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Old 7th May 2012, 21:55   #1 (permalink)
 
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Attitude = speed control/power = pitch

WHAT?!

So backwards, I landed fine last time doing it my own way. And now today he introduced this pitch controls speed and power controls attitude. Is it MANDATORY? Or is it a widely used technique?
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Old 7th May 2012, 22:01   #2 (permalink)
 
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It's not carved in stone; it's more complex than that. But setting pitch for speed, power for rate of ascent / descent is a good way to learn.

Once you are qualified and start to gain experience you'll find a lot of what you were taught in the PPL process is just the beginning. You have to start somewhere, and doing it by processes and numbers works well until you have the experience to do it from first principles.
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Old 7th May 2012, 22:01   #3 (permalink)
 
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It's just a method to break it down into easy chunks when you are learning how to establish a constant steady approach.

A lot of civvy schools teach this method, if high or low adjust power to fix it, if fast or slow adjust pitch attitude. This is really just a way of thinking which to adjust first. If you are high you would reduce the power, but you would soon need to lower the nose or the speed will bleed off. One way of imagining this pairing of attitude and power is that your arms are linked by a piece of string, like you were wearing mittens as a kid. If you adjust one thing, e.g. reducing power, you do the opposite with the other hand, in e.g. pitching forwards.

The military tend to teach the opposite, power for speed and pitch for rate of descent, as this method works a lot better when you come to fly an instrument approach or fast jet. Either way it amounts to the same thing and is just a way of breaking it down in your mind into something more manageable.
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Old 7th May 2012, 22:06   #4 (permalink)
 
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Thank you very much. It made it more complicated for me, definitely won't be using that technique ever again, it was like adding unnecessary steps.

EGKB,
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Old 7th May 2012, 22:12   #5 (permalink)
 
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Pitch does control speed.

Power does control rate of climb or descent.


Some instructors will elect to teach it the other way around, and this does seem to work as well for instrument approaches in particular.

The reality is that they are inexplicably tied to each other because power also has a pitch effect, and pitching also creates a rate of climb or descent. In the vast majority of aeroplanes increased power causes a pitch-up and a reduction in trim speed, whilst a reduction in power causes a pitch-down and a consequent increase in trim speed.

So:

Correct approach angle / too slow = pitch down + more power
Correct approach angle / too fast = pitch up + less power
Correct speed / too high = reduce power + pitch down
Correct speed / too low = increase power + pitch up.

(And at the current stage in your training = if both are wrong, probably go around and try again next time; if feeling braver AND there's plenty of height to play with, sort out airspeed first, then flightpath).

G
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Old 7th May 2012, 22:40   #6 (permalink)
 
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That all means nothing to me, I'm a practical guy, everything sort of is simultaneous for me, doing several things at once...

I wonder how my other instructor teaches as I have't done any landings with him yet!
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Old 7th May 2012, 22:42   #7 (permalink)
 
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Once you start IFR flying you'll find that on the ILS, your position on the glideslope (pitch) is controlled by elevators and your speed (to keep the CAT behind from going up your chuff) is controlled by throttle (Power).

Confusing innit?

Cusco
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Old 7th May 2012, 22:52   #8 (permalink)
 
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Are you saying different instructors at the same school are teaching different techniques at this early stage in your training?
If so I suggest you seek clarification from the head of training.
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Old 7th May 2012, 22:54   #9 (permalink)
 
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Quote:
Originally Posted by EGKB View Post
That all means nothing to me, I'm a practical guy, everything sort of is simultaneous for me, doing several things at once...
It will help a lot to separate the effects out in your mind.

It is a foolish arrogance to think that you don't need these simplifications. I have a PhD in flight mechanics, and still find it vital to keep coming back to these simplified models in my flying.

Quote:
I wonder how my other instructor teaches as I have't done any landings with him yet!
Personally I think that switching instructors is a bad habit and you are better sticking with one so that you are learning consistent method. However, if they teach in the same school then they should be standardised on the same technique.

The pitch for speed approach I described is pretty much standard across VFR flight training worldwide. It works.

G
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Old 7th May 2012, 23:25   #10 (permalink)
 
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It's not arrogance at all, it's completely subjective, some methods work for some, some for others.

I'm not saying pitch doesn't control speed, it does. But to me everything is backwards, there's a reason why there's an elevator on the plane to control pitch, it worked for me perfectly on all approaches/landings so far except for today when I tried the opposite technique....

I'm not sure if they teach the same technique, I haven't landed with the other instructor, he was on my first lesson and I wasn't taking much no on the landing as to what he was doing.
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Old 7th May 2012, 23:29   #11 (permalink)
 
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You appear to have stumbled upon what's referred to as the "point and power" technique - much loved by instrument instructors and very relevant to a big jet like a 737.

But in VFR in a single engined light aeroplane, really I'd stick with the classic pitch for speed and power for rate of descent. If this takes a little getting used to after developing an initial bad habit - live with it!

And as I said, I would stick with one instructor and their way of doing things as far as you can. Neither will be wrong, but you don't need the chopping and changing.

G
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Old 8th May 2012, 00:44   #12 (permalink)
 
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Quote:
Once you start IFR flying you'll find that on the ILS, your position on the glideslope (pitch) is controlled by elevators and your speed (to keep the CAT behind from going up your chuff) is controlled by throttle (Power).
I've heard this one before, not saying it's wrong but on an ILS approach I always use the throttle to control glideslope.
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Old 8th May 2012, 00:53   #13 (permalink)
 
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I disagree with everyone and I will explain why!!!

Think of two power levers the throttle and the elevator.
The throttle will tap into engine power.
The elevator will tap into potential energy inherent in the airframe.

Take the simplest form! remove the engine from the equation ie a glider on a still day and there is only one form of potential energy to tap into to maintain speed and that is the potential energy in the airframe.
In that situation you have one power lever and that is the elevator.
Add an engine and you have two power sources available the airframe and the engine.

So really neither is correct as it is using both sources which is accurate.
Take a light draggy trainer with a low powered engine and pitching for speed becomes more important.

Take a high powered slippery aircraft and pitching for speed becomes less important while power for speed more important.

Really its a play between using two power sources both equally important! Ignore one or follow one rule at your peril!

Take an inexperienced student in a low powered draggy single and the priority has to go to pitch for speed as that will keep the pilot away from a stall situation.

but I repeat you have two throttles to tap into energy why use one????
Ignoring one has the potential for real danger.
Both principals are flawed!

Pace

Last edited by Pace; 8th May 2012 at 01:20.
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Old 8th May 2012, 00:59   #14 (permalink)
 
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Can't really argue with that other that in a light draggy trainer on an instrument approach using throttle for glideslope control maintains the airspeed, needs no movement on the yoke (always handy when on instruments) and requires no trim change. It works for me anyway, use whatever works for you.
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Old 8th May 2012, 06:06   #15 (permalink)
 
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Surely, for a given configuration, your airspeed is set by the trim wheel

All the engine does is control the rate of descent. This means that if you are happy just to go down, you don't need an engine.
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Old 8th May 2012, 06:18   #16 (permalink)
 
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This is an interesting debate... partly due to the number of different views/experiences....

If you are learning to fly and land a light aircraft, VFR and are still doing your PPL then you need to set aside all talk of ILS - it's too early for that.. you need to learn to fly the aeroplane first.

The principle that works for me...

Base leg and long final... get the aircraft properly set up, power/attitude/trim - you need to establish a stable approach at the right speed.

All the way down the approach, one hand on the throttle and scanning between the runway and the ASI you are trying to keep this initially stable approach going

As you descend, the runway perspective may start to flatten out... you are sinking! The aircraft needs more energy so apply a little more power and adjust attitude to maintain airspeed.... (as stated the two go together).

If the runway perspective starts to lengthen you are getting too high... the aircraft needs less energy.. reduce the power and adjust the attitude.

This needs to be practised until it is instinctive... the day will come when, at 300' on a gusty day, you might suddenly start to sink rapidly... at this point you need power!! So once you have this habit you are going to avoid hitting the caravans at Caernarfon or the factories/hedge at Hucknall etc etc...

As stated - if your career goes on to bigger beasts, jets and/or Instrument approaches there are new things to bring in but all of these will be better if you learn the basics now.

Agree with Geng about one instructor... I was the "son of many instructors" and it confused the life out of me (I guess putting a question on here could do the same - but I learned without t'interweb).... as you get experience the differing views/techniques are easier to cope with but at first... one set of techniques will do...

Good luck... happy flying... Mike
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Old 8th May 2012, 07:19   #17 (permalink)
 
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Quote:
Surely, for a given configuration, your airspeed is set by the trim wheel
Peter

What if you don't have one ?

Pace
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Old 8th May 2012, 07:36   #18 (permalink)
 
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I think this is one of the more fascinating PPRuNe discussions.

I'm in the Genghis/Pace camp in that the two controls are linked. In the early days you have to give a student something to hang his hat on and we break down the mechanism used into easy chunks. The reality is that you will have to use both controls when adjusting speed or rate of descent on approach.
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Old 8th May 2012, 08:25   #19 (permalink)
 
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But surely your speed is already stable by the time you intercept the glideslope? It's all hanging in there at 105 kts or whatever and just knocking 2-300 rpm off the donk will have you sitting on the glideslope at 105 kts as well, no elevator or trim input needed. Or maybe I have a unique body mass/fuel mass and it's just luck that it works for me? Genuine question.
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Old 8th May 2012, 08:59   #20 (permalink)
 
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Thing

That will be because you are now tapping into both energy sources!
You have a set power to give you a set airspeed.
You then reduce that power.
If you attempted to hold altitude on the reduced power the airspeed would reduce but you let the aircraft descend hence making up for that lost power by tapping into the inherent energy in the airframe.
That is a simplified view as we all know that AOA and drag come into it but the principal is that you have two energy sources available one from the powerplant the other from the airframe.
Take your scenario you have reduced power and allowed the aircraft to descend which maintains that airspeed.
All going well till you hit a rising or sinking pocket of air what happens then?

Pace
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