# NTSB CEN23LA088: Beech M35, N9306Y, Tomball, TX, January 22, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: January 22, 2023, 11:27 local (17:27 UTC) - Place: Tomball, TX · Highway 99 - Coordinates: 30.05002, -95.67952 - Nearby events: https://openairdocs.org/map.md?lat=30.0500&lon=-95.6795&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Federal Aviation Administration - Houston FSDO - NTSB case key (mKey): 106620 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN23LA088 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/106620/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=106620 - Page: https://openairdocs.org/ntsb/CEN23LA088 ## Probable cause A loss of engine power during cruise flight for undetermined reasons. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Beech M35, 1 case](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=1151526), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) (defining event); cases with it: [Beech M35, 2 cases](https://openairdocs.org/ntsb-events/000/sequence.md?model=1151526), [All aircraft, 1,703 cases](https://openairdocs.org/ntsb-events/000/sequence.md) ## Analysis The pilot was conducting an aerial survey flight when the engine lost all power during cruise flight. The pilot was unable to restore engine power and he conducted a forced landing to a multi-lane highway. The airplane’s right main landing gear impacted the roof of a semi-trailer before the airplane rolled left wing down and descended into a concrete highway median. A postaccident fire ensued that destroyed most of the fuselage, cabin, and cockpit. A comprehensive examination of the airplane’s fuel system was not possible due to extensive thermal damage sustained during the postaccident fire. About 25 gallons of fuel was reportedly recovered from the fuel system before the wreckage was moved, but the amount of fuel recovered from each fuel tank was not individually documented. Both left and right wingtip fuel tanks exhibited extensive thermal damage and no residual fuel was found within the wingtip tanks. Fuel drained from the fuel selector when it was removed from the wreckage. The airframe fuel filter contained 1/8 to 1/4 cup of fuel. The fuel strainer was largely unobstructed, with only minor debris present. The airplane’s digital engine monitor was destroyed during the postaccident fire. Based on the pilot’s explanation of the fuel load, how the fuel was used during the flight, and a reported fuel consumption rate of 13.5 gallons per hour during cruise flight, there should have been ample fuel remaining to sustain normal engine operation. Examination of the engine did not reveal any preaccident mechanical malfunctions or failures that would have prevented normal operation. Ultimately, the investigation was unable to determine the reason for the loss of engine power. ## Factual narrative The airplane’s digital engine monitor was destroyed during the postaccident fire and, as such, the investigation was unable to review engine parameter data for the flight or determine the tachometer time at the time of the accident. A review of the airplane maintenance logbooks revealed the last annual inspection was completed on July 8, 2022, at 9,672.76 hours total airframe time. According to the logbook documentation, the recently overhauled engine was reinstalled on the airframe during the annual inspection. According to the airplane operator, at the time of the accident, the engine had accumulated about 800 hours since the last major overhaul. A review of the available maintenance records found no history of unresolved airworthiness issues. The airplane had a 110-gallon capacity fuel storage system (103 gallons usable) and consisted of two 25-gallon main fuel tanks, two 10-gallon auxiliary fuel tanks, and two 20-gallon wingtip fuel tanks. The cockpit fuel selector could be positioned to off, left main, right main, or auxiliary. When full, each main fuel tank contained 22 gallons of usable fuel. When full, the two auxiliary fuel tanks had a combined 19 gallons of usable fuel and were interconnected to provide fuel simultaneously to the engine when the fuel selector valve was positioned to auxiliary. The fuel contained in the wingtip tanks was transferred via electric fuel pumps to their respective main tanks and was selectable by an electric switch in the cockpit. All fuel contained in the wingtip fuel tanks was considered usable. On January 22, 2023, about 1127 central standard time, a Beech M35 Bonanza airplane, N9306Y, was substantially damaged when it was involved in an accident near Tomball, Texas. The pilot and the driver of a semi-trailer truck were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 aerial survey flight. According to the airplane operator, the pilot sent a text message at 1008 stating that he was departing West Houston Airport (IWS), Houston, Texas. The pilot reported that the airplane departed with a full fuel load (103 gallons usable) and that the fuel selector was initially positioned to use fuel from the left main tank (22 gallons usable). About 45 minutes into the