Jabiru 450 ul. Vortex generators

[Greg Stokes]

Has anyone fitted these VG's to their own Jabiru as a mod?

http://www.pnwaero.com/Jabiru.htm


Greg

[Greg Stokes]

According to http://www.pnwaero.com/benefits_of_vgs.htm there seem to be other things to consider too. Just wondered if they live up to their other claims of improvements, especially in low-speed aileron control and short field performance.

Greg

[Brian Hope]

Hi Greg, reports that I have read suggest that there are some improvements. In UK I know of only Silver Fern Microlights (Mike Moulai) that have fitted them to a Kolb and the guys that sell the Savannah who have (legally) tried them. There may well be others though. Might be worth talking to them to see whether they found the improvements worthwhile and whether there were any disadvantages.
You will need LAA approval if you want to put them on your Jab.

[Bill McCarthy]

The GASIL safety suppliment had in the past been littered with Jabiru incidents (only one in the latest) with almost all on landing and collapse of the nose gear. Since the ailerons on the Jab are not much bigger than a couple of A4 sheets of paper I would have thought that anything that would improve slow speed handling - especially crosswind landings, would be of benefit to the type, or indeed any type. If there was significant safety improvement gained by fitting them at the loss of two knots cruise speed, I would not hesitate to seek approval.

[Greg Stokes]

I know that VG's improve the Savannah to the extent that on the latest models, the leading edge slats are no longer fitted. That was my first choice of aircraft when I decided to go back to 3 axis flying but couldn't find a ready built one which was within my budget. I'm still doing my type conversion on the Jab and like it but comparing it to the C152/C172's that I used to fly, the Jab's slow speed control isn't as positive. The orientation of our strip usually means a crosswind landing.

Again, according to http://www.pnwaero.com/Pre-Tested%20Kits.htm they've already been tested on a Jab in America and are supplied with full fitting instructions. (Google also finds some Aussie Jabs with VG's fitted.) I was just hoping someone had already gained LAA approval, fitted them, could give me feedback and that it would be treated as a series mod.

[Greg Stokes]

The GASIL safety suppliment had in the past been littered with Jabiru incidents (only one in the latest) with almost all on landing and collapse of the nose gear. Since the ailerons on the Jab are not much bigger than a couple of A4 sheets of paper I would have thought that anything that would improve slow speed handling - especially crosswind landings, would be of benefit to the type, or indeed any type. If there was significant safety improvement gained by fitting them at the loss of two knots cruise speed, I would not hesitate to seek approval.

Couldn't agree more Bill. I'm a newbie to the LAA so I'm dipping my toes into the water at the moment.
If no-one else has gained approval for this mod and I can find proof that its worthwhile, I would consider applying for it.
What's involved and would I need the wealth of Solomon and the lifespan of Methuselah to see it through?

Greg

[Bill McCarthy]

Greg, I would make initial telephone contact with the engineering dept at the LAA - e.mail enquiries seem to disappear into a black hole. They should be able to tell you if VGs have already been fitted to type and the way to proceed with it.

[Greg Stokes]

Thanks for your replies.

After watching http://www.youtube.com/watch?v=YQO7SoULc3U
I'll give our engineering dept a call.

Greg

[Clive]

Further up this string we have Bill suggesting that all the nosewheel collapses are caused by small ailerons on Jabiru's, or is that not what you are saying Bill? Bit of a sweeping statements, you have much experience of the type?

The earlier mark Jabiru aircraft has a weak point with the nose leg. True, though treated correctly it is strong enough.

The Jabiru aircraft needs careful conversion to as it is not like conventional aircraft in some respects. That is in fact what type conversion is about of course.
Many 'instructors' need converting to the Jab before they can teach on it.
Speed handling, to preserve control is like all aircraft, something that needs careful monitoring on final part of an approach and landing.

Greg, VG's interesting idea but as someone who has flown all the Jabiru aircraft I don't see the need to fit stick on tabs to improve the Jabiru.

