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No Land 3 when loading Aircraft-State “short”

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Posted (edited)

Hello everyone,

I am fairly new to the PMDG 747 and Boeing Planes in general, so this might be an beginner mistake. Anyways I start my flights with the Aircraft Sate “short”. Mostly I am flying the 747-400 freighter version. Unfortunately I always have the “No Land 3” alert displayed when I am flying. After my research, I found out that this is (in most cases) caused by letting the power get interrupted. In my case this can only be caused when going from APU to engine power supply, due to the fact that the APU is already running when loading the state of the aircraft and there’s no disconnecting of an external power unit. But somehow I can’t figure out what I am doing wrong. While being pushed back, I turn first all four engines on, then turn the APU off. As far as I can judge it, there’s no interruption. 
Another idea which I had was that the problem is caused by a wrong procedure of loading the aircraft state. My steps are: 1. Open P3D 2. Choose airplane, location, weather and time 3. Load the scenario (Aircaft is now in the default take off state) 4. Pressing Shift + 4 5. PMDG Setup 6. Panel Sate load 7. LSK4L 8. Wait the shown time and let the countdown complete 9. Done


Can anyone help me and tell me what’s actually causing the problem in my case and how I can fix it?


Thank you in advance,


Edited by JKIE

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I'm sure in your searching, you found this thread, which does explain what is going on and so i assume you've got it figured out now.


Essentially, what happens (or should happen) is that your nav system is aligned when stationary, and you are good to go when this is done, but if you lose power to one of the systems, then your nav capability is diminished and the warning 'No Land 3' comes up, meaning that the criteria for a landing with multiple redundant systems back up is diminished. You can still do a landing, just not with as much avionics back up as would normally be the case, so this means that very high category landings in poor visibility with a low decision height (i.e. ones which rely on the autoland capability to a very high degree) would not be permitted.

There is no way to realign a nav system's IRS/INS when moving because it requires the gyros to not be detecting any movement. There was an incident a few years ago where a crew tried to do that (it was on an ATR-42 of Santa Bárbara Airlines - Flight SB518 from Merida to Caracas, venezuela). The crew mistakenly believed they could do the alignment whilst taxying (which of course you can't). With an ATR, there's no APU, so you need to crank an engine before pushing back and run it with the prop brake on and make sure that is the selected power source of course, which should have been a bit of a clue as to why not doing that was a bad idea, particularly as that is the standard procedure. As a result of not doing all that, the crew of SB518  took off into mountainous terrain in poor visibility with no AHRS (i.e. they had no primary flight displays and could not get them to appear either since they are reliant on the IRS being aligned), with predictably dire results (they crashed into a mountain, killing all on board).

The correct procedure with pretty much all aeroplanes is to set up everything in your nav system with ground power (or the APU running), and make sure your systems are utilising that power source, but when preparing to push back, you need to start your APU in good time, then when the APU is up and running, make sure your avionics power source is the APU and that the electrical bus switch connections are correct for that. You can crank an engine when pushing off stand, in which case you could select that as the power source, but technically you need ATC's permission to do that (since it is regarded as an engine test type of situation when cranking an engine on stand), otherwise you crank the engines when off the stand.

This is why we are always careful to never disconnect the ground power from an airliner unless we have had a crew member give us the disconnect signal followed by a thumbs up, even when we can hear that the APU is running and even when I get that okay signal, I still tend to make sure I see them look at the overhead and check their electrical bus switch selection. 


Alan Bradbury

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