Stick & Rudder

[Tomo]

So once again, talking primary effects, stick for speed, throttle for flight path!

:thumb_up: Throttle/Power/thrust ''will'' control speed ''also", as we all know...

 

 

[Guest Sharp End]

But if we have a functioning engine, we can reduce the needed descent rate by artificially, if you like, adding power to the system by adjusting the throttle ....So once again, talking primary effects, stick for speed, throttle for flight path! ....

I've been observing this thread and thus far have refrained from comment. However it's now time, so here's my input.

 

Rocketdriver, please re-read the quote above.

 

My response?

 

Equally, if we have a functioning elevator, you can reduce the needed descent rate by adding power to maintain speed, while pulling back on the stick to achieve your desired rate of descent, then trim. Thus stick for flight path and power for speed. In my opinion, the argument in this thread is not helping students. BOTH methods work in GA aircraft - however, as I've pointed out in a previous post in the landing technique thread, if you use the stick for speed, throttle for flightpath technique in some aircraft you will get yourself into trouble very quickly.

 

 

[Guest Crezzi]

if you use the stick for speed, throttle for flightpath technique in some aircraft you will get yourself into trouble very quickly.

Just out of interest - which types ?

 

And are there any aircraft where the opposite is the case ?

 

Cheers

 

John

 

 

[Guest Sharp End]

Just out of interest - which types ?And are there any aircraft where the opposite is the case ?

 

Cheers

 

John

Hi John,

 

See my post here:

 

http://www.recreationalflying.com/forum/question-week/68009-landing-methods-4.html

 

Other types are F104 - again used boundary layer control on its flaps via "blow" ducts from the compressor, and the Hunting H126 - same reason.

 

Aircraft with the opposite problem? Hmmm, all gliders I guess. I learnt to fly a glider (just circuits from cable winch launches to solo standard) when I was 15 and the stick for speed system was drummed into my head - so yes - although the airbrakes could be construed as an "anti-throttle" just to add to the confusion. i_dunno

 

 

[Tomo]

Then there is the question - is it practical, and comfortable? Re, using stick for speed, throttle for flight path.

 

Small aircraft don't tend to worry much, start moving into bigger aircraft, (ie longer) and you'll be sea sawing all around the sky.

 

Question has been moved to another thread.

 

 

[GraemeK]

In my opinion, the argument in this thread is not helping students. BOTH methods work in GA aircraft

Sharp - 100% - and both methods produce the same result as I've pointed out before. In descent, both methods result in you maintaining the aim point constant in the windshield. If the aim point moves down, you're overshooting - either reduce power to increase descent rate, then forward stick to maintain speed - or forward stick to adjust glidepath, reduce power to control speed.

 

Six of one, half a dozen of the other.

 

in the circuit and decide to slow things down a bit. reduce power to reduce speed.trying to get somewhere in a hurry. Increasing power = more speed.

 

bumpy conditions and need to reduce speed to turbulence penetration speed. reduce power which reduces airspeed.

 

cruise descent and want to maintain your cruise speed. Reducing power = less speed.

 

etc

At the risk of promoting disharmony in the Mazda household, I would question this - in all these cases we respond with both throttle and stick. For example, in turbulence, yes we reduce power but we also increase backpressure and thus the combined actions reduce airspeed while maintaining altitude. If we simply reduce power we'll enter a descent.

 

Question for someone who has access to a plane (right now I don't, since I left my FAA licence at home ). Set up straight and level, trimmed for cruise speed. Check trim by hands off stick. Then throttle to idle. What happens immediately to ASI and altimeter? What happens then to ASI and altimeter? Just for good measure, what happens in the same situation if you lock your arm to maintain the same stick position?

 

Interested in feedback as to what happens practically. If I can wangle it, I'll try to get our A380 driver to check out how his machine behaves on the way back home.

 

 

[Tomo]

Graeme, that is a good point, but: (where would you be without that word eh?)

