What happened
During a cross-country flight involving a pilot and a certified flight instructor, the aircraft type was ascending through 16,000 feet MSL when the pilot detected a drop in manifold pressure. Although advancing the throttle briefly restored some pressure, a loud bang was heard from the engine, followed by an immediate loss of power. The crew attempted to troubleshoot the engine, noting that while the engine would run with low boost, it ran poorly whenever the throttle was advanced past the halfway point.
The crew initiated an emergency descent and diverted to a nearby airport. While attempting to enter the traffic pattern through an overcast layer, the pilot extended the landing gear and flaps to correct a perceived high approach. This caused a drastic loss of airspeed and altitude. Despite attempts to apply power, the engine failed to respond. The aircraft subsequently struck a fence and impacted an open field just before reaching the airport, resulting in structural damage to the fuselage and wings.
Findings
An inspection of the engine following the accident revealed that the induction elbow for cylinders 1-3-5 had become displaced from the throttle and metering assembly. While the clamp remained secure to the induction hose, it was not positioned correctly relative to the retention bead on the assembly.
Maintenance records indicated that cylinders 4 and 5 had been recently replaced due to low compression, a procedure that required the removal and reinstallation of the induction system. The investigation found that the improper installation of the induction hose clamp failed to follow manufacturer service bulletin instructions, which require the clamp to be centered between the tubing bead and the end of the hose to ensure a secure connection.