Wind effecting climb rate?

NJA_Capt

Well-Known Member
[ 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.

[/ QUOTE ]
The vertical leg of the triangle (in this equation) is not constant.
A 2.7 degree gradient is 270 ft nm.
A 3.5 degree gradient is 350 ft nm.
Although the gradients are a reflection of angle, the difference between the two is a change in rate. The IAS in the equation is constant the only variable that could change the rate was the wind.
 

NJA_Capt

Well-Known Member
[ QUOTE ]
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??

[/ QUOTE ]
No, it's built into the FMZ.



[ QUOTE ]
Service ceiling 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?"


[/ QUOTE ]
Interesting consideration.
At ISA we don't have to step climb until we are above FL430.
Rate of climb leaving FL430 is 788fpm at .80mach.
There is a chart in the AFM that corrects climb time/distance for head and tailwind at altitude.


Good discussion guys. It's really had me digging in the books.
 

JHines

New Member
The gradients are feet (vertical) per nm (horizontal), relative to the ground.

The vertical leg is affected by climb rate; the horizontal leg is affected by the groundspeed (vector sum of IAS and wind speed in direction of fligh path). Change in either affects the angle (gradient).

I agree only the windspeed changes in the example.

The gradient is increased by a headwind because the headwind decreases the ground speed; not because it increases climb rate.
 

NJA_Capt

Well-Known Member
[ QUOTE ]
The gradients are feet (vertical) per nm...

[/ QUOTE ]
Gradients are the ratio of alt gain to horiz distance. A 3.5 gradient is the angle the plane must fly to reach the desired altitude.

[ QUOTE ]
The vertical leg is affected by climb rate; the horizontal leg is affected by the groundspeed (vector sum of IAS and wind speed in direction of flight path). Change in either affects the angle (gradient).

[/ QUOTE ]

I think we are looking at the same thing through different formulas. I am looking at fixed distances compared to your varying distances ref. ground speed.

I am looking a a fixed 1nm (6000')distance with differing climb gradients (angles). Over the same 1nm course, the aircraft with the headwind would attain a higher altitude over the 1nm quicker than the one without the wind.

Picture two aircraft on parallel runways departing simultaneously at the same indicated airspeeds. One has 30kt headwind(A), the other has 0 wind(B). Altitude will be measured 1nm (6000') past the runway. If aircraft A has a climb gradient of 3.5 (5.8%)and B has 2.7 (4.5%), at the 1nm point, A will be at 350' and B will be at 270. Or aircraft A attains 270 before aircraft B.

For the sake of argument, we are not allowed to consider headwinds when figuring gradients in order to be more conservative (safer).
 

Baronman

Well-Known Member
NetJetsCapt.,
You're right on with your anlysis of the two aircraft taking off, but that again is climb gradient, not rate of climb.

To answer the original question of rate of climb vs. headwind component we would set up the following:

Two aircraft take-off on parallel runways, one with a 20kt headwind component, one with no headwind component.
After both aircraft rotate and begin to climb, which will be the first to reach 1,000' above the airport?

Notice no reference is made to horizontal distance or groundspeed. Cause it doesn't matter is my arguement!!!

But again, you're right on with the climb gradient in your example, I'm with you on that one. And realistically climb gradient is more operationally important, this is just my theoretical question.
 

JHines

New Member
[ QUOTE ]
I think we are looking at the same thing through different formulas. I am looking at fixed distances compared to your varying distances ref. ground speed.

I am looking a a fixed 1nm (6000')distance with differing climb gradients (angles). Over the same 1nm course, the aircraft with the headwind would attain a higher altitude over the 1nm quicker than the one without the wind.

Picture two aircraft on parallel runways departing simultaneously at the same indicated airspeeds. One has 30kt headwind(A), the other has 0 wind(B). Altitude will be measured 1nm (6000') past the runway. If aircraft A has a climb gradient of 3.5 (5.8%)and B has 2.7 (4.5%), at the 1nm point, A will be at 350' and B will be at 270. Or aircraft A attains 270 before aircraft B.

For the sake of argument, we are not allowed to consider headwinds when figuring gradients in order to be more conservative (safer).

[/ QUOTE ]

I agree with all of that, assuming that by "before" you mean distance, not time. Aircraft A and B both attain the same altitude the same number of seconds after brake release, but B will have traveled farther over the ground.

Example (numbers picked to match your example): A and B both climb (still air) at a Vy of 180 kts IAS, at which the POH/PIM says 810 FPM (or about 8 kts vertically). Aircraft A traverses the specified 1 nm and climbs to 350' (or close to it) in 24 seconds at its 150 kt GS (30 kt headwind).

Aircraft B traverses the specified 1 nm and climbs to only 270' in 20 seconds at its 180 kt GS. Aircraft B hits 350' at 24 seconds and 1.2 nm from the runway. The gradients change with no change in climb rate. If there is a 300' tower 1 nm from the runway, aircraft B may smash into it.
 

IrishSheepdog

Sitting in the median
Ok I didn't bother reading all the posts since it seemed like they were getting really technical and I'm not that smart. LOL! Anyways, you won't have a difference in climb rate. What will change is the distance travelled across the ground in the time it takes to arrive at cruise altitude. This is due to the decreased groundspeed. This is why when we are flying into headwinds, we often will climb at only 1000-500 FPM to keep a very high groundspeed to offset the penalty from the headwind. Or, with a tailwind, we can climb faster to get above low level turbulence over the city since our groundspeed is fairly high. The climb rate isn't affected by the wind though.

Also, your climb rate isn't affected in takeoff/landing. Ground roll is though.
 

sixpack

New Member
I wish the hiring airlines would ask this question in their interviews.

(ps: I liked bluelake's answer the best... correct, yet humble)
 

sixpack

New Member
Here's a puzzle for the technical folks.

Question 1: There's no wind, and you're above your absolute ceiling, and losing 500 fpm (at 50 kts). What is your climb gradient?

Question 2: Your airplane is climbing at 1000 fpm at 50 kts, and you have a headwind of 150 kts. What is your climb gradient?

Which is better?
 

Ralgha

Well-Known Member
The gradient is exactly the same in each, but the first one is better because, unless you have rear windows, you can't see the mountain you're about to hit in the second scenario. :)
 

sixpack

New Member
OK, Kevin got that one right.

Try this one.

You are flying the LOC (BACK CRS) Rwy 13 Approach, on Final, and you are inverted. What course do you set your HSI needle?

(No really, it was a really cool move..., I have a polaroid)
 
Top