# NTSB LAX98LA304: Boeing 369E, N685F, Mesa, AZ, September 24, 1998 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 24, 1998, 15:40 local (22:40 UTC) - Place: Mesa, AZ - Coordinates: 33.429725, -111.710456 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.4297&lon=-111.7105&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report February 22, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 44077 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX98LA304 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/44077/pdf - Page: https://openairdocs.org/ntsb/LAX98LA304 ## Probable cause A hard landing caused by the pilot's improper flare during a simulated autorotatative landing. A factor in the accident was the soft wet sod landing area. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Hard landing, landing - flare/touchdown - terrain condition - soft (contributing factor) - misc rotorcraft,main rotor/tail boom contact - emergency procedure - simulated, pilot in command(cfi) - autorotation - performed, pilot in command(cfi) - flare - improper, pilot in command(cfi) (cause) ## Analysis The instructor pilot and his student were practicing autorotations to a turf area, which was wet and soft. The instructor pilot demonstrated a 180-degree autorotation, which he said appeared to finish with a normal deceleration flare and touchdown. After touchdown the instructor pilot stated he heard a loud rattling sound coming from the tailboom. The aircraft was examined and found that during the autorotation, the tailrotor blades had hit the ground causing damage to the tail rotor blades and tailboom, and it had severed the tail rotor driveshaft. Ground witnesses said the helicopter hit the ground harder than normal. ## Factual narrative On September 24, 1998, at 1540 hours mountain standard time, a Boeing 369E helicopter, N685F, collided with the ground during a practice 180-degree autorotation at the Falcon Field Airport, Mesa, Arizona. The aircraft, operated by Boeing Helicopters, sustained substantial damage. The instructor pilot and dual student were not injured. The local area instructional flight conducted under 14 CFR Part 91 departed the Boeing Helicopter ramp to perform the recurrency training at 1500. Visual meteorological conditions prevailed at the time of the accident. The instructor pilot stated that he and the student flew for about 1 hour demonstrating various landing procedures to include about 15 straight-in autorotations to Falcon Field's north turf area, which was damp and soft. The instructor pilot demonstrated a 180-degree autorotation, which he stated "appeared to finish with a normal deceleration flare and touchdown." He stated that right after the touchdown, a loud rattling sound was heard coming from the tailboom. The aircraft then had a short slide to a stop with a slight right curve. Ground personnel indicated to the flight crew that the aircraft should not lift off because they could see the tail rotor was slowing to a stop. The instructor pilot said he opened his door and saw the tail rotor was not turning, and he proceeded to shut the aircraft down. Prior to moving the aircraft, it was discovered that the aircraft's tail rotor blades had hit the ground causing damage to the tail rotor blades, tailboom, and severing the tail rotor drive shaft. Witnesses stated they thought the aircraft hit harder than usual and bounced slightly with a short slide. ## Aircraft - Registration: N685F (not matched to a registry record) - Reported make and model: Boeing 369E - Category: Helicopter - Serial number: 0512E - Airframe hours: 3245 - Engines: Allison 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: Boeing Helicopters - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 23, 1998, 74 hours before - Departed: FFZ, FALCON FIELD, AZ - Airport: FFZ, Falcon Field ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; flight instructor, commercial; medical: class 2, valid medical--w/ waivers/lim; seat: right; flight hours: 2,082 total, 167 in this make and model, 2,049 as pilot in command, 97 in the last 90 days, 37 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 290° at 5 knots - Visibility: 50 statute miles - Lowest ceiling: none - Temperature: 91 °F - Altimeter: 29.00 inHg - Observed at: FFZ ## 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 19980924026699A](https://openairdocs.org/incident/19980924026699A), Sep 24, 1998: Hughes 369E, Mesa, AZ, Substantial damage. Helicopter tail rotor struck the ground during practice auot rotations. (-23) while practicing/demonstrating 180 degree t/d autorotations, cip flared high and… 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.