Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Boulder, Colorado 80303
Friday, April 1, 2011 17:15 MDT
NTSB Narrative Summary Released at Completion of Accident
Data obtained from an onboard tracking device depicted the glider maneuvering between 21,000 to 23,800 feet mean sea level (msl) before entering a spiral descent, which is consistent with a loss of control. Several eyewitnesses observed the glider descending in a steep spiral turn toward the ground. The glider collided with high voltage transmission wires and terrain in a sparsely wooded area. An examination of the wreckage did not reveal any preimpact anomalies with the glider. Testing of the glider’s oxygen bottle, regulator, and mask detected no anomalies that would have precluded normal operation of the oxygen system. A review of audio recordings revealed that the pilot’s radio transmissions did not have the muffled sounds normally associated with the use of an oxygen mask, suggesting that the pilot may not have been wearing the oxygen mask during a portion of the flight. According to Federal Aviation Administration guidance, on average, a pilot can operate at 22,000 feet msl for about 5 to 10 minutes before losing consciousness due to a lack of oxygen (hypoxia); the glider was above 22,000 feet msl for 13 minutes 36 seconds. Therefore, it is possible that the pilot became incapacitated due to hypoxia.
Additionally, the pilot, who was diabetic and routinely self-tested his blood sugar levels, recorded a blood sugar level of 58 mg/ml about 1 hour 40 minutes before the flight; according to the U.S. Library of Medicine, a blood sugar level below 70 mg/dl is considered low (hypoglycemia). Although it is likely that the pilot addressed the low blood sugar level by eating or taking glucose tablets, his blood sugar level at the time of the accident is unknown. Hypoxia and hypoglycemia have similar symptoms including headache, blurred vision, tingling or numbness, and unclear thinking, and both conditions can lead to loss of consciousness if they are not promptly remedied. There was no record of the pilot being trained to recognize hypoxia symptoms, and it is possible that he may have mistaken the symptoms of hypoxia for hypoglycemia. It is likely that the pilot became incapacitated and lost control of the glider; however, it could not be determined if the pilot's incapacitation was a result of hypoxia, hypoglycemia, or a combination of the two conditions.
NTSB Probable Cause Narrative
The pilot's incapacitation for undetermined reasons, which resulted in a loss of control.
Event Information
| Type of Event | Accident |
| Event Date | 4/1/2011 |
| Event Day of the Week | Friday |
| Time of Event | 1715 |
| Event Time Zone | Mountain Daylight Time |
| Event City | Boulder |
| Event State | COLORADO |
| Event Country | -- |
| Zipcode of the event site | 80303 |
| Event Date Year | 2011 |
| Event Date Month | 4 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 395946N |
| Event Location Longitude | 1051122W |
| Event Location Airport | -- |
| Event Location Nearest Airport ID | -- |
| Indicates whether the acc/inc occurred off or on an airport | -- |
| 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 | 1712 Mountain Daylight Time |
| Direction of event from weather observation facility (degrees) | 326 |
| Weather Observation Facility ID | BDU |
| Elevation of weather observation facility | 5288 |
| Distance of event from weather observation facility (units?) | 4 |
| Time Zone of the weather observation | MDT |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | Clear |
| 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) | 21 |
| Dew Point at event time (in degress fahrenheit) | -12 |
| Wind Direction (degrees magnetic) | 300 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 17 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Gusting |
| Wind Gust (knots) | 21 |
| Altimeter Setting at event time (in. Hg) | 29.88 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | 012312Z AUTO 30017G21KT 10SM CLR 21 M12 A2988 |
| Event Highest Injury | Fatal |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | 1 |
| Injury Total Minor | -- |
| Injury Total None | -- |
| Injury Total Serious | -- |
| Injury Total All | 1 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 29750 |
| NTSB Notification Source | Boulder County Sheriff |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Apr 26 2012 4:33PM |
| User who most recently changed record | snyg |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N633BG |
| NTSB Number | CEN11FA259 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | None |
| Flight plan Was Activated? | -- |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | BURKHART GROB FLUGZEUGBAU |
| Aircraft Model | G102 CLUB ASTIR IIIB |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 5633CB |
| Certified Max Gross Weight | 1100 |
| Aircraft Category | Glider |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | 1 |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 1 |
| Number of Engines | 0 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | Annual |
| Date of Last Inspection | May 1 2010 12:00AM |
| Airframe hours since last inspection | -- |
| Airframe Hours | 2113 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | MILE HIGH YOUTH GLIDING ASSOCIATION INC |
| Aircraft Owner Street Address | 5534 INDEPENDENCE RD |
| Aircraft Owner City | BOULDER |
| Aircraft Owner State | CO |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 80301-3070 |
| Operator is an individual? | No |
| Operator Name | MILE HIGH GLIDING |
| Operator Same as Owner? | No |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | 5534 Independence Rd |
| Operator City | Boulder |
| Operator State | CO |
| Operator Country | USA |
| Operator Zip code | 80301 |
| 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 | BDU |
| Departure City | Boulder |
| Departure State | CO |
| Departure Country | USA |
| Departure Time | 1628 |
| Departure Time Zone | MDT |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | BDU |
| Destination City | Boulder |
| Destination State | CO |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Nov 4 2011 4:07PM |
| User who most recently changed record | aguj |
| Since inspection or accident | Last Inspection |
| Event Location Runway Number and Location | -- |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |