# NTSB CEN20LA173: Titan Titan Tornado S, N318WH, Haskell, OK, May 9, 2020 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: May 9, 2020, 06:45 local (11:45 UTC) - Place: Haskell, OK - Coordinates: 35.864166, -95.655555 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.8642&lon=-95.6556&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-climb to cruise: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 101254 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20LA173 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101254/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101254 - Page: https://openairdocs.org/ntsb/CEN20LA173 ## Probable cause The student pilot/builder’s addition of winglets to the stabilator, which resulted in flutter and overstress failure of the stabilator control horn. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Empennage structure: horizontal stabilizer](https://openairdocs.org/ntsb-findings/01035510): Aircraft › Aircraft structures · Capability exceeded (probable cause); cases with it: [Holloway William T TITAN TORNADO S, 1 case](https://openairdocs.org/ntsb-findings/01035510/cases.md?model=05634P6), [All aircraft, 23 cases](https://openairdocs.org/ntsb-findings/01035510/cases.md) - [Empennage structure: horiz stab misc structure](https://openairdocs.org/ntsb-findings/01035514): Aircraft › Aircraft structures · Design (probable cause); cases with it: [Holloway William T TITAN TORNADO S, 1 case](https://openairdocs.org/ntsb-findings/01035514/cases.md?model=05634P6), [All aircraft, 3 cases](https://openairdocs.org/ntsb-findings/01035514/cases.md) - [Maintenance: modification/alteration](https://openairdocs.org/ntsb-findings/02062030): Personnel issues › Task performance · Student/instructed pilot (probable cause); cases with it: [Holloway William T TITAN TORNADO S, 1 case](https://openairdocs.org/ntsb-findings/02062030/cases.md?model=05634P6), [All aircraft, 69 cases](https://openairdocs.org/ntsb-findings/02062030/cases.md) - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Holloway William T TITAN TORNADO S, 1 case](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=05634P6), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Student/instructed pilot (probable cause); cases with it: [Holloway William T TITAN TORNADO S, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=05634P6), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/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: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Holloway William T TITAN TORNADO S, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=05634P6), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Emergency descent: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Holloway William T TITAN TORNADO S, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=05634P6), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Holloway William T TITAN TORNADO S, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05634P6), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The student pilot departed on a flight in a kit-built airplane to test the winglets he had recently installed on the airplane’s stabilator, which were intended to eliminate the airplane’s uncommanded yaw. The flight was the airplane's first winglet test flight away from the airport traffic pattern and at a higher altitude. The student stated that during the flight, he decreased the pitch attitude to level off at 2,000 ft above ground level and the airplane suddenly vibrated aggressively and it "felt like the tail was thumping." He decreased the engine power, but the thumping and vibrating continued, so the pilot pitched the airplane down for an off-field emergency landing. Before he was able to land, the airplane rolled inverted and descended into the trees, resulting in the separation of the right wing. Postaccident examination revealed that the stabilator control horn had fractured due to overstress and separated from the push-pull tube. According to an airplane kit manufacturer engineer, winglets added to the stabilator produce flutter. Based on the evidence, it is likely that the winglets led the stabilator to flutter, which overstressed the stabilator control horn and resulted in the control horn’s failure. ## Factual narrative On May 9, 2020, about 0645 central daylight time, an experimental Titan Tornado S airplane, N318WH, was substantially damaged when it was involved in an accident about 3 miles north of Haskell Airport (2K9), Haskell, Oklahoma. The pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. The student pilot stated that the airplane had experienced uncommanded yaw on previously flights which he was trying to eliminate. After some research and a conversation with the airplane kit manufacturer, he installed vortex generators. The vortex generators did not eliminate the yaw, so he installed makeshift winglets on the stabilator, which were made from ½ inch plywood and aircraft speed tape. He did not ask the airplane kit manufacturer about the use of winglets on the stabilator, nor was he required to. The student pilot conducted a test flight