# NTSB WPR10CA226: Beech B35, N5032C, Burbank, CA, April 19, 2010 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: April 19, 2010, 14:15 local (21:15 UTC) - Place: Burbank, CA - Coordinates: 34.200553, -118.358612 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.2006&lon=-118.3586&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern base: Turbulence encounter](https://openairdocs.org/ntsb-events/360) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report July 1, 2010 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: FAA FSDO - NTSB case key (mKey): 75937 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR10CA226 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/75937/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=75937 - Page: https://openairdocs.org/ntsb/WPR10CA226 ## Probable cause The airplane's encounter with turbulence while at an airspeed above maneuvering airspeed, which exceeded the limit load of the stabilizers and ruddervators. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Empennage structure: spars/ribs (on rudder)](https://openairdocs.org/ntsb-findings/01035541): Aircraft › Aircraft structures · Capability exceeded (probable cause); cases with it: [Beech B35, 1 case](https://openairdocs.org/ntsb-findings/01035541/cases.md?model=1151506), [All aircraft, 1 case](https://openairdocs.org/ntsb-findings/01035541/cases.md) - [Empennage structure: spars/ribs (on vert stab)](https://openairdocs.org/ntsb-findings/01035531): Aircraft › Aircraft structures · Capability exceeded (probable cause); cases with it: [Beech B35, 1 case](https://openairdocs.org/ntsb-findings/01035531/cases.md?model=1151506), [All aircraft, 1 case](https://openairdocs.org/ntsb-findings/01035531/cases.md) - [Turbulence: clear air turbulence](https://openairdocs.org/ntsb-findings/03032015): Environmental issues › Conditions/weather/phenomena · Effect on equipment (probable cause); cases with it: [Beech B35, 1 case](https://openairdocs.org/ntsb-findings/03032015/cases.md?model=1151506), [All aircraft, 78 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern base: Turbulence encounter](https://openairdocs.org/ntsb-events/360) (defining event); cases with it: [Beech B35, 1 case](https://openairdocs.org/ntsb-events/360/sequence.md?model=1151506), [All aircraft, 423 cases](https://openairdocs.org/ntsb-events/360/sequence.md) ## Analysis The pilot reported that, during descent and at about 5,000 feet, the airplane was flying at 155-160 mph when it hit slight turbulence while in a 15 degree left turn and the tail started to flutter. The pilot quickly reduced power and raised the nose in accordance with the airplane's Pilot Information Manual. This stopped the vibration, which lasted a total of about 3 to 5 seconds. The rest of the approach and landing at the airport was uneventful. During the post-flight inspection, the pilot noticed wrinkles in the ruddervator. A mechanic determined that the left ruddervator had a cracked front spar and that the left stabilizer had wrinkled top skin and a cracked rear spar, which was bent up five inches. Examination of the ruddervators disclosed that they were within the balance requirements of the Beechcraft maintenance manual. The pilot stated that he was between 155 and 160 mph at the time of the turbulence encounter. The maximum structural cruising airspeed for this model variant of the Beech 35 series (Vno or Vc, and the beginning of the yellow caution arc) is 161 mph, and the maneuvering airspeed (Va) is 131 mph. By definition, maximum maneuvering speed (Va) is that speed at which full and abrupt control surface deflection or any turbulence encounter will result in an aerodynamic stall before the structural limit load will be exceeded and damage will occur. Above Va it is possible to incur structural damage with maneuvering inputs and/or significant turbulence encounters. The pilot was flying above Va but within the green airspeed arc when the airplane encountered the turbulence; however, he was not flying in the yellow arc above Vc/Vno and had no reason to believe that the airplane would encounter turbulence. ## Factual narrative In the pilot's written statement to the Safety Board, he reported that he was traveling from Modesto, CA, to Burbank, CA. The pilot reported that during descent to Burbank at about 5,000 feet, the airplane was flying at 155-160 miles per hour when it hit slight turbulence while in a 15 degree left turn, and the tail started to flutter. The pilot quickly reduced power and smoothly raised the nose in accordance with the airplane's Pilot Information