The pilot reported that, while maneuvering the Cessna 180B on floats about 2,500 feet above ground level, he heard a “slight squeal” coming from the engine before it started to sputter.
After the plane had descended to about 1,500 feet, the engine and propeller “completely stopped.”
The pilot determined that the plane would not reach a nearby lake and chose an unpaved road in the woods near Piscataquis County, Maine, for the forced landing.
The right wing hit a tree about 60 feet above the ground, and the plane then hit the road, which resulted in substantial damage to the wings, fuselage, and empennage.
Examination of the engine revealed that the crankshaft could be rotated freely by hand, and removal of the oil sump revealed piston material and the No. 3 exhaust valve head, which was fractured at the stem below the head.
Disassembly of the engine revealed normal wear and appearance on all of the cylinders except for the No. 3 cylinder, piston, and exhaust valve.
Metallurgical examination of the No. 3 exhaust valve revealed that the fracture had initiated at the outer surface of the valve stem and that the valve had fractured due to fatigue at the transition of the stem to the valve.
The NTSB determined the probable cause as the fatigue fracture of the No. 3 exhaust valve, which initiated at the outer surface of the valve stem and resulted in the subsequent total loss of engine power over terrain unsuitable for landing.
NTSB Identification: ERA14LA446
This September 2014 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.
I guess I don’t understand why the engine stopped. I was flying at low altitude in my C-172 with the Continental O-300-145 rock crushing HP-when the number 5 exhaust valve broke halfway down the stem. I was immediately able to detect *something* was wrong, since the engine felt like it was trying to shake itself off the mounts! After checking everything that might possibly have been the source of the problem, I simply pushed the throttle full in and even with three grown men on board it was able to climb ~200 feet/minute. Fortunately, an airport was only about 8 miles away, the engine continued to run and allowed me to make a normal landing. The engine stopped only when I shut it down. The non-pilot pax in the right seat is an engineer at Honda and wanted me to do some additional tests with the engine running. I think one of their practices is to run something to complete failure, then analyze what went wrong so they can strengthen or fix the failure. I shared with him that my personal R&D budget was not on the same scale as Honda, and if I could prevent any *further* damage to the engine, I wanted to salvage what I could! As it turned out, the end of the valve and some of the stem welded/bonded to the face of the piston and then slammed against the top of the jug on each revolution, causing plenty of vibration, as well as not producing any power. Of course, it resulted in a complete teardown of the engine, and considering it was 400 hours from TBO, a major overhaul was performed. I am mystified as to how/why something like this happens on a low compression, low RPM engine, but I am thankful to the folks at Continental for building an otherwise very tough engine!
POOR HEADLINE……………… engine failure did not bring down the aircraft…………… GRAVITY brought down the aircraft………. as it always does !!!!!!!!
You are not helping the normal aviator by making such statements…..
An engine failure causes the pilot to use the skills that they are supposed to have to determine how the flight will end……… but GRAVITY is what brought the aircraft down…. where it came down is dependent and multiple variables… one of which is if the engine is producing sufficient power or not….. but again… it is GRAVITY…. as each pilot learned in the first hour of ground school.
Please……… editors, writers……… think about what your are stating…. and ask this questions each time you are going to publish an article………ARE YOU A PART OF THE PROBLEM OR ARE YOU A PART OF THE SOLUTION?
Took me a couple of times reading this for it to sink in. \
“Examination of the engine revealed that the crankshaft could be rotated freely by hand, and removal of the oil sump revealed piston material AND THE No. 3 EXHAUST VALVE HEAD, which was fractured at the stem below the head.”
The only way the exhaust valve head could end up in the oil pan is THROUGH the piston! So after breaking off the valve head beat a hole in the piston to get into the oil pan.