primary effect of elevator

[plucka]

I am after some instructers ideas on this matter.

When I was taught to fly the primary effect of the elevator was believed to be pitch and as far as I know that is still what is taught. However after alot more experince I now disagree, I believe the primary effect of the elevator is angle of attack. Although very similar when in cruise quite different when stalled or very near the stall or critical angle of attack.

As we know stalling is when the wing reahes the critical angle of attack and stops producing lift, REGARDLESS OF SPEED. Did you also now that for a constant weight and atmospheric conditions being a constant, the aircraft will stall with the elevator at the same position regardless of speed. Hence if we do a staight stall with a high nose attidute we stall with the control column 2" from our beer guts lets say, therefore regardless of speed the aeroplane will stall with the control column 2" from our guts every time with weight as a constant.

This said not alot of us spend that much time so close to the stall, hence when we pull or push, the aeroplane pitches but that is because the angle of attack changed.

Do you think this should be taught because alot of new students I talk to do not seem to have a full understanding of stalling or angle of attack.

Your thoughts would be appreciated.

[FlyingForFun]

Hmm...... I think I agree, in theory.

In practice, though, we teach primary effects of controls in exercise 4a (if not exercise 3). At this stage, the student will have no understanding of AoA. What they will understand is attitude, so relating elevators to attitude seems to make sense, even if it's not true for every single phase of flight. Also, remember the aim of exercise 4a is to use the controls to select the datum attitude - so it's necessary to relate elevator to attitude to achieve the aim.

The student will get the complete picture as they go through the course. In exercise 4b they will discover that there are other things which can affect the pitch of the aircraft (power and flaps). In exercise 10b they will discover the stall, where, as you say, elevator can no longer be used to cause a direct pitch change, and we need to think of AoA. By that time, the student will have gained enough knowledge to understand what we're trying to teach him.

alot of new students I talk to do not seem to have a full understanding of stalling or angle of attackHow "new" do you mean? As I said, I wouldn't expect a student to understand these things properly until they've completed exercise 10b. In fact, there might even be a good argument that a student doesn't understand them properly until he's done a few hours of aeros.

FFF
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[plucka]

Thank You for your reply FFF, and I agree AofA is fairly indepth and to a new student too complicated to deal with in the early stages. I must admit I learnt to fly in NZ under a different syllabus as these numbers you quote mean nothing to me, but I get the idea.
When I said new students I mean near to PPL standard. I constantly hear them talking about stalling as a speed! This may not be a big issue where you are located and possibly be a smaller problem than I thought.
However I think a couple of lessons of aerobatics is a great idea at some stage in their training. This is where things like 'stick position, stall position' and how far out of balance we can actually fly, can be demonstrated.

[Oktas8]

Hi Plucka,

Clearly FFF has given a textbook answer - it is "the" answer, if there is such a thing! The purpose of an elevator is to control pitch, but the effect is usually to control angle of attack.

Did you also know that for a constant weight and atmospheric conditions being a constant, the aircraft will stall with the elevator at the same position regardless of speed.

For a little more information, your assertion quoted above is not strictly true. Stalling stick position will vary with configuration, rate of change of 'g', power (in some aircraft), and with CG position, to name only the main variables. For this reason the concept is not used in basic training, although it is an interesting discussion point in an aerobatics course.

While on the topic of aerobatics, did you know that with the right combination of speed and power you can use the elevator to maintain a pitch rate without changing the angle of attack very much? The first half of a loop would be a good example. So actually it is more generally true to say that elevator controls pitch, than to say that it controls angle of attack.

Well done for raising these points - you obviously already understand more than many!

O8

[FlyingForFun]

Agree with O8 about how stick position doesn't necessarily correspond to the stall - there was a discusion about this very recently, so rather than encourage thread creep by discussing it, I'll refer you to here (http://www.pprune.org/forums/showthread.php?t=219492).

I learnt to fly in NZ under a different syllabus as these numbers you quote mean nothing to meSorry - shouldn't have assumed you'd know our syllabus. Ex 3 is a trial lesson. 4a is Effects of Controls part 1 (effects of the primary flight controls) and 4b is Effects of Controls part 2 (effects of the secondary flight controls). 10b is stalling. I think that covers all the numbers I used.

FFF
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[homeguard]

Lets be very careful here. We may well be talking semantics and not aerodynamics.
The elevators control the aircraft in pitch around a centre of gravity. The angle of attack is the relationship of the wing cord with the path of fight (RAF). The elevator does not control the path of flight but is an element of the sum that gives to performance. By changing and CONTROLLING the pitch of the aeroplane around its centre of gravity using the elevator you will of course change/achieve an angle of attack to a given RAF but so do other things as already mentioned.

[NeedMoreHFMnemonics]

When the student first learns about the elevator, all they need to know is...
back pressure = pitch up = climbing attitude, slowing airspeed and reducing rpm.
forward pressure = pitch down = descending attitude, increasing airspeed and increasing rpm.
Everyones mind is like a wine glass, fill it up with too much crap and some good wine spills over the sides, lost!

[homeguard]

Pitch up does NOT = climbing attitude.

Pitch down does NOT = descending attitude.

[Horatio Leafblower]

I think NM HFM is on the right track - Instructors have a much deeper knowledge of the subject than a student will grasp at the early stages.

Keep the explanation usable, simple, and safe - when the sh1t hits the fan they will do the right thing.

Insight only comes with experience and exposure to a wide range of situations, and the full picture will only confuse 'em. I have one particular former student who delights in hanging around the Aero Club button-holing my current new-starts and telling them in eye-watering detail why the stuff I am teaching is 'wrong'. :ugh: