# NTSB SEA98LA192: Mayala Dragonfly, N4478V, Avon, MT, September 30, 1998 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: September 30, 1998, 09:45 local (15:45 UTC) - Place: Avon, MT - Coordinates: 46.650657, -112.600593 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=46.6507&lon=-112.6006&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report January 11, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 44066 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA98LA192 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/44066/pdf - Page: https://openairdocs.org/ntsb/SEA98LA192 ## Probable cause Failure of the engine crankshaft aft oil seal resulting in the loss of engine oil, and rough terrain during the forced landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, cruise - lubricating system,oil seal - failure (cause) - fluid,oil - loss,total (cause) - Forced landing, descent - emergency - Loss of control - on ground/water, landing - roll - terrain condition - rough/uneven (cause) - In flight collision with terrain/water, descent - uncontrolled ## Analysis The pilot-in-command/owner of the homebuilt Volkswagen-engine powered Dragonfly departed Helena, Montana, uneventfully. After approximately 30 minutes of flight he observed the engine oil pressure decrease to zero in less than two minutes with a concurrent increase in oil temperature. He then executed a forced landing in a rough pasture during which the aircraft bounced and then cartwheeled. Post-crash examination revealed oil on the aircraft's firewall and underside. Further examination revealed that the engine rear crankshaft seal was deformed and the neoprene gasket was missing. ## Factual narrative On September 30, 1998, approximately 0945 mountain daylight time, a homebuilt Mayala Dragonfly, N4478V, registered to and being flown by a private pilot, was destroyed during an emergency landing approximately one mile north of Avon, Montana. The pilot sustained minor injuries. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was to have been operated under 14CFR91, and originated from the Helena Regional airport, Helena, Montana, approximately 0915. The pilot reported that the takeoff, climb-out and level off were normal but that "about 25 min[utes] into [the] flight, [the] oil pressure started down. It went to zero in a minute or 2" and that "the oil temp went up." The pilot initially evaluated and then discarded landing on highway 2 due to numerous vehicles and multiple wires crossing the highway. He then maneuvered to land on highway 141 but determined that once again power lines interfered with a landing along with a curve in the highway. He then elected to land in a pasture. The pilot reported that the pasture was rough, and that during touch-down "the right main hit a (hole, ditch?) bounced up & the canard (left) hit the ground & started the craft to cartwheel" (refer to CHART I). On site examination by an FAA inspector revealed a considerable amount of oil on the aircraft's belly, but little if any on the windscreen. The firewall was covered with oil, and the engine sump oil drain plug was observed in place. The pilot/owner reported that the aircraft's Volkswagen engine rear crankshaft seal "chunked and rolled up," that the "neoprene part [was] gone," and that "all [the] oil [was] pumped out during the 30 min[ute] flight." ## Aircraft - Registration: [N4478V](https://openairdocs.org/deregistered/N4478V-2013-06-11), registration cancelled 2013-06-11, S/N 437, built 1985 (OpenAirDocs) - Reported make and model: Mayala DRAGONFLY - Registry model: [Mayala Hjalmer A DRAGONFLY](https://openairdocs.org/model/mayala-hjalmer-a-dragonfly) (registry code 05644HV) (OpenAirDocs) - Registry engine: [Volkswagen CONVERSION](https://openairdocs.org/engine/volkswagen-conversion) (registry code 63501, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 437 - Airframe hours: 988 - Engines: Volkswagen 70 horsepower reciprocating - Damage: Destroyed - Flight: Personal, Part 91 - Registered owner: Mayala, Hjalmer, A. - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, March 4, 1998, 41 hours before - Departed: HLN, HELENA, MT ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 58; private; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 1,170 total, 850 in this make and model, 1,120 as pilot in command, 40 in the last 90 days, 15 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: 4,000 ft overcast - Temperature: 48 °F, dew point 39 °F - Altimeter: 30.00 inHg - Observed at: HLN, 25 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 19980930027299A](https://openairdocs.org/incident/19980930027299A), Sep 30, 1998: Amtr DRAGONFLY, Avon, MT, Substantial damage. (-23) Aircraft sustained substantial damage during emergency landing in a field approx. 3 miles north of Avon, Montana. Pilot stated to sheriff scott howard… ## Other investigations on N4478V (1) 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 DEN86LA236](https://openairdocs.org/ntsb/DEN86LA236), Aug 25, 1986: Mayala Dragonfly (N4478V), Helena, MT, 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.