# NTSB DEN07FA089: Schleicher Alexander ASH 26E, N123KS, Castle Rock, CO, April 29, 2007 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: April 29, 2007, 17:13 local (23:13 UTC) - Place: Castle Rock, CO - Coordinates: 39.371387, -104.947776 - Nearby events: https://openairdocs.org/map.md?lat=39.3714&lon=-104.9478&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report August 30, 2007 - Report: Approved by Office Director - Parties: FAA FSDO - NTSB case key (mKey): 65670 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN07FA089 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/65670/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=65670 - Page: https://openairdocs.org/ntsb/DEN07FA089 ## Probable cause the pilot's failure to maintain aircraft control resulting in an inadvertent stall/mush. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight encounter with weather, descent - normal - weather condition - thunderstorm - Loss of control - in flight, cruise - aircraft control - not maintained, pilot in command (cause) - stall/mush - inadvertent, pilot in command (cause) - In flight collision with terrain/water, descent - uncontrolled - terrain condition - ground ## Analysis According to several witnesses, the self-launching sailplane entered a turn to the left. During the turn, the left wing dropped and the sailplane dove towards the ground. Ground scars at the scene were consistent with a nose low, left wing low, impact attitude. An examination of the glider's systems revealed no anomalies. Thunderstorm activity existed along the route of flight. The pilot had not obtained a full weather briefing prior to the flight. ## Factual narrative HISTORY OF FLIGHT On April 29, 2007, at 1713 mountain daylight time, a Schleicher Alexander GMBH ASH 26E self launching sailplane, N123KS, owned and piloted by a commercial pilot, was substantially damaged when it impacted terrain approximately 5 miles west of Castle Rock, Colorado. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 Code of Federal Regulations Part 91 without a flight plan. The pilot was fatally injured. The local flight originated from Kelly Airpark at 1310. According to several members of the Black Forest Soaring Society, the accident pilot arrived at the Kelly Airpark with the intention to fly his personal sailplane. The Black Forest Soaring Society tow plane pilot was unable to fly and the accident pilot elected to fly the club tow plane until another tow pilot was available. They estimate he flew for 1 hour. After conducting 4 tow flights, the accident pilot got into his personal sailplane to fly. According to Black Forest Soaring Society members, 8 to 10 gliders launched from Kelly Airpark the day of the accident. At least five of those gliders, including the accident flight, flew to the west of Kelly Airpark. Three of those flights proceeded as far north as Steamboat Springs, Colorado. The accident flight, and one other glider flew up and down the Front Range. Several witnesses, just west of Castle Rock, observed a sailplane, matching the description of the accident sailplane, flying in the area. One witness reported observing the sailplane enter a bank to the left. The witness stated that the sailplane leveled off and then initiated a turn to the left again. The witness stated that the left wing dropped, and the nose of the sailplane dove straight to the ground. The sailplane disappeared behind the ridge. Another witness observed the flight from a distance and stated that the sailplane was descending. The witness commented that the first 1,000 feet of the descent "did not seem too fast." He stated further that the last 1,000 feet of altitude loss "took place between 30 seconds and a minute." PERSONNEL INFORMATION The pilot, age 44, held a commercial pilot certificate, with an airplane single engine, multi-engine, glider, and instrument ratings, which was last issued on October 1, 2006. He was issued a second class airman medical certificate on October 23, 2006. The certificate contained the limitation that the "holder shall wear lenses that correct for distant vision while exercising the privileges of his/her airman certificate." According to an instructor with the Black Forest Soaring Society, the pilot obtained a spring currency flight April 14, 2007. The flight duration was 45 minutes. The aircraft maintenance log was provided to the National Transportation Safety Board (Safety Board) investigator-in-charge (IIC) for review. The pilot had logged his flight experience in the accident sailplane maintenance log, excluding the accident flight, and the flight from the day prior. According to this log, the pilot had no less than 123 hours in the accident sailplane. The family provided the Safety Board IIC a photocopied page of an aircraft pilot log and a glider pilot log, both appearing to belong to the accident pilot. A review of these flight logs revealed that the accident pilot had logged no less than 1,664 hours total time; 367 hours of which was in gliders. AIRCRAFT INFORMATION The accident sailplane, a Schleicher Alexander GMBH ASH 26E (serial number 26157), was manufactured in 1999. It was registered with the Federal Aviation Administration on a standard airworthiness certificate for utility category operations. The sailplane was equipped with a Diamond AE50R, rotary engine rated for 50 horsepower at 7,500 rpm. The engine was equipped with a 2-blade, stowable propeller. The sailplane was registered to and operated by the pilot, and was maintained under an annual inspection program. A review of the maintenance records indicated that an annual inspection had been completed on April 2, 2007, at an airframe total time of 509 hours. The sailplane had flown approximately 6 hours between the last inspection and the accident. METEOROLOGICAL INFORMATION Weather Radar Data (WSR-88D) (approximately 30 nautical miles northwest of the accident location) scanned the accident area at 1722, 1728, and 1734. Data indicated reflectivity values of 30 to 45 dBz in the accident area round the accident time. Visible satellite and infrared satellite imagery depicted cumulonimbus clouds with cloud top temperatures of minus 41.06 and minus 49.56 degrees Celsius. These temperatures correspond to cloud tops near 31,500 to 35,000 feet mean sea level (msl). Airman's meteorological information (AIRMET) SIERRA for turbulence and TANGO for icing was valid for Colorado, including the accident sailplane's route of flight. No Significant meteorological information (SIGMET) or Convective SIGMET were issued for the