Jab 170 Handling update

[Steve Donald]

That's smart, because it ensures that the mod is done and Jabiru have arguably discharged their 'duty of care'. You don't get your money back until you return the parts you have removed from the aircarft and substituted with the replacement. After all they can be assured the mod has been carried out if you send back the old parts, can't they?Jabiru should be commended for this initiative, we are quick to bag them when by our perception they do nothing on issues they should; so we should be quick to commend them in this instance. Also having discovered some handling anomalies in certain conditions, now 'knowing them' they DO have a duty of care to rectify the issues.

 

Anyone challenging this directive from Jabiru should have another serious thought about the consequences of not carrying out the mod, even if it did cost money to install.

 

David

I agree David but some like not to conform to dirrections ie car seat-belt wearing until they or the passenger departs the vehicle via the windscreen, sad but true, we need to remember Aircraft are under constant development and mods occur for safety and best performance we should embrace this concept.

 

 

[Spin]

Just putting a point of view that I think should be put. It doesn't hurt to get a different slant on things. the "other" side of the coin so to speak. When a course of action is proposed there are predictable consequences. I'm just putting them up for you to consider. Just another opinion. I certainly don't think it is"an emotional response with little basis in fact". Don't SHOOT the messenger...Nev

I guess I could say the same thing, you may not like the legal environment we live in (nor do I a lot of the time) but that doesn''t mean that people have to be kept in ignorance of their rights under that law. My suggestion to Kevin stands.

 

I see the debate has moved on and Jabiru are doing the right thing by people, so to speak and will be paying for the parts. From a PR point of view they would probably have been best advised to lead with that story and put the right spin on it from the get go. I see it virtually daily at work, just a little forethought regarding how the person on the receiving end may perceive your motivation pays dividends.

 

Also, has anyone got any input as to the reasons for the modification - it was suggested that it may be due to a lack of rudder authority in certain situations. I'm battling to understand how an increase in the fixed fin area will address this, normally that is done to increase directional stability in one or more phases of flight or even to assist in spin recovery. I'm referring here only to the new ventral fin, I follow the flap modifications.

 

 

[Vev]

Also, has anyone got any input as to the reasons for the modification - it was suggested that it may be due to a lack of rudder authority in certain situations. I'm battling to understand how an increase in the fixed fin area will address this, normally that is done to increase directional stability in one or more phases of flight or even to assist in spin recovery. I'm referring here only to the new ventral fin, I follow the flap modifications.

This is what was stated in the bulletin by Jab:

 

"fitting a larger ventral fin improves the aircraft’s directional stability – the pilot’s rudder inputs are fewer and smaller in all modes of flight".

 

When I spoke with them this week, they stated there was two reasons 1. Directional stability needed to be improved throughout the flight modes 2. Under server testing, during full power stalls, this modification assisted in spin recovery and provided better authority.

 

Cheers

 

Vev

 

 

[alf jessup]

Mandatory is for a reason by the manufacturer.

 

I would hate to be in anyones shoes who doesn't comply with this and happens to unfortunatley have some sort of incident which traces back to the mod not being done.

 

I'm sure as previously been said the insurance company would wipe you in an instance (as all they look for is anything they can to not pay out while still smiling and being buddys while your paying them) and i'm sure your pax's lawyer would have a field day in suing you for compensation all because i liked it the way it was.

 

For what it takes and at no cost to you other than a small inconvenience why on earth would you not do it as the benifits far out weigh the other options

 

My 2 bobs worth.

 

Cheers

 

Alf

 

 

[Spin]

This is what was stated in the bulletin by Jab:"fitting a larger ventral fin improves the aircraft’s directional stability – the pilot’s rudder inputs are fewer and smaller in all modes of flight".

When I spoke with them this week, they stated there was two reasons 1. Directional stability needed to be improved throughout the flight modes 2. Under server testing, during full power stalls, this modification assisted in spin recovery and provided better authority.

