I have scratched my head for some weeks to understand the dangers of setting the ALT in 1000s as we have always done, but have drawn a blank.
This is nothing new; various airlines have tried to re-invent the wheel and discovered (usually the hard way) that square wheels don't work.
What about an emergency descent? If you reach up to the altitude select knob (with it set to 100's at cruise level) and give it an anti-clockwise twist, then pull, descent will be initiated, but here is my guess at what will happen next -
- you will pull heading and speed, each in turn
- you will read the FMA, and perhaps be comforted by the "THR IDLE, OPEN DES. HDG" that you see
- you will then deploy the speedbrake
- at about this point you will go into ALT* with full speedbrake at high altitude
- you will utter #$%^&*()
The suggestion to use 100's below the transition level and 1000's above would seem to have considered the above scenario, where perhaps your company has not.
If you are cleared for FL320 and you turn the rotary selector just 1 click too far you would have entered FL330 iso FL320 when 1,000ft increments are selected. During phases of high workload, such an error could remain undetected.
Errr....whatever happened to reading the FMA?
Why not get the PNF to confirm the selection?
One would sort of hope that they do this already.......