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Isaacelpiloto

Descending...

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Hello fellow 777 pilots,

 

It's not the first time it has happened to me but I star descending and suddenly I realised I have dhosen the wrong Star, wrong transition, etc. I start to waste time fixing route discontinuities. The aircraft starts to drift off its descent path, and I try everything (VNAV, FLCH) but it does not want to descend. So I end up arriving at the localizer at FL320 and ruining my flight. :(

 

 

 

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First, you should pay attention to program FMC correctly next time. Use charts and plan mode on nav display to confirm your route is correct. Pay attention on vertical profile, and crosscheck any constraints between chart and FMC. Connect eventual discontinuities and get rid off duplicate waypoints.

 

If you really need to change star/transition/runway when you are already on star, select FLCH/Vertical speed and HDG modes first. FLCH logic tries to follow speed first, and then profile, so if you are too fast FLCH will not start descend immediately until it bleeds energy, or until you select higher speed on MCP window.

At that point, if workload permits, you can reprogram FMC and couple it with autopilot again. 

 

If you arrive too high you should consider holding pattern to be able to descend.

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When you are faced with a complex operation that diverts your attention away from flying the aircraft, consider slowing the simulator rate to 1/2 or even 1/4. Although some simpilots or online facilities may frown on this, I would remind them that there are at least two pilots in the real-world cockpit. (In a long-range aircraft like the 777, there are often one or two relief pilots occupying the supernumerary cockpit positions.) One pilot can focus on flying the aircraft, while the other(s) deal with the distraction. Since you are expected to do the work of two real-world pilots by yourself, it is fair to slow the simulator rate to 1/2.

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You guys are giving him information overload. If he can't even make the plane descend, then it's pretty clear he doesn't understand how the aircraft works.

Read the introduction guide, then do the tutorial.

Best advice you can get right now.

 

If you still have questions after all that, I'm sure all the extra info would make more sense.

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You guys are giving him information overload. If he can't even make the plane descend, then it's pretty clear he doesn't understand how the aircraft works.

Read the introduction guide, then do the tutorial.

Best advice you can get right now.

 

If you still have questions after all that, I'm sure all the extra info would make more sense.

Exactly!

 

The only other thing that I just thought of is that he has manual throttles overriding the auto throttle. How else do you end up in FL320 at your destination even in FLCH?

 

So, to Isaaceiloto:

 

Do you have a throttle quadrant?

Of no...then forget everything below and do the tutorial flight.

 

If yes, read the intro guide instructions on how to setup your throttles!

 

Here is why:

FLCH is a mode that will reduce thrust with the auto throttles and then the autopilot puts the nose down to keep the speed that is set in the speed window.

However, if you have a throttle quadrant, then you must make It is setup correctly in the PMDG settings (in the CDU....see intro guide!) or otherwise your manual throttles will override the autothrottle. In that case thrust will reduce to idle at first, but it will not stay there unless you put your thrust levers in idle also!

 

So read the guide or disconnected your throttles for now and then see if FLCH and Vnav work better then.

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Thanks everyone fr the help really appreciate it.

No, I haven't tried the tutorial flight, so I will do so. Just to note, this doesn't happen to me every time, normally everything works fine.

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The best thing to do is select the most appropriate STAR before you takeoff, for which you will need an airport chart (usually easy to find online with google). The runway and transition will depend on local weather so may need to change. I usually don't enter them until later in the route, when I check current destination weather and guess the likely landing runway. Changing or entering runway and transition in the 777 FMC isn't that difficult and FLCH should keep the plane descending nicely while you update the FMC. Also don't feel you need to clear all the discos. Some are meant to be there. In most cases it's obvious from the ND map that you connect the end of one route segment to the beginning of the next, but others are meant to remain to allow for ATC vectors, which you would use HDG mode to steer with. You can use PLAN mode to step ahead along the route to see the arrival on the ND.

 

If you are using FSX ATC then it's largely a waste of time programming a full STAR/transition/runway apart, just select the STAR to give you a TOD prediction and initial descent path. Once FSX starts vectoring you you should leave VNAV mode as that will often give you descent path problems once you are off the planned LNAV track. Then enter the arrival runway and procedure in the FMC to tune the ILS once ATC assigns it to you.

 

As well as following the tutorial flight it would be a good idea to get familiar with how the various AP modes work in climb, cruise and descent. FLCH is really easy to use for descent, and as long as you set an altitude several thousand feet below your current level, maybe as low as 2000 feet above the destination field elevation, and choose a high enough descent speed (around 280 knots) you should have no difficulty in staying on or below the descent path while you reprogramme the arrival.

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The best thing to do is select the most appropriate STAR before you takeoff, for which you will need an airport chart (usually easy to find online with google). The runway and transition will depend on local weather so may need to change. I usually don't enter them until later in the route, when I check current destination weather and guess the likely landing runway.

 

Just keep in mind that outside of US most STARs are rwy specific. :smile:

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g_precentralis, on 08 Dec 2013 - 3:48 PM, said:

Just keep in mind that outside of US most STARs are rwy specific. :smile:

I don't think you can generalise like that. In Europe for example it varies by country and even airport. You can even see both at the same airport. That's why I said refer to the charts.

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If you want to descent with FLCH, make sure your MCP altitude is set to an altitude below(!) your actual altitude when selecting FLCH. Otherwise the plane doesn't know if you want to descent or climb. ;-)

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