N. LITTLE ROCK, AR, USA
N173VE
VELOCITY 173 RG ELITE
The experimental homebuilt airplane was destroyed when it impacted trees following a loss of engine power during the takeoff/initial climb. Several witnesses reported that the engine sputtered then it lost power. Post-accident metallurgical examination revealed radial and circumferential cracks on the valve seat head of the #3 exhaust valve. The combustion chamber face of the valve contained sites of surface tearing where there was a lack of fusion of the coating to the base metal. Voids at the interface between the coating and the base material contained aluminum oxide, a material used during surface preparation operation.
HISTORY OF FLIGHT: On March 26, 1998, at 1610 central standard time, a Velocity 173 RG Elite homebuilt experimental airplane, N173VE, was destroyed when it impacted trees and terrain following a loss of engine power during the takeoff/initial climb from the North Little Rock Municipal Airport, North Little Rock, Arkansas. The airplane was owned and operated by private individuals under Title 14 CFR Part 91. The private pilot and the passenger received fatal injuries. Visual meteorological conditions prevailed for the local personal flight and a flight plan was not filed. The flight was originating at the time of the accident. Witnesses were interviewed by the NTSB investigator-in-charge (IIC). A pilot, located at the police base of operation building parallel to runway 17, observed the airplane during the takeoff and stated "I could hear a vibration like a prop[eller]. As the aircraft lifted off, there was certainly a problem with control, it would porpoise, yaw, and roll approximately 20 degrees on each axis. The engine was increasing and decreasing RPM rapidly. All these difficulties could be seen [and] heard during the flight until just before impact then the engine stopped." A witness, standing on the ramp area parallel to the runway, observed the airplane proceeding down runway 17 "abort the takeoff and taxi back to the end of the runway." The aircraft then successfully took off and when it was about 500 feet [agl] the right wing dipped and the plane dipped a little to the right, turned right on course, and headed over Camp Robinson [National Guard Facility adjacent to the North Little Rock Municipal Airport]. I then heard the engine "sputter and attempt to restart." Subsequently, this witness observed the airplane maneuvering "very low, just above the trees" as if it was returning to the airport. A mechanic at the airport observed the airplane abort a takeoff and taxi back to runway 17. During the taxi, he noted that the engine was not running smoothly and another witness reported the sounds of the engine as "ragged [and] sputttering." Another witness/pilot reported that the pilot obtained a weather briefing prior to the flight. Several days prior to the accident, this witness recalled that the "pilot and the fixed base operator had a conversation concerning the failure of the fuel pump. According to the witness, the pilot stated the engine ran at 1,400 RPM with the fuel boost pump. The pilot was discussing the possibility of switching from an in line fuel pump installation to a parallel installation." A pilot at the airport observed the aircraft's departure and after a few seconds heard the motor "start to surge high to low RPM (maybe 5 times)" and then stop. A witness at Camp Robinson stated that the engine "died and restart[ed] 3 times before I saw it come up below the tree line. It arced high over the street and nose dive[d] into [the] trees." Another witness at Camp Robinson heard the engine of the airplane "sputter and quit, start back up, stop and start back up again, then quit." This witness said he heard the airplane crash and explode. Another witness reported that 3 days (March 23, 1998) prior to the accident, the airplane departed runway 05 and when the airplane was 100 feet to 200 feet AGL, the engine sputtered and lost power. The airplane entered a glide and landed on runway 05 without further incident. Numerous witnesses reported that the winds were from the south at 15 to 20 knots. They, observing the post crash fire and smoke, called 911. Local and Camp Robinson authorities responded to the scene. The Magellan