NTSB Identification: CHI06FA206A
HISTORY OF FLIGHT
On July 30, 2006, at 1207 central daylight time, a Grumman TBM-3, Avenger, N420GP, operated by the Tri-State Warbird Museum, sustained minor damage when it taxied into the empennage and fuselage of an amateur-built Vans RV-6, C-FNQP. Both aircraft were taxiing for takeoff on Papa taxiway, which parallels runway 18 at the Wittman Regional Airport (OSH), Oshkosh, Wisconsin. The passenger seated in the right seat of the RV-6 received fatal injuries. The RV-6 pilot and the pilot and passenger of the Avenger were not injured. Visual meteorological conditions prevailed at the time of the accident. The pilots and passengers of both aircraft had attended the EAA AirVenture 2006 air show and were departing OSH. The Avenger's destination was Clermont County Airport, Batavia, Ohio, and no flight plan was filed. The RV-6's destination was Gore Bay, Ontario, Canada, and the pilot had filed a visual flight rules (VFR) flight plan.
The RV-6 pilot reported that the RV-6 was parked on row 301 of the homebuilt aircraft parking area that was located just south of the P-1 taxiway. The RV-6 pilot reported that the airplane was pushed onto the P-1 taxiway before he started his engine. He taxied forward on the P-1 taxiway and was directed by the flag person to taxi south on Papa taxiway. He reported that he was taxiing behind a green and white, high wing airplane that had TUNDRA painted on the top of the wing. He reported that a gray airplane was in front of the Tundra aircraft. The RV-6 pilot reported that he "didn't know the TBM was behind" his airplane. The RV-6 pilot reported that he was not sure if he was taxiing forward or if he was stopped when the Avenger struck the RV-6 from behind.
The Avenger pilot reported that the Avenger was parked in the Warbird parking area located at the north end of the air show display area. The Avenger pilot started the engine and let the engine warm up for about five minutes before he began to taxi. He taxied the airplane south toward the P-1 taxiway. He observed the flag person clear him to begin taxiing on Papa taxiway. The Avenger pilot reported that the airplane in front of the Avenger was a green and white, high wing airplane with TUNDRA written on top of the wing. He reported that he taxied at a very slow speed with the propeller speed set about 800 RPM. He reported that the Avenger had no mechanical defects and that the brakes were good. He reported that the relatively narrow width of the taxiway prevented a large angular change from the taxiway centerline. He reported he made "shallow S-turns within the confines of the taxiway width." The Avenger pilot reported that he observed the Tundra pilot taxi off the right side of the taxiway for some unknown reason. The Avenger pilot reported that he spotted the airplane that was in front of the Tundra airplane, and he stated that he had "100 yards of free pavement" in front of the Avenger. The Avenger pilot reported that when he heard the impact and saw debris flying, he shut down the engine. He reported that he never saw the airplane that he hit while he was taxiing.
The pilot of a Lancair airplane reported that he followed the Avenger while taxiing on Papa taxiway and he observed the Avenger taxi into the RV-6. The Lancair pilot reported that his airplane was parked in the homebuilt aircraft parking area near the Lancair airplane exhibit area located just south of the P-1 taxiway. He reported that about six aircraft marshallers helped push his Lancair into a position near the Papa taxiway so that he could start his engine. One of the aircraft marshallers motioned to him that he was cleared to taxi onto Papa taxiway. Instead, the Lancair pilot waited because the Avenger was approaching and he did not want to be in front of the Avenger while taxiing. After the Avenger passed, the Lancair pilot taxied onto Papa taxiway. He followed the Avenger at a distance so that he could remain clear of the Avenger's propeller blast. The Lancair pilot reported that it was "stop and go" traffic on the taxiway because of the number of airplanes taxiing for takeoff. The Lancair pilot reported that the Avenger pilot did not make any "S-turns" while taxiing, but instead, taxied straight ahead. The Lancair pilot reported that "all of a sudden" he observed black smoke and debris "flying everywhere" as the Avenger hit the RV-6. The Lancair pilot reported that there were no wing-walkers or aircraft marshallers next to the Avenger while it was taxiing on Papa taxiway.
A witness reported that he observed the Avenger taxi from the Warbird parking area to the P-1 taxiway and on Papa taxiway. The witness reported that he was walking in the same direction as the Avenger was taxiing, so the witness was focused on watching the Avenger. The witness reported that the Avenger was moving "very slowly and deliberately." He reported that the Avenger did not make any S-turns while it taxied on Papa taxiway. He reported that there were no wing-walkers for the Avenger while it taxied on Papa taxiway.
Another witness reported that she saw the Avenger do one S-turn while it was on Papa taxiway. She reported that she was observing airplanes taxi toward "Tower Road taxiway." She reported that there were about 8 - 10 airplanes, including a blue B-25 warbird, in front of the Avenger. She reported she observed the Avenger angled toward the side of the taxiway when it was "further down" the taxiway, but she did not know if the Avenger was doing S-turns at the time of the accident.
The Experimental Aircraft Association's (EAA) video production team was doing a video shoot of the Papa taxiway as the dissimilar aircraft were taxiing south toward Tower Road taxiway where they turned toward the runway for a "mid-field departure." The video operator was located about 40 feet south of the Tower Road taxiway.
