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blue up
12th Mar 2014, 21:27
Whilst browsing through the pages of my new 737 manual (Long, sad story involving 757 fleet reduction) I started to wonder why there is a growing mental block in my noggin with regards to circuits and switches being on, closed, off or open.
Closed circuit TV. Which bit is closed?
If a wire goes "Open circuit" then electricity flows within it so 'Open' must be tied to 'On'. But if I 'Close' a switch it also turns something 'On'. The more I think about it the more addled my grey matter becomes.

Then I looked at the 737 pressurisation system pictures. :bored:
If both systems fail you get an "AUTO FAIL" light to tell you that the afore mentioned systems have failed but if the "AUTO FAIL" AND "ALTN" light come on it is trying to tell you that the Altn system IS working.

Am I failing to grasp some hidden logic or has the world gone mad?

con-pilot
12th Mar 2014, 21:42
No it,'s not you. The world has gone mad.

Started when the FE was done away with. :{

They handled those sort of things.

Fox3WheresMyBanana
12th Mar 2014, 21:50
Not a big jet driver, but to electrical types, an open circuit is one in which no current flows, and closing a switch does let current flow. These terms derive from the days of knife switches like this (as seen in 'Frankenstein').
http://extra.listverse.com/amazon/madscientist/KnifeSwitch.jpg
This switch is 'open'

Naturally this conflicts with the plumber's use of 'open' and 'closed' for valves - open valves allow flow, etc.

http://media.web.britannica.com/eb-media/12/62712-004-3499E35D.gif

So - electrical: switch open = OFF, pipes: valve open = ON

Of course, almost all your valves are now moved by solenoids, which connect to electrical switches in the cockpit, so f#ck knows which terminology won out at Boeing.

In reality, your problem is with the manual writer who either doesn't realise this, or doesn't care about your cognitive issues, or more likely each section was written by a specialist in that area and Messrs Boeing consider it your job to understand everyone else's. You are a Sky God after all ;)

As to the indicators, I would have the Auto Fail caption to be Amber (or Red), to show an abnormal condition, and have the ALTN caption Green or Blue to show a normal state (given the Adjacent Amber).

But what do I know?

west lakes
12th Mar 2014, 21:54
If a wire goes "Open circuit" then electricity flows within it

Ah but electricity does not flow through an open circuit only a closed circuit, even if it is a "short" circuit which is a fault condition where the circuit is "shorter" than normal!

We do not actually use the terms "ON" and "OFF" in the leccy industry referring to switches, just "CLOSED" and "OPEN".

Dushan
12th Mar 2014, 21:55
If a circuit is "open" then the current cannot flow and therefore whatever is energized by it is in the "off" state.

Conversely, if the circuit is "closed", then the current flows and energizes the device, thus making it "on".

YMMV…

Shaggy Sheep Driver
12th Mar 2014, 22:06
CCTV? TV that is not broadcast. The camera and screen that displays the image are one complete 'closed' system.

'Open' circuit - a circuit which is incomplete. Current needs a 'complete' circuit to flow around. Break the circuit by 'opening' it (putting a gap in it) prevents current flow.

It's all perfectly logical.

Now, consider a railway signal (semaphore arm or colour light). It is either 'on' or 'off'. When the signal is 'on' it's at 'danger', its fallback position and the position it will revert to if the operating mechanism fails. Only when the signalman pulls it to 'off' may a train pass it.

How about magneto switches. 'Up' for 'mags live', which might seem counter-intuitive when you think of the domestic light switch which is 'down' for 'on'. But the mag switch works the same way as the light switch - when it's 'down' it completes an earth circuit to the mag's low tension coil output, disabling the mag. When it's 'up' the switch is 'off' or 'open circuit', enabling the mag to operate as its coil output is no longer tied to earth.

Again, logical.

And fail safe; if the switch drops to bits or the wire breaks, the mag is 'live' (coil output not earthed) and the engine keeps running.

