Headwind and Tailwind during cruise

[Driver 170]

During cruise of a 737 NG, will your TAS remain the same regardless of a TW or a HW and only GS that will increase if you have a TW and decrease if you have a HW?

[Intruder]

That depends on whether you adjust the speed for best economy.

The FMS in ECON mode will automatically increase TAS with a headwind, and decrease it in a tailwind. If in a fixed Mach or Long Range Cruise mode, TAS will remain the same with wind changes.

[Driver 170]

So the aircarft is moving along with the air mass and lets say its a TW this will reduce my AIR distance and reduce my time in flight?

[Lafyar Cokov]

Exactly - as the 'air you are travelling in' for want of a better expression - is travelling in the same direction as you - like on a raft down with the current - you have fewer 'air miles' to travel and your groundspeed is increased by th wind speed.

[Driver 170]

Thanks for the input much appreciated.

[pattern_is_full]

All of the above is correct. But there is another factor.

Any wind at all will make a round-trip longer than in no wind. Because you spend more time slogging along in the headwind than you do breezing along with a tailwind, so the cumulative effect is bigger for the headwind. (You are affected by it for more minutes)

Fly 60 miles from A to B and 60 miles back from B to A, in a 120-knot plane with no wind, and the round trip takes 60 minutes.

Fly 60 miles from A to B with a 20-knot headwind, and 60 miles back from B to A with a 20-knot tailwind.

Time for the first leg is 36 minutes. Time for the second leg is 25.7 minutes. Total time = 61.7 minutes

(increase distances and speeds as needed for a 737 - remember that a 737 at 35,000 feet may have 60kt winds to factor in)

"You can't win, and you can't even break even."

But indeed, TRUE airspeed is unchanged. It's only ground speed that takes it on the chin.

[thing]

Any wind at all will make a round-trip longer than in no wind.

And the slower you are the more difference it makes, which is why something like an Arrow which cruises at 130 kts at £150 ph is often cheaper over a trip than a Warrior which cruises at 100 kts at £110 ph.