flight, the pilot switched to the auxiliary fuel tanks (19 gallons usable) and set a timer for 38 minutes. The pilot reported that, based on the airplane’s digital engine monitor, the fuel flow was about 13.5 gallons per hour during cruise flight. Based on a review of ADS-B flight track data and the pilot’s statement, about 1 hour 16 minutes into the flight, the flight entered a left 270° turn to avoid another airplane before flying to the east toward David Wayne Hooks Memorial Airport (DWH), as shown in Figure 1. The pilot reported that the engine lost all power shortly after he completed the left turn and the airplane was heading east. The ADS-B track data showed the airplane about 11 miles west of DWH at 2,000 ftmean sea level before it entered a sustained descent, as depicted in Figure 2. The pilot was unable to restore engine power after he switched from the auxiliary fuel tanks to the right main fuel tank, increased the mixture control to fuel rich, and checked magneto operation. Due to the airplane’s low altitude, the pilot did not continue to troubleshoot the loss of engine power or review the emergency checklist. He declared an emergency with the DWH tower controller and made a forced landing to the eastbound lanes of Highway 99, about 1 mile west of the Telge Road exit. During the forced landing the airplane’s right main landing gear impacted the roof of a semi-trailer before the airplane rolled left wing down and descended into a concrete highway median, as shown in Figure 3. The airplane was immediately engulfed in fire after it came to rest on the highway. After the accident, the pilot unbuckled his restraints and exited the airplane. Figure 1 – Plot of airplane ground track. Figure 2 – Plot of altitude, ground speed, and vertical speed. Figure 3 – Selected frames from the semi-trailer truck camera footage. According to the Federal Aviation Administration (FAA) inspectors who responded to the accident site, the airplane descended onto the eastbound lanes of Highway 99 about 1 mile west of the Telge Road exit. The landing gear and flaps were found extended. The postaccident fire destroyed most of the fuselage, cabin, and cockpit. Both wing roots exhibited various degrees of thermal damage near the main fuel tanks. The filler caps for the two main fuel tanks and the two auxiliary fuel tanks were found properly installed. The FAA inspectors stated that the tow truck operator reportedly drained about 25 gallons of fuel from the fuel tanks before the airplane was moved, but the amount of fuel recovered from each fuel tank was not individually documented. The tow truck operator also added an absorbent granular substance (oil dry) to the fuel tanks to prevent further fuel leaks while the airplane was transported from the accident site. The left wingtip fuel tank exhibited extensive impact and thermal damage, and no residual fuel within the tank. The right wingtip fuel tank exhibited extensive thermal damage, and no residual fuel within the tank. Engine control continuity (throttle, mixture, and propeller) could not be established due to extensive thermal damage associated with the postaccident fire. The fuel lines within the fuselage cabin, cockpit, and engine compartment exhibited various degrees of thermal damage that precluded a comprehensive examination of the fuel system. The cockpit fuel selector valve exhibited thermal damage associated with the postaccident fire. Fuel drained from the fuel selector valve ports while it was separated from the wreckage. The fuel selector valve rotated freely, but the individual tank detents were not discernible. The airframe fuel filter contained 1/8 to 1/4 cup of fuel. The fuel strainer was largelyunobstructed with only minor debris present. The engine remained partially attached to its engine mounts. The forward engine mounts exhibited impact-related damage. The engine crankcase exhibited various degrees of thermal damage but was otherwise intact. The aft portion of the engine and the rear-mounted engine components exhibited extensive thermal damage. There was no evidence of cracks or holes in the crankcase or cylinders. The exterior of the engine did not exhibit any evidence of an oil or fuel leak. The engine oil sump contained ample oil. The oil lines remained intact and attached to their respective components. The oil filter exhibited thermal damage but no evidence of metal contamination. The intake tubes and exhaust were unobstructed. All six engine cylinders remained attached to the engine and exhibited relatively minor thermal damage. Internal engine and valvetrain continuity were confirmed as the crankshaft was rotated through the propeller. Compression and suction were noted on all six cylinders in conjunction with crankshaft rotation. A lighted borescope inspection of each cylinder did not reveal any anomalies with the cylinders, pistons, valves, or valve seats. The throttle and control unit exhibited thermal damage associated with the postaccident fire. The fuel inlet screen was fused inside the housing due to excessive heat from the postaccident fire, which caused it to