Aer Lingus still using Miles Per Hour (not Knots)

What Vision?

When I fly with Aer Lingus the pilots always give the ground speed in Miles Per Hours, and the wind speed at the destination airport in Miles Per Hour.
I don't get why they do this. It really bugs me. I'm so used to km now when driving and the weather report in km/h.

Now I know that planes use Knots for speed and NAUTICAL Miles for distance, Which have nothing to do with a Mile on the ground, they are two very different things. A nautical Miles is defined as exactly 1852 metres. Why 1852 metres, I don't know, I think it was a comprimise between all the different Nautical Miles used by differnt countries. I think it sould have been made 2000 metres or just have used km for everything.

Anyway getting back to my question, does anyone (maybe a pilot here) know why they give ground speed in miles per hour and weather conditions in miles per hour and not use km/h?

I fly between Ireland and another country with Aer Lingus that uses the metric system completely and people from there wouldn't have clue as to what a mile is at all, and about 60% of apssengers are from that country.

ONly once did a pilot use km/h for speed and metres for altitude.

Alun

What Vision? wrote: »

A nautical Miles is defined as exactly 1852 metres. Why 1852 metres, I don't know, I think it was a comprimise between all the different Nautical Miles used by differnt countries. I think it sould have been made 2000 metres or just have used km for everything.

A nautical mile corresponds to one minute of arc (1/60 of one degree) on any meridian (line of longitude) on the earth's surface, and while it's true that there were various different versions used by different countries, they didn't vary by much .. only a metre or two.

Ham'nd'egger

Alun wrote: »

A nautical mile corresponds to one minute of arc (1/60 of one degree) on any meridian (line of longitude) on the earth's surface, and while it's true that there were various different versions used by different countries, they didn't vary by much .. only a metre or two.

I'd take land miles per hour anyday over a knot or nautical mile

By and large, people here still trade in miles so I would imagine that it easier for Irish people to take into account over kilometers. Bear in mind that the pilot just gives you that information just as a courtesy, though I take your point; a standard would be nice.

Calina

My experience is that they give both kmh and mph over the ground.

Moving to Aviation though they might have a greater input there.

What Vision?

Alun wrote: »

A nautical mile corresponds to one minute of arc (1/60 of one degree) on any meridian (line of longitude) on the earth's surface, and while it's true that there were various different versions used by different countries, they didn't vary by much .. only a metre or two.

That maybe where it came from but it has been adjusted to 1852 metres exactly. I know this cos I use it everyday in work on sea charts.

So 1 nautical Mile is 1.852000000000000000000000000000000000000000000000000* km


I'm not accoustomed to miles anymore. I've been just driving in km/h for a few years now, even for a few years before Ireland converted. To go back to miles per hour just gets me confused.

FlutterinBantam

Take the macro view there son,obviously the pilot thinks the miles are more understandable to the majority of passengers.

Nothing more to it than that I would imagine.

kraggy

Hamndegger wrote: »

I'd take land miles per hour anyday over a knot or nautical mile

By and large, people here still trade in miles so I would imagine that it easier for Irish people to take into account over kilometers. Bear in mind that the pilot just gives you that information just as a courtesy, though I take your point; a standard would be nice.

Nautical miles are used precisely because 1nm is a fraction of a particular length on the earth's surface i.e. 1 minute of longitude (1/60 of a degree).

Thus, it is of more use than the statute mile which originated in the distance covered 1000 paces by a Roman soldier. A statute mile has no benefit in terms of navigation.

electric69

kraggy wrote: »

Nautical miles are used precisely because 1nm is a fraction of a particular length on the earth's surface i.e. 1 minute of longitude (1/60 of a degree).

Thus, it is of more use than the statute mile which originated in the distance covered 1000 paces by a Roman soldier. A statute mile has no benefit in terms of navigation.

It still doesnt stop them asking us questions about it!! When it comes to flight planning, for whatever reason, if we are given a distance in sm we still have to be able to convert it to nm for pratical use.

