PPRuNe Forums - 744 NAI

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My understanding is that when you select NAI, the idle thrust is increased. If so, does this happen on the ground?

e.g. temperature is less than +10 and there is visible moisture, would selecting NAI affect the idle thrust during taxi, and how does it affect the flare when you close the thrust levers?

Sorry if this doesn't make sense, hard to word my question :ugh: :ugh: :ugh:

Sorry but where does this information come from? Which engine?
On our B744 there is no interaction from the NAI to the fadec.
The NAI switch does not affect Eng speed.

You made me go and look through the AMM as I was not sure.

Oh dear, maybe I have got it all wrong. :\ :\ I don't fly the aircraft, and I can't recall where I got the information from, but I was under the impression that with the NAI selected to ON

1) The nacelle anti-ice valves open.
2) NAI is displayed in green next to the N1 indications on the primary
EICAS display.
3) The EEC's increase idle as required.

If this is not the case, then what is the point of entering the altitude at which NAI is expected to be used in the descent forecast page, if it has no impact on the descent gradient?

Quote:

Originally Posted by TotalBeginner

3) The EEC's increase idle as required.

When NAI is selected on, air is bled from the HP air offtake. The EEC will maintain idle speed by increasing the fuel flow.

Sorry Swedish Steve, but you are wrong! (at least with regards to RB211 powered -400's)

Quote:

The EEC will maintain idle speed by increasing the fuel flow

Misleading rubbish I'm afraid.

FACT:

When NAI is selected ON, the EEC automatically selecte APPROACH IDLE N1, which if you had IDLE selected prior to selecting NAI on would increase thrust produced by the engine.
This is to guarentee sufficient hot air for the system to operate correctly.

Totalbeginner:

Quote:

then what is the point of entering the altitude at which NAI is expected to be used in the descent forecast page, if it has no impact on the descent gradient?

It does, you are correct!

Ref FCOM 1/ TECH, Section 20:

EEC Idle selection:
The EEC selects minimum idle or approach idle. Minimum idle is a lower thrust setting than approach idle (N1). Approach idle is selected when:
- Nacelle anti-ice in ON
and/ or
- Flaps are in the landing position (25 or 30)
Approach idle decreases acceleration time for go-around, and is maintained until 5 seconds after touchdown, when minimum idle is automatically selected.