twist/tear during removal from the housing. The recovered portion of the inlet screen did not exhibit any evidence of contamination. The throttle cable remained attached to the throttle control arm, and the throttle plate rotated freely by moving the throttle arm. The mixture cable remained attached to the mixture arm, but the mixture arm separated from the housing and exhibited impact-related damage. The fuel manifold was found tightly installed to the top of the engine and exhibited thermal damage. Shop air flowed freely through the fuel manifold. The fuel injector lines and nozzles were clear of debris. Both magnetos remained attached to their engine installation points and exhibited thermal damage. The magnetos were removed and rotated by hand which produced spark at each point. The spark plugs exhibited features consistent with normal engine operation. The engine-driven fuel pump exhibited extensive thermal damage associated with the postaccident fire. The drive coupling was found sheared consistent with damage from rotation of the propeller/crankshaft postaccident; there was no evidence of rotational damage that is typically associated with an operational failure of the pump. Additionally, disassembly of the pump revealed thermal damage to the internal components of the pump. The rotating shaft and its associated carbon vanes remained intact but exhibited thermal damage. A dark-black resolidified material was observed within the pump chamber. The propeller remained attached to the crankshaft flange. All three propeller blades exhibited aft bending,twisting toward low pitch, and chordwise scratching. The semi-trailer truck sustained a minor puncture to the roof of the trailer but was otherwise undamaged. ## Aircraft - Registration: [N9306Y](https://openairdocs.org/aircraft/N9306Y), registered now, S/N D-6515, 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-6515 - Year built: 1960 - Airframe hours: 9672.76 - Engines: Continental IO-470-C 250 horsepower reciprocating - Damage: Substantial damage - Fire: On-Ground - Flight: Aerial observation, Part 91 - Operator: TFF, Inc - Registered owner: TFF, Inc - Airworthiness certificate: Standard, Normal - Last inspection: Annual, July 8, 2022 - Departed: IWS, Houston, TX - Destination: T78, Liberty, TX - Flight plan: VFR - Equipment: Electronic flight bag or handheld device, Auto-pilot, ADS-B, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 29; injuries: none; commercial, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review October 6, 2022; seat: left; restraint: 3-point; flight hours: 547 total, 175 in this make and model, 390 as pilot in command, 178 in the last 90 days, 120 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 320° at 10 knots, gusting 16 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 55 °F, dew point 36 °F - Altimeter: 30.02 inHg - Observed at: DWH, 7 nm away - METAR: METAR KDWH 221753Z 32010G16KT 10SM CLR 13/02 A3002 RMK AO2 SLP165 T01330017 10144 20072 50002= ## 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 20230122002989A](https://openairdocs.org/incident/20230122002989A), Jan 22, 2023: Beech M35, Tomball, TX, Destroyed. Aircraft, with one person onboard, while conducting aerial survey flight, experienced engine loss of power at 1500-feet above ground level (AGL). Pilot… ## Docket (8 files) The files NTSB released with the investigation on March 5, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=106620. 15.9 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 4.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18332582&FileExtension=pdf&FileName=01%20-%20NTSB%206120_1%20Form_Redacted-Rel.pdf - Pilot statement (item 2, PDF, 1 page, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18333431&FileExtension=pdf&FileName=02%20-%20Pilot%20Statement_Redacted-Rel.pdf - FAA ADS-B data (item 3, CSV, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18333701&FileExtension=csv&FileName=03%20-%20FAA%20ADS-B%20Data-Rel.csv - Semi-trailer truck video footage (NTSB edited) (item 4, MP4, 2.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18333441&FileExtension=mp4&FileName=04%20-%20Semi-Trailer%20Truck%20Video%20Footage%20(NTSB%20Edited)-Rel.mp4 - Semi-trailer truck video footage (original) (item 5, MP4, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18334226&FileExtension=mp4&FileName=05%20-%20Semi-Trailer%20Truck%20Video%20Footage%20(Original)-Rel.mp4 - Wreckage examination summary (item 6, PDF, 12 pages, 9 photos, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18334019&FileExtension=pdf&FileName=06%20-%20Wreckage%20Examination%20Summary-Rel.pdf - Airplane maintenance logbooks (excerpts) (item 7, PDF, 5 pages, 3.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18333884&FileExtension=pdf&FileName=07%20-%20Airplane%20Maintenance%20Logbooks%20(Excerpts)_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 8, PDF, 1 page, 144 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18334029&FileExtension=pdf&FileName=08%20-%20Wreckage%20Release_Redacted-Rel.pdf 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.