What is wrong with the jab?

[Guest brentc]

Interesting assumption based on an upside-down aircraft i_dunno

 

 

[Captain]

Hey guy's don't mean to harp on the subject. 6'00 news Coffs Harbour. Old Bar airfield near Taree. Jabiru upside down. looks like a write off pilot (and passenger I think) injured Not sure of the details. Eyewitness report states the aircraft touched down, i assume normally then veered sharply off the runway and overturned. Further report stated that the cause seemed to be with the brakes, though the reporter probably didn't understand the workings of the aircraft...couldn't have been a problem with the rudder or nosewheel assembly could it.....no of course not.

Look out fellas. Wayland1 is being objective again.

 

Don't worry wayway. The truth will come out and what most of us here like to do is actually find out what REALLY happened with each and every accident or incident.

 

As a Jab owner I, for one, certainly want to know the facts, don't you too?

 

You'll be surprised, but somebody here will most often know or find out what actually occured ..... so keep your shirt on, mate, and let's see what is the truth.

 

Kind regards Geoff

 

 

[turboplanner]

Yes, look at the embarrassing sequel after the last upside down event.

 

 

[slartibartfast]

New report here including picture of inverted J160.

 

Witnesses seem to be saying it ran out of runway. Old Bar is only about 540m long.

 

 

[Captain]

Hey guy's don't mean to harp on the subject. 6'00 news Coffs Harbour. Old Bar airfield near Taree. Jabiru upside down. looks like a write off pilot (and passenger I think) injured

Based on description in the link that Ross has given it sounds a bit like a ground loop before running out of room before the boundary fence ..... but does anyone have any more details?

 

And based on the photo it hardly looks like a write-off, eh Wayland?

 

What is the true position?

 

 

[motzartmerv]

Yep, sounds like an overun situation to me aswell.If she skewed off after touchdown they woulda went through a fence. Tough birds but aint they, looks like you could flip it over and fly away..

 

Good on the bystanders for helping out.. Great stuff.:thumb_up:

 

 

[Guest brentc]

The hardest part with that 160 is getting it back upright again without wrecking it further. I see the windscreen and side window perspex are smashed so it would be a bit bent in the middle possibly. Not the first and won't be the last Jab in need of some major repairs but should be up and flying again in no time.

 

 

[Guest ozzie]

that wheel spat wouldn't have dug in during the turn and tripped it up.

 

 

[ianboag]

My 2c worth.

 

When you veer hard LEFT on the ground the aircraft tips sharply RIGHT - possibly to the extent of lifting the left wheel off the ground and/or scraping the RIGHT wing on the runway(?).

 

I'm not sure how much steering authority the nosewheel has when things get to this point (tipped sideways). And of course if the aircraft is still "flying" a bit, then hard RIGHT rudder will lift the LEFT side some more. Perhaps it is possible to get to a state where it isn't steerable any more because it's tipped over so far.

 

Why it veered in the first place is a different question

 

IB

 

 

[Captain]

Good points made by Ian

 

Has anyone here had to actually ground loop a Jabiru? If so what really happens and is Ian's description about right?

 

 

[poteroo]

My take on 'groundlooping' a nosewheel a/c is that if the nosewheel is hard down under braking - the aircraft will roll over the opposite direction to the intended turn. On a wet, slippery, but firm, surface it might not.

 

The other more sensible way to 'groundloop' is to get/keep the nosewheel off the ground, and then kick in full rudder. My kingdom for toe brakes on the J160 !

 

Re the original discussion:

 

J160 has no landing vices if heldoff to touch on the mains....and progressive back pressure then applied to hold the nose up until the elevators lose effectiveness. Only after the nose then slowly falls to ground should any brakes be applied. A trickle of power left on through the roundout will help with elevator command, and ensures you keep the nosewheel off.

 

When you do this properly, you'll need to be looking down the left hand side of the engine cowls to see your runway at touchdown. If you can see over the centre of the nose at touchdown......then you are not yet in the desired landing attitude. And, unless you are really sighting down the LHS of the cowls, you are several degrees facing the left. So, the aircraft departs left off the runway.

 

We have our students sit in the J160, on a taxiwayrunway centreline, and move the aircraft around, and tip it down at the tail, so that the student can really 'see' what is straight, and what attitude it really takes to have the nosewheel 'off the ground'

 

So far, we've had no incidents by training this way.

 

happy days,

 

 

[facthunter]

Deliberate groundlooping.

 

One point that hasn't been mentioned so far (unless I've missed it). groundloop INTO wind, You will rarely achieve much the other way. AS far as groundlooping a tricycle U/C aircraft with the nosewheel in the air, I wouldn't count on it. As the mains are well behind the C of G, the aircraft has its best directional stability in this condition, ie any side load in the turn tends to straighten or lessen the turn.

 

The tailwheel aircraft has the wheels well forward of the C of G ,(especially when the tailwheel is on the ground) and the sideload encountered in the turn , once it starts, acts to make the yaw (turn) increase, so they are directionally unstable, and will groundloop any time you let them.

 

Like wise, when there is a lot of weight on the nosewheel, (when you are touching down too fast), you have an oversensitive condition, which is not corrected by the natural stable tracking of the mainwheels, and you either break the nosewheel, and/or end up putting a wingtip into the dirt, and maybe go over on it's nose, subsequently. Nev

 

 

[poteroo]

Actually, by holding the nose high, your CG is rearward of it's 'normal' position with the nosewheel on the ground. Having the tailskid or bolt nearly touching the ground would be my 1st choice if trying to swing to avoid a head-on impact. You have to make the aircraft 'directionally unstable', so to speak, for it to be able to swing into wind, (good point,btw). You'll have great difficulty in getting a nosewheel a/c to make a fast turn without it rolling over onto a wingtip and the prop while it's directionally stable.

 

Yes, the taildraggers do it of their own accord, but even then, they'll often dig in the outside wheel - putting the wingtip into the ground and then often nosing over.

 

happy days,

 

 

[facthunter]

True enough.

 

You don't have much option without differential braking. The nosewheel is often a castoring feature as well, in some designs. The nosewheel is not strong enough to 'muscle" it either, so it would be (as always) a good idea to know what your aircrafts limits are. I would not explore this in the initial training stage, because there is enough to cope with there already.

 

My previous post was directed at "tying up" an understanding of what is going on in the ground run, departure from a straight line situation, so I hope it is read in that context. Nev..

 

 

[Aussie Steve]

The hardest part with that 160 is getting it back upright again without wrecking it further. I see the windscreen and side window perspex are smashed so it would be a bit bent in the middle possibly. Not the first and won't be the last Jab in need of some major repairs but should be up and flying again in no time.

Our Jab was bent in a engine fail ( broke a cylinder to block flange and lifted the pushrod out of the rocker) in May 2007 and is only due back to us this week. Metalurgy test proved the metal was crap. This has been a major fight with Jab and has almost ended in court. As the engine is not covered by insurance ( I,ll bet most of you didnt know that-check and see) unless it is damaged in the crash. Which it was not as it had stopped inflight.the prop didnt even get damaged. But the undercarriage was torn off and the bum split open all the windows smashed apart etc.

 

A compromise has been made on Jabs behalf after the replacement engine failed when fitted to the repaired aircraft and test run.

 

The owner insisted that engine be replaced with a "new" engine at Jabs expense.

 

Which did not happen, so eventually they split the cost between them.

 

Maybe we,ll see it this week... we,ll beleive it when we see it.

 

Our other Jab received a new prop and with not even 30 hrs on it we discovered a crack eminating near the hub. Not a strike on it. Lame tested the torque. Its gone back. We,ll see what happens.