VH to 19 Registered aircraft

[Geoff_H]

I have been building a CriCri similar aircraft for some years.  As it has two engines and CASA (unlike the original designer, UK an French authorities) says it is a twin in its behaviour even though it's two engines are just over 24 inches apart.  The endorsement will cost me $5k to $10k.  RAA can't seem to accommodate a twin engined aircraft.  So I have thought of changingind the engines to a single.

Question is what inspection etc are required by RAA to register the craft? What are the costs?  I know I have to get an RAA licence....never really understood why, I learned on  C150 and still fly them on occassions. But what other problems am I likely to encounter as it is a composite design very much unlike a cri cri, only the aerodynamics are similar.

[facthunter]

You'll have a prop clearance issue with it and maybe stallspeed.  It's an RAAus CERTIFICATE. Issued under an exemption. Anything signed off on the VH licence counts toward the RAA thing. VH experimental gives you the most options. Nev

[Geoff_H]

Thanks Nev.  Stall speed full flaps expected approx 35knots

[kasper]

If you go RAAus then with a single seat aircraft you have two paths with 3 end points:

1. engine = two options for rego:

    a. Stall speed 45kts or less wing area unimportant => CAO95.55 covers you and you get 19- rego

    b. Wing loading at MTOW 30kg/m^2 or less and you can alternate to a. => CAO 95.10  can cover you and you get 10- rego

2. 2xengines = 1 option for rego => Wing loading at MTOW 30kg/m^2 or less => CAO 95.10  can cover you and you get 10- rego

 

95.10 is the only current RAAus rego class that allow multi engine/multi prop/jet propulsion BUT you are limited to single seat and 30kg/m^2 at MTOW

 

95.10 does not work for efficient little single seaters because it gets caught with the MTOW wing load => not enough wing

95.55 does not allow jets or multi engine or even 2 propellers from 1 engine - but allows any wing area so long as stall speed is lower than 45knts at MTOW

[Geoff_H]

Hi Kasper, thanks but I would have to single engine it.   RAA are unable to accommodate two engines.  A recent attempt to register one totally failed. The aircraft has Junkers flaperons has a large speed range.  What about the beauratic stuff?  Are construction inspections required?

[Bruce Tuncks]

Geoff, I sure feel angry on your behalf. Could you replace one engine with a more powerful one and then, later when nobody is watching, return the second engine as a "safety" measure?

This is the best example I have ever heard of where "safety" measures achieve the opposite of what is intended. Well that and some safety features on power tools which mean you need 2 hands instead of one.

 

[facthunter]

Plenty of people continue to mishandle non centre engines and even high thrust line ones by getting too slow.  Nev

[Geoff_H]

The cri cri can take off and fly on one engine.  With props 600mm diameter and engined 400mm off centre it is engine out simple.  Tail surfaces are comparatively large, it is an aerobatic aircraft.

[Geoff_H]

I had an initial SAAA inspection.  If I can find a suitable single engine how would I get RAAA approval?

[APenNameAndThatA]

One engine is usually safer than two, unfortunately for you. 

Edited March 22, 2022 by APenNameAndThatA

[Bruce Tuncks]

I would just try and register it with one engine "removed" and see what they say.

It may well be that Apename is correct and that there are single engines which are more reliable than the 2 cri-cri ones. But things like a single ignition system have been registered in the past.

[Bruce Tuncks]

I never knew that one engine was usually safer than 2 ...  The 2 engined Jabiru in South Africa would seem to me to be more reliable than a single, as long as it could fly ok on one engine.

Please tell us more .

 

[spacesailor]

Check your wing area, just to be certain it fits into A Caturgory., somewhere.

spacesailor

[Geoff_H]

Ok you have me.  What is category A?

[facthunter]

Think he means "some".    Nev

[Geoff_H]

Thanks Nev, Spacey.  I am trying to catch up with RAA rules.  I have a lot to go but I think that the specs for wing loading etc are in line with other single seat aircraft.

[kasper]

5 hours ago, Geoff_H said:

Ok you have me.  What is category A?

Spacey is once bitten VERY shy ... he built what was supposed to be a 95.10 registered airframe back in the early 1990's and when he was finished they had changed 95.10 to introduce the wing load restriction and he was caught out.

