julesmusician
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Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 6:52 am

How easy is it for pilots of commercial aircraft to find out the wind speed they are in - is it just a matter of pressing a button and the computer will tell you or do you have to do some calculations yourself? The reason is I have heard air traffic ask pilots and they come up with the answer straight away so I assume it must be on a readout on one of the computers?

J

[Edited 2005-12-11 22:53:39]
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
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Starlionblue
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 7:16 am

Quoting Julesmusician (Thread starter):
How easy is it for pilots of commercial aircraft to find out the wind speed they are in - is it just a matter of pressing a button and the computer will tell you or do you have to do some calculations yourself? The reason is I have heard air traffic ask pilots and they come up with the answer straight away so I assume it must be on a readout on one of the computers?

Basically, and I am sure the pilots will enlighten us, two data sources are used:
- GPS and/or inertial guidance (laser gyros) give data on ground speed.
- The pitot static system gives data on air speed.

Onboard systems figure out the difference and thus wind direction and speed. All at the click of a button.
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loggat
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 7:37 am

It's a simple readout from the FMS. Looks at your true airspeed, compares with your groundspeed and then couples it with your crab angle (heading vs. track) to come up with a speed and direction of the wind.
There are 3 types of people in this world, those that can count, and those that can't.
 
modesto2
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 8:23 am

Many navigation displays (such as 747-400, 757, 767, 777, A320, A330, A340) display wind speed and direction.
 
AAR90
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 8:37 am

If not being displayed on a screen at all times (most newer FMS'), it is a matter of a few keystrokes (non-FMS or earliest FMS acft) to see a wind display.
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speedracer1407
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 9:14 am


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Click here for bigger photo!

Photo © TriplET



Quoting Starlionblue (Reply 1):
Basically, and I am sure the pilots will enlighten us, two data sources are used:
- GPS and/or inertial guidance (laser gyros) give data on ground speed.
- The pitot static system gives data on air speed.

Onboard systems figure out the difference and thus wind direction and speed. All at the click of a button.

Incredible systems, these things. But, I can't quite get my head around how the system would accurately calculate wind direction, especially if it were changing all the time. Perhaps my lack of knowledge of the pitot static system is the culprit here.

O
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PhilSquares
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 9:21 am

Quoting AAR90 (Reply 4):
If not being displayed on a screen at all times (most newer FMS'), it is a matter of a few keystrokes (non-FMS or earliest FMS acft) to see a wind display

On every "glass" aircraft I've flown, the wind is depicted on the ND. So, no keystrokes required at all!!!
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loggat
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 10:21 am

Quoting Speedracer1407 (Reply 5):
Incredible systems, these things. But, I can't quite get my head around how the system would accurately calculate wind direction, especially if it were changing all the time. Perhaps my lack of knowledge of the pitot static system is the culprit here.

O

Sorry to have to quote myself from this thread, but this should explain it....

Quoting Loggat (Reply 2):
Looks at your true airspeed, compares with your groundspeed and then couples it with your crab angle (heading vs. track) to come up with a speed and direction of the wind.
There are 3 types of people in this world, those that can count, and those that can't.
 
modesto2
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 11:55 am

Side note but...what are the dotted arcs across the ND in that pic above?
 
CX Flyboy
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 12:11 pm

The dotted arcs are just a visual aid to help the pilots of they want. You can put any waypoint or airport in the FIX page, and then draw an arc of any distance around it. Usually we do it around some airports just to let us know what we are within X miles of it.

For example, if we do an ETOPS flight, anything outside 60 mins is in the ETOPS sector. We take 60 mins to mean 434miles, so we can draw a 434nm circle around our ETOPS airports, and then it is very easy to see when we are within the 60 mins, or outside it.

Certain airports may have a speed restriction upon arrival of say 250kts within 40 miles of the airport, so we can draw a 40 mile circle around the airport and it helps us with our speed reduction planning. A versatile and helptul tool.

In the photo, the pilots have drawn the circles to just overlap, so they know when they are flying along whether they are closer to the airport infront, or the one they have already passed.
 
Woodreau
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RE: Wind Data From Commerical Aircraft At High Levels

Mon Dec 12, 2005 10:32 pm

I've also used the FIX page to draw a circle around a VOR/NDB to do the procedure turn. You're supposed to stay within a certain distance of the NAVAID (usually 10nm). At 200kts, the 10nm comes up pretty quick, so the circle helps in the few times you get to do a full procedure instrument approach (usually in the sim)
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AAR90
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RE: Wind Data From Commerical Aircraft At High Levels

Tue Dec 13, 2005 12:15 am

Quoting PhilSquares (Reply 6):
On every "glass" aircraft I've flown, the wind is depicted on the ND. So, no keystrokes required at all!!!

Shhhh.... now you're really making me feel old .
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