Welcome Guest. Sign in or Signup

6 Answers

Headwind vs. Tailwind

Asked by: 3867 views Aerodynamics

Hello,

Reading Chapter 12 of FAA's PHAK book, I came across this statement, "A tailwind quickly changing to a headwind causes an increase in airspeed and performance.
Conversely, a headwind changing to a tailwind causes a decrease in airspeed and performance."

Can someone please explain this to me? I thought tailwinds increased your speed during cruise portion of flight and vice versa. 

Thank you,

Nima

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

6 Answers



  1. Mark Kolber on Dec 11, 2020

    I’ll leave more technical explanations to others. It’s the difference between airspeed and ground speed. When you talk about a tailwind increasing speed, that’s speed over the *ground*, not aircraft performance.

    What the PHAK is talking about is a sudden change in wind direction – wind shear. With that in mind, question back to you: You are on final. The wind quickly changes from a headwind to a tailwind. What happens?

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  2. Nima on Dec 11, 2020

    Hi Mark,

    Thank you for your answer and explanation. To answer your question, if the wind quickly changes from a headwind to a tailwind on final, one would lose speed, lift, and sink. That is why I think it is safer to fly a bit faster with headwind gusts but I could be wrong. Thanks again.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  3. Paul H. on Dec 11, 2020

    Think about the momentum and inertia of your aircraft.

    You’re going 100 kias against a 10 kt headwind. You have 100 knots of wind over your wings, holding you up.

    Suddenly, that headwind changes to a 10 kt tailwind. Instantly, you only have 80 knots of wind over your wings.

    Yes, over the course of several seconds at the same power setting your plane will speed up and regain an indicated airspeed of 100 kias.

    Yes, once this change has happened your ground speed will be 20 knots faster, making the tailwind a good thing.

    During those several seconds, though, your airspeed has suddenly dropped from 100 kias to 80. Your plane will be sinking.

    Now imagine it when you’re on final, going maybe 70 kias. 10-knot headwind shifting to 10-knot tailwind drops your indicated airspeed to 50 kias, and if you don’t change power settings quickly, you’re dropping like a rock, at or near stall speed. Those several seconds it takes for your airplane’s momentum and inertia to allow a rebalance of thrust and drag are more seconds than you can really afford. You’ll have to make fairly quick adjustments to pitch and power to stay anywhere near your approach profile.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  4. Mark Kolber on Dec 12, 2020

    Answering my question answered yours. too, didn’t it?

    That loss of airspeed and lift is the reason why on with reported gusts (which can change from headwind to tailwind to headwind to tailwind….) , we add 1/2 of the gust factor to our landing speed.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  5. Nima on Dec 12, 2020

    Thank you Mark and Paul for the thorough explanations. It now makes sense.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  6. Mackey on Dec 13, 2020

    100 KIAS –10K Head Wind= 90K ground speed.
    100 KIAS + 10K tail wind = 110K ground speed.
    110K–90K = 20K

    0 Votes Thumb up 0 Votes Thumb down 0 Votes


The following terms have been auto-detected the question above and any answers or discussion provided. Click on a term to see its definition from the Dauntless Aviation JargonBuster Glossary.

Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.