# NTSB ANC11FA093: Piper PA-18-150, N13973, McGrath, AK, September 4, 2011 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Field investigation · Final report - Date: September 4, 2011, 15:00 local (23:00 UTC) - Place: McGrath, AK - Coordinates: 62.952777, -155.606948 - Nearby events: https://openairdocs.org/map.md?lat=62.9528&lon=-155.6069&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern final: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report December 19, 2012 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: FAA FSDO-01 - NTSB case key (mKey): 81693 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC11FA093 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81693/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81693 - Page: https://openairdocs.org/ntsb/ANC11FA093 ## Probable cause The pilot inadvertently switched off the engine magnetos during short final approach, which resulted in a loss of engine power. Contributing to the accident was the manufacturer's placement of the magneto switches in the cabin. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Use of equip/info](https://openairdocs.org/ntsb-findings/02063000): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Piper PA-18-150, 3 cases](https://openairdocs.org/ntsb-findings/02063000/cases.md?model=7101828), [All aircraft, 111 cases](https://openairdocs.org/ntsb-findings/02063000/cases.md) - [Ignition system: switching](https://openairdocs.org/ntsb-findings/01057430): Aircraft › Aircraft power plant · Unintentional use/operation (probable cause); cases with it: [Piper PA-18-150, 2 cases](https://openairdocs.org/ntsb-findings/01057430/cases.md?model=7101828), [All aircraft, 9 cases](https://openairdocs.org/ntsb-findings/01057430/cases.md) - [Physical workspace: positioning/available space](https://openairdocs.org/ntsb-findings/03041010): Environmental issues › Task environment · Contributed to outcome (probable cause); cases with it: [Piper PA-18-150, 2 cases](https://openairdocs.org/ntsb-findings/03041010/cases.md?model=7101828), [All aircraft, 11 cases](https://openairdocs.org/ntsb-findings/03041010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern final: Engine shutdown](https://openairdocs.org/ntsb-events/140); cases with it: [Piper PA-18-150, 2 cases](https://openairdocs.org/ntsb-events/140/sequence.md?model=7101828), [All aircraft, 80 cases](https://openairdocs.org/ntsb-events/140/sequence.md) - [Approach-VFR pattern final: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Piper PA-18-150, 18 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=7101828), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Piper PA-18-150, 115 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=7101828), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The airplane was on short final approach to the airport when its engine would not respond to throttle input. The airplane descended into trees and impacted terrain. The pilot reported that immediately prior to the loss of engine power, he had made an elevator trim control adjustment and was in the process of making a throttle adjustment when he heard a snap and the engine quit operating, "as if the magnetos had been shut off." Examination of the airplane established that the throttle cable was intact. The engine was run, and no anomalies were noted. During the engine run, the magneto switches were turned off while the engine was at cruise rpm. The switches made an audible click/snap when turned off. Following a similar August 29, 2011, accident also involving a Piper PA-18 airplane, the pilot reported that, during the initial climb, he inadvertently switched off the engine magnetos with his coat sleeve while using the trim handle, causing the airplane’s engine to shut down. As with this accident airplane, the magneto switches were located on the left side of the cabin, just above the trim handle. As a result of incidents involving the inadvertent shutting off of the magneto switches, the Federal Aviation Administration published a notice of proposed rulemaking announcing its intent to issue an airworthiness directive requiring the reconfiguration of the magneto switches on Piper PA-18 airplanes. Given the absence of any mechanical issues with the airplane, as well as the location of the magneto switches and the trim handle, it is likely the pilot inadvertently shut off the magnetos switches while trimming the airplane on short final approach. ## Factual narrative On September 4, 2011, about 1500 Alaska daylight time, a Piper PA-18 airplane, N13973, sustained substantial damage following a loss of engine power during final approach to McGrath Airport, McGrath, Alaska. The airplane was operated by the pilot as a visual flight rules (VFR) personal cross-country flight, under the provisions of 14 Code of Federal Regulations, Part 91, when the accident occurred. Visual meteorological conditions prevailed at the time of the accident, and the solo commercial pilot received serious injuries. The flight departed Kingston Creek, about 85 miles east of McGrath. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on September 4, a rescuer that responded to the accident site said that the pilot told him that while on approach to land, he advanced the throttle to apply engine power to adjust his glide path, but the engine did not respond. The pilot reported that he thought the throttle cable had broken. The airplane subsequently descended into trees at the approach end of the runway, sustaining substantial damage to the wings and fuselage. Additionally, the pilot told the rescuer that he heard an audible snap, which made him think the throttle cable had snapped, and then the engine failed to respond to throttle application. During a telephone conversation with the NTSB IIC in January 2012, the pilot reported that he had owned the airplane for many years, and that there were no mechanical anomalies with the airplane prior to the accident. He said that on the accident flight, while on short final for the airport, the airplane had been trimmed for the approach, and the engine was throttled back. He said the approach was going to be short of the runway, and he applied power, but the airplane engine remained at idle. He thought the throttle cable had broken. The airplane descended striking trees and the ground, and nosed over. During recovery of the airplane, usable amounts of fuel were found in the wing tanks. The wings were removed and the airplane was transported to a maintenance facility in Anchorage, Alaska. On November 10, the airplane was examined by the NTSB IIC, accompanied by an FAA air safety inspector. During the inspection the engine was run on the airframe. The engine was started, and run through various rpm ranges. The throttle cable was found intact and it worked as anticipated. No mechanical anomalies were found with the engine. An FAA air safety inspector, a party to the investigation, said the pilot made the following statement during a telephone interview. On September 4, 2011, the accident pilot said that immediately prior to the loss of engine power, he had made elevator trim control adjustments and was in the process of making a throttle control adjustment when he heard a snap and the engine quit operating, “as if the magnetos had been shut off.“ The elevator trim adjustment handle is situated just below the magneto toggle switches. Duringthe engine run, the magneto switches were turned off while the engine was at cruise rpm. The switches being single-pole, single-throw mechanical switches, made an audible click/snap when turned off, which could be heard above the noise of the engine. Due to the pilot's injuries, no NTSB form 6120.1 was submitted. Airplane and pilot log books were examined, and no anomalies were found. Additional Information In a similar accident also involving a Piper PA-18 airplane, which occurred on August 29, 2011, near Cape Yakataga, Alaska, (ANC11CA089) the pilot reported that, during the initial climb, he inadvertently switched off the engine magnetos with his coat sleeve while using the trim handle causing the airplane’s engine to shut down; the switches were located on the left side of the cabin. The pilot realized the problem, but, due to the airplane's low altitude, he decided to land instead of trying to restart the engine. A postaccident examination of the magneto switches on the accident airplane, and other like models, revealed that a pilot's coat sleeve can contact and move the guarded magneto switches to the off position. As a result of the previous investigation the NTSB determined that the pilot inadvertently switched off the engine magnetos during the initial climb, resulting in a loss of engine power. Contributing to the accident was the manufacturer's placement of the magneto switches. The airplane in the current accident had the same magneto switch configuration as the airplane listed in ANC11CA089, and the pilot had just trimmed the airplane for the approach. Following the investigation of ANC11CA089, the FAA looked into instances of magnetos being inadvertently shut off in similarly configured airplanes. Their investigation led to publishing a notice of proposed rulemaking (NPRM), with the intent to publish an airworthiness directive (AD) for the reconfiguration of the magneto switches. ## Aircraft - Registration: [N13973](https://openairdocs.org/aircraft/N13973), registered now, S/N 18-8985, built 1972 (OpenAirDocs) - Reported make and model: PIPER PA-18-150 - Registry model: [Piper PA-18-150](https://openairdocs.org/model/piper-pa-18-150) (registry code 7101828) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 18-8985 - Airframe hours: 1364 - Engines: LYCOMING O-360 SERIES 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Richardson James K - Registered owner: Richardson James K - Airworthiness certificate: Standard, Normal - Departed: Kingston Creek, AK - Destination: PAMC, McGrath, AK - Flight plan: Unknown - Airport: PAMC, McGrath, runway 05, 2,000 × 60 ft, gravel ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; injuries: serious; commercial; airplane ratings: single-engine land, single-engine sea, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; seat: front; flight hours: 23,000 total, 6,000 in this make and model, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: 20,000 ft broken - Temperature: 61 °F, dew point 48 °F - Altimeter: 29.26 inHg - Observed at: PAMG, 1 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 20110904021679A](https://openairdocs.org/incident/20110904021679A), Sep 4, 2011: Piper PA-18-150, Mcgrath, AK, Substantial damage. On September 4, 2011, at about 1515 Alaska daylight time, a Piper PA-18 airplane, N13973, sustained substantial damage when its engine lost power, and it… ## Other investigations on N13973 (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 ANC78FA034](https://openairdocs.org/ntsb/ANC78FA034), Apr 30, 1978: Piper PA-18 (N13973), Homer, AK, substantial damage, 1 fatal ## Docket (2 files) The files NTSB released with the investigation on October 27, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81693. 2.3 MB in all. - Photo 1. Magneto switch configuration and relative position to the trim wheel. (item 1, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40378879&FileExtension=.PDF&FileName=Photo%201.%20Magneto%20switch%20configuration%20and%20relative%20position%20to%20the%20trim%20wheel.-Master.PDF - Photo 2. Side view of the magneto switches, and switch guards. (item 2, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40378880&FileExtension=.PDF&FileName=Photo%202.%20Side%20view%20of%20the%20magneto%20switches,%20and%20switch%20guards.-Master.PDF 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.