Chapter 3 MK 7 AIRCRAFT RECOVERY EQUIPMENT AND BARRICADE SYSTEMS

CHAPTER 3 MK 7 AIRCRAFT RECOVERY EQUIPMENT AND BARRICADE SYSTEMS Present-day aircraft normally require the use of runways that are 5,000 to 8,000 feet long in order to land ashore. On an aircraft carrier, these same aircraft are stopped within 350 feet after contacting the deck. This feat is accomplished through use of aircraft recovery equipment, including an emergency barricade that brings a landing aircraft to a controlled stop by absorbing and dispelling the energy developed by the landing aircraft. This recovery equipment is commonly called arresting gear. Figure 3-1 shows the general arrangement of a typical Mk 7 arresting engine. When you complete this chapter you should be able to do the following: Explain the operations and functions of the arresting gear engine systems during recovery operations. Describe procedures for removing and replacing crossdeck pendants. Identify procedures for attaching barricade webbing to the stanchions. Describe procedures for derceving and rereeving arresting gear engine purchase cable. Identify procedures for preparing, pouring, and conducting proof-load tests on wire rope terminals. COMPONENT DESCRIPTION AND OPERATION The sole purpose of an aircraft carrier is to provide a means of launching a strike against an enemy anywhere in the world within the strike range of our aircraft. After the aircraft complete their mission, the carrier must provide a means of safely recovering them The Mk 7 arresting gear provides this means. The three major systems that make up the Mk 7 recovery equipment are as follows: 1. Emergency recovery equipment 2. Drive system 3. Engine installation Aircraft arrestments aboard carriers are classified as either a normal arrestment or an emergency arrestment. Simply stated, arrestment is accomplished in the following manner: the arresting hook of the incoming aircraft engages a wire rope cable, called a deck pendant, that spans the flight deck in the landing area. The force of the forward motion of the aircraft is transferred to purchase cables that are reeved around a movable crosshead of sheaves and a fixed sheave assembly of the arresting engine. The movable crosshead is moved toward the fixed sheave assembly as the aircraft pulls the purchase cables off the arresting engine, forcing a ram into the cylinder holding pressurized hydraulic fluid (ethylene glycol). This fluid is forced out of the cylinder through a control valve that meters the flow to an accumulator until the aircraft is brought to a smooth, controlled arrested landing (see figs. 3-2 and 3-3). After arrestment, the aircraft’s arresting hook is disengaged from the deck pendant. A retract valve is then opened, allowing fluid to be forced from the accumulator back into the engine cylinder, forcing the ram out. As the ram moves out of the cylinder, the crosshead is forced away from the fixed sheave assembly, pulling the purchase cables back onto the engine until the crosshead is returned to its BATTERY position and the crossdeck pendant is in its normal position on the flight deck. An emergency arrestment is accomplished in the same manner as a normal arrestment except that a barricade webbing assembly transmits the aircraft’s landing force to the purchase cable instead of a crossdeck pendant. We will also discuss the 3-1