Wind effecting climb rate?

[Baronman]

Ok, there was a big discussion today at my flight school among the CFIs due to the heavy winds. Somebody said, on a day like today, your rate of climb will be fantastic...I personally disagree. Rate of climb will not change if you are in a head/tailwind situation.

I know wind will only impact angle of climb, not rate of climb when it is a steady state wind. Is there any source (book/website) where I can back this up? I kept trying to explain the idea of being in an airmass etc but they wanted hard evidence....Any thoughts?

 

[cimepilot]

I believe heavy headwinds help rate of climb. The main is reason is beacause of first-hand experience with this. But, he is the theory behind it:

If you have a 30 knot headwind, your airspeed will be at 30 knots even if you are not moving. This means that once you start moving and climbing out you can pitch up higher because you already have that 30 knots of extra airspeed from mother nature. That thirty knots combined with what you are generating from forward motion gives you the ability to increase your angle of attack and results in a steeper climb attitude.

In fact, if you want to maintain Vy or Vx on a windy day like mentioned, you will have to pitch up higher to do so which increases climb performance dramatically.

Last week, here in Orlando we had three days of 25-30 knot winds blowing right down the runway. On those three days, I was getting 900-1,100 fpm climbs on the C-172 which under the same outside pressure and temperature conditions would normally yield only 500-700 fpm climbs.

 

[ERAU_Intern]

That may be true while you are on the ground. But once you get airborne, a headwind or tailwind will NOT help your rate of climb. Angle of climb will change. For instance, if your C-172 climbs at 700fpm for the given temperature and weight, it is GOING to climb at 700fpm. The only thing that may change that momentarily is a wind gust. ANYWAY, if you have a 30kt tailwind, your 700fpm is going to result in a longer distance over the ground in order to reach your desired altitude. With a 30kt headwind, you will use up less ground distance to achieve that same altitude. But once again, the "Rate" of climb will not change. cimepilot, think of it this way. That wing is only going to perform as a result of the airflow over it. so if your airspeed indicator is reading 72kts, thats what the wing is going to fly like. And answer me this. Have you ever been climbing at Vy on a day with a 30kt headwind and observed your indicated airspeed jump up 30kts and stay there? Cause if you HAVE, I wanna know how you did it.

 

[Baronman]

I would argue that the reason why you got a jump in rate of climb after take-off was that you encountered stronger winds as you climbed, meaning the winds at 500ft were stronger than the winds on the runway.

SO....IF winds affected climb rate, then have you ever noticed that it's harder to climb enroute with a tailwind?? Will our service ceiling be lower when we have a tailwind? Do you see any difference in indicated/true airspeed with a head/tailwind....Nope....

 

[EatSleepFly]

[ QUOTE ]
If you have a 30 knot headwind, your airspeed will be at 30 knots even if you are not moving. This means that once you start moving and climbing out you can pitch up higher because you already have that 30 knots of extra airspeed from mother nature. That thirty knots combined with what you are generating from forward motion gives you the ability to increase your angle of attack and results in a steeper climb attitude.


[/ QUOTE ]

That 30 knots isn't "blowing" over the aircraft in flight. It has absolutely zero affect on your ability to produce lift. You are in an airmass that is moving 30 knots, that is all. Your aircraft will perform just as it does on a calm day, with one exception:

You will gain a given amount of altitude over a shorter distance. Vice versa if it is a tailwind- you will cover a greater distance to reach a given altitude.

If it helps, think about it in terms of "Control and Performance." X number of degrees of pitch will get you Vy every time, as long as the attitude indicator is set correctly. Do you ever adjust this "X number of degrees" for a windy day when going on an instrument flight? No.

Also, by that line of thinking, pointing the aircraft into or away from the wind will have an effect on stall speed, and we know that is not true.

Now, all that being said- I am referring to a constant, steady-state wind. When it gets gusty, and you throw windshear into the mix, that changes things.

 

[E_Dawg]

This is like the whole downwind to final loss of lift 'theory'... which is total BS

Here's the deal:
Air is a fluid and wind is air in motion
Motion is relative
You're IN the air (so all motions are relative to the air)

The plane doesn't give a crap about the wind, because when it's IN the wind (air in motion) it's part of it.


But anyways... I remember hearing that Vx changes with wind speed. Anyone know for sure??? And how much do you add / subtract.

 

[EDUC8-or]

I gotta chime in. This is commonly misunderstood. Wind only plays a role in groundspeed.

Think of you airplane as a boat. Think of the wind as a river. If you are travelling downstream at 20kts in a current that is 20kts, your speed through the river is 20kts. Your groundspeed may be 40, but not the actual speed through the water.

The wind is a larger river which we travel. The currents and flows are shifting, but we will not see an increase in climb performance with a headwind or tailwind. Our groundspeed and ETA may improve, but not performance, cooling, etc...

