# NTSB ANC09LA100: Grumman G-44A, N86627, Anchorage, AK, September 17, 2009 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 17, 2009, 09:40 local (17:40 UTC) - Place: Anchorage, AK - Coordinates: 61.209499, -149.889312 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.2095&lon=-149.8893&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report October 21, 2010 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration (Airworthiness) - NTSB case key (mKey): 74759 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC09LA100 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74759/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74759 - Page: https://openairdocs.org/ntsb/ANC09LA100 ## Probable cause A fatigue fracture of an unapproved hydraulic brake line fitting, which resulted in a loss of control during the landing roll. Contributing to the accident was the installation of an unapproved part by an unknown maintenance personnel. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: brake](https://openairdocs.org/ntsb-findings/01023242): Aircraft › Aircraft systems · Malfunction (probable cause); cases with it: [Grumman G-44A, 1 case](https://openairdocs.org/ntsb-findings/01023242/cases.md?model=3951508), [All aircraft, 297 cases](https://openairdocs.org/ntsb-findings/01023242/cases.md) - [Maintenance](https://openairdocs.org/ntsb-findings/02062000): Personnel issues › Task performance · Other (probable cause); cases with it: [Grumman G-44A, 1 case](https://openairdocs.org/ntsb-findings/02062000/cases.md?model=3951508), [All aircraft, 143 cases](https://openairdocs.org/ntsb-findings/02062000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-landing roll: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Grumman G-44A, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=3951508), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing-landing roll: Loss of control on ground](https://openairdocs.org/ntsb-events/230); cases with it: [Grumman G-44A, 3 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=3951508), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Grumman G-44A, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=3951508), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) - [Landing-landing roll: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Grumman G-44A, 2 cases](https://openairdocs.org/ntsb-events/300/sequence.md?model=3951508), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) ## Analysis The commercial pilot reported that he was landing his tailwheel-equipped amphibious airplane on a dry, paved runway at the conclusion of a local area postmaintenance flight operated under Title 14, Part 91 after a local facility had completed repairs to the right brake assembly. After landing, the pilot applied the brakes to slow the landing roll, and while depressing both brake pedals, the right brake pedal unexpectedly "went to the floor" and the airplane swerved to the left. The airplane ground looped to the left, sustaining substantial damage to the right wing and right aileron. A postaccident investigation revealed that a hydraulic supply line fitting on the airplane's right brake assembly had broken. The maintenance technician that did the repairs on the airplane's brake reported that the hydraulic supply line fitting was not removed during his work. He also said that he strongly suspected that the broken fitting might be an unapproved or "bogus" aircraft part due to an atypical thread pattern. An NTSB metallurgical examination revealed that the fractured fitting had failed due to a fatigue fracture. A Safety Board mechanical engineer noted that the broken fitting was marked with the "AN" (Air Force-Navy standards) identification stamp, signifying that it was approved for use in aircraft. Further investigation revealed that the fractured fitting was consistent in appearance to that of a fitting manufactured to meet the standards of a Joint Industrial Council (JIC), which is not intended for use in aircraft. The Safety Board mechanical engineer also noted that the two types of fitting are nearly indistinguishable except for the "AN" identification stamp. He added that without the aid of magnification, the "JIC" fittings and the "AN" fittings look identical. The "AN" fitting is reported to have a 40 percent increase in fatigue strength over the identical "JIC" fitting. There was no logbook entry which disclosed replacement of the hydraulic fittings, and the airplane's owner said that he was unaware when the brake line fittings had been replaced, but assumed it had been done prior to him purchasing the airplane. On July 22, 2008, the Federal Aviation Administration (FAA) issued an Advisory Circular (AC) 21-29C, change 1, which provides updated information and guidance to the aviation community for detecting suspected unapproved parts and reporting them to the FAA. ## Factual narrative On September 17, 2009, about 0940 Alaska daylight time, a tailwheel-equipped amphibious Grumman G-44A airplane, N86627, sustained substantial damage during a loss of control after landing at the Merrill Field Airport, Anchorage, Alaska. The airplane was being operated as a visual flight rules (VFR) postmaintenance check flight, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91, when the accident occurred. The commercial pilot/airplane owner and a maintenance technician were not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated at the Merrill Field Airport, about 0915. