Flying with and against the wind or flying perpendicular to the wind

There are various ways of flying in relation to the wind direction. The two extremes are:

Flying with and against the wind.

In the example above if the wind is at 360 degrees meaning it is blowing out of the north to the south, then the aircraft is flying into the wind from waypoint 8 to 9 to 10 to 11 to 12. If the plane normally flies at 35 knots and the wind is at 15 knots the ground speed is only 20 knots. The camera must slow down the rate at which it takes photos. What usually happens is that the plane speeds up to full throttle to try to achieve 35 knots groundspeed. This keeps the photo rate the same. This greatly shortens the endurance of the airplane because the power to increase propeller rpm is cubed! Yes, to double propeller rpm it requires two to the third power or eight times the power. In addition, drag increases to the square of the speed of the aircraft. In this example of increasing airspeed to 50 knots from 35 knots going into the wind to maintain a groundspeed of 35 knots increases parasitic drag by double. For these reasons aircraft fly just over their stall speed. Speeding up to fly into the wind is very detrimental to the endurance. Some stitching software highly prefer that the photos are perfectly in line with one another and are not skewed. The only way to achieve this is to fly with and against the wind. Otherwise the aircraft would have to crab into the wind to maintain its line. Another problem is that photos may not be able to be taken fast enough by the camera to be able to obtain all the necessary photos as the plane speeds downwind. In this example the plane will be flying 50 knots when heading south. This may exceed the capabilities of the camera to write to the SD card.

Flying crosswind

In the example above if the wind is at 090 degrees, meaning it is blowing from east to west (right to left) the plane would be crabbing into the wind (to the east). When it travels from waypoint 8 to waypoint 12 the aircraft would crab to the right. The amount it crabbed to the right would be dependent on the wind speed and the aircraft speed. The slower the plane is flying and the higher the wind speed the more it must crab. Crabbing leads to skewed photos. Most stitching software can handle skewed photos so it’s not a problem. In this example the aircraft will maintain its 35-knot speed throughout the flight which is best for endurance. The actual ground speed will be less depending on the wind speed, but it will be consistent in groundspeed and airspeed whether it is traveling north to south or south to north.