GPS location of the accident site was 1 nautical mile 235 degrees from the airport at 34 degrees 49.42 minutes North, 92 degrees 16.39 minutes West. PERSONNEL INFORMATION: A review of the FAA records revealed that the pilot obtained his private pilot certificate on January 8, 1990. On his third class medical certificate application form, signed on February 11, 1997, the pilot reported 1,200 hours of accumulated flight time. The medical certificate limitation required the pilot to wear lenses for distant vision and possess glasses for near vision. Medical records indicted that the pilot was diagnosed with diabetes that was controlled by diet. The pilot received a factory checkout (1.3 hours) in the Velocity aircraft. The pilot logbook was destroyed in the post impact fire. AIRCRAFT INFORMATION: According to information obtained from the builder, FAA, the manufacturer, and the Velocity Owner's Flight Manual, the Velocity 173RG (s/n 301) N173VE, was registered to the current owner on February 28, 1996. The 4 place experimental homebuilt composite airplane was issued the FAA airworthiness certificate on May 6, 1997. The aircraft design incorporated tricycle landing gear and swept wing with NASA-developed winglet system. The winglet consists of an upper and lower cambered surface at each wing tip. Maximum gross weight is 2,250 pounds. The engine was a pusher configuration. The fuel system consisted of two 30 gallon wing tanks with a mechanical engine driven fuel pump that transfers fuel to the carburetor. An auxiliary electric fuel pump provides backup for the engine-driven pump and fuel pressure redundancy during low altitude operation. According to the manufacturer, Franklin engine s/n 2611100047 was delivered to the United States from "PZL-RZESZOW"-Spolka Akcyjna (SA), who holds the Polish GICA Type Certificate No. CB-129 and the FAA Type Certificate No. E9EA, in July 1995. There with no accessories installed at the time of delivery. During telephone interviews, conducted by the IIC, with the builder, and internet correspondence from the pilot and/or the builder with other Velocity builders, the following information was reported for N173VE. The Franklin (6A-350-C1R, S/N 2611100047 CB-129, 205 horsepower, 2,800 rpm, 10.5:1 compression ratio) engine with 10 hours of running time was purchased from Aero Center, in the State of Oregon. Subsequently, the Franklin engine was derated (190 horsepower, 8.5:1 compression ratio) to operate on 93 octane automotive fuel. Derating was done by the builder and involved replacing the 10.5 pistons with new 8.5 pistons (pistons manufactured for engine 4A-235-B31,-B4) from "PZL-RZESZOW"-Spolka Akcyjna (SA). The camshaft was re-profiled in the U.S. to the 8.5 Franklin engine camshaft specifications. Ten hours of ground test running was accomplished prior to the first flight. The propeller was changed in January 1998 to an increased pitch propeller designed for the Franklin engine by IVO Propellers. The airplane was reported to cruise at 190 mph in the derated configuration. According to the builder, at 107 hours of total time, while on cross country flight at 8,500 feet msl and an rpm of 2,550, the engine driven fuel pump failed. The disabled mechanical pump restricted the flow provided by the electric boost pump limited the engine operation to 1,400 to 1,500 rpm's. The airplane was landed without further incident. The builder examined the engine driven pump (AC4886) and found that the flapper valve housing had disintegrated and partially blocked the fuel passageway. Following this loss of engine power, the builder modified the fuel system by installing a second boost pump (NAPA 7-9psi) parallel to the existing serial fuel system. One-way flow valves were installed in each parallel outlet line. One fuel line had a mechanical pump to pump the fuel to the carburetor and an electrical boost pump. The parallel line had a second electrical boost pump. During taxiing in 98 degree temperature conditions, the pilot had experienced a loss of engine power due to vapor lock. Subsequently, the builder installed a return line with an electrically operated solenoid valve whereby the fuel in the line could be returned to the left fuel and the lines filled with cooler fuel from the left fuel