Best Rate Of Climb Question

[NljbA380]

Can somebody explain why the best rate of climb is uneffected by a headwind.

 

I understand that the best rate of climb will provide the greatest vertical distance over minimal time, and will generally cover greater ground distance at a higher speed and lower attitude then that of the best angle of climb which will provide the greatest vertical distance over the minimal ground distance, and generally have a slower speed and higher attitude. And that the best angle of attack is effected by the headwind, which would produce a greater attitude, but why is the best rate of climb uneffected by a headwind and is the same with or without a wind (same vertical distance).

 

Also, can someone please explain the stalling angle of attack/speed. The definition in my book is "At the stalling speed, the stalling angle of attack is required to produce the necessary lift. Any further increase in angle of attack will result in less lift but more drag. It is important to note that it is actually the angle of attack that causes the stall".

 

So correct me if im wrong:

 

I can fly at 60 knots, and say the aircraft, at this speed, will have a stalling angle of attack of say 16 degrees (just random). Anything above this angle will result in a stall.

 

Or i can fly at 50 knots, and say the aircraft, at this speed, will have a stalling angle which is less then 16 degrees

 

And vice versa.

 

So essentially, the angle of attack for a stall is dependent on the IAS of the aircraft?

 

How is this effected by weight?

 

Naturally, by increasing the weight, a greater amount of lift is required.

 

For the aircraft to fly at an angle of say 16 degrees, the IAS is going to be have to be greater then the original 60 knots. So basically the increase in weight, will require a greater speed to fly at the angle of attack to maintain lift, which will create the stall if gone beyond this angle or if the airspeed is lowered beyond this new airspeed.

 

Ive kind of confused my self.

 

 

[Ada Elle]

Winds only affect those things that have a ground component. Best rate of climb is not ground referenced and thus headwind is unimportant.

 

Stall is related to angle of attack. However, at speeds less than the stall speed, you cannot get adequate lift to maintain level flight at the critical angle of attack. So you can fly an aircraft at less than stall speed, and not stall the wings, but it will be descending.

 

How is this affected by weight? At higher weights, you need more lift, so at the critical angle of attack you need higher speeds to maintain level flight.

 

essentially: mg = Cl A v^2. At the critical angle of attack you will have a certain Cl. A is fixed. so either v goes up as m goes up, or you can't maintain level flight.

 

 

[planesmaker]

A wing will stall at its particular AofAttack. We use the ASI as a guide only to what the AofA is. Eg at 1g in wings level flight at a particular wt the stall AofA will be reached at a certain airspeed ( eg 62kts) change any of those factors, wt, g loading, or banking the aircraft and the stall speed will change but not the stallAofA. So if you add a passenger the wt increases therefore the stall speed also increases as the stall AofA needs to provide more lift, however the stall AofA still remains the same ( in your example 16') the ASI is only a guide to the actual AofA, a crude AofA meter if you will.

 

 

[old man emu]

A bit of a sidetrack, but there is an instrument called an Angle of Attack meter which gives a visual display of the AofA.

 

How useful would one be on your panel? Here is a balance comment on them:

 

http://airfactsjournal.com/2013/08/angle-of-attack-isnt-a-miracle-cure/

 

OME

 

 

[Fishla]

Your first question:

 

You are flying through a parcel of air, the parcel of air is moving across the ground.

 

No matter how fast (or in what direction) the parcel of air is moving across the ground, you are moving through that parcel of air at the same speed and direction.

 

So you will climb through this parcel of air the same no matter how it is moving in relation to the ground.

 

If the parcel of air was moving downwards vertically then yes, your rate of climb *relative to the ground* will be affected - you're still climbing through the parcel of air at the same rate.

 

If the parcel of air is moving forwards (tailwind) your ANGLE of climb *relative to the ground* will be smaller. but again you're climbing through the parcel of air at just the same over time. The RATE of climb is still the same (height gained overtime), but the prevailing winds can affect your ANGLE of climb. A headwind would increase your angle of climb (but not the RATE).