In relation to the OP, was the distance given on the inflight monitors or verbally by the pilot? I would be suprised if he gave the distance in sm, where the monitors are out of his control when it comes to the distance units.

cp251

As a pilot, (non airline) I only use knots and nautical miles. That's what we use. Although perversely the rules for relating to distance from cloud and visibility is given in kilometres. In a weather report (METAR) or a forecast (TAF) for example the wind speed is in knots and the visibility in metres. Cloud heights are in feet.

Essentially the pilot is just looking at his or her readouts and doing a quick mental calculation for speed. The conversion from knots to statute miles is easy, 1 knot = 1.15 statute. Just add 15%, 500 knots is 575 mph. Whereas 1852 metres is a bit more tricky. Not that tricky but the pilot has better things to be doing than mental arithmatic. As for height, no one except the Russians (I think) use metres and that's not likely to change soon.

So miles and feet it is. Pilots, particularly the older ones are a conservative lot and will stick with what they know.

Probably it's also a factor that although you might be well used to kilometres, many if not most people are not. That will change but for now, the likes of me would only be confused if the Captain came on and said we were flying at 10,000 metres and at 700 kilometres an hour. If he said we were flying at 700metres and 10,000 km an hour. I'd swallow that too.:o

One thing on the Km, metres issues. I get really irritated when a aviation documentary comes on, air crash investigation, usually on the Discovery type channels. They alway uses metres for height and kilometres for speed. That's just ridiculous in aviation terms where neither are used. :mad:

highlydebased

Chances are when they are making a PA the only reason they are using miles per hour as its probably all the average joe soap would be able to equate for- many people may have never heard of the knots system.

Personally I'd be happy if they gave groundspeed as groundspeed (and not mph over the ground!)

kraggy

cp251 wrote: »

One thing on the Km, metres issues. I get really irritated when a aviation documentary comes on, air crash investigation, usually on the Discovery type channels. They alway uses metres for height and kilometres for speed. That's just ridiculous in aviation terms where neither are used. :mad:

In that case, using kilometres is down right wrong.

However, regarding height, metres are used in many parts of the world e.g. Russia and South America.

So if said programmes were dealing accident investigations in those regions, then they would be right to use metres.

cp251

That would be fair enough but they use it for all types of scenarios. For example in WW2 documentaries or incident and accidents which happen in the US. Whatever about speed it is completely inappropriate to use metres in altitude because feet is standard throughout international aviation.

Lennoxschips

I don't think knots have much to do with seconds of degrees. The Earth is round, so one degree longitude at the equator is much more distance than one degree in northern Greenland. So the knot would be a different distance depending on your location on the planet. So I doubt that particular definition.

According to Wikipedia, boats used to drop ropes with specifically spaced knots into the sea and then time how long it would take for them to float along in the water behind the ship, or something like that.

L1011

Thats how they *were* defined, how they're *now* defined is to do with rotation.

The land mile varied wildly around the world in the past also. And the meter has been a lump of steel, the speed of a laser in a vacuum, etc, etc.

Lennoxschips

But if they were defined by the distance between lines of longitude then a knot would be a different distance depending on where you are standing on the Earth.

Is there a source for this explanation? I'm genuinely interested.

Lennoxschips

I've found it, it's based on degrees longitude along the Equator.

So not anywhere North/South.

kraggy

Lennoxschips wrote: »

I don't think knots have much to do with seconds of degrees. The Earth is round, so one degree longitude at the equator is much more distance than one degree in northern Greenland. So the knot would be a different distance depending on your location on the planet. So I doubt that particular definition.

According to Wikipedia, boats used to drop ropes with specifically spaced knots into the sea and then time how long it would take for them to float along in the water behind the ship, or something like that.

Don't worry, it's nothing to do with knots tied on a rope. That is indeed the origin of the term but nothing to do with the length of the knot we use today.

I should clarity what I said about a knot. A nautical mile is the distance on the earth's surface subtended by an angle of 1 minute AT THE CENTRE OF THE EARTH. Therein lies the crucial bit. So, each minute is represented almost equally on the earth's surface. 1 minute = 1 nautical mile. Therefore the distance from the equator to either pole is 5400 nautical miles (1x60x90) minus the variation due to the fact that the earth is an oblate spheroid (i.e. is flat on the poles).

