N6171RRans S-17 · 2001

On May 4, 2013, about 1109 Pacific daylight time, a Rans S-17 experimental light sport airplane, N6171R, was substantially damaged during a forced landing near a construction site in Fontana, California. The pilot received minor injuries. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the flight.

According to the pilot, he was planning to purchase the airplane from a colleague, and was relocating it to his home airport when the accident occurred. The pilot departed Brian Ranch airport (CL13), Palmdale, California, about 0930, with an intended destination of Brackett Field airport (POC), LaVerne, California. He climbed to an altitude of 5,500 feet, and flew through the Cajon Pass via the Cajon Pass visual checkpoint depicted on the Los Angeles sectional aeronautical chart. As he approached the southern end of the pass, the engine began to lose power, with the maximum speed decreasing to about 4,500 rpm. The pilot was unable to maintain altitude, and initially believed that he could reach Rialto Municipal Airport (Miro Field, L67), Rialto, California, which was located about 8 miles south of his current position. He verified that the ignition systems seemed to be functioning normally, and confirmed that the cylinder head and exhaust gas temperatures were below their maximum limits. Maximum available engine rpm continued to decrease, to about 2,000 rpm. Shortly thereafter, the pilot realized that he would be unable to reach L67, and then planned for an off-airport landing on a dirt road near a construction site. When the airplane was about 200 feet above ground level, the engine ceased operating. During the "steep descending turn" from base leg to final, the airplane "lurched sharply and descended vertically" to the ground; the airplane had struck an unseen guy wire that was present in the pilot's selected landing area.

A representative of the Federal Aviation Administration (FAA) responded on-scene to the accident. He determined that there was a combined quantity of about 8 gallons of fuel in the two fuel tanks, and that there were no obvious irregularities with the engine. The owner of the airplane also responded to the accident site, and for safety reasons, he removed the rocket-equipped parachute recovery system from the airplane. The wreckage was transported to POC for a subsequent detailed examination by the NTSB and FAA.

The pilot held an airline transport category certificate, as well as multiple other certificates and ratings. He reported that he had about 8,232 total hours of flight experience, including about 1 hour in the accident airplane make and model. His most recent FAA second-class medical certificate was issued in March 2012.

According to FAA information, the airplane was manufactured in 2001, and was equipped with a Rotax 503 series engine. The engine was manufactured in 2000, and was mounted in a pusher configuration below the high-mounted, fabric-covered wing.

The 1052 automated weather observation for San Bernardino International airport (SBD) San Bernardino, California, located about 9 miles east of the accident site, included calm winds, visibility 10 miles, clear skies, temperature 26 degrees C, dew point minus 4 degrees C, and an altimeter setting of 29.78 inches of mercury.

According to FAA information, the airplane was manufactured in 2001, and was equipped with a Rotax 503 series engine. The engine was manufactured in 2000, and was mounted in a pusher configuration below the high-mounted, fabric-covered wing.

The FAA inspector responded to the accident site on the day of the accident, and obtained initial factual documentation. The aircraft owner and other persons recovered the wreckage to the pilot's hangar at Brackett Airport (POC), La Verne, California. Examination of the recovered airframe and engine was conducted by the FAA and NTSB on May 15, 2013, in the pilot's hangar.

While no evidence of any pre-impact catastrophic mechanical deficiencies or failures that would have precluded continued engine operation and flight was discovered, the overall condition of the airframe and engine were indicative of a lack of recent maintenance or upkeep, and many irregularities and deficiencies were observed. The details of that examination are contained in a separate document in the public docket for this accident.

The NTSB/FAA examination results were provided to Rotech, a Rotax-designated technical resource for accident investigation. A Rotech technician reviewed the information. Overall, the technician was concerned about the general condition of the engine, and the apparent lack of recent maintenance. The technician also provided detailed feedback regarding several deficient observed conditions, as presented in the paragraphs below. The technician concluded that the power loss could have been the result of any one of the observed deficiencies, or some combination thereof.

The principal problem with the fuel lines being secured with metal screw-type hose clamps is that they have a flat spot on their inner diameter, formed by the screw housing. This flat spot does not allow full 360-degree clamping. This can cause an air leak in the fuel system, considerably reducing the capacity of the fuel pump. The section of fuel line between the fuel tank and fuel pump is under considerable negative pressure when the engine is running hard, and the smallest flaw in any joint will cause air to be sucked into the system. Air leaks are much more detrimental when the fuel tank is mounted below the fuel pump and carburetor, as it was on the accident aircraft.

The fuel filter is supposed to be mounted between the fuel pump and carburetor, as shown in the Rotax installation manual. The accident aircraft had the fuel filter mounted between the fuel tank and fuel pump. Mounting the fuel filter on the suction side of the fuel system could reduce the capacity of the fuel pump and it is another potential area for an air leak. Contamination that was found within the fuel filter could block fuel flow, reducing the capacity of the fuel pump.

The rubber carburetor socket that joins the carburetor to the intake manifold was cracked. This could cause air to be sucked into the engine resulting in a lean fuel to air ratio. This rubber socket has a life span of 5 years. A daily condition check is to be done on the carburetor sockets for cracking, as stated in the Rotax operators manual.

Cracks were found on the exhaust system. The Rotax two stroke exhaust system is tuned and required to be in perfect condition. Two stroke engines depend on a timed echo sent back from the exhaust canister to close an exhaust valve long enough to maintain the incoming fuel in the chamber. Without this effect the top end performance and fuel consumption would be very poor. The Rotax operators manual pre-flight section explicitly states to inspect the exhaust system for cracks.

Spark plugs "A" and "B" from cylinder 1 are in very poor condition, with heavy carbon build up. This is an indication of either poor oil quality, poor fuel quality, incorrect carburetor positioning, and/or failure to replace the spark plugs at the required 25-hour intervals, as stated in the Rotax maintenance schedule. Spark plugs in this condition would not operate properly resulting, in a loss of engine performance and hard starting.

Rotax records show that this engine was sold late in the year 2000. According to the Rotax maintenance schedule, this engine should have been overhauled twice, per the Rotax-required overhaul interval of 5 years. No records indicated that this engine had ever received an overhaul.