# NTSB CEN11CA679: Waltman Theodore J Moose, N384JP, Hays, KS, September 30, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: September 30, 2011, 11:00 local (16:00 UTC) - Place: Hays, KS - Coordinates: 38.838611, -99.270553 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.8386&lon=-99.2706&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed, report February 6, 2012 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA Wichita FSDO - NTSB case key (mKey): 81951 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11CA679 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81951/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81951 - Page: https://openairdocs.org/ntsb/CEN11CA679 ## Probable cause Rudder flutter due to the design changes to the airplane's horizontal stabilizer. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [Waltman Theodore J MOOSE, 1 case](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=05622VK), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) - [Flight control system: rudder tab control system](https://openairdocs.org/ntsb-findings/01022721): Aircraft › Aircraft systems · Design (probable cause); cases with it: [Waltman Theodore J MOOSE, 1 case](https://openairdocs.org/ntsb-findings/01022721/cases.md?model=05622VK), [All aircraft, 6 cases](https://openairdocs.org/ntsb-findings/01022721/cases.md) - [Empennage structure: horizontal stabilizer](https://openairdocs.org/ntsb-findings/01035510): Aircraft › Aircraft structures · Design (probable cause); cases with it: [Waltman Theodore J MOOSE, 1 case](https://openairdocs.org/ntsb-findings/01035510/cases.md?model=05622VK), [All aircraft, 23 cases](https://openairdocs.org/ntsb-findings/01035510/cases.md) - [Empennage structure](https://openairdocs.org/ntsb-findings/01035500): Aircraft › Aircraft structures · Capability exceeded (probable cause); cases with it: [Waltman Theodore J MOOSE, 1 case](https://openairdocs.org/ntsb-findings/01035500/cases.md?model=05622VK), [All aircraft, 14 cases](https://openairdocs.org/ntsb-findings/01035500/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Miscellaneous/other](https://openairdocs.org/ntsb-events/900); cases with it: [Waltman Theodore J MOOSE, 1 case](https://openairdocs.org/ntsb-events/900/sequence.md?model=05622VK), [All aircraft, 1,556 cases](https://openairdocs.org/ntsb-events/900/sequence.md) - [Enroute-cruise: Miscellaneous/other](https://openairdocs.org/ntsb-events/900); cases with it: [Waltman Theodore J MOOSE, 1 case](https://openairdocs.org/ntsb-events/900/sequence.md?model=05622VK), [All aircraft, 1,556 cases](https://openairdocs.org/ntsb-events/900/sequence.md) - [Enroute-cruise: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Waltman Theodore J MOOSE, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=05622VK), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) ## Analysis During cruise flight in smooth air, with the autopilot engaged, the experimental category amateur-built airplane suddenly encountered a single occurrence of rudder flutter that lasted 2 to 3 seconds and then ceased. One passenger described the “frequency of vibration about 10 Hz” (cycles per second) and described the sound as “BRAAP.” The pilot disengaged the autopilot and continued to his original destination for an uneventful landing. A subsequent examination of the airplane found substantial damage to the stringers, frames, and empennage skin in the area just forward of the horizontal stabilizers. The pilot, who was also the builder of the airplane, had added an electrically actuated rudder trim tab several years earlier. Most of the weight of the rudder assembly was aft of the rudder hinges, and the builder had not installed rudder counterbalance weights forward of the hinges. In addition, he had recently installed struts on the bottom of the horizontal stabilizer. Airworthiness standards for certification of normal category airplanes require that they must be shown to be free from flutter. Airworthiness standards for certification of experimental category airplanes do not require that they meet those standards. ## Factual narrative During cruise flight in smooth air, with the autopilot engaged, the experimental category amateur-built airplane suddenly encountered a single occurrence of rudder flutter which lasted two to three seconds and then ceased. One passenger described the “frequency of vibration as about 10 Hz” (cycles per second), and described the sound as “BRAAP.” The pilot disengaged the autopilot and continued to his original destination for an uneventful landing. A subsequent examination of the airplane found substantial damage to the stringers, frames, and empennage skin in the area just forward of the horizontal stabilizers. The pilot, who was also the builder of the airplane, had added an electrically actuated rudder trim tab several years earlier. Most of the weight of the rudder assembly was aft of the rudder hinges and the builder had not installed rudder counterbalance weights forward of the hinges. In addition, he had recently installed struts on the bottom of the horizontal stabilizer. Airworthiness standards for certification of normal category airplanes require that they must be shown to be free from flutter. Airworthiness standards for certification of experimental category airplanes do not require that they meet those standards. ## Aircraft - Registration: [N384JP](https://openairdocs.org/aircraft/N384JP), registered now, S/N 303SR, built 2009 (OpenAirDocs) - Reported make and model: WALTMAN THEODORE J MOOSE - Registry model: [Waltman Theodore J MOOSE](https://openairdocs.org/model/waltman-theodore-j-moose) (registry code 05622VK) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 303SR - Airframe hours: 401 - Engines: VORONEZH M14P 360 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, April 1, 2011, 67 hours before - Departed: 18V, Hudson, CO - Destination: HYS, Hays, KS - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 55; injuries: none; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review July 18, 2009; seat: left; flight hours: 1,130 total, 516 in this make and model, 1,137 as pilot in command, 54 in the last 90 days, 7 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 50 statute miles - Lowest ceiling: none - Temperature: 70 °F - Altimeter: 30.37 inHg ## 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 20110930024529A](https://openairdocs.org/incident/20110930024529A), Sep 30, 2011: Waltman Theodore J MOOSE, Hays, KS, Substantial damage. While en-route from platte valley airpark, co (18V) to Hays, KS (hys), the pilot of an experimental amateur built Moose, N384JP, reported that he encountered a… ## Docket (3 files) The files NTSB released with the investigation on December 7, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81951. 1.2 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 279 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40358803&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Additional Comments From the Builder / Pilot (item 2, .PDF, 74 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40358673&FileExtension=.PDF&FileName=Additional%20Comments%20From%20the%20Builder%20%2F%20Pilot-Master.PDF - Passenger Statements (item 3, .PDF, 874 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40358675&FileExtension=.PDF&FileName=Passenger%20Statements-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.