Cottage Grove, OR, USA
N9988L
Grumman American AA-1B
The instructor (pilot-in-command) and student (aircraft owner) checked the Grumman AA-1B's fuel supply believing they had about 1/4 tank (left) and 3/4 tank (right) prior to departing on the instructional flight. Airwork at high altitude was completed, and then the aircraft was taken into the pattern for practice touch and go landings. During the initial climb following the first touch and go, and not more than 200 feet above ground, the engine abruptly stopped and the propeller was reported to stop rotating. The instructor took control of the aircraft, maneuvering away from trees and towards a landing site, while the student selected the right fuel tank and turned on the fuel boost pump, but did not engage the starter. The aircraft impacted trees during the forced landing. Fuel and aircraft log records indicated that under the best conditions (assumption of full tanks, i.e. 22 gallons useable fuel total on 09/29/00) the aircraft had a total 35.6 gallons of usable fuel expended over a duration of 7.4 Hobbs hours from 09/29/00, to the time of the accident (approximately 4.81gallons/hour average burn). The fuel selector was reported on the left fuel tank at the time of the power loss and found on the right fuel tank at the accident site. The fuel system was checked following the accident and was found to be capable of delivering fuel to the carburetor. The engine was examined and no anomalies were found. The carburetor was flow checked and disassembled and no discrepancies were found. Serious carburetor icing conditions were found to exist at the time of the accident.
HISTORY OF FLIGHT On January 10, 2001, approximately 1400 Pacific standard time, a Grumman American Aviation AA-1B, N9988L, registered to Little Green House Antiques and Collectibles, Inc., and being flown by a student pilot and a commercial flight instructor, was destroyed during an in-flight collision with terrain following a loss of power during the initial climb following a touch-and-go at the Cottage Grove airport, Cottage Grove, Oregon. Both pilots sustained serious injuries. There was no post-crash fire at the site. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was operated under 14 CFR 91 and was instructional in nature, originated from Cottage Grove approximately one hour earlier. The flight instructor was telephonically interviewed on 01/14/01, and provided the following information. The instructor and student departed Cottage Grove and did some high work (slow flight and power off stalls) and then entered the pattern at Creswell airport (8 nautical miles north of Cottage Grove airport) for practice landings. After an approach and go-around at Creswell due to a helicopter on the runway, they returned to Cottage Grove to continue the practice landings. The first approach and landing to the 3,200-foot long runway 33 at Cottage Grove was executed followed by the application of full power, carburetor heat "OFF," and flaps "UP." As the aircraft reached approximately 200 feet above ground (AGL) the engine abruptly stopped. There was no coughing, sputtering, or vibration and the aircraft was wings level at the time. The instructor took control of the aircraft and the student began to trouble shoot the power loss by switching fuel tanks and activating the electric boost pump without success. The instructor established a glide and turned the aircraft to the right about 15 degrees attempting to clear the river and high trees at the north end of the runway. The student pilot (aircraft owner) reported that prior to takeoff he "...checked the fuel levels prior to flight that day by visually observing the sight tubes for each tank..." and that the instructor pilot "...checked the fuel levels as well...." He reported that both he and the instructor believed they had two hours of fuel available with one-quarter tank left and three-quarter tank right. The student pilot also reported that he believed the propeller stopped turning after the power loss and that he had no time to activate the starter following the loss of engine power. PERSONNEL INFORMATION Flight Instructor: The flight instructor reported a total of 2,298 hours of flight experience of which 903 hours were as an instructor. Additionally, he reported 0.9 total hours of flight experience in the Grumman AA-1B type aircraft. Student Pilot: The student's personal logbook was opened on 01/17/97 and contained 35 instructional flights logged up through 01/04/98. These flights were conducted in Cessna 172 type aircraft with the exception of 2 flights in the Cessna 182 and 4 flights in the Piper PA-28. The log showed a total of 5 flights conducted in 1999, 2 in the Cessna 172, 1 in the Cessna 150 and 2 in the accident aircraft. The remaining 3 flights in the logbook were logged in 2000 in February, March, and April consecutively. The first 2 flights were in the accident aircraft and the last was in a Cessna 150. The student showed a total of 51 hours of logged flight experience, all recorded as "dual." His flight experience between the April 2000 flight and the accident flight were not known. AIRCRAFT INFORMATION The AA-1B's fuel system consists of a tubular tank (wing spar) partitioned into two cells, one in each wing outboard of the fuselage. Each cell holds 12 gallons of fuel of which 11 gallons is usable. The fuel is fed to the engine through a fuel selector which allows the pilot to individually select any of the three positions as marked "OFF-LEFT-RIGHT." Fuel cannot be drawn from both tanks simultaneously. Fuel from the tanks then passes through an auxiliary electric boost pump, on to the engine driven pump and finally to the carburetor. Fuel quantity is assessed by way of vertical sight gauges on the left and right cockpit walls outboard and adjacent to the left and right seat occupants' upper legs (refer to photographs 1 and 2). Each tank is fueled through a cap on its respective wing and the fuel can be visually checked at this location. According to records from the Cottage Grove airport, N9988L was fueled on the following dates: 29 SEP 00 13.77 gal 27 NOV 00 6.20 gal 28 DEC 00 7.40 gal* *This was the last known fueling of the aircraft and occurred on the approximate date (give or take 2 days). The fuel supplier was interviewed and reported recalling that the student pilot bought the gas, but that this was not a "top off," rather the insertion of enough gas to take the weight of the aircraft up to but not exceeding maximum gross