# NTSB SEA06LA124: Hughes 369D, N88SE, Salt Lake City, UT, June 20, 2006 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 20, 2006, 10:30 local (16:30 UTC) - Place: Salt Lake City, UT - Coordinates: 40.699047, -111.939788 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.6990&lon=-111.9398&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report January 31, 2007 - Report: Approved by Office Director - Parties: Salt Lake City FSDO - NTSB case key (mKey): 63983 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA06LA124 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/63983/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=63983 - Page: https://openairdocs.org/ntsb/SEA06LA124 ## Probable cause A loss of rotor rpm for undetermined reasons, resulting in a hard landing on top of the commercial building over which the helicopter was working. ## Analysis While placing an air conditioning unit on top of a commercial building, the pilot heard the main rotor pitch droop, and confirmed that the rotor rpm was beginning to decrease. He then confirmed the throttle was open in the full flight position, moved the load away from the personnel on the roof, and lowered the collective. The low rotor audio sounded, and the rotor rpm continued to decrease, so the pilot hit the load release switch and autorotated to an emergency landing on top of the roof. After a hard touchdown, the aircraft bounced, touched down again, and then balanced on the right skid before very slowly rolling onto its right side. The load he was placing on the roof weighed less than one-half of what the helicopter was capable of lifting under the ambient conditions, and neither an engine/airframe inspection nor a test run of the engine were able to establish any anomalies or the initiating factor in the rotor droop event. ## Factual narrative On June 20, 2006, approximately 1030, mountain daylight time, a Hughes 369D helicopter, N88SE, rolled over onto its side after autorotating to a hard landing to the top of a commercial building in Salt Lake City, Utah. The airline transport pilot, who was the sole occupant, was not injured, but the aircraft, which is owned by Pathfinder Leasing LLC, sustained substantial damage. The 14 CFR Part 133 long-line external load flight, which initially departed Bountiful, Utah, about 0840, was being operated in visual meteorological conditions. According to the pilot, who had already lifted 20 of 24 air conditioning units into place on top of the 30 foot tall building, just before placing the twenty-first unit on top of the building, he heard what he believed was a main rotor pitch droop. He then quickly looked at the main rotor rpm on the tachometer, which confirmed that the rotor rpm was beginning to decrease. He then confirmed the throttle was open in the full flight position, moved the load away from the personnel on the roof, and lowered the collective. The low rotor audio sounded, and the rotor rpm continued to decrease, so the pilot hit the load release switch and autorotated to an emergency landing on top of the roof. After touchdown, the aircraft bounced, touched down again, and then balanced on the right skid before very slowly rolling onto its right side. According to the pilot's calculations, the ambient conditions on the day of the accident allowed for loads up to 1,000 pounds, and it was determined that the load he was lifting was no greater than 425 pounds. A post-accident inspection of the airframe and engine did not reveal any malfunction or anomalies that would have contributed to a reduction in engine or rotor rpm. The engine was shipped to the Rolls-Royce inspection/test run facility in Indianapolis, Indiana, where it underwent an FAA-supervised test run. During all portions of the test run regime, the engine performed at or above all required specifications, and at full throttle produced power 11.9 percent above required output. At the end of the investigative process, no clear determination of the source of the rotor droop event could be established. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, hover - out of ground effect - reason for occurrence undetermined (cause) - Hard landing, emergency landing - terrain condition - other ## Aircraft - Registration: [N88SE](https://openairdocs.org/deregistered/N88SE-2013-10-29), registration cancelled 2013-10-29, S/N 800775D, built 1980 (OpenAirDocs) - Reported make and model: Hughes 369D - Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs) - Registry engine: [Allison 250 SER 250HP](https://openairdocs.org/engine/allison-250-ser-250hp) (registry code 03002, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 800775D - Airframe hours: 4610 - Engines: Allison 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: External load, Part 133 - Registered owner: Pathfinder Leasing LLC - Airworthiness certificate: Standard, Utility - Last inspection: 100 hour, May 1, 2005 - Departed: KBTF, Bountiful, UT - Destination: KBTF, Salt Lake City, UT - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 42; injuries: minor; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 1, without waivers/limitations; last flight review May 1, 2006; seat: left; flight hours: 8,821 total, 905 in this make and model, 6,779 as pilot in command, 134 in the last 90 days, 39 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 73 °F - Altimeter: 30.11 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 20060620012249A](https://openairdocs.org/incident/20060620012249A), Jun 20, 2006: Hughes 369D, Salt Lake City, UT, Substantial damage. (-23) While lifting a sling load consisting of a 430 pound air ventilation van to the roof top of a window manufacturing plant the aircraft experienced a loss… ## Other investigations on N88SE (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 CHI92LA017](https://openairdocs.org/ntsb/CHI92LA017), Oct 23, 1991: Mcdonnell Douglas MD369D (N88SE), Beech Grove, IN, substantial damage. Probable cause: IMPROPER INSTALLATION OF THE FLIGHT CONTROL LINKAGE DURING MAINTENANCE. COMPLACENCY AND INADEQUATE INSPECTION OF THE HELICOPTER BY MAINTENANCE PERSONNEL AND THE PILOT ARE FACTORS IN THE ACCIDENT. ## Docket (1 files) The files NTSB released with the investigation on November 9, 2006, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=63983. 397 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 397 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40268698&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.