NavList:

Who's next? Can aviation get over the nautical mile and knots addiction or is the inertia of the "installed base" simply overwhelming?

In aviation a slope of 1° over 1 NM is extremely close to 100 ft difference in altitude

That's one of the most important and widely used mental computations formulae (there are others ...) in Aviation.

So I am not sure degrees, NM are going to be dumped overnight in Aviation.

When flying [modern] Boeing or Airbus Aircraft ( B757's or A340's) I extensively used the on-board computer results, but especially during descents - which I have found to be quite challenging at times - almost up to every minute of time I nonetheless did "check" my descent.

It took me only a few seconds of time: was I "low" or "high" from the the published descent plan ?

The first case is easy to solve: if "low" simply increase thrust.

Solving the second case - being "high" can sometimes become a nightmare if you become aware of it too late while being already stuck at idle thrust, with some times speed brakes fully extended.

So, quite frequently did I perform my mental checks on A/C vertical positions relatively to the descent plan. The on-board computer did indicate altitude "errors" in feet with up to 4 or 5 published digits in some cases (e.g 12,700 ft high). But it was not always fully reliable in some cases ...

My mental results gave me only 2 significant digits, but at least these first 2 digits were [almost] 100% reliable.

There were Airports known for incorrect computer initial slope results during early and intermediate descent (e.g. OSDI / DAM when flying B757's arriving from the North-East).

The "1° at one mile equates 100 ft" rule saved my day more than once, and some of my nights too  ...

Kermit