takeoff weight with two occupants. The fuel supplier also reported that he believed these three fueling events were the only times the aircraft had been fueled between 09/29/00 and the accident date. A flight documentation (trip) record was found indicating that the aircraft on 09/29/00, was the same date as the 13.77 gallon fuel addition. The start time was recorded as 3756.1 (Hobbs) and the ending time was recorded as 3757.3 (Hobbs), or a total Hobbs time of 1.2 hours. The aircraft owner (student pilot) reported that this 13.77 gallon fuel addition preceded the 1.2 hour flight. According to the airframe log for N9988L, the aircraft underwent an annual inspection on 11/17/00, at a tach (total airframe) time of 4185.42 hours (the Hobbs reading on this date was reported to be 3757.5 hours). The tach time at the accident was observed to be 4190.33 hours (the Hobbs reading was observed to be 3763.5 hours). Based on the "best case" assumption that the 09/29/00, addition of fuel took the aircraft to full fuel tanks, the following fuel/tach/Hobbs time reconstruction was compiled: DATE TACH (hr) HOBBS (hr) FUEL ADD TOTAL FUEL 29 SEP 00 UNK 3756.1 13.77 gal 22.0 gal available 29 SEP 00 UNK 3757.3 -------- UNK 17 NOV 00 4185.42 3757.5 -------- UNK 27 NOV 00 UNK UNK 06.20 gal UNK 28 DEC 00 UNK UNK 07.40 gal UNK 10 JAN 01 4190.33 3763.5 -------- UNK -------------------------------------------------------------------------------------------------------- TOTALS 0007.4 hrs 35.6 gal available* *The distribution of this fuel between left and right tanks at any given time other than the hypothetically full fuel tanks on 09/29/00, was unknown. Fuel consumption for the Lycoming O-235-C2C equipped aircraft for operations at 2,500 feet above sea level ranged from 5.3 to 5.9 gallons/hour (dependent upon the type of propeller installed). Refer to CHART I, which provides fuel consumption rates for the Lycoming O-235-C2C equipped aircraft as a function of altitude and RPM. The instructor reported in the previously referenced telephonic interview that the aircraft had about 2 hours worth of fuel aboard when the flight initially departed; approximately 7 gallons in one tank and 6.5 gallons in the opposite. He also reported that he visually checked the fuel gauges before the flight and he believed the student physically checked the fuel quantity in the tanks. He also reported that the fuel selector was on "LEFT" at the time of the power loss. The aircraft was equipped with dual Slick magnetos of which one was equipped with an impulse couple. Should the propeller stop rotating it is necessary to engage the starter in order to initiate ignition. This condition was not discussed in the AA-1B Owner's Manual or in the emergency procedures section for engine failure. METEOROLOGICAL INFORMATION The aviation surface weather observation for Eugene (21 nautical miles north-northwest of Cottage Grove) on the afternoon of the accident (1356 hours local) reported in part: temperature 7 degrees C. and dew point 5 degrees C. A carburetor-icing chart is included (refer to ATTACHMENT I). WRECKAGE AND IMPACT INFORMATION The aircraft crashed just beyond a wooded area and slightly north of the Cottage Grove airport. Both wings were separated from the aircraft at the wing root area and both wings had sustained major tree impact damage along their leading edges. Each wing's fuel tank had been ruptured. The aircraft came to rest upright with one blade of its propeller in the 12 o'clock position and the opposing blade embedded vertically into the soil (refer to photographs 3 and 4). The prop spinner displayed upwards crushing at the point where the lower propeller blade entered the hub assembly. The FAA inspector who examined the aircraft at the site on the evening of the accident reported that the fuel selector was in the "RIGHT" position. Additionally, he observed fuel in the electric boost pump housing. TESTS AND RESEARCH The aircraft's engine and fuel system was examined at the facilities of HLM Air Service, Independence, Oregon, on the morning of January 25, 2001. Both magnetos were examined and tested in place with no malfunctions noted in either the magneto wiring or the magnetos themselves. The aircraft's air intake system was examined and was found to be free of any blockage. An alternate fuel system was set up through the right wing fuel tank line where it was torn from its tank. The electrical system was energized and the electric fuel boost pump was found to operate and provide a supply of fuel to and through the engine driven fuel pump and on to the carburetor. The engine driven fuel pump was removed and manually actuated. Suction and pressure were noted at the intake/outflow ports and the pump. The propeller was rotated and the actuating pin driven by the camshaft, which drives the engine driven fuel pump, was determined to function properly. Rotation of the propeller verified continuity of the crankshaft with acceptable compression/suction being measured on all 4 cylinders. The rocker arm cover boxes were removed and proper rocker arm movement and sequencing was observed during crankshaft rotation. Continuity between the mixture, throttle and carburetor heat controls to their appropriate attach points on the carburetor and heat box were noted. The throttle valve was observed fully open and the mixture lever was in the full rich position. The carburetor was removed and taken to the facilities of Precision Airmotive, Arlington, Washington. The Marvel-Schebler Carburetor, Model MA-3A, was flow-checked and then disassembled and examined. No anomalies were noted and the carburetor functioned within acceptable limits. ADDITIONAL INFORMATION An FAA Inspector examined the wreckage at the accident site on the evening of the accident, and then released the aircraft to Taylor's Towing & Auto Wrecking, Inc., for removal. Written wreckage release was accomplished on February 7, 2001, with the exception of the aircraft's carburetor. Written release of the carburetor was accomplished on February 15, 2001 (refer to attached NTSB Forms 6120.15).
The flight instructor's failure to ensure (supervision) the student had an adequate supply of fuel available, and the student's failure to refuel the aircraft sufficently resulting in a fuel starvation/exhaustion condition and total power loss. Contributing factors were the trees and unsuitable terrain at the forced landing site.
Source: NTSB Aviation Accident Database
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