# NTSB FTW97LA328: Fingerhut Revolution Mini 500, N570F, Huffman, TX, August 27, 1997 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 26, 1997, 20:00 local (Aug 27, 1997, 01:00 UTC) - Place: Huffman, TX - Coordinates: 30.059494, -95.089965 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=30.0595&lon=-95.0900&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report May 4, 1998 - Report: Approved by Office Director - NTSB case key (mKey): 20328 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW97LA328 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/20328/pdf - Page: https://openairdocs.org/ntsb/FTW97LA328 ## Probable cause The disengagement of the helicopter's collective control tube due to improper installation by the builder. Factors were the lack of sufficient information provided by the kit manufacturer and the pilot's inability to cushion the landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - rotorcraft flight control system - failure (cause) - rotorcraft flight control,collective control rod - disengaged (cause) - maintenance,installation - improper, owner/builder (cause) - information insufficient, kit manufacturer (contributing factor) - Forced landing, emergency landing - Loss of control - on ground/water, emergency landing - level off - not possible, pilot in command (contributing factor) ## Analysis The student pilot experienced a disconnect of the collective control system which resulted in the main rotor blades going to flat pitch while in cruise flight at 800 feet MSL. When the pilot attempted to cushion the landing by increasing collective pitch, the helicopter yawed to the left prior to touching down and the helicopter rolled over on its side. Examination of the wreckage revealed a disconnect of the collective flight control system between the collective riser block (P/N 0153), and the rod end (P/N 0600) for the collective control tube. Examination of the threaded areas of the collective riser block and the rod end revealed that the threads on the aluminum collective riser block were found to be displaced or pulled out due to inadequate improper penetration. The information supplied by the kit manufacturer was insufficient to properly rig the flight control system. ## Factual narrative On August 26, 1997, at 2000 central daylight time, a Fingerhut Revolution Mini 500 homebuilt helicopter, N570F, was substantially damaged during a forced landing near Huffman, Texas. The student pilot, sole occupant of the helicopter, was not injured. The helicopter was owned and operated by the pilot under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local flight for which a flight plan was not filed. The instructional flight originated from a helipad at the pilot's home in Huffman, Texas at 1945. According to the pilot, he experienced a disconnect of the collective control system which resulted in the main rotor blades going to flat pitch while in cruise flight at 800 feet MSL. The pilot added that he elected to execute a running landing to a cultivated field rather that try to land in a confined helipad. During the landing flare the helicopter yawed to the left as the pilot applied collective to cushion the landing prior to touching down. The pilot added that the helicopter was not properly aligned during touch down and the helicopter rolled over on its side. The FAA inspector confirmed that the 1997 model helicopter sustained structural damage. He added that the student pilot was properly endorsed for solo flight and had accumulated a total of 50 hours of flight in helicopters, of which 28 were in the same make and model. According to the aircraft maintenance records, the helicopter had accumulated a total of 28 hours since it was assembled by the pilot from a kit. Flight control continuity was confirmed by the FAA inspector to the cyclic and anti-torque systems of the helicopter. Examination of the helicopter by the FAA inspector revealed that a disconnect of the collective flight control system between the collective riser block (P/N 0153), and the rod end (P/N 0600) for the collective control rod (P/N 0002). With the aid of 10 power magnification, the inspector examined the threaded areas of the collective riser block and the rod end. The threads on the aluminum collective riser block were found to be displaced or pulled out. See enclosed drawing showing the 0.314 inch penetration on the threaded surface of the riser block and the first 0.388 inch engagement on the rod end. The FAA inspector also noted that the control rods provided by the helicopter manufacturer were not provided with a "witness hole" so either the installer or an inspector could verify the amount of rod end penetration into the threaded control tube. Furthermore, the assembly instructions provided by the manufacturer did not stipulate the minimum amount of thread engagement required in any of the rod ends in any of the flight control tubes in the helicopter, nor did it warn the potential builder of the criticality of proper thread engagement and security. To assist with the investigation, the FAA inspector inspected a like helicopter to establish a comparison on the installation of the flight control systems. The comparison between the two installations revealed that a pronounced difference existed in the length of exposed threaded areas between the rod ends and the control rods. The owner/builder of the helicopter provided the FAA inspector with the plans and instructions provided to him by the kit manufacturer during the assembly of the helicopter. ## Aircraft - Registration: [N570F](https://openairdocs.org/aircraft/N570F), registered now, S/N 109, built 1997 (OpenAirDocs) - Reported make and model: FINGERHUT REVOLUTION MINI 500 - Registry model: [Fingerhut Steven MINI 500](https://openairdocs.org/model/fingerhut-steven-mini-500) (registry code 05603K0) (OpenAirDocs) - Registry engine: [Bombardier ROTAX (ALL)](https://openairdocs.org/engine/bombardier-rotax-all) (registry code 09050, reciprocating) (OpenAirDocs) - Category: Helicopter, amateur-built - Serial number: 109 - Airframe hours: 28 - Engines: Rotax 582 67 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: Steve Fingerhut - Airworthiness certificate: Special, Experimental (Special) - Departed: NONE, TX ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 36; student; medical: class 3, valid medical--no waivers/lim.; seat: center; flight hours: 42 total, 26 in this make and model, 26 as pilot in command, 27 in the last 90 days, 19 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 140° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 68 °F - Altimeter: 30.00 inHg - Observed at: IAH, 16 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 19970826023989A](https://openairdocs.org/incident/19970826023989A), Aug 26, 1997: Amtr MINI500, Huffman, TX, Substantial damage. Collective disconnect. Damaged on run on log. Failed preflite collective used incorrect control inputs. Unskilled. (-23) see narrative #FTW97LA320 (.19) on… 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.