# NTSB MIA95LA078: Hughes 500C, N7172Z, Key Largo, FL, February 20, 1995 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: February 20, 1995, 11:00 local (16:00 UTC) - Place: Key Largo, FL - Coordinates: 25.079421, -80.439201 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=25.0794&lon=-80.4392&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report May 9, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 37733 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA95LA078 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/37733/pdf - Page: https://openairdocs.org/ntsb/MIA95LA078 ## Probable cause The pilot's misjudgment of altitude and failure to apply collective cushioning pitch during an autorotation resulting in a hard landing. Contributing to the accident was a total loss of engine power due to a loose coupling B-nut on the pneumatic fuel control system, and improper maintenance inspection of helicopter by unknown maintenance personnel. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, cruise - fuel system,line fitting - loose part/bolt/nut/clamp/etc - maintenance,inspection - improper, unknown (contributing factor) - fluid,fuel - starvation - Forced landing, descent - emergency - autorotation - performed, pilot in command - Hard landing, descent - emergency - altitude - misjudged, pilot in command (cause) - collective - not used, pilot in command (cause) ## Analysis The pilot stated he was in cruise flight at 500 feet agl when he experienced a total loss of engine power. He entered autorotation towards a highway. At 100 feet he initiated a deceleration and applied initial collective pitch at about 20 feet. Collective cushioning pitch was not applied. The helicopter collided with the ground ventral fin first, rocked forward, and slid about 150 feet. Examination of the helicopter revealed the B-nut on the after filter coupling of the fuel pressure differential switch was loose. The coupling B-nut was tightened. The engine was run in an engine test cell and developed adequate power. When the coupling B-nut was loosened the engine shut down. ## Factual narrative On February 20, 1995, about 1100 eastern standard time, a Hughes 500C, N7172Z, registered to Flying Gophers Inc., operating as a 14 CFR Part 91 personal flight, experienced a reported total loss of engine power in cruise flight in the vicinity of Key Largo, Florida. A forced landing was made on a public highway. Visual meteorological conditions prevailed and no flight plan was filed. The helicopter sustained substantial damage. The commercial pilot was not injured. The flight originated from Opa Locka Airport, Opa Locka, Florida, about 45 minutes before the accident. The pilot stated he was at 500 feet agl when he observed a high reading on the power turbine governor. He decreased the governor with the governor rpm switch and continued with the flight. About 1 minute later the helicopter experienced a total loss of engine power. The helicopter yawed to the left, followed by the illumination of the engine out warning light and engine out audio. He entered autorotation towards a highway. At 100 feet he initiated a deceleration and applied initial collective pitch at about 20 feet. Cushioning collective pitch was not applied. The helicopter collided with the ground ventral fin first, rocked forward, and slid about 150 feet before coming to a complete stop. An engine fuel and pneumatic system check was performed by McDonnell Douglas Field Service Representative under the supervision of the FAA on March 7, 1995. The fuel system failed the vacuum check. The hose assembly from the before filter (BF) port was loose at the fuel pressure switch after filter (AF) coupling B-nut of the engine-driven fuel pump. The engine was removed and transported to an authorized repair facility in Miami, Florida, for an engine test run. Before testing, it was noted that about 9cc of fuel was present in the engine-driven fuel pump filter bowl; an additional 1cc of fuel was present in the fuel nozzle inlet line. The coupling B-nut was tightened. The engine was run in a test cell on March 8, 1995, in the presence of the NTSB investigator-in-charge, and parties to the investigation. The engine started, ran, and developed adequate power. The AF filter side coupling B-nut of the fuel pressure differential switch was loosened 1 1/2 turns and the engine shut down. ## Aircraft - Registration: [N7172Z](https://openairdocs.org/deregistered/N7172Z-2012-06-18), registration cancelled 2012-06-18, S/N 1220438S, built 1970 (OpenAirDocs) - Reported make and model: HUGHES 500C - Registry model: [Hughes 500C](https://openairdocs.org/model/hughes-500c) (registry code 4470805) (OpenAirDocs) - Registry engine: [Allison 250-C20 series](https://openairdocs.org/engine/allison-250-c20-series) (registry code 03020, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 1220438S - Airframe hours: 7800 - Engines: ALLISON 250-C20 400 horsepower turbo shaft - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Flying Gophers Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 24, 1994, 59 hours before - Departed: OPF, OPA LOCKA, FL - Destination: OPF, FL ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 2,600 total, 175 in this make and model, 2,500 as pilot in command, 35 in the last 90 days, 15 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 270° at 14 knots - Visibility: 8 statute miles - Lowest ceiling: 20,000 ft broken - Temperature: 79 °F, dew point 70 °F - Altimeter: 29.00 inHg - Observed at: TMB, 20 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 19950220003539A](https://openairdocs.org/incident/19950220003539A), Feb 20, 1995: Hughes 500N, Key Largo, FL, Substantial damage. Lost power. Landed on a road. Collided with ground tail first. Loose fuel line b nut. 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.