While I have an audience…
I have questions about the FLC function in the Autopilot. I come from FSX, where activating Alt Hold meant that the aircraft would ascend or descend to the specified alitude setting, to FS2020 where all the autopilots I’ve used, G1000/G3000, will hold the current altitude, not change it, when you activate Alt.
All the things I’ve read say FLC is the preferred method of changing Altitudes with the AP. As opposed to Vertical Speed, FLC can only be accomplished if you are not at the extreme throttle position. In other words, if I am cruising at full throttle and want increase my altitude, FLC can’t do it because it will try to maintain the current speed and I would have to give the plane more power. Is this correct? So the only way to accomplish a higher altitude at full throttle is by using VS?
Same is true descending (in reverse..)?
You need to use the Nose Up and Nose Down buttons to change the speed.
Every aircraft has a Vy speed - best climb rate at a given speed. Usually marked on your PFD’s Speed tape. Assuming you don’t have autothrottle, use ALT SEL to specify the height to which you want to climb, press FLC. Reduce power to that speed.
Cruise climb speed is also worth mentioning.
To descend, you can use VS. You’ll need to manage two things - one is your VS rate (i.e., 1200 fpm) and your forward speed - both need to work to get you to the target altitude by the waypoint or designated point on your flight plan.
For that, many avionics have a ALT ARC which puts up a blue arc on your flight plan. It basically indicates at given current speed and or ascent/descent rate (it works for both climbs and dives), that’s where you’ll achieve that altitude. You need to set a target height in ALT SEL 'natch.
I believe the norm is to use FLC for climb and VS for descent.
With FLC: if you are in cruise, change your set altitude higher and engage FLC, FLC will automatically pick up your current cruise speed. Unless you then change something the aircraft will not actually start climbing. There are then two ways to actually start climbing:
- Decrease the AP target speed
- Increase power.
The “normal” procedure is to reduce the target speed from the current cruising speed which the AP initially automatically selected when you click on FLC, to the correct climb speed. This is normally - but not necessarily - your aircraft’s best rate of climb speed. You can typically choose any lower speed down to best angle of climb speed to something higher than best rate of climb speed as a “cruise climb”. Note that best practice is also to increase power from your cruise setting to the aircraft’s normal climb power setting.
When you do all this, the aircraft will pitch up to attain, and then maintain, the selected speed at the set power until it reaches the new, higher altitude. Note that you cannot specify a rate of climb: the aircraft will climb at the rate determined by the power and speed settings. When you get to your new altitude, aircraft will level off and the speed will start increasing. At that point you should reduce power to cruise setting.
Errm I always understood that FLC does not care about power settings but will adjust pitch to maintain whatever speed is commanded. The only requirement is that the power setting is high enough to actually be able to climb at the commanded speed.
Power setting matters. If it either doesn’t have enough power for climb or too much power for descent it will not pitch to what you are trying to achieve. All FLC does is pitch the aircraft to maintain the target ias. In aircraft without auto throttle the pilot has to do the power adjustment.
Does anybody know why my Vision Jet or PC-12 NGX pitch down to unsafe rates of descent when I use FLC to descend?
Why is it even an option to use for descending if it wants to kill me?
It doesn’t care about the rate of descent. It cares about the airspeed that FLC is bugged for. If you want to descend I suggest using VS or VNAV.
My understanding is that FLC is meant to be used for climb and VS used for descent.
Note that even VS has the potential to command an unsafe speed if too high a descent rate is selected.
The point is, it doesn’t care about bugged airspeed. My bugged airspeed was under 180kts yet when i selected FLC it took me to >9000fpm at over Mach 0.5.
If it cared about bugged airspeed in descent, you could just select a speed within the safe operating limits and hit FLC, and it would maintain that speed with an appropriate level of descent relative to thrust, as the Cessna 172 does. The Vision Jet and PC-12 don’t do this.
Im reality, theres no reason why both of them shouldn’t work, as long as the correct airspeed is selected. FLC works for descent in the Cessna 172 in that manner. It’s just the Vision Jet and PC-12 that seem to ignore bugged airspeeds. I don’t understand why.
FLC/IAS mode is not fully automated and still requires the pilot to know their aircraft. You have to select an appropriate power setting and aircraft configuration. Aircraft with autothrottle’s take the manual setting of power away but the pilot still needs to operate within what’s possible.
I was flying using AP and AT, selected a speed below cruise speed with MAN mode, and a target altitude of 3,000ft whilst cruising at 17,000ft. When I hit FLC it just nose dived the aircraft at over 9,000fpm.
What am I doing wrong?
While at 17,000 I set a target of 3,000 hit FLC and brought the power back a bit. Naturally as the speed decreased the nose dropped and then picked up again to capture the speed FLC was bugged at when I engaged it. I was able to set this to the speed I desired and the nose pitched accordingly to capture and maintain that speed and I didn’t see a 9,000+ FPM descent rate.
It should work just as @Maki152 described. I suspect you did something different to what you told us. If it happens again a video will help confirm what you see.
That’s odd. It only seems to happen to me in those two planes so far, the Vision Jet and the PC-12. Every other aircraft I’ve used have worked fine. There must be something else to it because I definitely had the configuration as described.
I’m using the Thrustmaster Airbus TCA, and I’m thinking it may be a binding issue with the throttle levers conflicting with the throttle on the sidestick. I had an issue with flying helicopters until I disabled the throttle on the sidestick, so I may try that.
Since having these issues I’ve stuck to descending with the VS instead.