# NTSB SEA99LA075: Air Tractor AT-401, N6024M, Jerome, ID, May 27, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: May 27, 1999, 08:30 local (14:30 UTC) - Place: Jerome, ID - Coordinates: 42.729339, -114.429466 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.7293&lon=-114.4295&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report November 30, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 46452 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA99LA075 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46452/pdf - Page: https://openairdocs.org/ntsb/SEA99LA075 ## Probable cause Fuel exhaustion. Carburetor contamination and rough terrain were factors. ## Analysis The pilot departed the airport, with approximately 75 gallons of fuel on board, and flew approximately 19 miles to the spray location. Approximately 45 minutes into the flight, the pilot noticed the fuel quantity gauge indication was decreasing at a higher than normal rate, and he elected to return to the airport. Eight miles from the airport, the aircraft began to lose power and the pilot elected to initiate a forced landing in an open field. During the landing roll, the aircraft struck a lava bed, causing substantial damage to the aircraft. An FAA inspector inspected the aircraft and reported that there was no evidence of fuel in the aircraft's fuel tanks. He also stated there was no evidence of a preexisting fuel leak. Post-accident inspection of the aircraft's carburetor revealed that the mixture control back-suction bleed tube in the carburetor bowl assembly was plugged. According to the certificate holder of the carburetor, a blockage of the mixture control back-suction bleed tube would result in a rich mixture situation. Normal fuel consumption for this aircraft is 32 gallons to 35 gallons per hour. ## Factual narrative On May 27, 1999, about 0830 mountain daylight time, an Air Tractor AT-401, N6024M, registered to West One Bank and operated by Spray Craft, Incorporated, as a 14CFR137 aerial applicator, was substantially damaged during an off-airport landing following an abrupt loss of engine power, eight miles north of Jerome, Idaho. Visual meteorological conditions prevailed and no flight plan was filed. The commercial pilot was not injured. The flight originated from Jerome County Airport, Jerome, Idaho, approximately one hour prior to the accident. During a telephone interview and subsequent written statement, the pilot reported that he departed the airport and proceeded to the spray location, approximately 19 miles northeast of Jerome with approximately 75 gallons of fuel on board. Approximately 45 minutes into the flight, the pilot noticed the fuel quantity gauge indication was decreasing at a higher than normal rate, and he elected to return to the airport. Approximately eight miles from the airport, the aircraft began to lose power and the pilot elected to initiate a forced landing in an open field. During the landing roll, the aircraft struck a lava bed, causing substantial damage to the aircraft's landing gear, engine and firewall. A Federal Aviation Administration inspector from the Boise, Idaho, Flight Standards District Office inspected the aircraft after the accident and reported that there was no evidence of fuel in the aircraft's fuel tanks. He also stated there was no evidence of a preexisting fuel leak. According to the pilot, the aircraft "experienced an abnormally high fuel burn due to either a stuck float in the carburetor or [a] malfunctioning carburetor mixture control." The fuel consumption rate for this aircraft is approximately 32 to 35 gallons per hour under normal conditions. Post-accident inspection of the aircraft's carburetor (serial number 5627175) revealed that the mixture control back-suction bleed tube (refer to Diagram I) in the carburetor bowl assembly was plugged. A back-suction type mixture control leans out the mixture by placing a portion of the venturi suction on the fuel in the float chamber so that it opposes the suction in the venturi on the main discharge nozzles. According to the certificate holder of the carburetor (Precision Airmotive Corporation of Everett, Washington), a blockage of the mixture control back-suction bleed tube would result in a rich mixture situation. Based upon the pilot's statement, fuel consumption during this flight would have been 60-75 gallons per hour. Normal fuel consumption for this aircraft is 32-35 gallons per hour. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, cruise - fuel system,carburetor - contamination (contributing factor) - fluid,fuel - exhaustion (cause) - Forced landing, emergency descent/landing - On ground/water encounter with terrain/water, landing - roll - terrain condition - rough/uneven (contributing factor) ## Aircraft - Registration: [N6024M](https://openairdocs.org/deregistered/N6024M-2011-12-16), registration cancelled 2011-12-16, S/N 401-0949, built 1994 (OpenAirDocs) - Reported make and model: Air Tractor AT-401 - Registry model: [Air Tractor AT-401](https://openairdocs.org/model/air-tractor-at-401) (registry code 0390204) (OpenAirDocs) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 401-0949 - Airframe hours: 1790 - Engines: P&W R-1340 600 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Spray Craft - Registered owner: West One Bank Idaho - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, March 2, 1999, 289 hours before - Departed: U73, JEROME, ID ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; commercial; airplane ratings: multi-engine land, single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: center; flight hours: 3,450 total, 525 in this make and model, 12 in the last 90 days, 12 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 34 °F - Altimeter: 30.00 inHg - Observed at: JER, 8 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19990527005899A](https://openairdocs.org/incident/19990527005899A), May 27, 1999: Airtrc AT401, Jerome, ID, Substantial damage. Acft engine quit shortly after take-off, and the pilot made an emergency landing.(-23)a/c lost power and pilot was forced to alnd in a field. A/c hit an… ## Other investigations on N6024M (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB LAX08CA034](https://openairdocs.org/ntsb/LAX08CA034), Dec 6, 2007: Air Tractor AT-401 (N6024M), Soledad, CA, destroyed. Probable cause: The pilot's failure to maintain an adequate clearance from mountainous terrain while maneuvering during an aerial application mission. Contributing to the accident was the pilot's diverted attention… From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.