Hi - I’m trying to make sense of autopilot modes for assigning bindings for the honeycomb bravo. I’ve read various posts on this and watched key youtube videos (SimHanger and RMag). I actually think the RMAg approach is not correct - at least not for GA aircraft - but that’s not relevant for this question).
I understand the difference between VS hold vs FLC mode. But there appears to also be an indicated airspeed hold (IAS) - and there are different bindings in controller options - I see these options:
Set Autopilot Airspeed hold
Autopilot Airspeed Hold
Autopilot Airspeed Hold On (and Off)
Toggle Autopilot Flight Level Change (and On/Off versions)
This would suggest that Flight Level Change is a different autopilot mode than Airspeed hold - but I’ve not found anything that describes how these differ.
I’m wondering if particular autopilots (in particular planes) support one or the other - but again, I haven’t found this described.
Related to this - in planes that use the KAP140 - when you have ALT hold set - is there any way to change the speed? I believe AP is controlling the elevator - so would one use the throttle to control speed when AP is engaged?
I’m not sure that I wholly understand what you’re getting at Hokfujow but:
If you select IAS on the HC Bravo left hand rotary you can then set the IAS which you want the aircraft to maintain with the right hand rotary. That required speed will appear as a caption above the airspeed ribbon on the PFD. If you then select the IAS button (so that it illuminates) and leave it at that then the AP will stay in ROL mode and try to maintain that speed for you. You will have to manage the aircraft in pitch though. If you wish to manage a change in change altitude with the AP then you can set the left hand rotary to ALT and use the right hand rotary to set the altitude that you wish to achieve and this will appear ,FLC will be displayed in the AFCS Status Box and the aircraft should commence a climb to that altitude at the desired airspeed, but remember you have to manage the throttle to ensure that the power matches the demand, the AP does not do that for you.
If you want to change altitude at a defined rate in FPM then select VS on the left hand rotary, then the VS button and then use the RH button to select the rate of change that you want to achieve. That will be a positive figure for a climb and negative for descent, managed by the direction in which you turn the rotary and this figure will appear to the right at the top of the Altitude ribbon. The actual rate of change will appear next to to the right of the current altitude. Again, you must manage the power.
I believe it to be common practice to use FLC to climb because that should ensure that you don’t lose airspeed and stall as the AP will match the climb rate to the available power. The VS is more commonly used for descent where the caution is to ensure that you do not overspeed.
All of this, of course, with the AP engaged.
If you have the HC Bravo set up correctly the binds for the various AP functions are already mapped. If you have the HC Alpha as well then there is a bind conflict between the HC Bravo switch binds and the HC Alpha binds and those have to be managed to avoid potential problems.
You might try searching on line for the G1000Nxi Pilot’s Guide Manual which is available as a free download from various sites and then you can thoroughly confuse yourself . Be sure to look for the manual for your aircraft type as there are differences.
Hi there - thank you very much for this. You actually answered a few questions I hadn’t asked yet (but was going to!). And yes, I’ve dealt with the overlapping bindings on the alpha and bravo, as well as couple default incorrect bindings on the bravo.
I think part of my confusion might be coming from the fact that I’ve mostly used GA aircraft with KAP140 AP so far. I think some of these functions are not available on those.
Here’s the part that was the crux of this particular question - but I think you answered it indirectly. It seemed to me that setting an airspeed (the IAS button on the Bravo ) had to do with the FLC function (which also maintains a speed). But it sounds like the set airspeed function has nothing to do with changing level - this is the part I’m trying to make sense of).
If I understand this right (which is questionable) - you can set FLC mode - and then decide what speed should be maintained? Or is that not how it works?
If you bind Set autopilot airspeed hold - are you turning on FLC ? Or is that totally unrelated? Alternatively, if you turn on FLC mode, how do you set the airspeed you want to maintain?
