Keeping the ball in the middle

[TrueNorth]

Hello all,

Wanted to get some second opinions on this:

When flying around in a 150 or 172, I make an effort to keep the ball in the middle (co-ordinated flight etc etc).

On long-distnce flights, this can result in a fair amount of discomfort, due to the constant exertion of pressure.

When I mentioned this to my instructor, he said `Don`t worry about it. Let the plane fly how it likes. If necessary, the machanics can alter the rudder trim to make it fly "straight", but don`t bother keep ing the ball there - you`re only adding drag`.

So, should I keep applying constant left or right rudder to keep the ball in the middle, or let it all hang out?

Any thoughts?

[Noggin]

Firstly the fixed trim tab should be adjusted so that you don't have to exert any pressure at normal cruise speed.

Secondly change your instructor

You might like to get him to explain about drag when the aircraft is out of balance.

[TrueNorth]

Hi Noggin,

That`s what I thought - if the plane is out of balance the drag will be worse!

Sorry to harp on...but I want to get this straight.

Say you were flying a heading of 360. There is a strong, steady wind from 090. Presumably, your tail will be pushed to the `left` as it offers more resistance to the wind. In that case, seeing as you can`t alter the trim tab in flight (on the planes I fly), you would have to suffer the results of continued use of the left foot. Is that correct?

cheers

[John Farley]

True North

No the wind will not blow your tail to the left.

The wind merely makes the mass of air you are flying in move over the ground (in the case you gave ) towards the west, so you will head 360 and track over the ground a bit to the left of north. The actual angle depending on your speed and the windspeed.

Mind you if your post was a windup I guess you win on all counts

JF

[TrueNorth]

Certainly wasn`t a wind-up.

I was just trying to determine if there could have been a reason other than poor rudder trim on the particular aircraft I was flying that caused me to have such a painful left foot through applying constant left rudder!

Now I feel stupid, however...it must have been a fairly inane question to cause people to think it was a wind up!

I thought it was fundamental that you always tried to keep the aircraft properly balanced - my instrucotr`s reaction to this (see original post) had me flummoxed...

[Noggin]

If you have a painfull left foot it sounds as though you have an excessive amount of fixed trim tab applied. A good reason why you should not push it on the pre-flight, or back it into the hangar door.

With many light aircraft the turn and slip may not be mounted horizontally resulting in the ball being slightly off centre.

If the aircraft is out of balance it is effectively going slightly sideways so which causes more drag, the rudder or the fuselage?

[John Farley]

TrueNorth

No need to feel stupid at all. We all have to learn. Are you happy now about the effect of a steady wind on the way your aeroplane flies through the AIR ?(ie it has NO effect on the trim) and that a steady wind only affects the way you travel over the ground

JF

[Oleo]

Yes I agree - get a new instructor, your current one has no clue what they are waffling on about... more drag indeed!

Yes, your plane's fixed trim tab needs adjusting. Yes your aeroplane has no idea that it is being pushed by a wind from 090 deg. It flies on happily as Mr Farley said with the mass of air; the wind does not push the just the tail, it pushes the whole of the aeroplane and dispaces it sideways while still facing 360 deg. And you still need the ball in the middle.

As I always like to tell my students: "the aeroplane doesn't know the wind is blowing!"

It will accelerate until thrust equals drag, whether this means standing still, going backwards or sideways. But it should always be flown with the ball in the middle in normal flight for minimum drag and hence maximum range.

With the ball in the middle you present a minimum of side surface to the wind and hence drag is minimised. We practice this using a piece a drift string taped to the nose of a twin aircraft while practicing one engine out drills (well I haven't practiced it personally But I have read about it...)

Hummmph!! ;)

[A and C]

True north take the advice in noggins first post and read all the posts below .....both actions will improve your flying.

And if you have eny doubts about aviation ask the question ,as this forum has the most instructor attention it seems like the best place.

[GT]

For what it's worth, I think Noggin's first post is about spot on.

[Manwell]

Truenorth,

May I also suggest that the sure way to find out if your aircraft is in "balance" is by levelling the wings and observing to see if there is any yaw, ie change of heading.
If the aircraft is yawing at all with the wings level it is unbalanced. Note that this may be very subtle and gradual.
If the balance indicator doesn't agree, it's the one that's at fault. Probably not mounted in the panel correctly.

