Throttle for speed, or stick for speed?

[Miserlou]

Airbrakes are very effective at controlling vertical speed and are operated in much the same way as the throttle; steeper descent when fully aft, shallow descent when fully forward. If one changes the pitch angle the speed will change.

May be easier for you DFC if we go back to effects of controls because I feel there's some fundamental errors in your understanding.
If you're flying straight and level and want to go up you have to add power.
If you want to fly faster you add power too but then you have to PUSH THE NOSE FORWARD so as not to climb.

I think you may be being confused by the fact that the pitch attitude for a given speed changes slightly due to the effects of the propwash over the wings and tailplane.

[slim_slag]

miserlou, not sure where to start with your post, I shall be charitable and assume you don't understand my use of 'trim it up' As I said, some of the stuff on this thread has confused the hell out of me.

classic, it's a 'top tip' to be used in a basic training spam-can. Basically the moral of the story is simply that if you get your power right early on you don't need to mess with pitch very much at all to fly a constant angle approach. Small corrections are easily effected by the trim wheel, if you end up needing large corrections then you have your power wrong so you need to change it. It's vitally important to keep ahead of the plane at all times and you will keep the needles in the doughnut. It may be herecy to some CAA examiners but it will get you on the ground very nicely, try it and see, if you don't like it don't use it.

Isn't getting the power right early on the basic premise behind how you teach a pre-solo student how to fly from abeam the numbers to the threshold? Ever heard it said 'power to 1800 abeam the numbers'? In other more interesting planes you might say 'power to idle' abeam the numbers. Both ways, once you have set power to a certain level you don't mess with it.

[Classic]

That's it, a 'top tip'. It's not a correct technique, it's not recommended and formally taught as a way of adjusting to maintain a glidepath. By flying any aircraft in this way you are effectively destabilising the approach. What are you doing with the control column when applying the trim? Just letting the nose drift up and down to achieve the glidepath? If you do that and have some sort of distraction for a time, the aircraft will continue to diverge from the glidepath at an increasing rate.

The reason I make these comments is that student or inexperienced pilots reading this thread may take what you say as sound advice and could find themselves with problems later. You should use the correct techniques in a spam can as much as any other aircraft f you wish to develop as a pilot, and bad habits like that will be spotted in a flash and jumped on further down a pilot's prospective career ( if they aren't already in a PPL flight check with an instructor).

The whole basis of basic flying training is to develop the idea that by setting an attitude, trimming to maintain it (NB NOT to change it) and setting the appropriate power setting, you will achieve the performance that you need.

[Say again s l o w l y]

Both ways, once you have set power to a certain level you don't mess with it.

Oooh I hate it when people use sweeping statements like that. Do you mean you've done something wrong if you've had to add or take away some power? Nonsense, you do what is required to keep the a/c where you want it.

There is no mythical, all encompassing way to fly aircraft, especially in the approach and landing phase. Are your actions always exactly the same on every approach? What happens when conditions are different?

"Top tips" are only used when somebody hasn't learnt the basics correctly in the first place. They mostly rank alongside Baldrick's cunning plans. Some do have merit and I myself don't always fly the way the book says, an example of differing techniques is cross wind landings, wing down, crabbed or a combination each has it's merit, but what do you find easier?

The only way I can understand what Slim is talking about is this, You are sliding down the glide slope and you start to sink below. I would at this point put a tiny nudge of back trim as I arrested the rate of descent, since it was obviously incorrect, but this is my personal way of doing it. I would expected an inexperienced student to re-establish on the glide using the primary flight controls, and then re-trim to help maintain.
Again this is semantics, but we need to keep techniques as simple as possible in the early stages, until a good understanding of what happens is built up, only then can we start to use 'short cuts.'

[slim_slag]

classic,

Note my use of the word 'heretic' in my first post. As I said, if you don't like it don't use it. With all due respect I think you have missed what I am saying.

SaS,

Not sure if you are agreeing with me or not, and I am also not sure whether you think you should use power or pitch to maintain a constant angle approach. I think what you have just said in your final post is correct, I think. Isn't the trim wheel connected to the same cable that the yoke is connected to?

This place would be so boring without a bit of controversy

[Say again s l o w l y]

In a way I'm agreeing, in that if you know the thing is trimmed wrong, you change it, but I wouldn't advocate just using the trim alone instead of the primary control.

I don't think that either power or pitch should be used in isolation, but a combination of the two since when one changes something in an aircraft it effects something else as well.

