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ASN Wikibase Occurrence # 134162
Last updated: 18 November 2021
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Type:Silhouette image of generic M18 model; specific model in this crash may look slightly different
WSK PZL Mielec M-18A Dromader
Owner/operator:Bureau of Land Management
Registration: N5198Y
MSN: 1Z023-07
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Location:Fillmore, UT -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Departure airport:Fillmore, UT (U19)
Destination airport:Fillmore, UT (U19)
Investigating agency: NTSB
The airplane took off and was en route to a nearby forest fire. The pilot said the takeoff roll was "a little longer" than usual, which he attributed to the high temperature. He noticed a lower propeller rpm (1 to 2 inches) and manifold pressure, and the airplane was in a 50 to 100 foot per minute rate of descent. He realized he needed to jettison the retardant, and made several unsuccessful attempts to use the emergency jettison handle. While his attention was diverted to jettisoning the load, the airplane collided with terrain. The pilot failed to disengage the emergency release (jettison) handle-locking lever prior to takeoff as required by the Pilot Operating Handbook. He also chose not to arm the hydraulic power for the retardant gate prior to takeoff. When examined at the accident site, the slurry mixture was of a "very thick consistency." The pilot said he mixed and loaded the slurry, called Fire-Trol, into the airplane. The slurry consisted of ammonium phosphate, a clay thickener, corrosion inhibitor, and colorant. A sample of the slurry, removed from the sealed pump hose, was tested and found to be LCA-R (concentrated retardant unmixed with water). The sample weighed 12.2 pounds per gallon, slightly heavier than pure concentrate (12.1 pounds per gallon). No water was found in the sample. When properly mixed, the slurry concentrate should weigh 9.13 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.
Probable Cause: the pilot's failure to follow proper procedures/directives, and the airplane's inability to climb while maneuvering after takeoff. Factors contributing to the accident were improperly mixed aerial application materials (fire retardant slurry), the high aircraft weight and balance, and the pilot's diverted attention.




Revision history:

21-Dec-2016 19:26 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
09-Dec-2017 16:57 ASN Update Bot Updated [Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative]

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