TAIL DESIGNINTRODUCTIONThe horizontal tail and vertical tail along with the wing are called lifting surfaces. The main difference between wing design and tail design comes from the main function of the tail which is different from that of the wing. The primary function of the wing is to generate maximum or substantial lift, while the tail is designed to operate normally with only a fraction of its ability to generate the required lift potential. During a flight mission, if at any time the tail reaches its maximum angle of attack which refers to the rear stall angle; is an indication of a design process error. The tail of a conventional unmanned aerial vehicle often has two components, the horizontal tail and the vertical tail, and serves two primary functions: Trim (longitudinal and directional) Stability (longitudinal and directional) )Control (longitudinal and directional) Trim refers to the generation of a lift force that acts through the tail moment arm around the center of gravity, balancing another moment produced by plane. For the horizontal tail, trim mainly means balancing the moment generated by the wing. Therefore, longitudinal trim is the first and foremost function of a horizontal tail and is also called balance. A rear-mounted horizontal tailplane has a negative angle of attack of about 2 to 3 degrees to balance the wing's pitching moment. The vertical tail is not necessary to generate a longitudinal trim force because the aircraft is generally left-right symmetrical, that is, an aircraft is symmetrical with respect to the XZ aircraft. Therefore, the main function of the vertical tail is directional stability. The second function of the tail is to provide stability. The stability of the aircraft is d...... middle of paper ......the balance of wing and tail moments is given by:Mcgwing = Mcgtail or (Lwing * lwing) = (Ltail * ltail) or Ltail= (( Lwing*lwing))/ltail=(233*0.0625)/1.43=10.18N where, Lwing= lift produced by the wingLtail= lift produced by the tail lwing= moment arm of the wing ltail= tail moment arm Horizontal tailgate = 10.18NNote: The tail arm represents 65% of the fuselage length. Usually, the tail arm is approximated by considering 65% to 75% of the fuselage [1]. REFERENCES: [1] “Airfoil and Geometry Selection” - Page 33-67-Airplane Design: A Conceptual Approach by Daniel P Raymer - AIAA Educational Series.[2] “Wing and Tail Design” - Page Aircraft Design: A Systems Engineering Approach by Mohammad H Sadraey- Wiley Aerospace Series[3] Shevell, RS (1989) Fundamentals of Flight, 2nd edition, Prentice Hall[4 ] Nelson, R. (1997) Flight stability and automatic control, McGraw Hill