Flight Safety Alaska Inc
Location: Anchorage, Alaska
Accident Number: GAA16CA487
Date and Time: September 1, 2016, 13:12 Local
Registration: N52950
Aircraft: Cessna 172
Aircraft Damage: Substantial
Defining Event: Miscellaneous/other
Injuries: 2 None
Flight Conducted Under: Part 91: General aviation - Instructional
Analysis
The flight instructor reported that during taxi the airplane started to lean to the right, so he looked out of his window to see if the right tire was flat. He further reported that "the ramp was opening up into a 2 foot wide dark black hole" underneath the right main landing gear. The flight instructor and student pilot egressed from the airplane without further incident.
A postaccident examination revealed substantial damage to the empennage.
The flight instructor reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.
Photographs provided by Federal Aviation Administration showed that the right main landing gear had broken through the pavement into a sink hole underneath.
Probable Cause and Findings
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The airplane's encounter with a developing sink hole during taxi on the ramp area.
Findings
Environmental issues (general) - Effect on equipment
Factual Information
History of Flight
Taxi-to runway Miscellaneous/other (Defining event)
Pilot Information
Certificate: Commercial; Flight instructor
Age: 33, Male
Airplane Rating(s): Single-engine land; Multi-engine land
Seat Occupied: Right
Other Aircraft Rating(s): None
Restraint Used: 3-point
Instrument Rating(s): Airplane
Second Pilot Present: Yes
Instructor Rating(s): Airplane single-engine; Instrument airplane
Toxicology Performed: No
Medical Certification: Class 1 Without waivers/limitations
Last FAA Medical Exam: March 23, 2016
Occupational Pilot: Yes
Last Flight Review or Equivalent: May 1, 2015
Flight Time: (Estimated) 967 hours (Total, all aircraft), 600 hours (Total, this make and model)
Student pilot Information
Certificate: Student
Age: 31,Male
Airplane Rating(s): None
Seat Occupied: Left
Other Aircraft Rating(s): None
Restraint Used: 3-point
Instrument Rating(s): None
Second Pilot Present: Yes
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 3 Without waivers/limitations
Last FAA Medical Exam: July 11, 2016
Occupational Pilot: No
Last Flight Review or Equivalent:
Flight Time: (Estimated) 10 hours (Total, all aircraft), 10 hours (Total, this make and model)
Aircraft and Owner/Operator Information
Aircraft Make: Cessna
Registration: N52950
Model/Series: 172P
Aircraft Category: Airplane
Year of Manufacture: 1981
Amateur Built:
Airworthiness Certificate: Normal
Serial Number: 17274642
Landing Gear Type: Tricycle
Seats: 4
Date/Type of Last Inspection: August 19, 2016 Annual
Certified Max Gross Wt.: 2400 lbs
Time Since Last Inspection:
Engines: 1 Reciprocating
Airframe Total Time:
Engine Manufacturer: LYCOMING
ELT: Installed, not activated
Engine Model/Series: O-320
Registered Owner:
Rated Power: 180 Horsepower
Operator:
Operating Certificate(s) Held: None
Meteorological Information and Flight Plan
Conditions at Accident Site: Visual (VMC)
Condition of Light: Day
Observation Facility, Elevation: PAMR,138 ft msl
Distance from Accident Site: 0 Nautical Miles
Observation Time: 01:53 Local
Direction from Accident Site: 299°
Lowest Cloud Condition: Few / 4900 ft AGL
Visibility: 10 miles
Lowest Ceiling: Overcast / 6500 ft AGL
Visibility (RVR):
Wind Speed/Gusts: 3 knots /
Turbulence Type Forecast/Actual: / None
Wind Direction: 20°
Turbulence Severity Forecast/Actual: / N/A
Altimeter Setting: 30.02 inches Hg
Temperature/Dew Point: 19°C / 12°C
Precipitation and Obscuration: Light - None - Rain
Departure Point: Anchorage, AK (MRI)
Type of Flight Plan Filed: None
Destination: Anchorage, AK (MRI)
Type of Clearance: None
Departure Time:
Type of Airspace: Class D
Airport Information
Airport: MERRILL FIELD MRI
Runway Surface Type:
Airport Elevation: 137 ft msl
Runway Surface Condition: Dry
Runway Used:
IFR Approach: None
Runway Length/Width:
VFR Approach/Landing: None
Wreckage and Impact Information
Crew Injuries: 2 None
Aircraft Damage: Substantial
Passenger Injuries:
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 2 None
Latitude, Longitude: 61.213054,-149.839996 (est)