Manual. This stopped the vibration, which lasted about 3 to 5 seconds. The rest of the approach and landing at the airport was uneventful. During the post-flight inspection, the pilot noticed wrinkles in the left ruddervator. The airplane was inspected by a mechanic, who found that the left ruddervator had a cracked front spar, and the left stabilizer had wrinkled top skin and a cracked rear spar, which was bent up five inches. The pilot did not state if there were any mechanical problems with the airplane prior to the accident. The airplane's maintenance records were reviewed. In January 2001, the airplane's two rear bulkheads were straightened and redoubled, short cracks were dressed, and new relief flanges were fabricated and installed. Also in January 2001, the empennage skins were redoubled. The airplane was painted as required, the flight controls and systems were reinstalled, and the static control balance was performed. The airplane was inspected for compliance with the pertinent Raytheon (Beechcraft) Service Bulletin. All work was done in accordance with the Service Bulletin, the appropriate Advisory Circular, and the Beechcraft 35 Shop Manual. In April 2001, the airplane's ruddervators were rebuilt and painted. After the painting, the right ruddervator's static balance was 17.33 inch-pounds (in-lb) moment balance. The left ruddervator's static balance was 17.59 in-lb moment balance. Both static balances were within the Beechcraft Shop Manual's allowable balance parameters of 16.8 to 19.8 in-lb. In February 2009, the airplane's fuselage and wings were repainted by the owner, then repainted by a certified mechanic shop. The control surfaces were not painted. After the accident, a mechanic removed and replaced the spars, re-skinned the airplane, used doublers between the spar and the new skin, added a doubler to the center forward of the aft rib, and checked the ruddervator balance. The mechanic stated that the control surface balancing was "perfect." The pilot reported that he was flying between 155-160 miles per hour (MPH) at the time of the turbulence encounter. The maximum structural cruising airspeed (Vno or Vc) is 161 MPH, and the maneuvering airspeed (Va) is 131 MPH. The pilot was flying above Va when the airplane encountered the turbulence; however, he was not flying above Vno and had no reason to believe that the airplane would encounter turbulence. ## Aircraft - Registration: [N5032C](https://openairdocs.org/aircraft/N5032C), registered now, S/N D-2294, built 1950 (OpenAirDocs) - Reported make and model: BEECH B35 - Registry model: [Beech B35](https://openairdocs.org/model/beech-b35) (registry code 1151506) (OpenAirDocs) - Registry engine: [Continental E225 series](https://openairdocs.org/engine/continental-e225-series) (registry code 17015, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: D-2294 - Airframe hours: 6850 - Engines: CONT MOTOR E225-8 225 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Niels Bogh, doing business as Bogh Industries LLC - Registered owner: Bogh Industries LLC - Airworthiness certificate: Standard, Utility - Last inspection: Annual, February 5, 2010 - Departed: KMOD, Modesto, CA - Destination: KBUR, Burbank, CA - Airport: KBUR, Burbank, runway 08, 5,802 × 150 ft, asphalt ## 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 17, 2009; seat: left; flight hours: 696 total, 108 in this make and model, 644 as pilot in command, 24 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 48 °F - Altimeter: 29.94 inHg - Observed at: KBUR ## 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 20100419055569A](https://openairdocs.org/incident/20100419055569A), Apr 19, 2010: Beech B35, Burbank, CA, Substantial damage. NTSB did not notify FAA of accident. FAA unaware of accident until 2/9/2011.according to NTSB report, "the pilot reported that, during descent and at about… ## Other investigations on N5032C (2) 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 SEA66F0221](https://openairdocs.org/ntsb/SEA66F0221), Jan 22, 1966: Beechcraft B35 (N5032C), Warrenton, OR, substantial damage - [NTSB SEA66D0177](https://openairdocs.org/ntsb/SEA66D0177), Nov 5, 1965: Beechcraft B35 (N5032C), Warrenton, OR, substantial damage ## Docket (1 files) The files NTSB released with the investigation on June 4, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=75937. 794 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 794 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40330898&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-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.