What are the effects of headwind strength on landing?

Question

Assuming a direct headwind with zero crosswind component, what are the effects of landing into say a 10kt vs 30kt vs 50kt headwind? Are there any specific advantages or drawbacks to a stronger headwind when landing? Are there any specific procedures that kick in when the headwind exceeds a certain number for a certain aircraft?

I don't know if aircraft type matters much in answering this question, though I realize that small aircraft could potentially encounter a headwind that is faster than the recommended landing speed, thus making it difficult to reach the runway in the first place. Let's leave that situation out of the answers - assume that the wind is slower than the recommended landing speed.

I understand that landing into a headwind is the preferred option, and that tailwind landings are possible up to certain limits.

I understand that crosswind makes the landing more challenging and that there are limits to the crosswind component. Assume a direct headwind for this question.

I understand that a headwind makes ground speed slower for a given quantity of lift, but that's irrelevant to anyone but the passenger anxious to make his connection.

Assume a fairly steady wind with minimal gusting - at a level most pilots wouldn't be concerned with. (Unless, of course, gusts make a more or less significant difference based on steady-stream speed.)

Update:

This seems to be a fairly difficult question. I get the fact that, in practice, the above conditions are likely never going to be met, this is more of a theoretical question - assuming a direct headwind, assuming near zero gusting, assuming "significant" differences in headwind (in relation to the aircraft's landing speed - a C152 with one on board will land slower than a fully loaded A380). These are combinations that will probably never happen outside a wind tunnel, but I'm sure someone, somewhere has thought about them.

Answer 1

Are there any specific advantages or drawbacks to a stronger headwind when landing?

A strong headwind right down the runway can appreciably shorten your landing roll, if you want to do that. If you want to clear the runway as soon as conveniently possible, you might be able to take a taxiway closer to touchdown than you otherwise would.

Or, let's say the taxiway that is closest to your gate is 3/4 or more down the runway, so what you might do in a strong headwind would be to not use reverse, or just go into reverse but not bring the power up. What you don't want to do, at least at busy airports, is tie up the runway at a taxi speed.

Some have contended that a strong headwind, with the resulting lower groundspeed, makes for a slightly smoother landing because the tires don't have to spin up as much. I don't have an opinion on that.

A strong headwind can mean that brake temperatures on arrival at the gate will be lower than otherwise, both because of less brake usage on rollout and better ventilation of the brakes while taxiing.

Are there any specific procedures that kick in when the headwind exceeds a certain number for a certain aircraft?

I've never heard of such specifically for a headwind, or at least I don't remember ever hearing of such.

Answer 2

This is from the viewpoint of a learner/novice pilot where landings are still a challenge.

Are there any specific advantages or drawbacks to a stronger headwind when landing?

Consistent and even headwind landings are lower risk and easier to do than no wind at all. Damage to aircraft and their passengers is caused by the difference in velocity between the aircraft and the ground. When landing in a strong even headwind you still have the same vertical descent speed but a dramatically reduced horizontal speed along the runway. This means that if anything goes wrong (plane not perfectly lined along the runway, landing a bit heavily etc) the ability to retain control and transition to running along the runway on your wheels is much easier. In the event of a loss of control and coming off the runway and hitting anything or indeed hitting an unexpected object on the runway the relative velocity of your plane to the stationary object involved is much less meaning less energy in the crash, less damage to everything involved and better chances of personal survival.

Also as you often are trying to keep to the same rough angle of descent you will often come in with a bit more power on which when the prop is in front of the wings increases airflow over the control surfaces making the aircraft a bit more responsive.

As a learner pilot in a little Cessna 152 (landing at about 60 knots) I greatly enjoyed a few days I got doing circuits (landing practice) with a nice strong steady 20 knot headwind as it allowed me to worry less about the wheels being perfectly ready to transition to trundling along the runway. 40 knots relative to the ground feels really slow and with a long runway that is going past slowly you have more time to focus in on getting the flare nice and accurate and touching down gently.

I did put the caveat on "consistent and even headwinds" as the reality is that stronger winds are usually more variable than weaker winds. It is not as easy if the headwind is varying by +-10 knots which is a lot more likely when the average is windspeed is 20 knots than when the average windspeed is 5 knots.

Are there any specific procedures that kick in when the headwind exceeds a certain number for a certain aircraft?

As implied above when the windspeed approaches the landing speed of the aircraft you need to apply power on descent to maintain an appropriate angle of approach. Otherwise you end up descending vertically onto the threshold.

Answer 3

Are there any specific advantages or drawbacks to a stronger headwind when landing?

As for drawbacks, a stronger headwind generally means a stronger headwind gradient. This means that for a given power setting and airspeed, the aircraft will tend to have a higher sink rate near the ground.¹ In a worst-case scenario, the aircraft may simply not have enough airspeed for a flare that adequately arrests this sink rate-- one solution is to maintain extra airspeed throughout the last part of the final approach, and then bleed it off very near the ground, but preferably not in an abrupt "flare" maneuver (read on for why not).

A strong wind gradient also means that any accidental ballooning upwards due to an excessive flare² will tend to be more pronounced, after which the airplane will tend to plummet downwards due to the effect described above.

I fly radio-controlled model airplanes as well as "real" airplanes, and those lightweight aircraft (little "foamies") are very prone to wind gradient effects. In light to moderate winds, I usually have smoother landings when landing downwind than upwind, due to the effects described above. (I don't land "real" airplanes downwind.)

Hang glider pilots who "flare"³ to reduce groundspeed to land on safely their feet are also very familiar with these effects-- and generally reserve a strong "flare" only for no-wind or light-wind situations, to avoid this "ballooning" effect-- though the dynamics are complicated by the fact that there's no need to flare hard enough to greatly alter the groundspeed when landing into a strong headwind anyway, since you generally don't want to touch down with a negative groundspeed, i.e. going backwards.

Footnotes:

1. Assuming that we're talking about a power setting and airspeed that would result in a positive sink rate (negative vertical speed) in still air, i.e. in the absence of any wind gradient.

2. Also pertains to an accidental upward "bounce" into the air after wheels contact the ground.

3. The type of "flare" used in a light-wind or no-wind landing with a hang glider is very different from what we use in airplanes to simply arrest the sink rate-- it is a dynamic maneuver that uses the inertia of the pilot's body to rapidly put the wing at an extremely high (stalled) angle-of-attack that results in a rapid loss of airspeed and groundspeed. Improperly timed or improperly executed, it can cause the glider to climb slightly-- or more than slightly.