# NTSB LAX04LA171: Maule M-7-260C, N99KJ, Paso Robles, CA, March 28, 2004 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 28, 2004, 11:34 local (19:34 UTC) - Place: Paso Robles, CA - Coordinates: 35.567501, -120.791664 - Nearby events: https://openairdocs.org/map.md?lat=35.5675&lon=-120.7917&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report July 7, 2005 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 58974 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX04LA171 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/58974/pdf - Page: https://openairdocs.org/ntsb/LAX04LA171 ## Probable cause fuel system vapor lock due to the failure of the left exhaust stack clamp pin, which caused a separation of the exhaust stack from the muffler and the porting of hot exhaust gases onto the fuel lines. ## 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, takeoff - initial climb - exhaust system,clamp - failure (cause) - exhaust system,stack - disconnected (cause) - fuel system,line - overtemperature (cause) - fuel system - vapor lock (cause) - Forced landing, emergency landing after takeoff - In flight collision with terrain/water, emergency landing after takeoff - terrain condition - ground (contributing factor) ## Analysis The airplane lost engine power during takeoff from a private airstrip and collided with the ground during the ensuing forced landing attempt. During the initial takeoff climb, approximately 1,000 feet above ground level, the engine sputtered. The pilot changed the fuel tank selector from the "BOTH" position to the "RIGHT" position and adjusted the mixture control. Partial power returned momentarily; shortly thereafter, the engine lost power again. During the forced landing on uneven terrain, the right wing impacted the ground. Post-accident examination revealed that the left muffler's exhaust stack was detached from the manifold. The exhaust stack is secured to the exhaust manifold outlet tube with a pin. This pin was eroded and no longer secured the two pieces together. Evidence of heat was found on the fuel lines and plastic tubing in the area of the exhaust stack. According to the AC 65-12A, vapor lock can be induced by high fuel temperatures and result in a partial or complete loss of power. A post-accident test run of the engine did not reveal any operating anomalies or malfunctions. ## Factual narrative On March 28, 2004, at 1134 Pacific standard time, a Maule M-7-260C, N99KJ, lost engine power during takeoff from a private airstrip near Paso Robles, California. The airplane collided with the ground during the ensuing forced landing attempt. The pilot, the registered owner, was operating the airplane under the provisions of 14 CFR Part 91. The private pilot and one passenger were not injured. The airplane sustained substantial damage. Visual meteorological conditions prevailed, and no flight plan had been filed. The personal flight was en route to Santa Barbara, California. According to the pilot, the taxi and run-up were normal. During the initial takeoff climb, approximately 1,000 feet above ground level (agl), the engine sputtered. The pilot changed the fuel tank selector from the "BOTH" position to the "RIGHT" position and adjusted the mixture control. Partial power returned momentarily; shortly thereafter, the airplane impacted the ground. During the forced landing on uneven terrain, the right wing impacted the ground. Each of the main tanks contained about 11 gallons; the total fuel capacity for each tank is 21.5 gallons. The National Transportation Safety Board investigator-in-charge examined the airplane on April 19, 2004 at Plain Parts, Pleasant Grove, California. The top spark plugs were removed and displayed normal operating signatures when compared to the Champion Check-A-Plug Chart AV-27. The left exhaust stack was detached from the left exhaust manifold. The clamp that secured the exhaust manifold to the exhaust stack remained attached to the exhaust stack. Removal of the clamp revealed that the pin which secures the exhaust stack to the manifold was worn and no longer held the two pieces together. The right exaust stack clamp was removed. The securing pin had a tapered appearance. The pin, by installation, is positioned in the flow of exhaust gases. An insulating sleeve covering the fuel line to the electric fuel pump was gray in color and partially melted. Spiral plastic tubing that covered cables was also melted. The following day, the engine was test run using an external fuel supply. No operating anomalies or malfunctions were noted. According to the airplane manufacturer, the pin is 1/4-inch diameter and not tapered. The exhaust stack to the muffler, by design, is attached to the exhuast manifold outlet tube using a "U" clamp and pin. The pin engages matching holes in the exhaust manifold outlet tube and the exhaust stack. In the event of a pin failure, the exhaust stack will no longer be secured to the manifold. The maintenance manual for the airplane states, "Note that the tail pipe [exhaust stack] clamps and the muffler-to-header attachments should not be tightened to the point of rigidity, but should be loose enough to be moved easily by hand." Vapor lock is defined in the Airframe and Powerplant Mechanics Handbook (AC 65-12A) as a partial or complete interruption of fuel flow. This results in vapor pockets from the premature vaporization of fuel restricting fuel flow through units that are designed to handle liquids rather than gases. The three general causes of vapor lock are the lowering of the pressure on the fuel, high fuel temperatures, and excessive fuel turbulence. ## Aircraft - Registration: [N99KJ](https://openairdocs.org/aircraft/N99KJ), registered now, S/N 30009C (OpenAirDocs) - Reported make and model: Maule M-7-260C - Registry model: [Maule M-7-260C](https://openairdocs.org/model/maule-m-7-260c) (registry code 5470112) (OpenAirDocs) - Category: Airplane - Serial number: 30009C - Airframe hours: 836 - Engines: Lycoming IO-540 270 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: John Graves - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 3, 2003, 60 hours before - Departed: Paso Robles, CA - Destination: SBA, Santa Barbara, CA - Airport: Private ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 64; injuries: none; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; last flight review August 4, 2002; seat: left; flight hours: 4,500 total, 800 in this make and model, 4,500 as pilot in command, 38 in the last 90 days, 15 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 63 °F, dew point 43 °F - Altimeter: 30.22 inHg - Observed at: KPRB, 6 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 20040328006549A](https://openairdocs.org/incident/20040328006549A), Mar 28, 2004: Maule M7260C, Crestin, CA, Substantial damage. (-23) The pilot stated that the engine lost power during take off from a Private airfield near paso robles, California. According to the pilot the taxi and… 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.