Knots are for boats!

[rsiano]

I have been bothered by the change from miles per hour to knots for speed values for aircraft for more than 35 years. Lets bring back miles per hour for aircraft. For example, since most people reference speed using miles per hour, advertising a speed in knots for new aircraft is penalizing their perceived capability. For example, the listed maximum cruise speed for the Cessna Citation Ten is 527 knots or it is 605 miles per hour. Which sounds more impressive? To me it is 605 mph. What do you think?
Thanks!

[EpsilonVaz]

......which sounds even better as 974kph (which is more commonly used worldwide than mph).

[svhar]

The metric system is the only way. The Russians are way ahead of us. Miles and knots are from the past. As are gallons, stones, yards, feet and inches.

[Capt Claret]

Haven't used mph for 40 years. Knots or kph for me please. A few hundred million Americans might be happy with mph but hundreds of millions more non Americans won't.

[27/09]

For me it comes down to using the graticule scale on a chart for measuring distance. One minute of one degree of latitude equals one nautical mile, therefore the use of knots makes perfect sense.

P.S. I can't agree that the metric system is the only way to go.

[galaxy flyer]

The metric system is a scurvy French idea brought to us by a Corsican defeated by Lord Wellington. Unfortunately, Napolean is getting his revenge.

[zerozero]

Totally agree with 27/09.

As long as we're navigating with nautical miles it makes more sense to use knots.

The metric system is useful in other applications (lab work for one).

But whatever the case, we should ALL be using the same measurements (China, I'm looking at YOU).

:hmm:

[sevenstrokeroll]

27/09...agree

and folks, DME is in knots

also, descent tables for ILS glideslopes can be approximated by using ground speed IN KNOTS time 5 for descent rate in FPM.

I remember the changeover...hated it then...happy about it now.

also, wasn't it "the high and the mighty" where the navigator makes a mistake in converting miles to knots and screws up things?

[Mach E Avelli]

Until they rejigger the whole system of positioning away from latitude and divide the points of the compass and bearings into something like 100 or 1000 units, the knot will stay. And rightly so, otherwise I would have to buy new charts, a new gps and a new compass for my boat and my bugsmasher.
Statute miles are up there with leagues and cubits as an outdated measure of distance. Like gallons and lbs.
Km is alright for cars, but is pretty useless in the middle of an ocean.
When the USA was the leading builder of aircraft they could get away with mph, but if they went back to that now, they would lose even more sales to those pesky foreigners.

[ImbracableCrunk]

"The metric system is the tool of the devil! My car gets forty rods to the hogshead and that's the way I likes it."

[InSoMnIaC]

a bit off topic but since someone mentioned the metric system. It seems pretty stupid why metric using countries like China issue altitudes in Metres but Rate of descent or Climb instructions in feet per minute. yeah i know the VSI if in fpm in most aircarft but so is the Altimeter. Make up your mind. Either metres or feet

[Loose rivets]

In Pillars of the Earth, Ken Follett had his man keeping the rod locked in a stone shed. Careful with it, they were. Trouble was, it wasn't quite the same length as the rod in the next town. Then there's time and the railway.


The world will have to be divided up metrically one day. Charts will all be on iPad type things, and correct for curvature as one sweeps the locations. Coming from the days of ink pens and curved localizer tracks, I welcome the technology.

Mind you, Miles per Gallon should be absolved from all requirements governing change.

[Tu.114]

With all the inability to agree on one of the already present units of measurement, maybe it would be better to find something new for widespread use?

There are so many possibilities ranging from Angström/week via Stadions/Olympiad to A. U./Indiction, there is surely one to be found that no-one in the world has ever used and consequently is not ideologically burdened and may be introduced worldwide?

[Firestorm]

Knots are a perfectly acceptable and sensible method of expressing speeds for aviation. Before changing that perhaps it would make more sense for the Yanqis to adopt metric measures and weights for fuel rather than using the US gallon measurement which is easily confused with the proper gallon which even us Brits have largely given up on (as it would cause us a severe brain haemorrhage and fit o rage) when buying petrol for our cars as it currently cost about £6.50 per gallon.

[fireflybob]

For me it comes down to using the graticule scale on a chart for measuring distance. One minute of one degree of latitude equals one nautical mile, therefore the use of knots makes perfect sense.

27/09 I think you will find that's the geographic nautical mile (which as I am sure we know varies in distance over the earth since the latter is an oblate spheroid).