Another thing to look for is the airspeed with the ball in the centre, and the speed with the wings level with no yaw. The higher airspeed (in smooth air,with power constant) will indicate least drag.

This method takes a lot longer than just looking at the ball, but if you get used to it you don't need to scan to the ball at all while looking out. It also develops an insight into balance that you can't get from watching the balance ball.

By the way, what is it that is in balance during balanced flight? I'd be interested to see what you ladies and gents think.

Regards to all..

[TrueNorth]

Many thanks, all!

Your replies have been very helpful. It can be a bit disconcerting when an instructor says the opposite to what you have learned from the very beginning...

Once again, thanks for clearing this up for me.

JF - thanks for the kind words. I`m happy with the effect of wind on a plane now.

This forum is great for student pilots like myself. Hope you don`t mind students invading the staff room...Stand by for further requests for information!

[Qhunter]

Cessna's have right hand tractor props and shouldn't need any left rudder except during a medium to low power descent.

Get a new instructor and get the plane seen to :)




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...is it Friday yet ?

[Tinstaafl]

It's easy to fly in-balance in straight flight.

As indicated previously, as long as the wings are maintained level then use whatever rudder is necessary to prevent the heading from changing ie prevent yaw.

Apart from asymmetric considerations eg a power/speed combination that it has not been trimmed for, or banana shaped aircraft then the a/c must be in balance. If continuous rudder pressure is needed then the rudder trim needs adjusting.

Best way I've found is to use a speck on the windscreen directly in front of you, and align it with some object on the horizon (further away is better than closer). Use rudder to prevent your chosen speck from yawing to the left or right of the aim point. Remember this is while keeping the wings level.

If you need to turn the a/c to align the speck then a coordinated turn should be done.

Even a fairly well coordinated turn can be done just by looking outside the a/c.

Again, choose a speck, but ensure it is one that appears to be postioned on the horizon.

If you're using the correct amount of rudder then the a/c will appear to roll around the speck against the Hz before any heading change happens.

If you're using to much rudder during the roll to the desired angle of bank, the speck will appear to move below the Hz.

If too little rudder the speck will appear to move above the horizon & in the 'opposite' direction of the roll/turn eg roll right with insufficient rudder the speck will move to the left. This is due adverse yaw - the reason rudder was required in the first place. Because the roll is causing an angle of bank, the yawing motion won't be parallel to the Hz, thus giving the speck the appearance of moving above the Hz.

P*ss easy to demonstrate in a Cessna but not so easy in a Warrior or anything that has an aileron/rudder interconnect.

Hope this helps. I suspect your instructor is being a bit slack with his/her teaching.

[FNG]

Tinstafl explains it in much the same way my old instructor would. May I venture a suggestion for True North, speaking as a non instructor (low hours PPL). At some point in your flying, if funds and logistics permit, try flying dual in an aircraft which normally requires more rudder inputs than a C150/152. Some nosewheel aircraft (eg Firefly, Pup, Robin) and probably most tail draggers would qualify, and the one I have experienced which hammers home the concept is the Tiger Moth. Persuade someone to buy you one of those gift vouchers for a Tigger trial as a Chrissie present. 30 mins dual with an experienced Tiger QFI should illustrate the point fairly neatly. Tell him you are not concerned (this time, at least) with learning Tiger checks, departures or landings, and concentrate instead on S&L and a few balanced turns. Then go back to the Cessna and see what happens.

[TrueNorth]

FNG,

A good idea. I have about an hour on taildraggers - I think it`s made me a lot more "rudder conscious" than I otherwise would have been.

From my experience, it is an area that somehow gets a little bit neglected (due, I suppose, to the type of aircraft on which most student pilots train).

While we`re on the subject of balanced flight, I was practising some timed turns (partial panel) yesterday, and it drove home to me the importance of flying a properly co-ordinated turn. I get a strange satisfaction from seeing the ball stay in the middle as I go through the turn and come out on the hoped for heading after x seconds!

