PMDG Boeing 737 AP wont engage?

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21

Did you add the correct position in the FMC to finish the alignment?

22

These are facts;

  • The IRS’ haven’t been aligned correctly
  • As per the real aircraft, if there is an issue with one or both IRS’ then the autopilot is not available

It really is that simple I’m afraid

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23

According to this vid i started the 737. You see at 1:10 how to activate Align and at 1:25 you see how i choose correct GPS position.

24

What Vid?
Once again, you did something wrong obviously.
Got back to the Airport and start all over and do not start the engines before you have an aligned IRS!!
It might be a small error, i.e. switching accidently the IRS Switches to ATT and back to NAV. This doesnt work, and you have to start all over from the off position.

25

Can i set the GPS position again as i did at gate and align?

26

I did all before 100% according to vid and not for the first time. But this error occours quite often. So is this vid wrong?

27

And why the Yaw Damper sometimes switch to off? Cause the maneuver was too strong? And why sometimes Master Caution “FLT CONT” appears? In the FMC there is no error to see according to hydraulic system for example.

28

It’s been a long time since I flew the 737 for real, but I seem to remember it is possible to get some element of IRS functionality back in flight after a fault. It’s a long and arduous checklist though.

I suspect what you’ve done is select align then move the aircraft before the process has finished. The align lights need to be extinguished for them to be correctly aligned. The process generally takes about 10 minutes.

The Yaw Damper switch has a solenoid and it won’t stay in position until the IRS alignment process has run for about 30 seconds.

1 Like
29

Well, i just looked roughly over it and there is one thing which can be the problem. He added the last known GPS Position for the IRS Align. Nice and for sure quite a good idea in real life, but in the sim you “move” the aircraft from one airport to another without flying it. So it might be possible, that you added a totally wrong position and the IRS didn’t align because of it.
Hint-> add the actual Airport on the left side and take this position.

And no, it occurs not quite often, i never saw this on my flights, just when i made a mistake at the beginning.

30

Do i have to init position before align? In the vid he first align and then init position. But it works in his vid.
And i move firstly when pushback and then turn on the engines. But long before pushback i init position and align. Yaw Damper also switch to off when making extreme hard maneuvers i just experienced.

31

I think it hast been added cause i also implement the flightplan via Simbrief as he explained in another vid and all in correct order.

32

Just try it. Step by step and if the IRS won’t align, step back, think and start all over. PMDG is not just a Vanilla Plane. It works, more or less, like the real one. So you have to learn how the plane works and what to do to get it work.
When i switch between Airbus and Boeing i just need 2 or 3 flights to get all subtleties again. Thats the reason why you have to do a rating for a specific aircraft type IRL.

33

No. The sequence (and I am massively simplifying this) should be;

  1. Battery on
  2. AC power on (either GPU or APU)
  3. IRS switches to ‘Align’
  4. Setup panel scan starting from the top left corner. As mentioned, the IRS alignment has to have actually started for the Yaw Damper switch solenoid to work. If you try and do this straight away the switch will just go back to the off position
  5. Once the panel scan(s) are complete you then move to the FMC setup. The first part of that is to go to the POS INIT page, select the GPS position into the scratchpad then bring it in to the current position boxes using the line select keys. You can enter the position at any point during the align process. If you haven’t done so by the time the IRS’ are happy the align lights will flash to alert you to the fact that you need to enter the position in to the FMC.

If you do it like that it will work 100% of the time.

2 Likes
34

What about Stdby Pwr? So far i did it right according to the vid. But then i wonder why i got the problems?

35

But the steps in vid above are correct, or did he something wrong? Cause i followed it very strictly.
And whats wrong with “FLT CONT”?

36

That’s a master caution because elements of your flight control system aren’t working because your IRS’ aren’t aligned.

You’re just gonna have to trust us here.

37

But isnt FLT CONT related with hydraulic or something like that?

38

Not only → FCOM is your friend :wink:
The correspnding part of the screenshot shows you, FLT CONT belongs to Speed Mach Trim Fail as well :grimacing:

IMG_0473
IMG_04731449×1459 153 KB

2 Likes
39

I been flying the 737 since launch and personally I think tutorial videos are not worth it,grab a Manual and a FCOM and do a test flight from airport A to airport B..

40

The IRS is the source of heading information for the autopilot, as well as pitch and roll information. The autopilot cannot work at all without the IRSs being fully aligned - it would have no idea what direction the aircraft is pointing or which direction is “up”

There are options in the FMS menus for how fast the IRS align. It real life, they can take 7 to 10 minutes to align after you enter the current GPS position. The aircraft must not be moved (pushback or taxi) until alignment is complete. That is probably what happened to you. If you don’t want to wait, you can select the option to have the IRSs align “instantly”.

1 Like