 

 

[Happyflyer]

Stall is related to angle of attack. However, at speeds less than the stall speed, you cannot get adequate lift to maintain level flight at the critical angle of attack. So you can fly an aircraft at less than stall speed, and not stall the wings, but it will be descending.

Not quite correct. If by "the stall speed" you mean the published stall speed of your aircraft, then you certainly can fly slower than that speed and still not descend. The published stall speed will be for MTOW, no power, 1 G and straight and level flight. If you fly at less than MTOW (kick out the passenger and have low fuel) and with power on you can fly at much lower speeds than the published stall speed and still not descend and even climb.

Someone also said that airspeed is a crude angle of attack meter. As angle of attack is controlled by the stick or control column I would rather use stick position as a slightly less crude angle of attack meter.

 

 

[Thirsty]

Yes that's how I always taught this. A headwind is only important if you can see the ground or are referencing the ground.

 

Try this: you're climbing out after takeoff and you have a headwind. You can see the ground so it looks like you're climbing steeper and going slower than "normal". Now, look away from the ground. Can't see the ground anymore so rate of climb etc can only be judged by looking at the vsi which would read exactly the same as if there was no headwind.

 

 

[facthunter]

Best climb speed ( for best rate of climb) is dependent on your AUW. The heavier the faster. (like a glider for x country with ballast tanks) . You would employ that if your aim was to gain height in the minimum time. like towing a glider or dropping meat bombs.or perhaps keeping your circuit as small as possible. It is hardly justified in a cross country situation, where you aim to get somewhere as efficiently as possible. Nev

 

 

[NljbA380]

Your first question:You are flying through a parcel of air, the parcel of air is moving across the ground.

 

No matter how fast (or in what direction) the parcel of air is moving across the ground, you are moving through that parcel of air at the same speed and direction.

 

So you will climb through this parcel of air the same no matter how it is moving in relation to the ground.

 

If the parcel of air was moving downwards vertically then yes, your rate of climb *relative to the ground* will be affected - you're still climbing through the parcel of air at the same rate.

 

If the parcel of air is moving forwards (tailwind) your ANGLE of climb *relative to the ground* will be smaller. but again you're climbing through the parcel of air at just the same over time. The RATE of climb is still the same (height gained overtime), but the prevailing winds can affect your ANGLE of climb. A headwind would increase your angle of climb (but not the RATE).

So im guessing this is where the IAS and GAS comes into it does it? IAS doesnt take into account the speed at which the wind is moving. Where as the ground speed does. So if I had a 5 knot headwind and a 20 knot headwind, the rate of climb would be the same regardless. But if we were talking about the GAS in relation to the rate of climb, they would be different? But because the rate of climb is in relation to time, it is uneffected by it correct?

 

 

[NljbA380]

So there is a stalling speed, which has a corresponding stalling angle for any given aircraft at a given wait. It is to fly at this speed, at x weight, the aircraft must have an angle of attack of whatever it is. Correct?

 

So which is the fixed variable? By the sounds of it its the stalling angle and the stalling speed is dependent on the weight of the aircraft. And by increasing the weight of the aircraft, for a given stalling angle (commonly 16 degrees) the stalling speed will INCREASE.

 

Is this all correct? Anyone confirm?

 

 

[planesmaker]

Yes.simply put The fixed is stall AofA. All others variable

 

 

[facthunter]

Yes.. stalling speed increases with actual weight . or with a dynamic situation such as a banked turn. where you feel an extra"G" load The stalling angle for a given airfoil stays the same. If you modify the airfoil with Ice accretion or slots and flaps the stall angle changes because the airfoil has changed. If you have ice on the wing for example, the stall speed may increase markedly and lift will be reduced and drag increased. Nev

 

 

[Fishla]

So if I had a 5 knot headwind and a 20 knot headwind, the rate of climb would be the same regardless. But if we were talking about the GAS in relation to the rate of climb, they would be different? But because the rate of climb is in relation to time, it is uneffected by it correct?