The video indicated that numerous aircraft were in line on Papa taxiway at the Tower Road taxiway. The video showed that the aircraft in front of the Avenger, before the impact occurred, included the accident RV-6, a green and white high wing airplane (Tundra), a gray RV-6, a red and white Cessna 150, a Glasair, a RV-6, a L-39 jet, and a blue B-25 warbird. The video showed the Tundra in front of the accident RV-6 and just behind the gray RV-6. The video showed the Tundra taxiing off the right side of Papa taxiway. The video showed that after the Tundra taxied off the taxiway, the Avenger was in a slight turn to the right and then turned back to the centerline within about 17 seconds after the Tundra taxied off the taxiway. The Avenger impacted the RV-6 about 1 minute 21 seconds after the Tundra taxied off Papa taxiway. The Avenger was the fifth airplane from Tower Road taxiway at the time of the accident. The video indicated that the Avenger was taxiing straight ahead for about 9 - 10 seconds prior to the time of impact and was not making an S-turn. The video indicated that the Avenger pilot was looking forward over the nose of the Avenger as it was taxiing forward prior to impact with the RV-6.
The length of Papa taxiway from the P-1 taxiway to the Tower Road taxiway is 1,500 feet. The accident occurred about 320 feet north of the Tower Road taxiway. The width of the taxiway is 35 feet.
The Avenger pilot held a commercial pilot certificate with single-engine land, glider, and airplane instrument ratings. He had about 2,500 hours of total flight time with 16 hours in the TBM Avenger. The pilot reported that he had flight experience in numerous "warbird" aircraft that included about 1,400 hours in the T-6, 60 hours in the P-51, and 70 hours in Stearman airplanes. He held a second-class medical certificate.
The RV-6 pilot held a private pilot's certificate with a single-engine land rating. He had about 543 hours of total flight time with 24 hours in a RV-6. He held a third-class medical certificate.
The single-engine Grumman TBM-3, serial number 53420, was a World War II torpedo bomber that seated three and had a maximum gross weight of 17,600 pounds. The Wright model R-2600-20 engine produced 1,900 horsepower. Its wingspan was 54 feet 2 inches, its length was 39 feet 5 11/32 inches, and its height was 12 feet. The width of the Avenger's main landing gear measured from the middle of the tires was about 10 feet 10 inches. When the airplane was sitting on its landing gear, the nose of the airplane was angled upward about 11 1/4 degrees.
The single-engine amateur-built Vans RV-6 seated two and its maximum gross weight was 1,200 pounds. The Lycoming O-320-B2A engine produced 160 horsepower. Its wingspan was 23 feet, its length was 20 feet 5 1/2 inches, and its height was about 5 feet 5 inches.
At 1153, the surface weather observation at OSH was: winds 160 degrees at 8 knots, clouds few at 5,000 feet, visibility 10 statute miles, temperature 23 degrees Celsius (C), dew point 20 degrees C, altimeter 29.84 inches of mercury.
The Federal Aviation Administration (FAA) issued a 29-page Notice To Airman (NOTAM) that detailed the special flight procedures for the EAA AirVenture 2006 air show that were effective from July 22 - July 31, 2006. Among other things, the NOTAM provided information for preflight planning, route planning, arrival and departure routes, and Oshkosh airport notes.
The EAA website, www.airventure.org, provided pilots with information about air traffic control procedures and aircraft movement on the ground. The website stated, "During AirVenture, whether departing VFR or IFR, all surfaces other than the active runways are considered to be Non-Movement Areas. This doesn't mean that you cannot taxi on them - it simply means that Air Traffic is only controlling surface traffic that is on active runways. During AirVenture, all ground movement is controlled by EAA Volunteers."
An EAA official reported the following concerning aircraft taxiing on Papa taxiway:
"Pilots are directed onto the Papa taxiway at P1 and Papa by EAA flag persons. A/C taxi one behind the other to the taxiway in front of the control tower, where they are directed onto the runway for takeoff by ATC personnel. They (pilots) are not controlled by ATC ground control or by EAA flag persons while moving along on taxiway Papa."
During AirVenture, Papa taxiway was used for southbound aircraft movement unless approved otherwise. EAA volunteer flag persons were stationed at the intersection of P1 taxiway and Papa taxiway, and at the intersection of Tower Road taxiway (P2) and Papa taxiway for southbound taxi traffic on Papa. The Ditch taxiway was used for northbound aircraft movement unless approved otherwise. EAA volunteer flag persons were stationed at the intersection of P1 taxiway and the Ditch taxiway, and at the intersection of Tower Road taxiway and the Ditch taxiway for northbound taxi traffic on the Ditch taxiway.
