Pitch controls altitude. Power controls airspeed?

[Mamakim]

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.


:cool:

[jtr]

Typical Jet Transport

Pitch = RoD
Power = Speed

[GoNorth]

The typical aeroclub way of thinking is

Attitude controls airspeed, power controls rate of descent.

When you get out into the real world though this theory is soon slapped out of you.

[Chimbu chuckles]

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:E :}

[sir.pratt]

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?

[Wizofoz]

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.

[Captain Sand Dune]

Not this old chestnut again!!

Military teaches attitude for IAS and Power for RoD around base, and attitude for aimpoint and power for IAS on final.

[Arm out the window]

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.

[Capt Claret]

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.

[Chris Higgins]

Agreed.

Capt Claret gets the prize for using a great example as a demonstration. I'm going to plagarize it at my next instructor's rating renewal!

[mattyj]

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!

[Wingman09]

quote:
--------------------------------------------------------------------------------
If you are high and on speed
--------------------------------------------------------------------------------

Ummm should you really be flying???

[Creampuff]

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.

[Cloud Cutter]

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'.

[Arm out the window]

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. ;)

[Jungmeister]

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. ;)

[djpil]

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 (http://web.mit.edu/16.61/www/lectures/lecture17.pdf) 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.

[karrank]

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:8

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....

[Creampuff]

But karrank, what you say you do:pitch=rate of descent & power=airspeedappears 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!:O

[Mamakim]

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.

[Mr Garrison]

Yep - I agree with Mamakim on that one.

Thats what my instructor told me also.

:ok:

[OZBUSDRIVER]

Hope no newbie reads this....you guys are gonna get someone killed.

C152 flaps down and speed decaying and threshold rising in screen. AND you guys want to pull back to go up and power to maintain speed???? Have you forgotten what happens next?

Interesting. DHC4 with all the laundry out doing classic wheel barrow routine. Power increases and Caribou does what?

A lightie should be flown like a lightie. Do not understand the reason for imitating a heavy. I suppose I will learn this whilst trying to master an ILS for my CIR.

[Capt W E Johns]

I have to disagree with you OZBUSDRIVER. I think you will find that while trying to master your ILS you'll find it easier to control your glideslope (ROD) by selecting and maintaining specific powers, which leaves you only one way to control IAS. It's not a case of lighties imitating heavies, I think it's just the best way to fly the aeroplane.

My general philosophy on the original question is that pitch is the most powerful flight control, so it (generally) is used to control the performance you are most concerned about. There are exceptions, and at the end of the day you still need the old "string around the back of your neck", but it is something I find helps in coming to terms with the concept.

It's really as Arm out the window says...

Bottom line: "It depends" :-)

[Ibol]

Primary effect of elevator - Change in pitch and flightpath.

Secondary effect - you will get a change in airspeed.

Primary Effect of adding power/thrust - Change in speed.

Secondary effect - You will get a change in flightpath.

Why - o - why would you start controlling the aircraft with the secondary effects during the approach????

That's what the primary effects are for!!!! The secondary effects are a consideration (and sure,... with some more experience under your belt a combination of the two is possible.)

Pitch for path. Power for speed. Will work in a C152 OZBUSDRIVER!! Push the power in to add speed, pull the nose up to climb (with full flaps!). I know.. I've done it. This rubbish about immitating a heavy.... An aeroplane's an aeroplane. Big, small, fast, slow, heavy, light. They all work the same.

Pitch for path. Power for speed. They are the Primary effects!
Will work in a C152
Will work in a jumbo
and will work in every fixedwing aircraft in between.

[Capt Claret]

Thank the deity Ibol, some common sense.

Mamakim

You said, 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.

Why oh why do you want to subscribe to a belief that changes between base & final? If you stick with Ibol's, power for airspeed & pith for flight path, the belief is a constant through all regimes of flight.

[Creampuff]

But with the greatest respect cc, is it that simple?

One of the many complicating factors here, as I mentioned above, is the design of the aircraft. In particular, the interaction of the thrust/drag couple with the lift/weight couple (which is a function of aircraft design) has an impact on the primary effect of thrust.

My understanding is that many training aircraft are deliberately designed so that the interaction between the two couples has the following effects, among others:

First, if power is reduced and no other control is touched, the aircraft automatically pitches down to maintain about the same airspeed and, consequently, the aircraft will begin to descend;

Secondly, the reverse applies – if power is increased and no other control is touched, the aircraft automatically pitches up to maintain about the same airspeed and, consequently, the aircraft will begin to climb.

