# NTSB LAX95LA158: Robinson R-22B, N4015Y, Lakeport, CA, April 11, 1995 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: April 11, 1995, 10:48 local (17:48 UTC) - Place: Lakeport, CA - Coordinates: 39.040317, -122.929466 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.0403&lon=-122.9295&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report September 24, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 29071 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX95LA158 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29071/pdf - Page: https://openairdocs.org/ntsb/LAX95LA158 ## Probable cause the student's misjudged landing flare and his failure to verify the validity of the low rotor warning. Factors in the accident were the company management's continued use of the helicopter in flight training operations with a known discrepancy in the main rotor warning system, and the soft nature of the soil at the autorotation landing area. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, approach - vfr pattern - downwind - misc rotorcraft,main rotor rpm warning system - false indication (contributing factor) - operation with known deficiencies in equipment - continued, company/operator management (contributing factor) - rotor rpm - not verified, pilot in command (cause) - Forced landing, emergency descent/landing - autorotation - initiated, pilot in command - Roll over, landing - flare/touchdown - terrain condition - soft (contributing factor) - flare - misjudged, pilot in command (cause) ## Analysis THE STUDENT WAS DOING TAKEOFFS AND LANDINGS IN THE TRAFFIC PATTERN WHEN THE LOW ROTOR RPM WARNING HORN ACTIVATED. THE STUDENT WAS UNSUCCESSFUL IN EXTINGUISHING THE WARNING HORN BY THROTTLE AND COLLECTIVE MANIPULATION AND ENTERED AN AUTOROTATION. THE STUDENT DID NOT VERIFY THE MAIN ROTOR RPM BY THE ROTOR TACHOMETER. DURING THE TOUCHDOWN, ABOUT 1/4-MILE SOUTHEAST OF THE AIRPORT IN A SOFT FIELD, THE SKIDS DUG INTO SOFT SOIL AND THE HELICOPTER ROLLED OVER. A FAA INSPECTOR EXAMINED THE AIRCRAFT AND ENGINE, WHICH INCLUDED AN ENGINE START AND STATIC RUN-UP. THE ENGINE STARTED NORMALLY AND WAS EXERCISED THROUGHOUT ITS NORMAL POWER RANGE. MAINTENANCE RECORDS REVEALED A HISTORY OF FALSE LOW ROTOR RPM WARNING HORN ACTIVATIONS IN THE HELICOPTER DATING BACK 9 MONTHS. AFTER PILOTS WOULD REPORT THE WARNING HORN DISCREPANCY TO MAINTENANCE PERSONNEL, A SYSTEM COMPONENT WOULD BE CHANGED AND THE HELICOPTER RETURNED TO SERVICE; HOWEVER, THE PROBLEM PERSISTED. THE CFI'S SAID THEY TRAINED THE STUDENTS, INCLUDING THE ACCIDENT PILOT, HOW TO COPE WITH THE NUISANCE WARNING. ## Factual narrative On April 11, 1995, at 1048 Pacific daylight time, a Robinson R- 22B helicopter, N4015Y, rolled over during the touchdown phase of an autorotation at the Lampson Airport, Lakeport, California. The autorotation was precipitated by the activation of a low rotor rpm warning horn, which the pilot was unable to resolve. The helicopter was operated by Resort Aviation of Lakeport, and was on a student solo instructional flight. Visual meteorological conditions prevailed and included calm wind conditions. No flight plan was filed for the operation. The helicopter sustained substantial damage; however, the student pilot, the sole occupant, was not injured. The flight originated at the Lampson airport on the day of the accident at 1015 as a local traffic pattern practice student solo operation. A Federal Aviation Administration (FAA) airworthiness inspector from the Sacramento, California, Flight Standards District Office responded to the accident site, examined the wreckage, and interviewed both the student pilot and other company employees. In a verbal statement to the inspector, the student said he was performing takeoffs and landings in the traffic pattern for runway 28, and was on downwind when the low rotor rpm warning horn activated. The student said he was unsuccessful in extinguishing the warning horn by throttle and collective manipulation and entered an autorotation. The student reported that he did not verify the main rotor rpm by reference to the rotor tachometer. During the touchdown, about 1/4-mile southeast of the airport in a soft field, the skids dug into soft soil and the helicopter rolled over. The inspector examined the aircraft and engine, which included an engine start and static run-up. The engine started normally and was successfully exercised throughout its normal power range. The inspector examined the maintenance records for the helicopter and interviewed both company flight instructors and maintenance personnel. The maintenance records revealed a history of false low rotor rpm warning horn activations in the accident helicopter dating back to July of 1994. After pilots would report the warning horn discrepancy to maintenance personnel, some system component would be changed and the helicopter returned to service; however, the problem persisted. In written statements, company flight instructors reported that the accident helicopter was the only one the company had, and they felt compelled by management to fly the aircraft with the unresolved discrepancy. The instructors stated that they trained the students, including the accident pilot, how to cope with the nuisance warning. ## Aircraft - Registration: [N4015Y](https://openairdocs.org/deregistered/N4015Y-2008-07-01), registration cancelled 2008-07-01, S/N 1427 (OpenAirDocs) - Reported make and model: ROBINSON R-22B - Registry model: [Robinson Helicopter R22 BETA](https://openairdocs.org/model/robinson-helicopter-r22-beta) (registry code 7640110) (OpenAirDocs) - Category: Helicopter - Serial number: 1427 - Engines: LYCOMING O-290 140 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Resort Aviation - Registered owner: Osk Development, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, July 30, 1994 - Airport: 102, Lampson Field ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 25; student; medical: class 3, valid medical--no waivers/lim.; seat: left; flight hours: 40 total, 40 in this make and model, 40 in the last 90 days, 40 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 50 statute miles - Lowest ceiling: none - Temperature: 57 °F - Altimeter: 30.00 inHg ## 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 19950411007199A](https://openairdocs.org/incident/19950411007199A), Apr 11, 1995: Robsin R22BETA, Lakeport, CA, Substantial damage. On downwind low rotor RPM. Autorotated. Landed off field. Skids dug in. Rolled. No defects. Known false rotor horn. 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.