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Keeping it straight on landing


Chucky
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I've recently changed from flying a Jab LSA to a J160 and I am having trouble holding it straight after touchdown.My last two landings have been all over the place like a mad dogs breakfast! I don't know if i'm just over correcting or what.

 

Anybody got any advice? I'd love to hear it.:confused:

 

Thanks,

 

 

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Good one Doc :thumb_up: - keep pulling it right back (the stick) as the aircraft slows, as far as it will go and keep it there (until the nose comes down by itself).

 

regards

 

:big_grin::big_grin:

 

 

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This problem is likely because of the Jabiru people's insistence in fitting the same tyre on the nosewheel as the mains. It's because it's a kind of a 'square' edged tire and when the weight is on it it skews all over the runway.

 

I know of a school with Jabs that was having literally one a week run off the runway because of this problem so the new CFI fitted 'round' tires to the nosewheel and the problem instandly went away.

 

As advised by Dr and Pete, stick back as much as you can without mono-ing. I keep the nose off the ground for as long as I possibly can on the landing roll and I get it up slightly as soon as practical on the takeoff roll. It can get a little interesting in a left crosswind in a J230 if you lift the nose off too early, but that's a whole other story!

 

 

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That doesn't seem to be a problem (leaving the mains with the original tires). You could describe the sensation of the square tyre problem as riding on the backbone of a cow (any cowboys here?) You'll notice a similar problem as a passenger in a 767 versus a 737 (not the same nosewheel problem, but the same sensation is experienced).

 

Many an unsuspecting Jab pilot has been caught out by this.

 

 

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Guest Pioneer200

I have noticed same thing when landing Jab J160

 

Every now and then it wants to veer left on landing and it takes a fair bit of right rudder to get it going straight

 

When this has happened it has always veered left NEVER right!

 

 

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I have noticed same thing when landing Jab J160Every now and then it wants to veer left on landing and it takes a fair bit of right rudder to get it going straight

When this has happened it has always veered left NEVER right!

Could the Tire pressure in the left be slightly lower than the right one...? or the brake is dragging a little...maybe...;)

 

Just a thought I had....025_blush.gif.9304aaf8465a2b6ab5171f41c5565775.gif

 

 

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is it possible to maybe `over inflate` the front tyre slightly to get the `rounded` profile? I know in my 172 if the front is too high in pressure, it can make a `shimmy` worse but maybe ok in the Jabs.

 

 

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Guest pelorus32
Would changing the mains as well as nosewheel tyre also help?

Changing to a Tecnam would solve the problem entirely!

 

041_helmet.gif.78baac70954ea905d688a02676ee110c.gif041_helmet.gif.b33edb063c342f545e37fe5acb1c5db2.gif041_helmet.gif.78baac70954ea905d688a02676ee110c.gif041_helmet.gif.b33edb063c342f545e37fe5acb1c5db2.gif041_helmet.gif.78baac70954ea905d688a02676ee110c.gif

 

024_cool.gif.7a88a3168ebd868f5549631161e2b369.gif

 

 

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Same staying on the runway problem with a kit built J230 here.

 

Mains, axles and etc were removed from the undercarriage legs and the wheels refitted and carefully realigned.

 

End of problem!

 

Factory built Jabs aren't exactly renown for their precision fitting and finishing so a wheel alignment might be on the cards

 

Old gliding instructor's rudder technique taught to pupils with rudder walking problems was to place heels firmly on floor and use foot movement through ankles to move rudders.

 

Was taught this very early in my flying as it stops rapid and excessive application of rudder by young, strong and gungho farmer's big feet.

 

Particularly useful on landing roll out.

 

Might not work on some LSA's due to rudder pedal configuration.

 

 

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is it possible to maybe `over inflate` the front tyre slightly to get the `rounded` profile? I know in my 172 if the front is too high in pressure, it can make a `shimmy` worse but maybe ok in the Jabs.

I had the same thought, before seeing your post.. Any views out their on over-inflating to round it up a bit??

 

 

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Maybe not over-inflating as such, but rather attempting to keep it at the maximum recommended pressure and keeping an eye on it. Either that or fit a different tire. Jab sell different types.

 

 

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Darting off the runway

 

I used to wonder why I was darting off the runway after touching down after a landing.