Thus, in aircraft designed this way, and usually at circuit/approach speeds in particular, it’s not just a case of “add power to get more speed”. If power is added on its own, the aircraft maintains about the same speed and begins to climb, and vice versa. To make it go faster, you have to push or trim nose down, and vice versa.

[Arm out the window]

Come on you blokes, stop clouding the issue for the poor learners!
There are numerous factors influencing what happens when we fly, but what they need are good ways of organising themselves to get the performance they want.

May I humbly suggest that for a starter (and depending on what you fly and what weight and conditions you're at, but a learner will generally be in a training machine at training weights), we use Power + Attitude = Performance.

Therefore, depending on the phase of flight you're in, set an appropriate power and attitude, trim, look out the front and let it all stabilise.
Next, note performance; is it what you want? Yes / No.
If yes, good.
If no, make a change depending on what's not right (and here's where opinions may differ, but it's all the same result really) -

For example - in a climb, too slow, already at climb power, so we must lower the attitude a bit to speed up.

Or: In a cruise S&L, too slow. We must add power to speed up, but ALSO lower the attitude as the speed increases so we don't climb.

Two situations, both need increased speed, but we use different control inputs to achieve our aim, because we're pilots and we have enough brains to pick the right thing to do in a given circumstance!

Saying that there's only one valid control technique is pointless; as I said before, we just need a way of thinking that works for us.
However, awareness of attitude is a very good thing because it tends to reduce overcontrolling and keeps you looking out the front - a fine habit to develop.
;)

[ConwayB]

Arm out of the window has the closest answer to which, IMHO is correct... a combination of both is required and is dependent on what flight regime you are in (as well as what aircraft you are in).

I was taught that on finals: Attitude for IAS, Power for ROD... That way you can 'ride the rails' on your final approach and make your aim point. (Aimpoint, Aspect Airspeed... Aimpoint, Aspect Airspeed.)

Some like it, others don't.

Just remember this from the formula for Lift:

Lift = Coefficient of Lift x 1/2 rho x velocity squared x wing surface area

So if you increase velocity, then CL or something else has to be reduced so that you don't increase lift and begin to climb. Solution, change the angle of attack of the wing to the relative airflow by changing the aircraft's attitude thereby changing CL

Answer: If you change speed (+/-), you must change CL by changing attitude (+/-) to maintain the same amount of lift (unless you can change air density [unlikely] or the wing's surface area [flaps, etc.])

That's my two cents worth, and it may be worth only two cents.

What WILL happen is that one day it will seem natural which sticks to push and pull to make the aircraft do what you want it to and you won't even think about it. (I'm still waiting for that day to arrive for me. ;-)

Safe Flying
CB

[Counter-rotation]

I'm surprised no one's mentioned the rules:

RULE #1 - Power + Attitude (+ Configuration) = Performance

Got that?!

Ohhhhh hang on :O that's Rule #2.

Rule #1 - ALWAYS LOOK COOL!!!! :cool:

CR.

[waav8r]

A lot of wise words have been said in this topic, but in IMHO the most important lesson is to abide by the laws of physics which ACTUALLY DO take into account the aerodynamic properties of the aircraft in question. You do not fly a propeller driven aircraft the same way you fly a jet powered aircraft. A propeller driven aircraft is typically very speed stable (as demonstrated during Attitude - Power - Trim exercises early during eberyones flying training) and it works very well indeed to trim the aircraft out for the desired speed while on G/S and use power changes to control the desired trajectory, ie the glideslope. In a jet - that is not the case, as you are on the back side of the power curve and typically unstable in speed.

To quote the classic BOEING compendium "Swept Wing Jet Characteristics":

Basic Rule No. 2:
Control airspeed with the throttles when thrust is variable. (Variable thrust - fixed flight path). Example Terminal area / approach / Holding Pattern / Slow Flight.

Basic Rule No. 3:
Control airspeed with yoke or pitch control when thrust is NOT a variable ( Fixed thrust - variable path)
Example Climb / Descent with idle thrust / Normal or high speed Emergency maneuvers (Engine out situations etc.)

Everyone do of course know what Basic Rule Rule Number 1 is, but as I always make an effort to complete the things I begin I sha

[ConditionLever]

You just get the speed right any way you can and keep the aiming point fixed in the windscreen. Both power and attitude control both speed and rate of descent. How can you say one control input only has one effect?

