TurbAero

There was one in Perth when I was there in 1981 and more recently (1990s), Quentin Campbell built and flew one in Canberra. I watched Quentin’s build and it was straightforward. I never got a flight report from him on it though. I have the plans for it and used a combination of it and the Hummelbirds plans to draw up a set of plans for a half sized Messerschmitt 109 replica. I finished the fuselage and vertical before deciding I wanted it to look closer to the original than the replica that I was building. What I can say about the construction technique which leant heavily on the T2 is that construction is simple and once you learn the basics, things can progress quickly.

Nev, I totally agree with both comments. To be frank, given the heavier weight of the Jab engine (and its perceived reputation in the US) we will probably push the 100hp Rotax 912 as the powerplant of choice for the standard Bug. The one we had flying in the US with a tired 912ULS in it and a fixed pitch Prince P-tip topped out at just over 180 knots, but again takeoff rpm was way too low and even climb was only at around 4800rpm due to the huge pitch on the prop. It still climbed at around 1200fpm at those low rpm’s. Again, we need to get a CS prop onto that and the Eprop Glorieuse would be ideal by the looks of it. We want to thoroughly test the Jab powered Bug because that is what we have here in Adelaide and the owner won’t be swapping out the engine any time soon. Having comparison figures between the Jab and the Rotax will be useful and having constant speed props on both will allow the ability to check optimum performance across the whole flight envelope. The new build Bug in the US will potentially have a turbocharged 160hp Edge Performance EP912sTI in it but we are still determining if that powerplant will fit. Fortunately we have a bit more real estate under the cowling in the new build Bug because we have done away with the centre structural keel which took up about 10” of lower cowl space at the firewall, reducing to 3” at the air intake behind the spinner. We know that the stock 912 fits in with the keel but without the keel, we should have room for the turbo system of the EP912. Based on the close to 200 knots we are getting from our 120hp Jab powered Bug with a fixed nosewheel, having 120hp available at 10,000’ and a retractable nosewheel or a tailwheel and lighter airframe should yield a decent cruise. Fun times ahead! As for Airmaster props fitted to Jab3300s, there are a bunch out there. We have one Arion Lightning builder here in Adelaide that used Airmasters on both his Jab powered Lightnings and there are a bunch of others out there doing the same thing. Since Airmaster build a system specifically for the Jab3300 engine, perhaps it’s wishful thinking that the system meets the moment of inertia limitations for the Jab… Anyway, back to the original post, is anyone aware of an Airmaster prop that might be available? Perhaps a damaged or retired aircraft? Perhaps a project that won’t be completed? Dave

The Bug goes fast with a fixed pitch prop but suffers on takeoff and climb if you can call a 400m takeoff roll and a 1500fpm climb suffering 😂. We want to optimise its performance across the entire operational envelope.

Thanks for the suggestion Thruster. We have considered that approach which is workable for gaining climb numbers because we can pitch it for a safe speed. However, we also want to test takeoff performance with maximum power available throughout the entire takeoff roll and we cannot pitch a ground adjustable one to do this. So one way or the other, we need an IFA prop and preferably a CS unit. FYI, at 120kias on a standard day, current climb rate is around 1500fpm but power is way down of course at 2600rpm. If full power was available, it should be up at around 2000fpm which is a useful rate of climb.

He would like to use the eprop which has had very good results when fitted to higher speed aircraft with the Rotax fitted, I.e. the Blackwing that exceeds 200 knots, and the weight is definitely appealing. However, his aircraft is ready right now for a CS prop and we would like to get testing done asap as we want to be able to publish accurate and verifiable performance figures for the aircraft as we would like to market both the budget version (200 knots top speed) and the sports version (220+ knots). For the budget Bug, the Jabiru or Rotax will likely be the engine of choice so we want to be able to provide performance figures for the aircraft that is fitted with those engines. The sports version is currently under construction in the US.

Hi Skippy, as I see it, the E-props CS prop is the Glorieuse which is currently for the Rotax (geared) engine only. They have one under development for direct drive engines but it is not yet available. So unfortunately, they do not appear to have a viable solution for my buddy at this stage. I appreciate the suggestion and thanks for taking the time to respond.

Hi everyone, My buddy has a Lightning Bug aircraft that is fitted with a Jabiru 3300 and a ground adjustable 2 bladed 64” diameter Bolly Optima prop. A photo is attached for interest. When pitched for a reasonable cruise (3000rpm, 180 knots), static rpm of course is very low, around 2400 and during climb at 120 knots, max rpm is around 2600rpm. Clearly, he is losing out on power badly on the takeoff roll and in the climb. He wants to address that by using a constant speed prop so he can maximise takeoff, climb and cruise power. Flat out at 3300rpm when the blades are pitched for maximum speed, TAS is around 195ktas, but he expects to pick up another 5 knots once the aircraft is painted and it has a smooth finish. The Airmaster prop system seems to be the most suitable for this application and the Airmaster AP420CTF is the appropriate system for the Jab3300. Of course, he needs to match that with the right blades as this aircraft is optimised for speed. With the cost of a new Airmaster system being fairly high, he would ideally like to borrow one of these prop systems to try it out before committing to a purchase. Alternatively, if there is a good quality second hand one available that would represent a cost saving over a new one, he would be interested in that. If you have or know of someone who might have an AP420CTF system that meets the borrow or buy criteria above, could you please reach out to me to discuss the options? Cheers, Dave

I hear it was Mr. Ed. You can get the story straight from the horses mouth.

And our very own one at Goolwa, albeit stretched.

