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?

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.

> 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. 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 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.

>
> Shortly after that incident a cartoon appeared showing a refueling tech
> kneeling on the wing of an airliner with a ruler and calling out to the
> passengers inside: "How many feet in a liter?"
>

 :-)

> Not quite moot, unless you have an upscale aircraft or are willing to
> fork out a 5-digit sum to upgrade.  There are thousands of small
> aircraft with mechanical altimeters whose owners won't upgrade without a
> fight.
>
Same over here  -just that none that I've looked at had ASIs in mph, but
I suspect that has a lot to do with British naval history and their role
in pioneering navigation methods. The oldest I've had hands on was a De
Havilland Tiger Moth (FF2 basic trainer) and that for sure was using
knots and feet. It was nicer to fly than I'd been led to expect but the
vis was terrible with those wings in the way. But then again that wasn't
surprising: my Libelle has unobstructed 360 degree vision.

> Mode C transponders digitize altitude in hundreds of feet; all hardware
> and procedures in the entire North American ATC system are hard-wired
> into feet.  I shudder to think of the nightmare it would be to cut over.
>
I don't think it ever will change in aviation for just the reasons you
give. Euro/Russian/Chinese military aircraft are fully metric (MKS units)
and so are most gliders in Europe, but everything else follows ICAO
conventions and uses nautical miles, bars, knots and feet.

However, flying with a metric panel is surprisingly easy: I've done it in
Austria and Germany. In the same type of plane the ASI needle points in
the same direction and the coloured segments and yellow pips are in the
same place - only the numbers the needle points to differ. Similarly, it
was easy enough to mentally convert height. The only one that did fool me
was the vario because 2 knots (200 fpm) is only 1 m/s, so I kept
underestimating sink and flying too slowly through it because the
calibration marks are the same: in the UK they are marked 0-10 knots
while the Germans put 0-5 m/s against exactly the same marks.

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


--
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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