Thus, the nautical mile is an AVERAGE Length of the minutes of latitude. The international nautical mile is 6076 feet while the Uk's is 6080 feet.

Lennoxschips wrote: »

I've found it, it's based on degrees longitude along the Equator.


So not anywhere North/South.

No, it's based on distance ALONG a meridian of longitude, which is degrees latitude i.e. from equator to pole.

Victor

cp251 wrote: »

As for height, no one except the Russians (I think) use metres and that's not likely to change soon.

Sweden used to, but not any more.

pclancy

I think as said before its just done for the average joe soap whos used to mph on his car and the only knot he's ever seen is in his shoelaces..."we're crusing at 520mph" always stirs a little "jaysus molly did you hear dat? we're feckin flyin it" in the cabin of an EI flight

ImDave

cp251 wrote: »

One thing on the Km, metres issues. I get really irritated when a aviation documentary comes on, air crash investigation, usually on the Discovery type channels. They alway uses metres for height and kilometres for speed. That's just ridiculous in aviation terms where neither are used. :mad:

+1 That really irratates me aswell. They spend thousands making those programmes as realistic as possible, and then go around given rates of desent in meters per second etc.

Our man in Havana

More annoying is you can hear the pilots talking in feet and knots on the cockpit voice recorders but Nat Geo simply over dub it with meters and kilometers.

I see those shows are made a Canadian company which might explain the meters and Km setup.

pclancy

Also the cockipts they depict are often nothing like the airplane in question. Control collums in an airbus anyone?

cp251

I have a suspicion that the figures in the original version is probably in imperial measures but when they dub it with a British narrator they convert it to metric. Probably the reason is that those channels are broadcast throughout Europe. It's still irritating though.

I don't mind them getting details of the cockpits wrong so much. In truth I imagine the makers wouldn't get much cooperation from the airlines themselves for the making of the documentaries. I was involved in one air crash recreation for TV. It was quite amusing as we pretended we were crashing. At least the aircraft type was correct.;)

spacetweek

cp251 wrote: »

Essentially the pilot is just looking at his or her readouts and doing a quick mental calculation for speed. The conversion from knots to statute miles is easy, 1 knot = 1.15 statute. Just add 15%, 500 knots is 575 mph. Whereas 1852 metres is a bit more tricky. Not that tricky but the pilot has better things to be doing than mental arithmatic.

I don't buy this at all. Why is increasing by 85% too much mental arithmetic, but increasing by 15% is OK?

cp251 wrote: »

As for height, no one except the Russians (I think) use metres and that's not likely to change soon.

It's true that feet or the local word for it is used pretty much worldwide for safety reasons (and the English language), but that doesn't mean you say that to the passengers. The measurement should be converted to the one which is most widely understood, which is metres.

cp251 wrote: »

So miles and feet it is. Pilots, particularly the older ones are a conservative lot and will stick with what they know.

It's not conservatism that's preventing change in this case; it's the fact that pilots (and air traffic controllers) are highly trained and it could be dangerous to disrupt their training, because lives are at stake.

EI-DAV wrote: »

+1 That really irratates me aswell. They spend thousands making those programmes as realistic as possible, and then go around given rates of desent in meters per second etc.

That's not right. In practice, it's irrelevant what's used by the specially trained people involved. You convert for the audience - nobody knows what "ascending at 8 FPS" means. See above.

FlutterinBantam

FlutterinBantam wrote: »

Take the macro view there son,obviously the pilot thinks the miles are more understandable to the majority of passengers.

Nothing more to it than that I would imagine.

exactly as I said days ago..

ArphaRima

Mph and feet 90% of the time. Unless in Eastern Europe where many like to hear height in metres and kph.

China still uses Metres for height. Metres per second for windspeed as opposed to knots is also fairly common in ex-communist bloc places.

electric69

fluffer wrote: »

China still uses Metres for height. Metres per second for windspeed as opposed to knots is also fairly common in ex-communist bloc places.

I think most of that is being fazed out due to our altimeters only reading in ft and R.O.D being measured in ft/min aswell. not much help when atc in china tells u to fly a certain heading in meters when ur coming from america / europe. I know the russians are still using meters and it doesnt look like they will change any time soon. At least they all have to speak english