# NTSB WPR20LA004: Glaser Dirks DG500, N600TT, Marana, AZ, October 6, 2019 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: October 6, 2019, 13:00 local (20:00 UTC) - Place: Marana, AZ - Coordinates: 32.43, -111.38999 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.4300&lon=-111.3900&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-aerobatics: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: Minor injuries - Injuries: 1 minor, 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 100381 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR20LA004 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/100381/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=100381 - Page: https://openairdocs.org/ntsb/WPR20LA004 ## Probable cause The pilots’ exceedance of the glider’s never-exceed speed (VNE) during recovery from an intentional aerobatic maneuver, which resulted in a failure of the right-wing air brake control drive, asymmetrical air brake deployment, and a subsequent hard landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Wing structure: attach fittings (on wing)](https://openairdocs.org/ntsb-findings/01035740): Aircraft › Aircraft structures · Capability exceeded (probable cause); cases with it: [Elan Flight DG-500 ELAN TRAINER, 1 case](https://openairdocs.org/ntsb-findings/01035740/cases.md?model=3802562), [All aircraft, 21 cases](https://openairdocs.org/ntsb-findings/01035740/cases.md) - [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Elan Flight DG-500 ELAN TRAINER, 1 case](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=3802562), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md) - [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Instructor/check pilot (probable cause); cases with it: [Elan Flight DG-500 ELAN TRAINER, 1 case](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=3802562), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md) - [Performance/control parameters: airspeed](https://openairdocs.org/ntsb-findings/01062010): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [Elan Flight DG-500 ELAN TRAINER, 1 case](https://openairdocs.org/ntsb-findings/01062010/cases.md?model=3802562), [All aircraft, 1,681 cases](https://openairdocs.org/ntsb-findings/01062010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-aerobatics: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Elan Flight DG-500 ELAN TRAINER, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=3802562), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) ## Analysis The pilots were performing aerobatic maneuvers in the glider. While recovering from a maneuver, the glider’s airspeed increased past the never-exceed speed (Vne) and the elevator began to flutter. The right air brake (spoiler) deployed fully, though the spoiler control was in the locked position. After assessing the controllability of the glider, the pilots chose to land at the gliderport rather than perform an emergency egress. The glider landed hard and impacted brush, resulting in the separation of the empennage at the tailboom. Postaccident examination revealed a separation of the right-wing air brake control drive system at the rod end, which resulted in the asymmetrical spoiler extension. The manufacturer stated that it should have been possible to deploy the left-wing air brake normally to compensate for the asymmetric behavior and have some (reduced) control over the approach glidepath. The manufacturer also stated there is no emergency procedure described in the flight manual for air brake malfunctions. It is likely that the air brake control separation was the result of the pilots’ exceedance of Vne during recovery from the aerobatic maneuver. ## Factual narrative On October 6, 2019, about 1300 mountain standard time, an experimental Glaser-Dirks DG-500 Elan Trainer glider, N600TT, sustained substantial damage when it was involved in an accident near Marana, Arizona. The commercial pilot seated in the rear seat sustained minor injuries and the private pilot seated in the front seat was not injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 test flight. The rear seat pilot stated that the purpose of the flight was to perform aerobatic maneuvers as part of the experimental glider’s airworthiness program. The rear seat pilot was also evaluating the front seat pilot’s proficiency in aerobatic maneuvers so that the front seat pilot could fly the glider solo as part of the test program. After completing several maneuvers, the front seat pilot was performing a “Sharks Tooth” maneuver, which comprised a climb, roll to inverted, and a vertical down line. During the maneuver, the front seat pilot rolled inverted, the glider’s nose dropped to 20° above the horizon, and the glider stalled. The rear seat pilot called for the front seat pilot to pull to vertical; however, the front seat pilot did not apply sufficient elevator, and the airspeed increased from around 90 kts to the never-exceed speed (VNE) “almost instantaneously.” The airspeed increased past 155 kts and the glider experienced a high frequency elevator flutter with the nose still below the horizon. During the recovery, the right spoiler deployed, and the pilots felt that the elevator was not controllable. They opted to make an emergency landing to runway 17R/35L at El Tiro Gliderport (AZ67) with minimal directional control from the asymmetrically deployed air brake. The