# NTSB ATL00LA030: Burak Stanley A XF4, N9VY, Brooksville, FL, February 29, 2000 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: February 29, 2000, 15:45 local (20:45 UTC) - Place: Brooksville, FL - Coordinates: 28.439104, -82.559631 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=28.4391&lon=-82.5596&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report December 4, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 48694 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL00LA030 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/48694/pdf - Page: https://openairdocs.org/ntsb/ATL00LA030 ## Probable cause The owner/builder's failure to build the airplane within the design stress limits of the drive shaft assembly, that resulted in the failure of the Flex Coupling Retention Bolts. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(partial) - mech failure/malf, cruise - normal - propeller system/drive assembly - failure - design stress limits of aircraft - exceeded, owner/builder (cause) - material inadequate,improper, owner/builder (cause) - In flight collision with terrain/water, emergency descent/landing ## Analysis Approximately 35 minutes in to the flight, the pilot experienced a loss of propeller thrust. The pilot stated that he heard a loud 'bang' from the engine compartment and experienced loss of thrust. The pilot said that the engine tachometer went to redline, and the propeller rpm decreased. The pilot said , changing the engine rpm did not change the propeller rpm. The pilot declared an emergency and started an emergency descent for a landing on runway 27. As the pilot maneuvered the airplane on the final approach, he cleared a stand of trees on the final approach to runway 27. While on short final to land, the airplane initially collided with the ground short of the runway surface and subsequently came to rest on a taxiway. The examination of the wreckage revealed that the Rex Flex Coupling Assembly had failed and that three out of the six Rex Bolts had also failed. The pilot stated that the Flexidyne Drive Shaft was designed for a 100 horse-power engine. The pilot/builder stated that he installed a 150 horse power engine on the airplane. ## Factual narrative On February 29, 2000, at 1545 eastern standard time, a Burak XF4, experimental airplane, N9VY, collided with the ground following a loss of propeller thrust at the Brooksville Hernando County Airport in Brooksville, Florida. The personal flight was operated by the pilot under the provisions of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed and no flight plan was filed for the local flight. The pilot received minor injuries and the airplane sustained substantial damage. The flight originated from Brooksville Airport, in Brooksville, Florida, at 1500. According to the pilot, 35 minutes in to the flight, while circling Hernando County Airport, Brooksville, Florida, at 3000 feet, the pilot experienced a loss of propeller thrust. The pilot stated that he heard a loud "bang" from the engine compartment and experienced loss of thrust. The pilot said that the engine tachometer went to redline, and the propeller rpm decreased. According to the pilot, changing the engine rpm did not change the propeller rpm. The pilot declared an emergency and started an emergency descent for a landing on runway 27. As the pilot maneuvered the airplane on the final approach, he cleared a stand of trees on the final approach to runway 27. While on short final to land, the airplane initially collided with the ground short of the runway surface and subsequently came to rest on a taxiway. According to the pilot, the examination of the wreckage revealed that the Rex Flex Coupling Assembly failed. The Rex Flex Coupling assembly connects the engine to the propeller drive shaft and pusher propeller. The pilot reported that three out of the six Rex Bolts (#16087) failed and one bolt was found with the head sheared off. According to the pilot, he cannot recall the torque applied to the flange assembly during installation nor did he recall the maximum required torque for this installation. The pilot stated that the Flexidyne Drive Shaft was designed for a 100 horse-power engine. The pilot/builder stated that he installed a 150 horse power engine on the airplane. ## Aircraft - Registration: [N9VY](https://openairdocs.org/deregistered/N9VY-2000-04-18), registration cancelled 2000-04-18, S/N 1973-92 (OpenAirDocs) - Reported make and model: Burak Stanley A XF4 - Registry model: [Burak Stanley A XF4](https://openairdocs.org/model/burak-stanley-a-xf4) (registry code 056123D) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 1973-92 - Airframe hours: 9 - Engines: Lycoming O-320 150 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Stanley A. Burak - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, September 15, 1999, 2 hours before - Departed: BKV - Airport: BKV, Hernando County, runway 27, 7,001 × 150 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; airline transport, flight engineer, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: front; flight hours: 8,866 total, 9 in this make and model, 4,138 as pilot in command, 5 in the last 90 days, 3 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 77 °F, dew point 55 °F - Altimeter: 30.00 inHg - Observed at: PIE, 41 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 20000229014359A](https://openairdocs.org/incident/20000229014359A), Feb 29, 2000: Amtr XF4, Brooksville, FL, Substantial damage. (.4) Approximately 35 minutes in to the flight, the pilot experienced a loss of propeller thrust. The pilot stated that he heard a loud 'bang' from the engine… 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.