HI. I use Honeycomb Alpha and Bravo. When on Autopilot, I select an altitude, it works. I select a heading, it works. BUT if I press “Hdg” off, it keeps the altitude (that’s OK), but refuses to let me control the heading. It keeps on heading to … some heading I don’t know what it corresponds to. Did I do anything wrong in my AP setting? Is that a common issue?
1 Like
Thats the way most AP work IRL as well.
Either it controls the aircraft or it doesn’t.
You can’t choose a single axis.
If you disengage the heading mode, most autopilots revert to a basic wings level or roll hold mode.
OK. Thanks. Strange… but thanks, good to know 
I flew for 30 years (small planes, no multi, no jets) and used some - old generation, I must admit - autopilots. I did not have this problem.
The best way (for me anyway) is to keep it in AP mode and use the incr/decr knob while in HDG. You can then simply dial in the direction you want to fly and easily switch between ALT and HDG changes. I enjoy flying in this manner and using external view or even drone view for some of the more fascinating areas of the globe.
Another thing I enjoy doing that has nothing to do with your question but everything to do about the sim. I have the Bing desktop app on my computer and every morning when I boot the computer the background changes to another, usually beautiful picture with a short description of where/what the picture is. I often then find that place using Google Earth and find the closest airport and go and visit that place. I’ve found places on the globe I had no idea even existed and some are amazing.
3 Likes
So, in order to just have ALT activated in the AP (without HDG), you would have to switch AP off, then back on and hit ALT?
No. You simply turn off HDG mode.
It makes no difference if you enable the AP without HDG first, or if you deselect it afterwards.
But you replied to the OP that it’s all or nothing, did you not, and that IRL you can’t switch off HDG while AP is still active? I must be misunderstanding.
“Either it controls the aircraft or it doesn’t.
You can’t choose a single axis.”
If you want to manually steer the plane while leaving the AP in ALT hold, how would you do that?
You can’t. If the AP is not in HDG mode (e.g. deselected), it’s either in roll hold or wings level mode.
Understoood. Thank you.
Then, past sims (FS9 for example) were incorrect? The AP on those planes did allow for this if my memory is correct…
If this was possible in fs9, it was incorrect for most aircraft.
As @ACJaydee mentioned, some very old and very basic APs were able to e.g. just hold HDG and/or ALT.
Do you have a Bravo Throttle Quadrant? If so then you simply set your ALT using the left hand knob selector in conjunction with the incr/decr knob, then switch your left hand knob selector to HDG and control direction using the incr/decr to move your HDG bug around. The AP will follow your heading bug. It’s not manually controlling it using the yoke, but rather the input from the Bravo.
If you don’t have the Bravo then this entire thread is moot to you. However you can still perform the same functions as described above. You just do it all with the mouse, virtually.
With the heading bug you can neither adjust the bank angle, nor the roll rate.
Not really comparable to manually controlling the heading.
1 Like
And I’ve noticed that if you do manually bank the plane, the AP will disengage losing ALT control as well. So you do have to only use the HDG bug.
Not being a real world pilot, it seems a waste of technology to have sophisticated AP/ Nav systems and not be able to independently have HDG or ALT engaged…
1 Like
No, it isn’t a waste of technology.
It makes zero sense to control only one axis.
The AP has been designed to reduce the workload and hence takes over the control of the aircraft.
Furthermore this would be a source for errors.
E.g. you ‘think’ the AP is controlling/maintaining the altitude, but it isn’t and starts descending while you are manually turning.
I partly agree with you “The AP has been designed to reduce the workload”, but IRL, there is a button on the yoke to disengage temporarily the HDG. I can tell you that when flying under AP, there can be situations when you NEED to change HDG rapidly and not degree by degree as the knob on Honeycomb Bravo permits. Maybe there is a way to program one of the buttons on the yoke to that end !?!?
1 Like
Didn’t this CWS or TCS disengage all servos? At least on the Dash7 it was that way.
also not fitted too often anymore these days AFAIK.
E.g. Boeings never had that.
If you need to change the heading rapidly, you simply disengage the AP and reengage it afterwards.
That’s e.g. the TCAS avoidence procedure as well.
When this happens, you fly.
If rapid changes in attitude are required then the pilot takes over and “flies” the plane. Once the situation is stable you can re-engage the AP.
As @PZL104 states, there is a function that will allow the pilot to make changes without disengaging the AP but none of these systems were designed to allow the pilot to get out and float behind the aircraft, taking pictures, while still steering the aircraft.
AP systems have evolved a lot over the years. We used to fly airliners by hand with only the assistance of what is described as pitch and roll mode with CWS.
More info, if your interested.
The 737-200 Sperry SP-77 Autopilot had very few functions but was very useful when you needed it. The AP basically worked on the principle of CWS (Control Wheel Steering) and would maintain “parameters” (pitch/roll) set by you.
For example:
You’re just departing Edmonton Intl Airport in Canada with a fully loaded CP Air 737-200, heading to Tuktoyaktuk. Pitch + power setting control vertical speed and airspeed. Pull the nose up until airspeed is V2 + 15 at climb power. Small pitch adjustments will be required during the climb to maintain that desired airspeed. (This is what we now call FLC. Maintaining an airspeed rather than a vertical speed.)
You activate the Autopilot (ELEV + AIL). The autopilot will now maintain wings level and your current pitch. Since you control airspeed with the pitch, you see that your speed is increasing, but you want to climb with 220 kts. So you pull back on the yoke until you maintain 220 kts. Let’s say this gives us a pitch of 9 degrees. If you now release the yoke, the autopilot will trim the elevator trim in order to maintain 9 degrees of pitch. No matter how fast you’re going or what the engines are doing, it will maintain 9 degrees of pitch UNLESS you change something. Same with descending. Pull the power. Point the nose to the desired path/airspeed and let go. The autopilot will now hold that until you change it.
Level flight was achieved in the same way. When reaching cruise altitude, push the nose down to maintain level and set cruise power. when stabilized, let go. The AP will trim to hold pitch.
The pilot would have to manually adjust the pitch cmd dial just to the right of the alt hold switch which would artificially set your FD to whatever pitch attitude you desired. There was no automation to what we now have as a FD, just a pipper on the artificial horizon that you would set and use as a reference.
Heading control was done in much the same way. Bank and let go. The AP would hold the bank angle. Roll out on your new heading and the AP would then keep the wings level. The whole system was very similar to the Airbus “Autotrim” used today.
Track angle and drift corrections are done by looking at the ADF and VOR indicators. We used every radio signal we could in conjunction with the ADF to triangulate position and make course corrections accordingly. ( The -200 I flew in the far north had a rec set that allowed us to tune in darn near any radio band imaginable for DF (direction finding). To augment navigation when radio signals were sparse, we could use the original GPS, (Global Positioning STARS).
EVERY instrument approach was flown by hand with AP pitch/roll hold. No such thing as autothrottle. Autoland was just another word for Crash.
3 Likes
Oh dear…a sextant! I’m having nasty pre-GPS flashbacks! 
2 Likes
Those would be the good ol’ days when navigating was an artform.
I guess we can call that magenta squiggle ‘art’…
I still remember when I first saw an HSI IRL.
Couldn’t believe how much easier intercepting VOR radials suddenly became.
1 Like