I think you'll find that the yoke/stick is not connected to the same cable as the trim. That does show a bit of a misunderstanding.
Most a/c have trim tabs that you are moving, so you are not directly moving the elevator with the trim wheel, but the tab.

[slim_slag]

SoS,

Yes, depends on the plane (and I was asking a question ). Again, if you don't like it, don't do it!

[MLS-12D]

Well gliders can't "fly" they can only glide.

See Miserlou's post, above.

I am not surprised to see that while people venture their own theories (which of course is their right), no one has suggested any criticisms of Langewiesche. As Miserlou said, "Stick and Rudder didn't get to be the classic it is by being factually incorrect."

On the same note, here is a quotation from Flying Magazine columnist Peter Garrison (another pilot who also knows more about practical aerodynamics and the theory of flight than the bunch of us together) in his 1980 book, Flying Airplanes: The First Hundred Hours (p.10):

Wolfgang Langewiesche's classic Stick and Rudder is the only masterpiece on the subject of learning to fly that I have seen. It is a thorough and correct introduction to the theory of flight for the practical aviator, and any pilot who takes his flying seriously ought to have read it carefully. It is dated, but being a really fine boook, it does not suffer much from age. Stick and Rudder seems to be free of errors and misconceptions; if it says one thing and your instructor says another, suspect your instructor, and keep quiet.

He continues, in a passage that may well serve as a denouement for this thread:

When I learned to fly, I didn't use any book at all, and it is quite possible to fly skillfully with a complete misunderstanding of some of the principles of flight. Most pilots do it all the time. Unless your jaw needs exercise, don't get into arguments with people about how things work. Read, listen, compare, and practice. You are certain to be exposed to misinformation or contradictions about the theory of flight; don't get worked up over it. It is the unavoidable consequence of nonscientists inhabiting a field that is, on the scientic level, quite complex.

[Say again s l o w l y]

Having not read either book I can't really comment on what is contained within them, but I am able to comment on some of the nonsense that gets put up on these boards.

Seems I must not be a 'serious' pilot then!! Again nonsense, but pretty much what I expect from some of the raging ego's that inhabit the private flying world.

Why would you keep quiet if you don't understand something that your instructor is trying to put across? Are you advocating that a book is a better teacher than the FI standing in front of you?

I have always got into discussions with people about how things work and this has always helped my understanding, are you suggesting that people should sit and just ponder and then come up with their own misconceptions? If a student didn't understand what I am trying to explain, I would be mortified if they didn't ask me to clarify.

What all this has to do with flying an ILS I don't know and also what has glider flying got to do with it aswell? I can't remember ever seeing a glider coming down the slope.

[slim_slag]

SoS,

You should go and read Stick and Rudder. There is one bit that makes me smile ( from memory it's something about the new fangled nose wheel planes coming out which will make it impossible to go off the side of the runway like you can with a taildragger) but it really is top notch.

Are you advocating that a book is a better teacher than the FI standing in front of you?

Read the book and think about that one again.

If you read the original post getting onto ILS discussions is not too far fetched. Also an ILS is excellent subject matter to discuss how pitch and power are used to follow a chosen path in the sky.

[Miserlou]

What I think MLS is saying is don't get into discussions about that which you have insufficient knowledge. Clearly there are some on here who should learn from that.

If you don't understand how a glider flies then you're at a disadvantage when understanding the finer points of powered flight. The aerodynamics are the same, the energy is derived from different sources.

It would be a sad state of affairs if the accident rate for gliders were the same as the accident rate for powered aircraft/engine failure accidents.

[Say again s l o w l y]

I'll try and find a copy of the book, but no matter how good it is, it can never be a substitute for a competent instructor. I have learnt more from talking and listening to people who are acknowledged experts than from reading any amount of books. Useful tools, but not the be all and end all.

Unfortunately there are many people on this board who seem to enjoy 'instructor bashing' at any opportunity. I have met a large number of these types in the flying world and to a man (yes, they have all been male) their attitude has panned out in the low standards of flying they ahve subsequently demonstrated.

Not all FI's are brilliant by a long shot, but given the time to do the job properly, you may be surprised at the levels of knowledge many have. Think about that next time you are telling someone that it is possible to complete a licence in less than 60 Hrs.