with the makeshift winglets and the uncommanded yaw was eliminated. Since the winglets proved successful, he created new winglets out of composite material, then attached them to the stabilator with glue and rivets. He completed 3 to 4 test flights with the new winglets and remained in the traffic pattern for all of the test flights. The airplane maintenance logbooks did not contain any entry for the winglets because the pilot was still conducting test flights and was not ready to have a mechanic sign off on the installation. The student pilot stated that on the morning of the accident, he intended to complete the first winglet test flight away from the airport and at a higher altitude than the other test flights. He departed from 2K9 and climbed about 600 feet per minute to 2,000 ft where he intended to level off. He stated that the airplane flew really well with no anomalies noted at that point. As he decreased the pitch attitude, the airplane suddenly vibrated aggressively and it "felt like the tail was thumping." He decreased the engine power to slow the airplane down and descend in altitude, but the thumping and vibrating continued. He pitched the airplane down for an off-field emergency landing. Before he was able to land, the airplane rolled inverted and descended into the trees. The responding Federal Aviation Administration (FAA) inspector stated that the airplane was found in a densely wooded area with the right wing separated and significant impact damage to the entire airplane. The stabilator control horn was found fractured and disconnected from the push-pull tube. A postaccident examination of the stabilator control horn revealed that it fractured due to overstress from gross mechanical deformation. The part also exhibited impact damage from the stabilator being actuated from control stop to control stop during the flight. The airplane kit manufacturer engineer stated that winglets added to the stabilator would change the balance of the control surface and cause flutter. The stabilator is installed with a counterweight calibratedspecifically for the stock stabilator. He had never seen anyone add winglets to the stabilator before and he hoped that a builder would contact him before adding winglets. He would tell a builder not to add winglets because it would alter the balance on the control surface. ## Aircraft - Registration: [N318WH](https://openairdocs.org/deregistered/N318WH-2020-09-24), registration cancelled 2020-09-24, S/N S12XXXC0HK0546 (OpenAirDocs) - Reported make and model: Titan TITAN TORNADO S (Undesignat) - Registry model: [Holloway William T TITAN TORNADO S](https://openairdocs.org/model/holloway-william-t-titan-tornado-s) (registry code 05634P6) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: S12XXXC0HK0546 - Year built: 2015 - Engines: Rotax 912 ULS 100 horsepower reciprocating - Damage: Substantial damage - Flight: Flight test, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: 100 hour, April 26, 2020, 230 hours before - Departed: 2K9, Haskell, OK - Destination: 2K9, Haskell, OK - Airport: 2K9, Haskell ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: serious; student; airplane ratings: single-engine land; seat: front; flight hours: 162.3 total, 33 in this make and model ## Weather - Conditions: Visual (VMC), Dawn - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 43 °F, dew point 39 °F - Altimeter: 30.29 inHg - Observed at: KMKO, 19 nm away ## 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 20200509006829A](https://openairdocs.org/incident/20200509006829A), May 9, 2020: Holloway William T TITAN TORNADO S, Haskell, OK, Destroyed. Aircraft(N318WH) departed Haskell Airport(2K9) to the north. After leveling off the pilot reported having lost stabilator control. The aircraft went inverted… ## Docket (7 files) The files NTSB released with the investigation on July 1, 2020, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101254. 5.9 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485076&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Correspondence - FAA Inspector (item 2, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485077&FileExtension=.PDF&FileName=Correspondence%20-%20FAA%20Inspector-Master.PDF - Correspondence - Student Pilot (item 3, .PDF, 62 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485078&FileExtension=.PDF&FileName=Correspondence%20-%20Student%20Pilot-Master.PDF - Correspondence - Titan Aircraft Engineer (item 4, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485079&FileExtension=.PDF&FileName=Correspondence%20-%20Titan%20Aircraft%20Engineer%20-Master.PDF - Correspondence - NTSB Materials Lab (item 5, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485080&FileExtension=.PDF&FileName=Correspondence%20-%20NTSB%20Materials%20Lab-Master.PDF - Photos (item 6, .PDF, 824 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485081&FileExtension=.PDF&FileName=Photos-Master.PDF - Maintenance Records (item 7, .PDF, 3.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485082&FileExtension=.PDF&FileName=Maintenance%20Records-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.