NTSB Factual Report

HISTORY OF FLIGHT

On February 21, 2001, at 0705 central standard time, a Cessna 172H, N733SS, operated by AIRGO, Inc., was destroyed when it impacted terrain 1.2 miles from the Centralia Municipal Airport (ENL), Centralia, Illinois, on a magnetic bearing of 003 degrees from the airport. The Certificated Flight Instructor (CFI) and student pilot were fatally injured. The 14 CFR Part 91 flight departed from ENL approximately 0620 on a local instructional flight. No flight plan was filed.

A witness reported seeing the airplane traveling toward him from west to east. The witness reported initially hearing the airplane's engine, and that the engine was at a low power setting. He reported the airplane was low, about 500 feet, and the airspeed was slow. He reported the airplane was in a steep angle of bank and in a turn to the right. He reported the airplane was in "…a kind of a climb in a bank." He reported that after 270 degrees of turn, the airplane flipped over on its back and became inverted. The nose of the airplane then went down. He reported the nose of the airplane started coming up and the airplane looked like it was going to recover when he lost sight of the airplane behind a tree line. He reported hearing the airplane's engine revving to full power. Then he heard the airplane impact the terrain approximately 1/4 mile away.

PERSONNEL INFORMATION

The 32 year old CFI was a commercial rated pilot with single and multi-engine airplane land and instrument pilot ratings. He held instructor ratings for single and multi-engine land airplanes and an airplane instrument instructor rating. He held a First Class Medical Certificate that was issued on July 1, 1999. The CFI was 5'7" tall and weighed approximately 149 pounds. He had a total of approximately 2,504 flight hours. He flew 112 hours in the last 90 days, which included 107 instructional flight hours.

The CFI had received his CFI rating on March 22, 1999, and had been flying as an instructor pilot for the operator. He had successfully completed a FAA chief flight instructor check ride for FAR Part 141 operations on December 8, 2000. The CFI was designated as the Chief Flight Instructor for the operator's FAR Part 141 flight school.

The CFI was a citizen of the United Kingdom. He did not have a visa waiver, a work permit card, or a "Green Card" issued by the United States Immigration and Naturalization Service (INS).

The 55 year old student pilot held a Third Class Medical Certificate that was issued on July 29, 1999. He had approximately 98 total flight hours. He flew 17.9 hours, which included 2.5 solo flight hours, between January 21, 2001, and the day of the accident. Prior to January 21, 2001, the student pilot's last documented flight was on August 18, 2000. He had logged a total of 18.0 solo flight hours. The student pilot was 6'4" tall and weighed approximately 310 pounds.

AIRCRAFT INFORMATION

The airplane was a single engine Cessna 172H, serial number 17268518, manufactured in 1977. The airplane seated four and had a maximum gross weight of 2,300 pounds. The engine was a 160 horsepower Lycoming O-320-H2AD engine. The last 100 hour inspection was conducted on December 14, 2000, and the last annual inspection was conducted on April 3, 2000. The airplane had flown 61 hours since the last inspection and had a total airframe time of 8,563 hours. The engine had 4,181 hours since a major overhaul on June 10, 1991. At the time of the overhaul, the engine had a total time of 1,371.1 hours. The engine cylinder compression readings recorded on December 14, 2000, during the last 100 hour inspection, were 1) 74/80, 2) 78/80, 3) 75/80 and 4) 75/80. The operator had purchased the airplane on October 15, 1994.

METEOROLOGICAL CONDITIONS

The 0655 observed weather at Mt. Vernon, Illinois, located 16 miles southeast of ENL, was: Winds 020 at 7 knots, 10 miles visibility, clear, temperature 27 degrees F, dew point 13 degrees F, altimeter 30.50.

WRECKAGE AND IMPACT INFORMATION

The wreckage site was located on the bank of Raccoon Lake, approximately 1.2 nautical miles from the threshold for Runway 18 at ENL and close to the runway centerline. The coordinates were 38 degrees 32.35 minutes N, and 089 degrees 04.42 minutes W. The wreckage path covered a distance of about 125 feet on a bearing of 130 degrees magnetic. The initial impact point was a tree root at the water's edge which had a piece of wing structure lodged in it. The main wreckage, located about 32 feet from the point of initial impact, came to rest against two hardwood trees about 10 feet above the lake's shoreline.

The empenage remained attached to the fuselage and both were found in a 50 - 60 degrees nose down attitude with the longitudinal axis aligned to the northeast. The right side of the cabin impacted the trees at or just aft of the front seats. The right cabin door was found against the left side of the fuselage. Neither of the front seat lap belts were intact. The webbing of both lap belts was torn and shredded. Both shoulder harnesses were attached to the airframe, but only the right shoulder harness was attached to a lap belt. The instrument panel was separated from the fuselage and was not intact. The engine was partially separated from its engine mounts and was found under the left wing, inverted, and pointing in a northerly heading.