The flag person at that intersection of P1 taxiway and Papa taxiway flagged aircraft onto Papa taxiway. The aircraft then taxied south on Papa taxiway until reaching the intersection of Papa taxiway and Tower Road taxiway. There, the next flag person would flag the aircraft to turn left onto the Tower Road taxiway where the aircraft contacted the control tower for takeoff clearance
WRECKAGE AND IMPACT INFORMATION
The Avenger collided with the RV-6 on Papa taxiway about 1,180 feet south of the intersection of the P1 taxiway and Papa taxiway. The rudder and empennage of the RV-6 exhibited propeller strikes. The right aileron and right flap of the RV-6 were broken away from their wing attach points. The right side of the fuselage and cabin exhibited impact marks consistent with a propeller strike. The tail of the RV-6 was found displaced about 4 feet left of the taxiway centerline. The debris field was located on the east side of Papa taxiway from the debris from the RV-6.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy of the RV-6 passenger was performed at the Fond du Lac County Coroner's Office, Fond du Lac, Wisconsin, on July 31, 2006.
TESTS AND RESEARCH
The distance between the propeller strike marks on the empennage of the RV-6 were about 3.5 inches. At a propeller speed of 800 RPM, the relative motion between the Avenger and RV-6 at impact was calculated to be approximately 6.9 knots.
On August 8, 2006, a visibility study of the Avenger and RV-6 was conducted by the National Transportation Safety Board's (NTSB) investigator-in-charge (IIC) and the accident reconstruction specialist from the Winnebago County Sheriff's Department.
During the visibility study, the Avenger was positioned on the centerline of taxiway Papa facing south. The pilot used in the visibility study was wearing the Avenger's parachute and restraint harness, and was seated in the Avenger at approximately the same height as the accident pilot. The pilot leaned forward and looked straight ahead, looking over the nose of the Avenger to determine the accident pilot's approximate field of vision while taxiing on Papa taxiway. The Avenger's engine cowl flaps were positioned in the full open position.
The RV-6's height of 5 feet 5 inches was used as the basis for the distance measurements in the visibility study. Using the measurements obtained from the laser measuring equipment, an "Area of No Visibility" was defined, and then plotted using a computer aided design (CAD) program.
An exemplary RV-6 was positioned on the centerline of Papa taxiway. The RV-6 was placed at various distances from the Avenger to determine when it was in the field of vision of the pilot of the Avenger, and conversely, when it was in the Area of No Visibility.
The visibility study indicated that the Area of No Visibility extended from the Avenger's pilot position out to approximately 170 feet. No part of the RV-6 was visible to the Avenger pilot until it was positioned approximately 170 feet from the pilot in the Avenger. At about 242 feet, the RV-6 was partially in view of the Avenger pilot. At 332 feet, the RV-6's canopy was in full view of the Avenger pilot. At 463 feet, the entire RV-6 was in view of the Avenger pilot.
A 2-dimensional CAD drawing was created to simulate the available visibility from the Avenger using the laser measurements that were obtained on August 8, 2006. The CAD drawings demonstrated the following results if "S-Turns" of 5 and 10 degrees were performed on the taxiway:
1. With a turn of 5 degrees, the wingtip of the RV-6 was visible at approximately 110 feet.
2. With a turn of 10 degrees, the wing of the RV-6 was visible all the way to the area of impact, and the airplane was never wholly within the Area of No Visibility.
On February 21, 2007, the NTSB IIC conducted a second visibility study of an Avenger and a RV-6 at the Addison Airport, Addison, Texas. The second visibility study confirmed that portions of the RV-6 could be seen from the cockpit of the Avenger all the way to the area of impact when the Avenger was angled 10 degrees from the taxiway centerline. With the Avenger's longitudinal axis aligned with the taxiway centerline, no portion of the RV-6 was visible until it was 140 feet in front of the Avenger, except for a small portion of the RV-6's wingtip when the RV-6 was positioned directly in front of the Avenger.
The Avenger pilot reported that he had flown to the EAA Oshkosh air show for about 15 - 18 years in other warbird aircraft. He reported that he normally landed and departed using runway 9/27, and that using runway 18/36 for departure was an unusual occurrence. He reported that he had used Papa taxiway when he was flying as a participant in the air shows, but then there were no other airplanes using the taxiway at the same time. He reported that he had never taxied on Papa taxiway for departure from runway 18/36 the previous years, and that it was the first time he had taxied on Papa taxiway with other airplanes using the taxiway.
The Avenger pilot reported that there were no mechanical problems with the airplane at the time of the accident.
The RV-6 pilot reported that he had flown to the EAA Oshkosh air show five times. He reported, "The co-pilot had visited Oshkosh more than 25 times. Most of them by air. He had more than 100 hours in an RV-6 and more than 1200 hours total."
The Airplane Flying Handbook states the following about taxiing a tailwheel-equipped airplane:
"Since a tailwheel-type airplane rests on the tailwheel as well as the main landing wheels, it assumes a nose-high attitude when on the ground. In most cases this places the engine cowling high enough to restrict the pilot's vision of the area directly ahead of the airplane. Consequently, objects directly ahead of the airplane are difficult, if not impossible, to see. To observe and avoid colliding with any objects or hazardous surface conditions, the pilot should alternately turn the nose from one side to the other-that is zigzag, or make a series of short S-turns while taxiing forward. This should be done slowly, smoothly, positively, and cautiously."
The FAA, EAA, and the EAA Warbirds of America were parties to the investigation.