Dushan
12th Mar 2014, 22:24
How about magneto switches. 'Up' for 'mags live', which might seem counter-intuitive when you think of the domestic light switch which is 'down' for 'on'. But the mag switch works the same way as the light switch - when it's 'down' it completes an earth circuit to the mag's low tension coil output, disabling the mag. When it's 'up' the switch is 'off' or 'open circuit', enabling the mag to operate as its coil output is no longer tied to earth.



Maybe in Cheshire. In NA they are up for on, and down for off. Logical.

ExSp33db1rd
12th Mar 2014, 22:29
Started when the FE was done away with

Totally agree, they also knew where the best bars and cheapest breakfasts were !

........so f#ck knows which terminology won out at Boeing.

In similar vein .......worked for a UK company that purchased a second hand US 747 freighter, and the UK CAA made us go through the US FAA manuals and change every incident of 'warning lamp' to 'warning light' ( or was it the other way around ?)

Yes, World's Gone Mad.

west lakes
12th Mar 2014, 22:30
Maybe in Cheshire. In NA they are up for on, and down for off. Logical.

Careful Dushan, you'll start another us (as in us not U.S.) vs us hamsterwheel :=:)

Shaggy Sheep Driver
12th Mar 2014, 22:40
In Cheshire we have Tiger Moths and Chippies. 'Up' for mags 'on', switch open circuit. Same in the Citabria.

If Bellanca in NA can get it right, why not NA domestic sparkies? ;)

blue up
12th Mar 2014, 22:43
So, when something is described as "having gone Open circuit" it is a broken wire rather than one that has earthed itself and popped the fuse? You learnt summat new every day!

As to the 737 thing, it's a miracle that they haven't had any accidents with such a confusing set of lights. Thank heavens this is just a single isolated issue.




PS. Lone Ranger. Full time flyer, part time airframe restorer and cowling wheeler. (No electrics stuff)

PPS. Has anyone here flown a Chrislea Super Ace?:E

west lakes
12th Mar 2014, 22:54
So, when something is described as "having gone Open circuit" it is a broken wire

By jove you've got it:ok:

rather than one that has earthed itself and popped the fuse?

That's a short circuit

tony draper
12th Mar 2014, 23:06
Just to make life more complicated when I worked as a Cable TV (RF Frequencies) ,maintenance bloke, a open circuit would have been described as a high impedance mismatch a short circuit as a low impedance mismatch when one circuit got mixed up with another it was called a interline.
:rolleyes:

Fox3WheresMyBanana
12th Mar 2014, 23:09
swap the word 'impedance' for 'resistance' and the cable circuit is the same as an electrical circuit.

tony draper
12th Mar 2014, 23:17
I know but RF can jump across gaps,anyway we blokes wi dirt under our nails just called em shorts and opens mixed up circuits crosstalk like everybody else.
:rolleyes:

BOAC
13th Mar 2014, 10:36
That's a short circuit - what, pray, is a 'long' circuit?

spekesoftly
13th Mar 2014, 11:14
It's all perfectly logical.when you think of the domestic light switch which is 'down' for 'on'.But on the domestic consumer unit all the MCBs and RCD are 'up' for 'on'.

Fox3WheresMyBanana
13th Mar 2014, 11:21
..and what about 2-way light switches on stairs? - they could be UP or DOWN for ON :eek:

I wonder what the A380 manual says about those....nightmare:E

tony draper
13th Mar 2014, 11:24
Came across key operated switches on equip bays on one job that were marked Enable for on, for the life of me I cant remember what off was marked but I dont think it was disable.
They could have saved on engraving had they just been marked off and on.
:rolleyes:

Fox3WheresMyBanana
13th Mar 2014, 11:44
Ford flipped the switch which he saw was marked "Mode Execute Ready" instead of the now old-fashioned "Access Standby" that had so long ago replaced the appallingly stone-aged "Off."
'So Long, and thanks for all the fish' - Douglas Adams

lasernigel
13th Mar 2014, 11:51
Why is down on here and off in the US. Why do they have to do everything differently???

