# NTSB MIA99LA217: Bell 47G-B3, N6712D, Selma, AL, August 8, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 8, 1999, 16:00 local (21:00 UTC) - Place: Selma, AL - Coordinates: 32.41098, -87.030624 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.4110&lon=-87.0306&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report November 30, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 47033 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA99LA217 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/47033/pdf - Page: https://openairdocs.org/ntsb/MIA99LA217 ## Probable cause The pilot's failure to maintain the proper touchdown point during landing causing the landing skid to become entangled with the edge of the helipad platform and the resultant rollover and main rotor blade strike of the tow vehicle. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Roll over, landing - proper touchdown point - not maintained, pilot in command (cause) - rotor system,main rotor - blade strike - object - vehicle ## Analysis After a test flight following maintenance, the pilot/owner was positioning the helicopter onto a trailer, (tail forward) when the right landing skid slipped off and became hooked on the edge of the landing platform. Despite full forward, left cyclic, the rotorcraft continued backward until the main rotor blades collided with the aft part of the truck. The main rotor pitch control rods were removed and shipped to the NTSB Materials Laboratory for failure analysis, and although the rods were found to possess under specification tensile strength, all damage appeared to be consistent with impact damage. ## Factual narrative On August 8, 1999, about 1600 central daylight time, a Bell 47G-3B, N6712D, registered to Precision Air Services, Inc., operating as a Title 14 CFR Part 91 maintenance test flight, crashed while attempting a landing onto a trailer near Selma, Alabama. Visual meteorological conditions prevailed and no flight plan was filed. The helicopter received substantial damage, the trailer-truck helipad was damaged, and the commercially-rated pilot and a passenger were not injured. The flight originated from the same location about 20 minutes before the accident. According to the pilot, during his landing attempt, the right skid became hooked on the trailer, and the helicopter sustained a dynamic rollover, damaging the main and tail rotor blades, the main rotor mast, and the tail boom. In his statement the pilot stated, "I screwed up." According to FAA personnel, postcrash pilot interview and examination of the damaged main rotor system and rotor collision damage to the trailer and truck revealed that during the landing phase onto the helipad, the right landing skid slid off the landing platform and the pilot's control correction, (full forward and left cyclic) led to a main rotor thrust vector similar to what would be experienced in a dynamic rollover. The main rotor pitch change control rods were sent to the NTSB Materials Laboratory for failure analysis. It was determined the components were part of a main rotor mast modification approved as Supplemental Type Certificate (STC) SH2772SW. The difference between the original and the replacement mast head controls is illustrated in Figure 2 of the enclosed report titled, "NTSB Materials Laboratory Factual Report". All separation and bending overstress damage to the components appeared consistent with impact damage. The center hexagons of three of the control rods were hardness tested using a Rockwell "A" scale indenter. The equivalent tensile strength specifications on the samples were found to be under that required by drawings of the control rods; however, it is not considered a factor in this accident. For additional information, see "NTSB Materials Laboratory Factual Report." ## Aircraft - Registration: [N6712D](https://openairdocs.org/deregistered/N6712D-2012-09-20), registration cancelled 2012-09-20, S/N 2203, built 1957 (OpenAirDocs) - Reported make and model: Bell 47G-B3 - Registry model: [Bell 47G-3B](https://openairdocs.org/model/bell-47g-3b) (registry code 1181026) (OpenAirDocs) - Registry engine: [Lycoming TVO-435-GIA](https://openairdocs.org/engine/lycoming-tvo-435-gia) (registry code 41526, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 2203 - Airframe hours: 13957 - Engines: Allison T63-700 318 horsepower turbo shaft - Damage: Substantial damage - Flight: Part 91 - Registered owner: Precision Air Svcs., Inc. - Airworthiness certificate: Standard, Normal; Special, Restricted (Special) - Last inspection: Annual, March 25, 1999, 72 hours before - Airport: SEM, Craig Field ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 11,000 total, 500 in this make and model, 11,000 as pilot in command, 25 in the last 90 days, 8 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 260° at 6 knots - Visibility: 6 statute miles - Lowest ceiling: none - Temperature: 102 °F, dew point 75 °F - Altimeter: 29.00 inHg - Observed at: MGM, 50 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 19990808011249A](https://openairdocs.org/incident/19990808011249A), Aug 8, 1999: Bell 47G3B, Selma, AL, Substantial damage. 1957 Bell 47G-3B helicopter was attempting to land on a trailer, one skid did not get onto the trailer, and the acft flipped over. (.4)after a test flight… ## Other investigations on N6712D (5) 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. - [NTSB SEA79DYP14](https://openairdocs.org/ntsb/SEA79DYP14), Apr 26, 1979: Bell 47G-3B (N6712D), Wenatchee, WA, substantial damage - [NTSB SEA76DYG74](https://openairdocs.org/ntsb/SEA76DYG74), Sep 15, 1976: Bell 47G-3B (N6712D), Cashmere, WA, substantial damage - [NTSB SEA72DYG40](https://openairdocs.org/ntsb/SEA72DYG40), May 26, 1972: Bell 47G2 (N6712D), Moses Lake, WA, destroyed - [NTSB SEA69D0183](https://openairdocs.org/ntsb/SEA69D0183), Feb 14, 1969: Bell 47G-2 (N6712D), Chelan, WA, substantial damage - [NTSB UNK65X0536](https://openairdocs.org/ntsb/UNK65X0536), Nov 2, 1964: Bell 47G2 (N6712D), Yuma, AZ, substantial damage 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.