Thanks again everyone for all the helpful replies

TN

[fallen eagle]

Aged instructor to student learning on Tiger.Explanation on use of rudder.If we push on the left pedal we get a draft on our right cheek, if we push on the right pedal we get a draft on our left cheek.We dont want any drafts in here do we?so keep the bloody ball in the middle.YES I KNOW IT WOULD NOT HAVE BEEN A BALL ON A REID AND SIGRIST TURN AND SLIP.Before I get jumped on. BYE BYE.

['I' in the sky]

I seem to remember in my early training a conatant humming in my right ear " Ball ..... ball in the middle .... watch that ball now ..." and I am no different with my students. Once your in the habit of checking it, it's not a big deal to keep it there. In a C150/152 the pressure required should not be that great. I've never flown a C172/PA28 type plane though that didn't have a rudder trim, although it's amazing how many people haven't been taught how to use them, and the number of PA28 ones that have just been wound off the end of the spindle.

[212man]

Lots of good stuff, as usual. I would emphasise the use of a distant object, ideally a cloud as you won't get confused by ground drift. The ball is a backup, like the ADI is a back up for the a/c attitude; of course you use the real horizon for establishing a/c attitude, don't you?

I agree with the remark about flying a type with more trim variation as it will make keeping the a/c in trim more of a second nature. It is far more apparant when out of trim in some types (even more so in helicopters).

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Another day in paradise

[This message has been edited by 212man (edited 23 October 2000).]

[Barney]

Hi,

If you want to experience this for 'real', go for a flight in a glider.

Seriously, the adverse yaw/aileron drag generated by a glider in a turn will teach you all you need to know about using the rudder/coordinated turns etc.

Just a thought.....

Barney

[TrueNorth]

Nice one Barney - I`ve been thinking about doing some gliding...

Thanks to everyone for their help. I do like this forum!

[pulse1]

When I was revalidating my PPL some years ago on a 152 I was using more fuel from one tank than the other. I was told by my instructor that this was because I did not have the ball in the middle most of the time - wings not level.
Now, if I fly a 172 on 1 - 2 hour cross country in relatively calm air, mostly with the ball in the middle and little or no rudder required, I still find I sometimes use more fuel from one side than the other (selector on both).

Does this really mean that I have been flying badly? If so, how do I improve?

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"If you keep doing what you've always done, you will keep getting what you've always got"

[New Bloke]

Pulse1,

Same happened with me, I was told it is 'cause I'm fat.....

[pulse1]

New Bloke,

That means it will get worse when you fly solo!

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"If you keep doing what you've always done, you will keep getting what you've always got"

[fallen eagle]

With referance to uneven fuel usage 150/2 172.its not to do with your weight at least not in my view.Might be a bit of out of ballance flight,but not much.Every one of the type I have flown seems to use in preferance fuel from the port tank first,there is a cross feed but it takes a while for it to catch up with demand.Maybe something to do with slightly differing pressure over the port wing,prop slipstream etc.Any other offers???

[IanSeager]

fallen eagle - apparently it has something to do with the venting system. There are two reasons why the fuel in a high wing Cessna flows to the engine. The first is gravity, the second is a slight positive pressure. Most Cessna high wings achieve this pressure through the L shaped vent on the left wing. The pressure should be even in both tanks. In order to make sure that it is even (apparently bad things happen if it isn't) Cessna 'link' the top of both tanks from a point at the top of the fuel tanks (Inboard). Because many Cessna tanks are loing and thin (Some 182 LR tanks are about 8 inches high but 7 foot long)and because the wing has some dihedral the equalising vent can be full of fuel rather than air. So - the right tank happens to be feeding the engine, the pressure comes from the left tank which pushes fuel rather than air through the pipes, the right tank remains and indicates full, while the left tank appears to be emptying. Worry not, this situation resolves itself when the left tank empties enough for the connecting vent not to be immersed in fuel.
Hope that helps
Ian
PS The above is sort of a precis from a six page document that the Cessna Pilot Association have put out.

[pulse1]

Many thanks Ian and FE for restoring my confidence. Having about 70 hours in Tiger Moths and about the same in gliders, both many years ago, I didn't think my coordination could be that bad - initially a little rusty perhaps.

