Cockpit assessment, switch direction

[Pilot DAR]

Yesterday's flight test training question was:

We are probably in agreement that an up motion is "on" for switches in the cockpit, where they are located on vertical surfaces. This is common for household and commercial building switches in North America (though not universal worldwide - which might explain why I'm sometimes in the dark in the UK and Hong Kong).

Similarly, if they are on a [lower] horizonal surface, which faces up, forward seems to universally be "on".

However, for switches on overhead panels, which way is best for the "on" position? I am aware that there is Boeing heritage that forward is to be "on". Such an arrangement fits in well, if the engine controls are also overhead, as they are required to be "control forward" for more power (on). The switch issue can be a little conflicting though, when a portion of the overhead panel is near vertical which prevails?

I have also seen a concept where on is the motion of the hand in an arc from lower to higher (meaning aft would be on, for overhead panels).

What is the experience of the group, as to what to accept in this regard?

[clunckdriver]

Simple, everthing "forward" for take of, ie, thrust levers and switches, and "up", or in the case of switch lights,"in". Please get this through to Airbus!

[Daniel_11000]

For overhead switches, I know that a western standard states that the positions for ON and OFF generally depend upon the tilt of the overhead panel itself : If the panel is 'vertical', ON etc should be 'UP', if the panel is 'horozontal' it should be 'FWD' , and both seem logical to me . I do not remember the angle at which the 'ON' position transition from 'UP' to 'FWD', I will make a search and let you know ( if I found it ...)
Daniel

[Shawn Coyle]

Russian standard is that back is on. When the KA-32 was to be certified in Canada, the switches had to be changed to forward is on. When the Russians certified one of the Challenger models, they insisted that the overhead switches be changed to aft is on.
Main point is to be consistent within the type within the country of operation.

[aviatorhi]

However it's labeled.

You don't happen to be ex-TWA do you?

[PEI_3721]

Pilot DAR. From fallible memory, I believe that the general design principles for switch direction are ‘Forward, Up, and Back for On’. The direction flows in an arc from the ‘at rest’ hand location, forward then up the front panel, and thus logically back for the overhead as you describe.
IIRC this convention was discussed by SAE (ARP 1402), but I am unable to locate the document. The sketch below originates from circa 1980 and may relate to the SAE work.

The BAe146/Avro RJ, although with rocker switches, follows this logic; also the few toggle switches in the A300 overhead panel.

However, a quick web search (MIL-HDBK-759C 31 July 1995 ‘Handbook for human engineering design guidelines’) indicates that the overhead ‘On’ direction should be forward.
Other generalised HF references discuss the switch location w.r.t. the vertical position above design eye location, and the slope of the overhead panel.

http://i56.tinypic.com/33cmz5z.jpg

[peeush]

Sense of operation differs world wide and it would be impossible to reach a consensus in this case (consider direction of rotors turning in helicopters across the globe !).

However, two factors may influence the direction of operation:-

1. Convenience of the crew. This would entail consideration of crew's orientation in terms of switch 'sense' that the machine is going to be operated. Necessarily this would relate to the 'switch sense' prevalent in that part of the world. This would positively add to cockpit adaptability of the crew and reduce possibility of incorrect operation of switches in 'Hazy' cockpit scenarios (Think of emergencies in air).

2. Inadvertent operation of the system. The system to which the switch relates must not be inadvertently operated due to interference with crew clothing/cluttered cockpit/Real estate crunch on the panel etc. Say for example a switch located too close the volume knob of the radio may get activated even when the crew actually doesn't want it. Here, it may be prudent to consider (if the switch can't be relocated) better of the two options....inadvertent 'ON' or 'OFF'-- that would be acceptable.

Finally, I don't really think that one half of the world would agree to the other half whatever the arguments may be.

Thanks for the read.

[Denti]

I know that lufty changed the switch direction of some (if not most) overhead panel switches for its 737 as they did not comply with a local industry norm for switches. Makes for a quite confusing sim session if you use some of their simulators. Anyway, over here the light switches in houses are build the other way round than in the US, switch them down means on, and the other way round. And yes, that is standardized and of course regulated...

[Pilot DAR]

Interestingly, I was test flying a DHC-6-300 Twin Otter today. The overhead switches were forward for "on". My company pilot explained to me that when he flew the DHC-6-320 Australian version, the overhead switches were the other way around. No wonder the Auzzies insist on type endorsements!

I was amused to find that this particular Twin Otter had an avionics master, and project power switch, both of which were on the vertical instrument panel in front of me, and were down for "on". I was not being asked to approve these. Good thing 'cause I would not have!

[Rick777]

When I was flying freight we had a bunch of old 707s. Some of the switches worked one way and some the other since they got the planes from all over the world. No two alike really. Made it interesting flying mostly at night and having a lot of the labels worn off.