That is my hope too. I suspect there is more to this accident than autopilot mismanagement.

Isn't the truth that it monitors the altitude and controls the attitude accordingly?

Agree with most of what you have stated, and I feel tremendous sadness for the family and friends of this Father and Daughter who loved aviation. I hope the resulting investigation will deliver some lessons that we can reflect and learn from.

Your criticism of the autopilot system is probably and understandably from a modern Jet perspective. However ancient autopilots of the era are not that far removed from modern autopilot function in non-fadec piston engine aircraft, in that they do not control power. This particular autopilot did control altitude, attitude and glideslope, but not trim (which may well have been the cause of the accident), but many autopilots of the era did.. as they incorporated electric trim. This Century 2000 unit was designed for aircraft with no electric trim fitted.
Leaving aside for a moment that the autopilot was probably 35 years old and modern advances in digital electronics, reliability, weight savings have changed the game to some extent.. the function is not that much different if you understand how the thing works.
A reasonably similar fatal accident occurred with a PC12 in February last year with the latest of tech.

In ALT mode the AP attempts to maintain the difference between the altitude and the altitude target at zero. It is controlling the aircraft altitude. How it does that, and the concept of inner and outer control loops, is probably out of scope here.

Yes. It is an altitude hold only option. It has its own barometric pressure sensor and can only alter the attitude via the elevator. No electric trim and no auto-throttle. There is a trim up/trim down indicator on the autopilot display that the pilot is supposed to monitor and make appropriate adjustments with the trim wheel. It is not clear if the pilot understood this.

There seem to be several people posting here who do not understand the proper response to illumination of the trim annunciators. Only after setting appropriate power for the desired climb or descent vertical speed should a trim annunciator be taken as an indication to change pitch trim.

Forget about the autopilot for a moment. How do you transition from hand flown altitude hold to hand flown VS target climb or descent?

Other than an off-hand comment the accident pilot made in one of her videos, I am not aware of any evidence to support her father holding any pilot ratings.

With ALT selected the "annunciator" (two labeled lights) will tell you to trim if necessary. Same with HDG or NAV, it doesn't know it just senses control loads.

You are flying AP coupled ALT hold mode and the aircraft is in trim at the desired airspeed. You fly through a sinking airmass. The AP drives the pitch servo to increase nose up elevator and illuminates the TRIM UP annunciator. What do you do?

I would add power.

I think the correct answer is: do both. Follow the indication of the trim indicator to make life easier for the autopilot and add power if you observe the airspeed decreasing.

It has been thirty years since I flew a Rockwell Commander 112a with a Century autopilot. It had electric elevator and rudder trim. In ATL only small MP adjustments were required.

I'm mot criticizing the autopilot, it can't do more than it was designed to do. My criticism is pointed at those, who use this system without the proper system knowledge. While I feel sad about the death of the female pilot and her father, it still is most probable that the pilot failed badly. There also remains the question wether she received ample instructions about the limitations of the installed autopilot system with manual trim only, training and evaluation could be the elephant in the room.

I have no modern jet experience, as my nickname states I flew Phantom F4 aircraft, over 3.000 hours, 1/3 of them instructing and evaluating. The most civilian modern jet Cockpit I ever occupied as a pilot was a Caravelle simulator for ATPL training and following successful check ride.

The autopilot of the Phantom was similar in the limitations as the century series one and could kill you if operated without the necessary oversight and control. Especially the "Altitude hold" had its traps.

That brings me back to responses like
"it controls altitude", it could cause out of trim conditions....."


Afaik from the manual and the informations provided this aircraft had no electric trim and no auto throttle, all the inputs from the autopilot acted directly onto the yoke. If the pilot does not trim manually, then the trim stays at its position where the pilot had put it prior engaging the autopilot. Same with the power. An out of trim situation is caused when the aircraft parameters ( TAS, pressure altitude, CG to name a few) are changed and the trim is not adjusted manually and / or the deviating parameter is not corrected to the original value.

There might be a misconception about using the term "control" and it might be on my side, as I'm no native english speaking person. Only an autopilot controlling auto trim and auto throttle could control altitude alone over time. Such a system needs a lot if inputs and feed back loops the used autopilot in the discussed accident aircraft didn't have. Sure an average pilot can use this autopilot to control the altitude without auto trim and auto thrust, the autopilot alone can't and here the knowledge of the pilot looks amiss.

