PART III-MANAGEMENT OF SYSTEMS

             low B.P.C. pressure and low forward speed leading
             to reduced fuel flow at the burners. Goblin Mod.
             1130 increases both the B.P.C. pressure setting and
             minimum fuel flow. Until the Mod. is embodied
             it is recommended that, to reduce the possibility of
             flame-out engine r.p.m. in stall manoeuvres should
             not be less than the following:-

                 20,000 ft.	..	..	5,500 r.p.m.
                 30,000 ft.	..	..	7,500 r.p.m.
                 35,000 ft.	..	..	8,500 r.p.m.

       (iii) During sustained turns at all altitudes there may be
             a tendency for engine r.p.m. to fall off slightly, up
             to a maximum of 1,000 r.p.m. The original r.p.m.
             will be regained when straight and level flight is
             resumed.

    (b) H.P. pump isolating check

        (i) Increase engine r.p.m. to 4,000 and set the isolating
            switch ON. This should result in an increase of
            about 1,000 r.p.m., pre-mod. 1130, or of about 800-
            900 r.p.m. post-mod. 1130. Should the desired
            increase not be achieved the system is unserviceable
            and the aircraft must not be flown.

       (ii) After the check return the switch to off and note
            that the r.p.m. drop to the original figure.

    (c) Use of the H.P. pump isolating switch for take-off

        If the isolating switch has been set to ON for. take-off
        it must be returned to off at a safe height whilst still at
        full throttle. This should cause little or no drop in         
        r.p.m.; the engine can then be throttled to the desired
        power. If the isolating switch is switched to off after
        power has been reduced a sudden drop of approximately
        1,000 r.p.m. will result.

    (d) Use of the H.P. pump isolating switch in flight

        If a sudden inexplicable drop in engine r.p.m. occurs the
        throttle should be closed and the isolating switch set to
        ON. (If the isolating switch is not switched to ON
        within 4 seconds there is a probability of flame extinc-
        tion). Once the switch has been set to isolate it must

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