glider landed hard, resulting in damage to the empennage. During a postaccident examination, the rear seat pilot noted that the drive link was disconnected at the rod end of the air brake. He stated that there is significant amount of structure to force the air brakes open but the bearing that was welded to the push/pull tube likely failed after so many years of movement on that bearing. He opined that the part likely had cracks or had been hardened by the manufacturing methods and years of pulling against the outer ring flexed it until failure. The additional forces of the wing bending moment from the high airspeed, and the air loads weakened the joint to fail. The pilot stated that he thought the damage to the glider in flight was because of the excessive speed they reached during the maneuver recovery. According to the manufacturer, similar failures had been reported when the air brakes were extended in negative g-flight. This led to technical note TN348-4T being issued in Germany in 1994. The air brake should be examined as part of the annual inspection and as such, is listed in the maintenance manual. The over center force has to be measured and set accordingly and if the rod end on the air brake side broke off, the stiffness of the air brakecontrol in the wing should be inspected to exclude any damage to the air brake control support structure on the root rib. The manufacturer reported that it should have been possible for the pilots to deploy the other air brake normally to compensate for the asymmetric behavior and have some (reduced) control over the approach glidepath. The air brakes (spoilers) should not be used for normal aerobatics but can be deployed for emergencies. There was no emergency procedure described in the flight manual for air brake malfunction. ## Aircraft - Registration: [N600TT](https://openairdocs.org/deregistered/N600TT-2021-01-28), registration cancelled 2021-01-28, S/N 5E 119 T50, built 1994 (OpenAirDocs) - Reported make and model: Glaser Dirks DG500 (TRAINER) - Registry model: [Elan Flight DG-500 ELAN TRAINER](https://openairdocs.org/model/elan-flight-dg-500-elan-trainer) (registry code 3802562) (OpenAirDocs) - Registry engine: [NONE](https://openairdocs.org/engine/none) (registry code 00000, none) (OpenAirDocs) - Category: Glider - Serial number: 5E 119 T50 - Year built: 1994 - Airframe hours: 1944 - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Tucson Soaring Club Inc. - Registered owner: Tucson Soaring Club Inc. - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, May 11, 2019 - Departed: AZ67, Tucson, AZ - Destination: AZ67, Tucson, AZ - Airport: AZ67, El Tiro, runway 35L, 5,000 × 130 ft, dirt - Equipment: ADS-B, Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 60; injuries: minor; commercial; airplane ratings: single-engine sea, single-engine land; medical: class 3, with waivers/limitations; last flight review September 17, 2019; seat: rear; restraint: 4-point; flight hours: 2,249 total, 8 in this make and model, 2,200 as pilot in command, 11 in the last 90 days, 1 in the last 30 days, 1 in the last 24 hours - Pilot; age 29; injuries: none; private; airplane ratings: single-engine land; medical: class 1, with waivers/limitations; last flight review April 3, 2019; seat: front; restraint: 4-point; flight hours: 269 total, 13 in this make and model, 130 as pilot in command, 44 in the last 90 days, 22 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 270° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 90 °F, dew point 43 °F - Altimeter: 30.07 inHg - Observed at: KRYN, 20 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 20191006018789A](https://openairdocs.org/incident/20191006018789A), Oct 6, 2019: Elan Flight Ltd. DG-500 ELAN TRAINER, Tucson, AZ, Substantial damage. Aircraft was performing aerobatic maneuvers to add to the phase ii capability list. During a 4G recovery, the aircraft entered an overspeed condition and… ## Docket (6 files) The files NTSB released with the investigation on March 8, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=100381. 12.2 MB in all. - Commercial pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 7.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12945787&FileExtension=pdf&FileName=Z%20-%20Attachment%2001%20-%206120%20Pilot_Redacted-Rel.pdf - Pui pilot/operator aircraft accident report NTSB form 6120.1 (item 2, PDF, 9 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12946889&FileExtension=pdf&FileName=Z%20-%20Attachment%2002%20-%206120%20Operator_Redacted-Rel.pdf - Record of conversations (item 3, PDF, 4 pages, 135 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12946794&FileExtension=pdf&FileName=Z%20-%20Attachment%2003%20-%20Record%20of%20Conversations-Rel.pdf - Air brake technical letter (item 4, PDF, 5 pages, 292 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12946545&FileExtension=pdf&FileName=Z%20-%20Attachment%2004-%20Technical%20Letter-Rel.pdf - Flight manual excerpt (item 5, PDF, 4 pages, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12946003&FileExtension=pdf&FileName=Z%20-%20Attachment%2005-%20Flight%20Manual%20Excerpts-Rel.pdf - Photo array and diagram (all provided by pilot) (item 6, PDF, 4 pages, 579 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12946691&FileExtension=pdf&FileName=Z%20-%20Attachment%2006%20-%20Photos%204-Rel.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.