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Data Source: NTSB AVIATION ACCIDENT/INCIDENT DATABASE Report Number: CHI94LA277 Local Date: 08/19/1994 Local Time: 12:50 CDT State: WI City: JANESVILLE Airport Name: Airport Id: Event Type: ACCIDENT Injury Severity: NONE Report Status: FINAL Mid Air Collision: NO
Category of Operation: GENERAL AVIATION Aircraft Type: AIRPLANE Aircraft Damage: SUBSTANTIAL Phase of Flight: 540 CRUISE Aircraft Make/Model: BEECH BE-90-C90A Operator Doing Business As: UNIVERSITY OF NORTH DAKOTA Operator Name: UNIVERSITY OF NORTH DAKOTA Operator Code: Operator: Owner Name: FIRST SECURITY BANK OF UTAH
WHILE IN CRUISE FLIGHT AT 20,000 FEET MEAN SEA LEVEL, AND MA NEUVERING AROUND BUILD-UPS THE FLIGHT ENTERED IMC. SHORTLY AFTER ENTERING THE CLOUDS THE AIRPLANE ENCOUNTERED SEVERE TU RBULENCE AND SOME OF THE FLIGHT INSTRUMENTS BECAME UNRELIABLE (TUMBLED). POSITIVE CONTROL OF THE AIRPLANE WAS REGAINED BETWEEN 16,800 AND 17,000 MSL. SUBSEQUENT EXAMINATION FOUND SUBSTANTIAL DAMAGE TO THE AIRFRAME.
Occurrence #: 1 110 ALTITUDE DEVIATION, UNCONTROLLED
Phase of Operation: 540 CRUISE
Findings
Subject - Modifier - Personnel Cause/Factor
1a. 20000(S) - 2226(M) Factor
WEATHER CONDITION - TURBULENCE IN CLOUDS
1b. 24023(S) - 3102(M) - 4000(P) Factor
FLIGHT INTO KNOWN ADVERSE WEATHER - CONTINUED - PILOT IN COMMAND
2a. 10101(S) - 1104(M)
WING, SPAR - BENT
2b. 24538(S) - 3107(M) - 4000(P) Cause
DESIGN STRESS LIMITS OF AIRCRAFT - EXCEEDED - PILOT IN COMMAND
THE PILOT-IN-COMMAND'S EXCEEDING THE DESIGN STRUCTURAL LIMITS OF THE AIRPLANE. FACTORS WERE TURBULENCE IN CLOUDS AND THE PILOT- IN-COMMAND;S CONTINUED FLIGHT INTO KNOWN ADVERSE WEATHER.
Number of Seats: 8
Aircraft Use: INSTRUCTIONAL
Type of Operation: 14 CFR 91
Domestic/International:
Passenger/Cargo:
Registration Number: 1553N
Air Carrier Operating Certificates:
Aircraft Fire: NONE
Injuries
Fatal Serious Minor None
Crew 0 0 0 3
Pass 0 0 0 0
Other 0 0 0 0
Invlvd 0 0 0 3
Landing Gear: TRICYCLE-RETRACTABLE
Certificated Maximum Gross Weight: 10160
Engine Make: P & W
Engine Model: PT6A-21
Number of Engines: 2
Engine Type: TURBO PROP
Basic Weather Conditions: VISUAL METEOROLOGICAL CONDITIONS (VMC) Wind Direction (deg): 220 Wind Speed (knots): 5 Visibility (sm): 5 Visibility RVR (ft): 0 Visibility RVV (sm): 0 Cloud Height Above Ground Level (ft): 9000 Visibility Restrictions: HAZE (H) Precipitation Type: NONE Light Condition: DAYLIGHT Departure Airport Id: DET Departure City: DETROIT Departure State: MI Destination Airport Id: GFK Destination City: GRAND FORKS Destination State: ND Flight Plan Filed: INSTRUMENT FLIGHT RULES (IFR) ATC Clearance: IFR VFR Approach/Landing: Event Location: OFF AIRPORT/AIRSTRIP
Certificates: COMMERCIAL
Ratings:
Plane: SINGLE ENGINE LAND, MULTIENGINE LAND
Non-Plane: NONE
Instrument: AIRPLANE
Had Current BFR: YES
Months Since Last BFR: 5
Medical Certificate: CLASS 1
Medical Certificate Validity: VALID MEDICAL-NO WAIVERS/LIMITATIONS
Flight Time (Hours)
Total : 642 Last 24 Hrs : 7
Make/Model : 70 Last 30 Days: 20
Instrument : 94 Last 90 Days: 157
Multi-Engine: 402 Rotorcraft : 0
NTSB Identification: CHI94LA277. The docket is stored in the (offline) NTSB Imaging System.
Accident occurred AUG-19-94 at JANESVILLE, WI
Aircraft: BEECH C90A, registration: N1553N
Injuries: 3 Uninjured.
WHILE IN CRUISE FLIGHT AT 20,000 FEET MEAN SEA LEVEL, AND MANEUVERING AROUND
BUILD-UPS THE FLIGHT ENTERED IMC. SHORTLY AFTER ENTERING THE CLOUDS THE AIRPLANE
ENCOUNTERED SEVERE TURBULENCE AND SOME OF THE FLIGHT INSTRUMENTS BECAME
UNRELIABLE (TUMBLED). POSITIVE CONTROL OF THE AIRPLANE WAS REGAINED BETWEEN
16,800 AND 17,000 MSL. SUBSEQUENT EXAMINATION FOUND SUBSTANTIAL DAMAGE TO THE
AIRFRAME.
Probable Cause
the pilot-in-command's exceeding the design structural limits of the airplane.
Factors were turbulence in clouds and the pilot- in-command's continued flight
into known adverse weather.
Full Narrative:
On August 19, 1994, at approximately 1250 central daylight time, a Beech C90A, N1553N, operated by the University of North Dakota, and piloted by commercial pilots, encountered severe turbulence while deviating around weather at 20,000 feet mean sea level, in the vicinity of Janesville, Wisconsin. The airplane experienced an uncontrolled altitude deviation, descending 3,000 feet before recovery by the pilots. During the recovery the airframe sustained substantial damage. The two pilot crew and one non- flying instructor reported no injuries. The CFR 14 Part 91 instructional flight was on an instrument flight plan. Thunderstorms were reported in the area. The flight departed Detroit, Michigan, at 1230. After the event the flight continued to the intended destination of Grand Forks, North Dakota.
The instructor pilot in a detailed statement indicated that in the vicinity of Janesville, Wisconsin, while cruising at 20,000 feet mean sea level, and maneuvering around build-ups the flight entered instrument meteorological conditions. Shortly after entering the clouds the airplane encountered severe turbulence and some of the flight instruments became unreliable (tumbled). She said that the power was reduced and the vertical speed indicator was observed to indicate a 3,000 feet per minute altitude loss and the airspeed indicator was at the "barber pole." Positive control of the airplane was regained between 16,800 and 17,000 feet. The flight then continued to the destination airport without further incident.
The instructor stated that weather was checked prior to departure from Detroit, Michigan, and the possibility of thunderstorm activity along the proposed route of flight was forecast.
The instructor pilot stated that an examination of the airframe after the event revealed that the airframe had sustained substantial damage as a result of the weather encounter; however, she stated that she does "not feel that the control inputs during the recovery were in such a manner to over-stress the aircraft."
Source: National Transportation Safety Board