why MPH instead of knots? - Page 3

Desert Rat · #21 03-20-2023, 01:15 PM

Quote:

Originally Posted by gasman

The irony of THIS statement is it is actually (rounded off) 174 kts. not 170...

hey, I said "about"

gasman · #22 03-20-2023, 01:28 PM

Quote:

Originally Posted by Desert Rat

hey, I said "about"

I did see that. That's why I said "rounded off" to keep the fire away from me too...

Scott Hersha · #23 03-20-2023, 02:19 PM

Quote:

Originally Posted by Mel

I fly from the left side and have everything set up in knots. My Wife flies from the right seat and has her side set up in MPH.

She goes faster than I do but has farther to go, so we both get there about the same time!

Ha Ha!! Good one Mel. I’m going to use that one too. It’ll make her feel good

gmcjetpilot · #24 03-20-2023, 02:32 PM

As long as you use consistent units it does not matter, MPH, KTS, KPH, MACH, Speed of light or Furlongs Per Fortnight.

Obviously MPH sounds better as it is 15% more than Knots. So 190 knots is plenty fast for a single engine sky scooter. However 220 MPH (218.5 MPH rounded up) sounds better doesn't it? Being experimental (EAB) planes we can use what units we want. The conversion is easy to make either way.

Back in the day all planes were in MPH before 1969. After 1969 they progressively transitioned to knots/hr for airspeed and knots for distance.

Mile or MPH is an archaic unit based on the British Imperial units. WIKI: "The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 English feet, or 1,760 yards."

Why knots? It is way easier to do navigation for boats and planes that fly in reference to Lat and Long. WIKI "The nautical mile is based on the Earth's longitude and latitude coordinates, with one nautical mile equaling one minute of latitude.

gasman · #25 03-20-2023, 02:46 PM

They didn't name the Mooney 201 because it's top speed was in knots.

201MPH was an easier number to reach.

Question..... Why is the speed of sound in MPH.

goatflieg · #26 03-20-2023, 03:05 PM

Quote:

Originally Posted by Plummit

It has to do with the type of primer used...

-Marc

This response had me laughing hard. Very well played, Marc!

JonJay · #27 03-20-2023, 03:07 PM

Quote:

Originally Posted by gmcjetpilot

Back in the day all planes were in MPH before 1969. After 1969 they progressively transitioned to knots/hr for airspeed and knots for distance.

.

Partially correct. WWII US Navy Aircraft used Knots, just look up their operations manuals. There is some debate on whether the instrumentation was in Knots or MPH. I have seen panels with both, inner and outer rings, as is pretty common still. 1969 was when the FAA finally standardized Airworthiness directives. The IOAC started working on standardization in the late 40's, whereby aircraft used MPH, Knots, and KPH. It took a long time to reach standardization, or have we?

My Bucker was built in 1961 and still used "klicks". German design built by CASA in Spain. It has Spanish, English, and German placarding. It doesn't know it has an identity crisis.

How they standardized on "feet" for altitude so much earlier is beyond me.

rvbuilder2002 · #28 03-20-2023, 03:22 PM

Quote:

Originally Posted by JonJay

Partially correct.

I think this is totally correct.... in the context of the lighter side of general aviation anyway.

The POH for a 1975 C-150 was still in MPH.
It wasn't until a year or two later that Cessna had switch all of the new production aircraft over to Kts.

Ed_Wischmeyer · #29 03-20-2023, 03:29 PM

Decades ago, there was a big push to switch aviation from miles and MPH to knots. Guess which side won...

BTW, Class D airspace is now 4.7 nm (5 miles) because an expansion to 5 nm would have grabbed a lot of airspace where it would have been inconvenient for GA operations.

Piper J3 · #30 03-20-2023, 03:41 PM

I'll jump in here.... Per the OP’s question regarding RV-12…. I believe when Light Sport Category was enacted back in 2004, the thinking was to make flight instruction less costly with simple airplanes requiring less instruction (read - less knowledge). If I remember, some of the rationale was to make things less confusing, mph would be used for speed designation because it was already used for US ground transportation and well engrained.

I earned my PPL/ASEL in 1970. I fly my RV-12 as hybrid… airspeed is mph and navigation is nm. I have to confess… I like seeing higher number for speed...