Learning Objective: Identify components and conditions of the ECS for the cockpit, cabin area, and the nose avionics compart-ment of the SH-60B helicopter.

The SH-60B helicopter cabin cockpit and nose bay environments are controlled by the ECS, which provides both heating and air conditioning in a range of 2 C to 71 C. Supplementary or backup air circulation is provided at all crew stations by manually controlled air inlets for out-side air. The ECS (fig. 3-19) consists of an air-cycle machine (ACM) (fan, turbine, and compressor), bleed-air ducting, necessary controls and valves, water separator, distribution system, air inlet, and heat-exchanger exhaust duct. The bleed-air portion of the ECS functions from two sources

Figure 3-19.- Environmental control system.

of bleed air- engine and auxiliary power unit (APU). The energy extracted from bleed air is used to drive the ACM's cooling fan and compressor. Bleed air is applied to the ACM through a modulating valve, which functions as both an on/ off valve and pressure regulator. Air source selection is accomplished by means of the AIR SOURCE ECS/ START switch on the overhead control panel. In the ENGINE position, the engine bleed air is selected as a source. In APU position, APU bleed air is used as the air source. With ECS selected ON (from engine source), maximum torque available is reduced by 3.5 percent. An overpressure switch, located on the ACM side of the modulating valve, senses high air pressure. In an overpressure condition, the over-pressure switch illuminates an advisory panel light to indicate ECS HI PRESS. System shutdown does not occur during an overpressure, since the ACM is capable of withstanding full bleed-air pressure, delivered by the engines or APU. Power is supplied from the No. 2 ac primary bus and the No. 2 dc primary bus, through two circuit breakers, both on the sensor operators (SO) circuit breaker panel, marked ECS PWR and ECS CONTR, respectively. If ECS fails, cooling air must be introduced into the nose avionics compartment by pulling the nose door cooling damper control located on the left-hand side of the console.