The Operating Environment and Aircraft Performance
Ground Effect
Countless environment factors contribute to an aircraft’s performance. An example of one element would be what is called Ground Effect. When a winged aircraft is flown at extremely low elevation, induced drag is substantially reduced. With the reduction of downwash, the air flowing from the trailing edge of the wing has no other option than to parallel the ground it encounters. Wingtip vortices used to contribute to the induction of drag are also being reduced, meaning that the earth will interfere with the formation of more massive vortexes. Low winged aircraft are affected more than a high winged aircraft due to the simple fact that lower winged aircraft have wing closer to the ground. Ground effect is also significant in regard to landing an aircraft. As the airplane passes from free air into ground effect, the reduction of induced drag as it nears the runway comes into, affect to make the airplane float past the point of intended touchdown.
In the typical cases of an airplane coming in with excessive speed, the usable portion of the runway may slip by with the aircraft refusing to settle down to land. A go around is necessity. On shorter fields, approaching with speeds aligned with safety. An airplane is usually more longitudinally stable in ground effect. It is slightly nose heavy. The downwash from the wing passes typically over the tail at an angle that produces a download on the tail. Ground effect deflects the path of the downwash and causes it to pass over the tail plane at a decreased angle. The tail plane produces more lift than usual, and the nose of the airplane tends to drop. To counteract this tendency, more up elevator is required near the ground. In take off as the aircraft climbs out of ground effect, the download on the tail plane increases and nose tends to pitch up.
Reference
Retrieved from https://www.pilotfriend.com/training/flight_training/aft_perf.htm
Hi Emmanuel,
ReplyDeleteI recently took a basic meteorology module in ERAU and this is my first time hearing about Ground Effect. It is so refreshing to read and learn something new in the student discussion board! In your post, you have mentioned that the type of wing can affect the severity of this ground effect and I was wondering if any other aerodynamic factors matter as well. Aside from aircraft structure, do other external factors like wind speed, humidity, altitude, and air pressure affect the magnitude of the ground effect? Does the size and type of aircraft matter when talking about the ground effect? Additionally, according to your post, the sudden loss in induced drag can pose significant threats to an aircraft. I am curious to know what are the methods current airports and pilots use to prevent this ground effect from causing a catastrophic accident when landing or taking off. Must the pilot take this effect into consideration when calculating landing speed and distance?
This was an interesting post overall and I like that you used photos to easier explain this phenomenon.
I have also replied the same thing on your discussion post.
Cheers!
-SH