Jump to content

#### Archived

This topic is now archived and is closed to further replies.

# headwind component calculation?

## Recommended Posts

Hi all,How is the headwind component of a crosswing calculated for Vref or Vapp? Thanks,Christos

#### Share this post

##### Link to post

It pretty much has no effect. Either with no wind, or a 20 knot headwind, you are still going the same airspeed, putting the same amount of air over the wings. The thing that changes is the groundspeed. If you land at 140 knots with no wind, you touch down at 140 knots, but if you have a 20 knot headwind, you land at 120 knots groundspeed.The equation for all of this is...0.5*(("Approach Airspeed"+"Head/Tailwind")*1.6878)*((("Approach Airspeed"+"Head/Tailwind")*1.6878)/"Autobrake Decellaration Rate")+1000 ^Glideslope is 1000 feet beyond threashold.

#### Share this post

##### Link to post

Vapp = Vref + correctionCorrection = half hw component + full hw gust component, min 5kt , max 20ktHeadwind component:

` 	|\  hw    |a\ wind speed 	|__\	xwa = angle between runway and wind directionHigh School trignometrycos a = hw / wind spdhw = wind spd * cos a`

Sample problem

`Runway heading 340Wind reported at 300/10-20Vref = 130ktAngle btn Runway and Wind, 'a' = 40degSteady Wind Speed, 'w1' = 10ktGust Component, 'w2' = 20kt - w1 					= 20kt - 10kt 					= 10ktSteady HW component = w1 * cos a                    = 10 * cos 40                    = 8ktGust HW component = w2 * cos a                  = 10 * cos 40                  = 8ktVapp = Vref + 1/2 (Steady HW Component) + Gust HW Component 	= 130kt + (8kt / 2) + 8kt 	= 130kt + 4kt + 8kt 	= 142kt`

Hope that helps!Nick Jones

#### Share this post

##### Link to post

Thanks asdf987, very good.This was exactly what I needed.Happy landings!Christos

#### Share this post

##### Link to post

Great stuff asdf987.

#### Share this post

##### Link to post

Actually, in the FMC of the 744X both crosswind and tail/headwind components are shown. I think is page 2 of the Progress menu. I don´t know about the others PMDG planes.

#### Share this post

##### Link to post

Felipe,We need to consider approach winds, rather than the cruise winds that would be displayed in the progress page, as we set up the arrival prior to top of descent.Cheers,Nick Jones

#### Share this post

##### Link to post
• Tom Allensworth,
Founder of AVSIM Online

• ### Hot Spots

• 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.
• ### Donation Goals

AVSIM's 2019 Fundraising Goal

Donate to our annual general fund. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.

68%
\$24,820.00 of \$36,000.00 Donate Now
×
×
• Create New...