# NTSB CEN11LA459: Wingtip To Wingtip Panzl S-330, N330JK, Battle Creek, MI, July 3, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 2, 2011, 20:40 local (Jul 3, 2011, 00:40 UTC) - Place: Battle Creek, MI - Coordinates: 42.306388, -85.25 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.3064&lon=-85.2500&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-aerobatics: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 5, 2013 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration, Grand Rapids FSDO - NTSB case key (mKey): 81032 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11LA459 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81032/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81032 - Page: https://openairdocs.org/ntsb/CEN11LA459 ## Probable cause The inadequate aileron hinge design, which resulted in the in-flight separation of the left aileron following a fatigue failure of the center hinge rod-end. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Flight control system: aileron control system](https://openairdocs.org/ntsb-findings/01022710): Aircraft › Aircraft systems · Design (probable cause); cases with it: [Wingtip To Wingtip PANZL S-330, 1 case](https://openairdocs.org/ntsb-findings/01022710/cases.md?model=056170N), [All aircraft, 45 cases](https://openairdocs.org/ntsb-findings/01022710/cases.md) - [Flight control system: aileron control system](https://openairdocs.org/ntsb-findings/01022710): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Wingtip To Wingtip PANZL S-330, 1 case](https://openairdocs.org/ntsb-findings/01022710/cases.md?model=056170N), [All aircraft, 45 cases](https://openairdocs.org/ntsb-findings/01022710/cases.md) - [Flight control system: aileron control system](https://openairdocs.org/ntsb-findings/01022710): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Wingtip To Wingtip PANZL S-330, 1 case](https://openairdocs.org/ntsb-findings/01022710/cases.md?model=056170N), [All aircraft, 45 cases](https://openairdocs.org/ntsb-findings/01022710/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-aerobatics: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [Wingtip To Wingtip PANZL S-330, 1 case](https://openairdocs.org/ntsb-events/338/sequence.md?model=056170N), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) ## Analysis The entire left aileron separated from the airplane as the pilot was performing an aerobatic aileron-roll maneuver during an airshow aerobatic demonstration flight. The pilot was able to recover into level flight and make an uneventful landing. The pilot stated that his preflight inspection before the accident flight did not reveal any mechanical issues with the airplane, including loose jam nuts or any other aileron anomalies. However, the pilot reported that his aviation mechanic had to retighten the jam nut for the center aileron hinge rod-end after it had been found loose on several occasions before the accident flight. A postaccident examination revealed that the center aileron hinge had failed in the shank region of the rod end due to reverse bending fatigue. No material issues were identified with the center aileron rod end, which met the part specifications. A design analysis confirmed that the aileron rod ends were adequate for the limit loads on the structure but were inadequate for fatigue tolerance. The stress levels in the rod end shank were at or above the endurance limit for the specified rod end material, regardless of a loose or tight jam nut. However, a loose jam nut further increased the stress in the rod end about 28 percent and would have reduced the cycles to a fatigue failure. Following the accident, the airplane manufacturer redesigned the aileron bracket assemblies by increasing the diameter of the rod end shank and reducing the moment arm between the bearing and the aileron bracket. The redesign yielded a total stress reduction of about 83 percent in the rod end, which was significantly below the endurance limit for the specified material. ## Factual narrative On July 2, 2011, at 2040 eastern daylight time, a Wingtip to Wingtip, LLC model Panzl S-330 airplane, N330JK, was substantially damaged when the entire left aileron separated from the airplane during an aerobatic flight over W K Kellogg Airport (BTL), Battle Creek, Michigan. The pilot, who was not injured, was able to land the airplane without further issue. The experimental airplane was registered to and operated by John Klatt Airshows, Inc., under the provisions of 14 Code of Federal Regulations Part 91, without a flight plan. Day visual meteorological conditions prevailed for the local airshow demonstration flight that departed at 2035. The pilot reported that the left aileron departed the airplane as he was performing an aerobatic aileron-roll maneuver about 50 feet above the ground at 160 miles per hour with a 30-degree nose-up attitude. The pilot was able to recover into level flight and make an uneventful landing. The pilot reported that his aviation mechanic had to retighten the jam nut for the center aileron hinge rod-end after it had been found loose on several occasions before the accident flight. The pilot stated that his preflight inspection before the accident flight did not reveal any mechanical issues with the airplane, including loose jam nuts or any other aileron anomalies. The left aileron was recovered in three major sections and was sent to the NTSB Materials Laboratory for additional examination. The examination revealed that the center aileron hinge had failed in the shank region of the rod end due to reverse bending fatigue that covered about 90-percent of the fracture face. The remaining 10-percent of the fracture face exhibited overstress signatures. The fatigue zones were located on the upper and lower portions of the fracture face as installed, indicating that the predominant loading was due to the actuation of the aileron. No