I will try to explain the PDCS a bit, in the way I understand it, not in the one being used by rw pilots. Just keep that in mind. If a later manual renders my texts redundant, so be it. 
Manual2 offers the view on the keys and mode descriptions of that unit.
The main purpose of the Performance Data Computer System (PDCS) is to guide the pilots through the usage of correct and economic thrust values, EPR settings. There are a lot of other features as far as I can see, such as calculating VREF values or the optimal cruise FL. So feel free to explore after looking at the basic operation.
Detail text.
Quote:
The PDCS was developed jointly by Boeing and Lear Seigler in the late 1970's. It enabled EPR and ASI bugs to be set by the computer and advise on the optimum flight level, all for best fuel economy. It was trialed on two in-service aircraft, a Continental 727-200 and a Lufthansa 737-200 for nine months in 1978 with regular line crews and a flight data observer. The 737-200 showed average fuel savings of 2.95% with a 2 minute increase in trip time over an average 71 minute flight. The 727 gave a 3.94% fuel saving because of its longer sector lengths. The PDCS quickly became standard fit and many were also retrofitted. By 1982 the autothrottle had been devised and thrust levers could be automatically driven to the values specified by the PDCS.
From: http://www.b737.org.uk/fmc.htm
The unit in the sim looks like this.
You have one big Flight Mode Selector which can only be turned, a keypad with the numbers and 'submodes', some 'page' keys and a top line of three round buttons, being used to select a line on the display (SEL), clear it (CLR) and to confirm entries (ENT).
We'll leave the TURB key out, same for the ENGAGE button. The first one offers a dedicated thrust value for flying in turbulent air, maintaining structural integrity and the second one currently doesn't work. It should mainly give a status update with either being lit or not and, when pressed, should drive the EPR bugs to the computed values, same for the ASI bugs.
What are EPR bugs? Look here.
See them? One is at the default 1.00, the right one shows 2.04, which was set up manually by me.
In the current build, you will always have to set up those markers by yourself and then adjust the throttles until you match them with the needles showing the actual EPR. So those pre-set bugs are your planned values you are aiming for when operating the throttles later. I could be wrong, but setting them could be a part for the pilot not flying.
For EPR itself, look here. http://en.wikipedia.org/wiki/Engine_pressure_ratio
So how to handle the PDCS?
Well, it acts like an early FMC in a way, so you will start it up in the STBY mode and then enter your plane's values. Do do this, we have to realize that the numbers on the keypad can act in two different ways.
When entering values: numbers act as numbers.
When looking for 'submodes' and no data field is waiting for entries: numbers act corresponding to their letters, like 'LOAD'.
There are a lot of submodes and the manual2 explains them like this.
This time, we're looking for the LOAD key, which is #1. This is how the unit looks like before we press it.
You see that you are in the STANDBY mode (note the selector, it actually shows STBY too), you see the data in that mode (not much) and you see that you have 3 pages to choose from, being on the first of those 3 ('1 - 3').
To switch through the pages, use the <-PAGE or PAGE-> keys. The STANDBY mode is a passive mode, showing a status and self test but not needing any entries from your side.
Now, after pressing #1 (LOAD), the unit looks like this.
Now the page title shows LOAD, means that we're in that 'load' submode, consisting of two pages. A lot of ???? there, which represents data the PDCS doesn't know about and which can/should be entered by the pilots.
Edited:
???? means data can be entered, is needed
< is the symbol which gets placed when you press the round SEL button. Pressing it more often switches through the lines of that page. That's your active line, you can clear it with CLR and then enter values. When done, press ENT.
Example.
You want to enter the current OAT in F, press SEL until the < is in the corresponding line.
Now you want to clear the ????, which happens when you press CLR once.
The < will start flashing and the line is cleared up of ????
Now enter the current OAT, take '55'.
Then press ENT.
The flashing will stop and the value entered gets computed. See, it even knows the temp in C now. Smart unit!
So that's the way of entering data!
Edited:
To conclude:
1) enter the mode you need for entering data.
2) select the line to enter data via SEL.
3) clear the line of ???? or previous data via CLR. (don't forget that step! I often do)
4) enter the value in the correct format.
5) press ENT to confirm.
6) no flashing < ? proceed to the next line or page or leave the mode.
If you are done on that page, switch to page 2 via PAGE-> and proceed.
Make sure to enter the temps and at least the ZFW or the plane to make use of the unit. Destination altitude helps on the planning (submodes!), same does the fuel value for reserve and alternate fuel. Here's the example screen for the ZFW value.
After pressing ENT, it becomes this. See the format change? It's automated.
Edited:
Note. Currently, the PDCS operates with imperial units, not metric ones. I've therefore edited the screenshots, to give proper values. Don't mix up the units, which is easy, because the ZFW gauge in the cockpit reads kgs. 
When you are done with the LOAD submode and want to return to the other modes, make sure that no data line is active (no flashing <) and then press #1 LOAD again. First press enters the mode, second one leaves it.
You can enter any submode in that manner, so if you would like to know your current VREF, press '8 VREF once and look up the speeds for your current GW. For planning ahead, enter your estimated GW (ZFW + FOB). To leave the submode, press #8 VREF again.
Now, without explaining all the rest, lets look at the use of the unit when it comes to our takeoff.
Leave all submodes and switch the Flight Mode Selector to TO.
You will receive this screen.
Now it reads 'FULL' on top and showing that 2 pages are available, being on the first of those two, the one for a full thrust takeoff. Since we've already entered the OAT, the unit knows about it and displays our 55 F or 12 C, allowing us a max engine safe EPR value of 2.13. We could use that one and dial in 2.13 on the previously shown EPR bugs.
Note. If the ENGAGE key would work, you wouldn't have to dial in anything, but press the lit ENGAGE button and watch the bugs move. So note that 'M' on the gauges, which just shows that we've manually set the bugs to 2.13 EPR.
If you would want to go for a derated TO, if the runway length and conditions permit, the second page of that TO mode gives you lower EPR targets. You have to enter a new OAT value there. Even when entering the same one as on page 1, the EPR will give you lower recommendations as the mode itself aims for a smaller amount of thrust (a fixed percentage less), therefore reduced engine wear.
However, you can combine that one with entering higher OAT, leading to even more thrust reduction. You know, like on the FMC planes, which allow the combination of derated modes plus estimated temps. Double derate.
So lets enter some 75 F while being on page 2.
See? the EPR is lower now and you can set up that lower target to save some engine wear cycles. Note that the rw folks would calculate much more since saving engines is nice, but not being able to take off when the runway ends isn't that fortunate. Doesn't save many engines, right? 
The rest of the unit still is a lot to explore and explain, but I think you've got the basics and may therefore be able to test and use it yourself. You will often find different pages (for e.g. CLIMB), which just represent the available modes of e.g. climbing out.
Switching through the pages (4 of them for CLIMB), there's the ECON mode, which you may know from the FMC planes, and there is the one for climbing at the max climb RATE (therefore spoiling the economics a bit, but allowing a safe climb over mountain areas or just up to levels where the noise doesn't harm people that much). MANUAL is for a manual set speed target I guess and LIMIT may be.. for something else. That's the part which needs an extra manual in my eyes.
You mainly set the Flight Mode Selector to the flight phase you are in or want to plan ahead for. Then you enter the necessary data (???? fields) and receive your thrust values. To set the EPR values, move the bugs via their dials. As soon as the ENGAGE key is working, this step won't be necessary of course.
A Flight Mode always leads to and shows thrust values, the submodes then give additional data.
You can access the submodes like VREF in between, at any time, by pressing the numbers as long as no data line is active (means NO flashing <). Remember, a second press on the number ends the submode and you are back on the normal one, like CRZ.
If you get totally lost, press the RCL key, which will always set you to the main mode the Flight Mode Selector is showing. Therefore, all submodes are left behind. The RCL key also helps with getting old values back, in case you've cleared a data line and now miss the previous data.
The users with some FMC experience will have advantages of course, knowing about this or that acronym and the dependencies behind it.
Have fun exploring and keep on reporting bugs and flaws as detailed as you can. It helps the devs and the other users. There a a lot of modes for planning and looking for readings and calculations. Enjoy!
If I got something wrong, please let me know. It wasn't done intentionally, I promise. 
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PDCS tutorial, sorta (Read 43131 times)