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on September 17, the pilot noted that the purpose of the flight was to do a postmaintenance check flight after repairs had been completed to the right brake assembly. He said that as he approached the airport, he lowered that airplane’s landing gear, depressed both brake pedals to test that there was adequate hydraulic back-pressure, and then continued the approach. After an uneventful touchdown on Runway 07, a dry paved runway, he applied the brakes to slow the landing roll. He said that while depressing both brake pedals, the right brake pedal unexpectedly "went to the floor" and the airplane swerved to the left. The pilot said that he immediately released pressure on both brake pedals, applied full right rudder, but he could not correct the swerve, and the airplane subsequently ground looped to the left, striking the right wing on the runway. During the ground loop the right wing and right aileron sustained substantial damage. A postaccident examination revealed a broken hydraulic supply line fitting on the airplane’s right brake assembly, with red hydraulic brake fluid sprayed within the right wheel-well area. During an on-scene interview with the NTSB IIC on September 17, the maintenance technician that did the repairs on the airplane’s brake reported that the hydraulic supply line fitting was not removed during his work. He also said that after his postaccident inspection of the broken hydraulic supply line fitting, he strongly suspected that the broken fitting might be an unapproved or "bogus" aircraft part due to an atypical thread pattern, irrespective of the hydraulic fitting having an "AN" (Air Force-Navy standards) identification stamp. The pilot/airplane owner said that the hydraulic brake line fittings had not been changed since he had owned the airplane, and a review of the airplane's maintenance logbooks did not disclose any previous work or replacement of the hydraulic fittings. The broken hydraulic fitting was sent to the NTSB's Materials Laboratory for examination. The hydraulic fitting was inspected on November 18, 2009, at the NTSB's Washington D.C. materials laboratory, under the direction of a senior Safety Board mechanical engineer. The Safety Board engineer reportedthat the fracture surface of the 45-degree elbow fitting displayed two distinct surface textures. One was dull and grainy, features typical of an overload event, and one was shiny and smooth. The smooth shiny surface had multiple ratchet marks, features that are consistent with fatigue. He added that an examination of the major fatigue zone revealed numerous zones containing ratchet marks and crack arrest marks, also typical of fatigue. The Safety Board engineer noted in his report that the broken fitting was marked with the "AN", which signifies it is approved for use in aircraft applications. He said that a nearly identical fitting is available which is intended to be used in industrial applications, and manufactured to meet the standards of the Joint Industrial Council (JIC), but is not intended for use in aviation applications. He wrote, in part: "The two types of fitting are visually indistinguishable except for the 'AN' identification. The most distinguishable difference between the 'AN' and the 'JIC' fitting is in the threads at the flare end." AN Fittings vs. JIC Fittings The "JIC" fitting uses a standard series thread with a flat or partially rounded root. The "JIC" fitting is designated as a class 2 component. The "AN" fitting uses a thread with a controlled root radius, and a tight tolerance thread pattern to achieve an increase in fatigue strength. The "AN" fitting is designated as class 3 component, which has a reported 40 percent increase in fatigue strength over the identical appearing "JIC" fitting. According to the Safety Board engineer, the thread pitch diameter of the fractured fitting was measured using thread triangles and it was found to be consistent with that of a class 2 or "JIC" fitting, which was not intended for use in an aircraft. He said that without the aid of magnification, the "JIC" fittings and the "AN" fittings look identical. A complete copy of the NTSB's materials laboratory factual report is included in the public docket for this accident. On July 22, 2008, the Federal Aviation Administration (FAA) issued an Advisory Circular (AC) 21-29C, change 1, which provides updated information and guidance to the aviation community for detecting suspected unapproved parts (SUP) and reporting them to the FAA. Appendix 1 contains FAA Form 8120-11, Suspected Unapproved Parts Reports, which serves as a standardized means of reporting. As a result of this accident and the subsequent investigation, the airplane owner/pilot replaced all of the "AN" hydraulic fittings to ensure that no remaining unapproved parts remained on his airplane. ## Aircraft - Registration: [N86627](https://openairdocs.org/aircraft/N86627), registered now, S/N 1453, built 1946 (OpenAirDocs) - Reported make and model: GRUMMAN G-44A - Registry model: [Grumman G-44A](https://openairdocs.org/model/grumman-g-44a) (registry code 3951508) (OpenAirDocs) - Registry engine: [Continental I0-470 series](https://openairdocs.org/engine/continental-i0-470-series) (registry code 17027, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 1453 - Airframe hours: 15267 - Engines: CONT MOTOR IO-470 SERIES 260 horsepower reciprocating; CONT MOTOR I0-470 SERIES 260 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Richard R. Taylor - Registered owner: Richard R. Taylor - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 18, 2009, 22 hours before - Departed: MRI, Anchorage, AK - Destination: MRI, Anchorage, AK - Airport: MRI, Merrill Field, runway 07, 4,000 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; injuries: none; commercial; airplane ratings: single-engine sea, multi-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, without waivers/limitations; seat: left; flight hours: 3,560 total, 780 in this make and model, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 46 °F, dew point 45 °F - Altimeter: 29.43 inHg - Observed at: MRI ## 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 20090917049529A](https://openairdocs.org/incident/20090917049529A), Sep 17, 2009: Grumman G-44A, Anchorage, AK, Substantial damage. On 9-16-09, the aircraft was flown for a maintenance test flight after maintenance on several items. The RH gear, outboard wheel half had been replaced. The… ## Other investigations on N86627 (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 FTW65F0006](https://openairdocs.org/ntsb/FTW65F0006), Apr 16, 1965: Grumman G-44A (N86627), Abbeville, LA, minor damage ## Docket (3 files) The files NTSB released with the investigation on August 6, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74759. 1.0 MB in all. - Materials Laboratory 15 - Factual Report 09-074 (item 1, .PDF, 472 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321861&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2009-074-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 2, .PDF, 500 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40334463&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 3, .PDF, 57 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40334464&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.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.