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MAINTENANCE MANUAL
PORT
Pitot-Static System Component Location
Figure 1 (Sheet 1)
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MAINTENANCE MANUAL
ELECTRONIC EQUIPMENT RACK, E2
OF FLOOR BEAM
RIGHT STANCHION
ELECTRICAL AND ELECTRONICS COMPARTMENT
Pitot-Static System Component Location
Figure 1 (Sheet 2)
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E17394
A
747-400
MAINTENANCE MANUAL
DRAIN PLUG VISCO JET DRAINDRAIN ASSEMBLY DE
SOURCE SELECT VALVE
F
Pitot-Static System - Component Location
Figure 1 (Sheet 3)
D13610
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MAINTENANCE MANUAL
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, are provided to aid in preventing the pitot and static systems from becoming interconnected. All the equipment receiving pitot and static pressure inputs use this type of connector except the elevator feel computer, the pitot-static probes, and the static pressure ports which use male and female non-color-coded connectors which cannot be interconnected.
7. Operation_________
A. Functional Description
(1) The pitot-static system consists of four independent pitot-static subsystems, one alternate static pressure subsystems, and two dedicated static pressure subsystems. The theory of operation for each of the subsystems is similar. The inputs and distribution are discussed in the following paragraphs.
(a) Pitot Pressure Sensing
1) For each of the four pitot systems, a pitot-static probe is located on the outside of the airplane. In this position, dynamic or ram pressure created by the forward motion of the airplane pressurizes the entire pitot portion of each subsystem.
2) A drain hole, located in the bottom of the probe head 2.25 inches aft of the tip, exits to the atmosphere to drain any moisture that may be collected.
(b) Static Pressure Sensing
1) Static pressure ports are located on the top and bottom of the pitot-static probe head, approximately 4.5 inches aft of the tip. The forward set of ports (one on top and two on the bottom) open into static line S1 and the aft set (one on top and two on the bottom) open into static line S2 The surface of the probe in the area of the static ports is designed to provide an accurate sensing of ambient air pressure as independent as possible of airspeed. To further assure accurate ambient pressure sensing, static pressure inputs are equalized by cross-connecting each set of static ports to a set of static ports on the opposite side of the airplane through a common manifold (see Fig. 2). Note that static ports from upper probes connect to static ports on lower probes. This tends to reduce any error caused by a localized pressure anomaly.
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