HOUSTON, TX, USA
N6846E
Cessna 175A
During cruise flight at full throttle and engine rpm at 2,700 to 2,800 (maximum 3,200 rpm), the engine ran rough. As the engine rpm and oil pressure decreased, emergency procedures performed by the flight instructor did not restore engine power. During the forced landing in a wet field, the nose gear collapsed and the airplane nosed over to an inverted position. This was the flight instructor's first flight in this make and model of aircraft. Before takeoff, the left magneto drop was beyond the 125 rpm maximum drop allowable. The last annual inspection was conducted in April 1997 at a tachometer reading of 1,956.59 hours. The tachometer reading at the time of the accident was 1,995.61 hours. A teardown of the engine revealed a hole in the #6 cylinder piston, and separation of the rod cap and bolts for the #3 cylinder connecting rod. The components of the #3 connecting rod exhibited overload features. The #6 cylinder piston exhibited physical evidence of detonation or preignition.
On December 13, 1997, at 1210 central standard time, a Cessna 175A single engine airplane, N6848E, nosed over during a forced landing following a loss of engine power near Houston, Texas. The airplane was owned and operated by a private owner under Title 14 CFR Part 91. The student pilot and his commercial pilot/flight instructor received minor injuries and the airplane sustained substantial damage. Visual meteorological conditions existed for the local instructional flight that departed the David Wayne Hooks Airport at 1150. A flight plan was not filed for the flight. During telephone interviews, conducted by the investigator-in-charge (IIC), and on the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), the flight instructor reported that he had the student conduct the preflight inspection using a Cessna 172 checklist while the flight instructor followed the Cessna 175 manual for any differences. This was the flight instructor's first flight in a Cessna 175 airplane. During the "Before Takeoff Checklist" the left magneto drop was approximately 200 rpm. The flight instructor leaned the mixture for a couple of minutes and then performed the magneto check again, and with the left magneto "there was now only an approximate drop of 100 rpm (within the 125 max[imum] drop allowable) and still a little roughness of the engine, but when running on both magnetos the engine ran smooth." The takeoff on runway 35L and the climb out were at an engine rpm of 2,700 to 2,800. The airplane was in level flight at 1,500 feet msl approximately 8 to 10 miles west of the departure airport, when the instructor noted a drop in the engine rpm and the oil pressure. The student pilot turned the airplane toward the departure airport while the flight instructor performed the emergency procedures; however, increasing or decreasing the controls in the cockpit, had no effect on the engine power. The engine power continued to decrease, the engine quit, and the propeller stopped rotating at approximately 200 to 300 feet agl. The flight instructor took the controls and turned the airplane toward the May Field Airport; however, the airplane landed short in a soft, wet grassy field. During the forced landing roll, in the wet field, the nose gear collapsed and the airplane nosed over coming to rest inverted. The flight instructor and student exited the airplane. The left wing, right wing, vertical stabilizer, and firewall sustained structural damage. During telephone interviews, conducted by the investigator-in-charge, the student pilot reported that he conducted the preflight inspection using a Cessna 172 checklist while the flight instructor followed the Cessna 175 checklist. During the run-up at 2,000 rpm, there was "around a 250 to 300 rpm drop and rough running on one side [magneto] and around 75-100 on the other side." The instructor made "some adjustments to unfoul the plugs" and the magneto drop was then "about 200 to 250" rpm. The student stated that the flight instructor said "we should have this checked out, but we are both eager to fly today so what do you say?" The student pilot agreed that he was eager to fly. The aircraft was cleared for takeoff and during the climb out the student and the flight instructor commented to each other about how "rough the engine was running." The flight instructor had the student pilot continue to fly the airplane westbound away from the departure airport. Approximately 10 minutes into the flight, the engine started to lose power and oil pressure. The FAA inspectors examined the airplane and the maintenance records. They reported that the airplane was manufactured in 1959 and received the original airworthiness certificate on November 28, 1959. With a tachometer time of 1,799.6 hours, the airplane was stored from 1976 through 1994. In 1995, the airplane was returned to service, and on May 5, 1995, the tachometer reading was 1,835.1 hours. The tachometer reading at the time of the accident was 1,995.61 hours. The last annual inspection was performed on April 5, 1997, at a tachometer reading of 1,956.59 hours. A review of the owner's manual by the IIC, revealed that the maximum [full throttle] tachometer reading is 3,200 rpm. The maximum recommended cruise rpm at sea level is between 2,400 and 2,900 rpm. A teardown of the engine, a Continental GO-300-C, S/N 12536-0-C, under the surveillance of the FAA inspectors, revealed metal in the engine oil screen, a hole in the top of the piston for the #6 cylinder, and separation of the rod cap and bolts for the connecting rod of the #3 cylinder. The failed components of the #3 connecting rod exhibited overload. The piston from the #6 cylinder was examined at the engine manufacturer's facility, under the surveillance of the FAA, in Mobile, Alabama, in April, 1998. According to the engine manufacturer, the piston exhibited physical evidence of detonation or preignition.
The total loss of engine power resulting from detonation and the ensuing failure of the engine piston and connecting rod components. Factors were: the instructor's decision to take off with a known deficiency (magneto drop over limit), the flight instructor's lack of familiarity with the aircraft, and the lack of suitable terrain for the forced landing.
Source: NTSB Aviation Accident Database
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