WAYNESVILLE, OH, USA
N37SK
Jordan KITFOX MODEL 1
Shortly after take-off, a partial loss of engine power occurred, and the pilot was unable to maintain altitude. The airplane collided with trees and a fence before coming rest on the ground. Examination of the two-cycle Rotax engine and the forward Bing carburetor revealed that the jet needle had broken and was blocking the mixing tube. Two Rotax service information documents addressed the wearing of the jet needle, due to the needle clip rotating from vibrations. One document called for an immediate check of the jet needle and needle clip for wear, followed by a 50-hour check thereafter. The second notification stated that the jet needle should be replaced every 150 hours. A Bing service alert stated that if an o-ring had not been installed, the needle clip should be inspected every 10 hours for signs of wear. The pilot was not aware that an o-ring would prevent wear on the jet needle until after the accident. The pilot reported the engine had a total of 417 hours, and the jet needles and clips were replaced at the 200-hour inspection. The pilot also stated that the components were checked for wear 36 hours prior to the accident.
On August 25, 2000, at 1845 Eastern Daylight Time, a homebuilt Kitfox Model 1, N37SK, was substantially damaged when it collided with trees darting a forced landing, shortly after take-off from the pilot's private airstrip in Waynesville, Ohio. The certificated private pilot/owner/builder sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight conducted under 14 CFR Part 91. In a telephone conversation, the pilot said: "I did a normal pre-flight. The wind was calm and I taxied to the south end of the strip for a northerly departure. I did an engine run-up twice, and all checklist items for take-off were normal. It was a normal take-off, where after lift-off I held the airplane level and built up airspeed. Just below 100 feet in altitude, the engine power went to idle. In about 5-7 seconds, the engine was still turning and producing about 40-50 percent power. "I put the nose over to maintain airspeed and made a slight 20 degree turn to the left. I was about 50-60 feet above tree level at this point. I turned another 60 degrees to the left to avoid houses and was parallel to the tree line. The left wing contacted a treetop. The wings stayed level and the nose at this point was approximately 30-35 degrees nose down. The left wing hit a fence post. The wing, landing gear, and nose hit the ground all at the same time. The aircraft turned almost 180 degrees around and came to rest in a level attitude. The fuel pick up line was broken and a large amount of fuel was spilling from the airplane." A Federal Aviation Administration (FAA) inspector performed an on-scene examination on August 29, 2000. In a written report, the inspector said: "The aircraft wreckage was removed from the scene and placed in the [pilot's] hangar, which was approximately 75 yards from the accident site. Inspection of the wreckage revealed the following: The cockpit forward of the leading edge of the wings was broken and bent down. The landing gear was broken and bent aft and under the fuselage. The left wing leading edge was dented outboard of the lift strut. The propeller blades were broken at the hub. "The accident site had gouges in the ground from the landing gear and propeller. The grass around the site was brown and smelled of gas. Inspection of the maintenance records revealed that the last condition inspection was performed in October, 1999." With permission from the Safety Board, the pilot performed an engine examination. When the pilot removed the forward carburetor, he found that the jet needle had worn/broken away and had lodged into the mixing tube, thus shutting off fuel flow into the carburetor. Examination of the other carburetor's jet needle also revealed signs of wear. The pilot reported that the engine had a total time of 417 hours. He replaced both jet needles and needle clips at the 200-hour inspection. The pilot stated that he last checked these components 36 hours prior to the accident and did not find any indications of wear. The engine was a 2-cycle ROTAX 532 with a Bing Model 54 carburetor. In 1991, ROTAX released two Service Information (SI) documents that addressed the jet needle valve. The Service Information documents were SI-03-1991, and SI-08-1991. SI-03-1999 was issued as a daily pre-flight check-maintenance plan for all ROTAX UL-engines. According to the maintenance plan, item #22 stated that the carburetor(s) should be checked for wear every 50 hours. Item #23 stated that the jet needle be replaced every 150 hours. SI-08-1991 stated: "Premature wear on carburetor parts e.g. jet needle, needle clip, and float can cause engine troubles, engine stoppage or emergency landing. Critical are those cases, where the jet needle rotates because of vibrations, caused by a loose fit of the needle clip." SI-08-1991 called for an immediate check of the jet needle and needle clip for wear. After the immediate check was performed, the jet needle and needle clip should be checked every 50 hours of operation. A Bing service alert stated: "ATTENTION. If your carburetor does not have the New Style Cup (827-347) and Jet Needle O'Ring (831-715), you must check your Needle Clip (963-500)! Place your Jet Needle in the proper setting. If the needle spins freely, ACTION MUST BE TAKEN! Remove the clip and hold the clip up to the light. If the needle is reduced at the clip position, REPLACE. If not, offset sides of clip and use emery 240 paper or a fine file on each side until light shows between. Carefully squeeze clip together with pliers. Insert needle in clip and try again. Repeat until needle does not spin freely. Needle must show a resistance to spinning. CHECK EVERY 10 HOURS!" When asked how this accident could have been prevented, the pilot stated: "Install [California Power Systems] part no. 963-505 (o-ring). This part installed on jet needle should prevent it from spinning, thus it should keep the jet needle from cutting itself on the needle clip. I only found out this part existed after looking in the California Power Systems 2000 parts catalog." The pilot/owner/builder reported 520 total flight hours, of which 417 hours were in his Kitfox, N37SK. According to FAA Advisory Circular AC 20-27D, Certification and Operation of Amateur-Built Aircraft, "the amateur-built program was designed to permit person(s) to build an aircraft solely for educational or recreational purposes. The FAA has always permitted amateur builders freedom to select their own designs. The FAA does not formally approve these designs since it is not practicable to develop design standards for the multitude of unique design configurations generated by kit manufacturers and amateur builders." According to ROTAX 532 UL engine manual, a warning is issued to users of the engine. The warning stated: "This is not a certificated aircraft engine. It has not received any safety or durability testing, and conforms to no aircraft standards. It is for use in experimental, uncertified aircraft and vehicles only in which an engine failure will not compromise safety.' "User assumes all risk of use, and acknowledges by his use that he knows the engine is subject to sudden stoppage."
A broken carburetor jet needle, which blocked fuel from entering the carburetor's mixing tube and resulted in a partial loss of engine power.
Source: NTSB Aviation Accident Database
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