SouthportGuy

FMC Msg: Unable CRZ ALT

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After weeks of trial and error I was able to successfully plan and load a route into FMC.

 

When I entered my cruise alt of FL380 it told me my max cruise for this route was FL353. OK. So I set it for FL353. Take-off, ascent goes fine, waypoints crossed etc. Now, my problem occurred when I was almost reaching T/D and I was waiting for the FMC to tell me RESET MCP ALTITUDE but this message never came. Instead once I reached T/D I got UNABLE CRZ ALT instead and thus my altitude never started dropping.

 

What did I miss?

 

Tried Google search for this problem but didn't find an answer for my exact situation.

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Hi,

 

First reading your post some clues make me believe that you are quite new to the sim (at least to the T7) like selecting FL353 (FL are always rounded to zero so it would be FL350 in this case, but also flying at the max FL where in most cases you would be rather flying at the optimum FL +/-1000ft to comply with airways parity and RVSM levels.

I would strongly suggest that you fly the tutorial that comes with it.

Then it seems to me that for whatever reason, the FMC never went to cruise mode but remained in climb mode and therefore won't go to descent mode either. What is it displayed on top of the VNAV page when you press once on the VNAV button of the CDU and does it bring you to page 1/3 or 2/3?

Also what is the altitude you have selected on the MCP compared to the actual aircraft altitude and to the one predicted or computed by the FMC?

Last, what modes are displayed on the FMA?

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Tried Google search for this problem but didn't find an answer for my exact situation.

 

The best place to start is the tutorial that you received with the product.  In fact, I would say in your case it is mandatory and don't get discouraged if everything doesn't become clear the first time. There is a lot to learn. Have fun.

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Hi,

I would strongly suggest that you fly the tutorial that comes with it.

I've been simming for a couple of years now. I just chose to follow the max attitude indicated by the fmc. I flew the tutorial with total success. Since then I've had no luck successfully planning my own route and flying it all the while having the tutorial manual open. Trust me, I'm following every step in the manual tutorial. The variable is the route I've entered.

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Hi,

 

May I ask you a couple of questions?

 

 

 


Since then I've had no luck successfully planning my own route and flying it all the while having the tutorial manual open

 

Are you referring to issue with the unable crz alt and "reset MCP alt" not showing? You said you did fly successful for once following the tutorial then not anymore after that?

 

 

 


The variable is the route I've entered.

 

The flying technique doesn't really depend on the route you enter in the FMC. It is a set of procedures to be followed per se. The route is just the path to go from point A to point B. 

What is preventing you from flying properly the aircraft related to the flight planning?

 

 

 


I've been simming for a couple of years now. I just chose to follow the max attitude indicated by the fmc.

 

May I ask you why such a decision? Sticking to the max altitude is neither realistic nor it is fuel efficient. If you want to stick to an altitude no matter what then you should stick to the optimum level.

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May I ask you why such a decision? Sticking to the max altitude is neither realistic nor it is fuel efficient. If you want to stick to an altitude no matter what then you should stick to the optimum level.

Because I've been flying the 747 for two years and I'm trying to learn to fly the 777. Flying the optimum level is good idea but not my concern at this point of my training as the tutorial does not explicitly require me to do that step. Using the tutorial and planning my own route is my goal today.

You said you did fly successful for once following the tutorial then not anymore after that?

No, I said I flew the tutorial with total success (using the destinations and routing required in the tutorial). Since then I've had no luck successfully planning my own route and flying it all the while having the tutorial manual open. I'm getting closer and making progress but I've run into a snag.

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There are so many factors to consider:

Takeoff weight

Fuel on board

Distance to be flown etc etc...

 

Unless there are specific operational or route-based restrictions (airway limitations and so on), you should aim to fly the highest operationally safe level possible for the route and weight of aircraft, taking into account the en route weather conditions at the altitude you aim to be. After a while, you tend to be able to guess the flight level for cruise for your route length and current aircraft takeoff weight. If you planned FL380, but the aircraft can only reach FL353, then you should enter FL340 (assuming your flight plan requires an even level for a westbound track). If your route is long, then you may opt to step climb to FL360 or FL380 if and when those levels become available as a result of the reduction in weight en route (thanks to fuel burn).

 

I am no expert in these matters, I just have around 1500-2000 or so logged hours on the NGX. If any of what I write you do not understand, then you may need to do a bit more reading in order to get the most out of the 777 simulation. The PMDG study sims do require some prior knowledge and perseverence, but the rewards are there.

 

Andrew

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While this point is irrelevant for flight simulation as far as simulator itself is concerned, airliners in real world operations almost never cruised at flight levels without a zero at the end, and even in metric airspace they cruised at a certain multiple of 300 meter. Random flight level assignment might be a thing in the future(There are researches showing how that would reduce possibility of a mid-air by turning most of them into airprox), but not now. Even then you just don't get to stay at your weight-adjusted maximum or optimum altitude and slowly climb as fuel weight goes down, even though that would be most efficient barring wind adjustment in case of optimum altitude.

 

About the question itself, make sure you didn't miss any steps and entries when adapting your own route to the tutorial, and the exact route you did fly would have been helpful posted here. UNABLE CRZ ALT would typically only appear during preflight when FMS judges your set cruise level incompatible with enroute restriction or climb performance - Like trying to file LHR-AMS at anything above around FL230(at-or-below crossing restriction at REDFA), or putting in just about anything in a local pattern with nothing but takeoff and landing runway in FMS, in my experience.

