How does a real-world DC-10 autopilot work?

[George Carty - HJG]

Since version 1.0 of the DC-10 panels has now been released at HJG, I feel I can now make public a query which I have regarding the functionality of the DC-10's autopilot, which I would like answered so that the autopilot on the version 2.0 panels could be programmed to work authentically. (I don't even think the payware Commercial Level Simulations DC-10 panel has simulated it quite right...)

I've already found a very useful document at www.scribd.com/doc/32605430/McDonnell-Douglas-DC-10-40-Auto-Flight , but it doesn't give me all the information I'd need -- my questions for now are:

1) Can you tell what state the autopilot is in just by looking at the autopilot itself (with buttons lit up, and/or with knobs pulled out for SPD, ALT SEL or HDG SEL modes), or do you have to look at the annunciator lights above the ADI for this purpose?

2) Apparently (according to what I've read), merely moving the vertical speed wheel will select VS mode. Since the wheel moves according to the aircraft's actual vertical speed when VS mode is not engaged, how does the mechanism determine if the wheel has been moved manually?

3) Once VS mode is engaged, is there any way of restoring manual (or CWS -- I presume the autopilot in CMD mode defaults to CWS behaviour if no other mode is selected) pitch control, without affecting whichever bank/turn mode is currently selected?

4) Is it possible to hold the current altitude by pushing the altitude select knob in? I read this in the documentation for a DC-10 add-on for the FlightGear flight simulation program, but there's nothing mentioned about this in the document referenced above, only that it is possible to hold the current heading by pushing in the heading select knob.

Hope someone here can help,

George

[christrott]

1) I can't tell you for certain, but I know when pushed the buttons sit in more than when "out". As they are back lighted, this increases the brightness of the button substantially, but I couldn't tell (and this is remembering what I did 12 years ago when I did the research and photos for Erick & SGA) if they lit up if the back light was off. The only reason for this was I didn't want to mess with much since the airplane was powered up (with the APU running).

2) It uses a spring/resistive sensor similar to how the rest of the system works to disengage the autopilot and autothrottle when pressure is applied to the yoke or throttles respectively.

I can't answer #3 or #4 with any level of confidence, but I believe that FlightGear was incorrect. McDonnell Douglas had great success with this style of autoflight system with the DC-9 and the DC-8, so it wouldn't make sense to change it. Under the prior aircraft, centering the VS wheel is what allowed you to hold an altitude other than the preselected one, so it would make sense, especially with the wheel markings, that rotating the VS wheel to "Hold Altitude" would enter Altitude Hold. As the preselect uses a mechanical system, it would add a significant level of complexity to the system to add the required mechanical motors and logic systems to allow the preselect to be reset to the current altitude with a push of the button when another, simpler way was already available.

[aerofoto - HJG Admin]

I think too .... from my own memory of both AIR NEW ZEALAND and UTA DC10-30's ....

When AP modes such .... as HDG, NAV, ALT, IAS/MACH in particular ... were selected, then, once acquired, these would also illuminate a corresponding lamp (quite prominent lamps) located in cluster/line of 4 just above the AI gauge on the main panel.

I think the MD11 also featured something similar too.

I also seem to recall .... that it took a wee while for the gyros to stabilize sufficiently, after departure, and before the AP could be could assume full authority and prior to which the aircraft needed to be hand flown, or, AP CWS mode employed .... rather than just flicking the AP paddle switch/ches "ON" and then having instant AP authority like we're accustomed to doing in most simulations

Those are some of my own technical memories of the DC10 .... but for me .... that was all 24 years ago .... when I did my last DC10 flights in the jump seat with UTA FRENCH AIRLINES.

I shot this one evening during one such flight across the Pacific ....



UTA DC10-30 F-BTDB. En route between Auckland/New Zealand and Papeete/Tahiti, July 10th 1989. Under the command of captain Philippe BARLOY, with F/O Josie CONROY, and F/E Serge SPICHER (out of the picture)

Mark C
AKL/NZ

[Mike Monce - HJG]

Great shot, Mark. Do my eyes deceive me or are those "ribbon" engine gauges on that panel instead of round steam gauges? That photo could serve as a basis for a new panel.

My perfect sim has both a great FDE, AND a fully operational panel/systems. If it takes me 20 minutes to get the plane going from cold and dark to taxi, I'm happy I know, kinda crazy.


Mike

[walterleo]

Hi Mike:

Then a Santa must fulfil a wish of mine: A FE panel for the DC-10 similar + to the L 1011 one. But Mike meanwhile you can try the PT Tu-154M, record from cold and dark to T.O.: around 20 minutes (navigation settings included) to engine running around 10 minutes. AND no shortcut (ctrl-E) available.

Kind regards

Walter

[aerofoto - HJG Admin]

Do my eyes deceive me or are those "ribbon" engine gauges on that panel instead of round steam gauges?

YEAH .... those are tape instruments .... similar to, but also different from, those represented in 2 of our current L1011 panel offerings.

Among DC10's .... this was a very rare engine instrumrent configuration.

All 8 AIR NEW ZEALAND DC10's featured it .... as did those operated hy the KSSU GROUP (KLM, SAS, SWISSAIR, and UTA) too.

Some crews around the world did't like this sort of configuration much .... since it could, apparently, in some situations become difficult to read quickly.

