# NTSB FTW97LA147: Beech M35, N223C, Iowa Park, TX, March 30, 1997 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 30, 1997, 15:30 local (21:30 UTC) - Place: Iowa Park, TX - Coordinates: 33.950439, -98.680351 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.9504&lon=-98.6804&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report August 25, 1997 - Report: Approved by Office Director - NTSB case key (mKey): 20188 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW97LA147 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/20188/pdf - Page: https://openairdocs.org/ntsb/FTW97LA147 ## Probable cause The pilot's refueling of the airplane with automotive grade fuel which resulted in engine failure due to detonation. A factor was the lack of suitable terrain for the forced landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, takeoff - initial climb - fluid,fuel grade - improper (cause) - refueling - improper, pilot in command (cause) - misc,engine pre-ignition and/or detonation - engine assembly,piston - failure,total - Forced landing, emergency descent/landing - On ground/water encounter with terrain/water, landing - roll - terrain condition - ditch - terrain condition - none suitable (contributing factor) ## Analysis The airplane was on its initial takeoff climb when the engine lost power. The pilot performed a forced landing in a field, and during the landing roll, the airplane impacted a ditch. An engine teardown revealed that the number 1, 2, 5, and 6 pistons were cracked, and the number 3 and 4 pistons had separated from their piston pins and were lodged in the top of their respective cylinders. An analysis of the fuel found in the airplane established that it was automotive gasoline (octane grade 87 to 92). As listed in the limitations section of the Pilot's Operating Handbook, the minimum octane grade of fuel approved for use in the airplane was 100. The use of low-grade fuel can lead to detonation, which is defined in FAA Advisory Circular 61-23B as a sudden explosion or shock to a small area of the piston top. ## Factual narrative On March 30, 1997, at 1530 central standard time, a Beech M35 airplane, N223C, registered to and operated by a private owner, was substantially damaged during a forced landing following a loss of engine power near Iowa Park, Texas. The private pilot and his passenger were not injured. Visual meteorological conditions prevailed for the Title 14 CFR Part 91 personal flight. A flight plan was not filed for the local flight which was originating at the time of the accident. During a telephone interview conducted by the NTSB investigator-in-charge and on the NTSB Pilot/Operator Aircraft Accident Report, the pilot stated that the airplane was on its initial takeoff climb from the Wichita Valley Airport when the engine seized and oil splashed onto the windshield. He made a forced landing in a wheat field close to the airport. During the landing roll, the airplane impacted an "unseen drainage ditch." Examination of the airplane by an FAA inspector revealed that both wing spars were bent and the fuselage was twisted. An engine teardown was performed under the supervision of an NTSB investigator at Air Salvage of Dallas in Lancaster, Texas, on April 3, 1997. During removal of the engine from the airframe, a portion of the number 4 connecting rod with its respective piston pin attached was found in the forward area of the cowling. Three holes were noted in the crankcase. During disassembly, it was found that the numbers 3 and 4 pistons had separated from their piston pins, and these pistons were lodged in the top of their respective cylinders. The number 1, 2, 5, and 6 pistons were cracked. Numerous metal pieces were found in the oil sump and throughout the whole engine. A fuel sample was taken; the fuel was yellow in color and had a strong gasoline odor. A review of the Limitations Section of the Beechcraft Bonanza K35 and M35 Pilot's Operating Handbook revealed that the minimum octane grade of fuel approved for use in the airplane was 100. On the Pilot/Operator Report, the pilot indicated the airplane had a mixture of 100 Low Lead and automotive fuel on board at the time of the accident. A laboratory analysis of the fuel sample performed by the Armstrong Forensic Laboratory, Inc., of Arlington, Texas, established the fuel to be automotive gasoline (octane grade 87 to 92). Regarding the octane grades of fuel, FAA Advisory Circular (AC) 61-23B, Pilot's Handbook of Aeronautical Knowledge, states the following: The proper fuel for an engine will burn smoothly from the spark plug outward, exerting a smooth pressure downward on the piston. Using a low-grade fuel or to lean a mixture can cause detonation. Detonation or knock is a sudden explosion or shock to a small area of the piston top, similar to striking it with a hammer. ## Aircraft - Registration: [N223C](https://openairdocs.org/deregistered/N223C-2011-01-03), registration cancelled 2011-01-03, S/N D-6287, built 1960 (OpenAirDocs) - Reported make and model: Beech M35 - Registry model: [Beech M35](https://openairdocs.org/model/beech-m35) (registry code 1151526) (OpenAirDocs) - Registry engine: [Continental I0-470 series](https://openairdocs.org/engine/continental-i0-470-series) (registry code 17027, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: D-6287 - Airframe hours: 5588 - Engines: Continental IO-470-C 250 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Wade A. Mathews - Airworthiness certificate: Standard, Utility - Last inspection: Annual, May 4, 1996, 23 hours before - Departed: F14 - Airport: F14, Wichita Valley ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 51; private; airplane ratings: single-engine land; medical: class 3, unknown; seat: left; flight hours: 3,500 total, 4 in this make and model, 40 in the last 90 days, 15 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 315° at 15 knots - Visibility: 10 statute miles - Temperature: 70 °F ## 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 19970330003959A](https://openairdocs.org/incident/19970330003959A), Mar 30, 1997: Beech M35, Wichita Falls, TX, Substantial damage. Engine siezed on takeoff. Oil on windshield. Crash landed. Had thrown a rod. Piston broke. Detonation due auto fuel (-23) aircraft took off from F14 and 20… 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.