11
GEAR DOWN DISPATCH AIRSPEED WARNING SWITCH
FUEL TANK AIRSPEED WARNING SWITCH
8
GALLEY AND TOILET EXHAUST
CENTRAL AIR DIFFERENTIAL
DATA COMPUTERS PRESSURE SWITCH 6
2 DRAINS
4 DRAINS 3
ALTITUDE RATE 4 DRAINS
UNIT (AUTOPILOT) 2
5
MAIN EQUIPMENT CENTER
Pitot-Static System Component Location
Figure 1 (Sheet 1)
T33346
EFFECTIVITY
ALL
703 Page 2
34-11-00
Apr 25/94
4. Static Source Selector Valves (Fig. 1, Sheet 2)
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A. Two static source selector valves provide the captain's and the first officer's pitot-static systems with the capability of choosing which static pressure sensors will be used. Static pressure inputs to air data instruments and central air data computers are supplied from the selector valves, which select static pressure inputs from either pitot-static probes (NORMAL position) or alternate static ports (ALTERNATE position).
B. The valve is operated by a toggle which is guarded in the NORMAL position The captain's selector valve is located near the cabin floor below the captain's auxiliary instrument panel. The first officer's selector valve is opposite in location.
5. Drains (Fig. 1 and 2)
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A. Drains are located on walls or uprights near the floor level of the lower decks of the airplane. They appear as a small cylinder terminating a vertical run of pitot or static tubing. Drains are located in the left crawlway beside nose wheel well; in the right crawlway beside nose wheel well in the main equipment center; in the forward cargo area; and in the aft bulk cargo area.
B. As installed, two types of drains act as a permanent sump. One type is a two-part device with an upper half containing a seal spring loaded in the closed position, and a lower half that locks in place to protect the seal opening. The lower portion of the drain assembly may be removed, turned upside down, and reinserted into the upper assembly. With the lower half held in this position by hand pressure, the seal in the upper half is held in the open position. The assembly now functions as a drain and any material collected in the sump will pass out of the pitot-static tubing. Upon reassembly, it reverts to its function as a sump. The other type is a simple plug that, when removed, allows any material collected in the sump to pass out of the pitot-static tubing. Upon reassembly, it reverts to its function as a sump.
6. Pitot-Static Tubing (Fig. 2)
___________________
A. The sensed pressures are distributed through the airplane in metal tubing mounted on the walls and bulkheads with rigid brackets. Connections and branchings of the tubing are accomplished through "T" fittings and union fittings requiring tools for disassembly. Connections from the rigid tubing system to the various delivery points are made through flex hoses and quick-disconnect fittings or threaded fittings.
B. Quick-disconnect connectors are designed to seal shut when disconnected thereby maintaining the pitot-static system integrity. All connectors of this type used on the static pressure system are colored yellow and all connectors used on the pitot pressure system are red. This color code, coupled with polarized plugs, prevents the pitot and static systems from becoming interconnected. All the instrumentation receiving pitot and static pressure inputs use this type of connector except the flight recorder, which uses male and female non-color-coded connectors which cannot be interconnected.
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