What is wrong with the jab?

[Guest brentc]

Jacmiles, the front wheel is too 'square' is the best way to describe what is wrong with it. Imagine that you had a wheel barrow with a square edged tyre and you have a full load in it. When the load tips slightly to the side, you end up with a large load on a skinny edge which makes it hard to control whereas with a 'round' type tyre the load is evenly spread across the surface area in contact with the ground.

 

Attached pic is of a Jab with 'round' tyres. Can you tell the difference?

 

I'm trying to find a good 160/170 pic now.

 

I will go out on a limb and say that if the aircraft is flown properly and slowed as much as possible as ANY nosewheel aircraft should be, where the nose wheel is put down as late as possible in the piece then this control problem won't happen.

 

Long ago when I was taught in a Gazelle I was taught to treat the nosewheel like it is extremely fragile and to hold it off the ground as long as possible in the landing roll and to lift it off as soon as possible in the takeoff roll. If you did this on landing in a 170 you would be travelling so slow when it touched down that you'd be stopped in around 20-30 metres and directional control would be not lost under almost any circumstances. I fly over the fence at 55 knots to achieve the most stable results in the 170.

 

It is a fact of life that in ANY aircraft directional control can be lost and appropriate actions should be taken in the instructional process to ensure that any specific aircraft tendencies be overcome with appropriate procedures. As for blaming the aircraft design and or manufacturer, just look at how many of these are out there and how many are running off runways outside the training environment (amost nil).

 

No reflection on you Kent, you have joined a long list before you. Hopefully you'll feel better if something did go wrong under the hood :-)

 

 

 

[facthunter]

Characteristics.

 

Comment on the smaller nosewheel. What it mainly does is to put more weight on the mains for the same touchdown attitude. These aircraft should be held off so that only the mains touch initially, and I would have thought that if the nosewheel is held off AFTER touchdown, then the nosewheel plays no part in controlling the direction that the aeroplane goes in, at that point. Could the left wheel have been partly deflated?.

 

Another factor is that this is the first time that the right seat has been unoccupied, so the plane is left side heavy... Nev..

 

 

[Guest brentc]

and I would have thought that if the nosewheel is held off AFTER touchdown, then the nosewheel plays no part in controlling the direction that the aeroplane goes in,

Exactly my point Nev. I don't see enough of this these days!

 

That being said though, I do sympathise with Kent in that the J170 does come in prior to landing VERY nose low to the point where it is often difficult to raise the nose above the rear wheels. Time and time again I see the 170 porpoising down the runway after touchdown alternating between mains and nosewheel. The problem is usually rectified by the nosewheel touching down at a lower speed. It's all about balance.

 

 

[BigPete]

Once the main gear is on the runway - keep pulling the stick ALL THE WAY BACK as the aircraft slows - until you can't pull back any further. The nose wheel will come down at a much slower speed, when it's ready to.

 

If you'te not doing this - then you shoud be.

 

regards

 

 

[Guest Orion]

Yes, it seems i'm up for a few beers, as they say you can run but you can't hide. It surprised me how fast the grapevine works.

 

Point taken about lowering the nosewheel as late as possible in the picture and maybe that was part of the problem. I'm very open to the notion that i may have contributed in some way. Would be foolish to think otherwise.

 

Main gear defineatley touched first this wasn't a case of wheel barrowing. CFI assures me that from where he was standing the landing was good.

 

My issue here is the ability to regain directional control. I agree i may have contributed to the left veer (still working it thru my mind) pehaps nosewheel down a touch too quickly however the point is missed.

 

Once the loss of directional control occurred simple application of right rudder should have started to bring it under control, That the point no mater how much i pressed the right rudder pedal the direction didn't change i swear if i had pushed the pedal any harder i would have pushed it out of the firewall. Paul can testify i'm not a small bloke.

 

interesting discussion about pedal movement down instead of forward. does this mean that in some circumstances its possible to depress the rudder pedal and rather than it move the nose wheel the pedal movement is actualy just flexing or deflection of the rudder pedal arm from its attachment point. If so that would explain why no response when the rudder pedal was pressed.

 

Cheers

 

Kent

 

 

[jetjr]

I have a J200 with around 200+hrs on this and an old 55

 

I too had a bush experience but after alot of afterthought it was largely my fault

 

Too fast, slight x cross wind, didnt hold off the nose wheel enough. And it happens VERY quickly

 

Ive learnt to treat the front wheel like its made of glass, get it off the ground as early as possible, and work as hard as you can to hold it off when landing

 

Im sure the rounded fr tyre would help, but most of my issues were from landing too fast.

 

Also found if you are even a little too fast the landings arent positive, ie aircraft will try to fly again. this leaves very little weight on the gear and makes it very tricky as the rudder isnt much help as these speeds either, then when it does come down your front wheel is crossed up

 

Theres a certain speed where it all works against you I reckon.

 

I landed with just a single stage of flap for a while which I reckon helps to reduce the problem until you get a bit better. Its a lot quicker speed but more positive sink and less floating. Also make sure you are looking a long way down the strip, not at the ground in front, looking too close stuffs up final few seconds ofyour judgement

 

Just my opionion remember, not a training tip, talk to your instructor. Im also in a different but similar AC

 

JR

 

 

[Guest Ken deVos]

...When the aircraft veered left and corrective action being application of right rudder failed to regain directional control then, with the benefit of hindsight, application of brakes may have slowed the aircraft better. In this situation everything is happening at once and probably as i was attempting to regain directional control i may have neglected to apply sufficient brakes....

Hi Kent

 

I fly the J160/170/230 and have not experienced the problem.

 

However, I will say that once you are veering off the runway, application of brake may actually hinder directional control. The brakes are only going to slow you in the direction of travel and you will need to release the brakes to turn.

 

 

[Guest brentc]

If the pedals are extended fully and you are close to full lock in either direction the situation exists where you could push down on the pedal instead of forward (if the modification hasn't been made to your aircraft).

 

Therefore you may have been pressing DOWN on the right pedal which would give you full lock to the LEFT.

 

 

[mAgNeToDrOp]

As an additional thought - In discussions with my CFI about directional control in the Jab, more specifically the J230, with the nose attitude too high part of the rudder can be effectively *blanked* out, by simply lowering the nose a bit, but still keeping the nose off obviously, there is suddenly more rudder control, due to I supect more airflow over the entire rudder surface. May apply to a 170 with same wings as 230 and bigger fuse, any thoughts?

 

CFI has also installed soft steering kit (not sure of the proper technical term but is supplied by Jabiru) on the J160 and this has seemed to help alot as the nosewheel steering is not so twitchy on the ground ( just a bit of a pig to turn on a narrow strip now)

 

 

[facthunter]

Nose wheel strut length.

 

I have seen some Savannahs that sit the way a small plane should. That is nose down. This reduces the chance of weight transfer to the nosewheel on landing. Once you use the brakes you are putting even more weight on the nosewheel, and the plane is still getting lift from the wings, so there is practically no weight on the mains. Particularly with a lot of flap. This is a very directionally unstable situation, and places a large load potentially on the nosewheel structure. No ultralight has a strong enough nosewheel to put up with this sort of treatment, even if the steering linkage is up to it. As has been said already "treat it as if it is made of glass".

 

Landing too fast is a common error. It creeps in when long runways are available, and the extra airspeed is used because it's the easier way to do it.. Porpoising,& wheelbarrowing can result with sometimes a large amount of damage to the aircraft. in any case it's a bad habit as one day the strip will not be long enough.

 

I am generallising here, and not stating that this is the case here. There could have been a rock in the brake caliper or something else. Nev..

 

 

[turboplanner]

I think I've made just about every one of the mistakes listed above.

