Hi,

I'd like to understand how wind shear affects the rate of climb.

On page 8.8 paragraph 3 states 'wind shear can also be encountered on climb after take-off, where both rate and angle of climb will be affected.


Thanks.

While it is true that when an aircraft is climbing in a steady wind, the wind will have no effect on the RATE of climb no matter what direction it may be coming from. However, when an aircraft SUDDENLY encounters a change in wind speed, such as would be experienced when leaving a layer of calm air near the surface to enter a layer of faster moving air above. there will be a momentary change in IAS. This is due mainly to the inertia of the aircraft preventing it from suddenly changing its speed through space. Since IAS is one of the factors that affects lift, there will also be a change in lift and climb performance, both angle and rate, will be affected. The angle of climb will remain different to the previous angle, but the rate of climb will gradually return to the no-wind value.

Bob

Thanks Bob.
So if there is a sudden increase or decrease in IAS due to change in wind speed, the rate will be affected though by a small degree
I was just trying to understand how the question would be worded for the answer to read 'rate of climb is affected' etc as opposed to Q7 on page 9.18.

The key to these questions is the presence or absence of the word 'sudden'. Wind shear must always be described as a sudden change in wind speed or direction.

Question 7 on page 9.18 is referring to a change in wind conditions during a steady climb, but it didn't say it was a sudden change. For example, if you climbed on one day in a certain wind and climbed another day in a different wind, you would expect no change in the rate of climb. However, if there was a sudden change in wind velocity during a particular climb, you would expect rate of climb to be momentarily affected.

By the way, the change in rate of climb may not always be small, that depends on the amount of change in wind velocity. However the effect on rate of climb will always be temporary. It's all about inertia. If you step off a moving platform onto a stationary floor you temporarily lose you balance, but you soon regain it.

Bob

Perfect. Thank you for explaining.

Hi Bob just wondering where they get angle of decent and angle of climb from angle of what, between flight path and the ground ? I seen in the book angle of climb is the height gained in a given distance is this the same for decent but change the gained with lost? and in fig 8.18 on page 8.7 it says that angle and rate of climb are increased if you go by (height lost in a given distance (angle of decent) and (Height lost in a given time ( rate of decent) these would be true just unsure on the angle component of it all?
Thanks for your time
Cheers Bob
Linc

Hi Linc,

Yes the angle of climb and the angle of descent are simply the angle your flight path makes in relation to the ground if the ground were horizontal and perfectly flat. Rates of climb and descent relate the amount of height change in a given period of time.

Cheers,

Rich

Thanks Rich on page 8.7 it says that rate and angle increase after the head will has dropped 10kts? if the angle between the ground and the flight path I thought angle would decrease?

Hi Rich just seeing if you seen the reply to the message ? cheers

Linc

Hi Linc,

Thanks for the reminder

When the headwind drops during the descent, the aircraft will initially lose airspeed and therefore lift. This means the aircraft will descend more steeply - the angle of descent will increase until the aircraft regains equilibrium in the new region of air. After that equilibrium is restored, the rate of descent will return to what it used to be before the wind shear and the descent angle will indeed be shallower.

The question is referring to what actually happens in the first moments when the aircraft transitions into the new wind: it will undershoot because its rate of descent and angle of descent will both increase.

Cheers,

Rich