Speed control - pitch or power?

[Shaggy Sheep Driver]

John Farley's excellent articles in 'Flyer' have opened up this for discussion this month. On the approach, do you use elevator or power to control speed?

As John points out, in a glider it had better be pitch. Years ago when I did my PPL on C150s I was taught to use pitch for speed, power for rate of descent. When I checked out in a Yak 52 a few years ago the technique was to use power for speed and pitch for flightpath control (point it at the numbers and fly a curved approach using power to control the speed). So maybe for low powered machines think 'pitch', for high powered think 'power'? Check out the article to see how John demonstarted to an 'always use pitch' instructor that it's not as simple as that.

Over the years I've worked out my own theories on this. What do you guys think???

SSD

[bluskis]

For piston pilots,
I am sure there has been a very recent thread on this subject, with a good crosssection of views on the two approaches, the conclusion of which was its horses for courses and use which ever you are comfortable with.

I think the crux was in one thread where the poster made the point that the mix of power and attitude resulted in the same reaction by the airplane regardless of how the pilot was thinking.

For turbine pilots immediate response from the motors cannot be expected and the heavy planes have inertia effects to consider, so I think this is why potential airline pilots use elevator to control flight path, therefore power to control speed.

[FlyingForFun]

Agree with bluskis - you'll end up adjusting both anyway, so in an aircraft without very much momentum and with engines which respond quickly, it doesn't make much difference which you do first. In fact, I think once I got to the stage where things started to happen automatically, I've been adjusting both at once - I certainly couldn't tell you which I adjust first without having to think very hard about it.

FFF
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[Final 3 Greens]

I was taught on SEPs to use pitch to control speed and power to control sink.

During 10+ hours of flight sim work on a medium jet sim with an airline pilot, I was taught pitch for sink, power for speed.

Both work well in the respective contexts.

I reckon that light aircraft are much more 'seat of the pants 'than' fly by the numbers', so it probably doesn't matter so much what you do, so long as you protect the flight envelope carefully, whereas the jet environment is different for the reasons quoted by Bluskis.

[Shaggy Sheep Driver]

Like some here, I use both and couldn't really tell how - I just do it. But I certainly use power to add or subtract 'energy' from the situation (too much speed or height - reduce power. Not enough of either or both, add power).

SSD

[QDMQDMQDM]

Like some here, I use both and couldn't really tell how - I just do it. But I certainly use power to add or subtract 'energy' from the situation (too much speed or height - reduce power. Not enough of either or both, add power).

In a low-speed aircraft like the Cub / Super Cub, I think you have to use pitch to control speed and power to control sink because using the engine doesn't make much difference to speed.

QDM

[Keef]

Having read this, I decided to try it out today on our jolly. I watched what I did (IYSWIM). It's both, but with a tendency to use specific settings for specific purposes - so 17 inches, 2300RPM for a "normal" approach, then pitch to control both speed and sink.

That works up to a point, then power has to be added or subtracted for coarser corections. There are a lot more pitch changes than power changes on a typical Keef approach.

Not sure what that proves - but I did like the John Farley article and his way to show the bemedalled CFI his point!

[Mike Cross]

Pitch to control sink can be a bit dodgy if you arrive high and haven't got much in the way of flap or airbrake to slow you down.

If you are a bit too high and point it at the numbers you can arrive with too much speed, a long float or possibly a wheelbarrow.

Taking the power off and keeping the speed back by not pointing the nose down can mean you take longer to arrive and lose more height.

Hopefully you have a headwind on final, so take an extreme example. 45 kt headwind 45 kt airspeed you will go down vertically. Stuff the nose down to 65 kt. You will increase your sink rate but also your forward speed and will land 20 kt x whatever time it took further along the runway.

The greater the differential between airspeed and the headwind component the less the effect.

Of course the real answer is to get the approach right so you are not too low and dragging it in with power or too high with full flap and very little power.

I was taught to use pitch to maintain airspeed and power to adjust rate of descent. I think this is easier for the beginner to assimilate. Once you know your aircraft you can experiment but a student needs a straightforward rule rather than a whole bundle of pitch/power/flaps/sideslip combinations to choose from.

I suspect my approaches have not got any better, I've just become more adept at juggling the options. At least in a Luscombe I only have three to play with (no flaps) which gives me one less thing to worry about.


