Flight Patterns
The basic goal of the flight patterns is to stay as close to the thunderstorm of interest for as long as possible. In most cases, it will be desirable to overfly the storm as it initiates, grows, matures, and decays. Occasionally the storm becomes too intense or vertically developed to directly overfly. In that case the ALTUS may be flown around the storm while staying as close to the storm as possible. Turns will be made as quickly and smoothly as possible to maximize the data collection quality. The primary flight pattern will be the petal as shown in the figure to the right.
This pattern will be best for isolated storms that can be overflown. The approach to the storm will be on a vector directly over the center of the storm. The initial flight path will continue until the aircraft has passed over the storm. As soon as possible after the aircraft clears the storm top, the aircraft executes a sharp (but smooth) turn until it is again on a vector over the storm center. Note that as the storm moves, the pattern will stay constant in the storm frame-of-reference, that is, we want to stay with the storm, not with some set location fixed in relation to the ground. This pattern will continue until the storm has decayed or the aircraft is vectored to another target.
If the petal flight pattern is not appropriate for the storm situation, the next desirable flight pattern is called the racetrack. This pattern will be most appropriate for lines of thunderstorms or storms with significant anvils. The approach to the storm is along a vector in line with the storm center or storms centerline. Once the aircraft has cleared the storm (or reached the end of the storm line or anvil), the aircraft executes a 90°/270?turn set to return it to the same storm relative heading as on the previous vector, only in the opposite direction. This pattern continues until the storm has decayed or the aircraft is vectored to another target. If the storm is too tall or severe for direct overflights, the polygon pattern, will be the next best choice. The approach pattern will be to make the closest approach to the storm as conditions allow. Once this closest approach is made, the aircraft is to make a series of glancing approaches to the storm. The occasional, small turns are to be made as quickly and as smoothly as possible so that the maximum time is spent on straight and level flight. This pattern continues until the storm has decayed or the aircraft is vectored to another target.
The final flight track is called the line. It is for cases where there is a line of storms that are too severe or tall to overfly. The aircraft is to approach the storm as if it were going to overfly or penetrate the first storm in the line. At the distance of closest approach, the aircraft is to turn and fly straight and level, parallel with the front face of the storm system. After the UAV passes the storm system, it will execute a 90°/270?turn set away from the storm to bring the aircraft back along the initial storm relative flight line only now in the opposite direction. The actual distance to the storm edge will be determined by the storm type and severity. This pattern will continue until the storm system decays, moves out of range, or the aircraft is vectored to another target.
