Vortex Generators  - Eric Bentley

Here is an update on the approval proceedure through the Laa for the fitting of VG

 

1) At the LAAs request, John Brownlow prepared a test schedule that was accepted for the J400 and G-SAZY (owner Stuart Pink)
was offered as the "Test AIrcraft" and was re-located to Cambridge for testing.
2) John duly undertook a series of baseline flights without VGS to establish the aircrafts "clean" performance.
3) I then installed a full set of Stolspeed VGs to the wing and tailplane (underside) and duly carried out the" first flight" with John.
( I think he wanted me on-board to show I had faith in the units and was happy to put the aircraft through its paces)
Well, nothing fell off, and after some extreme "stalls" roll rate checks ,climbs,etc we returned to Cambridge
4) Over the next 4 to 6 weeks John and Stuart carried out the same schedule as the Pre-VG flights to evaluate any improvements.
5) The final report has now been accepted by the LAA showing an improvement in "roll-rate" a reduction in the "stall-speed" a general
overall "flight feel" improvement and "crispness" of control.
6) The LAA are now prepairing the documentation to accept the Stolspeed VGs as a Mod to the J400.
7) I am now starting the ball rolling to allow the ULs to have these fitted.
8) This approval has been costly however , Johns charges,Airfield charges ,Fuel charges Hangarage,Vgs etc, and without Stuarts contribution
would have cost a lot more.Many thanks Stuart.
9) I will supply these VGs to pilots once the LAA paperwork is in place along with fitting instructions and any information required.I will also fit them
If you want and assist with your inspection paperwork.
When contacting the LAA for this approval, speak to Andy Draper who has seen this through with Francis and is "up to speed" with this.
It has took some time to get here but it will be worth it if you fit them.

 

Regards Eric Bentley, Mobile 07817-874279.

 


Fitting StolSpeed Vortex Generators to a Jabiru J400

Background:
We have owned our Jabiru J400 - G-CDLS now for approaching twelve months.  During that time we have thoroughly enjoyed operating the aircraft; however, we only ever found the general handling "adequate" at best.  Additionally, can be a little on the tricky side to achieve a "greaser" of a landing if one doesn't nail the approach speed just right.  As with a number of similar types of aircraft, once the airspeed had decayed the wings seem to abruptly stop generating lift.   A few months ago we mentioned this to Eric Bentley -LAA Inspector and Jabiru guru who is based at Fishburn Airfield in County Durham.  Eric recommend that we modify our aircraft by fitting StolSpeed Vortex Generators to the wings as he claimed they would transform the aircraft's handling, especially at lower speeds.  Well of course he would make such a recommendation as it just so happens that he is the sole appointed agent forStolSpeed in the UK.  Eric recommended that we take a close look at the StolSpeed website to learn more about how a number of tiny bits of plastic, glued to your wings, can transform your aircraft.  Having undertaken our own review about the whole subject of Vortex Generators, our flying group decided we'd go ahead and ask Eric to fit some for us onto our J400.  
 
Process:
As with any repeat modification to an LAA Permit Aircraft, approval to undertake the Modification is firstly required from the LAA before any work is started.  This proved to be a very simple affair as Eric had already obtained the original "sign-off" from the LAA.  All that was required on our part was to submit a form LAA/MOD 11 to the LAA together, of course, with the fee of £22.50.  Within a few days the LAA had issued a Permit Flight Release Certificate, this gave us the OK to have the Vortex Generators fitted to G-CDLS and then commence a rigorous Flight Test Schedule.

A quick call to Eric secured a slot in his busy work schedule and within a few days G-LS was over at Fishburn (we are based atKirkbride, Cumbria) ready for Eric to complete the work.  We also asked Eric to undertake all the fight testing for us in addition to supply & fitting of the Vortex Generators.
 
After a couple of weeks had passed with very poor flying conditions, we received at call from Eric to let us know all had been completed.  Within a day or so the LAA Modification Approval landed on the doormat courtesy of Royal Mail first-class post.  We were "up & running".
 
Conclusion:
Well, what can we say? - to state that we are impressed with the improvements in flight characteristics would be an understatement - the changes to how the aircraft handles are, in many respects, substantial but yet in some ways are very subtle.
 
Between us as a group of pilots we have already experienced shorter take-off distances, sharper handling in turns - particularly roll - and a landing flare that was far too high yet resulted in a "greaser" of a touch down.  Elevator authority remains even down to the lowest of air speeds and likewise the the wings do continue to fly at these low air speeds.  One of our flying Group even reckons that it is now impossible to stall the aircraft.  We're sure he isn't 100% correct in his observation; however, he's certainly not far from the mark.  Another Group Member has described the handling as though "she is now on rails".  Undoubtedly the wings do continue to generate lift all the way through to the touch down stage of the landing, whereas prior to our having the Vortex Generators fitted the wings would slow down to a point where they stopped flying and then produce a "thump" of a landing.

It's still early days and we have more exploration to do as we progress through all aspects of the flight envelope; however, our flyingGroup are already converts to the benefits of modifying the the aircraft by fitting the StolSpeed Vortex Generators.

Recommendation:
We would wholeheartedly recommend that all J400 owners seriously consider contacting Eric Bentley at Fishburn and arrange to have this modification completed as soon as possible as they will certainly not regret it.
 
It won't make a fully laden J400  (three adults & full tanks) into the ultimate STOL aircraft but it will take it heck of a long way towards it.
 
Given the cost we have occurred and what we have experienced so far, would we have them fitted again?  - You bet we would - it's a "no-brainer" !  
Anyone interested in fitting StolSpeed Vortex Generators to their own J400 can contact Eric Bentley on 07817874279 and anyone wanting to discuss our own personal experiences further can contact me on 07715 477 043 or  via email   gcdls@btinternet.com

Tony Haslam 
Kestrel Group - Jabiru J400 - G-CDLS
23rd June 2012