737 Pneumatics System Question

Date:         20 Mar 97 02:38:32 
From:         Jim Messina <sky@neosoft.com>
Organization: NeoSoft, Inc.
Followups:    1 2
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The 737-300 engine bleed valves are (according to an Aircraft Flight
Manual):

1. Shutoff valves
2. Pressure regulator valves
3. Reverse flow check valves

Are there versions of 737s that do not use the Reverse flow check valve
feature?

To extend the idea further, will you ever be able to heat up the engine
cowl inlets with the Engine Anti-ice switches "on", while on the ground,
with ONLY the APU running?

(for those who have no knowledge of the 737, the Engine Anti-ice for an
engine is supplied by it's own bleed air but "upstream" or before the
engine pneumatic bleed valve, when the engine is running. The engine bleed
valve does NOT have to be open to use engine anti-ice protection.

The APU, Auxiliary Power Unit, can supply bleed air to the pneumatic
system manifolds but "downstream" or outside of the where the engine bleed
valves supply air, for air condition purposes primarily, and engine
starting).

---
Bluecoat  - Jim Messina
http://www.neosoft.com/~sky