Text-only reference. Published from the recorded official FAA Airframe Chapter 1 PDF. Diagrams, photographs, and figure artwork are not reproduced here; use the official FAA PDF for those materials.
Outboard flap Trailing edge sandwich panels constant-thickness core Spoiler sandwich panel tapered core, solid wedge Trailing edge sandwich panels constant-thickness core Wing leading edge Inboard flap Spoiler sandwich panel tapered core, solid wedge Aileron tab sandwich panel tapered core, Phenolic wedge Aileron tab sandwich panel constant-thickness core Trailing edge wedge sandwich panel tapered core, cord wedge into which access must be gained regularly, such as the engine and its accessories. It is designed to provide a smooth airflow over the nacelle and to protect the engine from damage. Cowl panels are generally made of aluminum alloy construction.
However, stainless steel is often used as the inner skin aft of the power section and for cowl flaps and near cowl flap openings. It is also used for oil cooler ducts. Cowl flaps are moveable parts of the nacelle cowling that open and close to regulate engine temperature. There are many engine cowl designs. Figure 1-43 shows an exploded view of the pieces of cowling for a horizontally opposed engine on a light aircraft. It is attached to the nacelle by means of screws and/or quick release fasteners. Some large reciprocating engines are enclosed by “orange peel” cowlings which provide excellent access to components inside the nacelle. [Figure 1-44] These cowl panels are attached to the forward firewall by mounts which also serve as hinges for opening the cowl. The lower cowl mounts are secured to the hinge brackets by quick release pins. The side and top panels are held open by rods and the lower panel is retained in the open position by a spring and a cable. All of the cowling panels are locked in the closed position by over- center steel latches which are secured in the closed position by spring-loaded safety catches.
An example of a turbojet engine nacelle can be seen in and easily removable panels which can be opened and closed during maintenance. A nose cowl is also a feature on a jet engine nacelle. It guides air into the engine. Empennage The empennage of an aircraft is also known as the tail section. Most empennage designs consist of a tail cone, fixed aerodynamic surfaces or stabilizers, and movable aerodynamic surfaces. 1-19 1-20 Metal member bonded to sandwich Wooden members spanwise and chordwise Glass reinforced plastics sandwich the core Honeycomb sandwich core Metal wing spar The tail cone serves to close and streamline the aft end of most fuselages. The cone is made up of structural members like those of the fuselage; however, cones are usually of lighter construction since they receive less stress than the fuselage. [Figure 1-46] The other components of the typical empennage are of heavier construction than the tail cone. These members include fixed surfaces that help stabilize the aircraft and movable surfaces that help to direct an aircraft during flight.
The fixed surfaces are the horizontal stabilizer and vertical stabilizer. The movable surfaces are usually a rudder located at the aft edge of the vertical stabilizer and an elevator located at the aft edge the horizontal stabilizer. [Figure 1-47] The structure of the stabilizers is very similar to that which is used in wing construction. Figure 1-48 shows a typical vertical stabilizer. Notice the use of spars, ribs, stringers, and skin like those found in a wing. They perform the same functions shaping and supporting the stabilizer and transferring stresses. Bending, torsion, and shear created by air loads in flight pass from one structural member to another. Each member absorbs some of the stress and passes the remainder on to the others. Ultimately, the spar transmits any overloads to the fuselage. A horizontal stabilizer is built engine.
the same way. The rudder and elevator are flight control surfaces that are also part of the empennage discussed in the next section of this chapter.
Flight Control Surfaces
The directional control of a fixed-wing aircraft takes place around the lateral, longitudinal, and vertical axes by means of flight control surfaces designed to create movement about these axes. These control devices are hinged or movable surfaces through which the attitude of an aircraft is controlled during takeoff, flight, and landing. They are usually divided into two major groups: 1) primary or main flight control surfaces and 2) secondary or auxiliary control surfaces. 1-21 1-22 Skin Bulkhead Frame Stringer Longeron but more lightweight construction. Elevator Rudder Trim tabs Vertical stabilizer Horizontal stabilizer SkinSpars Rib Stringer Primary Flight Control Surfaces The primary flight control surfaces on a fixed-wing aircraft include: ailerons, elevators, and the rudder. The ailerons are attached to the trailing edge of both wings and when moved, rotate the aircraft around the longitudinal axis. The elevator is attached to the trailing edge of the horizontal stabilizer.
When it is moved, it alters aircraft pitch, which is the attitude about the horizontal or lateral axis. The rudder is hinged to the trailing edge of the vertical stabilizer. When the rudder changes position, the aircraft rotates about the vertical axis (yaw). Figure 1-49 shows the primary flight controls of a light aircraft and the movement they create relative to the three axes of flight. Primary control surfaces are usually similar in construction to one another and vary only in size, shape, and methods of attachment. On aluminum light aircraft, their structure is often similar to an all-metal wing. This is appropriate because the primary control surfaces are simply smaller aerodynamic devices. They are typically made from an aluminum alloy structure built around a single spar member or torque tube to which ribs are fitted and a skin is attached. The lightweight ribs are, in many cases, stamped out from flat aluminum sheet stock. Holes in the ribs lighten the assembly. An aluminum skin is attached with rivets. Figure 1-50 illustrates this type of structure, which can be found on the primary control surfaces of light aircraft as well as on medium and heavy aircraft.
Lateral axis (longitudinal stability) Aileron—Roll Rudder—YawElevator—Pitch Longitudinal axis (lateral stability) Vertical axis (directional stability) Aileron Roll Longitudinal Lateral Rudder Yaw Vertical Directional Elevator/ Stabilator Pitch Lateral Longitudinal Primary Control Surface Airplane Movement Axes of Rotation Type of Stability three axes of flight. 1-23