FLC is used on Aircraft ( usually airliners) with auto throttle
so a speed needs to be set and throttles engaged and then when changing alt it will maintain your selected airspeed and adjust climb rate to suit
On non Auto throttle aircraft IAS is maintained by pitch so it is used instead of VS or FLC
I personally never bind anything and just use controls in cockpit or my Logitech AP panel so i cant help with bindings
No FLC will use aircraft throttles and pitch
IAS hold on non AT aircraft will use just pitch and you have to use throttles
an example would be a turbo prop like PC12 or Grand caravan you would use IAS hold so you don’t exceed speed restrictions like 250 knots under 10k
FLITCH (Flight Level Change) is a more advanced feature usually found on airliners.
It’s basically a mode at which the pilot instructs the aircraft to change the flight level based on the best power available (max EPR/engine power rating) for climbing up and full engine idle for descending down. The autothrottle and autopilot modes do then just exactly that: change the flight level of the aicraft as commanded, ignoring more argumentative modes such as the VNAV-profile that would also direct speed restrictions and altitude restrictions (Flitch ignores those)
IAS climb/descent is based on your own throttling. So if you’d like to descent, you press IAS mode and gently pull out some throttle after which the aircraft will pitch down to maintain that speed, but using the accelaration by gravity to keep up with it. For climb, you’d hit a good climb speed, press ias, and every power setting above that will be shaken off in the climb profile of the aircraft.
Given most (not all) single engine GA will top out under 250 knots in straight and level, you’ll usually apply near full power on climb out anyway, and most best rate of climb is well under 200 knots - anywhere from 70-120. So using FLC simply applies the best pitch to match and hold that airspeed.
I think that reference to airliners and auto-throttle is irrelevant to the OP’s questions if he/she is flying solely GA . I think the questions that are raised in Post #3 are best addressed by example so:
Starting with the aircraft C & D carry out the checklist and start the engine(s). With the avionics master ON and the MFD live enter the flight plan, if you are using one; often I don’t. Assuming that you want to climb out at the best climb rate (other climb rates are available), which will be achieved at a speed specified in the POH, set that airspeed using the IAS selection on the HC Bravo. Assuming that you want to climb to a specific altitude then set the LH rotary on the HC Bravo to ALT and select that altitude. Once airborne and cleaned up toggle the AP to ON and the aircraft will climb at that specified indicated airspeed until it reaches the desired altitude at which point it will level out. Keep a weather eye on the AFCS Status Box on the PFD and you will see things change colour (white to green) as the process progresses. Just as Casual Click says if you are operating in most GA piston engined aircraft you will be at or around max MP and RPM throughout most of the climb but there will be some guidance on that in the POH.
If you follow the above procedure but DO NOT select FLC then you will have to use the throttle to manage the rate of climb.
You can follow the same procedures to change altitude whilst airborne.
Again, I urge you to download and refer to the Garmin Pilots Manual for whatever AP you are using. I would also highly recommend You Tuber “Huddison” who has created a series of videos ‘Back to Basics’ and he covers, amongst many other things and with a good level of clarity, the various G1000Nxi functions using the Cessna 172 as a platform
I think the difference between FLC and IAS is mostly just semantics; they both maintain an airspeed you choose by altering the rate of climb/descent. With AT, you don’t have to manage the power, without AT you do.
Edit: changed the last sentence as I had it wrong by 180°.
So do the two separate bindings do two separate things in the sim? Or do they always do the same thing, with the differences being related to the plane and its autopilot, and they’re just duplicates for historical reasons?
FLC: Flight Level Change. All FLC does is climb or descend at the selected airspeed, through command of pitch. Typically, this will default to the speed at which you selected it (i.e. pushed the FLC button), but can usually be changed by some means (depending on the AP).
It certainly can be used with auto throttle, but it doesn’t need to be. Without AT, YOU are the auto throttle! Typically, you might select climb power or idle. But you can select less (or more) if you are climbing/descending faster than you’d like.
V/S: Pretty much does what it says on the tin. The only important difference from FLC is that V/S will typically respect NO limitations. It’ll stall you. It’ll overspeed you. I say “typically” because some airplanes are smart enough to drop out of V/S when they approach one limit or another.
Also bear in mind that, without AT, the auto throttle is still you. The AC will hold your selected V/S, but you control the speed with throttle.
EDIT: After a bit of research, I came upon this:
As @Ephedrin87 has stated below, IAS is the same thing as FLC, Level Change, etc.
