Standby altimeter....

[fescalised portion]

I am involved in importing a Learjet from Europe to the USA. On reviewing the equipment list for the airplane, I noticed that the standby altimeter is calibrated in millibars so I have arranged to have it changed out for a standard one and recertified/tested before it leaves the EU. To cut a long story short, I was asked if the flight crew could just use the metric one and use a conversion chart from the POH or AFM every time that they need to change the altimeter setting (the primary displays are switchable between HG and MB, so no problem there). Of course this was all to save money, but I stated the reasons that I thought it was a necessity to get rectified and I won the battle. I have never come across an aircraft in that configuration before and I am just curious what other professionals out there think if they were asked to fly an aircraft (for hire) configured like that. I have my own, to me obvious reasons why it is undesirable, just looking for your thoughts and comments.....

[Dan Winterland]

The SI unit of pressure is the hectopascal, so therefore the altimeter in mb is technically the 'Standard' one.

In my experience, there is no problem with using an altimeter in a different pressure setting. In all three of my employers, we have used conversion tables. An with my present employer, it's OK to take the conversion from the selection of mb to ins on the EFIS switching panel.

But of course, it depends on your regulatory authority's rules.

[BOAC]

If it is 'for hire' I suspect it will not meet commercial certification requirements without a dual function instrument..Do be careful when you refer to a 'metric one' - that is quite a different thing. In terms of practical operations, I would have thought that setting the millibar/HP scale by switching the one of the main altimeters to mb/hp momentarily. would have been sufficient.

[Intruder]

There is no relief in our DDG for the IN/HPA switch, so I have to assume the dual function is required.

The only relief is for the Standby Altimeter Vibrator, and that requires VMC at departure and arrival airports...