material issues were identified with the center aileron rod end, which met the specification for a FAFNIR USA part number RE3ML6-2N. The rod end was constructed of AISI 8620 steel that had a specified tensile strength of 90 ksi. The remaining inboard and outboard aileron hinges exhibited fracture features consistent with overstress. The examination did not reveal any material anomalies with the inboard or outboard hinge assemblies. The center rod end was installed in a 2024-T3 aluminum bracket that was attached to the wing rear spar. The rod end was threaded into the end of the bracket utilizing Loctite on the threads and a jam nut that was seated against the bracket to prevent the rod end from backing out. The accident airplane reportedly had experienced a loose jam nut on several flights before the accident. The rod end failed in the area of the shank adjacent to the aft edge of the bracket beneath the area where the jam nut normally was secured. A Finite Element Analysis (FEA) was performed on the design with a loose jam nut and a tight jam nut. The analysis indicated a maximum tensile stressof about 60 ksi at the upper surface of the shank for the loose jam nut condition and about 47.5 ksi for the tightened jam nut. The fore-aft location of the maximum stress was at the shank-to-bracket interface for the loose jam nut condition and at the shank to jam nut interface for the tight jam nut condition. Considering a typical airplane operating weight of 1,600 pounds and the design load factor of 10 G, the total aileron load was about 681 pounds due primarily to the bending stress produced by the vertical load at the bearing. The calculated load on the center hinge was about 286 pounds. The maximum bending stress was about 51.0 ksi and 65.7 ksi for the tight jam nut and loose jam nut conditions, respectively. The maximum bending stress occurred at the upper surface of the shank for the aileron deflected full trailing edge up. The total tensile stress at the upper edge of the shank was 52.4 ksi and 67.1 ksi for the tight jam nut and loose jam nut conditions, respectively. The loose jam nut condition yielded a 28-percent increase in the tensile stress versus the tight jam nut condition. For steel components with a tensile strength less than 160 ksi, the endurance limit is expected to be about 50-percent of the tensile strength for smooth polished specimens. Based on the load estimates, the stress in the rod end was at or above the corresponding endurance limit. Following the accident, the airplane manufacturer redesigned the aileron bracket assemblies by increasing the diameter of the rod end shank and reducing the moment arm between the bearing and the aileron bracket. The redesign yielded a total stress reduction of about 83-percent in the rod end, which was significantly below the endurance limit for the specified material. ## Aircraft - Registration: [N330JK](https://openairdocs.org/aircraft/N330JK), registered now, S/N 009, built 2010 (OpenAirDocs) - Reported make and model: WINGTIP TO WINGTIP, LLC PANZL S-330 - Registry model: [Wingtip To Wingtip PANZL S-330](https://openairdocs.org/model/wingtip-to-wingtip-panzl-s-330) (registry code 056170N) (OpenAirDocs) - Registry engine: [Lycoming IO-540-G1D5](https://openairdocs.org/engine/lycoming-io-540-g1d5) (registry code 41644, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 009 - Airframe hours: 180 - Engines: Lycoming AEIO-540-EXP 300 horsepower reciprocating - Damage: Substantial damage - Flight: Air race/show, Part 91 - Operator: John Klatt Airshows, Inc. - Registered owner: John Klatt Airshows, Inc. - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, April 20, 2011 - Departed: BTL, Battle Creek, MI - Destination: BTL, Battle Creek, MI - Airport: BTL, W K Kellogg Airport, runway 23R, 10,004 × 150 ft, asphalt - Equipment: Angle of attack indicator ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 44; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review October 8, 2009; seat: single; restraint: 5-point; flight hours: 13,000 total, 180 in this make and model, 10,000 as pilot in command, 100 in the last 90 days, 50 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Dusk - Wind: 260° at 8 knots - Visibility: 8 statute miles - Lowest ceiling: 3,500 ft overcast - Temperature: 79 °F, dew point 70 °F - Altimeter: 29.97 inHg - Observed at: BTL ## 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 20110702012079A](https://openairdocs.org/incident/20110702012079A), Jul 2, 2011: Wingtip To Wingtip LLC PANZL S-330, Battle Creek, MI, Substantial damage. Aircraft was part of an airshow at kbtl airport. During a snap roll the pilot heard a loud bang and the left aileron departed the wing. Part of the aileron hit… ## Docket (5 files) The files NTSB released with the investigation on September 26, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81032. 681 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 257 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40401650&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - NTSB Load Analysis of Aileron Hinge Assembly (item 2, .PDF, 160 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40401651&FileExtension=.PDF&FileName=NTSB%20Load%20Analysis%20of%20Aileron%20Hinge%20Assembly-Master.PDF - Email Correspondence with Pilot, John Klatt (item 3, .PDF, 87 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40401652&FileExtension=.PDF&FileName=Email%20Correspondence%20with%20Pilot,%20John%20Klatt-Redacted.PDF - FAA Inspector Statements (item 4, .PDF, 77 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40401654&FileExtension=.PDF&FileName=FAA%20Inspector%20Statements-Redacted.PDF - Confirmation of Wreckage Return (item 5, .PDF, 100 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40401655&FileExtension=.PDF&FileName=Confirmation%20of%20Wreckage%20Return-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.