An ILS is NOT a good place to be discussing how to fly the aircraft competently. When you have reached that stage of training. I w ould assume that basic handling issues such as this would be taken care of, to allow you to concentrate on the job in hand i.e flying the ILS safely and keeping a mental picture of what's going on around you, NOT worrying about which lever you pull to make the a/c react how you want it.

Are gliders safer per hour of flying?

The aerodynamics of a glider and a powered aircraft are not the same. How can they be. They have totally different ways of operating.
The speeds are higher, the weight greater, airfoil sections different, plan forms utterly different, no issues such as thrust reaction or prop slipstream. You cannot argue that flying a glider is the same as flying a fixed wing or vice versa. Whilst the basic aerodynamic controls are roughly the same, how they effect the system is different. If you have lazy feet in a glider, ther is a much more pronounced effect than in a stubby little pwered a/c.

[slim_slag]

Miserlou,

In 2000 (last figures I can be bothered to find) in the US:

SEPS: 7.61 accidents and 1.27 fatal accidents per 100,000 hours flown

Gliders: 20.36 accidents and 3.18 fatal accidents per 100,000 hours flown

Now what was that you were saying???

SoS,

Chill

[MLS-12D]

Seems I must not be a 'serious' pilot then!! Again nonsense, but pretty much what I expect from some of the raging ego's that inhabit the private flying world.

Oh for crying out loud. Please re-read my post.

I didn't say that anyone who hasn't read Stick and Rudder is not a serious pilot. I merely quoted from a book that suggested that any pilot who takes his flying seriously should have read it.

If the book has previously escaped your attention, fine; there are plenty of great books out there that I don't know about. Now that it has been brought to your attention, I have no reason to believe that you will not attempt to track it down and see whether it is as good as the rest of us say it is. And if, after having read it, you have some criticisms, I will be happy to hear them, and promise to do so with an open mind.

Why would you keep quiet if you don't understand something that your instructor is trying to put across? Are you advocating that a book is a better teacher than the FI standing in front of you?

Point one: again, I was quoting a book. If you don't like what was said, just don't buy the book. Giving me a hard time about its contents is pointless and unnecessary.

Point two: yes, often the author of a flying book is much more experienced and knowledgeable than a run-of-the-mill flight instructor (especially those who are only 'building time' en route to an airline career). Is this really controversial?

Point three: While I can't read Peter Garrison's mind (refer to point one, supra), I speculate that he is suggesting that the student not engage in a discussion with his instructor because that might put the latter on the defensive and might well lead to hard feelings. E.g., just look at how quick you were to attack me!

Unfortunately there are many people on this board who seem to enjoy 'instructor bashing' at any opportunity.

Here is my take on instructors: some are good; some are bad;a few are great; and a few are dreadful. By the way, I am one myself.

You cannot argue that flying a glider is the same as flying a fixed wing or vice versa.

Actually I can, and will, argue that point. As anyone who has the slightest acquaintance with gliders knows, they are - surprise! - fixed wing aircraft.

[Miserlou]

Your statistics are as the lamp-post to a drunk man...more for support than illumination!

Now let's see the statistics for the UK, stall/spin(including following engine failure) per flight. I think you'll find a different result. These factors are only mentioned in the appendices. Running out of fuel or suffering an engine failure should not lead to a fatal accident.

What I was saying is also difficult to see in the statistics because stall/spin accidents which occur after an engine failure come under 'engine failure' which fails to show the true cause of an accident.

A 747 at idle thrust is nothing more than an overgrown glider. Whilst the systems may be vastly more complicated, that's all it is. Do they suddenly get new rules to fly by when they have all engine flame-outs? I think not!
Thanks for the laugh.

[DFC]

Miserlou,

[I]Airbrakes are very effective at controlling vertical speed [/B].

I am going to be very bold and say - No they are not!!!!!!

Airbrakes are very good at increasing drag and drag opposes thrust and at a set thrust an increase in drag will cause a reducton in airspeed.

The rate of descent may change as a result of the reduction in speed provided by the speed brake or if the pilot choses change the descent gradient i.e. hit the ground sooner which has a secondary effect of maintaining the speed.

Theoretical aircraft with locked controlls flying straight and level at 150Kt........the pilot extends the airbrakes slightly...........the aircraft slows down............lift reduces and the aircraft descends.....the path of the aircraft through space has changed. If the controls are unlocked and the pilot uses the control stick to return the direction of the movement vector back to where is was - the overall result will be the aircraft travelling along the original profile at a lower speed but a higher angle of attack (to counteract the loss of lift)

Thus the pilot has altered the speed with the airbrakes and then used the stick to restore the flight vector through space.


This argument is like the one where pilots say ailerons roll the aircraft and others say ailerons cause yaw..........both are correct but think about how we actually use the ailerons and what we considder primary effects and secondary effect. The last time I checked, the change in airspeed was a secondary effect of moving the elevator the primary effect is to pitch the nose up or down.

Most aircraft have a Power/Drag couple. On some aircraft, it is possible to control pitch with changes in power - would miserlou when flying that type use stick for speed and power to alter pitch attitude?..........or would he say that the stick is for altering attitude the change in speed is simply a secondary effect and the power is for altering thrust not for changing the attitude which is just a secondary effect!

Regards,

DFC

[Miserlou]

Thank you, DFC, very bold of you.

Airbrakes, the common name for spoilers, so-called because they spoil the airflow and in so doing decrease the lift. In opening into the airflow they also create drag which causes the speed to begin to decay reducing the airflow over the tail, in turn reducing the tail down force. This creates a nose down pitch change whereby the speed will increase again to restore the airflow over the tail until the stable situation is restored (typically after a couple of oscillations).

The new situation leaves the aircraft in a steeper descent at the same speed with a slightly different pitch attitude due to the change in configuration.
How you lose energy is up to you but if the pilot is now flying level at a lower speed then he will have a higher nose attitude.

You've really answered your own question where you mention the higher angle of attack. Speed is only a fallacious way of expressing angle of attack (for which, see Stick and Rudder). I see no case to answer; you can't change the principles of flight.

The pitch/power couple is part of the stability of the aircraft so that, as an example, if the engine were to fail the nose tends to fall. Then the speed doesn't have to decay so far before the stable, trimmed situation is restored.

Let's not go into exceptions like the Lake. It still flies faster when you put the nose down.

If moving the nose up and down is the primary, and controlling the speed is the secondary, then the flightpath must be the tertiary effect of the control. The discussion here is that the elevator controls the altitude/vertical speed before the attitude/speed.

Thanks for backing me up on that!

[ShyTorque]

"Airbrakes, the common name for spoilers, so-called because they spoil the airflow and in so doing decrease the lift."

Different things, where I was taught.

Spoilers popped up out of the wing and spoiled the lift. Some gliders have them.

Airbrakes popped open, not out of the wing, and created drag.
Like on the Buccaneer, the Hawk or the BAE 146, for example.

[Final 3 Greens]

I've been away on business for a few days and am amazed that this thread has run to 6 pages now, with such strong opinions from different perspectives.

Two things are clear:

1 - the laws of physics create a complex system within which the flight regime operates

2 - we create meta models to help us think about the complex system and in this specific instance to create metaphors that are easy for students to learn and which deal with the complexity by chunking the whole into easy to digest portions - e.g. How do you eat an elephant. Some learn one way, others another and a few learn multiple models

The impact of such powerful learning can been seen in the points and counter points in this thread.

As someone who designs learning programmes (in another equally complex field), I always take great care when creating powerful metaphors, since the subsequent "unlearning" required to move on to a different level of sophistication can be challenging.

People tend to scan the environment for information to support their beliefs and discard new learning because it does not fit the meta model indelibly burned into their unconscious mind during the training process.

Perhaps the real learning point from this thread is for instructors - when you are teaching one method or the other, an explanation of the context would be helpful, so that PPLs moving on to IRs or jet ops suffer less cognitive dissonance (confusion) when confronted with apaprently contradictory approaches.

In fact, I thought that Chimbu Chuckles summarised it pretty elegantly.

[Miserlou]

Shytorque,
The spoilers on a glider in the UK are called airbrakes, those which extend above and below the wing, and are used primarily to control the rate of descent on the final approach. They can also be used when descending 'on tow' so as not to overtake the tug.

Not really my fault that they are incorrectly named.

DFC,
I'd most certainly agree that the most important lessons may be for the instructor. A fact which wasn't missed by the CAA in one of the accident summaries noting LOC/VMC accidents due to failures in basic handling, to which I also refered earlier, as a possible symptom of poor instruction. I'm not instructor bashing (unless they think that the throttle controls the speed), just drawing the same conclusion.

The most simple system to break the principles of flight down into, or build up from, must be the glider, hence the references here.
We must at all costs avoid cognitive dissonance!