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-   -   Knots or MPH?? That Is The Question (https://vansairforce.net/community/showthread.php?t=81947)

longranger 01-30-2012 09:01 AM

Quote:

Originally Posted by Jamie (Post 622874)
Virtually every single reference to speed and distance in every aeronautical document, chart, sectional, AIM, FAR, not to mention every controller uses nautical miles.

It's the unit for the system. Anything else is just for bragging rights.

THE system for bragging rights is furlongs per fortnight, eighths of a mile (statute:D) per two weeks.

Flying at 7500ft is fairly handy in my 170 as the indicated mph is pretty close to true knots.

MarkW 01-30-2012 09:33 AM

Knots
 
Learned to fly in an old 172 with MPH. My instructor told me to use the inner numbers (knots) not the outer ring with the wrong numbers. Since then I have been flying newer 172's with knots. Learned to fly IFR using knots. Started visiting this site and many RV'ers were using the MPH and I am thinking "What the heck".

John Clark 01-30-2012 11:55 AM

"Back in the day" when I bought my used B-55 Baron, it was equipped with a dual scale A/S with knots on the inside ring. I sent the gauge off to the instrument shop where they rescreened the face to show only knots. Come to think of it, the last airplane I had with an MPH A/S was my J3 Cub, which I sold in 1970 :rolleyes:

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA

dutchroll 01-30-2012 11:30 PM

Quote:

Originally Posted by longranger (Post 623553)
THE system for bragging rights is furlongs per fortnight, eighths of a mile (statute:D) per two weeks.

Flying at 7500ft is fairly handy in my 170 as the indicated mph is pretty close to true knots.

I was wondering how long it would take for "furlongs" to be mentioned! ;)

Flying Scotsman 01-31-2012 12:14 AM

Quote:

Originally Posted by dutchroll (Post 624011)
I was wondering how long it would take for "furlongs" to be mentioned! ;)

I like slugs as the unit of mass, too. :)

MauiLvrs 01-31-2012 12:34 AM

Quote:

Originally Posted by MarkW (Post 623571)
Learned to fly in an old 172 with MPH. My instructor told me to use the inner numbers (knots) not the outer ring with the wrong numbers. Since then I have been flying newer 172's with knots. Learned to fly IFR using knots. Started visiting this site and many RV'ers were using the MPH and I am thinking "What the heck".

The numbers are bigger:confused:

dutchroll 01-31-2012 12:45 AM

Heh, I vaguely remember "slugs" from my aerodynamic days at uni. But I don't think I ever did understand why someone came up with such a unit! :)

Hey Vlad, if it's any consolation, I like the metric system and think it makes emminent sense (we converted down under several decades ago, and I speak "both" languages despite my public disdain for mph). But I think the hotchpotch of "standard" aeronautical units is here to stay for a while! ;)

Flying Scotsman 01-31-2012 01:21 AM

I've actually never understood why certain manufacturers (certificated or experimental) would mark their systems in mph. The *system*, at least in the U.S., uses knots and nautical miles. I've never heard an ATC specialist ask for or assign any speed in miles per hour.

As some of us know all too well, mixing measurement systems can be a recipe for disaster...

At least nautical miles and meters are related to measurements of the earth...1 nm = 1 minute of arc, 1 meter = 1/10,000,000th of the distance from the equator to the pole). Statue miles are essentially arbitrary. :)

(BTW, a Roman pace was *two* steps, not one...)

(I don't know if it's actually true or not, but my physics prof asserted that if you use the furlongs/fortnight/slug system, virtually all physical constants end up being approximately 1 x 10^some power :) I suspect he just made that up to see if we were listening!)

Can you tell I'm up late and bored tonight? LOL!

RV8R999 01-31-2012 04:29 AM

The ATC already mixes systems...

Wx is reported in statute miles and therefore the visibility portion of approach minima are published in statute miles...

why do we use Feet instead of meters?

sailvi767 01-31-2012 06:51 AM

Quote:

Originally Posted by RV8R999 (Post 624032)
The ATC already mixes systems...

Wx is reported in statute miles and therefore the visibility portion of approach minima are published in statute miles...

why do we use Feet instead of meters?


I think the feet verses meters issues was decided by Pan Am. Much of the worlds conventions on how we fly date back to their early days where there were no standards. Not all nations however use the ICAO standard of feet. Its a pain in the ____ flying in countries that do not with a aircraft set up for feet. Leveling at 11100 meters is one thing but when they ask you your altitude passing and its 26,700 feet by the time my slow brain has done the conversion to meters the number is history not where we are at the moment. Approaches get especially tricky because they often convert from meters standard to local altimeters at very low altitudes like 1200 meters. Add in another conversion since the same countries often use QFE instead of QNH for altimeter settings and things get interesting for the math inept among us.

George

Mel 01-31-2012 07:18 AM

Actually it's Both!
 
I fly left seat. Ann flies right seat.
Left side of the panel is knots. Right side is mph.
She goes faster than I do, but has further to go.
We usually get there about the same time.

RV8R999 01-31-2012 07:35 AM

Quote:

Originally Posted by Mel (Post 624079)
I fly left seat. Ann flies right seat.
Left side of the panel is knots. Right side is mph.
She goes faster than I do, but has further to go.
We usually get there about the same time.

now this is funny!

marchudson 01-31-2012 07:42 AM

What I use
 
Personally I use the universal standard of all measurements, the Horse length.

http://en.wikipedia.org/wiki/Horse_length

Currently my RV-7 goes 151,840 horse lengths / hour or 2531 horse lengths / sec, commonly referred to in the industry as HLPS.

Matter of fact, I was racing a B-55 the other day and on the start, he had me by "the slimmest fraction of a nose." However, by the end of the 2 mile course I had pulled head by at least 25 horse lengths. It was at this point that he noticed a dark substance streaming from my aircraft. He radioed and asked what was coming out of the back end of my trusty steed. To which I replied, "It's horse......" Well, you get the picture. :D

Sig600 01-31-2012 08:05 AM

How far across your EFIS screen does a 6 digit speed tape go? :eek:

wacarlton 01-31-2012 08:38 AM

Quote:

Originally Posted by Sig600 (Post 624099)
How far across your EFIS screen does a 6 digit speed tape go? :eek:

I typically use knots, but when I want to impress someone - I use Smoots. Hopefully Rob and crew will include an AFS update that will allow the EFIS to display in KSPH, SPS or SPM. 190.4 KSPH sounds faster than 175 knots. 3,174 SPM sounds a LOT faster.

Flying Scotsman 01-31-2012 11:56 AM

Quote:

Originally Posted by RV8R999 (Post 624032)
The ATC already mixes systems...

Wx is reported in statute miles and therefore the visibility portion of approach minima are published in statute miles...

Isn't that because the weather observations are done by a certified weather observer (or automated system) that is certified by the National Weather Service? (which uses statute miles)?

Geico266 02-03-2012 05:53 AM

Has anyone notice the performance numbers published by Van's Aircraft for our airplanes is in MPH? Hmmmm?

http://www.vansaircraft.com/public/rv-6per.htm

Why would we change what the engineers of our aircraft have determined to be a better unit of measure? ;)

David-aviator 02-03-2012 06:19 AM

Quote:

Originally Posted by Geico266 (Post 625304)
Has anyone notice the performance numbers published by Van's Aircraft for our airplanes is in MPH? Hmmmm?

http://www.vansaircraft.com/public/rv-6per.htm

Why would we change what the engineers of our aircraft have determined to be a better unit of measure? ;)

Marketing, its all about marketing.

From the Reno Air Race web site "Five days of racing action. Six classes of aircraft and speeds exceeding 500 mph."
It reads and sounds better than 434.48 knots.

But here, clearly the KNOTS have it. Or is it we have KNOTS. :)

Geico266 02-03-2012 07:15 AM

Quote:

Originally Posted by David-aviator (Post 625313)
Marketing, its all about marketing.

From the Reno Air Race web site "Five days of racing action. Six classes of aircraft and speeds exceeding 500 mph."
It reads and sounds better than 434.48 knots.

But here, clearly the KNOTS have it. Or is it we have KNOTS. :)

I think this sums it up pretty well.

