I'm sure you folks have noticed that the light switches on the A320 have different serrations and shapes. I've looked about for an explanation /guidance in some AICs and JAR25, but nada so far. Over to y'all bright lights !
Thanks. I too was resigned to the same conclusion but i was looking for some hard evidence. Couldn't find any in the Bus manuals. Also,there has to be some regulatory guidance on the subject...dont you think ?
Design of switches can be very significant. I used to fly Twin Otters. In the older models, the autofeather switch was exactly the same as, and right beside, the electric emergency fuel shut-off switch. The only difference was that the fuel shut-off had a red metal partition either side of it (NOT a guarded switch though).
One of our pilots, taking off at about 50% over MTOW (legally, on a ferry permit), mistook the switches and one engine went quiet shortly after take-off as he turned off the "autofeather"............ He landed back single engine, went off the edge of the runway and stopped right outside the fire station. Think it shattered the rubber compression blocks that the Twotter has on the landing gear........
By the time I started there, they had all been modified to push switchlights for the autofeather arm.
On the new Series 400 Twin Otters, there are two autofeather switches, one on each of the outboard ends of the instrument panel. One of the reasons we put them there was to eliminate exactly the risk of confusion that you identified in your post.
The two switches work in a similar manner to the switches at the top and bottom of a set of stairs - it doesn't matter whether you push the left or right switch, whenever one of the two is pushed, it changes the state of the autofeather system (to ON or OFF as the case may be), and the autofeather system status is indicated by the illuminated nomenclature within the switches and on the CAS message screen.
The picture below shows the left side autofeather switch, the right side is a mirror image.
Yes, it is common to put a ferry fuel system into a Twin Otter if you have to move it from one continent to another. The manufacturer provides an AFM supplement with all required guidance and performance data for the overweight operation.
In every case, it is necessary to obtain a special purpose flight permit for the overweight flight from the regulatory authority.
A few hours ago, I landed in Iceland, after departing Canada much earlier today - today's flight was nearly 8 hours long, and it would not have been possible without a ferry fuel system, and sufficient fuel loaded to put the aircraft over the certified MTOW. Naturally, I obtained a special purpose flight permit from the regulator of the state of registry prior to departing on this flight.
the light switches on the A320 have different serrations and shapes
I am aware of 35 light switches in the A320 cockpit - there may be more. As the saying goes, " ... if you don't know your light switches, you don't know your aircraft ..."
About the tactile feel - no written evidence, just what I was told in training. Also switches placed in order of most used to seldom used from front to back = ergonomics.
Yes, it is common to put a ferry fuel system into a Twin Otter if you have to move it from one continent to another. The manufacturer provides an AFM supplement with all required guidance and performance data for the overweight operation.
