# NTSB MIA07LA089: Hiller UH-12C, N92993, Plant City, FL, April 27, 2007 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: April 27, 2007, 13:45 local (17:45 UTC) - Place: Plant City, FL - Coordinates: 28, -82.150001 - Nearby events: https://openairdocs.org/map.md?lat=28.0000&lon=-82.1500&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 1 serious, 1 uninjured - Status: Completed, report December 20, 2007 - Report: Approved by Office Director - Parties: FAA FSDO - NTSB case key (mKey): 65689 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA07LA089 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/65689/pdf - Page: https://openairdocs.org/ntsb/MIA07LA089 ## Probable cause The loss of engine power due to a magneto impulse coupling failure for undetermined reasons. ## 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 - ignition system,magneto - malfunction - Forced landing, emergency descent/landing - Hard landing, emergency descent/landing - terrain condition - none suitable ## Analysis The flight instructor stated that he was conducting a discovery flight with a student, and all of a sudden, while the helicopter was in cruise flight at an altitude of 600 feet, the engine shook violently, shaking the whole helicopter. He said this lasted for several seconds and then the engine ceased operating. He said he immediately entered autorotation and attempted to affect an autorotative landing. During the landing the helicopter incurred damage. A postcrash examination of the helicopter by an FAA licensed airframe and powerplant mechanic, under the supervision of an FAA airworthiness inspector revealed that the right magneto impulse coupling had failed, and caused the impulse coupling to impact the stud used for starting. According to the inspector, this resulted in the gear train stoppage, and the engine ceasing to operate. The maintenance log revealed that the helicopter had last been given an annual inspection on June 5, 2006. ## Factual narrative On April 27, 2007, about 1345 eastern daylight time, a Hiller UH-12C helicopter, N92993, registered to and operated by Tampa Bay Helicopters Inc., as a Title 14 CFR Part 91 instructional flight, made a forced landing in a field following loss of engine power near Plant City, Florida. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight. The commercial-rated flight instructor was not injured, and the student received serious injuries. The flight originated at Vandenberg Airport, Tampa, Florida, the same day, about 1300. The flight instructor stated that he was conducting a discovery flight with a student, and all of a sudden, while the helicopter was in cruise flight at an altitude of 600 feet, the engine shook violently, shaking the whole helicopter. He said this lasted for several seconds, and then the engine ceased operating. He said he immediately entered autorotation and turned the helicopter to a westerly heading into the wind. He saw that he was not going to reach the large open field he wanted to reach, so the pilot said he selected a secondary field which was surrounded by trees of varying heights. As he was descending below the trees the pilot said the wind stopped, and it appeared that the helicopter was going to impact the northernmost tree perimeter, so he turned the helicopter. By the time he was clear of the trees the pilot said they were at an altitude of about 5 to 6 feet, and "there was nothing left to cushion the descent", so the helicopter fell to the ground, incurring damage. Postcrash examinations by an FAA licensed airframe and powerplant mechanic, under the supervision of an FAA airworthiness inspector revealed that the right magneto impulse coupling had failed and caused the impulse coupling to impact the stud used for starting. According to the inspector, this resulted in gear train stoppage, and the engine ceasing to operate. The maintenance log revealed that the helicopter had last been given an annual inspection on June 5, 2006. ## Aircraft - Registration: [N92993](https://openairdocs.org/deregistered/N92993-2013-05-22), registration cancelled 2013-05-22, S/N 852, built 1956 (OpenAirDocs) - Reported make and model: Hiller UH-12C - Registry model: [Hiller UH-12C](https://openairdocs.org/model/hiller-uh-12c) (registry code 4360116) (OpenAirDocs) - Registry engine: [Franklin 6A&6V335 series](https://openairdocs.org/engine/franklin-6a-6v335-series) (registry code 27020, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 852 - Airframe hours: 701 - Engines: Franklin 6V335 210 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: Tampa Bay Helicopters - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 1, 2006 - Departed: VDF, Tampa, FL - Destination: VDF ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; injuries: none; commercial, flight instructor; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2; last flight review February 1, 2006; seat: left; flight hours: 1,085 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 260° at 13 knots, gusting 19 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 90 °F, dew point 68 °F - Altimeter: 30.05 inHg - Observed at: PCM ## 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 20070427012289A](https://openairdocs.org/incident/20070427012289A), Apr 27, 2007: Hiller UH12C, Plant City, FL, Substantial damage. (-23) On April 27, 2007, about 1330 eastern time, a Hiller UH-12C helicopter, operating on a part 91 instruction flight made a forced landing in a field… 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.