[Frickman]

I read an article in some flying mag years ago that basically explained how the idea of PITCH controling AIRSPEED was a bad habit introduced to the civil world after WW2 by inexperienced and (sometimes) poorly trained fighter pilot's.

A low hour pilot flying a mustang (for example) with a high speed, low drag, laminar flow wing would find that lowering the nose would result in a rapid increase of speed for a reatively small, or no appreciable, increase in ROD.

David Davies does a good job of explaining what happens if you try this in a large jet transport. You get (initially) a massive increase in ROD with a relatively small increase in speed.

[Creampuff]

From Aerodynamics for Naval Aviators pp 350-352 by H. H. Hurt, Jr. University of Southern California, published by U.S. Navy 1960, revised 1965:For the conditions of steady flight with a given airplane, each angle of attack corresponds to a specific airspeed. Each angle of attack produces a specific value of [lift coefficient] and each value of [lift coefficient] requires a specific value of equivalent airspeed to provide lift equal to weight. Hence, angle of attack is the primary control of airspeed in steady flight.

Primary control of airspeed in steady flight by angle of attack is an important principle. …

[T]he rate of climb in steady flight is a direct function of the difference between power available and power required. … For this reason, it is apparent that power setting is the primary control of altitude in steady flight. …

FLYING TECHNIQUE. Since the conditions of steady flight predominate during a majority of all flying, the fundamentals of flying technique are the fundamentals of steady flight:

(1) Angle of attack is the primary control of airspeed.
(2) Power setting is the primary control of altitude, i.e., rate of climb/descent.

With the exception of the transient conditions of flight which occur during maneuvers and acrobatics, the conditions of steady flight will be applicable during such steady flight conditions as cruise, climb, descent, takeoff, approach, landing etc. A clear understanding of these two principles will develop good, safe flying techniques applicable to any sort of aeroplane.[Italics and capitals in original text.]

[psycho joe]

From Handling The Big Jets
In a very slow approach to a stall the incidence can be controlled very accurately, and in this steady slow approach condition, from an initial trimmed- out steady state descent, incidence bears a fixed relationship to airspeed. But only under these strictly defined conditions. If anything at all should disturb the flight path then the assumed relationship between airspeed and incidence is lost.

[Sunfish]

Ibol, are you trying to get someone killed?

Ever heard of Coffin Corner? Little Sunfish and his instructor went there in a Cessna 150 one day and only just got out.

Jets and light aircraft fly by the same laws, but the "coefficients" are very very different. Light aircraft land relatively fast with no power. Heavies land relatively slow with more power.

In landing a light aircraft, control your speed by pitch attitude and use the throttle to maintain your flight path as you are taught. It's easier that way because the speed will respond quicker to pitch changes than to engine speed changes.

When you get to do short field stuff with full flaps, you are operating more like a heavy (closer to coffin corner) and you will need power to maintain your speed and find yourself adjusting attitude to get exactly on aimpoint.

My limited understanding of Heavy jets is that you are always landing much further down (or is it up?) the lift drag curve(in other words more drag and higher power) than light aircraft for two reasons.

1. To keep landing speeds reasonable.

2. To deliberately keep more power on since jets don't spool up instantaneaously, and you may need that power to go around.

OK all you experts, tear me to shreds.

[Capt Claret]

Sunfish,

Coffin corner doesn't apply to C150 et al. It's where, due to compressability, the Vmo and Vs meet.

Most lighties can't get high enough or fast enough when high to have the problem.

You said, In landing a light aircraft, control your speed by pitch attitude and use the throttle to maintain your flight path as you are taught. It's easier that way because the speed will respond quicker to pitch changes than to engine speed changes.

I was taught the same but 2 years later, by the time I became an instructor at the very same flying school, under a different CFI & HoT, I was directed to teach attitude for aim point, power for speed. (which at the time I thought was horse sh!t, because of course I was a grade three instructor and what did these ex military Grade 1 jocks know?? :\ , more importantly, it was contrary to what I was taught and what I knew!!!!!!)

So having learned one way and used both as an instructor I can no longer understand why folk want to persist with believeing that attitude controls speed and power controls RoD.

Sure, (presuming you do nothing with the power) if you lower the nose you'll gain speed, or if you raise it, you'll lose speed BUT you'll also alter the flight path.