Knots or MPH, the important thing is get out there and fly. ;)

rgmwa 02-03-2012 07:40 AM

Quote:

Originally Posted by Mel (Post 624079)
I fly left seat. Ann flies right seat.
Left side of the panel is knots. Right side is mph.
She goes faster than I do, but has further to go.
We usually get there about the same time.

Mel, that's no help at all :D

ronschreck 02-03-2012 07:48 AM

It's all relative
 
Quote:

Originally Posted by Mel (Post 624079)
I fly left seat. Ann flies right seat.
Left side of the panel is knots. Right side is mph.
She goes faster than I do, but has further to go.
We usually get there about the same time.

In a 4-place airplane I always fly in the front seat so I get there first. :D

John@JohnKean.com 02-03-2012 08:37 AM

Airworthiness standards for Normal, Utility, Acrobatic and Commuter Category Airplanes, Title 14, Part 23, specify that distances are to be in nautical miles, and speeds in knots. From a practical point of view, a nautical mile is identical to a minute of latitude, a distance in nautical miles on a chart can easily be measured by using dividers and the latitude scales on the sides of the chart. OK, now I have identified myself as someone who flew long before GPS.

DonFromTX 02-03-2012 08:52 AM

You mean people actually did aviate prior to GPS? How crude! :)

Quote:

Originally Posted by John@JohnKean.com (Post 625357)
Airworthiness standards for Normal, Utility, Acrobatic and Commuter Category Airplanes, Title 14, Part 23, specify that distances are to be in nautical miles, and speeds in knots. From a practical point of view, a nautical mile is identical to a minute of latitude, a distance in nautical miles on a chart can easily be measured by using dividers and the latitude scales on the sides of the chart. OK, now I have identified myself as someone who flew long before GPS.


RV8R999 02-03-2012 09:05 AM

Quote:

Originally Posted by John@JohnKean.com (Post 625357)
Airworthiness standards for Normal, Utility, Acrobatic and Commuter Category Airplanes, Title 14, Part 23, specify that distances are to be in nautical miles, and speeds in knots. From a practical point of view, a nautical mile is identical to a minute of latitude, a distance in nautical miles on a chart can easily be measured by using dividers and the latitude scales on the sides of the chart. OK, now I have identified myself as someone who flew long before GPS.

If we are to use airworthiness standards as the metric for appropriateness, despite lack of applicability to EAB, then I believe we should at least be consistent in their application...

ELT Ant locations
Certified GPS ant installation requirements
Pilot Operating Manuals
Adherence to engine RPM and other limits such as Vne
Max Gross Weight deviations
etc...

my .01

Geico266 02-03-2012 09:25 AM

Quote:

Originally Posted by rgmwa (Post 625338)
Mel, that's no help at all :D

But it was funny!

Good one Mel.

I always thought you were a little slower than your bride. ;)

carlrai 02-03-2012 09:36 AM

I used primer...
 
...have tricycle gear, a slider canopy and use knots for my airspeed.

There that covers all of them.

Steve 02-03-2012 10:46 AM

Quote:

Originally Posted by Geico266 (Post 625304)
Has anyone notice the performance numbers published by Van's Aircraft for our airplanes is in MPH? Hmmmm?

http://www.vansaircraft.com/public/rv-6per.htm

Why would we change what the engineers of our aircraft have determined to be a better unit of measure? ;)

I used both actually. Knots to flight plan and cruise. MPH to land.
My airspeed indicator has MPH on the outer (easy to read) scale so I could quickly verify my numbers against Vans.
402 hours later I glance at it occasionally like when in turbulence or while in the pattern. I think most of fly by the seat of our pants after a while anyway.

Mark12A 02-03-2012 01:52 PM

Knots or MPH?
 
Think big. Use Mach.

Mike S 02-03-2012 01:53 PM

Quote:

Originally Posted by Mark12A (Post 625490)
Think big. Use Mach.

Think real big-----use warp factor;)

Mark12A 02-03-2012 02:03 PM

Warp Factor?
 
During bomber competitions, one word indicated a direct hit:

Shack!

rgmwa 02-03-2012 03:30 PM

Quote:

Originally Posted by Geico266 (Post 625388)
But it was funny!

Good one Mel.

Agreed, Larry. Made me laugh. I thought Mel's practical view of the whole knotty problem cut straight to the bottom line :)


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