 

To be fair to Jabiru, had the rudder pedal AD been complied with?

 

 

[Modest Pilot]

I would check the wheel alignment. It's not particully easy as it varies with load and rebound etc. It seems best to bias towards toe-out if in doubt, several reports say that the aircraft is a bit squrrelly with toe-in. On the 200 series check the forward aft bias, the four seater wheels are shimmed about 60mm further rear than the 2 seaters. Forward seems to be better with the two seaters tending to a more forward CG. (most of the time) Thought long and hard about toe brakes, There's not much room to work in and you lose legroom. To be honest I don't use the brakes much above 20kn, I fitted Trelleborgs all round, mainly for burr resistance, landing with a flat tire might be not be much fun on a runway. Still doesn't solve things if you hit a soft patch on one side during T/O landing. (Lots of sandy runways in S E QLD)

 

"Oh and don't forget to keep flying the aircraft right down to taxi speed!"

 

 

[nong]

Hey ORION. Lucky you stacked a Jabiru. Imagine being trapped under a Sportstar.

 

 

[motzartmerv]

Another thing that may or may not have contributed.. In a glide approach (as you said you do) the nose attitude is very low, even lower then the normal low jab attitude. This makes the transition to the flare attitude harder and needs to be done at exactly the right time..

 

 

[Guest Orion]

Hi Mozartmerv

 

As i said when i described the incident round out and touchdown was as perfect as i could do. The mains just "kissed" the runway. I cetainly didn't bounce the aircraft into the deck or drive it into the ground had done both earlier in training by rounding out a bit late or not checking and holding the aircraft for long enough after round out so i'm familiar with both.

 

Perhaps i didn't describe it accurately my reference to glide was glide angle my first solo landing wasn't a glide (power off) approach.

 

Problem started when nosewheel touched. Perhaps i didn't hold nosewheel off for long enough i'm open to that and certainly next flight i'll be concentrating much more on holding nosewheel off the deck, and once down keeping back pressure on controls to keep weight on mains.

 

I come back to the attempt to correct the loss of directional control. This is what concerns me.

 

Replaying the incident in my mind i'm nearly certain that i didn't apply brakes at all.

 

no time.

 

as soon as directional control lost and beleive me it veered so sharply to the left at one point i beleived the right wing was going to bury into the runway.

 

was concentrating on trying to regain control.

 

position of brakes on Jab means only two possibilities exist, either let go of controls with right hand to apply brakes, under the circumstances probably not a natural act or let go of throttle and attempt to apply brakes with left hand again same applies.

 

When this happens you really are hanging on for grim death and not really inclined to release your grip on anything.

 

Your limited training kicks in.

 

The aircraft is going left so you apply right rudder simple as that and thats what i did.

 

problem is it didn't respond so what else to you do ?

 

Not sure of the answer

 

If i tried to get it back into the air at that point fear is that full throttle on an aircraft careering out of control may have only worsened the situation so i ruled that out.

 

Whats left basically hang on and ride it out ?

 

Cheers

 

Kent

 

 

[Guest Brett Campany]

Hey Kent, mate I reckon by the sounds of it, you did everything you could. As mentioned before, I did the same thing not long ago, she just likes to get away from you. How's the body holding up mate?

 

 

[Guest Orion]

Couple of nice dark bruises on torso, shoulders a bit sore from the harness apart from that fine.

 

Focus now is getting back on the horse asap.

 

Thanks for asking.

 

Cheers

 

Kent

 

 

[Guest brentc]

Last time I saw this happen and full power was applied in an attempt to resolve the problem, the aircraft flew into the side of a shipping container and was destroyed :confused:

 

 

[lazerin]

Quick question from a Jab uninitiated....can someone explain the control lay out in the Jab cockpit?

 

From what I've gathered by reading this thread, there is a centre stick which seems to be in the right hand, and the throttle is controlled with the left hand? This means the throttle is on the left side/wall of the cockpit? Are there dual throttle controls?