As stated in an earlier post, IF one subscribes to the belief that the primary effect of power is to control speed, and the primary effect of pitch is to control the flight path then this premise applies to all flight regimes. One must remain cognisant of the secondary effect of pitch and power, but one doesn't have to change one's thinking just because one is in the circuit for a landing.

For example, if cruising along the beech at 500' enjoying the view one became aware that last light was encroaching and one needed to speed up to arrive before last light, would you
[list=1]
Lower the nose to speed up, or
open the throttle?
[/list=1]

[bushy]

If you are flying a chieftain down the ILS, and you use attitude to control airspeed, and power to adjust the rate of descent, it works beautifully.

[Arm out the window]

Clarrie, in answer to your question about the Beech along the beech, I'd do both!
Therein lies the answer.

[tinpis]

Hear hear bushy but if ya flying one them pointy jetty things it works all arse backwards.
If ya want to get down the ILS ya point the bugger down and use watever else you got to slow it down, most aces can leave the power at idle from TOD to late final http://www.augk18.dsl.pipex.com/Smileys/boogie.gif
If it gets a lil slow apply the kero
Bloody simple really but takes a while for old prop jockeys ta get the hang of it.

[Creampuff]

Yes clarrie, the "or" at the end of 'option' 1 is misleading.

My point (which I am comforted to note the author of Aerodynamics for Naval Aviators appears to support) is that if you just "open the throttle", you'll merely begin to climb without increasing airspeed, you won't get there any quicker (assuming you don't pick up a tailwind as you climb) and you will run out of juice sooner than you otherwise would have.

If you want to go faster, lower the nose. If you want to go faster and not descend, lower the nose and increase power.

[Capt Claret]

AOTW,

Why would you do both? If you just want to speed up, why don't you just lower the nose?

[Arm out the window]

Gunna have to get a lawyer in to vet my wording here by the looks. :D

How about instead of saying that power or attitude control airspeed, as one's preference may be, we go with something like 'Airspeed changes in level flight are made by changing power and adjusting attitude accordingly to maintain constant altitude.'

Far too dry but; maybe 'If I want to go faster I increase the power but then I straight away have to lower the nose a bit or else I climb.'

Or, 'Notwithstanding the aforementioned attitudinal or power adjustments, any changes in velocity will be instigated and accompanied by appropriate and fitting changes to the settings extant in attitude (being the visual relationship between the position of the horizon, to wit the perceived joining of sky and/or ground and sea, or the position where such joining may be reasonably assumed to be in the absence of a clear line of demarcation, and such parts of the aircraft in question in the pilot's forward line of sight as are necessary to establish said relationship) and power (that is, the setting of thrust, torque, pressure ratio or other accepted measure of output from an aircraft's powerplant or powerplants) which will be made in such a way as to complement one another and therefore allow the maintenance of an unvarying reading on the face of an instrument fitted to said aircraft for the purpose of measuring altitude.'

Yeah, that's better - sounds just like the CAOs now!

;)

[Sunfish]

If it was a regulation it would look like this:

278.1 A pilot shall not control speed by varying pitch attitude and flight path by varying power.

This is an offence of strict liability.

278.2 Regulation 278.1 does not apply to:

a) Balloons, or;

b) Aircraft with a gross weight of less than 5,700kg, when the pilot in command is:

1. The holder of a valid student pilots licence,or;

2. The holder of a valid Private pilots licence, or;

3. The holder of a valid commercial pilots licence, and the said licence holder does not posses a valid ATPL .

Translation: You do it your way, I'll do it like I was taught.

[v1rotate]

I was taught to use Power to control ROD and Pitch to control airspeed when I was first getting my instrument rating in a PA28. Works in a light aircraft but don't even think of doing it in a 20 tonne F27.

Did anyone get taught to use the rudders to maintain the localiser on the ILS. I always thought that was the worst technique to use. I don't even use my rudders anymore except on the runway during take-off and at the flare/roundout to maintain the aircraft straight.

[Super Cecil]

It's easier just to land the thing, older style steeper approach works for me.
If you treat any powerplant with the respect it deserves you don't bang the throttle on, recip, radial or turboprop.

[Lefthanded_Rock_Thrower]

Mamakim,

What type of aircraft are you talking about flying, light twins or Complex jets ?.

They are very different creatures.

[Mamakim]

I'm talking about small planes mainly.

But I'm also interested to hear about the big jets as well.

