# NTSB LAX96LA207: McDonnell Douglas MD-600, N600RN, Thermal, CA, May 28, 1996 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: May 28, 1996, 07:11 local (14:11 UTC) - Place: Thermal, CA - Coordinates: 33.990272, -117.379325 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.9903&lon=-117.3793&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report August 20, 1996 - Report: Approved by Office Director - NTSB case key (mKey): 29449 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX96LA207 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29449/pdf - Page: https://openairdocs.org/ntsb/LAX96LA207 ## Probable cause inadequate design of the stress limits for cyclic control of the helicopter. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Abrupt maneuver, maneuvering - design stress limits of aircraft - performed, pilot in command - Airframe/component/system failure/malfunction, maneuvering - misc rotorcraft,main rotor/tail boom contact - acft/equip,inadequate design, manufacturer (cause) - Forced landing, emergency descent/landing - Hard landing, emergency descent/landing - terrain condition - high vegetation ## Analysis The flight was part of an engineering test flight series to complete the Part 27 certification for a new rotorcraft. The specific test point was part of a flight strain survey and involved cyclic control reversals. The pilot had set the parameters and executed the cyclic control inputs as planned. Almost simultaneous with the aft movement of the cyclic there was a loud noise and immediate vibrations in the aircraft and the controls. A pilot in the chase aircraft informed the pilot that a main rotor blade had struck and severed the tail boom. A power off autorotation was accomplished without the tail rotor system. The resultant hard landing was onto a pile of dry brush which was ignited by the hot engine exhaust. The brush fire destroyed the aircraft. ## Factual narrative On May 28, 1996, about 0711 hours Pacific daylight time a McDonnell Douglas MD-600 helicopter, N600RN, was destroyed during flight tests at Thermal, California. The pilot was not injured. The helicopter was in a flight test program for FAA certification under 14 CFR Part 27. The specific test point at the time of the mishap was part of a flight strain survey and involved cyclic control reversals. The pilot set the parameters and executed the cyclic inputs as planned. Almost simultaneous with the aft movement of the cyclic there was a loud noise and immediate vibrations in the aircraft and controls. There was a chase aircraft for the mission and the chase pilot advised that the tail boom had been struck by a main rotor blade and had separated from the airframe. The pilot of the mishap aircraft then experimented with powered flight, but found that the right yaw was not controllable. He elected to continue the power off autorotation with a controllable left yaw. The autorotation was continued to a vacant field with some piles of brush and other desert debris. The pilot used available rotor rpm, cyclic, and collective control to execute a modified autorotation landing. The resultant landing was onto a brush pile with some skid and main rotor blade damage. The engine exhaust was adjacent to dry brush and grass which resulted in a grass fire. The ground fire destroyed the helicopter. ## Aircraft - Registration: [N600RN](https://openairdocs.org/deregistered/N600RN-1996-08-14), registration cancelled 1996-08-14, S/N RN001 (OpenAirDocs) - Reported make and model: McDonnell Douglas MD-600 - Registry model: [Mcdonnell Douglas Helicopter 600N](https://openairdocs.org/model/mcdonnell-douglas-helicopter-600n) (registry code 3027377) (OpenAirDocs) - Category: Helicopter - Serial number: RN001 - Airframe hours: 39 - Engines: Allison 250-C47 621 horsepower turbo shaft - Damage: Destroyed - Fire: On-Ground - Flight: Part 91 - Registered owner: Mcdonnell Douglas Helicopter - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, December 15, 1995, 39 hours before - Departed: TRM, CA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 48; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 10,191 total, 1,095 in this make and model, 8,000 as pilot in command, 40 in the last 90 days, 20 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 320° at 7 knots - Visibility: 20 statute miles - Lowest ceiling: none - Temperature: 68 °F, dew point 52 °F - Altimeter: 29.00 inHg - Observed at: TRM, 4 nm away ## 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 19960528011679A](https://openairdocs.org/incident/19960528011679A), May 28, 1996: Ayres 600S2C, Thermal, CA, Destroyed. During reverse cyclic flight test main rotor severed tailboom. Autorotated. Landed in brush. Exhaust caused fire. 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.