EDP's switch on 747 aircrafts???

[AeroTech]

Hi,

I read somewhere that EDP's switch on 747 (classic) has 3 positions: ON/Depress/OFF.
-What is the function of this switch in the depressurization mode?
-Why this switch is different than the one in other aircrafts (just 2 positions: ON/OFF).

Thank you
Best regards.

[spannersatcx]

From the classic Maintenance Manual, what the exact emergencies are that require the pump supply off (apart from a fire) I'm not sure of suffice to say if an a/c landed in that config it would more than likely be a pump change, or what was left of it anyway!

Operation of the engine-driven pump is controlled by the operating mode selected by the position of the ENG PUMP switch located on the flight engineer's panel.

With the switch positioned to NORMAL, the depressurizing valve is de-energized and the pump will supply fluid flow (proportional to the operating speed of the engine) as demanded by the system (Fig. 5).

When the switch is positioned to DEPR, the depressurizing valve is energized and the engine-driven pump is blocked from supplying flow to the system and output pump pressure is reduced to 800-1000 psi.

The only output is the case drain flow required for pump cooling and lubrication.

Placing the ENG PUMP switch to SUPPLY OFF or placing the ENG FIRE switch on the pilots' overhead panel to FIRE position, will close the supply (fire) shutoff valve and shut off all fluid flow to the engine-driven pump and depressurize the pump.

Except for certain emergency conditions, the ENG PUMP switch should never be placed to the SUPPLY OFF position or the ENG FIRE switch to the FIRE position with the engine operating.

[PPRuNe Pop]

Please do not make multiple posts. Your other one has now been deleted.


PPP

[Dan Winterland]

In practical terms, the pump output can be swithed off by DEPRESS. This allows fluid to circulate the pump for cooling and lubrication. If you swith it OFF, you cut off this fluid. If the engine is still turning, the pump will overheat and seize. Five minutes is the max allowable time for running the pump in OFF with the engine running.

[Bolty McBolt]

Hey Aerotech

You forgot to start your post...In an inflight shutdown what does the 3 position switch on the EDP do..

You should try asking how something works rather than how it fails.


Do you know what the 2 position HYD EDP swith on other aircraft do? Do they Depressurise, cut off or both.
It seems silly to ask a question and not be able to understand the answer.

End of Rant


:\

[AeroTech]

Hi,

Spannersatcx & Dan Winterland, thank you for your answers.

-What are the emergency and abnormal conditions that require to place the EDP switch to the DEPR or SUPPLY OFF position? (in case of engine fire, we can use the engine fire switch).

-Why this switch (with 3 positions) is no longer in use on the recent aircrafts? (even on the old ones like 737-200....)

Thank you.
Best regards

[Icebreaker]

grrrr that really annoys me....

'aircraft' is plural and singular, so you can leave off the 's'

my english teacher will be proud :ok:

[forget]

Icebreaker, As you are clearly an accomplished linguist could you please let me know the words, both singular and plural, for 'aircraft' in Portugese, Spanish, Mandarin and Esperanto.

'my english teacher will be proud'.

There's a little button on your keyboard to convert lower-case letters to what we on Earth call upper-case. Try using it.

Well done 'spanners' and Dan for the civilised responses!