Not being especially familiar with it, I was assuming that we were speaking of two different functions on the same panel, which I had never seen. This makes IAS different than, say, Selected Speed in an Airbus.
Since most of what I wrote after this was conjecture, it can be safely disregarded as it has been better explained in the link above and by @Ephedrin87 below.
The operation of FLC and VS described above is as it works in the aircraft I have flown.
IAS: It isn’t what I’m used to calling it, and I don’t know how it’s implemented in a particular AP, but I’d submit that IAS holds your speed, in level flight or otherwise, if it wasn’t being held already (by something like FLC).
In most larger aircraft, the AP in a climb will display on its flight display something like CLB HDG FLC for example, Climb (an AT mode or the mode that the flight management computer will display for power settings, etc if the AT is not equipped/not in use), Heading (the roll mode), and FLC (as we discussed)
But, when the AP reaches its selected altitude, the display will change to, again for example, SPD HDG ALT, or Speed, Heading, and Altitude. If the aircraft had a AT, it would hold the (IAS) selected. If not equipped, it might still display a bug on the flight display to allow the pilot to see what his speed was bugged to.
It’s difficult to say how this all works in a particular autopilot, but generally the concepts are the same. For instance, IAS in a climb/descent basically is FLC. That being the case, the AP may ignore the IAS button push if you were in FLC already. Alternatively, since it is possible that you might want to hold a VS AND an airspeed, pressing IAS while in VS would command (or bug without AT) the selected speed so that the AT, or you, could adjust the throttle appropriately.
And again, if you have AP, AT, or both it would do as you ask. If you had neither, it might still set the bugs on something like a Garmin so that you had targets displayed that you could follow.
Well that was a lot less pilot speak than I was intending, but hopefully it helped just a bit.
This is pure theory on my part, but I believe that all these different bindings are, often, different ways to skin a cat…particular to sims.
Just like the bindings in MSFS for Full Throttle, Half Throttle, etc, vs “Increase Throttle 5%” vs several ways to set the throttle axis, the bindings above all sound like the same settings but one allows you to select the value, another allows you to toggle it, and so forth.
FLCH and IAS modes are the same thing with a different name.
FLCH is mostly found in Boeings, in an Airbus it would be named Open Climb/Descent. IAS is Indicated AirSpeed, it will pitch for speed, as simple as that. Both can be used with or without an autothrottle. Boeing’s and Airbus’ IAS modes use max rated thrust or idle when the AT is used but at least in a Boeing you can easily use manual thrust as well. Maybe even in an Airbus, no idea.
There are many addons in MSFS whose IAS or FLCH buttons couldn’t be bound to the sim’s control settings the last time I checked it. For example in the DA62 with Tommy’s mod I had to use AAO for the FLC button.
FLC/IAS is a save mode for climb as it will prevent you from stalling out for the sake of a high climb rate. It’s also an easy to manage descend mode if you are airspeed limited.
VS will hold the rate of climb/descent, regardless of speed, angle of attack, angle of climb/descent. Always keep an eye on your speed when using it. Vs (stall speed here) and Vne both come quicker than desirable.
Please, continue. I’m not saying any of this to be contentious.
But this is fundamentally how the AP/FD works in the aircraft that I have flown them in, primarily the Kingair 200, Citation Encore, CRJ-7/900, B-737 (both with and without AT), and the A-320.
I have the least experience in GA autopilot but, even in MSFS, the basic concepts work this way. The execution can be quite different of course. For instance, I don’t recall our Kingair having Altitude Acquire or ALT Star in Airbusian. So we had to level off manually.
If it works differently in your experience (and the KAP for example is an entirely different breed of cat from an Airbus box), I would genuinely like to know.
EDIT: I’ve added a link to an article about IAS above. Not having familiarity with it, I was incorrect in my conjecture on how this particular function works. However, the FLC and VS functions work as I have described…at least in the installations that I have flown them.
Another important difference between FLC/IAS and VS is pax (and pilot) comfort.
There are many airplanes, even some airliners where FLC is very uncomfortable, even nausea inducing due to the constant and frequent pitch changes if the weather isn’t 100% calm.
