Pilot Debrief

AIR TRACTOR INC AT-502A near Stratford, CA — 2024-01-10

Final reportWPR24LA070
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Date
2024-01-10
Location
Stratford, CA, USA
Airport
Priv
Aircraft
AIR TRACTOR INC AT-502A
Registration
N6126U
Category
Airplane
Highest injury
None
Fatalities
0

Probable cause

A partial loss of engine power due to the malfunction of the engine compressor bleed-off valve.

NTSB narrative

The pilot was repositioning an empty agricultural airplane for fertilizer application. During takeoff, the airplane failed to develop full power. At about 200 feet above ground level (agl) the engine rolled back to near idle. The pilot’s attempt to vary the power lever inputs did not affect engine power output, and he initiated a forced landing into a grove of small pistachio trees and soft dirt. Postaccident examination of the engine and follow-up bench testing of the engine compressor bleed-off valve (BOV) revealed an abnormal amount of air leaking around the piston. Disassembly of the BOV revealed a piston ring set was stuck within the piston groove, consistent with an abnormal air leak and irregular function. Abrasive and adhesive wear was observed on the piston rings and piston groove. The wear was likely due to environmental contaminants or twisting in the BOV’s metal piston ring profile. Based on the condition of the BOV’s rings, the BOV likely did not fully close during the accident flight, which resulted in a partial loss engine power during takeoff.

NTSB coding

Evidence available

  • FDR / data
  • Photos
  • 13 docket documents
View NTSB final reportView NTSB docket

Docket documents13

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