# NTSB LAX99LA186: Robinson R22A, N8558N, San Luis Obispo, CA, May 19, 1999 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: May 18, 1999, 17:30 local (May 19, 1999, 00:30 UTC) - Place: San Luis Obispo, CA - Coordinates: 35.250358, -120.619186 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.2504&lon=-120.6192&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed, report December 4, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 46343 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX99LA186 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46343/pdf - Page: https://openairdocs.org/ntsb/LAX99LA186 ## Probable cause The student's inadvertent and uncoordinated application of forward cyclic during an autorotation flare, which resulted in a loss of main rotor rpm; and the flight instructor's inadequate supervision. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of control - in flight, approach - vfr pattern - final approach - weather condition - gusts - autorotation - performed - rotorcraft flight controls - improper use of, dual student - cyclic - inadvertent activation, dual student (cause) - rotor rpm - not maintained, dual student (cause) - supervision - inadequate, pilot in command(cfi) (cause) - In flight collision with terrain/water, descent - uncontrolled - terrain condition - mountainous/hilly - Roll over, descent - uncontrolled ## Analysis The instructor stated the student entered a practice autorotation at 1,400 feet (600 feet agl) to a landing site on top of a hill about 800 feet high. As the flare was initiated at 40 to 50 feet, the instructor mentioned to the student that the cyclic trim was engaged. When the student unexpectedly reached forward and tried to push the trim control knob in, he inadvertently pushed forward on the cyclic control. The instructor said this pitched the nose of the helicopter down and resulted in a bleed off of main rotor rpm. When the low rotor horn and warning light came on the instructor took control of the helicopter and rolled in throttle. The lowest rpm he recalls seeing was slightly above 90 percent. He made a left turn to avoid hitting the hill and encountered a strong downdraft due to the gusty winds. The helicopter touched down on the left skid during the turn and rolled over twice. ## Factual narrative On May 18, 1999, about 1730 hours Pacific daylight time, a Robinson R22A, N8558N, sustained substantial damage during a hard landing and rollover near San Luis Obispo, California. A certified flight instructor and student, the sole occupants, were practicing autorotations in a hilly area approximately 5 miles east of the San Luis Obispo airport. Both pilots received minor injuries. Helipro, Inc., of San Luis Obispo, was operating the instructional flight under the provisions of 14 CFR Part 91. The flight originated in San Luis Obispo about 1630 and no flight plan was filed. Visual meteorological conditions prevailed. An aviation routine weather report (METAR) issued for San Luis Obispo at 1717 indicated broken skies at 1,000 feet with winds at 17 knots gusting to 24 knots. The operator stated the pilots received a DUATS weather briefing prior to departure. They departed to the east, which was clear but windy. The instructor stated the student entered a practice autorotation at 1,400 feet (600 feet agl). The selected landing site was on top of a hill approximately 800 feet high. As the flare was initiated at 40 to 50 feet, the instructor mentioned to the student that the cyclic trim was engaged. When the student unexpectedly reached forward and tried to push the trim control knob in, he inadvertently pushed forward on the cyclic control. The instructor said this pitched the nose of the helicopter down and resulted in a bleed off of main rotor rpm. When the low rotor horn and warning light came on the instructor took control of the helicopter and rolled in throttle. The lowest rpm he recalls seeing was slightly above 90 percent. He made a left turn to avoid hitting the hill and encountered a strong downdraft due to the gusty winds. The helicopter touched down on the left skid during the turn and rolled over twice. The pilots were able to extricate themselves and walk to a farmhouse for help. The instructor stated the cyclic trim was used during cruise to relieve stick loads. He indicated the helicopter could be easily controlled in all flight regimes with the cyclic trim on or off. He normally flies with it off, but teaches its use because the flight examiner required a demonstration of its use on check rides. He said there was no checklist requiring it be turned off prior to practicing autorotations. He said it was controlled by a push/pull knob located on the console in front of the cyclic. The knob has to be pushed in approximately 4 inches to turn the trim off. ## Aircraft - Registration: [N8558N](https://openairdocs.org/deregistered/N8558N-2000-08-04), registration cancelled 2000-08-04, S/N 0466 (OpenAirDocs) - Reported make and model: Robinson R22A - Registry model: [Robinson Helicopter R22 ALPHA](https://openairdocs.org/model/robinson-helicopter-r22-alpha) (registry code 7640104) (OpenAirDocs) - Category: Helicopter - Serial number: 0466 - Airframe hours: 9536 - Engines: Lycoming O-320-B2C 160 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: Helipro, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, May 7, 1999, 48 hours before - Departed: SBP ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 24; flight instructor, commercial; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 369 total, 364 in this make and model, 317 as pilot in command, 164 in the last 90 days, 125 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 17 knots, gusting 24 - Visibility: 10 statute miles - Lowest ceiling: 1,000 ft broken - Temperature: 55 °F, dew point 52 °F - Altimeter: 29.00 inHg - Observed at: SBP, 5 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 19990518005389A](https://openairdocs.org/incident/19990518005389A), May 18, 1999: Robsin R22ALPHA, San Luis Obispo, CA, Substantial damage. Robinson R-22 helicopter was involved in auto rotation practice when the acft caught a down draft, struck the ground hard, rolled over, and was destroyed,… 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.