# NTSB MIA99LA191: Mooney M20F, N7114V, Liberty, NC, June 29, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 29, 1999, 12:40 local (16:40 UTC) - Place: Liberty, NC - Coordinates: 35.849601, -79.569396 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.8496&lon=-79.5694&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report March 2, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 46686 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA99LA191 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46686/pdf - Page: https://openairdocs.org/ntsb/MIA99LA191 ## Probable cause Improper inspection of the muffler assembly resulting in erosion going undetected and the rupture of the muffler and shroud while in cruise flight. The condition caused melting of portions of the air induction system, loss of engine power, and the pilot's attempted forced landing that resulted in collision with terrain that sheared one main landing gear and fractured the wheel of the other main landing gear. A factor in the accident was the pilot's obscured vision due to smoke in the cockpit. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - exhaust system,muffler - ruptured - maintenance,inspection - inadequate, other maintenance personnel (cause) - Loss of engine power(total) - mech failure/malf, cruise - induction air ducting - burned (contributing factor) - Forced landing, emergency descent/landing - fuselage,crew compartment - smoke - In flight collision with terrain/water, emergency landing ## Analysis The flight was in cruise at 6,500 feet msl, when the engine started to run rough. Two to three minutes later the engine stopped operating, and the pilot requested vectors to the nearest airport. While setting himself up for a forced landing, the cabin filled with smoke, and the pilot cracked open the cabin door to evacuate the smoke. The airplane touched down short of the runway and sustained main landing gear damage. Postcrash examination revealed muffler and muffler shroud breaching that allowed engine exhaust to impinge on and burn components of the nose landing gear, the air induction system, and the lower fuselage. NTSB Materials Laboratory examination revealed the muffler failed due to scaling and intergranular attack occurring over a period of time that would have been evident 30 flight hours previous when the airplane underwent an annual inspection. ## Factual narrative On June 29, 1999, about 1240 eastern daylight time, a Mooney M20F, N7114V, registered to a private individual, operating as a Title 14 CFR Part 91 personal flight, crashed short of the runway at Causey Airport, Liberty, North Carolina. The pilot was attempting a forced landing following an in-flight engine failure and subsequent smoke in the cabin. Visual meteorological conditions prevailed and no flight plan was filed. The airplane sustained substantial damage and the private-rated pilot, the sole occupant, was not injured. The flight originated from Newport News, Virginia, about 1 hour 10 minutes before the accident. According to the pilot, he was in cruise flight at 6,500 feet msl, when he heard the engine start to run rough. Two to 3 minutes later, the engine stopped altogether, and he steered toward the Causey Airport for a forced landing. He was in the landing pattern when the cabin filled with smoke. He touched down short of the runway into rough terrain, causing damage to the landing gear. In follow-up phone conversation, he stated he does not remember hearing any unusual engine noises during start or en route, nor does he remember any increase of level of exhaust noise. He did say, however, that he uses noise attenuating earphones that are very effective. According to an FAA inspector, the airplane touched down 300 feet short of the runway and hit a berm, shearing the right main landing gear assembly and fracturing the left wheel at the axle. Postcrash examination revealed that in addition to the main gear damage, the nose tire was burned and deflated, and the fuselage bottom aft of the firewall was heat stressed and cracked. The muffler shroud had a 2 x 3 inch hole and the muffler had a 4 x 4 inch hole blown out of their respective side walls and welded seams. Portions of the lower plenum/air induction system were melted. The muffler and shroud were shipped to the NTSB Materials Laboratory for failure analysis examination. The muffler walls revealed scaling and intergranular attack that eventually became cracks, and in the case of the perforated inlet pipes, disintegration. This allowed the undiffused exhaust gases to directly impinge on the muffler walls, accelerating the aging process. The Mooney M20 Series Service and Maintenance Manual and 100-Hour Annual Inspection Guide state that the exhaust heater shroud should be removed and inspected and the muffler inspected for corrosion, fatigue and/or welding cracks, and any other apparent damage during annual inspections. According to airplane maintenance records, this engine and airframe underwent an annual inspection on January 21, 1999, and had accumulated 30 hours since the inspection. ## Aircraft - Registration: [N7114V](https://openairdocs.org/aircraft/N7114V), registered now, S/N 22-0049, built 1974 (OpenAirDocs) - Reported make and model: Mooney M20F - Registry model: [Mooney M20F](https://openairdocs.org/model/mooney-m20f) (registry code 5870214) (OpenAirDocs) - Registry engine: [Lycoming I0360 series](https://openairdocs.org/engine/lycoming-i0360-series) (registry code 41515, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 220049 - Airframe hours: 2128 - Engines: Lycoming IO360 A1A 200 horsepower reciprocating - Damage: Substantial damage - Fire: In-Flight - Flight: Personal, Part 91 - Registered owner: Thomas S. Wilson - Airworthiness certificate: Standard, Normal - Last inspection: Annual, January 21, 1999, 30 hours before - Departed: PHF, NEWPORT NEWS, VA - Destination: 14A, MOORESVILLE, NC - Airport: 2A5, Causey Airport, runway 20, 3,002 × 40 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; private; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 3,554 total, 29 in this make and model, 3,439 as pilot in command, 119 in the last 90 days, 52 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 82 °F, dew point 75 °F - Altimeter: 29.00 inHg - Observed at: BUY, 13 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 19990629022399A](https://openairdocs.org/incident/19990629022399A), Jun 29, 1999: Mooney M20F, Liberty, NC, Substantial damage. (.19) On June 29, 1999, bout 1240 eastern daylight time, a Mooney M20F, N7114V, registered to a private individual, operating as a title 14 CFR part 91… 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.