Rate of climb would be the same. You are ascending through a parcel of air which is also moving relative to the ground.

 

So if the parcel is moving backwards from an obstacle, you would clear an obstacle quicker with the higher headwind- the ANGLE of climb would be greater the greater the headwind.

 

But you won't have ascended any quicker. The parcel is being blown backwards away from the obstacle with a headwind (and you with it). It decreases your horizontal speed (ground speed).

 

Ground speed will never affect climb RATE, but it will change the ANGLE you climb at.

 

I think you also want to call it GS (ground speed) not GAS. Ground speed is not an air speed. Airspeed is really a pressure - technically the dynamic pressure - the pressure of the wind hitting your wing as you push against it.

 

We travel through a parcel of air, hitting it, that's IAS. The pressure is being directed downwards - that's how we are flying!

 

You've got me thinking now. I found this which shows you what your ASI is actually showing you. http://www.rst-engr.com/rst/articles/KP89JUL.pdf

 

 

[NljbA380]

Yes.. stalling speed increases with actual weight . or with a dynamic situation such as a banked turn. where you feel an extra"G" load The stalling angle for a given airfoil stays the same. If you modify the airfoil with Ice accretion or slots and flaps the stall angle changes because the airfoil has changed. If you have ice on the wing for example, the stall speed may increase markedly and lift will be reduced and drag increased. Nev

Just out of curiosity. I know that when your flying in a nose up attitude, the angle of attack is the angle between the air flow and the chord of the cross sectional of the wind. How is said angle of attack influenced/calculated in bank and even in a ascending bank? How is it different from each side of the wing?

 

Can someone confirm this. I just read. "The only two terms in the lift equation that can be different between the two wings are lift coefficient (ie AOA) and speed. We have agreed the speed of the outer one is up so it must have less AOA."

 

Say were in a bank to the left. Obvisouly the right hand side of the wing is travelling at a quicker speed. When they say the only thing that can be different between the two wings are lift coefficient and speed. How is this true, because if your in a bank, then one wing is going to have to produce a greater amount of lift. And in which case, if we are banking to the left, the right hand wing is going to have both a greater speed and as a result angle of attack isnt it? And that explains why because of the greater angle of attack, it will stall first at a higher speed. And thus why we flip to the right when we stall. is this the correct thinking?

 

 

[NljbA380]

Rate of climb would be the same. You are ascending through a parcel of air which is also moving relative to the ground.So if the parcel is moving backwards from an obstacle, you would clear an obstacle quicker with the higher headwind- the ANGLE of climb would be greater the greater the headwind.

 

But you won't have ascended any quicker. The parcel is being blown backwards away from the obstacle with a headwind (and you with it). It decreases your horizontal speed (ground speed).

 

Ground speed will never affect climb RATE, but it will change the ANGLE you climb at.

 

I think you also want to call it GS (ground speed) not GAS. Ground speed is not an air speed. Airspeed is really a pressure - technically the dynamic pressure - the pressure of the wind hitting your wing as you push against it.

 

We travel through a parcel of air, hitting it, that's IAS. The pressure is being directed downwards - that's how we are flying!

 

You've got me thinking now. I found this which shows you what your ASI is actually showing you. http://www.rst-engr.com/rst/articles/KP89JUL.pdf

So why it is said the rate of climb is unaffected, the horizontal distance covered in a headwind is effected, and would be less.

 

Let me confirm.

 

The rate of climb is the height gained over a certain time interval. Say if we had a headwind, the ground speed is going to be less. We are going to not travel as far horizontally as opposed to no wind. Is the actual speed at which you climb less? Hence why we only climb to the same/similar altitude as a best rate of climb with no wind, which would cover a greater horizontal distance, but do so because it is at a greater speed?

 

 

[Fishla]

The rate of climb is the height gained over a certain time interval.

