TRENTON, GA, USA
N30236
Piper J3C-65
The pilot stated that during the takeoff roll, he forced the aircraft off the runway, because he mistook a midspan crest on the runway as the departure end, and because other similar aircraft became airborne at that particular point. The premature rotation caused the aircraft to become airborne in ground-effect, but it would not climb. It settled into trees about 100 yards beyond the airport boundary. The pilot further stated that he never saw over 2050 rpm throughout the takeoff run. The tachometer was subsequently found to be reading higher than actual engine rpm; at an indicated 2050 rpm, actual rpm was approximately 1650. The type-certificate data sheet indicated the redline was at 2350 rpm and minimum static was 1950 rpm. The pilot stated that he installed the tachometer sometime between 'Sun' n' Fun' of 1996 (where he thought he bought the tachometer) and 11/25/96 (when the aircraft was annual-inspected).
On October 4, 1997, about 1253 eastern daylight time, a Piper J-3C-65, NC30236, registered to a private individual, collided with power lines during takeoff from a private airstrip near Trenton, Georgia. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR 91 personal flight. The airplane was substantially damaged, and the private-rated pilot as well as the non-rated passenger were not injured. The flight originated one minute before the accident. The pilot stated that during the takeoff roll, he attempted rotation at about the same spot on the 1800 ft. grass strip that other identical aircraft had become airborne, but his aircraft would not fly. Further down the runway, the aircraft did become airborne, but with down-sloping terrain, the aircraft wouldn't climb, impacted power lines, and descended into "cleared brush.". The pilot stated that takeoff power on this day never exceeded 2200 RPM, that he mistook the crest of the runway for the departure end, and that when he reached the crest and saw how much runway remained, 476 feet, he probably should have aborted the takeoff. The undamaged engine, still installed on the airframe, was started under FAA observation using the same mixture of aviation and automotive gas onboard the day of the accident. Additionally, a digital-strobe tachometer was used, and the following was noted: Installed Tach Setting Strobe Tach Setting 1000 RPM 770 RPM 1700 RPM 1370 RPM 2200 RPM 1730 RPM 2350 RPM (REDLINE) 1870 RPM 2600 RPM (FULL THROTTLE) 2070 RPM The pilot stated that sometime between "Sun' n' Fun" of 1996, where he thought he bought the tachometer and November 25, 1996, when the aircraft was annual-inspected, he installed the tachometer. Review of the aircraft type-certificate data sheet for the installed engine/propeller combination reveals that under static conditions, the minimum rpm at full throttle should be 1950rpm.
failure of the pilot to abort the takeoff, when he observed an indication of less than full engine power on the tachometer from the beginning of the takeoff roll. Factors relating to the accident were: the inadequate preflight planning and preparation by the pilot by failing to know the available runway remaining for an abort maneuver, faulty reading on the tachometer, and trees near the end of the runway.
Source: NTSB Aviation Accident Database
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