# NTSB LAX98LA093: Boeing MD600N, N9204D, Mesa, AZ, February 3, 1998 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: February 3, 1998, 09:35 local (16:35 UTC) - Place: Mesa, AZ - Coordinates: 33.509574, -111.579498 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.5096&lon=-111.5795&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report February 15, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 30037 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX98LA093 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/30037/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=30037 - Page: https://openairdocs.org/ntsb/LAX98LA093 ## Probable cause the attempt by flight test engineers to verify a height/velocity data point that was subsequently shown to be outside the aircraft's performance capabilities. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Hard landing, emergency landing after takeoff - autorotation - intentional, pilot in command - aircraft performance,landing capability - exceeded (cause) - height/velocity curve - exceeded, production/design personnel (cause) - autorotation - not possible (cause) ## Analysis While in the process of verifying a height/velocity performance data point, the pilot entered an autorotation at takeoff power and maximum gross weight. The onboard telemetry revealed that the pilot reduced the throttle to flight idle at the entry point but that the remaining momentum caused the aircraft to accelerate and climb. During the descent, the main rotor rpm decayed and an excessive vertical sink rate developed. The aircraft landed hard at the intended touchdown point. The aircraft was hover-taxied from the landing area and a normal shutdown was completed. The test pilot reported that the height/velocity data point was outside the aircraft's performance capabilities. ## Factual narrative On February 3, 1998, at 0935 hours mountain standard time, a Boeing MD600N, N9204D, experienced a hard landing while performing an autorotative landing at Falcon Field, Mesa, Arizona. The aircraft sustained substantial damage; however, the pilot, the sole occupant, was not injured. The aircraft was being operated as a test flight by Boeing Mesa when the accident occurred. The flight originated in Mesa at 0736 on the morning of the accident. Visual meteorological conditions prevailed at the time and no flight plan was filed. At the time of the accident, the pilot was in the process of verifying a theoretical height/velocity performance data point. He had entered an autorotation at 14 feet agl and 30 knots airspeed while at takeoff power, and a gross weight of 4,100 pounds. The planned entry point was 10 feet agl and 20 knots airspeed. The onboard telemetry verified that the pilot had reduced the throttle to flight idle at the entry point. After the throttle reduction, however, the remaining momentum allowed the aircraft to accelerate to 30 knots and climb an additional 23 feet agl. During the subsequent descent, the main rotor rpm decayed and an excessive vertical sink rate developed. The aircraft landed hard at the intended touchdown point, while in a near level attitude. The aircraft was hover-taxied from the landing area and a normal shutdown was completed. A postaccident inspection of the aircraft revealed the airframe and landing gear exhibited bending, cracking, and tearing from fuselage station (FS) 78.5 to FS44.65. The bulkhead at FS124 and the engine door frame at FS137.5 were buckled and cracked on both the left and right sides. The cockpit seat pan support structures were buckled. The right and left landing gear struts were also bent and displaced. The test pilot reported that the height/velocity data point attempted was shown to be outside the aircraft's performance capabilities. ## Aircraft - Registration: [N9204D](https://openairdocs.org/deregistered/N9204D-2005-12-13), registration cancelled 2005-12-13, S/N RN004, built 1996 (OpenAirDocs) - Reported make and model: Boeing MD600N - Registry model: [Mcdonnell Douglas Helicopter 600N](https://openairdocs.org/model/mcdonnell-douglas-helicopter-600n) (registry code 3027377) (OpenAirDocs) - Registry engine: [Allison 250-C47 series](https://openairdocs.org/engine/allison-250-c47-series) (registry code 03029, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: RN004 - Airframe hours: 191 - Engines: Allison 250-C47M 650 horsepower turbo shaft - Damage: Substantial damage - Flight: Part 91 - Registered owner: Boeing Aircraft - Airworthiness certificate: Special, Experimental (Special) - Last inspection: 100 hour, May 5, 1997, 164 hours before - Departed: FFZ - Airport: FFZ, Falcon Field, runway 4L, 3,800 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 10,361 total, 308 in this make and model, 6,526 as pilot in command, 54 in the last 90 days, 18 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 40° at 1 knots - Visibility: 7 statute miles - Lowest ceiling: none - Temperature: 61 °F - Altimeter: 29.00 inHg ## 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 19980203006229A](https://openairdocs.org/incident/19980203006229A), Feb 3, 1998: Doug 600N, Mesa, AZ, Substantial damage. Proto type flight test. Velocity and height test. Damaged on hard landing other same test similiar damage. (.4) while in the process of verifying a… ## Docket (1 files) The files NTSB released with the investigation on August 4, 1998, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=30037. 401 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 401 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40389977&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.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.