Magnetic compass

[Hardy Heinlin]

Any aerobatic or fighter pilots onboard?

Minus 1 g. No barrel roll. Wings level with the blue side down.

Would the whiskey compass still swim or would it touch the case?


Cheers,

|-|ardy

[Qavion]

I'd order one from stores and experiment with it, if it didn't come so well-packed : P

Maybe there are some clues in its construction. I'll look for a "breakdown" diagram.

Cheers.
Q>

[Shiv Mathur]

Is it the same sort of thing as this ?


(I'm not sure, because on the old forum it seems to have been settled that there is some sort of pivot as well). http://744.hoppie.nl/forum.cgi/noframes/read/19205

If it IS the same, then it should be easy (and cheap) to get one of these keychains and experiment.

Shiv

[Simpilot767]

As you can see on the outline, even the whiskey compass is mounted
mechanically at the bottom of the "rose", so there are bank-limits where
it stops working. And furthermore it shows that the rose must be heavier
than alcohol. So i think it will touch the case...
I think if someone tends to fly a complete route by inverted flight, he has to
mount a second compass upside down  :mrgreen:

Timo

PS: Please excuse this "huge" picture, but there wasn´t any chance to upload an attachement when posting a reply. Otherwise i had downsized it...

[Hardy Heinlin]

Hi Timo,

as far as I know, the compass body's center of gravity lies lower than its jewel bearing. The max dip angle is, so I learned, ca. 18 degrees. But since this is a tangent function, the same freedom is theoretically also available when adding 180 degrees. The dip angle just must not approach 90 (or 270).


Cheers,

|-|ardy

[paulstory]

I have one in my RV8.  I could try, but I have a carbed engine and -1g for more than a second or two makes the fan out front stop.

[Qavion]

At every gate in Sydney, the compasses on our 744's tilt towards the south.

I was concerned about interference from aerobridges and terminal buildings, but whatever the position of the aircraft, the compasses still show the same behaviour.

Rgds.
Q>

[Blake H]

Hi guys,

I am installing a dimmer control to the compass light. Is it the overhead/cb dimmer control? Also in my technical manual there is no mention of the landing gear panel and upper Eicas panel dimmer control. The standby instruments is connected to the captain panel dimmer.

FYI. The compass I have is flight illusion.
 
Cheers, Blake.

[Hardy Heinlin]

If you work with PSX, you don't need to care about these internal 744 systems. The knob for the compass lighting is airline specific (can be selected in PSX), it can be the Captain's panel light pot (UAL) or the OVHD pot. PSX needs to read all your pot angles anyway. Out come the individual voltage values (per TCP/IP text messages) for various groups of flight deck lamps. These voltages also depend on the aircraft's AC busses, batteries, failures etc. which is all modelled inside the PSX software, you can't simulate these effects if you connect your knobs directly to your lamps.


Cheers,

|-|ardy

[the mad hatter]

I have the whiskey compass from the 747-400, not sure how I am going to get it to function as yet, but I can take it out and roll it about and revert back, in a tactical aircraft it the compass plays catch up.

@ Blake.. there is a whole lot of (hard) dimmer controls in the aircraft.. might be best to source the dimmer boxes at the base of the MIP, and then aft of the cabinets where the push pull tray is on the P2 position the main box is there.. does that help?

[Blake H]

For me I am going to have my own controller box with 10k pot. The globes will be voltage variable to control light intensity. Controller board will need to be made. I will use relays assigned to PSX to their respective dc bus. For power on/off situations. Google potentiometers controlling voltage circuits. Might be useful. Yes I do have the controller box, this will not be used.


That is why I need to know the above MIP and compass respective controller???


http://www.flightillusion.com/index.php?page=shop.product_details&flypage=ilvm_fly_admirable.tpl&product_id=48&category_id=7&option=com_virtuemart&Itemid=58.

Take your wet compass out and replace with above. I removed the casing of the flight illusion and replaced with the 747s compass case. Works a treat moving compass.  

[Hardy Heinlin]

I will use relays assigned to PSX to their respective dc bus. For power on/off situations.

There are also fixed-dim situations, not only on/off. And the power source may be AC bus 4 or the Main Standby Bus in this special case. It's your decision, but if you really want to use PSX, your current plan will cause a lot more work than necessary. You double your work by implementing something that is already available -- at PSX's output which you want to assign to your system anyway.