 

The easiest thing with RAAus it to understand single seat has two possible paths limited by either wing load or 45kts stall in landing config.  Work out your MTOW wing load and either eliminate or consider 95.10.

 

All of the procedural steps are then within the Tech Manual and given you mihgt have a half built airframe call RAAus and talk to tech as they can accomodate their processes to suit the case in hand eg moving from GA/SAAA build to RAAus build part way through. 

 

RAAus tech  are very approachable and talk plain english.

 

Cheers

[Geoff_H]

One of the problems that I have in converting to a single engine is "which engine".  The original idea of this design was to build an aircraft that could be built for under $10k using tools and equipment that could be easily borrowed or used by 'friends'.  The two two stroke engines cost $4k.  They put out around 30hp together, each weighs just under 10kg.  They have 600mm props and operate up to 6000RPM.  So to keep the weight down, to maintain less than 45kts stall speed I need a light 30hp engine that is reasonably light including and drive speed reduction for a single prop that will have to turn at a slower speed ( still have to do the calcs on this)

[Thruster88]

The rotax 277 single cyl is 28hp and 30kg complete, the 377 twin cylinder is 35hp and 38kg complete. Weight includes gearbox and exhaust. They are both out of production. 377 will turn a 60inch prop and is a solid performer, have one on a single seat thruster. 

[onetrack]

The V-twin, 4-stroke, carburetted CH750 Kohler industrial engine is rated at 27HP at a governed 3600RPM, but it will pull 5500RPM, and run all day at 5000RPM. At 5000RPM, it would produce well over 30HP.

It's an all-alloy engine with a huge amount of finning, and it would provide a cheap source of engine power for an ultralight.

It weighs 48kgs in stock standard industrial form, but when you take off all the ducting (unnecessary for aircraft use) and replace the cast iron flywheel with an alloy one, the weight comes down to well under 40 kgs.

 

The bloke in the video below has set one up as an aircraft engine - but he's used a chain drive reduction, which I consider is about as backward an idea as you could get.

He was driven by cost, but a good quality belt drive for a bit more money is a far better arrangement, quieter, far less prone to wear and trouble, and lighter, too.

His modified intake manifolding for the jettable Mikuni is pretty amateurish, I reckon he's probably lost a couple of HP with that crude setup, it wouldn't take much to improve on his workmanship.

 

https://www.youtube.com/watch?v=Z7oRT2cxPdo

 

 

 

[kasper]

5 hours ago, Geoff_H said:

One of the problems that I have in converting to a single engine is "which engine".  The original idea of this design was to build an aircraft that could be built for under $10k using tools and equipment that could be easily borrowed or used by 'friends'.  The two two stroke engines cost $4k.  They put out around 30hp together, each weighs just under 10kg.  They have 600mm props and operate up to 6000RPM.  So to keep the weight down, to maintain less than 45kts stall speed I need a light 30hp engine that is reasonably light including and drive speed reduction for a single prop that will have to turn at a slower speed ( still have to do the calcs on this)

Your options are limited.

 

Second hand out of production engines that fit your need:

Rotax 277 single pot two stroke = 27hp (in my experience ponies not horses)

KFM 107ER or ERMaxi = horizontal twin two stroke - electric start and 25-30hp (in my experience horses not ponies) - 24-25kg installed (I have 3 of these engines)

 

Current production

Hirth F23 = horizontal twin two stroke - electric start and 50hp (in my experience horses not ponies) - 26kg installed (I have 1 of these engines - best engine BUT expensive)

 

Beyond that you are looking direct drive high prop RPM with model engines or if you can get hold of them military drone engines ... I have 5 former drone engines putting out 26hp and are only 15kg including prop - but they are sinning the prop at near 6000rpm

 

I cannot think of any viable 4 strokes ... but given you are looking to replace 2 x 2strokes with a single staying 2 stroke should be OK for you.

 

Cheers.

[Geoff_H]

Howuch is a Hirth F23?

 

[kasper]

4 hours ago, Geoff_H said:

Howuch is a Hirth F23?

 

I can’t say now.  Contact them in Germany as there is no OZ agent

http://hirthengines.com/2-stroke-engines/

mine was second hand NOS and I built an aftermarket ignition and carb setup.

Mine was a bare spare core from an abandoned drone program I was involved in many years ago … its a lovely engine as are the KFM107s.