On 2017-04-04, Martin Gregorie  wrote:

> On Mon, 03 Apr 2017 21:51:58 +0000, Charlie Gibbs wrote:
>
>> And I don't know whether an STC even exists to let you replace your
>> airspeed indicator with one calibrated in knots.  I started looking into
>> it once, but quickly retreated.  At least most such indicators have an
>> inner scale in knots, which comes in handy for navigation -
>> but all the numbers in the POH are in miles per hour, so you're stuck
>> there.
>
> Doesn't that depend on what's listed as essential equipment in the POH?

It's more a matter of V speeds, etc.

> However, from what I've seen in the chatter on red.aviation.soaring I'm
> certain you're right in thinking that you've got to have mph. The FAA
> seems a lot more draconian over that sort of thing than out CAA.

It's the amount of paperwork required for a seemingly simple modification
that's the main stumbling block.

>> Inches of mercury over here.  One slight compensation is that one inch
>> of mercury equals about 1000 feet at lower altitudes, which is a handy
>> rule of thumb.
>
> Wondered about that, and whether that would be different at Internationa|
> Airports in the USA.

Nope.  Inches of mercury everywhere.

>                      I'd have a hard time with that, since my altimeter
> uses millibars and even my local controlled airfield's tower asks for
> "your height with 1016 set" if that's his reading when I talk to him as
> I'm passing by.

I have seen some altimeters with two scales: inches and millibars.
I think your typical glass cockpit (again, for the well-heeled)
will switch with the push of a button.  But most altimeters here
can be set strictly by inches.

Interesting thought: on powered planes over there with constant-speed
props, are the manifold pressure gauges marked in inches of mercury?
They are here - as well as the appropriate places in the POH.

> I know there are other things I'd expect to differ too, e.g. almost all
> non-US airliners will be doing Mode S with 1090ES extended squitters and
> I wouldn't expect any of them to have UAT systems fitted.

As of 2020, ADS-B (either Mode S with 1090ES or UAT) will be mandatory
for all aircraft operating in U.S. airspace classes A, B, and C, plus
class E above 10,000 feet.

> In fact, I find it harder to fly a familiar glider type in the US because
> your ASIs are upside down.

:-)  I wonder what Australians have...

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