# NTSB ANC94LA107: Helio H-700, N4059H, Tok, AK, August 13, 1994 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 12, 1994, 17:00 local (Aug 13, 1994, 01:00 UTC) - Place: Tok, AK - Coordinates: 63.180698, -143.09996 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=63.1807&lon=-143.1000&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed, report May 9, 1995 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - NTSB case key (mKey): 2540 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC94LA107 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/2540/pdf - Page: https://openairdocs.org/ntsb/ANC94LA107 ## Probable cause THE PARTIAL FAILURE OF THE AIRPLANE'S NORMAL BRAKE SYSTEM. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - On ground/water encounter with terrain/water, landing - roll - landing gear,normal brake system - failure,partial (cause) - terrain condition - ditch - ground loop/swerve - intentional, pilot in command ## Analysis AFTER LANDING ON THE GRAVEL BAR ON THE ROBERTSON RIVER, THE LEFT WHEEL'S BRAKE 'WENT SOFT.' THE PILOT ALLOWED THE AIRPLANE TO CONTINUE THE LANDING ROLL AND PRIOR TO STRIKING THE DITCH, HE INTENTIONALLY GROUND LOOPED THE AIRPLANE. DURING THE GROUND LOOP THE TAIL WHEEL STRUCK THE DITCH AND THE FUSELAGE BUCKLED. EXAMINATION OF THE AIRPLANE SHOWED THAT THE LEFT BRAKE'S TORQUE PLATE HAD SHEARED AND BROKEN THE BRAKE LINE. ## Factual narrative On August 12, 1994, at 1700 Alaska daylight time, a wheel equipped Helio-Courier H-700 airplane, N4059H, registered to Charlie Warbelow and operated by 40 Mile Air, LTD, of Tok, Alaska, experienced a brake problem during landing on an airstrip located 40 miles southwest of Tok on the east fork of the Robertson River. The Air Taxi flight, operating under 14 CFR Part 135, departed Tok and the destination was the accident site. A company flight plan was in effect and visual meteorological conditions prevailed. The pilot and the three passengers were not injured. The airplane was substantially damaged. According to the pilot, as he attempted to stop the airplane through the use of his brakes, the left brake went soft. He allowed the airplane to continue rolling and just prior to running into a ditch he intentionally ground looped the airplane. The tailwheel hit the ditch and the fuselage buckled behind the aft baggage compartment. The pilot stated the torque plate had sheared from the brake calipers and the brake line had broken. The passengers were employees of the American Copper and Nickel Prospect. The operator did not submit their names on the NTSB Form 6120.1/2 at the time of the accident. ## Aircraft - Registration: [N4059H](https://openairdocs.org/deregistered/N4059H-2000-01-10), registration cancelled 2000-01-10, S/N H-9 (OpenAirDocs) - Reported make and model: Helio H-700 - Registry model: [Helio H-700](https://openairdocs.org/model/helio-h-700) (registry code 4300400) (OpenAirDocs) - Category: Airplane - Serial number: 09 - Airframe hours: 1160 - Engines: LYCOMING TIO-540 350 horsepower reciprocating - Damage: Substantial damage - Flight: Part 135 - Operator: 40 Mile Air, Ltd - Registered owner: Charles Warbelow - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, July 20, 1994, 30 hours before - Departed: TKJ, AK - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 41; airline transport; airplane ratings: single-engine land, multi-engine land, single-engine sea; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 12,000 total, 2,000 in this make and model, 11,800 as pilot in command, 300 in the last 90 days, 40 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 30 statute miles - Lowest ceiling: 4,000 ft broken - Temperature: 61 °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 19940812021389A](https://openairdocs.org/incident/19940812021389A), Aug 12, 1994: Helio H700, Tok, AK, Substantial damage. Left brake failed on landing roll. Ground looped avoiding overrun. Bent fuselage. Torque plate and calipers broke. ## Other investigations on N4059H (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 ANC95LA039](https://openairdocs.org/ntsb/ANC95LA039), Mar 26, 1995: Helio H700 (N4059H), Deadhorse, AK, substantial damage. Probable cause: AN OVERLOAD FAILURE OF THE RIGHT MAIN GEAR RETENTION/LIMIT CABLE BRACKET BOLTS AND INSTALLATION OF NON-STANDARD BOLT HARDWARE BY OTHER MAINTENANCE PERSONNEL. THE PILOT'S FAILURE TO ABORT THE TAKEOFF… 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.