Well I for one am knot going to get involved in this debate. I'm in knots just thinking about it. And I don't have enough popcorn.
Art
I fly in knots also.
Art
I fly in knots also.
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why MPH instead of knots?
- Thread starter Blw2
- Start date
Fun With Units….
Way back in the last century, when I was in Aero Engineering school, we had a visiting professor (from GD in Forth Worth, home of the F-16….) for our senior design project. He announced that the use of ANY speed units (mph, fps, etc…) other than knots would be cause for an immediate “F” on anything submitted for grading because “that’s how the industry works, and you’d better get used to it!” (Of course, all your computations were in fps, so you had to convert in the end….)
Didn’t bother me - I was already a pilot before I got to college, and was used to knots because that’s what the “system” used - even though I learned to fly in the days where most GA airplanes were still calibrated in mph.
Of course, I went on to run missions with a flying machine that used knots, feet-per-second, and Mach - depending on the phase of flight. And once we started flying with our friends overseas, we added meters-per-second to the mix. All in a days work.
I chuckle every September when I get together with my “fast friends” at the Reno Races and they all do everything in mph (even the airline and military pilots who use knots in their day jobs) because…yup, the numbers are bigger that way!
My own airplanes? Everything is in knots because that’s what my profession uses (for atmospheric flight), and what ATC expects.
Paul
Way back in the last century, when I was in Aero Engineering school, we had a visiting professor (from GD in Forth Worth, home of the F-16….) for our senior design project. He announced that the use of ANY speed units (mph, fps, etc…) other than knots would be cause for an immediate “F” on anything submitted for grading because “that’s how the industry works, and you’d better get used to it!” (Of course, all your computations were in fps, so you had to convert in the end….)
Didn’t bother me - I was already a pilot before I got to college, and was used to knots because that’s what the “system” used - even though I learned to fly in the days where most GA airplanes were still calibrated in mph.
Of course, I went on to run missions with a flying machine that used knots, feet-per-second, and Mach - depending on the phase of flight. And once we started flying with our friends overseas, we added meters-per-second to the mix. All in a days work.
I chuckle every September when I get together with my “fast friends” at the Reno Races and they all do everything in mph (even the airline and military pilots who use knots in their day jobs) because…yup, the numbers are bigger that way!
My own airplanes? Everything is in knots because that’s what my profession uses (for atmospheric flight), and what ATC expects.
Paul
AeroEngineer
Well Known Member
For years, I've heard that this is basic airplane marketing: Cruise speed stated in MPH, stall speed stated in knots. Obviously! Right?
You joke, but that's basically the kind of reasoning that was used to invent the Fahrenheit scale
You joke, but that's basically the kind of reasoning that was used to invent the Fahrenheit scale
But didn’t get it quite right so they needed to invent the centigrade scale.
Function vs bragging rights
I fly using Knots
I describe my flights using MPH to the plus 50 crowd
I describe it using KPH to those under 50 (oh, so easily impressed!)
My first 7A had a Flight Data Sys AFP-30 in it so I could also report cruise at Mach 0.256, but that seamed so un-Bragg able….
I fly using Knots
I describe my flights using MPH to the plus 50 crowd
I describe it using KPH to those under 50 (oh, so easily impressed!)
My first 7A had a Flight Data Sys AFP-30 in it so I could also report cruise at Mach 0.256, but that seamed so un-Bragg able….
Shark
Well Known Member
That's for the "Taxi Steering" thread.
On RVs, tailwheels are steerable, nosewheels are not!
You joke, but that's basically the kind of reasoning that was used to invent the Fahrenheit scale
I'm aware, but that's also true of Celsius, but for a different subject.
Fahrenheit:
100 degrees = Human body temperature +/- 5%
0 degrees = You're dead
To answer a question some of you may have, the zero point was chosen as the stable temperature of a saturated solution of ammonium chloride mixed with water ice, which achieves a very specific temperature when mixed. Conveniently, the freezing and boiling points of water happen to be nearly 180 degrees apart, as an interesting physical metaphor.
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Ancient history
For responders who are not really, really old here is the history of speed units that I experienced. I was in graduate school studying aero engineering when I was learning to fly, late 1960s. The FAA standard at that time was MPH. During that period the flight instruction world was in a bit of a tizzy because the FAA announced that they were going to "modernize" the use of speed units but did not say what the change would be. Most people thought it would be a change to metric, kilometers per hour or meters per second. I was astonished when the modernization was announced as a change from MPH to knots (early 1968 I think). Knots is a really old unit that originated with square-rigged sailing ships, and I still don't know how that seemed like modernization to the decision makers.
Anyway, all airplanes built before around 1970 used MPH, by FAA regulation. Van is roughly my age and started out in that scenario.
For responders who are not really, really old here is the history of speed units that I experienced. I was in graduate school studying aero engineering when I was learning to fly, late 1960s. The FAA standard at that time was MPH. During that period the flight instruction world was in a bit of a tizzy because the FAA announced that they were going to "modernize" the use of speed units but did not say what the change would be. Most people thought it would be a change to metric, kilometers per hour or meters per second. I was astonished when the modernization was announced as a change from MPH to knots (early 1968 I think). Knots is a really old unit that originated with square-rigged sailing ships, and I still don't know how that seemed like modernization to the decision makers.
Anyway, all airplanes built before around 1970 used MPH, by FAA regulation. Van is roughly my age and started out in that scenario.
gmcjetpilot
Well Known Member
,
"It originated from the Roman mille passus, or “thousand paces,” which measured 5,000 Roman feet. About the year 1500 the “old London” mile was defined as eight furlongs. At that time the furlong, measured by a larger northern (German) foot, was 625 feet, and thus the mile equaled 5,000 feet."