 

When we say, use power for speed, stick for height or flight path if you like. That says it all, really; So you reduce power, nose go's down (due to drag and aerodynamics), then you use a little back stick to maintain height/flight path etc... And the same when adding power, nose rises (due to thrust line and aerodynamics) so you push stick forwards to maintain height/flight path etc... Because if it didn't, we wouldn't need an elevator at all.

 

At take off, do you add power first or forward stick to get speed?

 

Hope that makes sense...

 

 

[GraemeK]

Tomo - my point entirely - we never use either throttle or stick in isolation, we're constantly adjusting both.

 

But my challenge still stands - what happens in a perfectly trimmed aircraft in cruise if you throttle back to idle and don't touch anything else? I reckon the altimeter starts to unwind and the ASI stays at the trimmed airspeed (plus/minus a bit).

 

Happy to be proved wrong.

 

I'll let you know if our A380 driver is up to the challenge :DevilDog:

 

 

[GraemeK]

At take off, do you add power first or forward stick to get speed?

At take off, I'll take all the thrust I can get thanks. :thumb_up:

 

After takeoff, I might well exert a bit of forward pressure if necessary to achieve max rate of climb speed after I come out of ground effect .....

 

 

[Tomo]

But my challenge still stands - what happens in a perfectly trimmed aircraft in cruise if you throttle back to idle and don't touch anything else? I reckon the altimeter starts to unwind and the ASI stays at the trimmed airspeed (plus/minus a bit).

I'll definitely try that in the Jab next time I'm in it, though in the Drifter, it actually noses up a bit, and the speed deteriorates faster than you think. It will then descend in a mushing state.

 

I guess that is the difference between High Performance and Low Performance high drag machines.

 

But seriously, in an approaching situation like what we are talking about, the aircraft is already descending, how you got it to that point I don't know, your aiming point is third line in, you are established in a glide with a slight power descent, everything is looking good. You suddenly hit massive sink, and your airspeed is going down, the ground is very close, would you put the stick forward if you had power? If you didn't, there is no question other than yes. Never stall it higher than 6 inches or less above the ground. Fly it through the fence if you have to.

 

I don't know, we really are going in circles, but what ever situation you're in, do what you have to. I do a reasonable amount of low level flying, and you DON'T use stick for speed, stick is what make you either hit the ground or miss it, the up down thingo...

 

When gliding, I use stick for the whole thing, thermalling at the stall, S/L 70kts and still climbing on a thermally day.

 

Learn your aircrafts abilities/short falls an make use/be aware of them.

 

 

[Guest Sharp End]

But my challenge still stands - what happens in a perfectly trimmed aircraft in cruise if you throttle back to idle and don't touch anything else? I reckon the altimeter starts to unwind and the ASI stays at the trimmed airspeed (plus/minus a bit).

Depends on aircraft type, airspeed and thrustline. Generally true of stable GA aircraft, definitely not true of unstable "electric" jets ie F16. Interestingly a stable non-electric jet had a "different" characteristic which was demonstrated on the Lightning Training Flight. From an entry speed above 500kts trimmed out S&L if you selected idle/idle, the 'Ning would climb as the C of P moved forward as she started to slow down, then, as she got into the wrong side of the drag curve below 230kts would sink like a brick with about 15 degrees nose up and 18 alpha (AOA).

 

I'll try the "challenge" in the Airtourer when we next get to fly her but I'm prepared to bet she'll behave as Graeme predicts.

 

A380? Dunno! Stable "electric" jet. Probably plough on for a couple of cups of coffee before anyone noticed... i_dunno

 

anyone?

 

 

[Methusala]

Tomo, If your Drifter noses up a little when you reduce power it is possibly due to the thrust line being slightly nose down. Then, when you reduce power there will be a tendency for the nose to rise as the wing adjusts to the reduction in thrust. This could be a factor in the Drifter's reputation for very benign landing characteristics, meaning that as you flare and pull power back to idle the nose will rise gently. I haven't flown a Drifter, just speculating. Don:wave:

 

 

[Tomo]

Yes, that could be it Don, most likely anyway.

