DEN02TA069
DEN02TA069

On July 7, 2002, approximately 1830 mountain daylight time, a WSK PZL Mielec M-18A, N5198Y, owned by Utility Aviation, Inc., of Fort Collins, Colorado, and operated as a public use aircraft by the Bureau of Land Management (BLM), Boise, Idaho, was destroyed when it impacted terrain while maneuvering shortly after takeoff from Fillmore Airport, Fillmore, Utah. The commercial pilot, the sole occupant aboard, received minor injuries. Day visual meteorological conditions prevailed, and a BLM-approved flight plan had been filed for the fire suppression flight. The flight originated at Fillmore, Utah, approximately 1827.

The airplane operator submitted NTSB Form 6120.1/2, Pilot/Operator Aircraft Accident Report that had been sent to him by the pilot. Pages 5 and 6 were missing. Attempts to contact the pilot, who had since resigned, were not successful.

The following is based on an investigation conducted by the U.S. Department of Interior's Office of Aircraft Services (OAS). On the morning of the accident, the pilot and BLM's single-engine air tanker (SEAT) manager reported for duty at BLM's hangar. The loader/driver called in sick and the SEAT manager told him to remain in his hotel room until he felt better. [This constituted a breach of contract. The SEAT manager should have notified her supervisor that the airplane was unavailable, or sought modification of the contract from DOI's contracting officer]. Approximately 1530, with the permission of the SEAT manager, the loader/driver drove to St. George to pick up a prescription. No fire suppression missions were flown until a request for assistance was received late that afternoon. While the SEAT manager took the request, the pilot donned his flight gear and went to the airplane to begin loading the retardant.

The pilot used the retardant storage tank (provided by Fire-Trol) and the water "pumpkin" (provided by the federal government) to load the retardant mixture into the airplane hopper. The pilot told DOI investigators that he set the retardant valve to "two notches" and the water valve to "full open." Before the hopper was full, the SEAT manager arrived and the pilot told her that the mixture looked "thick" and to set the retardant valve to "one notch" to thin the mixture. The SEAT manager complied but the hopper was almost full and she subsequently closed the valve. The pilot told OAS investigators that the hopper was filled with 400 gallons of retardant.

According to OAS investigators, the pilot did not consult the M-18A's Pilot Operating Handbook to determine airplane performance. The charts, however, do not address airplane performance operating at 93 degrees F. (34 degrees C.). The pilot failed to disengage the emergency release (jettison) handle-locking lever prior to takeoff as required by the Pilot Operating Handbook. The pilot also chose not to arm the hydraulic power for the retardant gate prior to takeoff for fear of an inadvertent load release on the airport. Although the Pilot Operating Handbook does not require this, OAS investigators said it is "common practice in the fire retardant business" to arm the switch and release the retardant in an emergency situation. OAS said this is "an example of a negative habit transfer because all of [the pilot's] previous experience in this airplane had been carrying pesticides. The pilot, they said, was new to fire suppression, having been certified on May 31, 2002. He had made four water drops, two for certification purposes and two in fire suppression. The accident flight was the second time the pilot had flown with retardant, the first being on July 1. On that occasion, the pilot mixed the retardant, and it was said the slurry "looked thick."

Operating as "Tanker 450," the airplane departed Fillmore Airport's runway 22, en route to a nearby forest fire. The pilot used 10 degrees of flaps for takeoff. He said the takeoff roll was "a little longer" than usual, which he attributed to the high temperature. Climbing to 300 to 400 feet agl (above ground level), he turned left (east) onto the crosswind leg and noticed a lower propeller rpm (1 to 2 inches) and manifold pressure than he anticipated. When he turned left (north) again onto the pilot downwind leg, he noted the airplane was in a 50 to 100 foot per minute rate of descent. He turned left (west) to avoid the town of Fillmore. The airplane was 50 to 100 feet agl as he crossed Interstate Highway 15. The pilot realized he needed to jettison the retardant and made several unsuccessful attempts to use the emergency jettison handle. While his attention was diverted to the jettison handle, the right wingtip scraped the ground, digging a 63-foot long furrow. The engine struck the ground and separated from the airframe. The airplane then pivoted about the right wing 180 degrees, slid backwards, and came to a halt 143 feet from the initial point of impact. The landing gear separated and both wings and the fuselage were buckled. The left main gear was 9 feet in front of the nose, and the right main gear was next to the right elevator. There was no fire. When examined at the accident site, the slurry mixture was of a "very thick consistency."

Weather at the time of takeoff was recorded on the Fillmore 1750 METAR (Aviation Routine Weather Report) observation, to wit: wind, 220 degrees at 13 knots; visibility, 50 statute miles; ceiling, 25,000 feet overcast; temperature, 34 degrees C. (93 degrees F.); dew point, 12 degrees C. (54 degrees F.).

