What are the winds aloft?
Flight training prior to the cross-country phase was seldom concerned with winds aloft. So why deal with them now? Winds aloft have a significant effect on the aircraft’s ground speed. Even though the airplane indicates 80 mph during cruise flight, the ground speed may well be different. Let’s assume that winds aloft are indicating that a 20 mph headwind will be encountered during the flight. The ground speed will then become 60 mph. Using the example J3 Cub, it was determined that 2.1 hours of fuel was available, plus the 30 minute reserve, before needing to land. At 2.1 hours and a 60 mph ground speed, the distance covered will only be 126 miles; 42 fewer miles than when flying in a no wind condition. The headwind encountered may dictate that a fuel stop is necessary before safely reaching the destination airport. Conversely, if the winds aloft indicate that a 20 mph tailwind will be encountered, the groundspeed will be 100 mph. At 2.1 hours and a 100 mph ground speed, approximately
