Jump to content
Sign in to follow this  
Nick Dobda

what to do with wind info just prior to takeoff

Recommended Posts

When getting cleared for takeoff and landing, ATC recites the latest wind info. What do we do with this info? Is it just a mental note? Are we supposed to enter that into the FMC (takeoff)? Surely we don't have time to recalculate the thrust settings... is there some range the pilot is looking for to stay within to ensure the takeoff setting are still valid? What if the winds change enough to warrant recalculating takeoff settings? Does he pull the plane aside and tell ATC to hold up while I reconfigure? Does that ever happen?

Share this post


Link to post
Share on other sites

 

 


Is it just a mental note?

 

Yep.

 

The rest of the questions are overthinking it, really. If the wind changed that drastically, you might want to call your meteorology/planning department to have a discussion about forecasting and quality.


Kyle Rodgers

Share this post


Link to post
Share on other sites

Thanks, I wasn't sure I was kind of disregarding the info trusting the weather info ASN told me and was used in takeoff configuration was accurate (especially in a sim considering ASN is generating the weather). For landing, I was pretty sure it was FYI cause there's nothing to program and you react to whatever comes your way on the approach with control inputs. 

Share this post


Link to post
Share on other sites

 

 


For landing, I was pretty sure it was FYI cause there's nothing to program and you react to whatever comes your way on the approach with control inputs. 

 

Correct. Just as with takeoff, it's just a cursory check to give you the latest wind that you will have to adjust to.*

 

Not everything needs to go into the FMC. It's possible to fly an entire flight in the 737 and ignore the thing entirely. It certainly makes life a lot easier, but remember that it's a tool to assist you and not a tool to bind you.

 

 

 

*Side note: If a departure procedure says "fly runway heading," then you should not adjust your heading to track down the extended centerline. If the runway course is 191, then you should put your aircraft's nose on 191. If everyone is flying heading 191 on departure, they will all drift at about the same rate, relieving all of the crews of having to worry about wind correction.


Kyle Rodgers

Share this post


Link to post
Share on other sites

 

 


but remember that it's a tool to assist you and not a tool to bind you.

 

Yeah, I get that. Takeoffs though its cool to use up all the runway available instead of gunning it on takeoff. Miscalculating on the takeoff mode and derates could obviously lead to some problems. Like you said though for weather to change enough to become a problem between the gate and the runway is extreme and unlikely.

Share this post


Link to post
Share on other sites

It's a bit more than a mental note in so far as if you have company crosswind/tailwind limits and the tower reported wind was outside of those then you would be rather brave to disregard it.

 

It's slightly different in the sim because the only weather info we have is the METAR, which is (IIRC) the 10-minute average wind just prior to the METAR being published. The wind you get from the tower, on the other hand, in real life is much more current -- again IIRC usually more like a rolling 2-minute average or if requested the 'instant' wind direct from the anemometer is also available. Both of these values could be significantly different to the METAR in changeable conditions (especially if it's been a while since it was published).

  • Upvote 1

Share this post


Link to post
Share on other sites

 

 


The wind you get from the tower, on the other hand, in real life is much more current -- again IIRC usually more like a rolling 2-minute average or if requested the 'instant' wind direct from the anemometer is also available.

 

Those are the two most common. I know some of the older towers here in the States read right off of the anemometer (what the 7110 refers to as the "direct readout dial") since that's just about all they have, but the automated weather system information display is also an option (similar to what many FBOs have on display somewhere in the building). The additional option allowed by the 7110 is a reading off of the windshear detection system.

 

All are much better than what you get in the sim, as you noted.


Kyle Rodgers

Share this post


Link to post
Share on other sites

You could enter the wind info on the 2nd page of the takeoff page in the fmc. But, yes as Kyle stated, it's a mental note so you know on the takeoff roll how much to correct for wind - David Lee

Share this post


Link to post
Share on other sites

And... don't forget, the meteo man always says the TRUE ( wind )....

 

Just as winds reported in METAR, SIGMET, TAF are TRUE.

 

We never lie!

 

Since within the USA it can var as much as 25W and 20E at some airfields, this can really be significant, and you'd better make your mental conversion :-)


Main Simulation Rig:

Ryzen 5600x, 32GB RAM, Nvidia RTX 3060 Ti, 1 TB & 500 GB M.2 nvme drives, Win11.

Glider pilot since October 1980...

Avid simmer since 1992...

Share this post


Link to post
Share on other sites

 

 


And... don't forget, the meteo man always says the TRUE ( wind )....
 
Just as winds reported in METAR, SIGMET, TAF are TRUE.

 

But not when given by the tower (which is magnetic)!

 

Generally speaking -- if it's spoken it's magnetic, if it's written it's true.

Share this post


Link to post
Share on other sites

The meteo man isn't at the tower.... :-)  but we're not far, usually...


Main Simulation Rig:

Ryzen 5600x, 32GB RAM, Nvidia RTX 3060 Ti, 1 TB & 500 GB M.2 nvme drives, Win11.

Glider pilot since October 1980...

Avid simmer since 1992...

Share this post


Link to post
Share on other sites

Yeah, it's advisory but a good cross check on actual conditions as you start your roll. For instance, if your takeoff data is just predicated on no headwind, but the wind direction shifts a bit and the reported takeoff wind now contains a small tailwind component, your takeoff data is now technically invalid. Are you going to decline the takeoff clearance and taxi clear to get new data? On a 12000ft runway, at sea level, with a 2 kt tailwind? Well... do you have a fed in the jumpseat? :-D

 

On the other hand, on a 5,000ft, wet runway that ends in saltwater? Yeah maybe!


Andrew Crowley

Share this post


Link to post
Share on other sites

Since within the USA it can var as much as 25W and 20E at some airfields, this can really be significant, and you'd better make your mental conversion :-)

 

Tower controllers apply the correction here in the States.


Kyle Rodgers

Share this post


Link to post
Share on other sites

You might also be limited by the winds. If you're really pushing the limits, you might be looking for a minimum headwind or maximum tailwind. There could also be crosswind limits based on less than good braking action.

 

Nothing to do with the FMC, really.


Matt Cee

Share this post


Link to post
Share on other sites

Nice little cross check.

ie:
1: Prepare for your departure, get ATIS and clearances and stuff. Check the wind with topcat etc for V speed calculations

"Hey look, runway 19, wind 180 at 10 knots"

2: Tower tells you the actual winds just before takeoff

"ABC123 wind 180 at 15 knots, Runway 19 cleared for takeoff"

"Hmm that didn't match, but it's still fine. Let's takeoff."

 

or

"ABC123 wind 280 at 30 knots gusting 45, Runway 19 cleared for takeoff"

"hmm that REALLY didn't match at all! 280 - 190 = 90. That's all crosswind. aww this sux.

 

or

"ABC123 wind 340 at 30 knots gusting 45, Runway 19 cleared for takeoff"

"hmm that REALLY didn't match at all! 340 - 190 = 250. 240>90. A bunch of that is tailwind. a 30 to 40 knot tailwind is out of limits. We might need to say no to runway 19! Why didn't they give use 01? what's going on? I want no part in this crash waiting for a place to happen! Let's say no, and run our numbers again or double-check if they want to change their runway."

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
×
×
  • Create New...