The left wing remained attached to the fuselage and was located to the left of the fuselage. It exhibited aft compression of the leading edge and front spar along its span but remained intact. The wingtip had separated from the wing. Pieces of wing structure with electrical wiring in it were found crushed and embedded in a tree root at the initial point of impact.

The right wing impacted the hardwood trees. The wing separated at Wing Station (WS) 100.5. The inboard section of wing that remained attached to the fuselage exhibited crushing and buckling of its leading edge and spar. The section of wing from WS 100.5 to WS 208.0 exhibited crushing and buckling. A three-foot section of the right wing spar web was located on the ground to the left side of the fuselage.

All flight controls were found at the wreckage site. The flaps were retracted and the elevator trim was found 5 degrees up (nose down trim). Control cable continuity was established from the ailerons, elevator, and rudder to the respective cockpit controls. The aileron cables were found connected to the cockpit control yoke assembly. The aileron cables were found separated at approximately Fuselage Station (FS) 25 and the cables exhibited "broom straw" separations. The direct and crossover cables were connected at the left and right aileron bellcranks and exhibited continuity to FS 25 where the respective cables exhibited broom straw separations. The direct control cables had separated strands at the aileron direct cable pulleys in each wing. The National Transportation Safety Board (NTSB) retained the sections of cable with separated strands for further examination. The direct cable pulleys were found intact. There were no nicks, gouges, or scratches to the aluminum pulley bracket. Both pulleys rotated and they had no nicks, gouges, or scratches. Both pulleys had black grease residue on the side of the pulleys and in the pulley grooves. The cotter keys were intact. There were no signs of cable rub against any interior wing sections between the left and right wing aileron bellcranks and the wing roots.

The engine examination revealed the crankshaft rotated and there was valve train continuity and rear accessory gear rotation. Thumb compression and suction were observed on all cylinders. The carburetor was broken at the mounting flange. The single shaft, dual magneto was found separated from the engine. The cap assembly, ignition wiring, and left side of the distributor assembly sustained damage. The drive shaft could be rotated enough that the impulse coupling functioned. The drive shaft would not rotate a full 360 degrees. The spark plugs, according to the Champion Chart AV-27, indicated worn electrodes. The alternator exhibited rotational impact marks on the alternator housing behind the alternator propeller fins.

The propeller remained attached to the engine. One propeller blade was bent back and had leading edge polishing, chordwise scratching, and tip curling. The second blade was bent aft and had leading edge polishing.

MEDICAL AND PATHOLOGICAL INFORMATION

Autopsies were performed on the CFI and student pilot at St. Mary's Good Samaritan Medical Center, Centralia, Illinois.

Forensic Toxicology Fatal Accident Reports were prepared by the FAA Civil Aeromedical Institute. The report concerning the student pilot was negative. The report concerning the CFI indicated that 1.355 (ug/ml, ug/g) Acetaminophen was detected in the blood. Acetaminophen is an ingredient in Tylenol.

TESTS AND RESEARCH

The NTSB Materials Laboratory examined the two cut-out portions of the aileron cable from the left and right wings. The Materials Laboratory Factual Report stated the following information:

"Both of the portions of aileron cable were about 10 inches in length and were partially separated approximately in the middle of their length. The partial separations were reportedly at pulley locations. The cable contained 7 strands of wire. Six of the strands were laid around the center strand. Each strand appeared to have approximately 19 wires. At each partial separation location, two to three strands were completely separated and additional individual wires in other strands were separated.

Detailed visual examination of the cable portions with a bench binocular microscope revealed the presence of wear adjacent to all of the separated wires. The wear had completely penetrated through the separated wires, leaving sharp pointed separated ends. The exterior surface of the cable sections in the vicinity of the partial separations also contained wear. No evidence of fatigue cracking or corrosion damage was noted on the cable portions."

ADDITIONAL INFORMATION

The Cessna Service Manual for C-172's manufactured between 1977 - 1986 provided the following information concerning the lubrication of pulleys:

"Lubricate unsealed pulley bearings, rod ends, and Oilite bearings, pivot bearings, pivot and hinge points, and any other friction point obviously needing lubrication, with general purpose oil every 1000 hours of oftener if required."

Parties to the investigation included the Federal Aviation Administration, Cessna Aircraft Company, and Textron Lycoming.

The aircraft wreckage was released to Phoenix Aviation Managers, Inc.

NTSB Probable Cause

The student pilot allowed the airspeed to get too low and inadvertently stalled the airplane, and the CFI delayed in taking remedial action.