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maniamcool

NO LAND 3 EICAS warning on take-off?

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Hi,

 

I got this warning on the EICAS on 2 occasions just after take-off. It's really weird that such a warning would appear during the initial stages of the flight.

 

Both flights were done on heavy payloads with GW of around 380000kg. Flights with lower weights are uneventful and the warning does not appear.

 

The warning that stays during cruise and doesn't go away. I'll report back during landing if it clears itself.

 

Any ideas?

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Any ideas?

 

Sounds a lot like the aircraft isn't being configured properly. If you haven't flown the tutorial, please do so. Additionally, make sure you go through your pre-flight carefully. There are a number of steps that are slightly different within the 744 fleet (pertaining to FMC options), and slightly different from the 737 and 777 that can trip you up.

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Did you also get a split IRS message on the CDU? I got that along with a no land 3 a few times I have tested the bird.

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Did you also get a split IRS message on the CDU? I got that along with a no land 3 a few times I have tested the bird.

 

Ah yes I did! Both flights I made the mistake of disconnecting ground power before switching to the APU GENs. Got the Split IRS message after switching power to the APUs and went ahead with my pushback..etc, didn't think much about that message.

 

Could that be the cause?

 

 

 

I'll look through the tutorial to see if I missed anything. 

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Both flights I made the mistake of disconnecting ground power before switching to the APU GENs.

 

This is why. Fully power down the IRSs, and then re-spin them.

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Just out of curiosity, why does this cause the autoland to fail? Don't the IRS' just keep humming along on DC power when you screw up the gen config?

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Because when AC power is OFF the LEFT and RIGHT IRS units draw DC from the battery while the CENTRE IRS drops (there is an automatic relay to conserve battery). The only case that the CENTRE IRS will draw DC power is if DC BUS 3 is NOT powered and then only for 5 minutes.

 

There is your technical explanation.

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Ah yes I did! Both flights I made the mistake of disconnecting ground power before switching to the APU GENs. Got the Split IRS message after switching power to the APUs and went ahead with my pushback..etc, didn't think much about that message.

 

Could that be the cause?

 

 

 

I'll look through the tutorial to see if I missed anything. 

You are not alone, I took off from KPAE with "no autoland 3": and message:  "IRS align mode C".

According to the POS REF page (3/3) IRS L and R showed some numbers, but C was empty. 

 

Now after reading this post this all makes sense, Ik made the same mistake playing around with the power. 

 

The flight was OK, but I wonder: what would have happend if, in this situation, you would lose GPS for some reason?

Can you safely navigate a longer distance with only 2 IRS'es and no GPS? Or would the nav accuracy degrade in time?

(I used to fly Ralph Tofflemire classic 747 with the simufly INS, if you had 3 working INS units, you could have your nav checked via VOR's (triple mixing; if one unit failed - it happened!! - the triple mixing was gone).

 

Regards,

 

Wijnand Lindelauf  (EHBK)

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Did you also get a split IRS message on the CDU? I got that along with a no land 3 a few times I have tested the bird.

 

Had that myself, I think it has something to do with losing power temporarily - resulted in me getting the No Land 3 message too.

 

EDIT:

I can see it is already discussed in detail above. My bad.

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I received this message at the beginning of the tutorial flight (except that I started with ground power connected at a gate and IRSs not aligned) and continued to see it throughout the flight.  I had accidentally turned off the right IRS after all three were aligned while still on ground.  I did turn it back on and thought it was on long enough to realign, but I continued to get this message.  I didn't know how to tell if the third IRS had realigned.   On arrival I received "Land 2" message instead of "Land 3" (I chose a manual landing as I usually do). 

 

Mike

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