Yes.

 

Say if we had a headwind, the ground speed is going to be less.

Yes.

 

We are going to not travel as far horizontally as opposed to no wind.

Yes.

 

Is the actual speed at which you climb less?

No. The time taken to climb to the same height is the same.

 

Hence why we only climb to the same/similar altitude as a best rate of climb with no wind, which would cover a greater horizontal distance, but do so because it is at a greater speed?

Yes.

 

So why it is said the rate of climb is unaffected, the horizontal distance covered in a headwind is effected, and would be less.

Below you see a picture with two different climbs. Same aircraft, same everything. Except for the prevailing wind.

 

Vertical axis is height.

 

Horizontal axis is distance across ground.

 

You see a green line. This had a headwind.

 

You see a purple line. This had no headwind. Maybe even a tailwind.

 

The picture shows the height of both of the climbing lines at the SAME INSTANT in time. See that they are both the same height after the same elapsed time? They had the same RATE of climb.

 

But the purple line has covered a greater distance across the ground. The green line had a higher ANGLE of climb.

 

The red thing is an obstacle.

 

 

 

[NljbA380]

I think im just going to have to accept it for what it is at this stage. For some reason i just cant grasp it.

 

If there doing it at the same speeds, the best angle of climb will have a higher attitude, will cover less ground distance, but reach the same height. Where as the best rate of climb will have a lower nose attitude, and cover more horizontal distance, which would be better for fuel encomy. Where as the best rate would be more appropriate for takes off where there are obstacles at the end of the runway.

 

So generally speaking, is it preferred to use a best rate of climb, since your covering more ground distance which would be mean you going to save time (fuel) and because you have better visibility because of the lower nose attitude.

 

I just dont understand how they can be the same altitude after the one min, and not have different speeds. If they had different speeds, that would make sense, what is the difference between them. Sorry if im being a pain.

 

 

[Ada Elle]

Not quite correct. If by "the stall speed" you mean the published stall speed of your aircraft, then you certainly can fly slower than that speed and still not descend. The published stall speed will be for MTOW, no power, 1 G and straight and level flight. If you fly at less than MTOW (kick out the passenger and have low fuel) and with power on you can fly at much lower speeds than the published stall speed and still not descend and even climb.

Power should not affect stall speed, right? It's a purely aerodynamic phenomenon: the speed at which the gravitational force is balanced by the lift force at the stalling angle of attack. That's what I mean by stall speed, not the published speed.

 

If there doing it at the same speeds, the best angle of climb will have a higher attitude, will cover less ground distance, but reach the same height. Where as the best rate of climb will have a lower nose attitude, and cover more horizontal distance, which would be better for fuel encomy. Where as the best rate would be more appropriate for takes off where there are obstacles at the end of the runway.

So generally speaking, is it preferred to use a best rate of climb, since your covering more ground distance which would be mean you going to save time (fuel) and because you have better visibility because of the lower nose attitude.

 

I just dont understand how they can be the same altitude after the one min, and not have different speeds. If they had different speeds, that would make sense, what is the difference between them. Sorry if im being a pain.

They're not the same altitude after one minute - that example was BRoC with a headwind and without a headwind.

 

Best angle of climb usually has a lower speed and lower rate of climb than best rate of climb. You use best angle of climb to clear fixed obstacles. Otherwise you use best rate of climb because altitude is life and you want to gain options as rapidly as possible.

 

 

[Happyflyer]

Power should not affect stall speed, right? It's a purely aerodynamic phenomenon: the speed at which the gravitational force is balanced by the lift force at the stalling angle of attack. That's what I mean by stall speed, not the published speed.

Yes power does affect stall speed, so does weight, g forces, flaps, wing contamination. There are some very good answers here and some confusing answers, unfortunately if you don't know which is which it is hard to learn like this. You need to have a good face to face discussion with your instructor with a model in hand and get a good grasp of these concepts. Cheers.