I’ll be there with mini-me as well, although with my mini-me being 196cm, I am actually the mini-me. I hate that! I believe that I am slotted to give a talk about our turbine engine development program. Please come and say G’day and I’ll try not to bore you to tears! Dave

There was a red Tipsy Nipper in a hangar at Parafield for many years when I was younger so during the 70s. I took a real fancy to that aircraft!

Just aft of the rear cockpit. There will be two small 180lbf thrust jet engines mounted on pylons. The exhaust will pass between the horizontal and vertical stabs.

Oh, and my Jet Bug variant…

Rapture Aircraft are refreshing the Bug with a full structural redesign and re-engine to take the 100hp Rotax 912 and the 200hp TurbAero Talon turboprop. If you are on Facebook, you can see more info at the link below. Rapture Aircraft

Here is our very own Australian Bug, based at Rollo’s Airfield near Murray Bridge, SA. It is Jabiru 3300 powered and tops out at close to 200ktas.

We haven't yet predicted the noise levels but in 6 months time, I'll let you know!! Given that the recuperator is reducing the amount of energy that exits the engine via the exhaust by quite a significant amount, we are hoping that the engine will be a little quieter than your typical small gas turbine. That said, I am definitely not an acoustics engineer so I may be way off the mark!!

We anticipate that the Specific Fuel Consumption (SFC) of the Talon (the name for our 200hp recuperated turboprop) will be around 0.56 lbs/hp/hr at 10,000' ISA conditions when the engine is operating in the 150-180hp range. So 150hp at 10,000' will yield a fuel flow of 12.6gph/48 litres p.h. of JetA. To compare the Talon to a 200hp IO-360 at the same altitude, the IO-360 will be running at WOT and be producing 142hp maximum with a fuel flow of 11.8gph/45 litres p.h. of the more expensive Avgas. The cost of fuel for those cruise conditions is in favour of the turbine, due to the difference in price between JetA and Avgas. Also, our Talon engine will still have 189hp available at 10,000' versus the IO-360's 142hp maximum. As power is reduced below 150hp, the SFC (fuel efficiency) of the Talon will deteriorate so if the power is reduced to 120hp in the circuit for example, the fuel flow may be around 9gph/34 litres p.h. The Jabiru 3300 owners will know what their engine burns at sea level and WOT. I suspect that the 200hp turbine will be burning more fuel at that power setting but that power setting is not where the engine is being optimised. We can only do so much... RFguy, our 120hp variant which will be optimised for the 100-120hp power band and at a lower level will potentially reach your acceptable efficiency/price point targets.

Geoff, from our perspective, simplicity/lower parts counts/lower temperatures/lower pressure ratios/conventional technology = lower cost, and lower cost = more sales, assuming functionality, performance and reliability all meet the necessary standards. We have already introduced recuperator technology which is proven, but packaging it into a small aviation engine envelope is the challenging part. However, it is the technology that is the most likely solution to improving fuel efficiency, but containing cost. We shall stick with that technology for now.

I sincerely hope that we can be the one that successfully makes it into the market!

I’d have to get my engineers to answer that one with any authority and unfortunately, they don’t have time to be on the forums. I don’t want to embarrass myself by giving incorrect or misleading information, but I think mass flow through the engine heavily influences the rpm for best efficiency.

It is conventional small gas turbine blade technology. No blade cooling and nothing special about the blades. We cannot build the turbines in Australia so the turbines will be manufactured outside Australia. I’m not sure what you mean by what class of turbine they are. It will be a 200hp (sea level ISA + 10deg.c.) rated, recuperated, twin spool gas turbine.

Thanks rgmwa. To clarify, the two engineers were there as owners of experimental aircraft, not as representatives of the company they worked for. However, it was pleasing to have them show that they “get” what we are doing and that our technical approach was considered to be acceptable enough to them that they would put their names down for an engine.

Yes, we got a huge amount of both interest and support for the engine. We had over 2000 visitors to the booth during the week with over 800 proper engagements with our volunteer staff who were manning the display. We were fortunate to have our Chief Technology Officer as well as one of our senior designers on the stand who could answer any technical questions. Visitors included turbine engineers from GE and P&W, both of whom grilled our CTO intensely but afterwards, reserved an engine on the spot. Our engine simulator that replicated the engine cycle, offering a view of all internal temperatures and pressures, as well as rpm, fuel flow and power at the prop was a big hit. While we do not have an actual engine running yet, the number of people who indicated their support by stating that it was way overdue for someone to have a good go at offering a Turbine alternative to the legacy pistons was nice to hear. The support really was tremendous.

I guess that's going to be me... Fortunately, our two flying original Lightning Bugs both have honest stalls so without changing the aerodynamics, I am hoping that the new Bug will be the same. Your 912 would go into a new Bug ok and even 80hp would give it reasonable performance, even a long-wing RAAus type one. I think I have a couple of AMW808s sitting in the corner of the hangar now and that's the best place for them!

You are right, it won’t quite make RAAus registration requirements as is and indeed, even when it gets the wings attached. I’m thinking about a long wing version which could make it eligible. It would still be fast but have a lower stall speed. I wonder how much interest there would be in the Rotax long wing variant RAAus compliant variant? It’d probably still cruise at 150ktas. The rudder is extremely effective. It has been reported by the two pilots who are currently flying Bugs to be the most responsive and effective of the 3 flight controls. Who in their right mind would fly this aircraft slowly? If I heard that someone was wanting to do this, I’d have to wonder about their state of mind 🤣.