 

Destiny, that's interesting, thanks for that. Certainly shows we need to use the elevator to keep anything in control.

 

BTW, I'm not into proving anything if that's what some of you think, because we all know that both ways work, just a matter of working out which one to use for each occasion for the most practical results.

 

 

[Mazda]

Here we go again.

 

Firstly, Rocket. You've quoted the lift equation, well done. The problem is we are not talking about lift alone, we are also talking about thrust. You might remember there are 4 forces acting on an aircraft (plus the tail balancing force). If you take away the issue of thrust to overcome the drag, you are talking about gliding - hence of course you have to use attitude as there is no thrust to overcome the drag.

 

Graeme. Which way will it go? Depends on the thrust/drag configuration of the aircraft, the centre of pressure (eg swept wings). So for those giving examples, that may be true for that type, but don't think that is the case for all. What WILL happen though is if you maintain the attitude, the aircraft will slow down, and of course at some stage you will have to lower the nose to keep flying speed to avoid a stall, because you no longer have thrust to overcome the drag. For many RA/GA aircraft, the thrust/drag couple is designed to do this automatically (idiot proof?!) so the nose is likely to drop to maintain speed. This is a design feature, not an aerodynamic principle.

 

Now, for the students reading this.

 

I really, really don't want to get into complex aerodynamic debates here because from what I've seen, there are some basic misunderstandings of aerodyamic principles.

 

My advice is to take advice from the real experts - those who have studied the subject in detail - experienced airline, military (such as Mr Kruse - one of the most successful GA instructors), competition aerobatic pilots, or suitably qualified professionals. Please don't take advice from those who have been shown one way decades ago and believe anything else is WRONG.

 

When I started flying I was taught to use attitude for speed, and I did so for many years, until an aerobatic instructor said "let's try another way." Like some people here, I thought the guy was an idiot and was clearly WRONG because my other instructors taught me differently - I'd managed OK so far. Until I actually took the plunge and did what he suggested. It worked, and worked far better than the old way.

 

Yes, of course you can get by using attitude for speed, it works - up to a point. If you are only ever going to fly as you are doing now, stick with what you know if you are not interested in trying an alternative. But when you start flying something of higher performance (or if you start flying instrument approaches) that technique fails.

 

My issue for the students is why not start out with a method that you can use in everything from Jabirus to A380s to fighters?

 

For those who are using attitude to control speed on a powered approach and say anything else is WRONG, have you actually tried both techniques?

 

 

[GraemeK]

Also, suddenly finding yourself low or short with a big chunk of sink on final can not be saved by stick for fear of stall but can be with power.

It's all about energy management - and I'd prefer that when I get that sinking feeling I'd instinctively respond with throttle rather than stick - apart from that, both methods produce the same outcome and neither is right or wrong. And in the real world, on approach for instance, we make frequent small simultaneous changes to both, we would hardly notice which came first anyway, it pretty much becomes instinctive.

 

Nevertheless - in terms of aerodynamics, the natural aerodynamic behaviour is that stick controls speed (more correctly, AoA - but in most GA aircraft speed is a good proxy for AoA) - after all that is what decalage is all about. As others have pointed out, that normal aerodynamic effect is modified in some aircraft by effects such as the thrust/drag couple.

 

And, as Destiny pointed put, pulling back on throttle actually increased airspeed first, then returned close to trimmed speed - but the aircraft started to descend rapidly. As predicted. Then increasing throttle without touching anything else resulted in a climb at marginally below trimmed speed.

 

And as Mazda rightly points out - don't get your advice off a web site. Always talk to your instructor and take their advice. :thumb_up:

 

 

[GraemeK]

Just a thought on why this debate sometimes gets heated ...

