High Speed Climb

[veloo maniam]

Hi Aviators/Guardians of the skies, I need to know the rate of climb when High Speed Climb is approved below FL100 (Boeing and Airbus Commercials) Is there a link I can refer to?
Replies appreciated.

[Cartman's Twin]

Hi Veloo

The term 'High Speed Climb' refers not to the actual rate of climb, but the airspeed. Below FL100 there is generally a 250kts speed restriction. So when this is ATC restriction is removed, the crew can increase to their optimum climb speed which varies greatly depending upon the aircraft, load and the parameters dictated by the operator.

There is an impact upon the rate of climb but there is no 'rule of thumb' as to by what. The rate is more a function of the aircraft's potential performance and loading.

Hope this helps

[veloo maniam]

Thanks Cartman..I see a drop in the climb rate...say for eg 1000/min to 700/min but of course it varies with all the factors you have mentioned. Since you have indicated there is no rule-of-thumb, I will just watch and learn so that my trainees can be well informed. Thanks again.:O

[fireflybob]

I see a drop in the climb rate...say for eg 1000/min to 700/min but of course it varies

Whilst the a/c is accelerating from 250 kt to enroute climb (say 300 kt) you would expect to see a reduction in rate of climb as the kinetic energy is increasing compared to potential energy (height gained) - once the enroute climb is established the rate of climb will increase again - as has been stated above the actual rate of climb depends on factors such as weight etc.

[veloo maniam]

fireflybob...when will the a/c resume its normal climb rate?
thanks

[fireflybob]

when will the a/c resume its normal climb rate?

once the a/c has accelerated to it's en route climb speed

[veloo maniam]

Thanks fireflybob.:)

[Crazy Voyager]

Now you may ignore this post if you'd like, as you seem to have got the answer you wanted. I just want to (if I may borrow your topic a bit :8) dig a bit deeper in the physics behind this.

Now if I remember physics correctly, the air resistance against a surface increases with the square of the speed. So in other words twice the speed=four times the resisting force (can anyone who've studied some physics confirm this?).

If so, then a higher speed means more resistance=more power required to maintain airspeed (this is esspecially true at low altitudes where the air is more dense).

So what I'm trying to say is that a high IAS climb should result in a lower climb rate throughout the climb.

Initially rate is reduced while IAS is increased.

After IAS is at desired number, energy will be used to climb (increasing pitch angel).

But the engines are using more power to keep the speed up now than before, therefore the climb rate will be lower.


If I'm correct in my assumptions this should mean that the highest rate of climb is reached when you climb at minimum clean speed. This would mean minimum amount of resistance from the air and maximum amount of energy used to climb.


Am I making any sense? :p

[fireflybob]

If I'm correct in my assumptions this should mean that the highest rate of climb is reached when you climb at minimum clean speed. This would mean minimum amount of resistance from the air and maximum amount of energy used to climb.


Think you are confusing max rate of climb with max angle of climb - not the same thing! Former is height gained v time whereas latter is height gained v horizontal distance travelled.

Best rate of climb is achieved where the gap between power required and power available is largest!

Of course it also makes a difference whether it's jet or piston - if you want a good explanation see Mechanics of Flight by A.C. Kermode - one of the classics!

[Crazy Voyager]

Hm, I may have confused the terms.
I have always viewed "rate of climb" to be Distance/time (feet/minute). "SAS521 descend FL210, rate 2000 feet per minute or more". But I'm just a wannabe so it's probably I who have confused it.

So let's pose the question this way.
Does it make sense to belive (based on my previous post) that you can climb at a higher rate (feet/minute) at a low speed. Due to the decrease of resistance from air and since this there being more power available to propell the aircraft up rather than forward.

[Avionker]

http://upload.wikimedia.org/math/d/b/7/db7735d03f8de6082982164856a0d8ba.png

Don't forget to take into account that the lift generated (L) increases as the airspeed (v) increases. The only way to propel the aircraft up, as you put it, is to propel it forward......

Linky thing (http://en.wikipedia.org/wiki/Lift_(force))

[Crazy Voyager]

Hm, I now have some bedtime reading :ok: