Fuel Jettisoning Simulation (FJSIM) for Prediction of Groundfall

Fuel jettisoned from aircraft in flight may pose a health and environmental hazard at the surface. The fuel jettisoning simulation model, FJSIM, provides a key tool for evaluating the health and environmental impact of fuel jettisoning events from fixed and rotary wing aircraft. Military pilots are sometimes required to jettison fuel to land safely. The U.S. Air Force conversion from JP-4 jet fuel to the less-volatile JP-8 in the 1990s substantially increases the chances of significant JP-8 groundfall from jettisoned fuel. Realizing this, the Air Force embarked on the FJSIM research effort to accurately predict surface concentrations of JP-8 in order to protect people and resources on the ground. FJSIM combines a detailed, experimentally-verified fuel evaporation model, ambient meteorological conditions and individual aircraft characteristics to yield a demonstrator model for fuel jettisoning. This Windows-based model lets users estimate the location, total mass, volume, and areal extent of the groundfall from actual jettison events and planned operations, and can assist in reviewing and developing fuel jettison policies.

Figure 1: Fixed and rotary wing platforms modeled by FJSIM.

The principal components of the FJSIM model are:

  • Multi-component evaporation
  • Parameterized atmospheric meteorology
  • Modeled aircraft wake characteristics
  • Experimentally determined drop size distribution

The model features numerous input/output elements and displays. A main screen (Figure 2) contains nearly all U.S. Air Force aircraft, and other aircraft can be easily added. Plots of surface deposition are available and provide the approximate location, areal extent, and concentrations of material reaching the ground (Figure 3). Separate plots of drop size distribution and time aloft are also provided, as is surface evaporation (a result which answers "How long will the fuel remain on the surface").

Figure 2: FJSIM Main Screen w/ meteorology window. (A variety of metric and English units can be selected.)

Figure 3: Surface deposition plots can be shown as a planview isopleth (left) or colormap plot (right). Heavy black line indicates aircraft path during jettison. Blue arrow is north. Red arrow is wind direction.

The technical basis of FJSIM is summarized in

Quackenbush, Teske, and Polymeropoulos, "A Model for Assessing Fuel Jettisoning Effects," Atmospheric Environment, Vol. 28, No. 16, pp. 2751-2759, 1994.

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