I've just found out in the FCOM that THR makes the autopilot adjust the thrust for a specific V/S. From what I've seen, FLCH always commands THR, but sometimes I get full reference thrust, and other times I get variable thrust for a specific V/S. Is there a way to activate THR REF while in FLCH? Conversely, is there a way to remain in THR, but climb at max N1? Finally, in what conditions does FLCH command full N1 climb/full idle descent, and in what conditions does it command a specific V/S? LVL Change works differently in NG, and I've been unsuccessful at finding this in the manuals, so I'd appreciate if someone can point me in the right direction.

Yes level change works (slightly) different than in NG.

The FlighLevel Change in the 777 mode is actually a smart mode :-)

 

And no you can not change that.

 

First of all, the 777 is a Vnav/Lnav mode airplane.

Meaning you would normally use those modes.

All other modes are perfectly fine modes as well ofcourse, but are used when Vnav and/or Lnav are not suiting your needs for the particular climb or descend.

(such as switching to VS mode if ATC instructed you to maintain 1000ft/min)

 

If you would just use Vnav for your climb you get full climb thrust all the time during climb.

Now here comes the FLCH smart bit.....

If ATC can only clear you for small climbs/descends at a time, lets say from 5000ft to 7000ft, then you realy dont want to use Vnav for that (with full CLB thrust).

 

Very uncomfortable for your pax to level off.....then up like a rocket......level off.....etc

 

Further more, to prevent constant TCAS Resolution Advisaries from happening a pilot should reduce his climb/descend rate to 1000 - 15000ft/min upon approaching his cleared FL, if other aircraft are around.

You do this by changing from Vnav to VS for the last bit (last 1000 - 2000ft) of the climb/descend.

(For further climb/descend you would engage Vnav again).

So if another aircraft is flying level at 8000ft (so 1000ft above the level you are going to) and you would climb with Vnav (and THR REF) you have to set 7000ft, then press the altitude selector, then as you see the planes VS increase and increase and you become aware of the traffic in 8000ft you have to engage VS to reduce the rate.

Probably too late with that and the other aircraft has already executed a TCAS RA :-(

 

Much more elegant to use Flight Level Change which will give you a nice smooth climb that will reach 7000ft in two minutes (that is its target). So the FLCH climb would result in about 1000ft/min in this example.

 

Like I said, FLCH has a target to reach the set altitude in two minutes and adjust thrust accordingly.

If the difference between current altitude and newly set altitude is large enough (large enough that you cant get to this new level in two minutes) than it wil be at full thrust (or idle in descend) and it will stay there.

 

Normally ATC will try to give you uninterrupted climbs/descends, or at least climbs/descends over several thousand feet and you would use Vnav for this.

But if traffic does not permit this then FLCH is quite nice for this.

Yes level change works (slightly) different than in NG.

The FlighLevel Change in the 777 mode is actually a smart mode :-)

 

And no you can not change that.

 

First of all, the 777 is a Vnav/Lnav mode airplane.

Meaning you would normally use those modes.

All other modes are perfectly fine modes as well ofcourse, but are used when Vnav and/or Lnav are not suiting your needs for the particular climb or descend.

(such as switching to VS mode if ATC instructed you to maintain 1000ft/min)

 

If you would just use Vnav for your climb you get full climb thrust all the time during climb.

Now here comes the FLCH smart bit.....

If ATC can only clear you for small climbs/descends at a time, lets say from 5000ft to 7000ft, then you realy dont want to use Vnav for that (with full CLB thrust).

 

Very uncomfortable for your pax to level off.....then up like a rocket......level off.....etc

 

Further more, to prevent constant TCAS Resolution Advisaries from happening a pilot should reduce his climb/descend rate to 1000 - 15000ft/min upon approaching his cleared FL, if other aircraft are around.

You do this by changing from Vnav to VS for the last bit (last 1000 - 2000ft) of the climb/descend.

(For further climb/descend you would engage Vnav again).

So if another aircraft is flying level at 8000ft (so 1000ft above the level you are going to) and you would climb with Vnav (and THR REF) you have to set 7000ft, then press the altitude selector, then as you see the planes VS increase and increase and you become aware of the traffic in 8000ft you have to engage VS to reduce the rate.

Probably too late with that and the other aircraft has already executed a TCAS RA :-(

 

Much more elegant to use Flight Level Change which will give you a nice smooth climb that will reach 7000ft in two minutes (that is its target). So the FLCH climb would result in about 1000ft/min in this example.

 

Like I said, FLCH has a target to reach the set altitude in two minutes and adjust thrust accordingly.

If the difference between current altitude and newly set altitude is large enough (large enough that you cant get to this new level in two minutes) than it wil be at full thrust (or idle in descend) and it will stay there.

 

Normally ATC will try to give you uninterrupted climbs/descends, or at least climbs/descends over several thousand feet and you would use Vnav for this.

But if traffic does not permit this then FLCH is quite nice for this.

Got it, thanks for the helpful information. Quick question, though. I understand the benefit of using reduced thrust when climbing, say 2000 ft. But what if I want to descend around 2000 feet, and I want to do it as quickly as possible, is the only solution to descend using V/S and/or disconnect the A/T?

Got it, thanks for the helpful information. Quick question, though. I understand the benefit of using reduced thrust when climbing, say 2000 ft. But what if I want to descend around 2000 feet, and I want to do it as quickly as possible, is the only solution to descend using V/S and/or disconnect the A/T?

Welcome :-)

 

in descend the AT will first lowly move to its target thrust setting (for the 2 minutes target) and then switch from THR to HOLD mode.

In HOLD mode, in the real aircraft, you can take the thrust levers and manually close them to idle and they will stay there.

 

In the PMDG777 you can change in the CDU if you want to be able to that as well.

You can set your Throttle Quadrant (if you have one) to override the AT never or when in HOLD mode or Always I think.

You can also try what the F1 key does once the AT is in HOLD mode.

 

Otherwise yes, VS mode will make you dive down real fast if you want :-)

Welcome :-)

 

in descend the AT will first lowly move to its target thrust setting (for the 2 minutes target) and then switch from THR to HOLD mode.

In HOLD mode, in the real aircraft, you can take the thrust levers and manually close them to idle and they will stay there.

 

In the PMDG777 you can change in the CDU if you want to be able to that as well.

You can set your Throttle Quadrant (if you have one) to override the AT never or when in HOLD mode or Always I think.

You can also try what the F1 key does once the AT is in HOLD mode.

 

Otherwise yes, VS mode will make you dive down real fast if you want :-)

Alright, I get you. Well, thanks for the help. When I first saw this behavior, I thought I was going crazy and was setting up something wrong haha.

I know what you mean, with any simulation you are always thinking, is this normal or is something wrong :-)

FLCH is a "modulated" mode in the 777 - Rob explained it perfectly.

Thanks for the complement :-)