It is true that a headwind requires less of a groundspeed for takeoff, but once your wheels leave the ground your performance becomes a function of airspeed, available power, etc...

This is all assuming a constant wind with no shearing.

 

[bluelake]

[ QUOTE ]
This is all assuming a constant wind with no shearing.

[/ QUOTE ]

Exactly, and I think sometimes one CAN get a SSLLIIIGGHTTLLLY or MMMOOOMMEENNNTTAARRYYY better climb rate when climbing into the wind when the wind is increasing in velocity as one climbs. Here's my idea, and I know I read this somewhere, so at least there are two of us in the world that see it this way:

If an airplane is climbing at 70, into a 20 knot headwind, then, yes.. the groundspeed is 50. If the airplane then climbs into a layer where the wind changes to 25 knots, the groundspeed isnt gonna instantaneously change to 45, because the airplane has inertia with its own forward energy. I think the same holds in reverse, hence the "BS" theory of losng lift on downwind to landing.

I am horrible at dynamics, someone might be able to describe this better than I.

 

[NJA_Capt]

[ QUOTE ]
If it helps, think about it in terms of "Control and Performance." X number of degrees of pitch will get you Vy every time, as long as the attitude indicator is set correctly. Do you ever adjust this "X number of degrees" for a windy day when going on an instrument flight? No.


[/ QUOTE ]

No way. You look at the ATT indicator initially in a climb, after that you are mainly concerned with speed. You do whatever is necessary with pitch to control that speed. Does pitch change? Of course it does. If you takeoff at 32 degrees F Vy might be +15, if its 100 degrees F Vy might be +3.

Climb performance is based on excess thrust. Excess thrust is used to create lift. If the headwind is providing you with X amount of lift, there is more excess thrust available. This extra thrust increases your speed. To maintain climb speed with a headwind you must increase the angle of attack. If you increase your angle of attack while maintaining climb speed you increase your rate of climb.

Several of you compared two aircraft climbing at the same IAS, one with a headwind, the other with a tailwind. Then stated that the one with a headwind reached cruise altitude in a shorter distance. If they are traveling at the same IAS, to the same altitude, the one with a headwind gets there first. First=Less time because of the increased rate of climb.

Conversely, we glide the plane into the wind while doing emergency landing practice to decreases our rate of descent, decreases GS and decreases the rollout.

If you are cruising steady state and trimmed hands off, with no wind, and suddenly get a 50kt gust, which way will the airplane pitch initially? Up. This is an example of an increase in rate of climb.

 

[JHines]

[ QUOTE ]

Here's the deal:
Air is a fluid and wind is air in motion
Motion is relative
You're IN the air (so all motions are relative to the air)

The plane doesn't give a crap about the wind, because when it's IN the wind (air in motion) it's part of it.


But anyways... I remember hearing that Vx changes with wind speed. Anyone know for sure??? And how much do you add / subtract.

[/ QUOTE ]

Well...the defined"Vx" (airplane's steepest still air climb) wouldn't change, for exactly the reasons you stated. The actual climb gradient relative to the ground would change with wind speed. I would think the only time it would be worth adjusting for would be for a downwind takeoff, which might make the climb gradient much worse than expected relative to the runway and any fixed obstacles, under some circumstances.

Proabably the easiest way to see the magnitude of the difference is to look at the rate of climb table in a terps book. Pick an arbitrary gradient, and an arbitrary ground speed. then look at the adjacent entires for higher ground speed (tailwind) or lower (headwind). Example, at a 600FPM climbout at 80 KIAS, a 10 knot tailwind lowers the gradient by 50 FPNM.

 

[Baronman]

Mmmm...NetJetsCapt,

If you do a 360 degree turn with a constant 20kt wind from the north while maintaining altitude, will you get a different indicated airspeed throughout the turn? Nope...

Will you have to retrim the plane throughout the turn? Nope...There should be no change in performance throughout the turn provided it's a steady wind.

 

[cimepilot]

Although not stated as clearly and precisely as NJAcapt, what I said agrees with what he said and makes perfect sense. You are able to get a higher pitch attitude when flying in strong winds to maintain the same climb speed in a no-wind situation. This leads to a better rate of climb.

 

[NJA_Capt]

[ QUOTE ]
Mmmm...NetJetsCapt,

If you do a 360 degree turn with a constant 20kt wind from the north while maintaining altitude, will you get a different indicated airspeed throughout the turn? Nope...

[/ QUOTE ]
Correct, but you are varying the angle of bank to compensate for the increase or decrease in wind speed. If you hold a constant bank angle throughout the turn you will get an egg shaped turn.