time of the accident. A center weather advisory (CWA) for scattered thunderstorms, with tops from 30,000 to 35,000 feet msl, was issued at 1415 and was valid until 2000. Several pilot reports (PIREPS) had been issued for the Denver area regarding turbulence. Reports given for turbulence included light to moderate turbulence from 7,000 feet to 21,000 feet msl. The closest official weather observation station was Centennial Airport (APA), Englewood, Colorado, located 7 nautical miles (nm) north northeast of the accident site. The elevation of the weather observation station was 5,883 feet msl. The routine aviation weather report (METAR) for APA, issued at 1753, reported, winds, 230 degrees at 17 knots, gusting to 22 knots; visibility, 10 statute miles; sky condition, few 8,000, scattered 13,000, broken 22,000; temperature 21 degrees Celsius (C); dewpoint, 02 degrees C; altimeter, 30.07 inches. The remarks section reported virga distant south through west, cumulonimbus clouds distant south. Witnesses in the area, around the time of the accident, reported high, gusty surface winds, and thunderstorm activity directly west of the accident location. One witness reported that the sailplane appeared to have come from the thunderstorm. Heavy rain began shortly after the accident. No record of a weather briefing was found with Flight Service Station or Direct User Access Terminal System (DUATS). WRECKAGE AND IMPACT INFORMATION The National Transportation Safety Board investigator-in-charge (IIC) arrived on scene approximately 1900 on April 29, 2007. The accident site was located in sparsely vegetated, hilly terrain at the corner of a ranch. A global positioning system receiver reported the coordinates of the main wreckage as 39 degrees 22 minutes 17.1 seconds north latitude, and 104 degrees 56 minutes 52.7 seconds west longitude. The accident site was at an elevation of 6,105 feet msl and the sailplane impacted on a magnetic heading of 070 degrees. The first identified point of contact (FIPC) was located to the west of the main wreckage. The FIPC consisted of a ground crater 11 feet long, 4 feet at its widest point, and 8 inches deep. The dirt within the crater was pushed out towards the main wreckage. White paint chips were located within the crater. A second ground scar was located just to the north of the FIPC. This scar was 17 feet in length, 16 inches at its widest point, and was oriented north to south or perpendicular to the FIPC. A third ground scar, located just to the south of the FIPC, was 3 feet long and 4 inches at its widest point. It was oriented in a west to east direction. A debris path extended from the FIPC to the main wreckage. Paint chips, fiberglass, fragmented Plexiglas, various rubber hoses, portions of the control tubes, and fractured control surfaces were all located within the debris path. The main wreckage was located 100 feet from the FIPC and came to rest on a magnetic headin ## Aircraft - Registration: [N123KS](https://openairdocs.org/deregistered/N123KS-2017-04-04), registration cancelled 2017-04-04, S/N 26157, built 1999 (OpenAirDocs) - Reported make and model: Schleicher Alexander GMBH ASH 26E - Registry model: [Schleicher Alexander ASH 26 E](https://openairdocs.org/model/schleicher-alexander-ash-26-e) (registry code 05624RU) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Glider - Serial number: 26157 - Airframe hours: 509 - Engines: Diamond AE50R 50 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Utility - Last inspection: Annual, April 1, 2007, 6 hours before - Departed: PVT, Kelly Airpark, CO - Destination: CO ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 44; injuries: fatal; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; seat: center; toxicology performed; flight hours: 1,664 total, 123 in this make and model, 8 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 17 knots, gusting 22 - Visibility: 10 statute miles - Lowest ceiling: 22,000 ft broken - Temperature: 70 °F, dew point 36 °F - Altimeter: 30.06 inHg - Observed at: KAPA, 15 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 20070429005419A](https://openairdocs.org/incident/20070429005419A), Apr 29, 2007: Schler ASH26E, Castle Rock, CO, Destroyed, 1 fatal. (-23) On 29 April 2007 at approximately 1720 local time, an ash 26 e glider, piloted by the pilot [privacy data omitted] impacted the ground 5.3 miles… ## Docket (10 files) The files NTSB released with the investigation on August 16, 2007, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=65670. 16.9 MB in all. - Witness Statements (item 1, .PDF, 79 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40276652&FileExtension=.PDF&FileName=Witness%20Statements-Redacted.PDF - Maps or Charts of Accident Area (item 2, .PDF, 14.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40276653&FileExtension=.PDF&FileName=Maps%20or%20Charts%20of%20Accident%20Area-Master.PDF - Weather Information (item 3, .PDF, 379 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40276654&FileExtension=.PDF&FileName=Weather%20Information-Master.PDF - 302 Instrument Download Data (item 4, .PDF, 342 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40276657&FileExtension=.PDF&FileName=302%20Instrument%20Download%20Data-Master.PDF - Toxicological Report (item 5, .PDF, 477 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40279432&FileExtension=.PDF&FileName=Toxicological%20Report-Master.PDF - Wreckage Release (item 6, .PDF, 113 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40377339&FileExtension=.PDF&FileName=Wreckage%20Release-Redacted.PDF - Photograph 01 - Initial impact, debris path, and main wreckage (item 7, .PDF, 239 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40276658&FileExtension=.PDF&FileName=Photograph%2001%20-%20Initial%20impact,%20debris%20path,%20and%20main%20wreckage-Master.PDF - Photograph 02 - Main wreckage - rear view (item 8, .PDF, 279 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40276660&FileExtension=.PDF&FileName=Photograph%2002%20-%20Main%20wreckage%20-%20rear%20view-Master.PDF - Photograph 03 - Main wreckage - front view (item 9, .PDF, 270 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40276662&FileExtension=.PDF&FileName=Photograph%2003%20-%20Main%20wreckage%20-%20front%20view-Master.PDF - Photograph 04 - Main wreckage - left side view (item 10, .PDF, 238 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40276663&FileExtension=.PDF&FileName=Photograph%2004%20-%20Main%20wreckage%20-%20left%20%20side%20view-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.