Get to know the plane, play around with it's capabilities and you'll find it doesn't need any tweaks.

Bill mentioned the small ailerons, they are small but they are of sufficient size. That is because the Jabiru also uses the rudder to turn, pick up a wing etc. Learn to fly your Jabiru using a combination of stick and rudder and you'll be fine with it (well rudder and stick actually).

Respect the fact it cannot be landed on it's nosewheel and it develop your landing style such that you always hold the nosewheel up until you are ready to use it (not so easy on some 400s but they have stonking great noselegs).

For those who maybe reading this and forming an opinion on Jabiru's I hope I have added some support to the Brand, it's not perfect but it's not as Bill suggests appearing in the reports continually because it's a flawed aircraft.

Nose leg collapses on the Jabiru are caused by aircraft handling.

I do agree the legs could have been stronger, as Jabiru did as they changed the legs and now all newer aircraft have a stronger type. The old ones are still fine just recognise the fact they need flying properly and while forgiving in loads of areas, smacking down the noseleg of a Jabiru on landing is not one of them.

Regards, Clive

[Bill McCarthy]

Clive, I certainly am NOT suggesting that its a "flawed" aircraft - if I could afford one I'd have one like a shot ! I was simply suggesting that anything that would improve safety and slow speed handling are big pluses in my estimation, therefore since landings are slow speed manoeuvres, they should be of benefit - to ANY aircraft. Now, where did you read that I lambasted the type.

[Brian Hope]

Jabiru deliberately designed the nose and main gear legs to break away in the event of an accident rather than cause damage to the composite monocoque fuselage. There were however, a larger than acceptable number of gear collapses in the UK, whether that was as a result of our rough strips or simply poor technique you can make up your own minds about. Fact is that ideally an aeroplane should be able to take a reasonable amount of abuse as there will always be pilots who lack finesse, or simply have an off day. When LAA's chief engineer, Francis Donaldson visited the factory in Aus he raised the issue with them and it was agreed to strengthen the attachments up a bit.
Clive, I'm all for defending your aircraft, I'm the same with the Jodel, but if improvements can be shown to be possible, then why not fit them? For instance the Jodels were fitted with a small stall strip on the inboard leading edges some years after they left the factory because there was pretty nigh no pre-stall buffet and I guess there must have been a few stalling or landing accidents. By your reckoning this should not have happened, pilots flying Jodels should all have been careful not to let the speed decay below 1.3S, and no doubt most of them did, but.... The theory's great but practice is somewhat different.
I'm definitely not saying anything against Jab, they are great little aeroplanes. We had a 450UL on our strip and the owner and his wife used to fly it all over the place. After about 900 trouble free hours they sold it and built a 430 so they can take more baggage with them.

[gasax]

There are none so blind as those who will not see!

I own and fly a Zenith 601xl - subject to a number of accidents and compulsory LAA (and if you are elsewhere other mods).

Far too much of Clive's reponse smacks of the ill - informed comment from zenith owners prior to the fairly major compulsory mods to the xl.

One of my frineds built a Jabiru, he sold it on, not being very enamoured with it. Which is not to say there is a particular problem. But I am acutely aware that if the accident rate for any particular aspect is higher than expected - it is higher likely there is an engineering issue.

Pilot issues are a smoke screen - either the Jabiur is horribly dangerous (pretty unlikely) or there are issues with a 'weak' undercarriage and possible the low speed handling.

Passion is great in its place - but not in engineering issues.

I've seen vortex generators in action and frankly they have near magical qualities. Speed losses are pretty small but the low speed gains in terms of controllability and lack of stall are staggering.

Try a Super Cub with them and they literally only stall at ludicrous angles - and even then the controls still work! Fly at speeds where the ASI almost does not indicate. On an aircraft like the Jabiru I suspect they would make it float and fly - rather than clunk out of the sky.