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Keeping the ball in the middle

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Keeping the ball in the middle

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Old 19th Oct 2000, 20:39
  #1 (permalink)  
TrueNorth
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Question Keeping the ball in the middle

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?
 
Old 19th Oct 2000, 21:36
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Noggin
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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.
 
Old 19th Oct 2000, 21:42
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TrueNorth
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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

 
Old 19th Oct 2000, 22:33
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John Farley
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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
 
Old 19th Oct 2000, 23:00
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TrueNorth
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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...

 
Old 19th Oct 2000, 23:12
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Noggin
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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?

 
Old 20th Oct 2000, 00:31
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John Farley
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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
 
Old 20th Oct 2000, 04:56
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Oleo
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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!!
 
Old 20th Oct 2000, 12:18
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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.
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Old 20th Oct 2000, 13:16
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GT
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For what it's worth, I think Noggin's first post is about spot on.
 
Old 20th Oct 2000, 15:02
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Manwell
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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..
 
Old 20th Oct 2000, 15:13
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TrueNorth
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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!
 
Old 20th Oct 2000, 15:58
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Qhunter
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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 ?
 
Old 20th Oct 2000, 20:00
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Tinstaafl
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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.
 
Old 20th Oct 2000, 21:58
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FNG
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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.
 
Old 20th Oct 2000, 22:12
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TrueNorth
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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

 
Old 21st Oct 2000, 20:48
  #17 (permalink)  
fallen eagle
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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.
 
Old 24th Oct 2000, 01:40
  #18 (permalink)  
'I' in the sky
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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.
 
Old 24th Oct 2000, 02:18
  #19 (permalink)  
212man
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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).]
 
Old 2nd Nov 2000, 13:29
  #20 (permalink)  
Barney
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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
 


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