# NTSB MIA94LA176: Robinson R-22, N22431, Sanford, FL, July 9, 1994 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 9, 1994, 12:50 local (16:50 UTC) - Place: Sanford, FL - Coordinates: 28.810995, -81.329895 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=28.8110&lon=-81.3299&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report November 18, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 37573 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA94LA176 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/37573/pdf - Page: https://openairdocs.org/ntsb/MIA94LA176 ## Probable cause THE FAILURE OF THE TAILROTOR DRIVESHAFT FOR UNDETERMINED REASONS RESULTING IN LOSS OF TAILROTOR DRIVE. THIS RESULTED IN THE HELICOPTER SPINNING UNCONTROLLED AND DESCENDING FROM A HOVER UNTIL IT CRASHED IN THE WATER. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, hover - rotor drive system,tail rotor drive shaft - failure,total (cause) - rotor drive system,tail rotor drive shaft - undetermined (cause) - In flight collision with terrain/water, descent - uncontrolled - aircraft control - not possible, pilot in command - descent - uncontrolled - terrain condition - water ## Analysis THE HELICOPTER WAS IN A 15 FOOT HOVER WHEN IT BEGAN TO SPIN TO THE RIGHT AND DESCEND. THE PILOT WAS UNABLE TO CONTROL THE HELICOPTER AND IT CRASHED INTO THE WATER. A WITNESS ON THE GROUND OBSERVED THE TAILROTOR SLOW DOWN JUST PRIOR TO THE HELICOPTER STARTING TO SPIN TO THE RIGHT. EXAMINATION OF THE HELICOPTER AFTER THE ACCIDENT INDICATED THE TAILROTOR DRIVESHAFT WAS SEPARATED AT THE LAST COUPLING PRIOR TO THE TAILROTOR GEARBOX. THE TAILROTOR GEARBOX WAS FREE TO TURN AND ONE TAILROTOR BLADE WAS BENT AT A 90 DEGREE ANGLE. THE OTHER TAILROTOR BLADE WAS NOT DAMAGED. METALLURGICAL EXAMINATION OF THE SEPARATED TAILROTOR DRIVESHAFT INDICATED IT SEPARATED DUE TO TORSIONAL OVERSTRESS IN THE NORMAL DIRECTION OF ROTATION. THE DRIVESHAFT HAD ACCUMULATED 887 TOTAL HOURS SINCE IT WAS INSTALLED NEW IN JUNE 1992. THE HELICOPTER HAD BEEN SUBJECTED TO AN OVERSPEED AND TWO GROUND DAMAGE OCCURRENCES TO THE TAIL STABILIZERS IN THE LAST 150 FLIGHT HOURS. ## Factual narrative On July 9, 1994, about 1250 eastern daylight time, a Robinson R22 Alpha, N22431, registered to Palm Beach Helicopters, Inc., made a forced landing in the St. Johns River near Sanford, Florida, while on a 14 CFR Part 91 aerial observation flight. Visual meteorological conditions prevailed at the time and no flight was filed. The aircraft received substantial damage and the commercial-rated pilot and one passenger were not injured. The flight originated at Sanford, Florida, on July 9, 1994, about 1240. The pilot stated that while maneuvering at about 15 feet above the river to spot alligators, the helicopter began to spin to the right. He lowered the collective pitch control and lowered the nose thinking that the wind was causing the spin. This had no affect and he had to ditch the helicopter in the river. A witness on a boat told him that the tailrotor had stopped before the helicopter ditched. Postcrash examination of the helicopter by a FAA inspector indicated the tailrotor driveshaft was separated near the last coupling before the tailrotor gearbox. One tailrotor blade had a 90-degree bend in it across the blade face and the other blade was not damaged. The tailrotor gearbox turned freely. Metallurgical examination of the separated tailrotor driveshaft was conducted by Mr. Joe Epperson, Senior Metallurgist, NTSB, Washington, D.C. The shaft separated due to torsional overload in the normal direction of rotation. There was no evidence of preexisting cracks or abnormalities. See attached metallurgist's factual report. Logbook records indicate the tailrotor driveshaft was new when it was installed by Robinson Helicopter during helicopter overhaul on June 22, 1992, at aircraft total time 1,997 hours. The shaft had accumulated 887 total flight hours since new at the time of the accident. Logbook records indicated the helicopter received a overspeed inspection on November 17, 1993, at total aircraft time 2,637. On December 1, 1993, the lower vertical stabilizer was replaced due to ground damage. On June 21, 1994, at aircraft time 2,851 hours, the horizontal stabilizer was changed due to ground damage. See attached logbook pages. ## Aircraft - Registration: [N22431](https://openairdocs.org/deregistered/N22431-2013-06-13), registration cancelled 2013-06-13, S/N 0494 (OpenAirDocs) - Reported make and model: ROBINSON R-22 - Registry model: [Robinson Helicopter R22 ALPHA](https://openairdocs.org/model/robinson-helicopter-r22-alpha) (registry code 7640104) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 0494 - Airframe hours: 2884 - Engines: LYCOMING O-320-B2C 124 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Registered owner: Palm Beach Helicopters Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, April 28, 1994, 60 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 28; commercial; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 200 total, 199 in this make and model, 135 as pilot in command, 35 in the last 90 days, 16 in the last 30 days, 10 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 90 °F, dew point 70 °F - Altimeter: 30.00 inHg - Observed at: SFD, 3 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 19940709017889A](https://openairdocs.org/incident/19940709017889A), Jul 9, 1994: Robsin R22ALPHA, Sanford, FL, Substantial damage. Flying low to spot alligators. Lost tail rotor control. Ditched in river. Driveshaft broke due overload. Prior strike 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.