# NTSB CEN15IA230: Cessna 152, N49158, Pilot Point, TX, April 30, 2015 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: April 30, 2015, 11:15 local (16:15 UTC) - Place: Pilot Point, TX - Coordinates: 33.379165, -95.937225 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.3792&lon=-95.9372&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report April 26, 2016 - Report: Approved by Office Director - NTSB office: Central Region - NTSB case key (mKey): 91164 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN15IA230 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/91164/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=91164 - Page: https://openairdocs.org/ntsb/CEN15IA230 ## Probable cause The loss of engine power due to the separation of the distributor gear arm on the left magneto. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Ignition system: magneto/distributor](https://openairdocs.org/ntsb-findings/01057414): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Cessna 152, 4 cases](https://openairdocs.org/ntsb-findings/01057414/cases.md?model=2071835), [All aircraft, 101 cases](https://openairdocs.org/ntsb-findings/01057414/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Cessna 152, 6 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=2071835), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Maneuvering: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342); cases with it: [Cessna 152, 21 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=2071835), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Cessna 152, 35 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=2071835), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The flight instructor and student pilot were conducting a training flight. After the student completed some maneuvers, the engine started running roughly. The flight instructor made several attempts to correct the problem without success. The airplane was unable to maintain altitude, so the flight instructor performed a forced landing to a field, which resulted in minor damage to the airplane. An examination of the engine revealed that the Nos. 2 and 4 lower sparkplugs were lead-fouled and inoperative and that the Nos. 1 and 3 lower sparkplugs were lead-fouled but still operational. Further examination revealed that the distributor gear arm on the left magneto had separated and that the distributor gear arm on the right magneto was loose. Following the incident, the operator examined its fleet and found an additional 19 magnetos with loose distributor gear arms. The magneto manufacturer reported that it had seen 16 magnetos that exhibited similar failures. The manufacturer subsequently issued a service bulletin recommending that distributor gear assemblies in the affected magneto, which included the incident magneto, be removed and replaced at the "earliest convenient maintenance time, not to exceed the next 50 hours" with a replacement gear assembly. ## Factual narrative On April 30, 2015, about 1115 central daylight time, a Cessna 152 airplane, N49158, sustained minor damage during a forced landing near Pilot Point, Texas. The flight instructor and student pilot were not injured. Visual meteorological conditions prevailed at the time of the incident. The instructional flight was operated by U.S. Aviation Group, LLC., under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. The local flight departed Denton Enterprise Airport (KDTO), Denton, Texas, about 1100. The student had just completed steep turns when the engine started running rough; however, the roughness soon stopped. Following another steep turn, the engine started running rough again. The flight instructor went through several procedures and checklists to troubleshoot or diagnose the engine roughness including a magneto check. The rpms fluctuated between 1,200 and 2,000 and the flight instructor was unable to maintain altitude or correct the rough-running engine. He elected to land in a nearby field which resulted in minor damage to the nose landing gear and engine mount. An examination of the engine revealed that the number 2 and number 4 lower sparkplugs were lead-fouled and inoperative and the number 1 and number 3 lower sparkplugs were lead-fouled but still operational. Further examination revealed that the distributor gear finger (part number 510406) on the left magneto (Slick Magneto, serial number 14040289/model number 4381) separated. The distributor gear finger (510406) on the right magneto (Slick Magneto, serial number 14040835/model number 4381) was loose. The magnetos had 478.8 hours total time. Following the incident, U.S. Aviation Group, LLC., examined the remainder of their fleet and discovered an additional 19 magnetos with loose distributor gear fingers. The model numbers were 4381 (same as the incident magnetos), 4370, 4371, 4372, and 4374. Total time on these magnetos varied from 48 hours to 2,168.5 hours. These magnetos were installed new at engine overhaul or as a replacement during maintenance. The Director of Maintenance at U.S. Aviation Group LLC. commented that the method of attaching the finger to the gear was different than in the past. According to the manufacturer, Slick by Champion Aerospace, they had seen 16 magnetos that exhibited similar failure modes: 9 with the separation of the distributor finger and 7 with loose fingers. They added that there was no design change. Controls used in the insertion of the finger into the gear and an additional inspection of this procedure had since been added. On July 2, 2015, Slick by Champion Aerospace issued Service Bulletin 1-15. This service bulletin called for the distributor gear assembly to be removed and replaced on certain Slick Magnetos, at the "earliest convenient maintenance time, not to exceed the next 50 hours." The magnetos involved in this incident were included in the models affected outlined in the service bulletin. ## Aircraft - Registration: [N49158](https://openairdocs.org/deregistered/N49158-2019-12-16), registration cancelled 2019-12-16, S/N 15281171, built 1977 (OpenAirDocs) - Reported make and model: CESSNA 152 - Registry model: [Cessna 152](https://openairdocs.org/model/cessna-152) (registry code 2071835) (OpenAirDocs) - Registry engine: [Lycoming 0-235 series](https://openairdocs.org/engine/lycoming-0-235-series) (registry code 41505, 4 cycle) (OpenAirDocs) - Category: Airplane - Serial number: 15281171 - Year built: 1977 - Airframe hours: 10204 - Engines: LYCOMING O-235-L2C 115 horsepower reciprocating - Damage: Minor damage - Flight: Instructional, Part 91 - Operator: US Aviation Group LLC - Registered owner: US Aviation Group LLC - Airworthiness certificate: Standard, Utility; Standard, Normal - Last inspection: 100 hour, March 25, 2015 - Departed: KDTO, Denton, TX - Destination: KDTO, Denton, TX - Equipment: Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Student pilot; age 24; injuries: none; student; medical: class 1, without waivers/limitations; seat: left; restraint: 3-point; flight hours: 39 total, 39 in this make and model, 22 in the last 90 days, 6 in the last 30 days, 1 in the last 24 hours - Flight instructor; age 20; injuries: none; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review February 28, 2014; seat: right; restraint: 3-point; flight hours: 1,229 total, 262 in the last 90 days, 84 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 54 °F - Altimeter: 30.02 inHg - Observed at: KDTO ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 20150430005559I](https://openairdocs.org/incident/20150430005559I), Apr 30, 2015: Cessna 152, Pilot Point, TX, Minor damage. The certified flight instructor (CFI) was providing basic flight instruction to his student at 3300 feet, MSL. The engine experienced roughness following a… ## Docket (4 files) The files NTSB released with the investigation on March 9, 2016, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=91164. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 984 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437523&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - US Aviation Magneto Failure Documents (item 2, .PDF, 3.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437524&FileExtension=.PDF&FileName=US%20Aviation%20Magneto%20Failure%20Documents-Master.PDF - Record of Conversation - Manufacturer (item 3, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437525&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Manufacturer-Master.PDF - Slick Service Bulletin (item 4, .PDF): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40437526&FileExtension=.PDF&FileName=Slick%20Service%20Bulletin-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.