I'm tending to lean towards those that say its a combination of both rather than just one or the other. I.e -> I'm not taking the black/white approach......but more the grey (the combination!)

Thanks to all the people that have responded thus far.....seems like there are a lot of different opinions out there.


MK

[Zhaadum]

POWER CONTROLS AIRSPEED as PRIMARY EFFECT.

ATTITUDE (pitch) CONTROLS APPROACH PATH as PRIMARY EFFECT.

Plain and simple.

Today I was flying with a student in a light twin who had some previous twin training and was having BIG problems with circuits prior to his endorsement check flight. He was way LOW and FAST on early to mid final. I asked him how the approach was and he said LOW. So I said fix it. He ADDED POWER (wrong!) and we did not change flight path, the runway still appeared flat and we just speeded up still heading for a house prior to the airport boundary. (Increase of speed does produce pitch up tendancy due lift increase but it is a secondary effect that takes much longer to occur, and now you are more stuffed as you are closer, faster and still on an unstable approach. You should be slowing down towards your Vref anyway, not speeding up!)

I then told him on the next circuit to raise the nose for fixing the approach path and what do you know? We stopped decending, the runway picture lengthened to a normal appearance and the bloody speed (as a secondary effect) ceased being a problem.

We then proceeded to conduct several more circuits using POWER for SPEED and ATTITUDE for PATH (don't forget to trim each time speed changes) and this guy went from zero to hero! Couldn't land to save his life at first, then at the end perfect touchdowns on centreline on mains just after aim point in x-wind and a couple assymetric too.

Couldn't be simpler really.

Cheers! :ok:

[Arm out the window]

Yes mate, you refer to what I regard as the correct finals technique - elevator for aim point, power for airspeed. If low, temporarily shift the aim point further up the runway until approaching the right glide path, using power to maintain the correct speed, then reselect the numbers as the aim point.
Slightly different story round base though - no particular aim point, it's more an attitude for airspeed and see how you're going for height, add or subtract power depending on what height you should be at at a particular position and adjust the attitude to maintain the airspeed.
Also in the climb, you maintain airspeed with attitude. It's not as black and white as you say, it's a combination of techniques appropriate to what you're doing.
Having said that, the technique you describe above works very well for finals.

[Lefthanded_Rock_Thrower]

Zhad,

Using the technique you suggest, try doing an ILS or an constant profile NDB, I feel that what Arm out the Window is quite correct.

Also try being high in finals and use your technique ( especially in PA31 with 128 kt VLO ).

The beauty of the Attitude = Airspeed, Power ( flap and gear ) = Performance, it is a stable configuration.

From my experience in piston twin ( mainly PA31, C402, B58, C340, C310 ), an ILS for example i use the follwing for a C310/B58, it works a treat, it is an established approach, i.e. if i was to be distracted during my approach i would be plus or minus 100 ft and 5 kts of where i should be.

Assume, the ILS is 15nm long, you join from 3700 ft ( eg YBCS):

6nm to 1000ft descent to 3700 ft by 20nm CS, by 3700 feet 18-20 inches at 2400 rpm ( 18 light, 20 heavy ).

from 20nm to 18nm allow the aircraft to slow to about 150knots by maintaining 3700, then select APP Flap.

Airspeed should now be about 130 kts, at about half scale glide slope select Gear Down ( go down ), airspeed 120-130, ROD established ( adjust attitude / trim to suite ).

To maintain glideslope, your required ROD will be Ground Speed (GS) times 5 ( look at the trusty Garmin 100 ), check on VSI.

If you are not making your required ROD, adjust power 1 inch at a time, with about 20 seconds between adjustments to allow the VSI to catch up ( you may need to make small adjustments to the attitude to maintain required IAS ).

This is how i fly and this makes flying a approach in IMC very simple, it also is a very simple method of flying a visual cct.

I have not flown a big turbine or jet, i guess theres a reason they call them speed levers in a jet.

[Capt Claret]

Lefthanded_Rock_Thrower

I'm with Zhaadum. I've used both philosophies. I've tought both philosophies.

The premise that power primarily controls speed and pitch primarily controls does not change with flight regime and works with every powered aircraft I've flown from C152 to BAe146, and no doubt it works for B747 and A380 too.

Constant profile NDB or ILS, even the 15ILS or 33 LOC at Cairns, no problem - too fast, reduce thrust/power, as aircraft slows adjust pitch to keep aim point. Too low, raise nose to adjust profile and increase thrust/power to maintain speed.