 

 

[Ada Elle]

Yes power does affect stall speed, so does weight, g forces, flaps, wing contamination. You need to have a good face to face discussion with your instructor with a model in hand and get a good grasp of these concepts.

Forgot about the vertical component of thrust - but if the wings are past a stalling AoA, how does power help?

 

 

[Happyflyer]

Forgot about the vertical component of thrust - but if the wings are past a stalling AoA, how does power help?

It doesn't, if the critical angle of attack is exceeded you will stall no matter what. Adding power allows that to happen at a slower speed.

 

 

[planesmaker]

I think im just going to have to accept it for what it is at this stage. For some reason i just cant grasp it.If there doing it at the same speeds, the best angle of climb will have a higher attitude, will cover less ground distance, but reach the same height. Where as the best rate of climb will have a lower nose attitude, and cover more horizontal distance, which would be better for fuel encomy. Where as the best rate would be more appropriate for takes off where there are obstacles at the end of the runway.

So generally speaking, is it preferred to use a best rate of climb, since your covering more ground distance which would be mean you going to save time (fuel) and because you have better visibility because of the lower nose attitude.

 

I just dont understand how they can be the same altitude after the one min, and not have different speeds. If they had different speeds, that would make sense, what is the difference between them. Sorry if im being a pain.

I think you have mixed the terminology and confused yourself.

Best angle of climb is done usually at a lower airspeed but higher angle of attack( nose high) to clear obstacles but gives a lower rate of climb eg500ft/min which may only result in 1.5kms to arrive at 1000ft but take 2 mins. this is used to clear obstacles.

 

Best rate is done at higher airspeed & will give you altitude faster but over a greater distance on the ground eg 700ft/min& 2 km to get to 1000ft(about 1.5 mins ) just as an example

 

So best angle is in relation to the ground, best rate in relation to time.

 

 

[NljbA380]

I think you have mixed the terminology and confused yourself.Best angle of climb is done usually at a lower airspeed but higher angle of attack( nose high) to clear obstacles but gives a lower rate of climb eg500ft/min which may only result in 1.5kms to arrive at 1000ft but take 2 mins. this is used to clear obstacles.

Best rate is done at higher airspeed & will give you altitude faster but over a greater distance on the ground eg 700ft/min& 2 km to get to 1000ft(about 1.5 mins ) just as an example

 

So best angle is in relation to the ground, best rate in relation to time.

Haha, yes. I have indeed. Its just i asked if the airspeeds differ before and was told they dont. which is what confused me even more. But i referred back to my book again, and basically its saying for one minute of time, a best angle of climb will produce x altitude gain, over a smaller horizontal distance, at a steep angle of attack with a higher attitude and because of this a lower speed.

 

Where as a best rate of climb will produce a climb that is at a lower angle of attack and hence a lower attitude, will cover more horizontal distance, and will reach the similar altitude in the same time because it is doing so at a higher speed.

 

If they were to complete both these two climbs, at the same speed and the same time interval, the best angle of climb would clearly gain a larger amount in altitude Correct?

 

 

[planesmaker]

No. If you climb best angle may only give for example 500ft/min take 2 mins to 1000ft whereas best rate will yield say 700ft/min and only take 1.5 mins to 1000ft but cover a greater distance. Usually used where you are doing a nav and want to climb to say 5500ft and cruise, so it will get you to altitude faster and cover the distance faster( both desirable)

 

Best angle usually only used to clear an obstacle and usually only used for as short a time as possible (cooling, visibility etc)

 

Best angle maybe at 60kts best rate maybe at 80kts just as an example

 

 

[Happyflyer]

If they were to complete both these two climbs, at the same speed and the same time interval, the best angle of climb would clearly gain a larger amount in altitude Correct?

Remember the only difference between flying at best rate and best angle is the air speed, so you can't do the two climbs at the same speed. Your aircraft flight manual gives you the one and only speed you fly for best rate and the one and only speed you fly for best angle (which will be lower than best rate).