Alerter above vnav alt
I notice that absolutely everytime I use VNAV I get a message saying 'Alerter above vnav alt'. It this some sort of error or warning message or is it simply a notification...? That yellow MSG in the top right corner really blinks as if something terrible is going on and you really need to read that message NOW! 
This happens also during a descent and that blinking MSG can become a bit annoying... I wonder if this happens this much in the real plane too.
Comments
VNAV is not used much in the Q400 in reality. "alerter above vnav alt" is a standard notification that the autopilot settings will cause level off before the target altitude in the FMS (assuming you have ALT SEL selected)
ckyliu - Proud supporter of http://www.ViaIntercity.com, over 950+ J41 & Q400 flights and 200+ for A320
Hm, well, I get that message without using alt sel and at the START of descent, so as soon as VNAV is engaged, so not when nearing a level off point. So that seems a bit odd...
But anyway, if it's not used that often in real life... I suppose most pilots descend using VS? Why isn't it used that often? Not precise enough? It seems to work flawlessly in the Majestic Q400. I do suppose VNAV is mainly used for RNAV approaches then?
Jvan, two things:
I would guess that the altitude alerter is a CRM thing. It is vitally important that the crew understand the airplane's assigned altitude, and SOP would dictate that the assigned altitude always be set in the alerter, no matter what method the aircraft is using to get there. If I remember correctly, just about all modern jets are set up so that the altitude in the FMS and the altitude in the alerter must agree.
I am in the US. Here, VNAV is used extensively now for SIDS and STARS, especially for jets. But... the Q400 isn't a jet, so across the US system the Q often gets treated just like a Twin Cessna, segregated into a lower, slower route structure that doesn't make much use of FMS/RNAV/RNP procedures.
I assumed that majority of descends are done in IAS mode...
And I assumed climb was done in IAS mode and descend in VS mode. That’s also how the real life Q400 pilot does it in the Airline2sim courses. Seems more logical somehow too.
Thats correct. For climbs, you would only use the GA, IAS and Pitch modes (Pitch depending on company SOP). Climbing on V/S is a strict no-no.
For descents however, you would always use manual V/S or very rarely VNAV. Another reason why you wouldn't use VNAV often is that it would give you inaccurate rates if ATC gives you a heading and you would fly that one in LNAV HDG mode. If you use the normal HDG mode, you would have to go V/S anyways. The VNAV also isnt capable of using wind data properly, giving you unreasonable rates for different legs. Apart from all that, the VNAV autoflight can be quite 'harsh', giving you very high descent rates if you happen to be above the profile.
So, for descent, pilots usually do set up the VNAV properly, but never actually engage the VNAV mode. It still serves as orientation, apart from that you can use the VTO or just the general rule of thumb. Also, you would usually aim for a -2000 fpm descent initially, which varies a bit depending on the aircrafts weight.
Great information, lgl3592, thanks! I already made a habit of setting the TOD on the VNAV page but descending with VS. I then keep an eye on VNAV to see if I am more or less descending well or not.
There still is something odd going on with VNAV... Just did a flight during which I did set VNAV on the left FMS but didn't use it at all. However, at one moment the right FMS showed the message: Alerter above vnav alt...!? And after landing it said: VNAV disconnected! While I didn't even set it on the right FMS!
Seems those messages sometimes show up at random...?
I can't tell whether or not those messages appear in real life as often as they do in the sim, but a quick "MSG" and "BACK" on the FMS will get rid of it.
Tapping MSG twice is even quicker.
+1 Excellent info. Thank you!
Haha, VNAV all the time, V/S during vectors... So there is no best way to get things done.
I get the Alerter above message even when I set a lower altitude before I get to the VNAV intercept path (which I of course alwasy do). So I am certainly not stuck at a certain level. No matter what I do, even when the plane follows the VNAV path perfectly, I do get that Alerter message. Yesterday I even got it once again on the right FMS while I hadn't even touched any VNAV setting.