Miles & NM
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Miles & NM
When I was working in final approach area , I would like to say: "XXX maintain 180 KTS until 7 NM from touchdown ." Nearly all the pilots prefer to use "maintain 180KTS until7 MILES from touchdown ."When it was my first time to meet this situation , I repeat the NM again and pilots said "affirm 7 MILES "
I know there is a small difference between miles and NM ,but once the plane could not stop on the runway ,that is the accident.What do you usually say ? Shall I use KM instead of NM or mile ?
I know there is a small difference between miles and NM ,but once the plane could not stop on the runway ,that is the accident.What do you usually say ? Shall I use KM instead of NM or mile ?
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Since all the aircraft systems are working to nautical miles, you can say "miles" and it will mean "nautical miles". Statute Miles are not, as far as I know, a recognised unit of distance for aviation purposes.
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Correct me if I'm wrong.....ICAO standards are NM for tracking distances, km for reporting vis and runway lengths, feet for altitude.....
If you are party to ICAO recommended practices then there's no ambiguity.
Ohcirrej
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Originally Posted by timelapse
Don't american METARS have vis in statute miles?
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As far as I'm aware, all countries use nm for navigation. I doubt there's much chance of confusion, since the FMS,GPS,IRS,INS...all use nm.
As for METARS, I've long wondered why they don't give visibility in nm instead of km/sm. Of course, this would be reduced to ft/m as necessary
As for METARS, I've long wondered why they don't give visibility in nm instead of km/sm. Of course, this would be reduced to ft/m as necessary
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I understood that a nautical mile always indicated a horizontal distance across the earth's surface at sea level, in theory one minute of latitude - great for navigation.
Other units of distance - km, miles, feet etc can be used for point to point distances in any direction - if you stick with the icao standards it is difficult to go wrong.
The only time DME miles = nautical miles is at sea level, although the differences for an ILS approach altitudes are minimal.
Other units of distance - km, miles, feet etc can be used for point to point distances in any direction - if you stick with the icao standards it is difficult to go wrong.
The only time DME miles = nautical miles is at sea level, although the differences for an ILS approach altitudes are minimal.
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Not quite true Miraz. 1 NM is the "distance bisected by 1 minute of arc at the earth's surface", so the NM is exactly the same size whatever height you're at. A NM is a NM is a NM, which is why it's ideal for navigation. A DME mile is equal to a NM all the time, but if you're at FL350 you still have to take slant range into account. If you're flying an ILS approach, slant range doesn't really matter because the DME is where you want to be i.e. on the ground!
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Correction:
1 NM is the distance described on the Earth's surface by 1 minute of arc from the earth's centre at the equator.
Our home planet (well, for many of you!!) is an oblate spheroid; so, 1 minute of arc on any Great Circle (except the equator) COULD be different in actual length.
NMs SMs KMs.... all Dutch to me: just don't let 'em bump into each other!!!!!
Ho-hum: off to the sheep pasture
POC
Our home planet (well, for many of you!!) is an oblate spheroid; so, 1 minute of arc on any Great Circle (except the equator) COULD be different in actual length.
NMs SMs KMs.... all Dutch to me: just don't let 'em bump into each other!!!!!
Ho-hum: off to the sheep pasture
POC
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'zachary
But what's a "mile"? NM or SM.
Pecanticity will out!
"At 75DME descend to ...... ": solve the problem?? Probably not for the kilometricos!!??
"At 75 DME NMs or 77.67 DME SMs or 117.4 DME KMs, descend to ....."
There must be a table somewhere to make it this easy!
Over and out!
Pecanticity will out!
"At 75DME descend to ...... ": solve the problem?? Probably not for the kilometricos!!??
"At 75 DME NMs or 77.67 DME SMs or 117.4 DME KMs, descend to ....."
There must be a table somewhere to make it this easy!
Over and out!
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But what's a "mile"? NM or SM.
Pecanticity will out!
"At 75DME descend to ...... ": solve the problem?? Probably not for the kilometricos!!??
Pecanticity will out!
"At 75DME descend to ...... ": solve the problem?? Probably not for the kilometricos!!??
My head hurts
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75DME means 75 nautical miles DME since DME receivers only work on nautical miles
but saying 160 knots to 4 miles means to 4 Nautical miles
since on an ILS approach the ILS is paired to a DME there is no need to specify that the miles you mean are nautical
Assumptions can be dangerous things.
I'm catching the headache!
PS - Titan, take a look at Annex 5.