Remember in Oman turned more things off in M60's than in Chieftains.
They even mess with MBT's!!

Fox3WheresMyBanana
13th Mar 2014, 12:07
It's just to annoy you personally Nigel!


A short history of competing systems in the electrical world.

The big battle was in the USA between Thomas Edison's DC system and George Westinghouse's AC system. The electric chair as a method of execution was developed as an advertising gimmick by Edison's company, to show how dangerous AC electricity was. The first man executed was William Kemmler, on August 6th 1890. His lawyers had argued it would be 'cruel and unusual punishment', but it was approved anyway, due largely to the influence and funds of JP Morgan (whose company now pays Tony Blair). In fact, the execution was seriously botched, took 8 minutes, and a reporter said "They would have done better using an axe."

I leave you to your own conclusions about advertising executives and Tony Blair.

lasernigel
13th Mar 2014, 12:13
I leave you to your own conclusions about advertising executives and Tony Blair.

We could only wish he'd slip into one as well. Scenes from the " Green mile" come to the forefront.

blue up
13th Mar 2014, 13:11
The Chrislea Super Ace control system...

Chrislea decided there was a better way, and threw away the rudder pedals. They settled on a system using dual-control yokes. Aileron control was similar to other yoke-operated aircraft: turn left for left bank, and right to bank right. So far so good...

Now for the elevator. Push or pull on the yoke on a Chrislea and nothing happens - though there's a rumour that some pilots actually pulled hard enough to break them off! These pilots were, predictably, unavailable for comment.

Nigd3
13th Mar 2014, 14:03
What about when the alert goes off?

Is this good or bad? :E

Blacksheep
13th Mar 2014, 14:07
- what, pray, is a 'long' circuit? One that goes all the way round?

blue up
23rd Mar 2014, 15:17
Just done week one of 737NG course. About 95% of the switches are UP=OFF and 5% UP=ON (A/T arm, F/D, A/P Disconnect....)

Is this a wind up???

Also, who decided to put Hyd B right under the Engine AI switches? I'm told that there are 2 types of 737 pilot, those who say they've put the Hyd B off, and liars.

cattletruck
23rd Mar 2014, 15:22
Is this a wind up???No, that's a rotary button. :E

thing
23rd Mar 2014, 15:28
Spammies always annoy me with their up for on switches. What happened to down for on? You think you've switched the landing light on and you switch it off. Or vice versa. I understand that the americans have their switches arse about face (although I can't remember American hotels being different to ours re light switches etc) but surely it can't be beyond the wit of aircraft importers to turn the switches around so that they work the right way. How many times have you climbed into an aircraft and all the switches are in the 'on position because the poor guy who flew it before you thought he had switched everything to the 'off' position?

Blues&twos
23rd Mar 2014, 16:53
I'm a Controls Engineer. Where I work, we have solenoid operated valves driven automatically by control systems. These control systems also monitor the position of the valves and if there is a mis-match between the desired state and the actual state the system alarms and fails safe. The monitoring is done by electrical position switches on the valve body called 'feedback switches' and they monitor both open and closed positions.

Now....pay attention....a valve can be energised (on) or de-energised (off). For a normally closed valve, on = open and off = closed, but for a normally open valve on = closed and off = open. As the feedbacks must agree with the required valve state for the system to be healthy, when the valve is on, the feedback on must be on and the off must be off. With the valve off, the off must be on and the on must be off. If both the on is on and the off is on, or the on is off and the off is off, the system will alarm. Or if the on is off and the off is on when the valve is on and similarly if the on is on and the off is off when the valve is off, there will be an alarm.

Obviously.

Blues&twos
23rd Mar 2014, 17:28
Fox3

..and what about 2-way light switches on stairs? - they could be UP or DOWN for ON

Or both at the same time!

jimtherev
23rd Mar 2014, 18:58
...except Blues&Twos reminded me of the story of the two little skunks who lived with their mummy in the forest.
One was called In because he was always out and t'other was called Out because he was always in, and mummy was called, er, mummy of course.


So, one day, mummy said to Out (who happened to be in, you understand) "Out, go out into the woods and bring In in" Because In was out as usual.


And Out went out, and almost immediately, Out came back in with In... or In came back in with Out, I forget which. So mummy asked, "Out, how did you manage so quickly, to bring In in?"
And Out replied, "Easy, mummy, you see........




"In stinkt"

Krystal n chips
23rd Mar 2014, 19:15
" How many times have you climbed into an aircraft and all the switches are in the 'on position because the poor guy who flew it before you thought he had switched everything to the 'off' position?

If the "poor guy " who flew the a/c before you hasn't got the ability and understanding to complete the shut down checks correctly, the "poor guy" in question should be keeping both feet firmly on the sodding ground and out of a cockpit, the "poor guy" in question being a pillock.

And how much time and money do you think it would cost to change all the switch positions in a cockpit, and what benefit would this bring.....short answer is a lot..... and non.

Always found Boeing cockpits perfectly logical to operate in the "UP=OFF" etc mode, when I made the transition from UK types to Boeing as an engineer.

thing
23rd Mar 2014, 19:18
I bet you're a barrel of laughs at parties.

sitigeltfel
23rd Mar 2014, 19:43
I doubt he is invited to many.

Blues&twos
23rd Mar 2014, 21:22
Ha ha! Know the feeling, Henry Crun. I also do the software programming. Usually quite easy to get the system to do the basic "user requirements"...the real pig of a job is to make sure the code doesn't ever disappear up its own arse when the users do stupid things....which they do with tedious regularity. Experience has taught me that nothing is so unlikely to happen that the users "will never do that".:ok:

owen meaney
23rd Mar 2014, 21:28
.
ELECTRICAL THEORY OF SMOKE...BY JOSEPH LUCAS
Positive ground depends upon proper circuit functioning, the transmission of negative ions by retention of the visible spectral manifestation known as "smoke". Smoke is the thing that makes electrical circuits work; we know this to be true because every time one lets the smoke out of the electrical system, it stops working. This can be verified repeatedly through empirical testing.

When, for example, the smoke escapes from an electrical component (i.e., say, a Lucas voltage regulator), it will be observed that the component stops working. The function of the wire harness is to carry the smoke from one device to another; when the wire harness "springs a leak", and lets all the smoke out of the system, nothing works afterwards. Starter motors were frowned upon in British Automobiles for some time, largely because they consume large quantities of smoke, requiring very large wires.

It has been noted that Lucas components are possibly more prone to electrical leakage than Bosch or generic Japanese electrics. Experts point out that this is because Lucas is British and all things British leak. British engines leak oil, shock absorbers, hydraulic forks and disk brakes leak fluid, British tires leak air and the British defence establishment leaks secrets...so, naturally, British electronics leak smoke.

blue up
23rd Mar 2014, 23:18
Owen. You can still buy new, genuine, Lucas Smoke.

http://www3.telus.net/bc_triumph_registry/images/Smokekit2.jpg

Shack37
23rd Mar 2014, 23:41
And then we have (had) push button switches which light when pressed. Previous logic was Green for Start and Red for Stop until Elf n Safety decided this logic was not logical. Proper logic dictates that Start should be Red as this initiates the risk condition and Green should be Stop as this is the safe condition.

Then they painted all the fire extinguishers Red so you have to get really close to identify the correct type by which time yer eyes are watering.

Windy Militant
23rd Mar 2014, 23:58
What about when the alert goes off?

Dunno about that, but the Alarm has gone off.....







