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On January 21, 1997, at 1350 central standard time (cst), a Mooney M20J, N1160G, was destroyed when the aircraft collided with snow covered terrain near Cottage Grove, Minnesota, during an ILS runway 32 approach, to the St. Paul Downtown Holman Field Airport. The private pilot and passenger were fatally injured in the accident. The pilot had planned to fly to Cambridge, Minnesota, but requested a diversion into Holman Field, due to weather. The 14 CFR Part 91 flight was operating on an IFR flight plan, and instrument meteorological conditions prevailed at the time of the accident.
The weather at St. Paul Downtown Holman Field Airport at 1353 cst was reported as wind 150 degrees at 13 knots, visibility 1.5 miles with light rain. The ceiling was reported as 500 feet overcast, the temperature was 3, the dewpoint was 0. The altimeter was 29.52.
AIDS TO NAVIGATION
The airplane received radar vectors for an ILS to runway 32. Between the time of 1316 cst and 2043 cst five other aircraft executed the ILS to runway 32, at the St. Paul Downtown Holman Field Airport. None of these aircraft reported any problems with any of the navigational equipment for the approach. At 1316 cst the pilot executing the ILS 32 approach reported that he broke out at 1,250 feet mean sea level. The decision height for a full ILS 32 approach is 954 feet.
WRECKAGE AND IMPACT INFORMATION
The airplane wreckage path followed a magnetic heading of approximately 330 degrees. The distance from the right wing tip which was the first piece found in the wreckage path, to the location of the last piece in the wreckage path was measured by a survey crew as 556 feet.
The right wing was u shaped, the left wing showed no significant span wise bending. The pitot tube on the left wing was found with no signs of ice or debris noted either on the tube, or in the drain hole for the tube. When the left wing was flipped over following the accident, fuel was seen running out of the wing tank which stained the snow a bluish tint. All of the airplane's control surfaces were found at the accident site. No signs of any control surface abnormality were found by the investigator in charge (IIC). The flaps appeared to be in the retracted position at the time of impact.
The fuselage was separated just in front of the empennage, in the cabin area, and in front of the cabin near the firewall. The throttle, propeller, and mixture controls were all found in their maximum forward positions. The gear handle in the cockpit for the landing gear was found in the up position. The airspeed indicator's needle was found indicating 165 knots. The valve for the vacuum systems alternate air was found in the open position. The standby vacuum knob, and the alternate static source knob were both found out approximately one half inch. The aircraft's artificial horizon was not located until March of 1997. The static ports on the fuselage appeared to be open, with no signs of ice or debris covering them.
The airplane's propeller was separated from the crankshaft of the engine. Both blades of the propeller showed signs of chordwise scratches, leading edge damage, and were twisted. Both propeller blades had broken loose in the hub of the propeller, and had rotated approximately 180 degrees from their normal position.
Before the engine was moved from the accident site the air box was removed from the fuel control and no indications of icing were found. The fuel manifold on top of the crankcase was opened and was wet with fuel. The engine alternate air door was found in place and it appeared to be in the closed position at the time of the accident.
MEDICAL AND PATHOLOGICAL INFORMATION
Both occupants of the airplane were separated from the main portion of the fuselage, and ended up near the end of the wreckage path.
An autopsy was performed on the pilot, and the passenger by the Office of the Medical Examiner, at 300 E. University Ave., St. Paul, Minnesota. Toxicological testing done on the pilot by the Federal Aviation Administration in Oklahoma City, Oklahoma, was negative for all tests conducted except Ibuprofen.
TESTS AND RESEARCH
The airplane's engine was moved from the accident location to a heated garage on the evening of January 22, 1997, for further examination. The top spark plugs were removed and inspected with no abnormalities noted. The ignition wires were cut, and all of the ignition leads produced spark when the engine was rotated by hand. The crankshaft was rotated using the accessory gear that the vacuum pump runs from on the accessory case of the engine. All cylinders had compression when the engine was rotated.
The mechanical fuel pump casting was damaged. When the mechanical fuel pump was opened all of the gaskets and seals appeared to be normal. The electric fuel pump would pump water when it was tested following the accident with a battery charger.