OAS certificated the pilot to serve as a SEAT pilot on May 31, 2002, 38 days before the accident. His certificate application indicated 2,900 total hours, 500 hours mountain flying, and 350 hours in make/model. In order to be certificated, the pilot made two demonstration water drops. He made two other water drops when he was assigned to Fillmore, Utah. The accident flight was the second time the pilot had flown with retardant, the first time being on July 1. At that time witnesses said the slurry mix "looked thick." The pilot said his employer gave him "a few hours" of dual instruction in the Fillmore area in a different type airplane. His employer also "briefly" discussed the procedures for transferring, mixing, and loading retardant. OAS pointed out that the training of vendor personnel (pilot and driver/loader) was the responsibility of the vendor. SEAT managers are responsible for contract compliance and are trained by the U.S. Government.

Chemonics Industries manufactured the slurry, called Fire-Trol. It consisted of ammonium phosphate, a clay thickener, corrosion inhibitor, and colorant. A sample of the slurry, removed from the sealed pump hose, was submitted to Wildland Fire Chemical Systems for testing. The sample was determined to be LCA-R (concentrated retardant unmixed with water). No water was found in the sample. The sample weighed 12.2 pounds per gallon, slightly heavier than pure concentrate (12.1 pounds per gallon). OAS investigators said this might have been due to the failure of the operators to recycle the concentrate as recommended by the manufacturer. Their investigation revealed that the water and retardant valves were working properly and should have delivered a proper water-retardant mix if they had been set correctly. They concluded the water valve was in the full closed position during the mixing process.

According to Chemonics Industries' instructions, a refractometer should be used to check the slurry mixture at the beginning of, and several times during, the loading process. The refractometer measures the salinity of the mixture and displays this information to the operator. The acceptable range of LCA-R is 13 to 15 (less than 13 is too diluted, and more than 15 is too concentrated). The pilot and SEAT manager told investigators they had never used the refractometer in the days they worked together.

Properly mixed, the slurry concentrate should weigh 9.13 pounds per gallon. The slurry sample taken at the accident site weighed 12.2 pounds per gallon. The airplane's hopper held 400 gallons. A properly mixed load should weigh 3,652 pounds. It was computed that the hopper's payload weighed 4,880 pounds at the time of the accident, a difference of 1,228 pounds.

In a letter dated July 16, 2002, Wildland Fire Chemical Systems advised the National Interagency Fire Center that the sample was "within the acceptable range for pure Fire-Trol LCA-R (concentrated retardant unmixed with water). The sample received by our lab was LCA-R. The refractometer and density are both indicators of salt content. The viscosity and density are within the parameters that we expect to see in an unmixed sample of LCA. The refractometer results are within acceptable parameters for the mixed product. These results indicate that no water was added to this sample before it was received at our lab. Fire-Trol LCA-R has a specific weight of 9.12 lb/gal and 12.10 lb/gal, respectively, for mixed retardant and liquid concentrate. We would expect to see a density of 1.090-1.105 h/mL for a mixed product (water added). In an 800-gallon tank at 1.105 g/mL, the weight should be 7296 lbs. A density of 1.466 g/mL equates to 12.2 lb/gal of LCA-R, which translates to 9760 lbs."

On July 12, 2002, the U.S. Department of Interior's Office of Aircraft Services issued Safety Alert 02-03 and OAS Operation Procedures (OPM) Memorandum No. 02-46, entitled, "Accepted procedures for the mixing and loading of retardant into SEAT aircraft." Citing "several recent aircraft incidents that involved the overloading of SEAT aircraft with liquid concentrate (LC) retardant as a result of mixing and loading procedures," including "loading LC directly into aircraft from bulk storage tanks while utilizing various types of hardware devices that were intended to blend retardant," the Alert said that "serious overloading can occur when pure LC is loaded into an aircraft without being mixed with the appropriate ratio of water."

On July 16, 2002, the U.S. Department of Agriculture's Forest Service issued Safety Alert 2002-17. It stated (in part): "In an effort to eliminate the possibility of overloading an aircraft with an incorrect mix of retardant, the following procedures apply immediately: "Both powdered and liquid bulk materials will be blended in a mixing container prior to being introduced into the aircraft. In order to maintain quality control and safe flight operations, no bulk material will be loaded into an aircraft prior to being mixed to the proper ratio and checked by refractometer or other accepted method. The practice of loading an aircraft with bulk material and then adding water is not an acceptable method of mixing retardant." This Safety Alert was reiterated by a memorandum, dated July 25, 2002, from Wildland Fire Chemical Systems to all air tanker base managers and personnel.



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