Pitch controls altitude. Power controls airspeed?
Thread Starter
Join Date: Jun 2005
Location: Australia
Posts: 38
Likes: 0
Received 0 Likes
on
0 Posts
Pitch controls altitude. Power controls airspeed?
Does pitch control altitude or does pitch control airspeed?
I would of thought it was a combination of both, but some people I've recently spoken to are adamant that its one way and not the other.
Interested to hear people's opinion on this one.
I would of thought it was a combination of both, but some people I've recently spoken to are adamant that its one way and not the other.
Interested to hear people's opinion on this one.
Grandpa Aerotart
Light aircraft have very little inertia so attitude changes effect airspeed quite quickly...so does power. Varying power in a propeller aircraft varies lift over the wing because of prop wash, as well as IAS....particularly in twins.
A jet has relatively huge inertia (I landed a B767-300 at 133000kg this afternoon- compare that with a C152...about 500kgs from memory?) and the fact that there is no 'prop wash' over the wings.
Also jets approach 'behind the drag curve'. Jets typically approach in an attitude between O ish (B767) and 5 degrees nose up (Falcon corporate jet). The two extremes of my personal experience.
In a jet there is no increased lift until after, essentially, the speed increase...in a prop the lift increase is instant (prop wash) and happens before the IAS increases.
So a large aircraft with lots of inertia is a little slow...and you lower the nose to regain that 5 kts or so...result = huge rate of descent with little speed increase because of the inertia....result is ugly.
Instead increase thrust and speed increases quite quickly but with little variation in approach flight path...because of inertia.
The correct way to think about it, as a concept, is power/thrust=IAS and attitude=Flight path but it can be a little difficult to grasp when you are learning to fly in an aircraft with so little inertia (and vastly different secondary effects of power/thrust).
Sorry if this aint as succinct as usually....secondary effects of red wine
A jet has relatively huge inertia (I landed a B767-300 at 133000kg this afternoon- compare that with a C152...about 500kgs from memory?) and the fact that there is no 'prop wash' over the wings.
Also jets approach 'behind the drag curve'. Jets typically approach in an attitude between O ish (B767) and 5 degrees nose up (Falcon corporate jet). The two extremes of my personal experience.
In a jet there is no increased lift until after, essentially, the speed increase...in a prop the lift increase is instant (prop wash) and happens before the IAS increases.
So a large aircraft with lots of inertia is a little slow...and you lower the nose to regain that 5 kts or so...result = huge rate of descent with little speed increase because of the inertia....result is ugly.
Instead increase thrust and speed increases quite quickly but with little variation in approach flight path...because of inertia.
The correct way to think about it, as a concept, is power/thrust=IAS and attitude=Flight path but it can be a little difficult to grasp when you are learning to fly in an aircraft with so little inertia (and vastly different secondary effects of power/thrust).
Sorry if this aint as succinct as usually....secondary effects of red wine
Last edited by Chimbu chuckles; 3rd Jul 2005 at 17:20.
Guest
Posts: n/a
a simple test - fly straight and level at 75% power in a 152/172, then push the throttle in. the first action is a pitch up, and an increase in altitude (if you do nothing else). speed comes secondary. it's the same on approach. full flap, leave power set at 1500, then try climbing. you'll soon reach the stall.
i guess that at the stall, pitch controls airspeed, but more importantly, at that time, it controls (influences?) a of a. power just helps reduce altitude loss. if power and pitch were inclusive of each other though, gliders would never fly would they?
i guess that at the stall, pitch controls airspeed, but more importantly, at that time, it controls (influences?) a of a. power just helps reduce altitude loss. if power and pitch were inclusive of each other though, gliders would never fly would they?
If you are high and on speed, you will need to reduce power AND lower the attitude. If you are on glide slope but slow, you will have to increas power AND lower the nose.
It is always a combination of both and you ALWAYS have to adjust both to vary speed, flightpath or both. Trying to seperate one from te other is pointless.
It is always a combination of both and you ALWAYS have to adjust both to vary speed, flightpath or both. Trying to seperate one from te other is pointless.
There is generally more than one way to skin a cat, as the saying goes, and the concept of what controls what is just something that helps us get our thinking straight when we fly.