 

EDIT: P.S. You don't "trial and error" a Boeing 777. Much of your purchase price went to those documentation that came with the aircraft, make sure they are worth the money spent.

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I got UNABLE CRZ ALT
The only place this message is referenced is in FCOM2 page 11.60.7. It says "performance predicts a zero cruise time at the entered altitude." Quit trying to fly at max alt. and plan your flight for optimum alt. Your flights are screwed before they ever leave the ground.

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Quit trying to fly at max alt. and plan your flight for optimum alt. Your flights are screwed before they ever leave the ground.

As a newer 777 user I don't know how to determine what my optimum alt is. Perhaps a better way to answer is to not just say " Quit trying to fly at max alt. and plan your flight for optimum alt." and give me a more direct step on how to determine what that optimum alt should be. The FCOM2 page doesn't explain it (when searching for words "optimum", "cruise", and "altitude"). I've also been Googling trying to find the answer believe me.

 You don't "trial and error" a Boeing 777. Much of your purchase price went to those documentation that came with the aircraft, make sure they are worth the money spent.

You don't trial and error Boeing 777 in real life. You can absolutely trial and error a Boeing 777 in FSX. Which is exactly how I learned the 747.

 

Not everybody learns by textbook. This is a very frustrating comment that I keep seeing from others who think they are trying to help. I know people get upset when newbs ask what you think are questions easily answered if they were just wired the same way you are. Well, not everyone is wired nor learns the same way you do. I learn by reading manuals and working with other good-hearted people who don't get bent out of shape with playing an instructor role.

 

I honestly try to think of ways to not ask questions. I open the pdf's, I search the pdf's using the search feature, I search Youtube. I work to steer away from even having to come into a forum and ask a question which often inevitably results in some kind of "Well duh!" response.

 

If there is a better instructor friendly sub-forum in this site I'd be happy to move there in order to not bother the more experienced users here if that helps.

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As a newer 777 user I don't know how to determine what my optimum alt is. Perhaps a better way to answer is to not just say " Quit trying to fly at max alt. and plan your flight for optimum alt." and give me a more direct step on how to determine what that optimum alt should be. The FCOM2 page doesn't explain it (when searching for words "optimum", "cruise", and "altitude"). I've also been Googling trying to find the answer believe me.

 

Try the FMC. Press the  VNAV button. Go to the next page which should be ACT ECON CRZ 2/3.  Look on line 4 second from the left.  OPT is the optimum altitude. When selecting the altitude to fly at take into consideration post #2 first sentence.

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Not everybody learns by textbook. This is a very frustrating comment that I keep seeing from others who think they are trying to help. I know people get upset when newbs ask what you think are questions easily answered if they were just wired the same way you are. Well, not everyone is wired nor learns the same way you do. I learn by reading manuals and working with other good-hearted people who don't get bent out of shape with playing an instructor role.

 

I honestly try to think of ways to not ask questions. I open the pdf's, I search the pdf's using the search feature, I search Youtube. I work to steer away from even having to come into a forum and ask a question which often inevitably results in some kind of "Well duh!" response.

 

If there is a better instructor friendly sub-forum in this site I'd be happy to move there in order to not bother the more experienced users here if that helps.

 

Hi,

 

When I read Michael's and your answer I understand both of you. However, It think his comment was more intented to people who rush to the forum at the first little thing without opening the least document and believe me they are quite numerous in forums in general.

 

Have you ever read posts where people tell something like, I don't understand how to do that, or why it does that when I press this... And the next answer is, check the first page of the intro manual?

 

Sure the forum is a place to ask question and where a lot of people are quite happy to help and come to seek for help along with  looking at documents and trying to learn the maximum by themselves is a good thing.

Rush to the forum expecting from others to copy-paste what is already written tutorials/manuals just because they are too lazy to search by themselves and expect their whims to be served on a silver plate, heck no!

 

That's why, when someone ask how to fly the aircraft or ow to you use this or that equipment, we usually lead them toward the manuals and tutorials first not to bash them but to encourage them to learn by themselves and also sometimes to save some time.

 

To me, taking the time to read again and again the documents provided with the add-ons is also another way to show some respect and gratitude to people who took the time to write these documents (especially the tutorials that are not always written by employees who are paid for but sometimes by volunteers who are only willing to help others freely).

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Try the FMC. Press the  VNAV button. Go to the next page which should be ACT ECON CRZ 2/3.  Look on line 4 second from the left.  OPT is the optimum altitude. When selecting the altitude to fly at take into consideration post #2 first sentence.

That did the trick!  Was able to do the complete flight from gate to gate. Thanks for helping guys.

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My apologies if my comment troubled you... That was not my intention. Congrats on getting your question sorted out!

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On ‎1‎/‎23‎/‎2016 at 8:38 AM, pcubine said:

 

Try the FMC. Press the  VNAV button. Go to the next page which should be ACT ECON CRZ 2/3.  Look on line 4 second from the left.  OPT is the optimum altitude. When selecting the altitude to fly at take into consideration post #2 first sentence.

Is it valid for PMDG 747-8 FMC as well? I don't see ACT ECON CRZ 2/3 I am asking on this because I also got an "Unable Crz Alt" message. I resolved that by changing the route giving more distance between Departure and Arrival legs.

BnrCNQc.jpg
 

 

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4 hours ago, ph-cxz said:

vnav page. 

Got it, many thanks

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