Individually Owned: 150,657
Corporate Owned: 137,281
N/A Airport
Aircraft Accident/Incident Report
Cassville, Missouri 65625
Sunday, February 6, 2011 11:15 CST
NTSB Narrative Summary Released at Completion of Accident
The airplane was in cruise flight when its propeller separated. The pilot performed a forced landing to a snow-covered field, during which the nose landing gear collapsed causing minor damage. Postaccident metallurgical examination of the crankshaft extension attachment bolts revealed that they had fractured from fatigue due to insufficient clamping force. Dish-shaped washers were installed between the bolt head and extension, and thread locking compound was found trapped under the concave side of the washers. The maintenance manual in effect at the time of the incident called for application of thread locking compound to both the female threads in the crankshaft and to the male bolt threads. However, this procedure has the potential for inadvertently wiping a portion of the thread locking compound that is applied to the bolt onto the face of the propeller extension without the installer knowing, thereby trapping it between the washer and the extension face. In this incident, the torque applied to the attachment bolts at installation was insufficient to squeeze out the thread locking compound from under the washers and compress the washers flat, which would have produced the proper metal-to-metal contact. While the applied torque may have been less than specified, it is also possible that the trapped thread locking compound may have had a hydraulic effect that resisted the clamping force associated with a properly applied torque. In the former case, insufficient clamping force would have been present from the time of installation. In the latter case, clamping force could have lessened over time due to wear at the edges of the washer, compression creep, and wear of the trapped thread locking compound. Since this event, the manufacturer has implemented changes to the maintenance procedures with detailed instructions and warnings to prevent contamination of the crankshaft, propeller hub extension, washers, and bolt faces with thread locking compound. In addition, the design of the hub attachment has been modified to incorporate three 8 millimeter dowel pins between the hub and crankshaft to prevent movement between the propeller extension and crankshaft.
NTSB Probable Cause Narrative
The fatigue failure of the propeller hub retaining bolts due to insufficient clamping force .
Event Information
| Type of Event | Incident |
| Event Date | 2/6/2011 |
| Event Day of the Week | Sunday |
| Time of Event | 1115 |
| Event Time Zone | Central Standard Time |
| Event City | Cassville |
| Event State | MISSOURI |
| Event Country | -- |
| Zipcode of the event site | 65625 |
| Event Date Year | 2011 |
| Event Date Month | 2 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 394035N |
| Event Location Longitude | 0935208W |
| Event Location Airport | N/A |
| 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 | 1715 Coordinated Universal Time? Same as GMT |
| Direction of event from weather observation facility (degrees) | 315 |
| Weather Observation Facility ID | HFJ |
| Elevation of weather observation facility | 1313 |
| Distance of event from weather observation facility (units?) | 14 |
| Time Zone of the weather observation | UTC |
| Lighting Conditions | Day |
| Lowest Ceiling Height | 1800 |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | -- |
| Sky Condition for Lowest Ceiling | Broken |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 3 |
| Dew Point at event time (in degress fahrenheit) | -1 |
| Wind Direction (degrees magnetic) | -- |
| Variable Wind Indicator | -- |
| Wind Speed (knots) | -- |
| Wind Velocity Indicator | Calm |
| Wind Gust Indicator | -- |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 29.91 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | METAR KHFJ 061715Z AUTO 00000KT 10SM BKN018 03/M01 |
| 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 | 2 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 32023 |
| NTSB Notification Source | Tom Bartells - FAA KC FSDO |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Oct 29 2013 10:44AM |
| User who most recently changed record | brajo |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N904MS |
| NTSB Number | CEN11IA235 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | None |
| Flight plan Was Activated? | No |
| Damage | Minor |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | SCHLICHTMAN |
| Aircraft Model | STOL CH750 |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 75-7495 |
| Certified Max Gross Weight | -- |
| Aircraft Category | Airplane |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | Yes |
| Flight Crew Seats | -- |
| 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 | Conditional |
| Date of Last Inspection | Mar 3 2012 12:00AM |
| Airframe hours since last inspection | 90 |
| Airframe Hours | 125 |
| ELT Installed | Unknown |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | Michael E Schlichtman |
| Aircraft Owner Street Address | PO Box 562 |
| Aircraft Owner City | Cassville |
| Aircraft Owner State | MO |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 65625 |
| Operator is an individual? | Yes |
| Operator Name | Michael E Schlichtman |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | PO Box 562 |
| Operator City | Cassville |
| Operator State | MO |
| Operator Country | USA |
| Operator Zip code | 65625 |
| Operator Code | -- |
| Owner has at least one certificate | None |
| Other Operator of large aircraft? | -- |
| 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 | 94K |
| Departure City | Cassville |
| Departure State | MO |
| Departure Country | USA |
| Departure Time | 1105 |
| Departure Time Zone | CST |
| Destination Same as Local Flt | dest & departure same, accident can occur anywhere |
| Destination Airport Code | 94K |
| Destination City | Cassville |
| Destination State | MO |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Oct 29 2013 10:44AM |
| User who most recently changed record | brajo |
| Since inspection or accident | Time of Accident |
| Event Location Runway Number and Location | N/A |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |