World Record Plane - 12 years on

[Robin Austin]

Hi Folks

I’m not a regular reader or contributor these days (bit lazy) but since I put this brief report of my current aircraft together for a local group (here in Australia), I thought it may be of interest here on this original Sonerai group too.

SERA-173 (VH SRS) is the 3rd aircraft in my journey (following the world record VH-SGS) of developing evolutionary aircrafts originally based on the 1970 Monnett Sonerai II design.

Put simply, the aim this time round was to build the smallest achievable plane outside in conjunction with the largest achievable plane inside, all with performance exceeding VH-SGS. How hard could that be????? ha ha!

The resulting SRS is likely the first Rotax 912 aircraft capable of carrying 2 large adults whilst achieving genuine RV series performance. In saying that, I’d be happy to be told if in fact there are others (with verifiable performance).

Although maintaining Sonerai heritage, SRS is considered sufficiently divergent from the original Sonerai design to warrant a new name, hence the SERA-173 (Stands for Sonerai -Evolution -Robin -Austin - 173 knots max cont. cruise speed)

Broadly speaking the SERA 173 specs and differences from a
standard Sonerai 2 are as follows (all specs solo).

• Max continuous cruise speed 173 Kts
• All day everyday cruise speed 165 Kts (24”/4800rpm)
• Economy cruise - 160 Kt at 15.2 L/hr
• Aerobatic +6G -5G
• VNE 180Kts (testing included full range flutter testing up to and including 200Kts)
• 300Kg empty - 600KG MTOW – 300Kg payload
• RV10 cockpit dimensions - comfortable for 6’5” pilot, 6’2” PAX (Sonerai volume +67%)
• Centreline flying from front seat
• High strength crash resistant zone around pilot (2.5X FAR23 requirements)
• Airframe structural strength = Sonerai +25%
• Airframe efficiency = Sonerai +72%
• Stall speed slightly less than Sonerai II (minimum solo 39Kts)
• 1250 NM range at 160 Kts
• 1700 NM range at 100 Kts
• Also comfortable at 70 or 80 Kt “loitering” speed
• Constant speed propeller with latest Sensenich high speed blades
• 23” prop clearance for gravel strips
• Full span (30 degrees deployment) electric flaperons
• Horizontal Stabiliser - electric inflight adjustable
• Rotax 912 reliability and operating costs
  
  Although now flying for 150 hrs over 3 years, SRS is still “work in progress” hence the temporary SERA 168 logo (which was based on the original design cruise speed).
  SRS also features 1-person-easy-folding wings to minimize hangar space requirements, or in this case negates the need for a hangar as its current home is a custom built, generous sized, air-conditioned enclosed trailer (See photos attached) which doubles as a hangar and workshop and lives at home right outside my garage (I can play with my toy anytime!)
  This design, construct and refinement project (including trailer) has taken 8 (enjoyable) years, and development continues.
  Hoping this provides an interesting read to those more technical members and those interested in performance aircrafts.
  Regards
  Robin

 

[Robin Austin]

Sorry about the formatting, my typing machine froze. Anyway, here are some pics of the "new" SRS.
Robin

 

[eschrom]

Absolutely stunning! Congratulations, Robin! Can you tell us *how* you achieved such enviable performance? Also, why did you pick a Rotax over a Jabiru? I would have expected the latter to be less expensive in your neck of the woods.

Truly impressed,
Ed

 

[Robin Austin]

Thx Ed. Appreciated.
Re the how to. I took 3 years to write this up and I expect it would take me 20 years to answer your question at that rate. Ha ha. I would need to write a book and I don’t do too well at this stuff.
However to answer your question a bit, it’s just about methodical (anal?) attention to detail and drag reduction.
Every time air expands, contracts or changes direction, particularly suddenly, it creates drag. So it really is just about uncompromisingly detecting and quantifying this in as many places as you can and figuring out how to reduce these effects. I know that may sound vague but that’s really most of it.
So to start with an accurate, light, straight build is important. But equally, challenging every point of drag and improving where necessary or possible is equally important. Big areas are engine bay (huge), particularly getting the cooling air to accelerate and join seamlessly as it exits. Also, rigging and trim (minimising trim drag).
The way air exits any protrusion seems substantially more important than where it enters or hits it
So without sounding evasive, this would need to turn into a VERY long answer to answer your question comprehensively.
Re a Jabiru vs Rotax. Over the last 30+ years, I‘m having trouble recalling seeing a single 912 series engine that was installed, maintained and flown according to the manuals, fail due to its own integrity, ie excluding fuel starvation etc. I lost count 20 years ago of the number of Jabirus that had failed under same criteria. I know, it doesn’t sound patriotic, but my brain works with facts, not myths. Sorry Mr Jabiru, I just say it as I see it.
Hopefully Ed, that fills in a couple of gaps although I know it doesn’t answer your question fully.
Regards
Robin

 

[Robin Austin]

Sorry, this post was a duplicate but I can’t seem to delete it.

 

[Robin Austin]

And just for laughs.
if you ever watched the film “San Andreas” with Dwayne the rock Johnson, you will have seen small airport scenes. The hangars in the background at our local club airfield in the pics are the hangars in that film. In fact some of the sign writing is still visible on the hangars.
And those massive cracks in the San Andreas ground were just near here too. If you’re sharp you’ll see that all the trees in the film are native Australian Eucalyptus.
But as they say, that’s Hollywood!
cheers
Robin

 

[Robin Austin]

Hi again Ed ( or the moderator should they be reading this).
Just curious whether I’ve re-registered correctly as I notice that none of my posts are appearing in the new posts tab, new profile posts tab, or my daily email activity notification.
It may be as they are my posts? Can I ask if they are appearing there on your browser?
Thx
Robin

 

[soneraifred]

i can see your posts.

 

[eschrom]

I can see them too. Thanks, Robin. If you have any close-up photos of the details you describe, particularly the engine bay, I'd love to see them. My 2LS is just a stock, 140 mph, VW powered airplane but the prospect of making it go faster without adding power is intriguing.

Ed

 

[Robin Austin]

Thx Fred. Great to see you’re still there. I was intending to catch you at Oshkosh this year, but maybe next!

Hi Ed. Actually there’s not much to see in the engine bay yet. This aircraft’s performance is mainly from what’s visible outside. I haven’t really started under the cowls except for the initial build placement of the radiators and their inlet ducting. The radiators are large so that the air flow can be slow with less resulting friction. There are some other things, like the careful placement of the Rotax muffler to guide and accelerate the cooling air towards the exit. I guess that’s like the rest of the plane, the things that make it low drag are not really visible or obvious unless you actually know why they’re there. The whole fuselage is redesigned profile wise. There are no sharp changes in angles. Both sides and bottom are 1 continuous curve from front to back. (It is 3” wider than std Sonerai 2. In fact the aircraft is 1’ taller than a standard Sonerai and the canopy is, as I recall, 18 or 19” longer).
Panel alignment, gaps, including spinner gap to prevent leakage were all concentrated on.
There are small carbon composite ribs in between every wing rib to help keep more accurate wing section in flight.
All rivets are filled to a high standard (shape and surface finish) both top and bottom such that the wings can’t be visually differentiated from composite wings. I have altered the wing section ( sorry, 1 of a kind trade secret here).
Exhaust outlet tapered to optimise balance between HP loss and actually producing thrust. Also angled to minimise exit turbulence whilst assisting thrust and oval section to minimise drag.
Aileron trailing edges are special shape to reduce drag ( I’ll follow with a photo at some stage).
Spats are 1 of a kind but are effectively a custom and modified mid sized Vans pressure recovery that covers almost all of wheel. All fitted with extreme care to alignment and blended to low drag integrated fairings.
Gear legs are aluminium but are hand tapered in both planes ( they get progressively thinner towards the wheels). They are also then (hand) finished to an airfoil shape. Finally, they are wrapped in glass, then have carbon trailing edges added so they taper in section to a thin trailing edge. Fully enclosed brake lines. They would present really minimal drag.
ContInued soon.

 

[Robin Austin]

Continued.
Hard to know where to start and where to stop.
Other areas include intersection or interference drag reduction wherever practical, and importantly, rigging. Ground adjustable wing incidence (left and right separately), HS incidence adjustment inflight electric, and Incremental aileron reflex, once again in flight electric. There are infinite combinations of these 3 that all provide stabilised straight and level flight. To get the best combination, extensive, accurate, repeatable and methodical testing is required. I will try to upload my testing technique as an attachment soon. It’s quite lengthy but this sort of rigour is absolutely required so that repeatable testing outcomes result. These tests must be able to differentiate 1/4 knot, or as an absolute minimum 1/2 knot changes, otherwise improvement cannot be positively identified.
Phew. No wonder I’m tired! OK, time to relax in front of tv and then sleep.
Hope some of this is informative or a bit interesting.
Regards
Robin

 

[Bil4381]

MY sIILS IS POWERED BY A Jabiru 3300, solid lifter engine. I've had no issues with it thus far. Admittedly i did a great deal of work to ensure optimum cylinder cooling and oil temperature control. Also my prop allows me to run it at 3300rpm in fast cruise. Indication shows 180 kts. I bought it because it has 7 main crankshaft bearings and real propeller and flywheel thrust bearings.
My close friend had a Europa XS with a Rotax 912. He lost power over the Laurentian Mountains and crash landed beside lac Minerve. It took 2 weeks to get it "off the Mountain" . Upon inspection the fuel had boiled in the lines, because the exhaust has come adrift at the heads. Also one of the ign coils was cooked. I felt that the installation hardware the Rotax dealer had sold him was deficient. The stud nuts had no self retention feature. I also believe the dealer had seen the installation yet said nothing. I made him fix or modify about 30 defects I found. My friend then sold the aircraft at 1/4 of what it cost hom to build.
I'm an AME and aircraft inspector as well as glider and commercial pilot. Nearly 50 years as both.
in short my life is worth enough that I'd never put myself behind a rotax engine.

Thx Ed. Appreciated.
Re the how to. I took 3 years to write this up and I expect it would take me 20 years to answer your question at that rate. Ha ha. I would need to write a book and I don’t do too well at this stuff.
However to answer your question a bit, it’s just about methodical (anal?) attention to detail and drag reduction.
Every time air expands, contracts or changes direction, particularly suddenly, it creates drag. So it really is just about uncompromisingly detecting and quantifying this in as many places as you can and figuring out how to reduce these effects. I know that may sound vague but that’s really most of it.
So to start with an accurate, light, straight build is important. But equally, challenging every point of drag and improving where necessary or possible is equally important. Big areas are engine bay (huge), particularly getting the cooling air to accelerate and join seamlessly as it exits. Also, rigging and trim (minimising trim drag).
The way air exits any protrusion seems substantially more important than where it enters or hits it
So without sounding evasive, this would need to turn into a VERY long answer to answer your question comprehensively.
Re a Jabiru vs Rotax. Over the last 30+ years, I‘m having trouble recalling seeing a single 912 series engine that was installed, maintained and flown according to the manuals, fail due to its own integrity, ie excluding fuel starvation etc. I lost count 20 years ago of the number of Jabirus that had failed under same criteria. I know, it doesn’t sound patriotic, but my brain works with facts, not myths. Sorry Mr Jabiru, I just say it as I see it.
Hopefully Ed, that fills in a couple of gaps although I know it doesn’t answer your question fully.
Regards
Robin
[/QUOTE]

 

[CdnMedic]

Happy to see you post up here. Seeing your records proved what a "Sonerai" could do and helped seal the deal on me building one. I looked at what info I could find on SGS for some inspiration, and have really enjoyed watching Mike Arnold's videos on youtube in hopes of bringing some of those thoughts and techniques in to my build.

My biggest question, is how you managed to have solo up front capability. It is my biggest hang up about the aircraft. I'm assuming it involves increasing cord and some fuselage lengthening. I'm a shorter guy so I'm not overly concerned for leg room.
It's a big enough hang up for me I almost waited for the SPA Cougar to be released, but it wouldn't be able to use my preferred engine.
I'm still very early in my build (ribs so far).

I'm planning on a Yamaha Apex set up, but a 912 is also a possibility for me. The Yamaha set ups are really getting popular and where I am I can get a great motor for cheap. I know those motors are tough, and the gear box has been out a couple years now with zero catastrophic failures.

 

[tls258]

Robin-

It's a clean and lean machine. Beautiful. Any pics of the interior and engine setup you might share? Where would it fit in the lineup? 2LS+? Are you exploring going into business with J Monnett with this "new and improved" version of the stalwart Sonerai, or would this be too much competition for the Sonex?? How are you handling the aft CG when some lard butt pax sits in back? That seems to be a tricky question for the RV-4 crowd with some opting for no passenger due to handling uncertainty. Isn't it a lot less complicated to put the pax on the center of the Hershey bar so W&B vectors do not change? If visibility is a question, why not install a camera and drive by wire?
T

 

[Aviacs]

In fact the aircraft is 1’ taller than a standard Sonerai and the canopy is, as I recall, 18 or 19” longer).

I have delayed progress on my purchased S2 due to a number of factors, primary being that canopy height needs increased by about 3" for me to fit. (Obviously known at point of purchase, airplane had a number of added features that made it the best value at the time). So my question is what if any changes did you make to the vertical stab & rudder dimensions compared to stock plans? And would you change anything about that area after the accumulated flying time?

Thank you!

 

[Robin Austin]

MY sIILS IS POWERED BY A Jabiru 3300, solid lifter engine. I've had no issues with it thus far. Admittedly i did a great deal of work to ensure optimum cylinder cooling and oil temperature control. Also my prop allows me to run it at 3300rpm in fast cruise. Indication shows 180 kts. I bought it because it has 7 main crankshaft bearings and real propeller and flywheel thrust bearings.
My close friend had a Europa XS with a Rotax 912. He lost power over the Laurentian Mountains and crash landed beside lac Minerve. It took 2 weeks to get it "off the Mountain" . Upon inspection the fuel had boiled in the lines, because the exhaust has come adrift at the heads. Also one of the ign coils was cooked. I felt that the installation hardware the Rotax dealer had sold him was deficient. The stud nuts had no self retention feature. I also believe the dealer had seen the installation yet said nothing. I made him fix or modify about 30 defects I found. My friend then sold the aircraft at 1/4 of what it cost hom to build.
I'm an AME and aircraft inspector as well as glider and commercial pilot. Nearly 50 years as both.
in short my life is worth enough that I'd never put myself behind a rotax engine.

Thx Ed. Appreciated.
Re the how to. I took 3 years to write this up and I expect it would take me 20 years to answer your question at that rate. Ha ha. I would need to write a book and I don’t do too well at this stuff.
However to answer your question a bit, it’s just about methodical (anal?) attention to detail and drag reduction.
Every time air expands, contracts or changes direction, particularly suddenly, it creates drag. So it really is just about uncompromisingly detecting and quantifying this in as many places as you can and figuring out how to reduce these effects. I know that may sound vague but that’s really most of it.
So to start with an accurate, light, straight build is important. But equally, challenging every point of drag and improving where necessary or possible is equally important. Big areas are engine bay (huge), particularly getting the cooling air to accelerate and join seamlessly as it exits. Also, rigging and trim (minimising trim drag).
The way air exits any protrusion seems substantially more important than where it enters or hits it
So without sounding evasive, this would need to turn into a VERY long answer to answer your question comprehensively.
Re a Jabiru vs Rotax. Over the last 30+ years, I‘m having trouble recalling seeing a single 912 series engine that was installed, maintained and flown according to the manuals, fail due to its own integrity, ie excluding fuel starvation etc. I lost count 20 years ago of the number of Jabirus that had failed under same criteria. I know, it doesn’t sound patriotic, but my brain works with facts, not myths. Sorry Mr Jabiru, I just say it as I see it.
Hopefully Ed, that fills in a couple of gaps although I know it doesn’t answer your question fully.
Regards
Robin

[/QUOTE]


