Is there a tailwind limit while in cruise?

Question

The storm Ciarán is, as of posting, making its way through the Atlantic Ocean with winds easily passing 300 km/h (161 kts).

While this is going on, a BA flight took only 8 h 45 mins to do LAS-LHR with a tracked speed peaking at 1200 km/h (~mach 0.98).

I know that, for landing, tailwind, must not exceed a certain value...

Is there such a limit to how much tailwind a cruising plane can experience?

"Mach" values are really only appopriate for airspeeds, not groundspeeds. (Unless you are trying to imply that the groundspeed of the aircraft was .98 the groundspeed that a sound wave would have, moving in the same direction as the plane, at the same altitude, under the same conditions.... but that's just a complicated way of saying that the airspeed was .98 Mach.) — quiet flyer, Nov 01 '23 at 23:28
Related: Can a jet stream make a subsonic plane fly at a supersonic speed relative to the ground? — Bianfable, Nov 02 '23 at 07:26

score 25 · Accepted Answer · 2023-11-01T17:08:13.950

25

The airplane is flying within an envelope of air and operates at its normal "indicated" airspeed (typically mach number while at cruise). The envelope of air itself can be traveling at any speed, but since the airplane is only flying within that envelope a tailwind contributes only to an increase in ground speed (hence the tailwind limitations on takeoff and landing).

So, unless there are other circumstances impacting the airplane because of an extremely strong tailwind (turbulence, etc.), there is no limitation with respect to the speed of a tailwind during cruise.

edited Nov 01 '23 at 17:08

answered Nov 01 '23 at 16:36

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Or on extreme high speed your GPS may not work (requirement for civilian GPS) and you may get radio problems. I think such condition will never appear on our atmosphere. Maybe other systems expect maximum ground speed values (radar, etc.). – Giacomo Catenazzi Nov 01 '23 at 16:41
Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on [meta], or in [chat]. Comments continuing discussion may be removed. – DeltaLima Nov 01 '23 at 21:04

score 9 · Answer 2 · edited Nov 03 '23 at 10:05

I'm adding another answer to the good one already posted, only to mention some aspects relative to winds in altitude.

Groundspeed vs airspeed

You're talking about groundspeed, speed relative to the ground. But when an aircraft is not taking off or landing, this reference is meaningless.

Air rotates with Earth, meaning when there is no wind air already moves at Mach 1 at 45° of latitude, and is still at the poles, at sea level, a bit more at 10 km height. Adding 300 km/h is adding only 30% only.

Aircraft always fly in this moving air and what counts is the difference between air and the aircraft, what is called airspeed.

For the aircraft this makes no difference air is moving or not, exactly like the fact Earth is moving in space is meaningless for us if we are seated in our kitchen.

So to answer your question: There is no limit at all because there is no impact on the aircraft.

There is an exception for the takeoff and landing phases, where the aircraft depends both on air for being aloft, an the ground to accelerate or brake. If air is moving relatively to the ground, this must be managed, and there are limits, in particular for crosswind, and tailwind. These limits, which are quite small numbers, are defined by the operator, based on the maximum value demonstrated by the manufacturer, e.g. on the A330, Airbus demonstrated a crosswind of 32 kt and a tailwind of 10 kt, but some operator will limit it further.

Wind in altitude

There is a second aspect to your question: Storm wind velocities are given for sea level, but winds at 10 km are very different.

It happens Ciaran strong winds are the left over at sea level of higher currents at the tropopause (10/12 km): Sea this view of the winds at sea level:

The storm is closing to the English channel, and now the rest of the Northern Atlantic is pretty calm at sea level. The location at the circle has now a wind of 38 km/h, but at an altitude of 10 km (250 hPa), winds are really different:

Now we have a wind of 325 km/h at the same place. These data and images are from earth.nullschool.net. So the question is what are winds in this area when there is no storm?

Jet stream

The answer is West-to-East winds are regularly at 200 km/h at cruise altitude, they form the jet stream around the North pole:

This pink/white oscillation denotes winds between 200 and 300 km/h at this time and this is pretty the same other days.

Is G force not applicable and relative to ground speed? This is probably irrelevant for straight-and-level flight, but would it make a difference if one needs to alter course? Is it to small (given standard turns for non-military or non-acrobatic flight) to be consequential? — Stephan Samuel, Nov 02 '23 at 13:27
"G-force" is a measure of acceleration. Acceleration is a change in velocity over time. It does not matter what reference that velocity uses - an acceleration of 1m/s/s is the same force whether my starting velocity is 0 or 9999km/h. — jamesbtate, Nov 02 '23 at 14:33
@StephanSamuel: James is right. Perhaps the only "force" which matters is Coriolis effect, a fictitious force. It makes depressions and anticyclones spiral in presence of acceleration (due to the air mass at different heights/latitudes, so at different tangential velocities), but has no measurable effect on an aircraft. — mins, Nov 02 '23 at 15:05
@StephanSamuel: A plane turns relative to the air. If you had a 100 kt tailwind going east, and then turn 90 degrees left to a point the nose due north, your ground speed will have a 100 kt eastward component. Since you aren't killing this part of your horizontal speed, it doesn't make the turn require any extra G forces. Unless you turn more tightly to make your ground track more like it would have been without wind. So if you fly the same, the G forces will be the same, but your ground track will have an extra component in the direction of the wind. Effectively a wider turn. — Peter Cordes, Nov 02 '23 at 21:56
@StephanSamuel: Perhaps relevant to look at coast guard search patterns (https://www.youtube.com/watch?v=aoXJfuPaFF8 - Smarter Every Day) - ocean current drift speeds are comparable to the water speed of the boat, so this can have a large effect. Destin's video includes plots of a search pattern in absolute lat/lon coordinates vs. in coordinates relative to a drifting buoy (datum). Exact same situation: you don't know anything's different due to surface current except by measuring your position relative to the ocean floor / shore / GPS coordinates, rather than the water. — Peter Cordes, Nov 02 '23 at 22:00

score -4 · Answer 3 · answered Nov 09 '23 at 08:47

-4

Even if I have no pilot's license, I'd say no limit for Tail Wind in Cruise, for sure tail wind is absolutely undesirable in takeoff and landing.

During cruise, there is no 'tailwind', unless wind has a higher speed than aircraft top speed, a rare event, that may induce loss of lift. Did it ever happen? The airplane floats on a wind that takes it forward at a higher speed respect to ground. That's all, folks!

answered Nov 09 '23 at 08:47

Urquiola

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"During cruise, there is no 'tailwind', unless wind has a higher speed than aircraft top speed, a rare event, that may induce loss of lift. " -- incorrect, because the aircraft flies inside the wind and thus does not feel the wind. – quiet flyer Nov 09 '23 at 11:19
This is what I said. Isn't it? – Urquiola Nov 11 '23 at 08:27
Only the pilot in an old open cockpit flying machine 'feels the wind'. Sorry, Airplanes have no senses, no 'feelings'. A semantic issue. Aufwiedersehen. Gesund + – Urquiola Nov 11 '23 at 08:29

Is there a tailwind limit while in cruise?

3 Answers3