Sonex High Wing!

[Skippydiesel]

Bryan/Scott

In Australia, the builder can nominate the MTOW, however I am not an engineer (farmer)

Either of you guys wish to comment?

Not either of the guys.............but isn't this the same airplane that the original builder thought, amongst many other things, that he knew better than the designer and that he needed to and, in fact, did change the angle of incidence of the wing? This is one of those airplanes that John Monnett would say "please don't call it a Sonex". Not meaning to offend you, but personally I would have passed on this purchase. Depending on what was or what is the actual desired mission of the original builder or yourself, there must have been a better alternative out there. Just my opinion.

Art,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,Jabiru 3300 #261

No offence taken.

I did have it checked out by an aircraft engineer - he was very complimentary regarding the quality of the build and saw no potential problem(s) with the 1.5 degree change in the wing, angle of attack/incidence. The aircraft flies and handels normally, has tested good for the designed stall of 40 Kn (flaps MTOW) & 150 Kn (true) high speed cruise 5450 rpm @ 5500 ft.

Don't know the original builders intended mission but given the extra fuel capacity & the CS prop, would suggest the same as mine - long distance touring.

Alternatives/price range - I focused on finding a Europa XS/Rotax 912ULS - over two years, came close twice - no deal! Then Sonex came out of the blue - if you look past the fuselage construction, many similarities - so I purchased it.

As far as Mr Monnett - I would guess that every home build, has some degree of customisation/personalisation. Could be as small/insignificant as the paint job, right up a major change like a much larger engine. Lets face it Mr Monnett was no fan of the Rotax 9 range, so I am not surprised that he would disown anything outside his original concept.

[Skippydiesel]

My own polished Sonex Legacy dual stick tailwheel has fairly frugal instrumentation including a 40 l seat back auxiliary fuel tank, 5.00 tyres, an Icom 200 and a mode C transponder. With the Edge 915 ECI including oil and coolant, it puts 680 lbs on the scales. It was not always like that: it started out very basic with the small Shinn tyres and a Jab 22A, but no auxiliary tank. The result was 618 lbs. This only shows that you need to be extremely careful when you start loading on the goodies. The sword above your head are always those 1150 punds.

So true.

I think if I had not purchased a Sonex with wing tanks, the back of the seat Aux fuel tank idea has a lot of merit. Likely lighter/litre capacity, than 2x 30 L wing tanks + plumbing/valves/sensors/etc & a simpler fuel transfer system - what's not to like?

Probably hoping for divine intervention however, I am seriously considering having my Sonex reweighed - I just can't get my head around its current empty weight.

[Kai]

My seatback tank contains only 40l- however, I can´t recall I have ever topped it off (in case my CG calcs might be slightly on the optimistic side). I have done some flying out of Alice and Toowoomba- the flying we do up here is not totally unlike Down Under, while our distances are shorter we are often up in the mountains and experience local weather dramatically different from forecasts and a total nogo up front. The idea of not having anough fuel to turn around and return home, is a show stopper, and an off field landing would surely put a lid on everything! We seldom plan for more than 3 hours flight, for which the Edge would require something slightly short of 50l. Then we have the mandatory reserve-we don´t feel that 40l is too much: but of course no luggage back there! In short it works, but it is not ideal.

[Skippydiesel]

Scott/Bryan,

You have both made some good points, regarding Sonex MTOW increase but somehow I feel you have not followed up with the rest of your argument.

Given that this aircraft is designed to put up with the stresses imposed by amateur aerobatics:

How can a plus 78 kg ( 600 kg) MTOW be of any concern, when the aircraft is flown in the "Utility" configuration. and assuming it has been loaded within CG considerations ??
The engine/prop are certainly able to deliver sufficient thrust for TO & sustained flight (check out all the other Rotax 9 powered aircraft).
As unrecarrages are constructed, with considerable overcapacity, specifically to withstand the occasional botched landing, can it not be assumed that a mere increase of 78 KG can be accomodated??

What remains is the ability of the aircraft to fly at this higher weight - will the lifting surfaces be sufficient, at a high density altitude, to achieve/sustained controlled flight ??

[Bryan Cotton]

That's beyond my current skill level and bandwidth to analyze. I'd say the burden is on the person who wants to exceed the GW to prove it's good, rather than the person who thinks the manufacturer's GW is a good limit.

[Kai]

When this new 600 kg MTOM for the new sports class came up un Europe, all aircraft owners deluged the manufacturers with requests for raised weights. I was lucky enough to get in touch with Kerry. The essence in his reply was that they did not know- it had never been tested (apart from the static spar loading). It might be possible, but he asked me to bear in mind that the factory limit was by no means only structural. Flight performance also came into it- takeoff, glide ratio, landing characteristics, to mention a few. Tongue in cheek he informed me that Sonex was in no way unwilling to set up a test program to find out, as long as someone else footed the bill. We left it at that. I miss Kerry- he was great!

[Murray Parr]

My own polished Sonex Legacy dual stick tailwheel has fairly frugal instrumentation including a 40 l seat back auxiliary fuel tank, 5.00 tyres, an Icom 200 and a mode C transponder. With the Edge 915 ECI including oil and coolant, it puts 680 lbs on the scales. It was not always like that: it started out very basic with the small Shinn tyres and a Jab 22A, but no auxiliary tank. The result was 618 lbs. This only shows that you need to be extremely careful when you start loading on the goodies. The sword above your head are always those 1150 punds.

So true.

I think if I had not purchased a Sonex with wing tanks, the back of the seat Aux fuel tank idea has a lot of merit. Likely lighter/litre capacity, than 2x 30 L wing tanks + plumbing/valves/sensors/etc & a simpler fuel transfer system - what's not to like?

Probably hoping for divine intervention however, I am seriously considering having my Sonex reweighed - I just can't get my head around its current empty weight.

My Waiex is disappointingly heavy. 335 kg (739lbs) with the supposedly lighter Rotax up front and I never added many extras. I am suspicious of how the main gear legs that seem to pull inwards after rolling forward might be putting extra pressure on the scales (I first noticed this when jacking up a main wheel and was surprised at how much the gear moved sideways once the wheel left the floor surface). Wondering if you are meant to relieve this pressure to get an accurate reading, anybody have any thoughts on this?

[Bryan Cotton]

Murray,
Where I used to work they had a sign on the wall : "One test is worth 1000 expert opinions."

My expert opinion is it won't make a ton of difference but you could test it.