# NTSB CHI94LA277: Beech C90A, N1553N, Janesville, WI, August 19, 1994 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 19, 1994, 12:50 local (17:50 UTC) - Place: Janesville, WI - Coordinates: 42.680915, -89.010307 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.6809&lon=-89.0103&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report January 12, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 9636 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI94LA277 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/9636/pdf - Page: https://openairdocs.org/ntsb/CHI94LA277 ## 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. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Altitude deviation,uncontrolled, cruise - weather condition - turbulence in clouds (contributing factor) - flight into known adverse weather - continued, pilot in command (contributing factor) - wing,spar - bent - design stress limits of aircraft - exceeded, pilot in command (cause) ## Analysis 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. ## Factual 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." ## Aircraft - Registration: N1553N (not matched to a registry record) - Reported make and model: BEECH C90A - Category: Airplane - Serial number: LJ-1238 - Airframe hours: 4749 - Engines: P&W PT6A-21 550 horsepower turbo prop - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: University Of North Dakota, doing business as University Of North Dakota - Registered owner: First Security Bank Of Utah - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, August 4, 1994, 54 hours before - Departed: DET, DETROIT, MI - Destination: GFK, GRAND FORKS, ND - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 27; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 642 total, 70 in this make and model, 226 as pilot in command, 157 in the last 90 days, 20 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 220° at 5 knots - Visibility: 5 statute miles - Lowest ceiling: none - Altimeter: 29.00 inHg - Observed at: JVL ## 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 19940819028039A](https://openairdocs.org/incident/19940819028039A), Aug 19, 1994: Beech C90A, Janesville, WI, Substantial damage. Maneuvering around buildups at FL200 entered cloud severe turbulence. Lost control. Spar damage on abrupt recovery. 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.