 

[Baronman]

Constant Bank angle will result in an egg-shaped pattern, I agree....But that's because of the changing groundspeed, not changing airspeed. (Turns around a point).

Nothing during the turn around a point suggests that as we head into the wind, we must decrease angle of attack to stop an impending climb. We're just changing crab angle and bank angle to get a nice constant radius circle...

 

[NJA_Capt]

OK, I'll cut to the chase.
From the CE750 AFM second segment climb gradient chart.
1000'elevation
15 C
35,000#
10 kt tail wind 2.7
0 wind 3.1
10 kt headwind 3.2
30 kt headwind 3.5

Rate of climb increases with headwind.

 

[SteveC]

You're just pulling our leg(s), right?
[ QUOTE ]
Climb performance is based on excess thrust. Excess thrust is used to create lift. If the headwind is providing you with X amount of lift, there is more excess thrust available. This extra thrust increases your speed. To maintain climb speed with a headwind you must increase the angle of attack. If you increase your angle of attack while maintaining climb speed you increase your rate of climb.

[/ QUOTE ]
The only time that a headwind provides additional lift is when you are in an increasing headwind situation. A steady-state headwind or tailwind makes no difference. Power + attitude = performance, i.e. 75% power and 10 degrees pitch-up will give the exact same climb rate whether you are traveling upwind or downwind.

[ QUOTE ]
Several of you compared two aircraft climbing at the same IAS, one with a headwind, the other with a tailwind. Then stated that the one with a headwind reached cruise altitude in a shorter distance. If they are traveling at the same IAS, to the same altitude, the one with a headwind gets there first. First=Less time because of the increased rate of climb.

[/ QUOTE ]
No, the amount of time will be identical. The distance traveled over the ground will be different, but the climb rate (altitide change per unit of time) remains the same for either direction.

[ QUOTE ]
Conversely, we glide the plane into the wind while doing emergency landing practice to decreases our rate of descent, decreases GS and decreases the rollout.

[/ QUOTE ]
Yes, gliding into the wind will decrease GS and rollout, but it does not decrease the rate of descent. If it did, we could fly a C152 into a fifty knot headwind, engine shut down, and stay up forever.

[ QUOTE ]
If you are cruising steady state and trimmed hands off, with no wind, and suddenly get a 50kt gust, which way will the airplane pitch initially? Up. This is an example of an increase in rate of climb.

[/ QUOTE ]
Agreed, but this is only due to the inertia of the airplane attempting to maintain the same airspeed in a changing condition. Does not apply to a steady-state wind condition.

 

[SteveC]

[ QUOTE ]
Rate of climb increases with headwind.

[/ QUOTE ]
No. Headwind increases climb gradient (altitude gained per horizontal distance traveled), not rate of climb (altitude gained per unit of time).

 

[Baronman]

Net Jets Capt,
Have you ever been given a clearance up to a higher FL and had to check your charts to see if you could get up there??

Service cieling is when rate of climb= 100fpm right?

So when ATC queries if you can get up higher, have you ever said "unable because of a wicked tailwind?" Probably not...

It's based upon aircraft weight, and temperature primarily but not head/tailwind.

 

[JHines]

[ QUOTE ]
Although not stated as clearly and precisely as NJAcapt, what I said agrees with what he said and makes perfect sense. You are able to get a higher pitch attitude when flying in strong winds to maintain the same climb speed in a no-wind situation. This leads to a better rate of climb.

[/ QUOTE ]

That sounds attractive, but it is just not correct. The affect of headwinds or tailwinds on lift is only transient as the aircraft lifts off, touches down, or flies into an area where the wind speed and/or direction changes. The terms "headwind" and "tailwind" are meaningful only in relation to movement over the ground. They have no effect on aircraft performance through the air (i.e. climbs).

For example, you are sitting on the end of runway 36 with the winds at 360 at 50 KTS magnetic. The wind is then 50KTS "headwind" relative to your airplane and the runway. You start your roll. As soon as the wheels lift, your airplane leaves the ground frame of reference and enters the wind's frame of reference. After some extremely short transition period, both the plane and the wind have a 360 at 50 KTS velocity vector relative to the ground. There is no effect on pitch attitude, climb rate, or anything else, because there is NOT a 50 KT wind velocity component relative to the plane.

 

[JHines]

[ QUOTE ]
OK, I'll cut to the chase.
From the CE750 AFM second segment climb gradient chart.
1000'elevation
15 C
35,000#
10 kt tail wind 2.7
0 wind 3.1
10 kt headwind 3.2
30 kt headwind 3.5

Rate of climb increases with headwind.

[/ QUOTE ]

No, the climb gradient changes, which is the A/C's climb angle relative to the ground. The climb rate, which is the vertical leg of a right triangle, is constant. The horizontal leg (GS) is shortened if there is a headwind, increasing the gradient.