I've always found it useful for climbs, cruise and descents other than final approach to use attitude for airspeed, and power for rate of climb/descent. Naturally the two affect eachother, but it gives you an effective control technique to use to fly accurately. For example, say you wanted to descend at 140 kt and 500 fpm; set an appropriate descent power and attitude for the type, adjust the attitude to get the right IAS, see where your ROD stabilises. If it's too high, add an increment of power - you will then have to raise the attitude a bit to maintain the speed (in practice, you'd do both at the same time). So it's just a way of thinking, rather than a black/white argument.
For finals, though, you're aiming to fly a particular glide path - I imagine a set of rails leading from an appropriate 'gate point' at the commencement of final (height, distance out and speed), and use attitude to fly down those 'rails', now adjusting IAS with power.
Some people do this differently; ie continue to use attitude for IAS on final and power for where they're going to hit the ground. I like the preciseness of setting aim point directly with attitude, but it's just personal preference; you say tomayto, I say tomahto kind of thing.
I've always found it useful for climbs, cruise and descents other than final approach to use attitude for airspeed, and power for rate of climb/descent. Naturally the two affect eachother, but it gives you an effective control technique to use to fly accurately. For example, say you wanted to descend at 140 kt and 500 fpm; set an appropriate descent power and attitude for the type, adjust the attitude to get the right IAS, see where your ROD stabilises. If it's too high, add an increment of power - you will then have to raise the attitude a bit to maintain the speed (in practice, you'd do both at the same time). So it's just a way of thinking, rather than a black/white argument.
For finals, though, you're aiming to fly a particular glide path - I imagine a set of rails leading from an appropriate 'gate point' at the commencement of final (height, distance out and speed), and use attitude to fly down those 'rails', now adjusting IAS with power.
Some people do this differently; ie continue to use attitude for IAS on final and power for where they're going to hit the ground. I like the preciseness of setting aim point directly with attitude, but it's just personal preference; you say tomayto, I say tomahto kind of thing.
Bottums Up
I feel safe in saying that most if not all pilots will accept the following statement.
To take off from rest an aeroplane needs to accelerate to reach flying speed and then rotate to become airborne.
Now, if attitude controls airspeed, then to take off one should line up, lower the nose to accelerate down the runway, and then when flying speed is reached and one wants to climb, a climb being a negative descent, then one opens the throttle to achieve the requied RoD.
When you do this, please let me know, I want to watch.
IF you accept that the primary effect of power is airspeed, and the primary effect of pitch attitude is flight path, then you have it skun. As with most things there are secondary effects of both pitch and power. It all comes down to energy management, and IMHO, power for speed & attitude for flight path are the easiest to come to terms with and the most logical too, and as illustrated in my take-off scenario above, doesn't change with the flight regime.
To take off from rest an aeroplane needs to accelerate to reach flying speed and then rotate to become airborne.
Now, if attitude controls airspeed, then to take off one should line up, lower the nose to accelerate down the runway, and then when flying speed is reached and one wants to climb, a climb being a negative descent, then one opens the throttle to achieve the requied RoD.
When you do this, please let me know, I want to watch.
IF you accept that the primary effect of power is airspeed, and the primary effect of pitch attitude is flight path, then you have it skun. As with most things there are secondary effects of both pitch and power. It all comes down to energy management, and IMHO, power for speed & attitude for flight path are the easiest to come to terms with and the most logical too, and as illustrated in my take-off scenario above, doesn't change with the flight regime.
Join Date: Dec 2004
Location: back to the land of small pay and big bills
Age: 50
Posts: 1,218
Likes: 0
Received 0 Likes
on
0 Posts
The original post was pitch controls altitude? (not attitude)..
...so the answer would be...well...yes
..oh and were you reffering to the approach phase on instruments or just basic handling?
..makes a difference!
...so the answer would be...well...yes
..oh and were you reffering to the approach phase on instruments or just basic handling?
..makes a difference!
Join Date: Apr 2005
Location: home
Age: 38
Posts: 27
Likes: 0
Received 0 Likes
on
0 Posts
quote:
--------------------------------------------------------------------------------
If you are high and on speed
--------------------------------------------------------------------------------
Ummm should you really be flying???