Mike

[OBK!]

Maybe worth some practical experiments (with sufficient heigh to recover by 3000ft of course!).

But come to think of it, as a PPL student I was always told to set power and modify the speed of the aircraft with elevator. I think it's the SECONDARY effect of doing this which concerns the vertical profile aircraft, so then you have to play with the power more. So thinking back to basics, it is pitch for speed, power for vertical speed.

Picture this, you where 50ft above the ground and entered a full developed stall i.e buffeting/falling out sky. What would you do first? An autonomous reaction from your subconcious mind may think "ahh! ground! stall! pull back!" but it should be infact be pitch forard and then power? It's weird! I like to stick to the idea that they before work nicely together, and I almost always do power/pitch together.

[bluskis]

Then there is the rudder to think about in those gusty crosswinds.

The throttle in turbulent arrivals at say Gibralta and Elstree.

And the time when you realise you have rounded off too high, it is definitely power to control descent then.

Short field landings if I remember correctly, drag in with power and power off to touch down.

And pitch controls everything in a forced landing, except for some sideslipping and flap making up for lack of throttle control to reduce power.

No wonder it takes time to get those landings right.

[Final 3 Greens]

OBK!

So thinking back to basics, it is pitch for speed, power for vertical speed.

It's contextual in reality.

In a jet airliner it's definitely pitch to control vertical speed, power to control airspeed. (That's the way airlines train their pilots)

I believe that the US Navy also take the same view, although that's second hand info.

Bluskis

And the time when you realise you have rounded off too high, it is definitely power to control descent then.

It's power and pitch in concert really isn't? Don't you add the power which has two effects (a) an instant pitch up moment and (b) increase of airspeed, causing increased lift from the wing, both factors reducing the rate of sink, cushioning the landing.

[vancouv]

I was definitely taught power for height, pitch for speed, and that is certainly how I fly. If I'm too high on an approach then I take power off, and only adjust pitch to maintain my airspeed.

If I remember correctly in the book 'Stick and Rudder' the author also agrees with that, although a friend has borrowed it so I can't check!

I guess when you're learning it makes it a lot easier to be taught a specific method - if my instructor had said 'do whatever you want' when I was learning I don't think it would have helped me much.

But if you're flying with someone who approaches and lands perfectly (maybe one day that will be me!! :mad:) who cares which way he thinks he's doing it?

[Shaggy Sheep Driver]

Of course the real answer is to get the approach right so you are not too low and dragging it in with power or too high with full flap and very little power.

What's wrong wiv the latter??

SSD

In a jet airliner it's definitely pitch to control vertical speed, power to control airspeed. (That's the way airlines train their pilots) I believe that the US Navy also take the same view, although that's second hand info.


According to the Article by John Farley that started this thread, the USN is unusual in jet circles in using 'pitch for speed'.

SSD

[Final 3 Greens]

SSD

According to the Article by John Farley that started this thread, the USN is unusual in jet circles in using 'pitch for speed'.

Just shows that one should not rely on second hand info! I have ordered Flyer today, since JF is definitely worth reading.

[MLS-12D]

I'm no navy pilot, but I believe SSD is correct about the USN's practice. Probably most of us have seen that tape of the jet fighter going too low on the glidepath, to which the LSO responds by radioing "power ... power ... POWER! Eject! Eject!" (pilot punches out and a/c slams into the stern of the ship). If he thought that the airplane was too low and in danger of crashing, I can't see why he would want to increase the speed; so presumably he wanted to arrest the rate of sink.

Personally speaking, I always use the stick to control airspeed, and throttle/spoilers to control sink. But then, all of my experience has been in saiplanes and light airplanes.

Here are two related articles that may be of interest:
http://www.avweb.com/news/columns/182210-1.html
http://www.mwenda.com/stick.htm

[bluskis]

F3G

I was talking about the (very rare) times I have flared too high, I would not at that point want to pitch up, merely brake the rate of descent by adding power, of course with a twin prop wash adds a little aerodynamic lift as well.

[High Wing Drifter]

I was definitely taught power for height, pitch for speed...
What about when the thrust source is above the drag line?

[MLS-12D]

http://godscopilot.com/flight-03.htm

MLS-12D

P.S. For what it's worth, the unofficial USN site "Gerber Gouge" [http://www.navygouge.com/primary/gerber.html] says: "Remember, control airspeed with nose attitude and rate of descent with power".

