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dromeascr

Step climbs and RVSM definition

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Hello,

 

I have 3 questions about step climbs, and I couldn't find an answer elsewhere, I guess you have the knowledge and experience I lack to help me with these.

So:

 

I was flying a 777F from NTAA to PHNL. When I was on the ground, I requested the PERF INIT page and I got FL320 as my CRZ ALT. I checked the LEGS page and I noticed that I'm climbing at FL340, not in a particular waypoint. Checking the PROG page, it was ~1320NM to step climb. Before reaching that point, I could clearly see the S/C point on the ND. I set the MCP alt to 34000 and the pitch mode was VNAV PTH. At about 20NM prior to that point, the S/C on ND disappeared, and in the PROG page the distance to step climb had the value "NOW". But nothing went on. It kept flying at FL320, I pressed the MCP alt knob but still nothing.

 

And my questions are- how to properly perform a Step climb, what is the "Step size" thing (in the VNAV 2/3 and PERF INIT pages), how it affects step climbs and what's the RVSM (Reduced Vertical Seperation Minimum, it's the default step climb value).

 

 

I tried to keep it as short as possible, I'm looking forward hearing from you guys.

Thanks in advance.    

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Hi,

 

1) Step climb:

To perform a step climb with the T7, you have to set the new altitude on the MCP, wait for the indication "Now" and then press the Alt intervene button on the MCP. The AP will then switch to VNAV SPD and THR REF and climb to the new altitude.

 

2) Step size: 

The box step size allows you enter the size of the steps you want to be calculated by the FMC. If set 1000ft, the FMC will computes the step climb every 1000ft. So If you start at FL320, the further S/C will be FL330, FL340, and so on.

For 2000ft, you will get FL320, FL340...

The default values are:

_ 0 : no step climb

_ RVSM: steps every 2000ft

_ ICAO: steps every  4000ft

_ Manual entry (1000...): steps computed on the value entered.

 

3) RVSM: The steps will be calculated every 2000ft as the levels for one way on a airway are separated by 2000ft (so to keep minimum 1000ft vertical separation between aircrafts on opposite course on the same airway).

General rules for the RVSM is even levels on 180-359°, odd on 000-179°, but there are numerous exceptions. In Europe, some countries like France, Italy and Spain adopted a North / South RVSM (Even to the North, odd to the South). In Asia, some countries like China and Mongolia have a RVSM based on metric FL.

 

RVSM is now implementated almost in the whole world if I'm correct (needs to confirm there as I can't find an actual chart of the implementation, mine is dated 2011), between FL290 and FL410. However, out of these levels and in some places remain other kind of separations:

Over FL410, the minimum separation is 2000ft, hence steps are 4000ft on a same course.

In non-RVSM airspaces (CVSM, if some remaining), all the flight levels are odd and separated by 2000ft on opposite direction (so 4000ft on a same direction).

 

On particular areas like the North Atlantic Ocean region, FL are allocated to the NAT tracks every 1000ft but you may not be allowed to perform step climb as the separation there is based on waypoint reporting with no radar coverage.

(It may be different now with in the implementation of the ADS-C and CPDLC on the tracks).

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OH, okay, step climbs can't be done automatically with VNAV PTH just by setting the new mcp alt as I thought. As for RVSM, thanks for your explanation, it really helped me sort things out. Since I was cruising at FL320, "2000" and "RVSM" are basically treated the same way for the step climb's calculation right?

 

And by the way, the difference between VNAV SPD and FLCH is the fact that it changes to VNAV ALT or VNAV PTH once it reaches MCP alt insteads of ALT hold right? 

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OH, okay, step climbs can't be done automatically with VNAV PTH just by setting the new mcp alt as I thought. As for RVSM, thanks for your explanation, it really helped me sort things out. Since I was cruising at FL320, "2000" and "RVSM" are basically treated the same way for the step climb's calculation right?

 

The MD11 used to step climb on her own when you set a higher altitude on the MCP but not the T7.

As far as I know and I have observed in the sim, yes RVSM and 2000ft gives the same calculations. A real T7 pilot would confirm though.

 

 

 


And by the way, the difference between VNAV SPD and FLCH is the fact that it changes to VNAV ALT or VNAV PTH once it reaches MCP alt insteads of ALT hold right? 

 

Basically, the mean difference between VNAV SPD and FLCH is that FLCH is blind mode. It makes you climb or descent to the altitude set on the MCP without taking care of the FMC VNAV profile. It means that it will not comply with any altitude or speed restriction.

On the contrary, VNAV SPD will provide protection for the speed and altitude restrictions along your way.

Let's say you are at FL320, set 10000 on the MCP. On your route, the next waypoint 30nm away has a restriction of min FL280.

If you press the FLCH, then the AP will brings you to 10000ft on a straight idle descent and will cross the next waypoint at whatever altitude that descent sets you may it be lower than FL280.

VNAV will start an idle descent and then stop at FL280 if you reach that level before the waypoint, switching to VNAV PTH and SPD at some point at or before that level.

Then with no further intervention from your part, it will resume the descent once passed the waypoint with altitude restriction.

 

Regarding speed, the same applies for example for the 10000/250 restriction. If you descent with FLCH to 8000ft with 280 set in the speed box of the MCP, it will keep that speed through the 10000ft.

If you use VNAV, then, the FMS will slow you down to 240kt before reaching 10000ft by reducing the rate of descent and then continue to 8000ft.

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Once you get comfortable with performing the step climb maneuver in the B777, there is a PMDG option to do this for you automatically. This feature is not in the real aircraft, of course.  See the complete options in the Introduction manual.

 

Also, recommend you fly the tutorial that came with the product. There is a lot of useful information there.

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The MD11 used to step climb on her own when you set a higher altitude on the MCP but not the T7.

As far as I know and I have observed in the sim, yes RVSM and 2000ft gives the same calculations. A real T7 pilot would confirm though.

 

 

 

 

Basically, the mean difference between VNAV SPD and FLCH is that FLCH is blind mode. It makes you climb or descent to the altitude set on the MCP without taking care of the FMC VNAV profile. It means that it will not comply with any altitude or speed restriction.

On the contrary, VNAV SPD will provide protection for the speed and altitude restrictions along your way.

Let's say you are at FL320, set 10000 on the MCP. On your route, the next waypoint 30nm away has a restriction of min FL280.

If you press the FLCH, then the AP will brings you to 10000ft on a straight idle descent and will cross the next waypoint at whatever altitude that descent sets you may it be lower than FL280.

VNAV will start an idle descent and then stop at FL280 if you reach that level before the waypoint, switching to VNAV PTH and SPD at some point at or before that level.

Then with no further intervention from your part, it will resume the descent once passed the waypoint with altitude restriction.

 

Regarding speed, the same applies for example for the 10000/250 restriction. If you descent with FLCH to 8000ft with 280 set in the speed box of the MCP, it will keep that speed through the 10000ft.

If you use VNAV, then, the FMS will slow you down to 240kt before reaching 10000ft by reducing the rate of descent and then continue to 8000ft.

 

Thanks again, a lot of useful information I was missing. I hope you are eager to answer one more question. 

When a leg in the LEGS page is linked with an altitude contraint (like 3000A or something like that), how can I see what altitude has the FMC calculated I will be by that leg, so I can perfectly match it's calculated glidepath, even though I have disengaged the VNAV ? Below 10000 I usually disengage the VNAV and descend with V/S, so isn't there a way to find that out? For a normal leg, the altitude and the speed are displayed next to it in the LEGS page. But what about those with altitude contraints? 

 

The fact that you are not a real life pilot, really surprised me. 

 

 

Once you get comfortable with performing the step climb maneuver in the B777, there is a PMDG option to do this for you automatically. This feature is not in the real aircraft, of course.  See the complete options in the Introduction manual.

 

Also, recommend you fly the tutorial that came with the product. There is a lot of useful information there.

 

I haven't flown the tutorial (You mean the first tutorial, Male Int'l to Dubai I guess) but I have read the whole pdf. As for the second tutorial (Washington to Munich if I remember correctly), I haven't flown it either, but I have read most of it. 

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Thanks again, a lot of useful information I was missing. I hope you are eager to answer one more question. 
When a leg in the LEGS page is linked with an altitude contraint (like 3000A or something like that), how can I see what altitude has the FMC calculated I will be by that leg, so I can perfectly match it's calculated glidepath, even though I have disengaged the VNAV ? Below 10000 I usually disengage the VNAV and descend with V/S, so isn't there a way to find that out? For a normal leg, the altitude and the speed are displayed next to it in the LEGS page. But what about those with altitude contraints? 
 

 

As far I know, there is no way to know what is the calculated altitude  behind a speed restriction. And deleting the altitude restriction  to find it out may not be the best way as the VNAV profile would be modified when you delete it.

 

However, I don't think it is really useful to know that. If you want to descent using another mode that VNAV, then you have two choices.

_ Use FLCH and set the next altitude restriction in the bow on the MCP, then update the altitude box after passing the restriction

_ Use V/S, set the altitude restriction on the MCP and adjust the rate of descent so that the green arc matches the waypoint with the altitude restriction on the ND.

 

As long as you remain above the MSA/MEA and above/below the next altitude restriction, then you are fine.

 

 

 


The fact that you are not a real life pilot, really surprised me. 

 

I'm flattered, thanks! However I'm far from having the knwoledge of a real pilot. I may read all the books, manuals and tutorials I can find, I still miss the concrete experience of being at the commands in the cockpit!

There are some things you can learn in theory and some others you unfortunately will never know unless you fly the real birds.

I'm making my way to the PPL though! I will never fly big jets, but at least I have started flying small prop.

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I haven't flown the tutorial (You mean the first tutorial, Male Int'l to Dubai I guess) but I have read the whole pdf. As for the second tutorial (Washington to Munich if I remember correctly), I haven't flown it either, but I have read most of it.

 

You should fly the tutorials.... I could read the best books out there on how to land an airplane but until I got in one and started doing it I didn't know peaches from fluff.

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Thanks for all your help, I really appreciate it.

 

Best wishes, I hope you will enter a cockpit's door and use your skills and knowledge one day.  

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