LasseT

Cancel of decend mode

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Hello,

During the week I flew between Stockholm/Arlanda and down to Palma de Mallorca.

When we entered French air space and should go down 1000 feet, I probably did something wrong. NGX ended up in some form of "long decend".

When I looked at my legs page, I saw that at each point, a slowly falling height was all the way to the beginning of STAR. Even the speed was affected.

On the ND, the decend path had also showd up. 

I had to fly the plane on altitude and speed hold the rest of the flight but could use LNAV.

It is clear that I somehow ended up in decend Mode.

The question is, if there is some way to get out of this mode and Go back to VNAV / LNAV mode.

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Hi,

Just enter again you cruise level in the CRZ page of the CDU and the FMC will revert to cruise mode.

And by the way, forum rules require to put your full names in all your posts.

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Thanks for your reply. I tried to fill in FL on CRZ page but it did not work.

It seemed like something had hung up for decende mode remained on my ND

Unfortunately, I missed the rule for full name but it is fixed now :biggrin:

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Can you please describe how you initiated the 1000ft descent for your change of level what was displayed on the FMA before and after the change?

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Unfortunately, I do not remember in what order I did. Probably in the wrong order.

Yesterday I tested again like this:

1. Changed FL on CRZ page in FMC

2. Changed FL on overhead panel for cab pressure

3. Changed FL on MCP and pressed ALT INTV.

That way, it worked well.

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If I recall well (but I don't have the FCOM at hand and didn't fly the NGX for a long time), the FMC should change to descent mode when you set a lower altitude on the MCP and press the alt intv button only when at a certain distance of the calculated TOD (maybe 150nm).
Otherwise it should interprete it as a change of flight and just go to cruise descent mode until reaching the new flight level and revert automatically to cruise mode.

But I fly much more the 744 and the 777 which for sure work that way.

Do you remember at which distance from the calculated TOD you were when you initiated the descent to the lower flight level?

 

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When I look in my OFP, I decend to FL330 (from FL340) 635 nm before TOD. Should have risen to FL350 again 524 nm before TOD.

When I tested yesterday and succeeded I did in this order:

1. Changed FL on CRZ page in FMC

2. Changed FL on overhead panel for cab pressure

3. Changed FL on MCP and pressed ALT INTV

Another pilot I've got on my FB writes like this:

According to our SOP, it is:

1. Change FL on MCP and press ALL INTV

2. Change FL on CDU

3. Change FL on FLT ALT (cabinpressure)

The problem for me is actually how / if I can get out of decent mode if I happen to initiate it incorrectly.

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2 hours ago, LasseT said:

The problem for me is actually how / if I can get out of decent mode if I happen to initiate it incorrectly.

Just remember the ALT INTV technique.  When all else fails with your automation, simply turn it off.  Turn off both F/D and then turn back on.  Reset things to where you want them to be.  It's just part of the learning process, you won't do that very often.

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