 

 

[mAgNeToDrOp]

This should give you a general idea of the jab panel, obv can differ, brakes and trim in front of centre stick

 

 

 

[ianboag]

I had an experience a bit like this in a Cessna a week after I purchased it in 1999. I have since had a bit of a think about it and figured what (I think) I did wrong. I was interested to read this one but it sounded a bit different to mine.

 

Until I read the bit "veered left" with "right wing almost hit runway" ie the aircraft veered left and tipped right.

 

Remember that when you are flying and you pile on right rudder the left wing goes up ....

 

I have explained my mishap to a number of people viz x-wind landing, all three wheels on the ground, then right (upwind) wing lifted and aircraft veered sharply and asked for opinions. First question was does the aircraft go straight or veer left or right (it veered strongly right - about half the people get that), next was what to do - half said hard left rudder which is what I did. This of course made the right wing go further in the air etc etc. So I leaned hard on the left toe brake and eventually the plane stood on its nose, banged the prop and left wingtip on the runway, then dropped back on to all three and rolled smoothly forward. Except the prop wasn't turning and had bent ends. The 172A Cessna is one of the most docile aircraft on the planet. The tower observed "that looked like it hurt" .....

 

I have since decided that my key error was not to immediately whack on max aileron to get the offending wing down. I don't know if this helps as advice in this case .... Jabs don't have the most authoritative ailerons on the planet anyway.

 

The main thing this illustrates for me is that when you move outside the envelope the outcome gets to be quite random. One should work hard to stay inside it.

 

Cheers IB

 

 

[lazerin]

Thanks magnetodrop, that makes things clearer.

 

 

[turboplanner]

Kent, I had the J170 steering lock up on me after a medium turn while taxying. As we headed for a 172 the Instructor suggested, more foot pressure, so I stopped, then taxied away and demonstrated the condition a couple more times. He still didn't believe me so I levered myself against the seat and all but stretched the fuselage, but the nose wheel remained locked at an angle.

 

I strongly suspect from your repeated assurances that you couldn't change the nosewheel direction that this is what your problem was. That was the reason for the AD, so it's important to know whether the AD was acted on as a starting point

 

 

[Yenn]

How many uneventful landings had been done in this plane before the accident? If more than a few it would point to the plane being OK when the previous landing was completed.

 

Was there any evidence of damage which could have caused the accident, and if so did it happen before or during the accident. If the answer is no damage evident, then it points to pilot error.

 

For pilot error to occur on first solo in any type of aircraft not uncommon, but it is no good berating yourself about it, nor is it any good to not see what could have happened. At least Orion you appear to be able to get on with it, and I don't think anyone here would condemn you if it was your fault. One of the great things about making mistakes is being able to share them and help someone else avoid the same fate.

 

 

[skydog]

Any crosswind?

 

The pilot describes the weather conditions as OK but I suspect some XW.

 

I only have 80 hours on Jabs but notice they are extremely light aircraft and susceptible to the slightwest crosswind on landing. I have had 2 rather scary unexpected landings veering off one direction or the other opposite to the wind direction.

 

Fast action on the aileron is required plus rudder to correct it but it happens quickly on the Jab due to its light weight and you have to be aware or have a few hours up your sleeve to counteract it quickly. Contrary to opinion in this thread there has been very many incidents of Jabirus running off the runway into ditches etc just read the airsafety magazine from CASA over the years.

 

The controls such as throttle, brakes and flaps are totally out of standard and although as an experienced pilot you can fly them quite OK as I have but there must be a reason for aircraft makers to use more conventional controls as found on allmost all other aircraft. The Jabs would be great planes in my opinion if they had conventional panel throttles, differential foot brakes ( how much extra would they really cost ) and electric flaps. Some versions such as the J230 etc now have electric flaps and panel throttles, which is great, come on Jabiru , bring on diff foot brakes and make this great little plane even greater.