This December 2008 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Piper Cherokee. Injuries: 3 Serious. Location: Kapolei, Hawaii. Aircraft damage: Substantial.
What reportedly happened: The airplane was level at 1,500 feet MSL when the flight instructor had the private pilot receiving instruction reduce power and glide towards the runway for a touch-and-go. The CFI said they did not use carburetor heat nor did they clear the engine during the glide. The pilot landed the plane, then advanced the throttle for takeoff. Immediately after liftoff, the flight instructor noted that the engine was not producing full power. He took control of the airplane, checked the engine instruments, fuel tank selector position, and fuel pressure, and confirmed that the throttle and mixture controls were full forward. The CFI did not apply carburetor heat. The airplane did not have enough power to reach an altitude that would allow it to avoid obstacles at the end of the runway. The Piper collided with trees and a power line.
During the post-accident examination no airframe or engine pre-impact mechanical discrepancies that would have prevented normal operation were found. The fuel tank selector valve was found slightly out of the detent for the right tank position, but it still offered about 80% of the normal opening for fuel to pass. According to the engine manufacturer, carburetor ice can form under a relative humidity of 50% to 60% with any outside air temperature from 20° to 90° Fahrenheit. The calculated relative humidity at the time of the accident was 79%. A carburetor icing probability chart indicated that the conditions were in the range for serious icing at glide power. Investigators determined that the partial loss of engine power was likely a result of the formation of carburetor ice.
Probable cause: The partial loss of engine power during the initial climb due to the failure of both pilots to use carburetor heat during a long descent for landing in carburetor icing conditions and the flight instructor’s inadequate supervision of the flight.
For more information: NTSB.gov