05-06-2015, 06:36 PM
Actually, you only see 2 when it is in flight (the other two are downholders). :-)
Many people don't realize it, but the two horizontal tails* at the back of the airplane always produce a down force in flight (except perhaps during certain maneuvering situations). If you actually take the time to look at it in detail, you'll notice they have an upside down airfoil (relatively flat on top and more curved on bottom).
*(proper term horizontal stabilizers...or in the case of some planes, like the T-38, stabilators...a combination of stabilizer and elevator, as the function is to both stabilize the airplane in pitch and 'elevate'/move the nose up and down, as well as produce a down force to counter the nose down pitching moment produced by the distribution of aerodynamic forces on the wing).
Many people don't realize it, but the two horizontal tails* at the back of the airplane always produce a down force in flight (except perhaps during certain maneuvering situations). If you actually take the time to look at it in detail, you'll notice they have an upside down airfoil (relatively flat on top and more curved on bottom).
*(proper term horizontal stabilizers...or in the case of some planes, like the T-38, stabilators...a combination of stabilizer and elevator, as the function is to both stabilize the airplane in pitch and 'elevate'/move the nose up and down, as well as produce a down force to counter the nose down pitching moment produced by the distribution of aerodynamic forces on the wing).