They haven't made a decent record since 68 guns!* :}


*Viz circa 1990

Blues&twos
24th Mar 2014, 00:04
And then there's the UK three phase wiring colours, where blue used to be L3 but is now N, and black used to be N and is now L2. And if an extension was installed, you could have a mixture of the two schemes (labelled of course). Nice 'n' safe....:ugh:

Or you might have three browns and a blue, just to confuse the issue.

ricardian
24th Mar 2014, 00:28
And on domestic mains "up" was "off" but on high current devices "up" was "on". Quite simple

ExSp33db1rd
24th Mar 2014, 01:10
Experience has taught me that nothing is so unlikely to happen that the users "will never do that".Murphy is always with us.

oldpax
24th Mar 2014, 02:57
Old fashioned aeroplanes that used petrol in their engines had "Ignition switches".When they are OFF they are actually ON and when ON are actually OFF.The instructor at St Athans was tearing his hair out trying to explain this to a bunch of boy entrant elects!!!

VFD
24th Mar 2014, 03:26
And then there's the UK three phase wiring colours, where blue used to be L3 but is now N, and black used to be N and is now L2. And if an extension was installed, you could have a mixture of the two schemes (labelled of course). Nice 'n' safe


I deal with equipment manufactured/assembled from every country on this earth. There are multitudes of color codes (ok, colours or was it tires/tyres)


There is absolutely one thing I can tell you for sure is I have never found an electron that knew what color the insulation was on the conductor.


VFD

teeteringhead
24th Mar 2014, 20:21
Ahhhh - Lucas! When in the US of A I was told the best thing to come from Britain was MG cars, while the worst was Lucas Electrics. One recalls an American biker one once knew remarking that the reason we (the Brits) like warm beer was beacuse Joe Lucas made the fridges! :ok:

con-pilot
24th Mar 2014, 20:44
Spammies always annoy me with their up for on switches.

So then you think when the landing gear lever is in the up postion, the gear should be down and when down, up. :p


Just on a side note; I used to fly a DC-3 that flap indication had been relocated and was vertical. However, when the indicator was at the top, the flaps were full down and when at the bottom, up.

Yes, it bit me in the butt once on takeoff with a green co-pilot. Must say we didn't use much runway until it wanted to fly. :\


Oh, by the way. I've traveled all over the world and around the world, lived in England as a kid for six years and I've never encountered a light switch where down is on. Never. Well except in very primitive and backward nations. :p

Shaggy Sheep Driver
24th Mar 2014, 21:39
Ah! Joe Lucas. Known to generations of Brit car drivers and motorcyclists as 'The Prince of Darkness'.

thing
24th Mar 2014, 21:54
So then you think when the landing gear lever is in the up postion Landing gear lever? What is this landing gear lever you speak of?

I've never encountered a light switch where down is on.

To turn the dark on you put them 'up'. Any fule kno that.

con-pilot
24th Mar 2014, 21:58
Landing gear lever? What is this landing gear lever you speak of?


De thingy wot puts de wheels down.

To turn the dark on you put them 'up'. Any fule kno that.

No, that would be to turn de dark off.

Funny, never the less. :p

ExSp33db1rd
24th Mar 2014, 21:58
Oh, by the way. I've traveled all over the world and around the world, lived in England as a kid for six years and I've never encountered a light switch where down is on. Never. Well except in very primitive and backward nations.Lived in England until age 48.

Never saw a switch where On was UP - until my first visit to the USA.

When a child, most house switches protruded from the wall, not inserted, were round, brown, made of Bakelite (plastic hadn't been invented) and the little peg went down for ON.

N'est ce pas ?

Well except in very primitive and backward nations.Well, maybe you're trying to make a point ? !!

Windy Militant
24th Mar 2014, 23:20
When a child, most house switches protruded from the wall, not inserted, were round, brown, made of Bakelite (plastic hadn't been invented) and the little peg went down for ON.

Were they not tumbler switches? In which case you push the peg down, but the switch goes up! :\

con-pilot
24th Mar 2014, 23:28
Lived in England until age 48.

Never saw a switch where On was UP

Well, with me being a youngester, must have been moderized by the time I got there in 1956. ;)

I'll take your word for it, as I was so young and it was a long time ago. Plus, up until the last year and a half we were there, we lived off base. But my mother put her foot down and we moved on base, Woodbridge/Bentwaters RAF/USAF Base. I know the light switches were up for 'on' there.

