Southern Pines, NC, USA
N4022P
Harpster Hawk Aero Tandem
The experimental amateur-built Hawk Aero Tandem airplane sustained substantial damage during an emergency landing following a loss of engine power during cruise. The pilot stated that he had lost engine power after restarting the engine twice. He impacted a mound with his nose landing gear. A witness saw liquid in the fuel tank when the airplane was disassembled. The airplane was powered by a Hirth 2706 fuel-injected engine. The Blue Max two cycle oil's recommended fuel and oil ratio was 100:1. An engine manual supplement noted that the recommended fuel and oil mixture was 90:1 for fuel injected engines. The pilot reported that he used a 100:1 fuel/oil ratio. A representative of the engine repair facility stated, "This engine experienced a piston seizure of the mag[neto] end piston. ... The PTO side piston is undamaged and from inspection of this cylinder it appears that possibly there was too lean of an oil mix in the fuel."
On June 18, 2007, about 2015 eastern daylight time, N4022P, an experimental amateur-built Harpster Hawk Aero Tandem airplane, piloted by a private pilot, sustained substantial damage during an emergency landing following a loss of engine power during cruise near Southern Pines, North Carolina. The personal flight was operating under 14 CFR Part 91. No flight plan was on file. Visual meteorological conditions prevailed at the time of the accident. The pilot and passenger reported no injuries. The local flight originated from Moore County Airport, Pinehurst/Southern Pines, North Carolina, at approximately 2000. The pilot's statement to a Federal Aviation Administration Inspector, in part, stated: The airplane had 178 hours on it as of December of 2006. At that time, I pulled the engine and shipped it to the distributor, Recreational Power, to have some work done. I had been having problems with harmonics at certain RPM ranges. They discovered some internal problems and ended up rebuilding the entire engine. I flew the plane for the first time this year on March 7. Since then, I have flown with the rebuilt engine for 11.1 hours, and it had been running great. This was a big improvement. On Monday, my neighbor, ... asked me to take him flying. We had been up for about 40 minute when, for no apparent reason, the engine quit. I looked around and spotted a large soccer field that I could land on. After turning in that direction, I managed to restart the engine. We had lost about 400 feet of altitude (from 1200' msl to 800'). I immediately started to climb and turned towards the Moore County Airport, where I am based. We were only about five miles away. After maybe 45 seconds, the engine quit a second time. I lined myself up with a hole on Midsouth golf course, which was straight in front of me and attempted to restart the engine. The engine did start a second time, but again, I had lost several hundred feet of altitude. By this time I was over the tee box of the course and only a couple of miles for the airport. I attempt to climb again but the engine quite after only about fifteen seconds. By this time I had traveled more than half the length of the fairway and had climbed a hundred feet or so requiring me to make a very short field landing. I also had sand traps and mounds directly in front of the green. I was able to put the plane on the ground but struck one of these mounds collapsing the nose gear on the front of the plane and bending the tail section; both which I can repair. The Fire Marshal for the Southern Pines Fire/Rescue department stated that liquid was observed in the airplane's fuel tanks when the airplane was disassembled. N4022P was registered as an experimental amateur-built Harpster Hawk Aero Tandem airplane, serial number H1143-A-TRI-2706. The engine was a two cycle, two cylinder, fuel injected, 65-horsepower Hirth 2706, serial number 895816. The engine drove a three-bladed Ivoprop, serial number 11R2200. The website for the repair facility that had rebuilt the engine stated that the Blue Max two cycle oil's recommended fuel and oil ratio was 100:1. An engine manual supplement noted that the recommended fuel and oil mixture was 90:1 for fuel injected engines. The website contained an engine description which, in part, stated: 2706 incorporates Al-Nikasil coated cylinders for superior performance and reliability. Al-Nikasil in simple terms is a nickel based material, applied in a paste form, when super heated it becomes part of the cylinder itself. Al-Nikasil provides for a super low coefficient of friction, reducing engine heat and wear. The pistons and cylinders expand at the same rate thus providing for a seizure resistant engine. 2706 crankshaft is 4130 chromemolly steel. Heads, cylinders, rings, block casting, connecting rods and associated components are all of the highest grade alloys available. The pilot, in part, reported: The way I handle my fuel is simple. I have a gas caddy that holds thirty gallons. I also have a platform that plugs into the hitch receiver on my vehicle. When I need fuel, the gas caddy is laid flat on the platform, and I drive about five miles to an Exxon station where I buy my fuel. At this time I add one quart of Bluemax two cycle oil to the caddy with twenty five gallons of 93 octane gas. My mixing [ratio] is 100-1. The oil is the manufactures recommended oil. I never buy more or less than the twenty five gallons and the oil colors the gas green. The five mile drive back to the airport well mixes the oil and gas. This is the procedure I have followed since I built the plane six years ago. The engine was shipped to the repair facility. A representative of the facility stated: This engine experienced a piston seizure of the mag[neto] end piston. As customer re started engine 2 times after initial seizure it is not possible to determine exact cause because of extensive damage done to piston by the re starts. The PTO side piston is undamaged and from inspection of this cylinder it appears that possibly there was too lean of an oil mix in the fuel.
The loss of engine power during cruise due to the piston seizure for undetermined reasons and the unsuitable terrain the pilot encountered during the forced landing. A factor was the rising terrain of the mound that the airplane impacted.
Source: NTSB Aviation Accident Database
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