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Wind Data From Commerical Aircraft At High Levels  
User currently offlineJulesmusician From , joined Dec 1969, posts, RR:
Posted (8 years 9 months 1 week 3 days 3 hours ago) and read 2744 times:

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]

11 replies: All unread, jump to last
 
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17038 posts, RR: 66
Reply 1, posted (8 years 9 months 1 week 3 days 3 hours ago) and read 2738 times:

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.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineLoggat From United States of America, joined Feb 2000, 666 posts, RR: 0
Reply 2, posted (8 years 9 months 1 week 3 days 2 hours ago) and read 2730 times:

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.
User currently offlineModesto2 From United States of America, joined Jul 2000, 2801 posts, RR: 5
Reply 3, posted (8 years 9 months 1 week 3 days 2 hours ago) and read 2715 times:

Many navigation displays (such as 747-400, 757, 767, 777, A320, A330, A340) display wind speed and direction.

User currently offlineAAR90 From United States of America, joined Jan 2000, 3474 posts, RR: 46
Reply 4, posted (8 years 9 months 1 week 3 days 1 hour ago) and read 2709 times:

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.


*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 5, posted (8 years 9 months 1 week 3 days 1 hour ago) and read 2701 times:


View Large View Medium
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



Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 6, posted (8 years 9 months 1 week 3 days 1 hour ago) and read 2696 times:

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!!!


User currently offlineLoggat From United States of America, joined Feb 2000, 666 posts, RR: 0
Reply 7, posted (8 years 9 months 1 week 3 days ago) and read 2682 times:

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.
User currently offlineModesto2 From United States of America, joined Jul 2000, 2801 posts, RR: 5
Reply 8, posted (8 years 9 months 1 week 2 days 22 hours ago) and read 2659 times:

Side note but...what are the dotted arcs across the ND in that pic above?

User currently offlineCX flyboy From Hong Kong, joined Dec 1999, 6601 posts, RR: 55
Reply 9, posted (8 years 9 months 1 week 2 days 22 hours ago) and read 2655 times:

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.


User currently offlineWoodreau From United States of America, joined Sep 2001, 1040 posts, RR: 6
Reply 10, posted (8 years 9 months 1 week 2 days 12 hours ago) and read 2591 times:

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)


Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
User currently offlineAAR90 From United States of America, joined Jan 2000, 3474 posts, RR: 46
Reply 11, posted (8 years 9 months 1 week 2 days 10 hours ago) and read 2570 times:

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 .



*NO CARRIER* -- A Naval Aviator's worst nightmare!
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