AIRFRAMES AND ENGINES

Transcription

1 5 CHAPTER 1 AIRFRAMES AND ENGINES AIRCRAFT CLASSIFICATIONS An aircraft may be classified by wing type, high wing or low wing; by the number of engines it has, single engine or multi engine; or by the type of under carriage it has, fixed gear, retractable gear, floats, skis, or amphibious. PARTS OF AN AIRCRAFT 1. Propeller 8. Wing 2. Engine Cowl 9. Flap 3. Windshield 10. Vertical Stabilizer 4. Door 11. Horizontal Stabilizer 5. Wing Strut 12. Rudder 6. Landing Gear 13. Elevator 7. Fuselage 14. Aileron Fig. 1.1

2 6 FUSELAGE CONSTRUCTION Truss Type Fuselage Truss type fuselages are either wood framed or steel tube framed and fabric covered. Ultra light aircraft often use truss type construction. Truss Type Fuselage Fig. 1.2 WING CONSTRUCTION Spars Wing spars are the main members of the wing and run the length of the wing. They are stiffened against torsion (twisting stress). Spars also run the length of the horizontal stabilizer and vertical stabilizer. Front Spar Ribs Rear Spar Compression Struts Fig. 1.3 Compression Struts Compression struts join the front and rear spars of lifting surfaces and are designed to take compression loads. Ribs Ribs run from the leading edge to the trailing edge of lifting surfaces. They give the wing, the horizontal stabilizer and the vertical stabilizer their shapes.

3 7 Web Rib Truss Rib Fig. 1.4 Web Rib Web rib wings will usually be aluminum covered. The aluminum will carry some of the air loads. Truss Rib Truss type wings will usually be fabric covered, usually with Stits material. The fabric carries none of the load; the truss structure carries it all. Internal drag and anti-drag wires between the compression struts may be required to aid in load carrying. Batten Tubes Dacron covered Batten Tube Fig. 1.5 Monocoque Control Surfaces Monocoque structures have very little internal structure - no spars or ribs. Control surfaces, such as ailerons, elevators, rudders and flaps are not subjected to such high air loads and therefore may be of monocoque construction. Metal control surfaces are usually corrugated for increased stiffness.

4 8 Corrugated Monocoque Control Surface Fig. 1.6 Cantilever Wings Cantilever wings are wings that are entirely supported by the wing spars. Cantilever Fig. 1.7 Semi-Cantilever Wings Semi-Cantilever wings are externally braced by wing struts from the fuselage to the mid-section of the wing.

5 9 Semi-cantilever Fig. 1.8 Ailerons Ailerons are movable surfaces attached to the rear spar of the wing toward the wing tip, which provide roll control by increasing or decreasing the angle of attack of a wing. Left Aileron Down, Right Aileron Up, Roll Right Fig. 1.9 Flaps Flaps are movable surfaces attached to the rear spar of the wing and are used to provide increased lift at low speeds by increasing the angle of attack of the wing. They are either electrically or mechanically operated. Flaps Down Fig Flaperons Flaperons are a combination of flaps and ailerons. They both droop to function as

6 10 flaps and they will work as ailerons in the retracted or deployed position. TAIL SECTION OR EMPENNAGE The tail section is required to provide stability in pitch and yaw. Zephyr Rans Lazair Types of Tails Fig Horizontal Stabilizer The horizontal stabilizer is an airfoil set on the tail with a slightly negative angle of attack to balance the aircraft weight and to provide pitch stability. A disturbance such as a gust of wind may increase the lift on the wings. The aircraft will tend to pitch up forcing the tail down. The downward movement of the horizontal stabilizer will cause it to meet the relative airflow at a higher angle of attack, increasing its lift, and forcing it up to regain the original balance of the aircraft. A sudden loss of lift by the wings will tend to cause the nose to pitch down. The upward movement of the horizontal stabilizer will cause it to meet the airflow at a negative angle of attack, which will force it downward to regain the original balance of the aircraft. Aircraft pitches up, forcing the horizontal stabilizer to meet the airflow at a higher angle of attack, increasing its lift, forcing it up. Aircraft pitches down, forcing the horizontal stabilizer to meet the airflow at a negative angle of attack, forcing it down. Fig. 1.12