I'm just making sure I got this right.
For the take-off roll, having headwind is preferable, so there is a positive airspeed.
For the en-route segment, a headwind is not ideal and increases time to destination, whereas a tailwind is more favorable.
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6$\begingroup$ Yes, that is about right. Is there a question? $\endgroup$– Ron BeyerCommented Jun 27, 2016 at 20:13
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2$\begingroup$ So you are asking if what you are thinking is correct? $\endgroup$– SMS von der TannCommented Jun 27, 2016 at 20:40
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$\begingroup$ You're doing it wrong. $\endgroup$– Ryan MortensenCommented Jun 28, 2016 at 0:30
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2$\begingroup$ @RyanMortensen: How should your comment be understood unless you explain what is wrong? I see two correct statements here (head wind for landing and tail wind for cruising are usually seen as positive by the pilot) $\endgroup$– minsCommented Jun 28, 2016 at 9:10
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$\begingroup$ @mins you're being too literal. Forget I said anything... I was referring to how to ask questions. Not the statements contained. $\endgroup$– Ryan MortensenCommented Jun 28, 2016 at 13:42
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1 Answer
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Short Answer: Yes, you have it right.
For a longer answer consider an example aircraft that has the following characteristics:
- Takeoff Speed: 60 knots (Indicated Airspeed)
- Landing Speed: 50 knots (Indicated Airspeed)
- Cruise Speed: 100 knots (Indicated Airspeed)
Note that all the speeds are airspeeds, which are what we usually measure in flight.
To find the groundspeed you add or subtract the effect of wind, which will become important as you'll see:
A headwind gives the plane a lower groundspeed for a given airspeed.
If our example airplane has a 10-knot headwind it has the following practical effects:
- On takeoff the aircraft only has to gain an additional 50 knots to reach takeoff speed:
It effectively has a 10-knot "bonus" from the headwind, and will thus reach takeoff speed in a shorter distance, and need less runway. - Once in the air the headwind works against the aircraft's progress: The groundspeed of the aircraft is equal to its airspeed minus the headwind, so while you're cruising at 100 knots airspeed you're only making 90 knots over the ground. A 100-mile flight will take an extra 7 minutes to complete.
- On landing the aircraft will arrive at the runway with a 50-knot indicated airspeed, but because of the headwind will be making 40 knots across the ground. It will thus have less energy to get rid of once it lands, and will require less runway to slow to a stop.
A tailwind gives the plane a higher groundspeed for a given airspeed.
If we reverse our earlier example and give the aircraft a 10-knot tailwind it has the following effects:
- On takeoff the airplane must accelerate to a 60-knot airspeed, however it's also being pushed along by a 10-knot tailwind, so it effectively has a -10 knot airspeed standing still: The wind is blowing forward over the wings. When it reaches its 60-knot takeoff speed it will have a 70-knot groundspeed because it's being pushed along by the wind, so it will have a longer takeoff roll.
- In cruise the wind continues pushing our example airplane along, so its 100-knot cruise speed gives it a 110-knot ground speed. A hypothetical 100-mile trip would take a little over 54 minutes.
- On landing the aircraft arrives with a 50-knot indicated airspeed, but a groundspeed of 60 knots (the wind is still pushing it along), so it will have more energy to dissipate when it lands: A longer ground run, and more braking required.
A chart of the effects of headwinds and tailwinds on takeoff and landing can be found in the Pilot's Handbook of Aeronautical Knowledge, it's reproduced below.
Effects of winds in cruise can be calculated using an E6B Flight Computer
