Auto pilot disconnect

[mog]

Hi All,
 I have been in discussion with some mates of mine and we can't agree on a facility that I believe exists on the DC9, I believe that if the A/C is in flight under Auto pilot control and the Pilot for some reason pushes or pulls the Control Column the Auto pilot will disconnect, is this true? It is my belief that it's true of the MD80 series, but does the truth exist also for the DC9?

Beers

mog

[aerofoto - HJG Admin]

on the DC9, I believe that if the A/C is in flight under Auto pilot control and the Pilot for some reason pushes or pulls the Control Column the Auto pilot will disconnect, is this true? It is my belief that it's true of the MD80 series, but does the truth exist also for the DC9?

I think that "may" be the case (per a certain amount of physical pressure being appliud to the yoke) .... but .... I don´t say it is the case.

Jim .... only if he wishes to .... might be the best person/authority to provide "the definitive" answer.

The AP´s in our simulations/panels don´t do that though .... and nor will be re-engineered to be able to do so even if they´re supposed to

The closest (to your descroption) some of our panels offer is a "CWS" mode (DC-10 and L-1011 panels definitely .... I can´t remember if our DC-9´s offer this feature or not .... other things on my mind at the moment and time´s limited) .... which results in partial AP engagement that allows manual control input in relation to both pitch and bank .... but .... without causing the AP to disengage.

The only simulation I´m aware of that attempted "something like what you´re querying" is the TM B737-200 panel .... but .... I found it´s being able to do this also resulted in the AP just "letting go" sometimes (and also incurring a run away trim too) without any control input at all ever having been applied and without any warning too. I recall this issue being mentioned within the AVSIM hosted TM support forum .... and that it required a fully licensed FSUIPC verion in order to be corrected.

Mark C
BOG/CO

[mog]

Thanks Mark, The early 737-200 had an odd Autopilot, I'm referring to the old Sperry 77 set up, to climb or dive was achieved by pushing or pulling the control column, the rate of descent was also controlled thus, once the desired altitude was achieved the Autopilot selector was set to Alt Hold and a further switch on the coaming selected to Alt Hold and Bob's your fathers brother as they say, I think, but I'm not sure, the 737 Classic had a Torque motor which aside from providing certain inputs to the Autopilot system also sensed pilots inputs and if they exceeded a certain figure (magnitude) would disconnect the Autopilot, there is I believe a similar set up in the MD80, (but I could be totally wrong). The CWS (Control Wheel Steering) mode as I understand it, rendered the Autopilot to basic pitch and roll mode hold, the altitude and direction being controlled by the pilot.
To me it makes sense (I'm easily swayed!) Consider this, an A/C is flying along fat dumb and happy in Autopilot, and the Pilot and Co-pilot have just finished the required spilling of the coffee onto the centre console when out of the clouds, in front of them, comes a flock of birds (feathered type), or heaven forbid another A/C, the Pilot (they're always the quickest?) grabs the spectacles! no time to fumble for the disconnect button! and pushes the column forward, the Autopilot disconnects (and bleats it's protest!) thus ensuring that there are no opposing forces on the controls in this emergency.
What do you think?

Beers

mog

[aerofoto - HJG Admin]

The early 737-200 had an odd Autopilot, I'm referring to the old Sperry 77 set up, to climb or dive was achieved by pushing or pulling the control column, the rate of descent was also controlled thus, once the desired altitude was achieved the Autopilot selector was set to Alt Hold and a further switch on the coaming selected to Alt Hold

That´s precisely the B737-200 AP version modeled by Richard PROBST .... as was selected by TM.

It´s also precisely how it was intended to be used and perform in FS too .... albeit that with the AP engineered this way, I (and a number of others too) found this simulation had a tendancy to commence a sudden and uncommanded descent, that could result in a dive, and which couldn´t be corrected unless the AP was manually disengaged and reset .... and sometimes even this sort of remedial action wouldn´t arrest the sitution either.

Without "licensed FSUIPC influence" it seems it wasn´t possible to correct this unwanted yoke/AP anomally with this particular panel.

The CWS (Control Wheel Steering) mode as I understand it, rendered the Autopilot to basic pitch and roll mode hold, the altitude and direction being controlled by the pilot.

That´s my understanding of AP "CWS" mode too .... and is how we´ve engineered it within the DC-10 and L-1011 panels we offer.

As I recall .... the AP on early L-1011´s could be disengaged per so many pounds of pressure being applied to the yoke .... and which was (I understand) "one of" the causes of the 1972 EAL 401 prang in the MIA Everglades. I think that paerticular system was modified somewhat after this prang.

As for the rest .... I prefer to defer to someome like Jim for an opinion .... "if" he cares to offer one

Mark C
BOG/CO

[mog]

Thanks for the response Mark, hopefully Jim will kick in with some views.

Beers

mog