The International Nautical Mile, last time I checked, is defined as 1852 metres (no doubt the eurokrats got their hands on this definition!).

That said I agree with your reasoning for sticking with nautical miles and knots - "miles per hour" was an awful American invention.

[Saint Jack]

rsiano: Not a particularly accurate statement, '27/09'. 'zerozero', 'sevenstrokeroll' (eh!) and 'mach E avelli' are correct, knots are for NAVIGATION.

[Al Murdoch]

It actually makes sense to have a variety of systems of measurement in use for different things... For example, RVR and visibility are expressed in meters, speed in knots, altitudes in feet.
If you hear someone say 10,000 Feet, you know they must be talking about altitude (generally speaking). If you hear 100m, its likely to be RVR etc etc.

[Check Airman]

If you hear someone say 10,000 Feet, you know they must be talking about altitude (generally speaking). If you hear 100m, its likely to be RVR etc etc.

You could also hear 300ft in the US. Now is that cloud base, or RVR?:}

[nitpicker330]

RVR 300' ( 91 m ) wow that's way below CAT3B territory and I think you'd be told "RVR 300 feet". Couldn't even takeoff with 300' RVR :eek:

[darkroomsource]

If you hear someone say 10,000 Feet, you know they must be talking about altitude (generally speaking). If you hear 100m, its likely to be RVR etc etc.
You could also hear 300ft in the US. Now is that cloud base, or RVR?
Wasn't that his point?
use knots for speed, miles (nautical miles preferably) for distance, feet for altitude, meters for RVR, feet per minute for climb/descent.
Then, you know what's being talked about based on the unit of measure.
Of course, if you grew up in the US, it's hard to judge distance by meters, because they're aren't exactly yards... and if you grew up elsewhere it's hard to judge height by feet, because you have to divide by 3 (approximately).

[Calmcavok]

Why not measure in multiples of "Wales"? You often hear people/media describing places relative to the size of Wales (I recall Australian farms often being described as x times the size of Wales).

Your common or garden jet would travel approx 3 Wales/hr, a turboprop would be about 2 Wales/hr. Height could be measured in fractions of Wales's.

Just a thought.

[stilton]

I vote for Warp Factor..

[InSoMnIaC]

I vote for Warp Factor..

Lets break the sound barrier first then we can talk about warp factor

[AdamFrisch]

I grew up in metric, but obviously comfortably use feet and knots in my flying. However, you often hear in t he UK and the US "I can't think in metres" and how they can't gage it. Exactly the same problem I have in feet - I can't gage a distance in it without first doing the conversion from meters.

But there's a simple solution for you guys and everyone could use meters tomorrow in the old "Farenheit"-belt of the world; Because you can all use yards, right? A yard is a meter!

[yotty]

Not too sure that a yard equals a meter. Could we settle on fathoms? ;)

[FlightPathOBN]

I would like to see them dump the mag compass headings and magvar...

with grid north and GPS, the whole mag nomenclature for runways is a real pain, especially when it switches, and they re-name the runways....

[Uncle Fred]

Prefer knots for flying. Although grew up with feet/inches/yards, the metric system is just fine--base ten arithmetic works every time!

Don't mind visibility in metric but I do prefer the FLs the way they are (in other words not in meters). For me it is just simpler to use. Always a bit of a thinking exercise when flying into or through China's airspace. Much easier now going through Russia's and I might be wrong about this, but it seems the controllers like it as well.

[daved123]

Uncle Fred, I am sure you must have seen it in Vendee also, the French, in the home of the metric system, have invented a new non-metric system of distance measurement - The Minute !
All over we see direction signs to McD, Intermarché, Leclerc etc "au feu a droite, 2mn" (at the traffic signal, turn right, 2minutes) although if anybody tried to achieve those timings they would suspect that, being patriotic, they must have asked Air France to calculate the 'distance'
daved

[parabellum]

RVR 300' ( 91 m ) wow that's way below CAT3B territory and I think you'd be
told "RVR 300 feet". Couldn't even takeoff with 300' RVR


Think you may be a bit confused there Nitpicker, CAT3B can be zero/zero in terms of viz and cloud base for both landing and take off, depends on the capability of the aircraft/state of airport aids/crew recency etc. as well as your own airlines SOPs. Been a while since I did one but I seem to remember 75meters and 20' as the landing minima for the B747-400 that I flew and that had more to do with taxying than landing.

[Herod]

Flew an aircraft many years ago where we uplifted fuel in litres, calculated it in kg, the main tanks were gauged in Imp gal, and the aux tanks in USG. My brain hurt. Having then flown for many years using runway lenth in metres, I moved to a company which used manuals direct from Boeing (this in the UK) and I had to start thinking in feet. Counterintuitive.

[Piltdown Man]

Seconds, minutes, feet in nautical miles (ish), degrees of latitude - can I stick with knots please?

[boguing]

On a septic web forum a few years ago a native pointed out that the handy 345 triangle trick wouldn't work in metric. He went quiet when I pointed out that it would work with Cornflake packets.

[GOLF_BRAVO_ZULU]

Isn't the whole point of a 345 triangle that it is devoid of the need for specific units of linear measurement? They could be in Millimeters or Cables (tenth of a nm) and still give the correct ratios for Mr Pythagoras's wonderful triangle.

Just wait until some brown job artillery wallah comes along and tries to convince you that Mils are better than Deg, Min, Sec of arc. You will then get the tedious explanation about a Metre being one ten-millionth of the meridion that passes through somewhere called Paris and how easy it is to pace it out on an OS map or NATO JOG chart. He (or possibly she these days) should be told that metres are too bloody small for anything horizontal and too big for anything vertical.

[boguing]

Yep.

Fun can still be had though. Surveyor friend asked me to help him lay out a site. Field into 'plots'. And although a more than successful yachtsman and navigator, it became apparent that 345 didn't feature in his knowledge.

Sent him off with the tape reel and giving him different multiples of 3,4 and 5 on each occasion that we had to establish a right angle. Wish I'd videoed it. The more that I hysterically giggled, the larger the multiple had to be so that he couldn't hear me.

I've never actually confessed to it...

Until now. Colin.

[Uncle Fred]

Uncle Fred, I am sure you must have seen it in Vendee also, the French, in the home of the metric system, have invented a new non-metric system of distance measurement - The Minute !
All over we see direction signs to McD, Intermarché, Leclerc etc "au feu a droite, 2mn" (at the traffic signal, turn right, 2minutes) although if anybody tried to achieve those timings they would suspect that, being patriotic, they must have asked Air France to calculate the 'distance'
daved



Ah yes, the French minute--un peu de temps! Fungible, with plasticity, without fixed interval...it has a character of its own but does add a element of relaxation to the proceedings.

Reminds me of the quote from Gustav Flaubert Une minute--On ne se doute pas comme c'est long, une minute

[reynoldsno1]

I believe, in principle at least, that the Chinese are going to use feet for altitude at some unspecified date in the future. Same goes for WGS84 co-ordinates.

[stilton]

'Lets break the sound barrier first then we can talk about warp factor'


That was done a few years ago actually :confused:

[Capot]

As a Gunner (RA) I was around when we changed in the early 1960s from yards (NOT equal to a metre!) and degrees, to metres and mils (6,400 in a circle, vs 360X60X60 seconds). The simplicity of the shell-lobbing arithmetic from that moment was wonderful.


Metres have a scientific basis as a measurement constant and navigation tool, just as knots do. Statute miles, yards, feet and inches are something to do with how Roman soldiers would yomp along and other measures that meant something 2,000 years ago, and they belong in that time.

I navigate my boat in knots/nautical miles, because I locate myself using latitude and longitude, and so does my GPS when it's not on some national grid or another. My aircraft, when I owned one, measured speed in knots so I navigated in nautical miles. If I'm using a map on land I navigate in metres/kilometres/kph because, in the UK and most other countries I plod around in, the grid and vertical measurements on the map are metric. And thank God for that.

[nitpicker330]

Parabellum:-- nope no confusion mate. CAT 3B at KJFK still requires at least 600' RVR to "commence the approach" you cannot commence any approach on the planet in zero zero.!!

Any approach below 1000' can be continued to minima for a look see if the RVR falls below minima. CAT 3B on the other hand can continue to land as visual ref is not needed until after nose wheel touchdown.

Although you'd be pretty brave to land in zero zero CAT 3B...

[Uplinker]

It is actually quite useful that our units for speed, distance and altitude are all different, because that prevents confusion.

If we hear an instruction in feet or flight level, we know it refers to altitude. Similarly; Knots = speed, miles or nautical miles = distance, Kilometers or meters = visibility.

Be careful what you wish for: If it was ALL in meters, can you imagine the potential confusion?:- "Speedbaby 123, descend altitude four kilometers to be level four zero kilometers before Brookman's Park, speed four zero zero kilometers per hour, RVRs at Stansted four zero zero/four zero zero/four zero zero meters".

Think about also the extra RT time that would be involved in a busy TMA taken up by having to say 'kilometers per hour' each time instead of simply 'knots'.

[hawker750]

What does in matter, fly an Airbus, it seems airspeed indication is an optional extra!

[DX Wombat]

A yard is a meter! Would that be Gas, Electric or Water? := :*
Anyway, you have all got it completely wrong, Knots are for keeping Boy Scouts, Cubs, Brownies and Guides occupied when the Leader can't think of anything else for them to do. :p ;)

[A Squared]

I locate myself using latitude and longitude, and so does my GPS

Actually, it doesn't. It locates itself in Earth Centered, Earth Fixed Cartesian coordinates, using meters as a unit. It *displays* its position in latitude and longitude entirely for your conveninece.

[Capot]

You are right; how could I have been so lax.

I meant to say "I locate myself using a pencil and a parallel ruler to mark a position on a chart showing latitude and longitude, while my GPS locates itself in Earth Centered, Earth Fixed Cartesian coordinates, using meters as a unit and then displaying its position in latitude and longitude entirely for my conveninece."

And then I would have checked my spelling, just to make sure I would escape all criticism, and corrected any errors that I noticed.

[valvanuz]

A yard is a meter!

Fine with me, you sell me meters, I'll pay you yards

[Capot]

1 yard = 0.9144 metre

You lose!

[sablatnic]

Capot could be right. Last I had a yard of ale, it was just 3'!
;)

[Capot]

There are 3 possibilities for what the yard was based on, and none of them encourages one to go on using it;

1. It's a double cubit. ("What's a cubit?" "Half a yard, stoopid".)

2. It was more or less the distance around a man's waist.

3 It was the distance from King Henry I (1100-1135)'s nose to his thumb, with his arm outstretched, or something like that. That's King Henry I of England, and some of France as I recall, perhaps wrongly.

The word 'yard' comes from the Old English gyrd, meaning a rod or measure

Enough already.

[oxenos]

I'm with yotty on this. Fathoms. The original decimal system.
100 Fathoms = 1 cable. 10 Cables = 1 Nautical mile.
So, speed in knots, height in fathoms, vis in cables.

"XXX, you are cleared to descend to 300 fathoms, radar heading North North East by East, report established ILS for runway North West By North Port, RVR 1 cable."
What could be simpler?

[FlightPathOBN]

Vessel speed at sea was measured using a chip log. This consisted of a wooden panel, weighted on one edge to float upright, and thus present substantial resistance to moving with respect to the water around it, attached by line to a reel. The chip log was "cast" over the stern of the moving vessel and the line allowed to pay out.
Knots placed at a distance of 47 feet 3 inches (14.4018 m) passed through a sailor's fingers, while another sailor used a 30 second sand-glass (28 second sand-glass is the current accepted timing) to time the operation.
The knot count would be reported and used in the sailing master's dead reckoning and navigation. This method gives a value for the knot of 20.25 in/s, or 1.85166 km/h. The difference from the modern definition is less than 0.02%.

there is the foundation of your measurement...

[grounded27]

To the OP, I feel it disturbing that it disturbs you. It should though be globally standard, same goes for altitude and spoken language with ATC.

[18-Wheeler]

The metric system is the only way. The Russians are way ahead of us. Miles and knots are from the past. As are gallons, stones, yards, feet and inches.

^this^
The old Imperial system is on its last gasps, as it should be. Aviation is the last stubborn area where it's hanging on and I hope that it transitions as quickly as possible to full metric.

Though I would actually like to see Planck Units used, they make even more sense than Metric does.

[FullWings]

Not to mention millibars, hectopascals, inches and mm of mercury. All still in use today in aviation, somewhere in the world...

[jxk]

What about TIME: Could we please have a year equalling 1000 days with 10 months of a 100 days and a week of 10 days. The World wasn't built for metric units but for aesthetics where a pint of beer looks and feels right and is what an average person wants to consume in any one session. The same applies to weights: a pound of anything is much more to the human scale than kilograms etc. Packing is another problem much easier to pack a dozen items (3x4 or 2x6) than 10. And why isn't the World a perfect circle rather than an oblate ellipse? In the World of computers it's binary so 1s and 0s and thus bits, bytes hexadecimal octal .....