 

Cheers

 

Vev

Thanks Vev, that explains things - I suspect part two may explain the mandatory part, as one of the earlier posters pointed out many aircraft have had new fins and strakes added, not uncommonly to address spin recovery.

 

 

[Vev]

Spin,

 

Spot on ... I had a good look at Cessna 162 Skycatcher at Oshkosh last year (2010) and they too had added a huge ventral fin along the fuselage which extend to form part of the rudder bottom ... the Cessna sale chap said it was added to assist spin recovery, following some flight test problems. Interesting to note the 162 I looked at had had a significant tail strike.... The Cessna's tail is only about 2 feet off the ground... at least the Jab has a good air gap to support the ventral.

 

Cheers

 

Vev

 

 

[Ballpoint 246niner]

I’m often amazed at the hostile reaction leveled at Jabiru when they are clearly trying to rectify an issue. In my personal experience, they have always made every attempt to support any problem I have had… I have often received free or heavily discounted parts even though my aircraft is well out of its warrantee period…. I know many manufactures would simply send one to a call centre to chat with some dispassionate person on the other side of the planet.

 

I think we should be proud of what Jab have achieved as an Australian company and recognise their drive to keep on developing and improving.

 

It’s a small family company, not a global conglomerate, who do a fine job that deserves more support … they should be congratulated for listening and offering a solution.

 

Cheers

 

Vev

Spot on Vev!!

 

 

[bushpilot]

Spin,Spot on ... I had a good look at Cessna 162 Skycatcher at Oshkosh last year (2010) and they too had added a huge ventral fin along the fuselage which extend to form part of the rudder bottom ... the Cessna sale chap said it was added to assist spin recovery, following some flight test problems. Interesting to note the 162 I looked at had had a significant tail strike.... The Cessna's tail is only about 2 feet off the ground... at least the Jab has a good air gap to support the ventral.

 

Cheers

 

Vev

Talking with a school that has fitted the mods to their J170 in last few weeks - and they have had 2 instances of ventral strike already.. Any other early experiences out there??

 

 

[pylon500]

Reading the post from the beginning, I was getting the impression Jabiru was trying to correct a crosswind handling problem and wanting better rudder authority.

 

But as I read on I find it's more to do with low speed directional stability.

 

Either way, the answer is more more vertical surface area, BUT, having more fixed area will lesson control authority as mention by SPIN.

 

One thinks the better correction would have been to produce a bigger rudder, and retro out to owners on the same swap deal (they could keep all the old rudders for the 160's).

 

A suggested correction below...

 

Arthur.

 

 

 

[Modest Pilot]

That's exactly what is about to happen. A new rudder is awaiting certification. No more flat sides. A more efficient 12% chord standard NACA airfoil. The J230 will get the same treatment if all goes well. Makes the aircraft feel nicer to fly.

 

 

[pylon500]

I get the impression the rudder on the J230 has sufficient authority with the longer tail moment, all it needs now is rudder pedals tall enough to exert enough leverage to move it, and the nosewheel.

 

Maybe independent brakes would help too?

 

While we're at it, how about an elevator big enough, and with enough throw to handle full flap when two up in the J230?

 

(Lights blue touch paper, and runs away!)

 

 

[motzartmerv]

The ventril fin is huge. Tail strikes are going to happen with great frequency. Ours has not had the mod done yet, but will be returning to the factory (at the owners expense) to have some repairs done on cracking repairs. hhmm...and will be getting the mods installed then.

 

The 170 does get 'fluffy' at slow speeds and the first axis to suffer is the longitudinal. without doubt.

 

I am no engineer so I can't comment on weather the fin will dampen that, but i would imagine it would be more prone to weathercocking, and reduce the effectiveness of the rudder, ie, you will need MORE rudder to keep it straight once it starts an excursion offline.

 

Anyway, Jabiru must have good reason to make the mod mandatory.

 

 

[Guest Pioneer200]

Motz, what are main differences between the 160 and 170 in flight?? Which do you prefer??? If one was to buy a Jab would you choose 120, 160 or 170??