When AIR NEW ZEALAND transitioned from the DC10-30 to the B747-200B during 1981 we also fitted this same engine instrument configuration to each of our 5 aircraft (much to the disgust of BOEING .... I believe) .... simply because our crews (those whom transitioned to the B747) has already vbecome very well acquqainted/accustomed to this particular gauge standard over their past 8 years of DC10 operations.

When AIR NEW ZEALAND eventually sold it entire B747-200B fleet to VIRGIN ATLANTIC during 1999 .... apart from reconfiguring these aircraft to their own specific requirments, one of the first things they/VIRGIN did was rip out the original tape engine instruments and replace these with the traditional round analogue type gauge standard.

Mark C
AKL/NZ

[George Carty - HJG]

Would I also be correct in thinking that on a real-world DC-10 autopilot you cannot deactivate the autopilot's current mode by pressing the same button again, but only by switching to a different mode or disengaging the autopilot completely?

[aerofoto - HJG Admin]

"POSSIBLY" George .... maybe as its own (sort of) built-in safety feature .... maybe to guard against inadvertant disengagesw of a particular mode.

I can't verify this though .... basically because all/most of of the pilots whom flew DC-10's (here .... in NZ) are/have "left the launching pad and shot into space/died by now.

Did you pick up the DC-10 manual extracts I uploaded for you .... complements of AIR NEW ZEALAND ?

I think the AP, and it's many modes, and functions were well covered within that particular data.

Let me know (per PM) if you haven't got/recieved that data

Mark C
AKL/NZ

[walterleo]

Hi Mark:

Those ex DC-10 pilots still living seem to have flown various other airplanes afterwards, so their memories are blurred by the experience of operating other systems. At least a friend who has flown B 757 and B 767 after the DC-10 told me, he is shure he would remember everything sitting in a real cockpit, but without that he doesnt want to give false answers.
So for simulation purposes one has to stick to the published manuals. But in other historic oriented enterprises one has to accept shortcomings also. For centuries history didnt know where the corpses of Varus legions rested even as it was the worst military catastrophe of the Roman Empire; where all the Spanish caravelles with their treasures exactly went down...
I myself am searching for the moment the take-off and landing tables for the real Tu-124 as no real manual for that airplane can be found in the NET. For the TU-104, Tu-134, Tu-154 IL 18 and IL 62 there are manuals some even in English or German available. So I think I will testfly the simulation and make my own tables FOR THE SIMULATION.

There is a discussion around the issues here:

www.airliners.net/aviation-forums/tech_ops/read.main/191792/

May be you know it already...if not it sheds some light on the issue.

Kind regards

Walter

[Nathan Ford - HJG]

Am not home at the moment, but I have a cockpit video on the DC10-30 and they explain how everything works. I'm pretty sure they go into detail about the autopilot. They also detail the engineer's panel and overhead.

Will check it out tomorrow and let you know.

Cheers,

Nathan

[aerofoto - HJG Admin]

Those ex DC-10 pilots still living seem to have flown various other airplanes afterwards, so their memories are blurred by the experience of operating other systems.

It's called/pilots call that "AUTOMATIC DUMP" Walter

However well conversaent one was with the operation of a particular aeroplane is usually of absolutely no benefit to them/pilots when they transition to there next aeroplane.

We've often taklked about this, among retuired aircrew, here in AKL, and over a few drinks

I have a cockpit video on the DC10-30 and they explain how everything works

Drop George a PM .... if you care to Nathan .... if you have the link and feel it might help.

I have (compliments of AIR NEW ZEALAND) an extensive selection of extracts from one of our old DC-10-30 manuals (and which i'm sure includes an AP section) .... but .... I'm not sure if George has received the file/s I prepared for him.

The more information .... then the better .... of course

Mark C
AKL/NZ

[George Carty - HJG]

Yes I got your Air New Zealand manuals and have just been having a look at them.

Thanks,

George

[George Carty - HJG]

OK, I've established from the Air New Zealand manual that a dual autoland on the DC-10 involved engaging the second autopilot channel once autoland mode is selected (which the other manual I'd been reading didn't make clear, as it suggested that each channel actually had 2 autopilots the second of which is used only for autoland), but I'm still unsure as to whether there are any other non-obvious "gotchas".

Taking the L-1011 panel as an example, such would be the autopilot VOR selector moving automatically to SPLIT when ILS or autoland mode is selected, or the fact that autoland is cancelled by disengaging the autopilot or by switching off both flight directors...

George

[walterleo]

"However well conversaent one was with the operation of a particular aeroplane is usually of absolutely no benefit to them/pilots when they transition to there next aeroplane."

Yes to my freind the BOEING people while transitioning to the B 767 told: "Forget everthing you have done in other airplanes!".

Kind regards

Walter

[Nathan Ford - HJG]

Sorry guys, the video isn't going to be of any help. The captain didn't talk much about the autopilot and skipped right over the vs.
What I did notice, after selecting an altitude, they "pull" on the altitude selector knob to enter the new altitude for alt capture.
Immediately after takeoff, the captain asked for IAS and used that to reference the flight director for pitch information.
On a visual approach, the f/o used CWS down to 500 feet and then turned the A/T off at 100 feet!

I can only assume that after VS mode has been selected, pressing IAS will turn off VS and go back to using pitch for the climb/ descent.

As the crew didn't level off at any intermediate altitudes, I couldn't see if they "pressed" the ALT button to level off.

The Autopilot buttons where dimly lit for the night take offs and where brighter when pressed.

Cheers,

Nathan.