# NTSB CEN13LA305: Stinson 108-3, N121CM, Beaumont, TX, May 23, 2013 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: May 23, 2013, 12:00 local (17:00 UTC) - Place: Beaumont, TX - Coordinates: 30.070278, -94.214996 - Nearby events: https://openairdocs.org/map.md?lat=30.0703&lon=-94.2150&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-climb to cruise: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report February 10, 2014 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA-Houston FSDO - NTSB case key (mKey): 87017 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN13LA305 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/87017/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=87017 - Page: https://openairdocs.org/ntsb/CEN13LA305 ## Probable cause The lack of a forward clamp on the carburetor heat box rubber boot, which allowed the boot to be ingested into the inlet of the carburetor heat box, restricting the airflow and leading to a subsequent partial loss of engine power. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Power plant: air intake](https://openairdocs.org/ntsb-findings/01057160): Aircraft › Aircraft power plant · Damaged/degraded (probable cause); cases with it: [Stinson 108-3, 1 case](https://openairdocs.org/ntsb-findings/01057160/cases.md?model=9230408), [All aircraft, 50 cases](https://openairdocs.org/ntsb-findings/01057160/cases.md) - [Power plant: air intake](https://openairdocs.org/ntsb-findings/01057160): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Stinson 108-3, 1 case](https://openairdocs.org/ntsb-findings/01057160/cases.md?model=9230408), [All aircraft, 50 cases](https://openairdocs.org/ntsb-findings/01057160/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Stinson 108-3, 3 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=9230408), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-climb to cruise: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Stinson 108-3, 6 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=9230408), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Stinson 108-3, 15 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=9230408), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) - [Landing: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [Stinson 108-3, 13 cases](https://openairdocs.org/ntsb-events/096/sequence.md?model=9230408), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md) ## Analysis The pilot reported that the airplane's engine lost partial power shortly after takeoff. The airplane was unable to maintain altitude, so he executed a forced landing to a field, and the airplane nosed over. Postaccident examination revealed that the rubber boot between the carburetor heat box and cowl was missing its forward clamp, which was not found in the wreckage The clamp was likely missing because an improper clamp was used or a clamp was not installed properly, which allowed the boot to come loose and to be ingested into the inlet of the carburetor heat box, restricting the airflow and resulting in a rich fuel mixture and the subsequent partial loss of engine power. No other anomalies were found with the engine or its systems. ## Factual narrative On May 23, 2013, about 1200 central daylight time, a Stinson 108-3, N121CM, sustained substantial damage when it nosed over during a forced landing following a loss of engine power near Beaumont, Texas. The pilot received minor injuries. The airplane sustained damage to the vertical tail surfaces, wings, wing struts, and fuselage. The aircraft was registered to and operated by Aircapital Nevada, Inc., under the provisions of 14 Code of Federal Regulations Part 91 as a business flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The flight was originating from the Beaumont Municipal Airport, Beaumont, Texas, and was bound for College Station, Texas.The pilot reported that he had performed a pre-takeoff run-up and all engine indications were normal. He proceeded to take off and made two 90-degree turns prior to the loss of engine power. The pilot said that the engine was still producing some power, but he was not able to maintain altitude. He attempted to land in a field and the airplane nosed over. Examination of the engine confirmed compression on all cylinders, valve system continuity, and magneto operation. The carburetor appeared new and the fuel strainer was clean with no debris. The fuel within the gascolator did not appear to have any water or sediment. The upper spark plugs were of three different electrode configurations. All of the plugs exhibited a wet-black appearance. The rubber boot that was located between the carburetor heat box and the cowl was very pliable and had cracks on the exterior surfaces. The rear of the boot was attached to the carburetor heat box with a clamp and sealant. The front of the boot did not have a clamp installed and one was not found in the wreckage. Discussions with a member of the International Stinson Club (ISC) revealed that the front of the boot between the carburetor heat box and the cowl should have had a 2-piece clamp installed. The ISC member said that without the clamp installed it is possible for the boot to be sucked into the inlet of the carburetor heat box thereby restricting airflow, resulting in a rich mixture and reduction of engine power. ## Aircraft - Registration: [N121CM](https://openairdocs.org/deregistered/N121CM-2018-05-30), registration cancelled 2018-05-30, S/N 108-4284, built 1948 (OpenAirDocs) - Reported make and model: STINSON 108-3 - Registry model: [Stinson 108-3](https://openairdocs.org/model/stinson-108-3) (registry code 9230408) (OpenAirDocs) - Registry engine: [Franklin 6A4165 series](https://openairdocs.org/engine/franklin-6a4165-series) (registry code 27025, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 108-4284 - Engines: FRANKLIN 6A4165 SERIES 165 horsepower reciprocating - Damage: Substantial damage - Flight: Business, Part 91 - Operator: Aircapital Nevada Inc - Registered owner: Aircapital Nevada Inc - Airworthiness certificate: Standard, Normal - Departed: BMT, Beaumont, TX - Destination: CLL, College Station, TX - Flight plan: Unknown - Airport: BMT, Beaumont Municipal Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 81; injuries: minor; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; seat: left ## Weather - Conditions: Visual (VMC), Day - Wind: 190° at 8 knots - Visibility: 10 statute miles - Lowest ceiling: 3,000 ft broken - Temperature: 84 °F, dew point 73 °F - Altimeter: 30.03 inHg - Observed at: BMT ## 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 20130523008509A](https://openairdocs.org/incident/20130523008509A), May 23, 2013: Stinson 108-3, Beaumont, TX, Substantial damage. Aircraft took off on runway 13 for a cross country ferry flight at approximately 1200 noon on Thursday 05/23/2013. PIC stated once airborne the engine began… ## Docket (3 files) The files NTSB released with the investigation on December 9, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=87017. 888 KB in all. - Wreckage Examination Notes (item 1, .PDF, 7 photos, 782 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399347&FileExtension=.PDF&FileName=Wreckage%20Examination%20Notes-Master.PDF - Record of Cconversation with Pilot (item 2, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399348&FileExtension=.PDF&FileName=Record%20of%20Cconversation%20with%20Pilot-Master.PDF - Record of Conversation with International Stinson Club Member (item 3, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399350&FileExtension=.PDF&FileName=Record%20of%20Conversation%20with%20International%20Stinson%20Club%20Member-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.