Using ALTS in the Hawker

[Richard Sennett 2,499]

According to the RW manual, you initiate an altitude change by:

 

Thanks Bert but was hoping this tweak you have made will do this - have you tried it or I would assume you are using gtn and can not test it ?

 

2.3.  Select FLC mode and adjust the throttles for vertical speed

[Bert Pieke 7,584]

The way Carenado has implemented it, the autopilot starts a 500 fpm climb or descent the moment you turn the altitude knob, when you are flying in ALT hold mode.

 

In my GTN mod, I changed this to 1000 fpm to make it more useful.  (500 fpm seems too little for a business jet).

 

The above mod changes it to 0 fpm which I believe, is the way the real aircraft behaves.

 

Turning the knob should not initiate a climb or descent, all by itself.

[Richard Sennett 2,499]

The way Carenado has implemented it, the autopilot starts a 500 fpm climb or descent the moment you turn the altitude knob, when you are flying in ALT hold mode.

 

In my GTN mod, I changed this to 1000 fpm to make it more useful.  (500 fpm seems too little for a business jet).

 

The above mod changes it to 0 fpm which I believe, is the way the real aircraft behaves.

 

Turning the knob should not initiate a climb or descent, all by itself.

 

Ah thanks Bert

[macwino 14]

This thread has been very helpful to my understanding how the AP functions. One thing, however, that I'm not clear on, is the use of the VNAV button. I am using Bert's mods with the GTN 750, and perhaps that is the source of my confusion.

 

In any event, I find the button to be non-responsive. Pressing it gives no annunciation in the PDF. And it seems to have no effect at all on what's going on, although the Carenado manual seems to indicate that you should first press this button and then proceed to select VS or FLC. 

 

Here's the specific manual provision that I'm referring to:

 

VNAV: The VNAV button selects/deselects the VNAV mode. When VNAV is active The FMS (or the pilot) is able to command various vertical modes (VALT, VFLC, VVS) based on the current FMS flight plan (or pilot input).

VALT: When climbing or descending or by pressing the ALT button in the FGS, the system will captured either the altitude written on the flight plan (VALTV) or the altitude commanded by the altitude preselector (VALTS) or the altitude that you had when the ALT button was pushed (VALT).

VFLC: When the FLC button is pushed or when the FMS commands a change in vertical mode to the FLC mode the airplane maintains the indicated airspeed at the time the mode is selected. It can be modify by the pilot by rotating the speed knob (this is how most pilots do it). Selected speed is annunciated over the airspeed ribbon.
VVS: When the VS button is pushed while in VNAV.

VVS becomes the active vertical mode. The pilot can modify the current VS by using the VS/Pitch wheel. 

 

Thanks for any input.

Robert

 

[barrel_owl 304]

Robert,

if you use Bert's mod, VNAV is inoperative.

[macwino 14]

Simple enough. Thanks.

[X24 15]

In the real world, ideally ATC will give you a descent clearance before top of descent, although here in Australia, sometimes it's after!

So, you would set that cleared altitude on the FCU or other appropriate acronymical device, but not actually initiate the descent till TOD using either VS, pitch or FLC.

 

VS can be nice to use, but some operators forbid its use for initiating a descent because it is possible to navigate away from a captured altitude with it without requiring a lower (or higher) altitude to be set, so you can actually start descending without a clearance which is of course a big no-no. Pitch will do the same thing. FLC should automatically try and fly to the selected altitude.

 

This ain't written in stone of course, just offered as food for thought...

[CaptKornDog 281]

Sorry for bringing up an old thread but for the life of me, I can't get ALTS to arm. I activate the FL Alert in the MFD menus and can get ALTS to arm on initial climbout. But after that, in either VS or FLC mode, can't seem to trigger it.

 

Add me to the philosophy where I'd expect the aircraft not to actually begin changing altitudes until I actually select a new pitch mode also. Not the arbitrary 500 FPM climb or descent (whatever it is).

 

Any help would be appreciated.

[X24 15]

Kyle

 

One of the "interesting" features that Carenado have designed into the auto flight system is that arming or engaging a particular lateral or vertical mode does not necessarily disengage the previously armed or engaged mode(s).

 

Engaging a mode after takeoff can engage the autopilot too. Disengaging the autopilot may completely or partly disengage whatever modes were active and/or armed.

 

There is a clickspot in the centre of the altitude knob labelled PUSH TO CANCEL or some such (I'm away from my computer till tomorrow when I can have a look at this in more detail). The FMA is not always a reliable indicator of the state of the auto flight system, so I generally have tooltips ON: hovering the mouse pointer over a button or knob will let me know what state it is in - ON, OFF, ALTS, ALT HOLD, NAV etc.

 

It's worth having a play around with the push to cancel function which I can use to put me into pitch mode that you can then directly control with the thumb wheel.

 

I've also found that even when in FLC, VS can remained armed in the background, so that moving the thumb wheel will change the VS selection "donut" on the VS scale, and the aircraft will now pitch towards the commanded vertical speed. Some more button pushing is required to re-acquire FLC. In many cases, the auto flight remembers the most recent selection made, and although this may now become the active mode, it does not automatically disengage or remove the previous mode. That's why it seems to be necessary to reset the AP/FD just prior to arming an approach sometimes. It dumps whatever was active, and starts with a relatively clean slate.

 

Figuring out the logic pertaining to specific modes and manoeuvres takes a lot of patience, practice, note taking, and trial-and-error. It may appear to be inconsistent, but it is nonetheless just following the logic that was designed into it. Our task, should we choose to accept it, is to determine the exact sequence of commands that will produce a desired result.

 

The PFD option for FL ALERT is supposed to remind you to set QNH or 1013 when descending or climbing through transition if you haven't already. My scale flashes, but won't stop regardless of what's set.

 

Have a look here too if you haven't already: http://www.avsim.com/topic/470992-hawker-flc-does-work/