# NTSB LAX98LA178: Fields Baby Belle, N656VK, Inyokern, CA, May 31, 1998 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: May 31, 1998, 11:45 local (18:45 UTC) - Place: Inyokern, CA - Coordinates: 35.879901, -118.150733 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.8799&lon=-118.1507&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report August 3, 1999 - Report: Approved by Office Director - NTSB case key (mKey): 30103 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX98LA178 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/30103/pdf - Page: https://openairdocs.org/ntsb/LAX98LA178 ## Probable cause The failure of the pilot to recover from a low rotor rpm condition, which resulted in a loss of aircraft control. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of control - in flight, takeoff - initial climb - collective - improper, pilot in command (cause) - remedial action - improper, pilot in command (cause) - rotor rpm - not maintained, pilot in command (cause) - In flight collision with terrain/water, descent - uncontrolled - terrain condition - rough/uneven ## Analysis The pilot took off and approximately 40 mph and 60 feet agl, he felt an increasing vibration which he attempted to reduce by raising the collective. He decided to land and as he applied aft cyclic and reduced the collective, the aircraft began yawing to the left and he ran out of right pedal. The aircraft nosed over in an uncontrolled descent and impacted the ground at approximately a 45-degree nose-down attitude and 20-30 degree left roll. The pilot reported that he built the kit helicopter, which has a total time of 67 hours. The kit does not include a low rotor rpm warning system. The pilot holds a private pilot certificate with a single engine land rating and has a helicopter solo endorsement dated August 22, 1997. ## Factual narrative On May 31, 1998, at 1145 hours Pacific daylight time, a Fields Baby Belle experimental helicopter, N656VK, crashed approximately 5 miles northwest of Inyokern, California. The aircraft was destroyed and the private pilot/owner, the sole occupant, suffered serious injuries. The personal flight originated at the pilot's home and was en route to the Inyokern airport to refuel. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that during the preflight, he found a piece of the engine cooling shroud rubbing against the engine flywheel. He further stated that the first run-up was aborted due to metal chaffing sounds near the fan housing. The pilot estimated that he had approximately 10 gallons of fuel onboard prior to takeoff. He reported that the purpose of the flight was to fly to Inyokern airport to obtain fuel and to practice approaches and landings. The pilot reported that he took off and passed through translational lift. Approximately 40 mph and 60 feet agl, he felt a vibration, which began increasing. The pilot reported that the tachometer needle was in the green arc. He stated that he attempted to reduce the vibration by raising the collective. The pilot reported that he decided to land and as he applied aft cyclic and reduced the collective, the aircraft began yawing to the left and he ran out of right pedal. The aircraft then nosed over in an uncontrolled descent and impacted the ground at approximately a 45-degree nose-down attitude and 20-30 degree left roll. The helicopter came to rest on its right side. There were three eyewitnesses to the accident. They reported that just after takeoff, they saw the helicopter turn left, dip the nose down and to the left, and drop forward to the ground in about a 30-45 degree slope. Upon reaching the accident site, the witnesses noted that the cockpit bubble had burst outward and toward the passenger side. The cyclic stick was gone, with just wires left. One main rotor blade was bent along the ground. The transmission was torn out and tilted toward the pilot's side of the ship. One of the tail rotor blades was bent. The pilot reported that he built the kit helicopter, which has a total time of 67 hours. The kit does not include a low rpm warning system. According to the kit manufacturer, the main rotor blades rotate clockwise and the tail rotor rotates 5.5 revolutions for every single revolution of the main rotor. If a low main rotor rpm situation is encountered and anti-torque is not reduced through the pedals, the aircraft will yaw to the left. Power available from the engine is directly proportional to rpm. If the rpm drops 10 percent, there is 10 percent less power. With less power, the helicopter will start to settle, and if the collective is raised to stop it from settling, the rpm will be pulled down even lower, causing the ship to settle even faster. If rotor stall occurs, the blades will either "blow back" and cut off the tail cone or it will just stop flying, allowing the helicopter to fall at an extreme rate. The recovery from low rpm is to add throttle and lower collective. The pilot holds a private pilot certificate with a single engine land rating and has a helicopter solo endorsement dated August 22, 1997. ## Aircraft - Registration: [N656VK](https://openairdocs.org/deregistered/N656VK-2014-04-14), registration cancelled 2014-04-14, S/N VK01, built 1977 (OpenAirDocs) - Reported make and model: Fields BABY BELLE - Registry model: [Fields Stuart G BABY BELLE](https://openairdocs.org/model/fields-stuart-g-baby-belle) (registry code 05604K2) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Helicopter, amateur-built - Serial number: VK01 - Airframe hours: 67 - Engines: Lycoming O-320-D2J 160 horsepower reciprocating - Damage: Destroyed - Flight: Personal, Part 91 - Registered owner: Stuart G. Fields - Airworthiness certificate: Special, Experimental (Special) ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 61; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: right; flight hours: 315 total, 60 in this make and model, 213 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 20 statute miles - Lowest ceiling: none - Temperature: 72 °F - Altimeter: 30.00 inHg - Observed at: IYK, 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 19980531011479A](https://openairdocs.org/incident/19980531011479A), May 31, 1998: Amtr BABYBELLE, Inyokern, CA, Destroyed. Vibrations and yaw after takeoff. Nosed over. Uncontrollable descent. Not equipped with low rotor RPM warning light (.4)the pilot took off and approximately 40… 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.