Hi Bil.
Great to hear your Jab engine is going so well. I wasn’t trying to get into a Jab vs Rotax discussion, just answering a direct question based on my personal observations. But that’s the great thing about these forums, we get to hear from lots of different experiences.
Rotax exhaust kits are carefully designed such that if you hang them below the engine perpendicular to the crank, and don’t change the location of any of the 4 muffler inputs, it just moves around with all the thermal expansion without undue stresses. If you relocate 1 or more inlets or make other changes, the installation needs a slip joint on 1 pipe or it will eventually fail. Not sure if that was the case there.
I think we might be on the same page somewhat though in that the Rotax engine itself Seemed to remain a functional unit, despite it stopping due to fuel starvation? Or am I misunderstanding?
It seems that Jab engines are better regarded in US than here. This may be cause they weren’t released into the US for the first 10 or 15 years, after they improved their reliability substantially, which is a good news story. That’s not so say that there are not lots of happy Jab owners here, there are, but I was just relating my observations as truthful as I could, and strictly on those observations and without allowing personal bias.
On that, perhaps you may comment, and others might chime in here too, how many Jab engines are you aware of that have reached TBO without moderate or major internal intervention? Sadly, I’m not aware of any although I’m sure there would be, but hopefully after this I’ll hear of a flood of them, which would be good.
Finally, I’m not trying to trash our local product or economy, just conveying 1 persons experience.
Just before I sign off, your final comment re Rotaxes, is that based on seeing or hearing first hand of verified engine failures, not fuel starvation or the like? I ask this cause it’s in direct contrast to my experiences and I’m genuinely interested if I’m missing something. I’ve built or owned roughly as many planes with new Lycomings as Rotax 912s ( carburettor type) and have also had repair and rebuild authority but only for 20 years less than you, and perhaps not as high level as yours, but would find it hard to argue that properly installed Rotaxes are less reliable than traditional aero engines.
Not trying to get in the middle of that argument either, ha ha. Just like to continue learning.
Cheers
Robin

 

[Robin Austin]

H

Happy to see you post up here. Seeing your records proved what a "Sonerai" could do and helped seal the deal on me building one. I looked at what info I could find on SGS for some inspiration, and have really enjoyed watching Mike Arnold's videos on youtube in hopes of bringing some of those thoughts and techniques in to my build.

My biggest question, is how you managed to have solo up front capability. It is my biggest hang up about the aircraft. I'm assuming it involves increasing cord and some fuselage lengthening. I'm a shorter guy so I'm not overly concerned for leg room.
It's a big enough hang up for me I almost waited for the SPA Cougar to be released, but it wouldn't be able to use my preferred engine.
I'm still very early in my build (ribs so far).

I'm planning on a Yamaha Apex set up, but a 912 is also a possibility for me. The Yamaha set ups are really getting popular and where I am I can get a great motor for cheap. I know those motors are tough, and the gear box has been out a couple years now with zero catastrophic failures.

Hi WTR
Re the front seat flying.
Few issues,
Engine installation is quite light, although prop hub is relatively heavy by LSA standards, but appropriately built to last the distance when compared to traditional CS props.
Engine is as far back as I could put it. Firewall is tapered to allow carbs rearward while pedals remain fwd.
I have 100% mass balancing on tail surfaces and electric HS trim which cumulatively adds about 6 lbs or so Plus with a long moment arm.
Main tank is well behind rear seat (42 litres), installed as per FAR23 requirements.
And the key, 20 litre tank up front in std position. This tank is only used when carrying a PAX. I can transfer 20 litres from rear tank during warm up and taxi. All fuel ( including 2 x 30 litre wing touring tanks) all transfer to the main tank so no confusion. Engine only ever draws through a single tap from main tank.
Battery behind rear seat.
Baggage up front above 20 litre tank and behind rear seat allows more flexibility.
That’s about it. This allows carrying most any combinations of pilot and Pax that could be reasonably expected ( typically about 120 Kg from memory in either seat.
Sorry, short answer became long answer!
Cheers
Robin

 

[Robin Austin]

