Incident Overview
During a cross-country flight with a certified flight instructor, the pilot noticed a reduction in manifold pressure while climbing through 16,000 feet mean sea level. Advancing the throttle temporarily increased pressure by one or two inches, but shortly thereafter a loud bang was heard from the engine, followed by an immediate loss of engine power.
Troubleshooting and Diversion
The pilot and flight instructor attempted to troubleshoot the issue. The engine seemed to respond with the low boost engaged but ran rough whenever the throttle was advanced more than halfway. They diverted to a nearby airport and began an emergency descent. While descending through an overcast cloud layer, the pilot aimed to enter the airport traffic pattern.
Approach and Landing
On final approach, the pilot believed the airplane was high and extended the landing gear and flaps. Shortly after, airspeed and altitude decreased drastically, and the pilot realized the aircraft was too low. Applying the throttle produced no change in engine performance. The aircraft struck a fence and landed hard in an open field just short of the airport, resulting in structural damage to the fuselage and wings.
Postaccident Examination
Examination of the engine revealed that the induction elbow for cylinders 1-3-5 (right side) was displaced from the throttle and metering assembly. The induction hose and clamp were secure on the hose, but the clamp was positioned on the inboard side of the retention bead rather than beyond it, as required.
Maintenance History
Review of the aircraft maintenance logbooks showed that cylinders 4 and 5 had recently been replaced due to low compression. This replacement required removal of the induction system. A manufacturer service bulletin specified that during reinstallation, the induction hose and clamp(s) must be slid onto one tube, with both tube beads centered in the hose and the clamp positioned between the bead and the end of the hose.
Probable Cause
The official probable cause is a loss of engine power due to the in-flight separation of the 1-3-5 cylinder induction tube elbow, which was caused by the improper installation of the induction tube elbow by maintenance personnel.