Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Bourne Stage, Texas 78216
Tuesady, June 23, 2009 12:49 CDT
NTSB Narrative Summary Released at Completion of Accident
The pilot noticed a light fluttering of the rudder pedals that stopped when he applied gentle foot pressure. The motor glider was in level cruise flight when it suddenly began to shake violently, throwing the pilot back and forth against his restraints. He said that the airspeed was about 80 KIAS (knots indicated airspeed); however, data available from the airplane’s on-board Global Positioning System (GPS) indicates that the aircraft was flying approximately 110 KCAS (knots calibrated airspeed). The pilot deployed the emergency ballistic parachute and the aircraft landed gently on top of small trees, sustaining additional damage. Postaccident examination of the motor glider revealed the empennage had separated from the fuselage, but remained attached by control cables and tubing. GPS data showed the aircraft’s airspeed had gradually increased to about 110 KCAS when the in-flight breakup occurred.
After a similar accident in the Czech Republic, the never-exceed speed (Vne or redline) was lowered from 119 KCAS to 81 KCAS. The accident airplane’s airspeed indicator had two redlines: one was at 119 knots and the other was taped onto the instrument glass at 81 knots and was in the middle of the green arc. The pilot said that he was not aware that the Vne speed was 81 KCAS, but that the change was a temporary flight recommendation from the manufacturer. He said that he had received the memorandum containing the temporary restriction on airspeed not to exceed 81 KCAS in any configuration, but that he “did not think the 81 knots was a Vne speed.” The manufacturer had lowered the Vne as a temporary measure because of a previous accident where an in-flight structural failure of the aft portion of the fuselage occurred. The investigation of the first accident by Air Accident Investigations Institute, Republic of Czechoslovakia, determined that the separation was the result of aerodynamic flutter in the empennage. According to the NTSB’s Materials Laboratory report, the fractures were consistent with compressive loads and tension or tearing from local bending. No evidence of manufacturing errors or preaccident damage was noted.
NTSB Probable Cause Narrative
The pilot’s exceedance of the aircraft’s placarded never-exceed speed (Vne), resulting in aerodynamic flutter in the empennage and the subsequent in-flight structural failure of the aft portion of the fuselage.
Event Information
| Type of Event | Accident |
| Event Date | 6/23/2009 |
| Event Day of the Week | Tuesday |
| Time of Event | 1249 |
| Event Time Zone | Central Daylight Time |
| Event City | Bourne Stage |
| Event State | TEXAS |
| Event Country | -- |
| Zipcode of the event site | 78216 |
| Event Date Year | 2009 |
| Event Date Month | 6 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 293201N |
| Event Location Longitude | 0982811W |
| Event Location Airport | -- |
| Event Location Nearest Airport ID | -- |
| Indicates whether the acc/inc occurred off or on an airport | Off Airport/Airstrip |
| Distance from airport in statute miles | -- |
| Degrees magnetic from airport | -- |
| Airport Elevation | -- |
| Weather Briefing Completeness | -- |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1253 Central Daylight Time |
| Direction of event from weather observation facility (degrees) | 284 |
| Weather Observation Facility ID | SAT |
| Elevation of weather observation facility | 800 |
| Distance of event from weather observation facility (units?) | 13 |
| Time Zone of the weather observation | CDT |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | 6000 |
| Sky/Lowest/Cloud Conditions | Few |
| Sky Condition for Lowest Ceiling | -- |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 33 |
| Dew Point at event time (in degress fahrenheit) | 18 |
| Wind Direction (degrees magnetic) | 140 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 5 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 29.92 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | -- |
| Event Highest Injury | None |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 1 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 27822 |
| NTSB Notification Source | FAA ASW ROC |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Jan 27 2011 12:24PM |
| User who most recently changed record | broda |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N17UA |
| NTSB Number | CEN09LA379 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | None |
| Flight plan Was Activated? | No |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | Urban Air SRO |
| Aircraft Model | UFM-13 |
| Aircraft Series Identifier | Lambada |
| Aircraft Serial Number | 113/13 |
| Certified Max Gross Weight | 1320 |
| Aircraft Category | Glider |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | 2 |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 2 |
| Number of Engines | 1 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | -- |
| Date of Last Inspection | -- |
| Airframe hours since last inspection | -- |
| Airframe Hours | -- |
| ELT Installed | No |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | -- |
| Aircraft Owner Name | San Antonio Light Sport Aircraft, Inc. |
| Aircraft Owner Street Address | 14400 Spearmint Tea Trl |
| Aircraft Owner City | Pflugerville |
| Aircraft Owner State | TX |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 78660 |
| Operator is an individual? | No |
| Operator Name | San Antonio Light Sport Aircraft, Inc. |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | 14400 Spearmint Tea Trl |
| Operator City | Pflugerville |
| Operator State | TX |
| Operator Country | USA |
| Operator Zip code | 78660 |
| Operator Code | -- |
| Owner has at least one certificate | None |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | -- |
| Operator Certificate Number | -- |
| Indicates whether an air carrier operation was scheduled or not | -- |
| Indicates Domestic or International Flight | -- |
| Operator carrying Pax/Cargo/Mail | -- |
| Type of Flying (Per_Bus / Primary) | Personal |
| Second Pilot on Board | No |
| Departure Point Same as Event | No |
| Departure Airport Code | 5C1 |
| Departure City | Boerne Stage |
| Departure State | TX |
| Departure Country | USA |
| Departure Time | 1202 |
| Departure Time Zone | CDT |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | 5C1 |
| Destination City | Boerne Stage |
| Destination State | TX |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Apr 26 2010 3:29PM |
| User who most recently changed record | scoa |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | N/A |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |