BIAF	Waypoint before IAF in the CP-IAF contingency plan path
CP	Contingency waypoint
CP-IAF	Contingency plan path section from CP to IAF
FAP	Final Approach Path
FAF	Final Approach Fix waypoint
IAF	Initial Approach Fix waypoint
JMPS	Joint Mission Planning System
LRL	Left-Right-Left extremal
LSL	Left-Straight-Left extremal
LSR	Left-Straight-Right extremal
PFP	Primary Flight Path
RAP	Rapid Refresh
RLR	Right-Left-Right extremal
RSL	Right-Straight-Left extremal
RSR	Right-Straight-Right extremal
SAELSS	Semi-Automated Emergency Landing Site Selection
TDPT	Touchdown waypoint
UAV	Unmanned aerial vehicle
Nomenclature
A	Wing aspect ratio,
CD0	Flags-up parasite drag coefficient
e	Airplane efficiency factor.
g (m/s2)	Acceleration of gravity, 9.8 m/s2
HA (ft)	UAV altitude before the i-th phase of a minimum-time extremal trajectory
HB (ft)	UAV altitude after the i-th phase of a minimum-time extremal trajectory
HE (ft)	Estimated altitude lost value during one cycle around the helix-shaped excessive altitude loss path before descending to in no wind condition
HIAF (ft)	UAV altitude at the end of CP-IAF path section of the contingency plan
HELS (ft)	Elevation of the emergency landing site
HFAP (ft)	Altitude-to-be-at for the UAV before initiating the final approach path
${\tilde{H}}_{FAP}$ (ft)	Approximate altitude-to-be-at for the UAV before the final approach path with no wind assumption
HTDPT (ft)	UAV altitude estimate over TDPT in the contingency plan
M	Altitude bin counter value used in estimating the altitude drop
S (ft2)	Wing reference area,
tA (s)	UAV takeoff time from point A
tB (s)	UAV estimated landing time at point B
tΔh (s)	UAV descent time within a single altitude bin height
thH (ft)	Maximum tolerable height value over TDPT for a contingency plan
th0 (ft)	Threshold used in the heuristic rule that corresponds to the case where the UAV does not have enough altitude to complete the final approach path after arriving at IAF from CP.
th1, th2 (ft)	Thresholds used in the heuristic rule that corresponds to the case in which HIAF is almost equal to HFAP and there is no need for excessive altitude loss path
th3 (ft)	Threshold used in the heuristic rule that corresponds to the case where the UAV has relatively small excessive altitude, not enough to complete one cycle of the helix-shaped excessive altitude loss path.
th4 (ft)	Threshold used in the heuristic rule that corresponds to using the helix-shaped excessive altitude loss path due to significant excessive altitude.
Ti (s)	Travel time for the i-th phase of a minimum-time extremal trajectory assigned to a segment in the CP-IAF path.
Td (s)	Accumulated altitude bin descent times used in altitude drop estimation
V	UAV true airspeed
Vs (knots)	UAV sink rate for straight level gliding.
Vs(HA) (knots)	UAV sink rate at HA
$V_{sw}\left(H_A\right)$ (knots)	Total UAV sink rate at HA
Vsφ (knots)	UAV sink rate when turning.
$w_{H_A}$ (knots)	Downward wind forecast component at HA
W (lbf)	UAV weight at the contingency point, CP
Δh (ft)	Altitude bin height used for estimating altitude drop
ΔH (ft)	UAV altitude drop after a travel time of Ti
ρ (slug/ft3)	Air density value at UAV’s altitude
φ (rad)	Bank angle of the turn
ω (rad/s)	Turn rate