Autopilot Altitude Hold problem Since Latest Stable Update

[tmansteve]

Altitude Hold has been working fine up until now. I have read through the update notes but might have missed something. I set the plane nice and level with autopilot on and altitude switch on. Press NWS but the AP/ref stays on. I tried keyboard key just in case but nothing. Is anyone else having this problem?

 

I have read some earlier answers and will see if it will work because I know I am doing everything right.

 

Cheers

Steve

Edited August 20, 2021 by tmansteve

[eatthis]

your climb rate has to be within 200 feet per minute now so its a bit more fussy, it does work for me though

[tmansteve]

Thanks eatthis

 

Will have another go and check climb rate

[Biggus]

One thing that's really helped me is to watch the rate of change on the altimeter more than the VSI as you level out. There is a bit of lag in the VSI.

[tmansteve]

Thanks for the tip biggus. Will keep an eye on that. 

[Callsign JoNay]

Altitude hold is still gradually descending me though. It won't hold an altitude over a long period of time like it used to before the AP update a few patches ago.

 

Anyone know if this is a bug or a feature?

[51GRIZZLY]

On 8/25/2021 at 6:08 PM, Callsign JoNay said:

Altitude hold is still gradually descending me though. It won't hold an altitude over a long period of time like it used to before the AP update a few patches ago.

 

Anyone know if this is a bug or a feature?

Got the same observation, AP is gradually decending sometimes up to 50-70 ft. when i sweep the wings all the way back after activation. I would say, it looks like a bug to me 

[Victory205]

The autopilot trims at 1/10th of the normal, manual trim rate. It can’t keep up with manually sweeping the wings aft like that due to the change in Cp, nor is it able to keep up with extreme acceleration or deceleration. It’s not an airliner autopilot, it was generally used by turning it on after the pilot stabilized the aircraft at the desired altitude and airspeed. 

[Callsign JoNay]

16 hours ago, Victory205 said:

The autopilot trims at 1/10th of the normal, manual trim rate. It can’t keep up with manually sweeping the wings aft like that due to the change in Cp, nor is it able to keep up with extreme acceleration or deceleration. It’s not an airliner autopilot, it was generally used by turning it on after the pilot stabilized the aircraft at the desired altitude and airspeed. 

In the current OB the autopilot slowly descends the aircraft even if I hold a consistent speed with 20 deg sweep. 

If I depart as per NATOPS at 300 kts, 500 feet, sometimes I descend to 400 before I get to 7 DME.

Or during recovery if I establish overhead angels 2 at 250 I will drop ~100 feet during an orbit in the stack.

The VSI needle is always a touch below 0.

Does that sound like a bug or feature?

[AH_Solid_Snake]

This might be driven by a mismatch between expectations and reality. The F-14 autopilot isn't a digital system coupled to a FBW like the F-18 for example. Fundamentally its an extension of the analog stab aug system that can use very small trim adjustments to null rates, detected by accelerometers. 

There isnt a digital input of altitude to compare against a set desired altitude and drive the aircraft to it, there's a gyroscope somewhere detecting a trend upwards, and a trim tab responding to it, its a reactive system not a pro-active control system.

For all those reasons the autopilot shouldn't be used as a poor mans FBW to fly the aircraft, it can be very helpful at night, or orbiting in the stack twiddling your thumbs while all the F-18s take 10 passes to get on deck. But it absolutely isn't a substitute for manual trim and flying the aircraft.

[Baz000]

Alt hold doesn't seem to hold alt in even a shallow 10 degree turn

 

[AH_Solid_Snake]

I can only suggest videos or tracks at this point. Completely anecdotally the AP works perfectly for me.

[Golo]

I have not checked recently, but for me there was slight descent of about 30-50ft upon AP engagement, and then it held that altitude OK. It looks like 3 autopilot cases 3 different results. Say what you will here, but I actually like it, it is like everyone has a planes with their own little imperfections, it gives HBs 14s "soul" if you will. I dont want this fixed.

Edited October 20, 2021 by Golo

[Steve Gee]

On 10/12/2021 at 4:14 PM, Victory205 said:

...It’s not an airliner autopilot, it was generally used by turning it on after the pilot stabilized the aircraft at the desired altitude and airspeed. 

How much of a mission was spent using autopilot?

[stuart666]

I had difficulty setting it up too. It DOES work. However, the light remains on when you move outside the parameters of the autopilot, and previously that would turn it and the system off. Ok, so we have the paddle, but that means you have to turn back on your stab channels as well.

TBH, I was cheating and using the autopilot to trim around the boat. Much as I hate its adjustment to this level, its undoubtedly the right thing to do. It was something of an exploit.

Edited October 24, 2021 by stuart666