But, in all the countries I have flown to, I cannot remember any up for 'off' switches.

In the 727s I flew, some had the landing switches up for on and some for off. It was a pain in the arse remembering which was which.

Now, in Austrialia and New Zealand, are the light switches up for off? Sadly have not been to those countries, yet. Still planning on going someday.

John Hill
25th Mar 2014, 00:12
Now, in Austrialia and New Zealand, are the light switches up for off?
Yes, except in installations where two or more switches control the one circuit as for example in a hallway or stairway.

con-pilot
25th Mar 2014, 00:37
Thank you, I'll try to remember that when we come down there.

Out Of Trim
25th Mar 2014, 21:09
This all sounds like the rules of Cricket!

The rules of Cricket Explained to a foreinger (Funny)
Cricket: As explained to a foreigner...


You have two sides, one out in the field and one in. Each man that's in the side that's in goes out, and when he's out he comes in and the next man goes in until he's out. When they are all out, the side that's out comes in and the side that's been in goes out and tries to get those coming in, out. Sometimes you get men still in and not out.
When a man goes out to go in, the men who are out try to get him out, and when he is out he goes in and the next man in goes out and goes in. There are two men called umpires who stay out all the time and they decide when the men who are in are out. When both sides have been in and all the men have been out, and both sides have been out twice after all the men have been in, including those who are not out, that is the end of the game

:ok:

ExSp33db1rd
25th Mar 2014, 23:06
.........but the switch goes up!but we couldn't see it, so didn't worry about it !

........and New Zealand, are the light switches up for off? The few that go up and down are down for ON, but all the ones I normally see now are little 'rocker' buttons, and yes, one presses the bottom of the button in for ON . Same logic I guess.

In the 727s I flew, some had the landing switches up for on and some for off.BOAC bought Boeing 707's new from Boeing and specified the movement of the switches up or down for ON, ( can't remember which way now, but I think down for ON ! ) then later bought some second hand ones from a USA operator, and had to remove all the switches and turn them around ( or replace them ? ) to conform with their original aircraft fleet that we were all used to, so that all the aircraft were the same.

Not light switches, but a NZ operator had 3 aircraft, two had the fuel selectors in the order Left/Right/OFF. The 3rd had them in the order Left/OFF/Right. Many died in the eventual, almost inevitable, crash of the 3rd aircraft one dark night. The Coroner said "can't pilots read ?" How many times do you get into your wife's car and turn on the windscreen wipers at the first road junction - instead of the indicators? Can't you read ?

con-pilot
25th Mar 2014, 23:15
Its current and has been for a very long time.


Not in the hotels I stay in.

ChristiaanJ
25th Mar 2014, 23:47
A "must-read" for all the participants in this thread :
Donald A. Norman - The Design of Everyday Things.

(My copy dates from 1998, so maybe not too easy to find, but worth the effort!)

tony draper
26th Mar 2014, 00:02
Someone once told me that the scans on old TV sets had to be reversed if they were to be used in Australia other wise the picture would be upside down and reversed left to right.:rolleyes:

Capot
26th Mar 2014, 00:03
I'm not sure if anyone's mentioned this, sorry if so; a Tiger Moth's magneto switches are up for ON, if that proves anything.

So, I think are any aircraft magneto switches where there are proper switches, and not some cheap rotating key arrangement combined with a switch for the starter solenoid, such as those favoured by Cessna. And Piper, if I remember correctly.

radeng
26th Mar 2014, 11:15
The argument I heard was that if you had 'up' for 'on', it was not likely to get an inadvertent 'switch on' of the equipment. Apparently in WW2, US troops given some British radio gear sent it back to stores, not realising that the switches had to be 'down' to get operation.

But what about toggle switches mounted such that the movement is in the horizontal plane? Especially when they are unmarked and reference to the instruction manual is needed to find out which is what....