 

Maybe we are talking about two different things. The first is the aerodynamic theory - the stick moves the elevator, which changes the angle of attack and hence speed (all other things being equal, like thrust/drag couple). Throttle controls power, which affects energy - add throttle when trimmed and the extra energy has to be reflected as potential energy, ie altitude (again, all other things being equal). That's the law!

 

The second is how you actually fly the plane, which is a different thing - and depends on a whole lot of other things, including type and personal preferences. There are many ways of achieving the same thing in practice, and none is particularly right or wrong, it depends. An example would be the approach in a typical GA aircraft - I actually think it would be pretty hard to work out which method the pilot was using by watching him/her - the adjustments would be smooth and continuous and in both cases the aiming point would remain constant in the windshield. Which is just as well I guess :patch:

 

Sharp End - you might be able to help me on one point. I'm sure someone (probably an instructor) telling me one reason you have to use stick for flightpath in the jets is that the engine takes a finite time to spool up and hence is too unresponsive to make quick changes to path.

 

 

[Methusala]

Graeme K, Thankyou for throwing in that lovely term decalage. Words make life interesting. Learning is also a satisfying pursuit and I have gained a lot from my involvement in this discussion. I have been encouraged by the high level of committment and thought displayed by you blokes and sheilas. Justifies Ian's and many others expense of time and resources to what is, I think a great site. We must all be open to new ideas proposed but not be shackled by reputations of those who put them forward. An open mind but very sceptical is my way of thinking. Thankyou all, Don

 

 

[Guest Sharp End]

Sharp End - you might be able to help me on one point. I'm sure someone (probably an instructor) telling me one reason you have to use stick for flightpath in the jets is that the engine takes a finite time to spool up and hence is too unresponsive to make quick changes to path.

Hi Graeme,

 

Partially true and one reason the RAF/RAAF way is PAT... Power-Attitude-Trim. You recognise a change in flightpath is required, adjust the power and change the attitude. Once the engine spools up or down towards the required power setting, re-adjust it to exactly the required amount and then trim. Gen three turbofan engines such as the Adour and RB199 spool up reasonably quickly and spool down very quickly compared to the older generation turbojet Avons and even older centrifugal flow Derwents etc. The most noticeable difference in a jet (apart from the sheer grunt of the things) when compared to a piston is flying formation... fore and aft positioning is done by throttle and you have to almost second guess the leader unless he/she is REALLY smooth with throttle inputs.

 

I'm a little past my use-by-date to comment on gen four engines but can tell you that the Pegasus as fitted to the Harrier reacts almost instantaneously to throttle input and probably has engine acceleration rates better than modern EFI piston engines. The down side of the Pegasus' startling performance is TBOs of bugger all hours... 250 from memory although it may be 500, not sure, never flown a Harrier - my legs were too long!

 

S-E

 

 

[Guest Sharp End]

Hmmmmmm ... what is it about Don's .... I know a few :ilmostro:

Par-Don?

 

I'm a bit deaf... too many jet engines!

 

 

[flying dog]

I read a bit of this - it is going on way too long for my likes.

 

Mr Bob Hoover would be THE BEST person to ask about power management with what he does in his plane.

 

Oh how I would love to be able to get in touch with him and ask him to please post his thoughts here.

 

 

[Guest Sharp End]

Hey Mark,Good one you poor deaf bastard. Have you and the lovely Ms M been parking up in the big block lately :polite:. How are all 3 of you , (you two and the Big Block I mean)?

LOL

 

David

Sorry mate, didn't hear you at first!

 

All good here with the three of us, hoping for a decent weekend weather-wise to give the Big Block a work out! Cheers...

 

 

[Guest Sharp End]

hi fdBob Hoover does a great demonstration of "energy management".......when he starts his routine he doen't have any power!!!

 

check on youtube....there are a number of videos of the great man

Check it out!