Will i enter the first cruise alt in the FMC first?

Can you understand no?

 

 

But still can't figure out why i get a VNAV DISCONNECT?

It is normal.

Thanks so much for the help. Yeh FL250 sounds more like a REST. But still can't figure out why i get a VNAV DISCONNECT?

 

What about a STEP CLIMB in my FP ? Will i enter the first cruise alt in the FMC first?

 

Not sure about the disconnect, but it could just be related to your work flow.

 

Don't over automate. If you feel like adding the restriction in, set FL390 in as the cruise alt, and add the FL250 onto the legs page. Honestly, though, I'd just set it on the MCP. It's a common simism to try and get the FMC to do everything. It's really not necessary.

 

 

What about a STEP CLIMB in my FP ?

FL250 to FL390 is not a step climb. Control it using the MCP.

 

 

There is no problem with step climbs. Enter your final altitude on the INIT page as your cruise altitude. Control intermediate altitudes levels by using your altitude window and ALT INTV. Don't make any entries in the FMC for altitude changes. Put 390 in the FMC and leave it alone.

 

I'm not sure this is correct, but the topic is an ATC altitude restriction before reaching TOC and I don't mean to go off topic but...

 

I am flying UA1232 KLAX-PHNL in a B738 ETOPS-180.  Initial cruise is FL340 and final per PFPX is FL380 with two step climbs.  I notice that if I use FL380 as cruise in the FMC then entering STEP values on the CRZ page indicates a penalty rather than a savings.  Also I reviewed both FCOM and FCTM and I think that the correct method is to enter initial cruise in the FMC, enter the next step as STEP value on CRZ page and it indicates a savings amount and the step climb point (I've set my pressure controller to FL380). On reaching the step climb point, reset the FMC cruise value to FL360 and it gives the RESET MCP ALT message. Reset the MCP and press ALT INTV and a new TOC point is displayed on the ND and all performs as expected. No VNAV disconnect. After established at FL360 I set the STEP value to FL380 and it indicates the distance to step climb point and a savings value.

 

None of this has anything to do with original topic, sorry.

Not sure about the disconnect, but it could just be related to your work flow.

 

Could you possibly maybe try doing what i've done and see if you get a disconnect?

 

Don't over automate. If you feel like adding the restriction in, set FL390 in as the cruise alt, and add the FL250 onto the legs page. Honestly, though, I'd just set it on the MCP. It's a common simism to try and get the FMC to do everything. It's really not necessary.

 

Or you can just enter it into the CRZ page hit ECON and see where your TOC lands and try get it to match your final cruise waypoint.

Driver170, on 22 Dec 2014 - 7:49 PM, said:

 

What about a STEP CLIMB in my FP ?

FL250 to FL390 is not a step climb. Control it using the MCP.

 

Will do for future flights

 

 

Could you possibly maybe try doing what i've done and see if you get a disconnect?

 

Sure. I'll try and fit it in tonight. What's the route / restriction / etc.

 

 

 

Or you can just enter it into the CRZ page hit ECON and see where your TOC lands and try get it to match your final cruise waypoint.

 

Again, I'd stress that this is over-automating, and might be causing your issue.

Sure. I'll try and fit it in tonight. What's the route / restriction / etc.

 

Thanks kyle. None, thats the thing! If you just enter a first cruising alt of your choice and your final one at a higher alt like FL390. But don't got straight to FL390 just enter FL340 or anything lower in the MCP ALT and hit ALT INV.

But don't got straight to FL390 just enter FL340 or anything lower in the MCP ALT and hit ALT INV.

KIAD-KTPA Cruise attitude FL 380. Route - CAPITAL8 HAFNR GVE J75 TAY DADES4. 380 entered in FMC. Dialed 26000 in altitude window on MCP. At FL260 the climb stops. VNAV stays connected and VNAV SPD changes to VNAV ALT on FMA. Fly at FL260 for 50 miles. Change altitude to 38000 in MCP altitude window, press ALT INTV, plane starts the climb to FL380. Thrust is N1, VNAV ALT changes to VNAV SPD on FMA. Plane levels off at FL380. VNAV SPD changes to VNAV PTH and N1 changes FMC SPD on the FMA. VNAV remains connected the whole time of the flight. I was wrong, it does not disconnect at FL260.

KIAD-KTPA Cruise attitude FL 380. Route - CAPITAL8 HAFNR GVE J75 TAY DADES4. 380 entered in FMC. Dialed 26000 in altitude window on MCP. At FL260 the climb stops. VNAV stays connected and VNAV SPD changes to VNAV ALT on FMA. Fly at FL260 for 50 miles. Change altitude to 38000 in MCP altitude window, press ALT INTV, plane starts the climb to FL380. Thrust is N1, VNAV ALT changes to VNAV SPD on FMA. Plane levels off at FL380. VNAV SPD changes to VNAV PTH and N1 changes FMC SPD on the FMA. VNAV remains connected the whole time of the flight. I was wrong, it does not disconnect at FL260.

 

Yes that works for me too but you have missed the procedure that i have explained.

 

You need to set the FMC to FL260 level off and then put FL380 in the FMC and put a lower alt in the MCP ALT and try it ALT INV ....

Yes that works for me too but you have missed the procedure that i have explained.

 

You need to set the FMC to FL260 level off and then put FL380 in the FMC and put a lower alt in the MCP ALT and try it ALT INV ....

I am not going to use that procedure because it is incorrect See if you can get help on pprune. So long.

Incorrect? Not sure about that, all down to SOPs

 

http://www.airliners.net/aviation-forums/tech_ops/read.main/287623/

 

 

I reviewed both FCOM and FCTM and I think that the correct method is to enter initial cruise in the FMC, enter the next step as STEP value on CRZ page and it indicates a savings amount and the step climb point (I've set my pressure controller to FL380).

Dan, I agree that if your are doing step climbs the initial cruise altitude would be entered on the INIT REF page and the climb to the next altitude would be controlled by the CRZ Page in conjunction with the altitude window and the ALT INTV button. But to go from FL260 to FL390 is not a step climb. It's just a climb from an ATC restriction to the cruise altitude and the final altitude should be entered in FMC on the INIT page and the climb from the restriction to final altitude should be done by using the MCP not the FMC.

But if you set everything to the final alt and if you can't make that alt you will get a off schedule descend warning light.

Its not about getting help, its to see if anyone else gets this problem as it may be a bug. Its not going to take more than 5 mins.

 

I'm not saying its a bug but i'm only asking if anyone has the same problem

Why wouldn't you be able to make that altitude if you'd set it as the cruise altitiude? 

Change of winds or a diversion i don't know. Nothing is perfect.