tank prior to takeoff. According to the builder, the total time on the airframe was estimated at 116 hours and the airplane had flown 9 hours since the modification of the fuel system. Franklin Engine Description, Operation and Service Manual (Doc. No. 26.0.197) for the Franklin 6A-350-C1R includes the following data. The engine specifications are found in the Polish GCIA Type Certificate No. CB-129 and the FAA Type Certificate No. E9EA (copy enclosed). Poland and the U.S. have a bilateral agreement for the acceptance of the aircraft engine into the U.S. Issuance and continued acceptance of the engine requires that the engine meet Title 14 CFR Part 21.1 (SFAR 26.1) which states in part that the type certificate may be issued under FAR 21.29 when the FAA determines that the design standards and practices, the quality control standards, and the certification procedures utilized by Poland are the equivalent of those required in the United States. Title 14 CFR Part 33 prescribes airworthiness standards for the issuance of type certificates and according to the Type Certificate Data Sheet No. E9EA, the 6A-350-C1R engine model complied with FAR Part 33. FAA Advisory Circular (AC 21-23) provides information on the FAA airworthiness certification or acceptance of civil aeronautical products imported to the United States. To be considered for installation on United States registered aircraft, each engine to be exported to the United Sates shall be accompanied by a certificate of airworthiness or certifying statement: This engine conforms to its United States type design (Type Certificate Number E9EA) and is in a condition for safe operation. PZL Franklin Engine Service Letter No. 95-1 states in part: WARNING: THE INSTALLATION OF ACCESSORIES OTHER THAN SPECIFIED IN THE "ENGINE DESCRIPTION, OPERATION, AND SERVICE MANUAL" MAY CAUSE PREMATURE FAILURE OF THE ENGINE, AND INVALIDATES THE TYPE CERTIFICATE." The FAA inspector, assigned for the engine examination, stated that "it is unknown if the builder changed the magneto timing or changed the camshaft in order to compensate for the different (shorter) fuel burn duration for autogas in lieu of avgas." He further stated that "once the certificate of airworthiness has been issued by Poland for a specific engine, any changes to that engine per its type design will invalidate the status of the engine certification unless approved by the cognisant aircraft certification office (ACO)." The "PZL-RZESZOW"-Spolka Akcyjna (SA) representative classifies de-rating (pistons and re-ground camshaft) as a major alteration, major design change, or major change in type design, and that "once the engine was derated with 8.5 cylinders, the engine did not meet the type certificate." The representative further stated that the "8.5 piston lowers the available power by approximately 10 percent." The FAA Type Certificate states the minimum grade aviation gasoline as 100/130, the engine compression ratio at 10.5:1 for the 6A-350-C1R engine. The Engine Description, Operation, and Service Manual (26.0.197) states: USE OF AVIATION GASOLINE WITH THE OCTANE NUMBER LESS THAN OCTANE NUMBER PROVIDED BY REQUIREMENTS IS INADMISSIBLE AS THIS MAY RESULT IN DETONATION DURING COMBUSTION AND IN THE DAMAGE TO THE ENGINE. According to the "PZL-RZESZOW"-Spolka Akcyjna (SA) representative, the 6 cylinder engine, 6A-350-C1R, 10.5:1 compression ratio, and the 4 cylinder engines, 4A-235-B31, -B4, 8.5:1 compression ratio are "not allowed to be used with automotive fuel." Technical data for the 6 cylinder and the 4 cylinder Franklin engines specifies the minimum grade aviation gasoline as 100/130. METEOROLOGICAL INFORMATION: The Little Rock, Arkansas, weather observation (METAR) issued at 1550 reported wind from 200 degrees at 14 knots with gusts to 22 knots. The visibility was 10 statute miles with scattered clouds at 5,000 feet and broken clouds at 25,000 feet. The temperature was 81 degrees Fahrenheit with a dewpoint of 55 degrees Fahrenheit. The altimeter was 30.04 inches of Mercury. AERODROME: North Little Rock Municipal Airport is a non-towered airport served by runways 05/23 and 17/35. The asphalt runway 17 is 3,009 feet long and 75 feet wide. Airport location is 34 degrees 50.00 North latitude; 092 degrees 15.15 