NTSB Factual Report

On August 7, 2001, about 1552 eastern daylight time, a Mooney M20C, N78933, registered to a private individual, experienced a loss of engine power shortly after takeoff and minimally damaged a vehicle and a Broward County bus during a forced landing on a road. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 instructional flight. The airplane was substantially damaged and the certified flight instructor/airplane owner (CFI) and private-rated student sustained minor injuries. The bus was not structurally damaged and the driver and five passengers were not injured; two passengers on the bus sustained minor injuries. The vehicle was not structurally damaged; the driver and one passenger sustained minor injuries. The flight originated about 3 minutes earlier from the Fort Lauderdale Executive Airport, Fort Lauderdale, Florida.

The CFI stated that he flew into the Fort Lauderdale Executive Airport for the purpose of going to a pilot shop and after going there, performed a limited preflight based on the uneventful flight and the short duration after landing. The airplane was taxied using only the engine-driven fuel pump, and an engine run-up was performed before takeoff with no discrepancies noted. An intersection takeoff was performed from runway 13 which provided for 3,000 plus feet of remaining runway. The pilot-rated left seat occupant performed the takeoff with 20 degrees of flaps extended and the boost pump on. When no usable runway remained for landing, the landing gear was retracted. The flight continued and at approximately 400 feet mean sea level, the left seat pilot turned off the boost pump; the engine, "...experienced the initial loss of power." The CFI took control of the airplane and visually verified the positions of the magneto switch, master switch, and fuel pump. The auxiliary fuel pump which was previously turned off was turned on, and the CFI pushed the throttle, mixture, and propeller controls forward; the throttle control was, "slightly retarded." He noted that the manifold pressure was indicating 17 or 18 inHg, and advised air traffic control of the loss of engine power. Unable to return to the departure airport, he maneuvered the airplane and attempting to restore engine power by pumping the throttle feeling, "...minimal resistance." He leaned the fuel/air ratio, with no effect. While flying near a highway, he noted that the manifold pressure was indicating 15 inHg. Unable to land on the highway due to congestion, he maneuvered the airplane for a forced landing on a roadway and pulled the throttle to idle, reporting later, "Nothing changed." While descending with the landing gear retracted, a portion of the airplane lightly contacted and damaged soft material on the roof of the car; no structural damage to the car was noted. He performed a full-stall landing and the airplane impacted the ground. While sliding on the ground, the right wingtip collided with the rear bumper of the bus; no structural damage to the bus was noted. The airplane came to rest upright approximately 523 feet from the initial touchdown point on the road. The airplane was recovered without removing any components.

Examination of the airplane revealed the throttle lever with attached throttle cable was separated from the carburetor; no evidence of safety wire was present in the hole of the securing screw of the throttle lever, on the lever, or on the throttle stop. Both propeller blades were damaged. A sufficient quantity of fuel were found in both fuel tanks; no contaminants were noted. No repairs were performed to the engine which remained installed on the airframe. Using the airplanes fuel system, the engine was started and operated to 2,000 rpm using only the engine-driven fuel pump; safety concerns pertaining to the damaged propeller blades precluded operating the engine at a higher rpm. Both propeller blades were cut to approximately the same length, removing the damaged portion of the blades. The engine was started and operated to maximum red line indication using only the engine-driven fuel pump.

Airworthiness directive (AD), 72-06-05 Revision 2, with an effective date of July 3, 1986, indicates in part that for the model of carburetor installed, to torque the throttle arm clamping screw to 20 to 28 inch pounds and to safety the clamping screw to the throttle arm and throttle stop as depicted in the illustrations. A copy of the AD is an attachment to this report.

An AD list included with the maintenance records indicates that AD 72-06-05 Revision 2 was signed off as being accomplished on January 10, 2000. The method of compliance was listed as, "[complied with] at [overhaul]." Review of the maintenance records revealed that the carburetor was signed off as being overhauled on February 21, 2000. Copies of the AD list and maintenance entry are an attachment to this report.

Calculations performed using an NTSB program determined the propeller rpm at touchdown was 1,566. The calculations are based on the distance between the first and second ground scars on the road made by the propeller (21.5 inches), a two-bladed propeller installed, and stall speed at touchdown. A copy of the document prepared is an attachment to this report.

The airplane minus the retained carburetor was released to David E. Gourgues, liability specialist for LAD (Aviation) USA, on October 11, 2001. The retained carburetor was also released to David E. Gourgues, on October 12, 2001.

NTSB Probable Cause

The failure of the mechanic who installed the carburetor after overhaul to safety the throttle linkage at the carburetor per an Airworthiness Directive resulting in separation of the throttle linkage and subsequent partial loss of engine power. Contributing to the accident was the unsuitable terrain encountered by the pilot-in-command during the forced landing.