--------------------------------------------------------------------------------
If you are high and on speed
--------------------------------------------------------------------------------
Ummm should you really be flying???
If you're flying a glider, mamakin, there's only one correct answer: attitude = airspeed (ignoring speed brakes and any other lift reducing/drag enhancing device).
If you're flying anything that's heavier than air and not a glider or a rocket at the time you're flying it, then the answer depends on the power to weight ratio and aerodynamic design factors of the specific aircraft.
If you're flying anything that's heavier than air and not a glider or a rocket at the time you're flying it, then the answer depends on the power to weight ratio and aerodynamic design factors of the specific aircraft.
Join Date: Feb 2004
Location: NZ
Posts: 835
Likes: 0
Received 0 Likes
on
0 Posts
I think the phases of flight being refered to by the question are a steady (not zoom) climb or stable descent, particularly descent on final.
The correct explanation was given by Wizofoz - it is ALWAYS a combination of both. The combination depends on the aircraft as has also been stated. The reason you need both variables is due to the 2 dimensional nature of the flightpath (on approach), if you maintain a constant attitude and use power to change airspeed you are not in direct control of glidepath.
As a student pilot in a light single you are best to take the advise 'power controls rate of descent, attitude controls airspeed.' While not totaly correct it will give you the cues required to fly a stable approach. It may be usefull to keep in the back of your mind that 'power and attitude control rate of descent and airpeed'.
The correct explanation was given by Wizofoz - it is ALWAYS a combination of both. The combination depends on the aircraft as has also been stated. The reason you need both variables is due to the 2 dimensional nature of the flightpath (on approach), if you maintain a constant attitude and use power to change airspeed you are not in direct control of glidepath.
As a student pilot in a light single you are best to take the advise 'power controls rate of descent, attitude controls airspeed.' While not totaly correct it will give you the cues required to fly a stable approach. It may be usefull to keep in the back of your mind that 'power and attitude control rate of descent and airpeed'.
Manakim, as you can see there are a number of ways of looking at it!
No doubt a little bit of thought will allow you to make up your own mind; the people you mention who are adamant about the subject sound a bit closed-minded.
How about this? You're flying straight and level, and want to speed up. Power for airspeed? Fair enough, put some on, machine goes faster. Hang on though, holding the same attitude but now it's climbing. Hmmm....lower the nose a bit.
Stabilise at the new speed - attitude's lower now; and for any given airspeed, there will be a particular attitude/power combination that works. Power plus attitude equals performance, as the old saying goes.
This is one subject that we can no doubt talk about for weeks and end up back in the same place - a person's view will probably tend towards what they were taught originally.
We should probably switch the conversation to something like what's the best football code, that's something that can also go on for weeks.
No doubt a little bit of thought will allow you to make up your own mind; the people you mention who are adamant about the subject sound a bit closed-minded.
How about this? You're flying straight and level, and want to speed up. Power for airspeed? Fair enough, put some on, machine goes faster. Hang on though, holding the same attitude but now it's climbing. Hmmm....lower the nose a bit.
Stabilise at the new speed - attitude's lower now; and for any given airspeed, there will be a particular attitude/power combination that works. Power plus attitude equals performance, as the old saying goes.
This is one subject that we can no doubt talk about for weeks and end up back in the same place - a person's view will probably tend towards what they were taught originally.
We should probably switch the conversation to something like what's the best football code, that's something that can also go on for weeks.
As my old Flying Instructor used to say;
"The elevator is a funny control; when you pull back on the stick you go up. When you pull back further you go down!"
G Dunn circa 1964.
"The elevator is a funny control; when you pull back on the stick you go up. When you pull back further you go down!"
G Dunn circa 1964.
One of those situations which is not black and white, just shades of grey. One end of the band favours one view and the other end favours the other.
Typical engineering analysis for those interested.
For those heading towards military flying or airlines then it makes sense to train that way.
Aero club types should stick with the aero club style mentioned previously - especially with my aeroplane - it is definitely near one end of the grey scale and doesn't like being flown otherwise.
