HISTORY OF FLIGHT On August 9, 1993, at approximately 1200 Alaska daylight time, a tundra tire equipped Piper PA-18-135 Supercub, N1200A, owned and operated by Kelly Bay, d.b.a. Wrangell Mountain Aviation, Inc., crashed on landing at a remote strip near the Barnard Glacier. This glacier is located in the Wrangell Saint Elias National Preserve, approximately 40 miles ESE of McCarthy, Alaska. The airplane had departed McCarthy at 1120 in visual meteorological conditions under 14 CFR Part 135 for the purpose of carrying sheep hunters. No flight plan was filed. The commercial pilot and his passenger(s) were not injured. The airplane was substantially damaged. The accident location was approximately N61-07, W141-40, at an undulating alluvial field of the Barnard Glacier, south of peak 8230 (feet) shown on the Anchorage Sectional Chart, (43rd Edition, 12/15/88). This location is approximately 50 miles (40 minutes flight time) one-way from McCarthy, Alaska. The flight time considers the cruising speed of a PA-18 Supercub to be approximately 80 knots with an 8% speed degradation due to tundra tires in a no-wind condition. Initial information received by the NTSB via the U.S. Park Service (OAS pilot) at 1900 on August 9, 1993, indicated that the pilot had radioed the passing USPS airplane that the he and his passengers were not injured. On August 11, 1993, the operator told the FAA Principal Maintenance Inspector that he had overturned his supercub on landing due to the roughness of the strip, saying that he, "got on the brakes too hard." He also said that the strip was about 500 feet in length at the 3300 foot level and that he was transporting goat hunters. The pilot further said that it was his second trip to the strip on that day and that on the previous trip he had transported most of the gear of two hunters for a 12 day trip and a 200 pound passenger. On the accident flight, the pilot told the FAA that he had only light gear and a 180 pound passenger on board. The pilot told the NTSB that the damage to the airplane was limited to "minor fabric damage to the wing, a bent prop and a bent rudder." The US Park Service ranger-pilot reported that in communications with the pilot on the day of the accident that the airplane had suffered broken spar and that it had a "wing off." The Park Service said that the strip was "very short and would not allow it's pilots to land there." Information provided by the OAS pilot who first communicated with the accident airplane on the day of the accident indicated that two passengers were on board at the time of the accident. Information provided by the pilot-operator to investigators indicated that there was only one passenger on board at the time. Attempts by the NTSB to interview the passengers, named by the operator, have been unsuccessful. AIRCRAFT INFORMATION The airplane was fitted with a third seat under an approval not applicable to this airplane. The operator provided the NTSB with a copy of a Supplemental Type Certificate (STC) (SA554AL issued 5/7/79 to D. M. Hendrick of Buffalo, MO and R. E. Sullivan of Anchorage) authorizing the addition of a third seat to be installed aft of the passenger seat. Research of records (Type Certificate Data Sheets) has indicated that the accident aircraft, serial number 1200, was manufactured as an original "PA-18" (sometimes referred to as a PA-18-90, 105, 115 or 135, according to the horse power rating of the engine). The STC provided as a basis for the third seat on the accident airplane applies to basic PA-18-150 airplanes which have been manufactured originally as a PA-18-150 under a type certificate of 1954 and later. The accident airplane was built by Piper on or about September 21, 1951. Also provided was an August 1992 weighing record indicating the weight of the airplane (with full fuel) to be 1433 pounds. The maximum gross weight of the airplane is 1750 pounds. The aircraft was weighed with full fuel (36 gallons) however, the oil quantity was 7.0 quarts. The oil capacity of the engine is actually 8.0 quarts. The STC document supplied is a design change to add a third seat in the baggage compartment, however, as stated in the "limitations and conditions," applies only to Piper PA-18-150 models only. The accident airplane was not a PA-18-150 model. The weighing record of the accident airplane (attached) indicated a useful load of 546 pounds added to an empty weight of 1204 pounds. Should the airplane, as configured by the STC be loaded to carry a pilot and 2 passengers of a standard weight (170 pounds each), for a total of 510 pounds, the airplane could carry only fuel of only 36 gallons. ADDITIONAL INFORMATION The rear seat was not placarded in accordance with Part 23. Notwithstanding the STC's inapplicability to this serial numbered PA-18, and therefore the design change deviation from the type certificate, the installation did not indicate a requirement for a third seat placard for those operations where a standard (170 pound) passenger could not occupy that seat. A placard would be required under 14 CFR Part 23.1557 if a passenger seat could not accommodate a passenger of at least 170 pounds, and additionally, that the aircraft be required to have at least one half hour of fuel (at rated maximum continuous power) and full oil (8.0 quarts) to pass certification with a passenger weighing 170 in each of its installed seats. (14 CFR 23.25). In the case of the accident airplane the aft seat must be placarded with a limitation of 147.5 pounds, (if the STC was legal in the first place.) The airplane was equipped with "tundra tires" for which there was no known approval for this airplane. The airplane was reportedly equipped for bush operations under its operating certificate (14 CFR Part 135) with 30 inch tundra tires. No STC was known to have been granted for this airplane for use of that tire. The FAA Anchorage Aircraft Certification Office stated that while various STC's exist for a wide range of balloon "tundra tires," no certification flight tests, nor no approved changes in limitations or performance exists on airplanes so equipped. (See attached ACE-115N memo dated 4/27/93.) The airplane was equipped with an unapproved powerplant. The airplane was modified with a Lycoming O-320/B2B "conical- mount" 160 horsepower engine. This installation can be approved under applicable STC's which allow design changes for this engine to modify an original PA-18-150 model, however is not permitted for application to a PA-18 (90 or 105 or 135 series). In addition, it was reported that the engine was further fitted with a constant-speed propeller. Such a propeller is an unauthorized deviation to the STC upgrade to the 160 HP engines, (had the STC actually applied to the accident airplane.) The FAA Principal Operations and Maintenance Inspectors of this 14 Part 135 operator had conducted ramp inspections on this aircraft previously. Furthermore, the accident airplane was placed on the operator's 14 CFR Part 135 certificate after review by the Anchorage FSDO.