NTSB Identification: NYC97FA011.
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Accident occurred Sunday, October 27, 1996 in BERLIN, NJ
Probable Cause Approval Date: 10/31/1997
Aircraft: Yakovlev YAK-18T, registration: N9418
Injuries: 2 Fatal,1 Serious.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The airplane was on a demonstration flight with a prospective buyer in the left front seat & the co-owners in the right front & a rear seat. A witness said the airplane was above the airport when a puff of white smoke came from the exhaust, & the engine lost power. The gear was extended, & the pilot(s) entered a left turn to circle & descend for a forced landing at the airport. The left seat pilot said the right seat pilot abandoned the controls, saying 'You have it.' He also said that before entering an uncontrolled descent, the right seat pilot yelled, 'We're not going to make it,' then he grabbed the controls, yanked back, and the airplane half snap rolled & dove into trees. However, a ground witness said the airplane descended until it impacted a tree, while still in a left spiral. Exam of the engine revealed 3 broken connecting rods & a shattered #5 piston. The piston had failed in compression & showed polished edges & distress associated with hydraulic lock. Operating instructions required that spark plugs & drain plugs be removed from the #4, #5, & #6 cylinders before turning the propeller to prevent hydraulic lock (if parked more than 3 days). A witness said the owners started the radial engine every couple of weeks without removing anything from the engine. A factory trained engine technician said there was evidence '...the engine was started without the operator having first checked for the presence of oil in the lower cylinders as is described in the aircraft operating instructions.'

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

an inadequate preflight by unknown person(s), sometime before the flight, by failing to avoid a hydraulic lock (from oil seepage) in the #5 cylinder, which resulted in a bent connecting rod, subsequent failure of the #5 piston, and loss of engine power. Also causal was: the flight crew's failure to maintain adequate control of the aircraft and/or clearance from a tree, while maneuvering for an emergency landing.

Full narrative available

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