TOOELE, UT, USA
N9594V
Cessna 172M
The pilot stated that just after takeoff, the airspeed began decreasing, the stall warning horn sounded, and the airplane started sinking despite attempts at corrective action. The airplane impacted the ground beyond the departure end of the runway. Density altitude was 6,385 feet. A videotape, filmed by a rear-seat passenger, showed that the aircraft reached a pitch attitude of up to 24 degrees nose-high after takeoff. It also recorded a sound, resembling the stall warning horn, 42 seconds after start of takeoff roll (about 18 to 19 seconds after becoming airborne), and it recorded no significant change in engine noise pitch during the event. The airplane's electrical flap switch demonstrated improper mechanical operation 'due to normal wear' during postaccident functional testing. Investigation revealed that the pilot took off uphill to the south (average runway slope was 0.81 percent). The FAA's regional airport master record and the Utah state aeronautical chart wrongly indicated that the runway sloped uphill to the north, rather than to the south. The Airport/Facility Directory (A/FD) gave no runway slope data for the airport; the A/FD legend stated that the runway slope would be shown 'only when it is 0.3 percent or more.'
On June 7, 1996, at approximately 1050 mountain daylight time, N9594V, a Cessna 172M operated by American Aviation, Inc. of Salt Lake City, Utah, sustained substantial damage in a collision with terrain immediately after takeoff from Bolinder Field-Tooele Valley Airport, Tooele, Utah. The aircraft was being operated under 14 CFR 91 on an introductory instructional flight at the time of the accident. The commercial pilot (who was a certificated flight instructor), a dual student, and a rear-seat passenger received minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the local flight. The instructor reported: ...The wind sock was full favoring a south departure....I completed the runup and taxied onto [runway] 16. I applied full throttle and the airspeed began to build up. I rotated the aircraft at 60 [MPH]. I began to climb. All the engine instruments were good. The airspeed was still increasing. Then it began to decrease. I began to drift westward and the stall warning horn went off. I [proceeded] to pitch to level, I checked the engine and flight instruments. The power was at 2300 RPM. The airspeed was bleeding off. The airplane began sinking. I pushed the mixture full rich and checked for full throttle, primer in and locked, and magnetos on both. We were still sinking. I added flaps because I was [committed] to land.... I was still losing altitude and airspeed. The left wing began to dip down. I used the ailerons and rudder to get wings level. I then held the nose off as long as I could.... The aircraft impacted the ground beyond the departure end of the runway. The pilot reported winds on his accident report as being from an estimated 160 degrees magnetic, based on the wind sock, at "10+" knots. He reported the temperature as 80 degrees F. Based on the pilot's reported temperature, Tooele Valley's field elevation of 4,316 feet above sea level, and Salt Lake City's reported altimeter setting of 30.19 inches Hg at the time of the accident, density altitude at Tooele Valley at the time was approximately 6,385 feet. The passengers consisted of a teenage boy, who was receiving dual instruction in the left front seat, and an adult woman, who videotaped the accident sequence from the rear seat using a personal videocamera. Neither passenger furnished a written or verbal statement to investigators. However, the adult passenger provided the videotape to investigators. This tape was in a stretched and broken condition at the time it was received at the NTSB's Seattle office. The tape was spliced at the break using tape, rewound, and copied. The copy was then viewed. Review of the copy of the videotape revealed the following information. The airport windsock was momentarily filmed during the taxi out for takeoff and showed light southerly to southeasterly winds. The takeoff was filmed from a point corresponding approximately to the start of the takeoff roll (this point is referred to hereafter as "start of film."). The aircraft passed a runway touchdown zone marking approximately 15 seconds after start of film and then became airborne about 23 to 24 seconds after start of film. Using the track of the runway edge during the ground roll as a horizontal reference and the bottom edge of the left side rear window as a reference for the aircraft fuselage reference line, the aircraft attained a maximum nose-up pitch attitude of approximately 24 degrees above horizontal after becoming airborne. Approximately 42 seconds after start of film, a sound resembling the aircraft stall warning horn was recorded on the tape audio. At about this point, the tape video became unusable. All data from the tape ceased at about 49 seconds after start of film. The tape audio did not record any significant change in the pitch of the engine noise during the accident sequence. FAA investigators who responded to the accident reported that the airplane's electrically actuated flaps were fully down at the accident scene. The flap switch (Cessna part number MS25201-5) was subsequently removed from the aircraft and sent to Cessna for functional testing under supervision of the FAA Aircraft Certification Office in Wichita, Kansas. During functional testing, the switch exhibited proper electrical operation but improper mechanical operation. The switch, which incorporates a spring-return mechanism to return it to the neutral position upon being released from the extend position, did not return to neutral after being released. The switch was disassembled to determine the nature of this malfunction. Cessna reported that "it was concluded that, due to normal wear, the springs had deformed slightly and allowed the switch rod to avoid proper contact with the springs." Cessna also reported that the malfunctioning switch was a proper installation on the accident aircraft. There was no information provided on the pilot's accident report regarding the time in service on the switch or the airframe. The aircraft was a 1974 model according to the FAA aircraft registry. The 1974 Cessna 172M owner's manual indicates the following power-off/aft center-of-gravity stall speeds for zero bank angle and 2,300 pounds gross weight: 57 MPH calibrated airspeed (CAS) with flaps up, 52 MPH CAS with flaps extended 10 degrees, and 49 MPH CAS with flaps fully extended at 40 degrees. The maximum rate-of-climb data in the owner's manual indicated that at 2,000 pounds gross weight (the estimated gross weight based on the aircraft loading reported by the pilot), 4,316 feet altitude, and 80 degrees F, the aircraft's climb rate is 568 feet per minute at an indicated airspeed of 82 MPH. The maximum rate-of-climb chart specifies flaps up, full throttle, and mixture leaned for smooth operation above 3,000 feet. The leaning procedure prior to takeoff from fields above 3,000 feet elevation, according to the manual, is to lean the mixture "to give maximum RPM in a full throttle, static runup." The engine's normal operating speed range at 5,000 feet, according to the manual, is 2,200 to 2,600 RPM. A state airport directory printed on the back of the Utah state aeronautical chart indicated an uphill grade of 0.81% on runway 34 at Tooele Valley. A copy of the airport sketch in the FAA airport master record (FAA Form 5010) on file at the FAA Northwest Mountain Region Airports Certification Office in Renton, Washington also indicated an 0.81% uphill grade on runway 34. However, a query of an airport database maintained on a World Wide Web (WWW) site at Georgia Tech University indicated, based on the elevation given for each end of the runway, that the average runway slope was 0.81% uphill on runway 16. The Georgia Tech WWW airport data is prominently annotated "USE AT YOUR OWN RISK" but cites the FAA's National Flight Data Center as its data source. The WWW site indicated that its airport information was current as of December 5, 1996. The surveyor for the Salt Lake Airport Authority, which operates Tooele Valley Airport, verified by telephone on December 23, 1996, that the runway elevation data at the Georgia Tech WWW site was accurate and that the runway slope is overall uphill from north to south. The U.S. Government Airport/Facility Directory (A/FD) does not contain runway slope information for the airport. The A/FD legend states that "Runway slope will be shown only when it is 0.3 percent or more."
failure of the flight instructor (CFI) to ensure that adequate airspeed was maintained during initial climb after lift-off, which resulted in an inadvertent stall/mush. High density altitude was a related factor.
Source: NTSB Aviation Accident Database
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