104: Airframe Fundamentals

104.1 Explain the purpose of the wing fold system.

The combined hydraulic power system supplies hydraulic power to the wing fold and automatic jury strut system. Hydraulic power operates actuation cylinders that unlock, fold spread and lock the outer wing panels. Mechanically actuated timer valves also control this sequence of events in the fold and spread cycles. Hydraulically operated check valves, priority valves, lock valves and flow regulators aid in the control of the system. The wing fold selector valves solenoid or manually controlled, directs hydraulic fluid to the system components to fold and spread the wings. Before selection, the flaps shall be in the 20-degree position. All this occurs to save space on the aircraft carrier and allow easier movement on the deck.

104.2 Explain the term artificial feel as it applies to the flight control system.

The hydraulic portions of the flight control system are incapable of being reversed. Hydraulic cylinders (actuators) move in response to pilot or copilot input to move the actuators and thus move the pilot or copilot control column or pedals. Because of this, the aerodynamic forces that exist on the control surfaces are not fed back to the cockpit controls. To compensate for this, an artificial feel system in the control system produces a simulated force on the cockpit controls.

104.3 Explain the purpose of the tailskid.

The tailskid is lowered and raised in conjunction with the landing gear and is used to prevent damage to the aircraft.

104.4 State the purpose of the main gear extender system.

An internal main gear extender system provides additional deck clearance during catapult launching operations by extending the main gear struts.

104.5 State the purpose of the landing gear emergency extension system.

If a combined or flight hydraulic system failure occurs, the landing gear and tailskid must be extended with an emergency pneumatic system. The system consists of a 3,000-psi nitrogen bottle, a nitrogen release valve, two pressure operated dump valves, and shuttle on the gear and tailskid actuators. Nitrogen is released from the bottle by actuating the emergency landing gear handle that is linked mechanically to the release valve. The released nitrogen positions the dump valves to open the uplines of the landing gear and door cylinders and the tailskid lift actuator to return fluid to the reservoir. At the same time, nitrogen enters the down side of the cylinders through shuttle valves and extends the cylinders. The system lowers the landing gear only once because the nitrogen cannot be recharged in flight.

104.6 State the purpose of a hydraulic patch test.

Contamination analysis is used to determine the particulate level of a hydraulic system and the Presence of free water or other foreign substances. The methods used to identify and measure contamination is patch testing, electronic particle count analysis, and halogen testing. Patch testing is the primary contamination measurement method used at all levels of maintenance. The P/N57L414 contamination analysis kit (fig. 4-3) is used to perform patch testing. In the patch test method, a fluid sample of known volume is filtered through a filter membrane of known porosity. When the fluid passes through the filter, all particulate matter in excess of a size determined by the filter characteristics is retained on the surface of the membrane. The retention of particulate matter causes the membrane to discolor proportionally to the particulate level of the fluid sample. Free water will appear either as droplets during the fluid sample processing or as a stain on the test filter. The typical color of contamination in any given system is usually uniform. The degree of filter membrane discoloration correlates to a level of particulate contamination. By visually comparing the test filter with contamination standards that represent known contamination levels, the contaminant level of the system can be determined.

104.7 Identify the location of the bail out hatch.

The bailout hatch is at the forward end of the cabin floor, immediately aft of the cockpit. The hatch consists of a floor panel, at T-handle, and a drop-away hatch faired with the underside of the fuselage. To open the bailout hatch, theT-handle must be lifted to unlock the floor panel. The floor panel may then be pivoted upward by means of a track and roller arrangement and moved forward with a forward lifting motion. The forward edge of the panel strikes two hatch releases that unlock the dropaway hatch and permit it to fall free of the aircraft because of slipstream. When the floor panel is in the full vertical position at the forward side of the hatch opening, it protrudes below the underside of the fuselage to provide a wind block to facilitate bailout.

104.8 State the hazards associated with the following : a. Movable surfaces; is a hazard to personnel, GSE, and any other equipment placed in the way. Items placed in the path of the moveable surfaces are in risk of being crushed, punctured, dented, cracked or just scratched. All of which can be either replaced or repaired. Personnel trapped between movable surfaces face a much bigger risk. Serious injury or even death can occur. b. Foreign Object Damage; is a hazard to the operation of turboprop engines. Damage can occur in parking, storage area and maintenance procedures and during engine installation and engine ground operation. Perform frequent and periodic inspection of engine nacelles, inlet ducts and storage areas.

104.9 State the purpose of the cargo cage.

The cargo cage provides a means of securing cargo for carrier operation. The cage consists of a series of stanchions between the overhead rails and corresponding floor tracks; horizontal bars closing of ends of the cage; and adjustable-length vertical side posts fitted between the stanchions to form the sides.

104.10 Define the term corrosion.

Corrosion is the electrochemical deterioration of a metal because of its chemical reaction with the surrounding environment. This reaction occurs because of the tendency of metals to return to their naturally occurring states, usually oxide or sulfide ores. When a water solution containing soluble salts is present, corrosion of many alloys can occur easily at ambient temperatures.

104.11 Discuss the following types of corrosion: a. Uniform surface Uniform surface corrosion results from a direct chemical attack on a metal surface and involves only the metal surface. On a polished surface, this type is of corrosion is first seen as a general dulling or etching of the surface and if the attack is allowed to continue the surface becomes rough and possibly frosted in appearance.

b. Pitting The most common corrosion on aluminum and magnesium alloys is called pitting. It is first noticeable as a white or gray powdery deposit, similar to dust, which blotches the surface. When the deposit is cleaned away, tiny pits or holes can be seen in the surface. Pitting corrosion may also occur in other types of alloys.

c. Exfoliation Exfoliation is an advance form of intergranular corrosion where the surface grains of a metal are lifted up by the force of expanding corrosion products occurring at the grain boundaries. The lifting up or swelling is visible evidence of exfoliation corrosion. Exfoliation occurs on extruded, rolled, wrought and forged high strength aluminum and magnesium parts.


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