On 28 May 2011 at about 14:00 local time, a Grumman G-164A registered N9724, operated by Crop Jet Aviation LLC, was involved in an accident near Hazelton, Idaho, 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

28 May 2011 at 14:00

Classification

Accident

Location

Hazelton, Idaho, United States

Nearest airport

Hazelton (U94)

Coordinates

42.5772, -114.1356

Aircraft

Grumman G-164A

Registration

N9724

Category

Airplane

Engines

1

Operator

Crop Jet Aviation LLC

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Hazelton → Hazleton

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR11LA238

Nobody was injured.

A total loss of engine power during low-level maneuvering due to an excessively worn carburetor.

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

Read the full NTSB narrative

The pilot was completing an aerial application pass over a field when the engine began to lose power. He initiated a climb, heard a bang, and observed a white puff of smoke issuing from the top of the engine. The engine subsequently lost all power, and the airplane sustained substantial damage during a forced landing into a pasture. Postaccident examination of the engine revealed that it did not exhibit catastrophic internal damage or any preimpact anomalies that would have precluded normal operation. The carburetor was undamaged during the accident and was subsequently installed on an exemplar engine for testing. During the tests, the engine sputtered, backfired, hesitated, and produced puffs of white smoke from the exhaust ports when the throttle was advanced from idle to power. The sputtering stopped when the throttle was advanced slowly. Examination and disassembly of the carburetor revealed excessive wear, particularly to the accelerator pump assembly. The accelerator pump provides increased fuel flow to the engine during rapid throttle advance, and an ineffective pump would cause engine hesitation and stumbling during acceleration. The symptoms reported by the pilot during what would have been rapid engine acceleration after completing a pass was consistent with a worn accelerator pump, and matched the engine characteristics observed during the carburetor test. The carburetor had been installed on another engine since its most recent maintenance event and its total time since overhaul could not be determined. The engine examination also revealed that five teeth from an intermediate gear within the supercharger drivetrain were fractured, with loading opposite of the direction of rotation. Metallurgical tests found that the teeth failed in overload. Given the rotational speeds of the supercharger system, the gear failure was most likely caused by the sudden engine stoppage after the propeller made contact with the ground.

Quoted verbatim from the NTSB record.