If the mile originated with 5000 Roman feet, how did we end up with a mile that is 5280 feet? Blame the furlong. The furlong wasn’t always just an arcane unit of measure that horseracing fans gabbed about; it once had significance as the length of the furrow a team of oxen could plow in a day. In 1592, the English Parliament set about determining the length of the mile and decided that each one should be made up of eight furlongs. As a furlong was 660 feet, we ended up with a 5280-foot mile."
"Each nautical mile originally referred to one minute of arc along a meridian around the Earth. Think of a meridian around the Earth as being made up of 360 degrees, and each of those degrees consists of 60 minutes of arc. Each of these minutes of arc is then 1/21,600th of the distance around the earth. Thus, a nautical mile is 6076 feet."
But where did the unit if foot or feet come from? “foot” is 12 inches long and was actually the length of King Henry I's foot. The inch was the length of 3 grains of barley end-to-end or the width of a man's thumb. The length between someone's outstretched arms was called a fathom.... Imperial unit standards are now referenced to metric units, example one yard is 0.9144 meter or 12 inches 0.3048 meters.
But what about a meter or metre? The metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole along a great circle, so the Earth's circumference is approximately 40000 km. Clearly measuring the earth is not easy. In 1799, the metre was redefined in terms of a platinum bar in Paris. Then it got real complicated using cadmium isotope wave length, Krypton-86 wave length and methane-stabilized helium–neon laser, finally the distance traveled at speed of light in a vacuum divided by 299,792,458.
Moral of the story it is a standard that is fixed and known, based on some arbitrary choices.
And a statue mile is modern? Statute mile is the result of Roman influences and plowing oxen.
"It originated from the Roman mille passus, or “thousand paces,” which measured 5,000 Roman feet. About the year 1500 the “old London” mile was defined as eight furlongs. At that time the furlong, measured by a larger northern (German) foot, was 625 feet, and thus the mile equaled 5,000 feet."
If the mile originated with 5000 Roman feet, how did we end up with a mile that is 5280 feet? Blame the furlong. The furlong wasn’t always just an arcane unit of measure that horseracing fans gabbed about; it once had significance as the length of the furrow a team of oxen could plow in a day. In 1592, the English Parliament set about determining the length of the mile and decided that each one should be made up of eight furlongs. As a furlong was 660 feet, we ended up with a 5280-foot mile."
"Each nautical mile originally referred to one minute of arc along a meridian around the Earth. Think of a meridian around the Earth as being made up of 360 degrees, and each of those degrees consists of 60 minutes of arc. Each of these minutes of arc is then 1/21,600th of the distance around the earth. Thus, a nautical mile is 6076 feet."
But where did the unit if foot or feet come from? “foot” is 12 inches long and was actually the length of King Henry I's foot. The inch was the length of 3 grains of barley end-to-end or the width of a man's thumb. The length between someone's outstretched arms was called a fathom.... Imperial unit standards are now referenced to metric units, example one yard is 0.9144 meter or 12 inches 0.3048 meters.
But what about a meter or metre? The metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole along a great circle, so the Earth's circumference is approximately 40000 km. Clearly measuring the earth is not easy. In 1799, the metre was redefined in terms of a platinum bar in Paris. Then it got real complicated using cadmium isotope wave length, Krypton-86 wave length and methane-stabilized helium–neon laser, finally the distance traveled at speed of light in a vacuum divided by 299,792,458.
Moral of the story it is a standard that is fixed and known, based on some arbitrary choices.
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gmcjetpilot
Well Known Member
The irony in this statement is that 200 mph is about 170 kts, not 160
Ahaaa 170 and kts is 195.633 mph not about 200 mph. There is no rounding in aviation for the love of lift and thrust gosh sakes. Ha ha.
jneves
Well Known Member
When casual sailors want to go faster, they buy a bicycle.
Dave
Dave
I realize this thread is more than a year old, but since so much of the thread was getting into the details...
The above statement is incorrect.
We do not use knots/hr for airspeed. Knots is already an airspeed, which is "nautical miles per hour". Knots/hr would mean "nautical miles per hour per hour", which is a rate of acceleration.
Similarly, we do not use knots for distance. Knots is a speed. We use nautical miles for distance.
Anyone look at/use the new international version of a flight plan? For cruising speed there are only 2 options: Mach number (enter "M") or Knots (enter "N"). "N"? I know English spelling can be hard, with silent "K's", but really, 'N'?
Average folk go buggy eyed when I tell them I normally cruise at 320 kph (160 knots easy rounded off conversion)
In Canada I grew up with mph, as a young adult had to now think in kph, got in to this aviation thing & work with knots. Now in retirement we all rely on Google map & think in hours & minutes to destination..
In Canada I grew up with mph, as a young adult had to now think in kph, got in to this aviation thing & work with knots. Now in retirement we all rely on Google map & think in hours & minutes to destination..
The world is out of sync with the USA on almost all units.
Issue that throws me in aviation is not the knots vs mph. It is temperature. A continuous switch between using F or C. I have been trying for 45 years to make up my mind on which I want to standardize around.
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vlittle
Well Known Member
Just convert in your head. Nothing can go wrong, of course. https://en.wikipedia.org/wiki/Gimli_Glider
0 degrees = dead.
In Search and Rescue recovery. (I.e. extreme hypothermia) we say: “they are not dead until they are warm and dead” I think 60F is the existing record set in the late 1990’s
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