The vacuum pump's shaft was intact and the vacuum pump would produce vacuum when rotated by hand. When the vacuum pump was opened, all of the carbon vanes were intact.
The airplane's artificial horizon was disassembled by the IIC on March 14, 1997. The artificial horizon showed signs similar to impact damage, but no abnormalities were found when the artificial horizon was disassembled. The internal brass gyro did not show any signs of rubbing on its aluminum case. Some corrosion was present on the inside of the aluminum gyro case when disassembled.
The pilot of N1160G was receiving radar vectors from the Minneapolis Approach Control Facility. At 1903:01, N1160G was cleared to descend from 8,000 feet to 6,000 feet. At time 1908:31, the pilot of N1160G reported that "ya I shot through six thousand can I continue on down or do you need me up here?" At which time the controller clears N1160G to descend to 4,000 feet. At time 1947:58 the controller requested the pilot of N1160G to verify his altitude. At time 1948:21 the controller request the pilot to climb to two thousand five hundred feet. At 1948:27 the pilot reported "we're going up sir." At time 1948:37 the controller instructed N1160G to turn left to a heading of 120 and asked if everything was ok. At time 1949:24 the controller reestablished contact with the pilot of N1160G and again asked the pilot if everything was ok. At time 1949:27 the pilot responded with "negative". The controller responded back at 1949:29 asking the pilot if he wanted emergency vectors to Saint Paul. The pilot's last transmission with the controller was at 1949:32. The complete transcript of the last 45 minutes of pilot conversations with air traffic control (ATC) is included with this package as a supplement.
On April 23, 1997, the IIC interviewed the pilot of a Beech Duchess who was also executing the ILS 32 approach to Holman Field, at the time of the accident. The pilot of the Beech Duchess remembered the top of the overcast in the approach area was approximately 5,500 at the time of the accident. The pilot also reported that no icing conditions were encountered during the approach.
The radar data for the accident aircraft was obtained by the IIC. The raw radar data was plotted from the National Tracking Assistance Program (NTAP) radar data. This data shows that at 1947.5 minutes N1160G was at 2,400 feet above mean sea level (msl), and then descended to 1,700 feet msl at 1948.2 minutes. During this same time period the airplane ground track appears to change to the 180 degree heading issued by ATC. At 1949.25 minutes the radar data shows that N1160G is at 1,200 feet msl, and increases to 2,000 feet msl at 1949.58 minutes. The last radar data for N1160G is at 1949.75 minutes, and indicates an altitude of 2,100 feet msl. The graphical representation of this data is included as a supplement to this report.
Mooney M20J rate of climb performance data was reviewed by the IIC. The maximum rate of climb for a M20J, at 2,300 pounds, at 2,000 feet pressure altitude, and a temperature of 0 degrees celsius is shown at approximately 1,275 feet per minute.
A review of the pilot's logbook indicated that since January 2, 1995, until the day of the accident, the pilot had flown 4.1 hours of actual instrument time, and 3.5 hours of simulated instrument time. Over this same time period the pilots logbook indicated that the pilot had flown 14 instrument approaches. Of the 14 approaches 11 were NDB approaches at the airport where the aircraft was based, and 3 were ILS approaches at the Madison Airport where the airplane departed from. The pilot's logbook also showed that the pilot had flown N1160G since May 21, 1996. Previous to the M20J, the pilot's logbook indicated numerous flights in a Mooney M20F.
The pilot had recorded 1.5 hours of actual instrument time on July 10, 1996 and 3.5 hours of simulated instrument time between August and September 1996 in the accident airplane. The pilot's logbook showed that he had flown 3 ILS's at the Madison Airport on August 13, 1996, and 2 NDB approaches at the airport where the airplane was based on September 15, 1996. No instrument approaches under actual IFR conditions were recorded by the pilot in his logbook in the accident airplane.
Parties to the investigation were the FAA, and Lycoming.
The airplane wreckage was released to a representative of United States Aviation Underwriters.