Robin-

It's a clean and lean machine. Beautiful. Any pics of the interior and engine setup you might share? Where would it fit in the lineup? 2LS+? Are you exploring going into business with J Monnett with this "new and improved" version of the stalwart Sonerai, or would this be too much competition for the Sonex?? How are you handling the aft CG when some lard butt pax sits in back? That seems to be a tricky question for the RV-4 crowd with some opting for no passenger due to handling uncertainty. Isn't it a lot less complicated to put the pax on the center of the Hershey bar so W&B vectors do not change? If visibility is a question, why not install a camera and drive by wire?
T
View attachment 15185

Hi T
Thanks for the kind comments. Appreciated.
No pics of interior or engine bay for a while. Unfortunately neither of those are finished. I‘m pretty slow nowadays and don’t feel comfortable publishing half finished work. Sorry, but that’s just a personal thing. Some of these areas would look a bit rough to those that don’t understand developmental projects. This is important to me as when I finish a project, I try to achieve as close to a concourse finish as I can, but I also like flying too along the journey and it can’t all happen at once.
Funny, I camped next to my plane at a major flyin. Cowls were all in primer tinted a shade of poorly matching white. Finish was #40 grit. Whilst laying in tent, I heard several unsuspecting commentators criticising the paint finish. Just a laughable example but hopefully enough said.
Where does it fit? Well outside it’s not that much bigger overall than 2LS although it is 1’ taller, but inside it’s seating dimensions are RV7+ in front and RV7- in rear. Actually it’s the same as RV10 split down the centre. Bit similar in front seat to your RV4 but way more legroom. Not that you need it. I’m 6’ 1 1/2” and using second set of (touring) rudder pedals, my legs are stretched out straight. You decide ha ha. I’m confused!
And you’re right, flying from rear seat is probably easier but I’ve done 600 hrs looking at the back of a mates head, And without being disrespectful, the view from the front seat now is WAY better!!!
Cheers
Robin

 

[CdnMedic]

H



Hi WTR
Re the front seat flying.
Few issues,
Engine installation is quite light, although prop hub is relatively heavy by LSA standards, but appropriately built to last the distance when compared to traditional CS props.
Engine is as far back as I could put it. Firewall is tapered to allow carbs rearward while pedals remain fwd.
I have 100% mass balancing on tail surfaces and electric HS trim which cumulatively adds about 6 lbs or so Plus with a long moment arm.
Main tank is well behind rear seat (42 litres), installed as per FAR23 requirements.
And the key, 20 litre tank up front in std position. This tank is only used when carrying a PAX. I can transfer 20 litres from rear tank during warm up and taxi. All fuel ( including 2 x 30 litre wing touring tanks) all transfer to the main tank so no confusion. Engine only ever draws through a single tap from main tank.
Battery behind rear seat.
Baggage up front above 20 litre tank and behind rear seat allows more flexibility.
That’s about it. This allows carrying most any combinations of pilot and Pax that could be reasonably expected ( typically about 120 Kg from memory in either seat.
Sorry, short answer became long answer!
Cheers
Robin

Lots to think about. Maybe a stretch would have been a better set of plans for me to purchase in order to do a set up like that.

You really got me thinking there. The Apex is a longer set up than the Rotax so it would already be packed tight to the firewall. Was planning to indent the firewall to make room for the coolant or oil tanks.

I guess once I have the fuselage "done" and the engine installed and wings bolted up I can start messing around with placement of fuel tanks and see if I can come up with something similar and still balance out in all configs.

 

[Robin Austin]

Rule of thum is whatever you add to the

I have delayed progress on my purchased S2 due to a number of factors, primary being that canopy height needs increased by about 3" for me to fit. (Obviously known at point of purchase, airplane had a number of added features that made it the best value at the time). So my question is what if any changes did you make to the vertical stab & rudder dimensions compared to stock plans? And would you change anything about that area after the accumulated flying time?

Thank you!

Rule of thumb is whatever you add to canopy height, add the same to rudder height. And for conservative safety (at least I did), strengthen VS main spar appropriately, although my calculations show that this MAY be unnecessary.
That’s all you need to do on a retrofit like yours.

On top of that, for a new build to make a better “overall flyer”, I added 5” HS span and 2” to chord of elevators. Although this was done mainly due to aggressive use of flaperons.

And about +22% to chord of vertical stabiliser.

That all being done, I probably wouldn’t make any further changes.

Cheers
Robin