# NTSB CEN25LA325: Helio H-391B, N4431U, Monroe, MI, August 18, 2025 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 4 · Limited · Final report - Date: August 18, 2025, 13:30 local (17:30 UTC) - Place: Monroe, MI - Coordinates: 41.939889, -83.434667 - Nearby events: https://openairdocs.org/map.md?lat=41.9399&lon=-83.4347&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Loss of control on ground](https://openairdocs.org/ntsb-events/230) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report January 9, 2026 - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Central Region - Parties: FAA - NTSB case key (mKey): 200814 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN25LA325 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/200814/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=200814 - Page: https://openairdocs.org/ntsb/CEN25LA325 ## Probable cause The pilot’s failure to maintain directional control during the landing roll with a crosswind. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Helio H-391B, 2 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=4300106), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters: directional control](https://openairdocs.org/ntsb-findings/01062020): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Helio H-391B, 2 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=4300106), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) - [Wind: crosswind](https://openairdocs.org/ntsb-findings/03034040): Environmental issues › Conditions/weather/phenomena · Effect on operation (probable cause); cases with it: [Helio H-391B, 1 case](https://openairdocs.org/ntsb-findings/03034040/cases.md?model=4300106), [All aircraft, 1,008 cases](https://openairdocs.org/ntsb-findings/03034040/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-landing roll: Other weather encounter](https://openairdocs.org/ntsb-events/400); cases with it: [Helio H-391B, 1 case](https://openairdocs.org/ntsb-events/400/sequence.md?model=4300106), [All aircraft, 1,127 cases](https://openairdocs.org/ntsb-events/400/sequence.md) - [Landing-flare/touchdown: Loss of control on ground](https://openairdocs.org/ntsb-events/230) (defining event); cases with it: [Helio H-391B, 2 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=4300106), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-landing roll: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Helio H-391B, 1 case](https://openairdocs.org/ntsb-events/300/sequence.md?model=4300106), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) ## Analysis The pilot reported that while landing his tailwheel airplane in a crosswind, the airplane bounced upon touchdown. The right wing lifted, the airplane drifted down the runway on the left wheel, and the airplane exited the runway into the grass. The left wheel dug into the grass and the airplane pivoted. During the accident sequence, the left landing gear separated from the fuselage, and the left wing struck the ground. The left wing was substantially damaged. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. At the time of the accident, the pilot was landing the airplane on runway 03 with wind from 100° at 10 knots gusting 15 knots. ## Aircraft - Registration: [N4431U](https://openairdocs.org/aircraft/N4431U), registered now, S/N 091 (OpenAirDocs) - Reported make and model: HELIO H-391B - Registry model: [Helio H-391B](https://openairdocs.org/model/helio-h-391b) (registry code 4300106) (OpenAirDocs) - Category: Airplane - Serial number: 091 - Year built: 1958 - Airframe hours: 2385 - Engines: Lycoming GO435C2B2-6 260 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 8, 2025, 14 hours before - Departed: 3NP, Napolean, MI - Destination: TTF, Monroe, MI - Airport: TTF, Custer Airport, runway 03, 4,997 × 100 ft, concrete - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; injuries: none; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review September 13, 2024; seat: left; restraint: 3-point; flight hours: 329 total, 12 in this make and model, 12 in the last 90 days, 12 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 100° at 10 knots, gusting 15 - Visibility: 10 statute miles - Lowest ceiling: 3,200 ft broken - Temperature: 75 °F, dew point 63 °F - Altimeter: 30.18 inHg - Observed at: KTTF - METAR: KTTF 181735Z AUTO 10010G15KT 070V130 10SM BKN032 OVC038 24/17 A3018 ## 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 20250818013389A](https://openairdocs.org/incident/20250818013389A), Aug 18, 2025: Helio H-391B, Monroe, MI, Substantial damage. Pilot lost control attempting to land with a crosswind. The aircraft turned 90 degrees right into the wind and skidded on the left main wheel. Upon exiting the… ## Other investigations on N4431U (2) 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 SEA92LA191](https://openairdocs.org/ntsb/SEA92LA191), Aug 26, 1992: Helio H-391B (N4431U), Edmonds, WA, destroyed. Probable cause: THE PARTIAL LOSS OF ENGINE POWER WHEN AN EXHAUST VALVE SEIZED IN THE OPEN POSITION AND THE WATER WHERE THE PILOT WAS FORCED TO LAND, WHICH RESULTED IN AN ACFT NOSE OVER ON TOUCHDOWN. - [NTSB SEA84LA026](https://openairdocs.org/ntsb/SEA84LA026), Nov 19, 1983: Helio H-391B (N4431U), Hood River, OR, substantial damage ## Docket (2 files) The files NTSB released with the investigation on January 9, 2026, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=200814. 3.3 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19542052&FileExtension=pdf&FileName=New%20Form%206120%20copy_Redacted-Rel.pdf - Photos (item 2, PDF, 4 pages, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19572044&FileExtension=pdf&FileName=photos-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.