minutes West longitude. The airport elevation is 544 feet msl. WRECKAGE AND IMPACT INFORMATION: Aircraft wreckage (North 34 degrees 49.42 minutes; West 092 degrees 16.32 minutes) was distributed along a measured magnetic heading of 180 degrees with the final resting site (elevation 542 feet) in and along a creek bed approximately 177 feet from the North Dakota Road located on Camp Robinson North Little Rock, Arkansas. The cockpit area came to rest on a magnetic heading of 260 degrees with the engine and portions of the main wing spar oriented in a southerly direction. Portions of the aircraft including the aircraft identification (N173VE) on the winglet area of the aircraft were found in a tree located 68 feet from the road. Other fiberglass portions of the aircraft were at the base of this tree and in and around the bases of a cluster of trees 109 to 152 feet from the road. The aircraft was destroyed by a post impact fire. The engine was found at the base of a tree on the southern bank of the creek. The fiberglass was burned from the inner propeller rods. The propeller rod found stuck in the ground was bent upward. MEDICAL AND PATHOLOGICAL INFORMATION: The autopsy was performed by the Arkansas State Crime Laboratory, at Little Rock, Arkansas. Toxicological testing was performed by the FAA Civil Aeromedical Institute (CAMI) at Oklahoma City, Oklahoma. The toxicological findings were negative. TEST AND RESEARCH: The airplane components that were not destroyed by the post impact fire were examined on July 29, 1998 at Lancaster, Texas, under the surveillance of the NTSB IIC. The Precision Carburetor MA-5, (p/n 10-5043, s/n 75048309) screen contained charred debris. The carburetor metal float and the venturi were intact. A teardown of the engine revealed that the #3 cylinder exhaust valve head was separated from the valve stem. The surface of the piston and the base of the cylinder were deformed. The exhaust valve keeper and the rocker spring were loose. The #3 cylinder piston, rocker arms, valve springs, valve spring seat, valve retainers, and valve stem cap, and #1 cylinder exhaust valve were forwarded to the NTSB Metallurgical Laboratory for examination. The #1 cylinder push rod sustained impact damage. The rocker arm for the #1 cylinder was removed from contact with the push rod. Subsequently, hand compression was noted at cylinders #1, #2, #4, #5, and #6. The crankcase was S/N 2611180027 and the crankshaft S/N was 26110069. Camshaft showed P/N 81390 with the camshaft lobes ranging from 39 to 40 mm when measured with a digital micrometer. The spark plug gap ranged from .022 to .024 with the top spark plugs for cylinders #1 and #2 exceeding .040. The magneto, SLICK Model 6399, serial number 97050399, had the adapter per PZL Service Bulletin 50-96 installed. The oil pump bearing surfaces were smooth. Camshaft bearings exhibited wear. The top metal cover of the engine driven fuel pump and a portion of the fuel pump spring were the only fuel pump components found at the site. The fire and impact damaged fuel pump adapter was found attached to the engine. The fuel pump adapter drive was forwarded to the NTSB Metallurgical Laboratory for further examination. The NTSB metallurgists found radial and circumferential cracks on the valve seat head of the #3 exhaust valve. Examination of the combustion chamber face of the valve revealed sites of surface tearing. The coating fracture associated with the tearing appeared to have no fusion of the coating with the base material. Further examination revealed a void between the base material and the coating in the area of the fracture. A void at a depth of 80 microns was associated with a radial crack extending to the surface. Circumferential voids between the coating and the base material contained particles (identified as aluminum oxide) of no uniform shape. Metallurgical examination of the #1 exhaust valve revealed two pits on the seat of the valve.
Inadequate fusion between the valve stem and head due to inadequate quality control during construction of the exhaust valve for the number three cylinder. A contributing factor was the lack of suitable terrain for the forced landing
Source: NTSB Aviation Accident Database
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