Must go - just opened a bottle of red wine.
Typical engineering analysis for those interested.
For those heading towards military flying or airlines then it makes sense to train that way.
Aero club types should stick with the aero club style mentioned previously - especially with my aeroplane - it is definitely near one end of the grey scale and doesn't like being flown otherwise.
Must go - just opened a bottle of red wine.
Mostly Harmless
Join Date: Nov 1999
Location: Oz (cold & wet bit)
Posts: 457
Likes: 0
Received 0 Likes
on
0 Posts
I'm deep in the heart of this, with 11.8 HRS in the logbook and just getting it together on the approach picture. I agree with everybody that says it's a combination of both, and my school was up front and told me it was a stepping stone. At some time in the future when I'm droning down the ILS in something bigger power = airspeed and pitch = rate of descent.
I can even conceive how it could be done together and reasonably automatically, but I can't do that yet.
Breaking it up into pitch=airspeed & power=rate of descent is helping me to see the whole situation by breaking a difficult task into two easier chunks. I look out the window, runway looks to be in the right spot and isn't "moving". I look at the speed, fark! 70K, it was 75 a 'second' ago, push the nose down a bit. Look at the runway, surprise surprise, it moving up the window, bit more power. Look at the speed, 75, pitch up a tiny bit. Look at the runway, etc.
So back to the original question, the equation is what your instructor says it is
edited by karrank, coz while he's real proud of figgering it out in the air he obviously (as pointed out kindly by somebody) hasn't really grasped the concept....
I can even conceive how it could be done together and reasonably automatically, but I can't do that yet.
Breaking it up into pitch=airspeed & power=rate of descent is helping me to see the whole situation by breaking a difficult task into two easier chunks. I look out the window, runway looks to be in the right spot and isn't "moving". I look at the speed, fark! 70K, it was 75 a 'second' ago, push the nose down a bit. Look at the runway, surprise surprise, it moving up the window, bit more power. Look at the speed, 75, pitch up a tiny bit. Look at the runway, etc.
So back to the original question, the equation is what your instructor says it is
edited by karrank, coz while he's real proud of figgering it out in the air he obviously (as pointed out kindly by somebody) hasn't really grasped the concept....
Last edited by karrank; 9th Jul 2005 at 05:28.
But karrank, what you say you do:
appears not be what you're actually doing!
If your response on seeing an IAS of “70K”, when “it was 75 a 'second' ago”, is to “push the nose down a bit”, it seems to me that you’re actually using pitch to control airspeed. If you add a “bit more power” to stop the runway from “moving up the window”, it seems to me that you’re actually using power to control ROD.
Hope that made sense!
pitch=rate of descent & power=airspeed
If your response on seeing an IAS of “70K”, when “it was 75 a 'second' ago”, is to “push the nose down a bit”, it seems to me that you’re actually using pitch to control airspeed. If you add a “bit more power” to stop the runway from “moving up the window”, it seems to me that you’re actually using power to control ROD.
Hope that made sense!
Thread Starter
Join Date: Jun 2005
Location: Australia
Posts: 38
Likes: 0
Received 0 Likes
on
0 Posts
OK - thanks everyone for the replies,
I think its fair and logical to say that its not one or the other but as wizofoz put it, a combination of both.
If I noticed my airspeed drop from 75 to 70 and I was on glideslope and I wanted to remain on glideslope, then I would do a combination of adding power and lowering the nose - nice and small movements, so I think you can argue either way but it comes down to combination movements in the controls.
But I was always told by my instructor that power controls height when on base and that power controls airspeed when on finals and I find that that mindset generally works although its often that I adjusting and fine tuning both all the time.
I think its fair and logical to say that its not one or the other but as wizofoz put it, a combination of both.
If I noticed my airspeed drop from 75 to 70 and I was on glideslope and I wanted to remain on glideslope, then I would do a combination of adding power and lowering the nose - nice and small movements, so I think you can argue either way but it comes down to combination movements in the controls.
But I was always told by my instructor that power controls height when on base and that power controls airspeed when on finals and I find that that mindset generally works although its often that I adjusting and fine tuning both all the time.