The output from PSX for your compass light is a value from 0 to 1000. It's computed based on dozens of aircraft specific parameters that are beyond the control of your flight deck knob. If you check the output for 0 and non-zero, well, OK, then you have an on/off information. But no dim information. When a certain bus is unpowered, the value could be fixed at 430 while your knob should be ineffective (if it's modelled realistically). So, all you'd have to do is simply feed your light system by the complete information (0-1000), not only by 0/non-zero mixed by values directly from your knob. The knob output should go into PSX, nowhere else. Vice versa, these things may also influence the battery discharging in the PSX model. If you skip all this, you'll have an expensive 100% complete hardware cockpit with systems working only at 10% realism :-)

[Jeroen Hoppenbrouwers]

Waahaaa, this was the killer remark, Hardy.

"By turning up the lights you discharge the battery faster."

This clearly indicates how much already went into PSX and how little a flight deck builder should try to outsmart it by adding bypass circuits.

Probably this summarizes the PSX flight deck builder's bible:

1. Every bit of input hardware feeds just and only into PSX.
2. Every bit of output hardware gets its commands just and only from PSX.

A light buld isn't controlled by a relay plus a bus plus a dimmer, unlike the real aircraft. It is controlled just by a dimmer. PSX controls the dimmer for you and includes everything relevant.


Jeroen

[Hardy Heinlin]

Oops, I have to be more precise. In this special case the knob is inoperative and the dimmer dims to fixed 12v while it gets 28v or less from the discharging battery.

But, aside from that, the brightness knobs do influence the amperages and voltages in the aircaft's electrical system. PSX really needs the output from the pot.


Cheers,

|-|ardy

[Blake H]

Wow! Never thought PSX would go to that extent. That is very cool .

I might have to do some thinking, I might have to get the dimmer control boxes out.

[the mad hatter]

If you skip all this, you'll have an expensive 100% complete hardware cockpit with systems working only at 10% realism :

I finally understand this aspect as I had to dispose of my first effort because I removed,lost, gave away, sold, crushed, and or cut items I did not think important

[Jeroen Hoppenbrouwers]

There is one more aspect to think of in terms of keeping auxiliary equipment such as dimmer control boxes around.

This kind of stuff is aerospace industry material. Not only is it very expensive and/or hard to find, it also tends not to interface with anything else. You may find yourself having to re-implement a full aircraft system just to get data to the dimmer boxes. In such a case, it may be worth to ditch the dimmers and replace them by straightforward (industrial, but not aerospace) voltage-controlled or USB-controlled dimmers.

Also, long-term replaceability is an issue. Parts will break and if spares are going to be a real problem, you are better off trying to get something else instead.

Now next topic is whether you want to go with DMX512  :shock:


Jeroen

[Hardy Heinlin]

Build a small museum next to the sim room. These old things have a long history, have flown millions of miles, they look fascinating when they are aesthetically placed in a well illuminated showcase.

[the mad hatter]

A well made point Jeroen,

 But the questions is when will a particular item fail ?(we don't know).. and determining which items can be exchanged out for ease of build and which items one should retain. It is not until one opens the deck up to see that firstly it was never designed to be taken apart and that you realise  that you don't have a clue what this part does.( some days I just run and hide) it can be that scary.. plus being in the States items are easier to come by than for our friends in other countries like Austrailia, Asia and alike..  ILS and other systems for sourcing are almost palatable

I guess it comes down to these things..
A) Are we reverse engineering the aircraft.
B) Building simulators
C) Emulating the simulator.
D) What is the intended use/expectation from the build  
E) Budgets

how ever if there was a keep throw list that would help maybe I should start one :-)
\\
B

@ Mr Hardy...  Excellent point sir and have taken that to hand mainly with the panels radios etc etc from the 300 I have and I will be keeping the flight engineer's station fully populated as a display just lighted up no real world functions

[Jeroen Hoppenbrouwers]

I now realize how much we actually should borrow, technology-wise, from the performance (stage) industry. Audio is already there big time inside PSX, John is constructing a mixer interface, but we don't do MIDI or anything else. Lighting and stage equipment is mainly DMX. There are huge markets for this gear and lots of it is readily available in your local stage shop. I spend many hours browsing through these stores in Miami -- brilliant to see what kit you can get these days, and most is interfaced to a PC in some way.


Jeroen