Embraer E190 FLCH logic

[FLX/MCT]

Hey fellow PPRuNers,

I am looking for some deeper explanation of SPDe logic when climbing/descending in FLCH mode on the E190.

According AOM

For small altitude changes the AT commands only the necessary thrust in order to maintain a comfortable predetermined schedule based on vertical speed.

Does anybody know specific numbers or even some references when the "small altitude change" logic will engage and whether FLCH aims for a specific V/S in this case? (I heard on Boeing 777 it is based on time to reach the selected level.., maybe it is similar on the Embraer)
I have already checked the AOM and also some Honeywell guides but so far without success.

Any answer is appreciated

[FE Hoppy]

For small Flight Level Change climbs and descents, the AT implements a proportionality scheme that provides thrust as appropriate to attain a programmed rate of climb/descent.
The programmed rate of climb/descent is proportional to the magnitude of the selected altitude change. For the first 1000 ft of flight level change the climb/descent rate is 1 to1 (i.e. if the change is 1000 ft the AT would aim to achieve 1000 ft/min of climb/descent rate).
For flight level change beyond 1000 ft the programmed rate becomes 1 to 2 (i.e. if the change is 3000 ft the AT would aim to achieve 2000 ft/min of climb/descent rate). Full thrust climbs and full idle descents are achieved when the target climb/descent rate increases beyond the capability of the aircraft for the active upper and lower N1 rating.
This scheme assures that passenger comfort is maintained throughout the small altitude change maneuvers where maximum climb and idle thrust is undesirable.

Don't ask me how I know ;-)

[FLX/MCT]

You really nailed it, thanks!

[Micky]

In my experience this logic doesn't work as well as it should. Especially the 1000' climbs really don't work most if the times I find the V/S increasing to a rate which is not in compliance with out OM-B limits, so for Idle Descents or climbs its great but for small climbs e.g. 1000-3000' V/S of FPA work best for me.

[AtomKraft]

I think it works really well.
It's nice how it changes from "speed on the throttle" to "speed on the elevator" too.

It's clever stuff, the AT sys on these e-jets.

[Capn Bloggs]

Originally Posted by Micky

Especially the 1000' climbs really don't work most if the times I find the V/S increasing to a rate which is not in compliance with out OM-B limits

Surely you're joking? By the sounds of it, the system works well. Why on earth would you have SOPs that discourage it?

[FE Hoppy]

Micky, If your OMB doesn't match the aircraft, that's not the aircrafts fault.

[Micky]

The programmed rate of climb/descent is proportional to the magnitude of the selected altitude change. For the first 1000 ft of flight level change the climb/descent rate is 1 to1 (i.e. if the change is 1000 ft the AT would aim to achieve 1000 ft/min of climb/descent rate)

This is the same what the instructurs at Jet Blue taught us, but in my experience the V/S rises to about 1200-1300 ft/min when using the FLCH mode for 1000' climb or descents. And this is higher then the 1000 ft/min Limit which is set down in our OM-B. This was introduced to stop TCAS RA issued due to excessive closer rates to cleared levels in the terminal area. Resulting in about 80% of all RA's experienced in my company.

I really like the Embraer is a great Aircraft and fun to fly. I just wanted to point out that the FLCH mode (for small Altitude changes) does work as well as it is written in the manuals. As I said before for idle descents or during climb out it works really well.

[The Baron]

The best vertical mode for normal climb is FLCH. For small changes I use FPA. VS is best suited to turboprops and other slow moving obstacles.

[ACMS]

Mmmmmmm

We use VS for climbs and descents ( if given altitude restrictions by ATC ) as required on the A330 with the understanding you normally don't at high flight levels due to performance thrust issues.

Especially required in RVSM and also to avoid nuisance TCAS RA's with level offs.

Also used a lot on the 744 and 777.

[Capn Bloggs]

As I said before for idle descents or during climb out it works really well.

So does my VNAV.