ATO #109 - May 19, 2000
QuestChats require pre-registration. Unless otherwise noted, registration is at: http://quest.nasa.gov/aero/chats/ LAST SCHEDULED CHAT During the summer our chat schedule will slow down to a chat every other week or so. If you want to make suggestions or requests for experts to chat with send me an email at firstname.lastname@example.org Aerospace Team Online QuestChat with Craig Hange Wednesday May 24, 2000 10 - 11 AM Pacific Craig is an aerospace engineer at NASA Ames Research Center. His research has included the Joint Strike Fighter Program and the Wright Flyer. Currently he is working on STOVL powered lift and low speed research. Read his bio at http://quest.nasa.gov/aero/team/hange.html
Regimes of Flight Art Contest, Contest ends May 26, 2000 The entries are coming in! To see the competition go to http://quest.nasa.gov/aero/events/regimes/contest/ For more information on how to participate go to http://quest.nasa.gov/aero/events/regimes/contest.html#art Teacher Feedback: Susan Walter wrote after a Parents Night with her students' Regimes of Flight art was displayed: "You can't imagine what a pleasure and joy it was to be able to share the students' art with their parents tonight. You know parents come to open house to see their child's work and there it was on the Internet!... BTW, the parents were appreciative of the art activity itself; they thought it to be quite unique, challenging and a valuable educational experience.
[Editor's Note: Craig Hange is an aerospace engineer whose research has included the Joint Strike Fighter and the Wright Flyer. Currently he is working on STOVL powered lift and low speed research. His journal comes to you in two parts. If you missed Part 1 you can find it at http://quest.nasa.gov/aero/team/fjournals/hange/ls.html Read his bio at http://quest.nasa.gov/aero/team/hange.html ]
ALL AIRPLANES ARE LOW-SPEED AIRPLANES, PART 2
By Craig Hange
Low-speed flight is characterized by flying a lot closer to what's called the stall. A stall occurs when the airflow over the wing separates from the wing and the wing no longer generates any lift. This separation occurs for a variety of reasons, but the primary causes are due to flying too slow, and flying at too high of an angle of attack. You may ask, "Aren't these also the conditions an airplane is flying at during take-off and landing?" Yes! That is exactly the problem. Also add in the possibility of a wind gust upsetting the airplane when it's close to the ground and you have a very challenging flight regime indeed. It's no wonder you have to wear your seat belt during take-off and landing. This is where the airplane designer has to make some choices. They have to make a trade off between low-speed handling and high-speed requirements. The airplane will be profitable only if it can fly at fast speeds with minimum fuel usage. This means minimizing drag and this in turn means using small wings with minimum camber generating minimal lift. However, the airplane must take-off and land, so it has to fly at low-speed during a portion of its flight. That means it needs wings with flaps and slats that generate a lot of lift, and it must also be stable at these speeds and be responsive so the pilot can correct for problems such as the wind gust. The designer has to come up with an airplane that can do both, and has to be good at both. At NASA, there are people and organizations to help with such problems. Many of the NASA engineers specialize in low-speed aerodynamics. We understand the problems and requirements for flying an airplane during take-off and landing. We understand how to fly close to the stall, and what needs to be done to keep the airplane from going beyond stall. We can help design good flap and slat systems that help during low-speed, but fold out of the way for high-speed. We also conduct tests in the low-speed wind tunnels to investigate low-speed flight. The largest wind tunnel in the world, the 80 ft X 120 ft Wind Tunnel at NASA Ames is a low-speed tunnel. In addition to testing helicopters, we also test STOL airplanes in it. STOL stands for Short Take-Off and Landing. These are airplanes that can fly so slow that they can take-off and land in less than 1000 ft. Some even use jet thrust to make up for the loss in lift from the wings. Someday these airplanes will be taking off from much smaller airports that are more convenient to your home. In our modern lives of high-speed computing and travel into space, it's easy to get excited about flying higher and faster. It may not seem glamorous or interesting to study low-speed flight. There are however, plenty of challenges that need to be addressed in the regime of low-speed flight, and these challenges will still be around when you are ready to enter the workforce. And don't forget, not all airplanes are high-speed airplanes, but ALL of them are low-speed airplanes.