P.P.S. What does Langewiesche says about this debate?

[Final 3 Greens]

Bluskis

Sorry, I wasn't clear. What I meant was that the very act of adding power tends to cause a pitch up to some extent, rather than suggesting that you would add back pressure.

[tmmorris]

It certainly seems the RAF are promoting power for speed at the most basic level: I was being encouraged to pursue that method in a G115 (which is about as light as the RAF aircraft get!) on Wednesday afternoon, by an instructor who is also a qualified civvy FI. I found it perverse; all my instincts from my own training are power for sink rate, pitch for airspeed.

The 2nd time I got it beautifully right and greased the landing - 2 feet above the runway. We then plonked down unceremoniously. I'd failed to get the 'picture' right for an unfamiliar plane!

Tim

[redbar1]

There are no exemptions from the laws of nature. One way of putting it basically is : 'If sink-/climb-rate is controlled with the stick, why do we use engines for takeoff?'. This settles the pure physics for most students. ;)

In the 'real world' of course there are a lot more practical aspects to consider in addition. Say for instance in one extreme you fly some fuel-to-noise-converter with thrust/weight ratio > 1:1 (F-15, etc). Then of course you can control almost 'any way you want'.

Most small pistons are on the other extreme relatively slow and low-powered. One poster mentioned shortfield ops; if you're going to have a shot at SHORT shortfield ops, having the physics sorted out becomes essential. And as another poster already pointed out, in a low-altitude stall, it's no bad idea to have the reflexes right!

And then it is back to the 'power vs altitude and stick vs. speed/AoA' for the students.

(And, not least, to save their training day, the 'Any landing you can walk away from is ok. And if the next student actually can use the same plane, it was a good one') :ok:

cheers,

[Final 3 Greens]

Redbar

'If sink-/climb-rate is controlled with the stick, why do we use engines for takeoff?'

erm........to control the airspeed for takeoff?

I think a clever student could hoist you with your own petard :)

[pulse1]

I was having a bit of trouble with my landings about 18 months ago. When I had my last check flight I was told off for using power to increase speed on the approach. I realised that my problem was that I had started to use point and power without realising it. (Too much time wasted flying fast things on FS).

The instructor then demonstrated that, with the C152 trimmed for 70k, a big increase in power just made the nose come up which then destabilised the approach. He made the same point as Redbar.

Since then I have gone back to controlling speed with pitch(& trim) and rate of descent with power. My landings are now much better and confidence is restored.

I am not saying that point & power isn't a good way of doing it but, because you need to keep retrimming, I have found it much more difficult to maintain a stable approach.

[redbar1]

Final 3 Greens,

;)
First, please allow me to quote again:
'If sink-/climb-rate is controlled with the stick, why do we use engines for takeoff?'
All climbing consumes energy, just as all descending releases energy. I hope we agree on that! If I could control the input/output of energy with the stick, all I would have to do to take off was pull back.

Unfortunately, I have yet to see that happen; the stick contains darn little energy at start of take-off roll. We all have to use throttle to increase the energy availible, to take off. That's the physics. THEN we use the stick to obtain the wanted AoA, resulting in a particular airspeed. Sorry, but blame old Newton, not me! :ok:

Cheers, and happy landings (and take-offs)

[Shaggy Sheep Driver]

No matter what method pilots develop later on, I'd recommend all students to use pitch for speed, power for rate of descent. You have to have a 'method' to learn the basics, and for light singles this one works.

I'd be surprised if PPL instructors taught anything different.

SSD

[Final 3 Greens]

Redbar

I think you missed my point mate - I wasn't arguing physics, just playing around with words ;)

Anyway, I'm pleased to have learned that airliners don't obey the known laws of physics. I'm off to flat earth lessons next. :D

SSD

Agree with you view. pitch for speed, power for sink is safe for students and works well in light singles.

[skydriller]

This is a really interesting thread, Ive been thinking about what I do myself, but Im afraid I just....erm...sort of .....do it naturally.......as needed for a smooth approach etc. and I cant remember what I was taught!!

No doubt the next time I fly I shall probably spend time trying to work it out:rolleyes:

Is there by any chance a copy of Mr Farley's article available online? Flyer is a little hard to come by in France!!

Regards, SD.