Simple.

[Lefthanded_Rock_Thrower]

So how do you adjust aim point in IMC ?.

[Capt W E Johns]

You adjust aimpoint when IMC by changing your approach profile, just like you do when VMC. Your question, I suspect, is really 'how do you know where your aimpoint is when IMC'.

[Lefthanded_Rock_Thrower]

Capt Johns, Yes, exactly.

For the 30 year old aircraft that I fly, they are fitted with very ordinary Artifical Horizons ( certainly not a precise piece of equipment ), compared to perhaps a inclinometer / Angle of Attack Indicator in a big/newer machine.

The performance equipment, VSI and ASI that i use (of course there are delays in these instruments), but are relatively accurate tools to use compared to the AH, your thoughts ?.

[Capt W E Johns]

Yes, entirely agree with you LHRT - some AH's / AI's are not accurate enough to allow for very delicate setting of a powerful flight parameter, i.e pitch.

Also, in a lighty the attitude is much more prone to variances around than on heavy/fast aircraft.

For these reasons, when teaching ILS approaches I like to suggest using power to control rate of descent - I think trying to set an attitude to control ROD on an instrument approach is not very practical or accurate in my a/c types. I believe the same applies for most descent regimes, even visually. But that doesn't mean it's impossible or incorrect!

By setting an attitude for an airspeed, you're left with power to control ROD/glidepath. Not on glidepath? Adjust power by a very measurable amount (a few percent/psi/inches as your steed dictates), and wait for the results. Rinse and repeat! Sure, speed will now be your major variable, but for an ILS I'd rather accept a speed inaccuracy than an altitude error.

Anyway it's really a matter of semantics... connect both gloves with a piece of string running around the back of your neck, and you'll normally get it right. :)

[psycho joe]

By setting an attitude for an airspeed, you're left with power to control ROD/glidepath.

With regard to an ILS, angle of descent is fixed therefore rate of descent is dependant on airspeed but not controlled by airspeed. By setting POWER for airspeed and adjusting ATTITUDE for ROD = PERFORMANCE.

Sure, speed will now be your major variable, but for an ILS I'd rather accept a speed inaccuracy than an altitude error.
Why would you accept either??

[Chimbu chuckles]

LRT on a CANPA your adjust your path to the 'aim' point (a alt/DME dist) with reference to a profile. Therefore if you're off profile you change attitude to adjust your ROD (flight path) and use thrust to control your IAS.

If you are high what will effect change quicker...lowering the nose or reducing power/thrust? You want to effect chage quick because then you need smaller changes and can be more precise.

[Arm out the window]

It seems that on visual finals in a lightie, or on the ILS, the attitude for profile and power for speed works pretty well because you have a direct visual representation of 'how you're going' with respect to the desired glidepath.

However, in response to Psycho Joe, it's groundspeed that's important for angle of descent, not airspeed.
With fluctuating airspeed, for example (as Capt W.E. Johns says) in a lightie you are bouncing around; and so chasing the glideslope with attitude can be a pain in the arse, much more so than in something that's got a bit of penetration (oo-er matron!), therefore you may be better off selecting an attitude to stick around your desired airspeed as best you can, and make adjustments to power as you see a trend developing to hopefully peg the power that's going to give you an appropriate ROD for the average wind component down most of finals.

Then of course you'll get the hills and/or sea breeze stuffing it all up anyhow!

[Lefthanded_Rock_Thrower]

Chimbu,

In the lighties i fly, if you where to push forward as you suggest you speed up and go from the back of the drag curve to the front.

Going from the back of the drag curve to the front makes the profile problem worse, i.e less pwr required therfore more excess power, or in this case less deficiency of power ( less ROD for a higher ground speed ).

Remember the Forward and Reverse Command thing:

In the high end of the Drag Curve you pull back, a decrease in airspeed cause more excess power ( more climb / less descent ) - *Pull back, go up*.

In the back half of the drag curve, you pull back, the airspeed decreases and you have less excess power ( Less climb / more descent )- *Pull back, go down*.

With the big shiny aeroplanes that don't leak oil that you fly, what do you call them again,,,,,,, ummm,,,,thats right " Airliners", your drag curve is a lot larger in range ( for example 120- 500 kts ), therefore less steep, smaller changes in Excess power for the same airspeed change.

Then theres the "Hot stuff out the back is less efficient at low airspeeds compared to our propellors".