I have a PA39 purchased 3 months ago. It has an Altimatic IIIb with Autoflite. I understand the Altimatic pretty well, but the Autoflite system is a mystery. There are a few pages in the POH addressing these two systems, but are pretty vague. It says to turn on the Autoflite first, then turn on the Altimatic which will disengage the Autoflite. Could someone please explain the purpose of the Autoflite system, and it's relationship with the Altimatic. I am not sure what, if anything, the Autoflite does.

Thank you,

Ed Rognerud
Rosemount, MN

Hello Ed:
The auto flite is "separate" backup autopilot. It is basically a basic wing leveller using its own gyro mounted under the baggage floor. It shares the roll servo with the altimatic3 and
is only used if you have a problem with the altimatic3, be it a hard failure within the console or amplifier or and this is the primary reason for the autoflite existance, if you have a gyro failure in flight the altimatic will not work. It will of course just follow the toppled gyro until you take back control of the airplane manually or shut off the altimatic3.
When you turn off the altimatic3 the autoflite takes over using its own gyro and will give you a poor mans autopilot to get you home.
You simply use the bank knob to fly the airplane, or if its an advance autoflite, I believe it also has a nav coupling function.
Hope this helps,
Gary

Gary,

Your post has more information than my POH. Thank you very much.

Ed

 

I was under the impression that the wing leveler used the T & B gyro .Not true ?

No, it used the AI, or at least it did as installed in my 260B.

Don

No, it does not use an external Tand B gyro, it uses its own gyro incorporated in the box under the baggage floor.(Some settups did use the Turn and Bank but I think that was either Cessna or Beech using the century autopilot as well.)
Indeed the autoflight 2 is a backup system and is powered whenever the On/Off switch on the instrument panel is on and the altimatic 3 is off.
(however the gyro in the box under the floor is always running whenever the aircraft master switch is on).
The autoflite 2 will whenever the switch is on and the altimatic 3 is off will hold the current heading. It in effect is more than a wing leveller in that
if the aircraft is upset by turbulence it will return back to the previous heading. Yes the trim switch is in effect that, a knob for trimming the airplane so that the heading does not drift
from its set heading.
In the air if you want to change heading you simply press the AP release button on the control column, turn to new heading then release, the aircraft will now follow that new heading.
The only ground check you can do is to turn on the switch and with aircraft stationary, check for no movement in the control column, If it moves you can trim this out using the trim knob. As you taxi a right turn will move column left and visa versa. (caution the control column will continue to the stop if you don't return to the initial heading) Then turn it off.

Gary

Had an Autoflite in my PA-39... during a major panel upgrade, my avionics folks convinced me to take it out... don' recall the specific reasons now, but I was under the impression that they were more trouble than they were worth.

Jim

Yes, I took mine out as well when it needed a gyro overhaul. It is a backup to the other autopilot and would make your
life easier if you had a vacuum failure in hard IFR, but in the twin there are 2 vacuum pumps and gyros usually give hints before they
pack it in, so for me it wasn't worth the extra couple of pounds of weight and costs to keep it.

Gary