 

I finally woke up that it only happened when I was landing in a cross wind whether it was in a Jabiru LSA 55, J230c or Wally's Tecnam at Narrandera.

 

But then I am almost always landing in some sort of cross wind even if it only a couple of knots and is almost unnoticeable during the circuit.

 

So if I land in a cross wind from the right I have the A/c banked to the right with left rudder on to keep the a/c lined up on the runway.

 

Once I touch down on a single wheel or two wheels in this condition (if I don't change the rudder deflection) the a/c will immediately swing to the left even if the nose wheel is on the ground because the rudder will now be pushing the tail more into the wind on the right but the mains are anchored on the ground and starting to point to the left in relation to the runway and the nose wheel is also turned to the left.

 

So I needed to reduce left rudder input the moment a main is on the ground but the wind is now trying to push the tail to the left before the front wheel is on the ground so it still needs some rudder to stop it weather cocking into the X-wind.

 

Then I would have it almost neutral once the front wheel touches down otherwise I would be doing a very rapid close examination of the left hand edge of the runway because the rudder pedals are linked to the front wheel steering.

 

The distance from the front wheel to the mains is very short on a Jab so a small rudder movement results in a large change in angular direction once the front wheel is grounded - but the Jab cannot turn as sharply as a castoring front wheel would allow with the aid of individual main brakes.

 

So it makes life much easier if I keep the front wheel off the ground for as long as possible and coarse steer with the rudder then remember that I am fine steering with the front wheel once it drops on the ground and then will probaly need even less rudder pedal input to keep it straight up the runway.

 

This is all very difficult because I cannot see how much rudder I have applied as my feet are not within view.049_sad.gif.af5e5c0993af131d9c5bfe880fbbc2a0.gif

 

I am going to have to learn all this again once I get my J160 flying as the rudder pedals will feel different at that moment of truth as we touch down in every different x-wind component.

 

I always reckoned that it would be easier to learn X-wind landings if we had a rudder (or front wheel) position indicator on the panel in front of the pilot. I was told recently that there is such an indicator on Boering 747s.

 

I guess the spring loaded rudder centring system on the Jabirus is one approach to this problem - but then I was always reluctant to take my feet off the pedals in the middle of a X-wind landing then without any input from me, relying on the rudder to go to the neutral position which is actually about 5 degrees of right rudder.

 

This might even result in a ground loop if the x-wind is strong enough and leave the two ends of the a/c no longer connected by the fuselage.:black_eye:088_censored.gif.2b71e8da9d295ba8f94b998d0f2420b4.gif

 

 

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Quote

 

"if we had a rudder (or front wheel) position indicator on the panel in front of the pilot"

 

My instructor told me it's called the ball.

 

The jab 160 i've trained in always turned port or starborad when applying brake. It was unpreditictable which brake that would seem to crab more than the other. As it starts to grab you release a bit off pressure then reapply to get a more central breaking effect.

 

Not having used toe brakes on a plane, but would i be right in saying that having used both , most would choice toe over hand break.

 

 

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The weekly featured magazine article that will be published tomorrow (Sat morning) is on crosswind landing - it is a very interesting read - look for it at the top of the home page from 9:00am tomorrow (Sat 8/11/08)

 

 

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I run 50/55 PSI in the nose tyre. This does indeed make the cross section more rounded. The effect is like fitting a narrower tyre.

 

Despite my harping, students love to have that nose wheel on the ground, even at appallingly high speeds, probably because thats what 747 pilots do on TV ( V2 ROTATE!! ). Of course the steering gets squirrelly so they fight it some more and of course the situation deteriorates. Ultimately I intervene by pulling the stick back but ya gotta give 'em some rope so they can learn. Some students think the plane will tip over backwards if the stick is brought further back after touchdown, yes really!

 

The problem for the commercial operator is to protect the aircraft from the students actions.

 

The solution is to keep the nose tyre hard. This is because the tyre will break traction before the swerving becomes too serious. Thus the structural loads on the nose leg are relieved and the aircraft is rendered incapable of making that final wild swerve ( left ) to the accident scene. It always gladdens my heart when I hear the sound of that nose wheel skidding!

 

 

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  • 9 months later...
Guest Kevin the Penniless

Just plenty of back pressure on the stick both during takeoff and landing. I found the Jab was all over the shop until I was told to keep the back pressure on.

 

 

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