T-45A UJPT, E2-C2, ADV, & IUT Eng-26
Engineering Review
4.
EDP bypass valve
a.
Location: bottom, left aft fuselage
b.
Description
(1) Reduces load on engine by by-
passing output of EDP to return
side of system during low rpm
periods (engine start)
(2) Bypass in effect from 0% to
45% rpm
(3) Reset above 45% rpm (above
1,800 psi) by pressing HYD 2
RESET button
(4) Bypass valve activates when en-
gine rpm drops below 42%, such
as during engine flameout
5.
Emergency package assembly (See IV.F.3)
E.
Emergency hydraulic system description:
The emergency hydraulic system acts as a
backup to the HYD 2 system by deploying the
RAT, when the HYD 2 pressure falls below
acceptable levels. The RAT automatically
extends whenever HYD 2 EDP pressure falls
below 1,500 psi. Since the RAT is a fixed
displacement pump, emergency hydraulic
pressure will fluctuate between 2,500 and
3,000 psi displayed on the HYD 2 gauge,
whenever the RAT is in operation. Extension of
the RAT does not put the HYD 2 EDP into
bypass
CAUTION: Placing EMER FLAPS switch to
the DOWN position when normal HYD 1
pressure is available will cause the hydraulic
fluid to rapidly overheat, possibly causing a
HYD 1 seal failure resulting in HYD 1 system
failure.
(8-03) Original
Page 26-25
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