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"If you keep doing what you've always done, you will keep getting what you've always got"

[New Bloke]

I still think it is pilot weight. The same thing happened to me in a Pup 100 but NOT in the Pup 150. Only happened solo and my mate Ali McBeale had no problem at all ;)

[before landing check list]

Hello True North,
You have been told correctly, the airplane does not know the wind is blowing. It doesn't care. The only time YOU care is when performing ground reference manuevers. Downwind turns are ok if ball is centered. And then the wind does not push it at all, just moves with the airmass. Like a boat going across the river, same principle. read "Stick and Rudder". Also if all else is equal the fuel used should be the same between tanks should be the same if wings are level(trim) Or the A/C may prefer one tank over the rest. As far as fixed trim goes, the A/C should be in trim with feet on the floor in the condition it is in most, usually cruise. Exception for instance are tow or jump planes that spend lots of time climbing. Remember the feet move when hands move, ALL THE TIME. ok?
j

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What can you conceive more silly and extravagant than to suppose a man racking his brains, and studying night and day how to fly?

— William Law, 'A Serious Call to a Devout and Holly Life XI,' 1728

[This message has been edited by before landing check list (edited 05 November 2000).]

[TrueNorth]

OK!

Thanks all :)

[JamesG]

Ian Seager describes the C172 tank link - don't I know about this.

On my first flying lesson, pipe developed a leak during the taxi and we had to abandon ship as a small (but worrying) amount of Avgas came through the headlining onto my hair.

I learned about not going near sparks from that!

[Mach_D]

True North

I think you have had an excellent response to your question and agree with most of what has been said. However, I cannot belive that your instructor couldn't have shed some light on this issue. Are you sure you're not teaching yourself to fly?

For what it's worth, as an ex Glider pilot I used to be heavy on the feet when flying C150/152. The C150 doesn't have an adjustable trim tab on the rudder ( or at least the ones I am familiar with)and the C152 often get 'adjusted' by students who have forgotten their original walk round brief. However, it takes a pretty meaningful deflection before you would need boot loads of rudder to balance. Make sure your wings are level (equal sky!) then apply rudder as required to balance keeping the wings level.

I used to fly everywhere with one wing down and fight with the Rudder to keep the ball in the middle. Operator error!

Best of luck

[Tinstaafl]

I've noticed lots of students who fly wing down in the early part of their training.

Students in the left seat would tend to fly R wing low, and those in the right seat (eg trainee instructors) would fly L wing low

Seems to be related to the centerline offset of the seats plus trying to use the cowl/visible sky as the reference for horizontal. They appeared to be trying to achieve an equal ground/sky field of view as they looked from one side to the other.

I suspect that the uneven view from the left or right seat, compared to a centre line seat position is to blame.

In a similar vein is students trying to align heading by using the centre of the cowling instead of a point directly in front of themselves. Again, this is with the offset seating.

One fellow was so adamant that he was flying wings level & heading accurately that I had to line us up dead straight on the runway with him on the centreline then mark the windscreen where a the end of the runways 'touched' + a spot that was aligned with the RWY end centreline.

After that, go flying & see the difference.

I think that if instructors allow students to develop these habits they become ingrained as their primary 'reference' instead the correct one(s)

[Squawk 8888]

True North

As a followup to the suggestion of trying a plane that needs more rudder, if time & funds permit I recommend spending an afternoon in a glider. Most gliders have no gyro instruments, just the pitot-static and a drift string up front. Because you have no torque, precession or asymetric thrust to deal with you get a very good feel for what the controls alone are doing.

[TrueNorth]

Mach_D,

You`re right, I have had an excellent reponse, and I would like to thank everyone for all the helpful replies.

I think I may have mis-represented my instructor a little, however. I am coming to the conclusion that what he meant was "we`re 5 miles from the field after a long flight, so if your foot hurts don`t worry about keeping the ball in the middle. You`re fighting the trim, which is out of whack - once it`s fixed the plane will fly straight. For now, just let it do what it wants." In my ignorance I misunderstood him to mean don`t worry about it EVER, which as so many of you have pointed out, is patent nonsense.

The shock of what I THOUGHT he had said made me forget or doubt everything I thought I knew about aerodynamics and the forces acting on a plane in flight! You have all helped to ease my fears...thank you. (Still planning to do some gliding, though.)

Mach_D, sometimes it feels like I am teaching myself to fly...hour-building for the Commercial!