[Bergerie1]

I think the ancient Egyptians first divided the day into 24 hours, 12 hours of day and 12 of darkness. But the base of 60 (for time and compass directions) came from the Babylonian system of counting which they may well have inherited from the Sumerians. Many of our current methods of counting and measurement come from very ancient roots! Rather than changing them let's glory in their antiquity. Also, 60 is quite convenient as it can be divided in many ways.

[A Squared]

Not to mention millibars, hectopascals, inches and mm of mercury. All still in use today in aviation, somewhere in the world...

Converting from Millibar to Hectopascals is pretty simple, being as they're the same.

[boguing]

Look folks - this is really simple.

Exactly 6,000 Years ago, the Creationistas say that we were made.

We were a bit confused, and so concentrated on our fingers and toes, and decided that base 10 could work.

We then discovered that the World was spherical-ish and created a flawed mapping system.

They saw that one could divide the oblate spheroid into segments, like the Oranges that they were enjoying when boiled with sugar and made into Marmalade.

Good result. It worked. But.

They didn't spot that Lines of Latitude might have been better replaced by choosing an East and West Pole and cutting the sphere into segments akin to those that Lines of Longitude do.

They would then have been able to work out the best way to eat a Grapefruit.

Notwithstanding this error, some bright spark realised that multiples of 12 offer more outcomes of subdivision than those of 10. Good point, and well made.

Then at some point (and I'd welcome some input from the Creationistas for an exact date) we noticed the stars and Sun/Moon/Planets, and made some notes. And with some sums worked a few things out so that we could guess our location.

A bit further along, Radio was created, (again, input welcomed) and some people (who turned not to be on our 'like' list) came up with "Ultrakurzwellen-Landefunkfeuer".

This was not good news.

But it was a turning point (sorry). Thereafter the electronic and radio based systems (with the exception of the simple RDF) relied on lines on maps for co-ordination which were entirely arbitrary. The 1980s gave us (civilians) electronics which would do their stuff and give us Lat/Long - but only thinking in 1/0s internally.

Today the gps system does not have a clue about units that we would use. They work out where we are and, in much the same way as we would say 'print' on some data, it stuffs it through the last bit of software to demonstrate some sort of recognisable position.

That, folks, is my take on the history of mapping.

Now if I could start.......

[parabellum]

Just a personal opinion but, as already pointed out by several above, the current system is the best way to go. Using separate units of measurement for speed, height, RVR/viz etc. avoids misunderstanding and the speed with which the current, commercially orientated, flying schools are churning out new pilots these days I'm all in favour of as many built in safety devices as possible. Happy to see there is no serious effort by any major aviation organisation to change the present, western system.

[square leg]

What you say is true, but it's knots the entire truth!

[InSoMnIaC]

That was done a few years ago actually

So it was Stilton. time for Warp factor after all

[Al Murdoch]

Check Airman - thank you for making my point for me... Ahh, the USA, where even the paper is a different size and shape to the rest of the globe.

[Old Smokey]

I'm surprised that someone hasn't raised the point that the Nautical Mile is ESSENTIALLY a Metric unit, being defined as EXACTLY 1852 M, and equal to 1 minute of arc of latitude. Degrees, Minutes, and Seconds are an integral part of the Metric system. I say essentially a Metric unit, see the extract from Wikipedia below, where, in red, it is noted that it is accepted for use in the International System of Units by the BIPM. It's equivalent in feet or other units is a surd.

Courtesy of Wikipedia - The nautical mile (symbol M, NM or nmi) is a unit of length that is about one minute of arc of latitude measured along any meridian, or about one minute of arc of longitude at the equator. By international agreement it is exactly 1,852 metres (approximately 6,076 feet).

It is a non-SI unit (although accepted for use in the International System of Units by the BIPM) used especially by navigators in the shipping and aviation industries, and also in polar exploration. It developed from the sea mile and the related geographical mile.

The nautical mile remains in use by sea and air navigators worldwide because of its convenience when working with charts.
- END Wikipedia quote.

The International Nautical Mile was established in 1929, adopted by the U.S.A. in 1954, and belatedly by the Brits in 1970 when they finally standardised and dropped their beloved 6080 ft Nautical mile (But it's legacy lives on in things like the constant of 38.94 instead of 38.9679 for Mach Number to TAS computation ~ some errors never die!).

A system that essentially provides for navigation, and as a bonus is an accepted de-facto member of the Metric system, is, I believe, more useful and appropriate than the distance that a Roman soldier could march in full kit between rests:\

Time to bury the milus and the mile with the cubit and other quaint measures.

Best Regards,

Old Smokey