Going back to my original post, this autopilot only acts on the yoke, operating power and trim are out of its reach as it would be to a pilot whose hands were tied to the yoke. Would the pilot have known this, she would have controlled speed and altitude, the traces show no sign of such action, to the contrary. The oscillation deviation of speed and altitude increases in each cycle, until hitting the ground.

There is a time to be sorry, but we only learn from the truth. Not saying though that it will be my truth. Enough said, there will be those who understand, and those who will have to make their own way of learning.

Fly safe, merry Christmas and a peaceful year 2024.

it doesn’t do gps glide slopes though (afaik) and certainly not on my bird

He was not a rated pilot. My understanding is that he liked to accompany his daughter and she felt more comfortable with him aboard. From the few videos I watched after the crash, she seemed to rely upon him quite a bit to assist with looking outside while she was heads-down and for general support with the aircraft. There were a few radio calls she missed that dad had to prompt her to respond. Also, she had more than a few “why is it doing this” questions that dad helped figure out.

Such a sad tale, poor lady trying to make her flying dream come true (perhaps too prematurely it seems), and whilst doing so her Dad also loses his life as well.

All very tragic, and quite telling that One's Training and your very own aptitude to Fly is paramount.

Poor folks.

Seems to me that this autopilot needs to activate the Master Caution if it calls for re-trimming but re-trimming has not been adjusted for, say, 5 seconds.

A little trim up or trim down light on the autopilot itself seems a bit too subtle to me. Is there a trim demand light in front of the pilot as well ?

Of course, any competent pilot would be used to automatically re-trimming after a power or speed change. How did this pilot's lack of trimming and mode confusion come to pass, and why did her instructor sign her off ?

FLY, Navigate, communicate, (capitalisation deliberate).

RIP

I took the information about glide slope capability from the operarting manual that someone posted way up in this thread. Of course there are different installations of this autopilot, like with and without pitch trim capability, so not all will be fitted with this option.

Did this aircraft have a master caution indicator at all? I have flown (and still do) quite a lot on piston singles an twins, but never saw such an indicator. However, the manual of this autopilot (the link can be found in posting #44 of this thread!) states that if no action is taken for some time, an aural warning will be generated. So there is a warning system coming with the out-of-trim condition. But of course, in order to know what causes the warning sound, someone must have told the pilot about it or otherwise the pilot must have bothered to read the manual.

This is the relevant quote from the manual:

"The Century 2000 may be ordered as a Trim
Prompting autopilot. This means automatic
control (autotrim) of the elevator trim is not
available on these system. When the autopilot
displays a flashing TRIM UP or TRIM DOWN on
the annunciator, the pilot should manually move
the trim control of his aircraft in the direction
indicated on the autopilot. When the autopilot
determines that the trim condition is satisfied,
the trim lamp on the annunciator will extinguish
and the pilot should stop his trim
action. There are 2 degrees of trim prompting. For a small trim error the
trim prompt will flash approximately once each second. A large trim error
will cause the prompt to flash approximately 3 times per second. A large
error not corrected for a period of approximately 2 minutes will sound an
alert for 5 seconds. The alert will repeat every 2 minutes until the large
error is corrected."

Ah, fair enough. I have no specific knowledge of these types or this autopilot, but somehow the out-of-trim condition was missed, hence my questions.

I wonder if the aural alert can always be heard in a noisy cockpit and through headphones, and whether there is a trim light near the pilot's eye line.

Or maybe the pilot got confused and was moving the trim the wrong way - there are some clipped-on notes obscuring the trim wheel,

I would say yes absolutely, these aural warnings are designed for noisy cockpits and pilots wearing headsets.

It is in the avionics stack in the middle of the panel and clearly visible for the pilot. Watch this video here (for at long it is still available on YouTube) where she tries out the autopilot after it came back from being repaired: She has absolutely no idea what she is doing and at one point her non-pilot (as we now know) father must tell her that the autopilot is actually engaged in altitude-hold-mode. The trim light is flashing all the time but she couldn't care less. And in the end she commits the cardinal sin of disconnecting the autopilot from it's control panel instead of using the disconnect button on the yoke whilst gripping that steadily. But again, someone had to tell her about those things or she should have read the manual, neither of which obviously happened.

Everything is possible.