Looking for an Airmaster prop for a Jabiru 3300 to buy or borrow

[TurbAero]

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

[skippydiesel]

FYI - Check the weight of the Airmaster CS and then compare with the EProp CS

[TurbAero]

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.

[skippydiesel]

If you have the time, may be worth waiting for the E - my Airmaster is approaching + 12 kg on the nose

[TurbAero]

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.

 

 

[Thruster88]

Your buddy could pitch the current Bolly prop for max power rpm in the climb to see how much climb performance will be gained. No cost and quick to do.

[TurbAero]

50 minutes ago, Thruster88 said:

Your buddy could pitch the current Bolly prop for max power rpm in the climb to see how much climb performance will be gained. No cost and quick to do.

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.

[facthunter]

Don't forget all the schneider Cup Racers were fixed pitch Props and they had to take off on water.    Nev

[skippydiesel]

10 minutes ago, facthunter said:

Don't forget all the schneider Cup Racers were fixed pitch Props and they had to take off on water.    Nev

Yeh! but if so desired, they could take all the ocean to climb .

[facthunter]

They were extremely hard to handle in the take off Phase as the torque buried one float. Yes their main game was speed but that can be converted to climb rate. The floats hampered both but they still went very fast on a fixed pitch prop.  Nev

[TurbAero]

3 hours ago, facthunter said:

They were extremely hard to handle in the take off Phase as the torque buried one float. Yes their main game was speed but that can be converted to climb rate. The floats hampered both but they still went very fast on a fixed pitch prop.  Nev

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.

[RFguy]

Hi TurbAero.

That's a high range of ops requirement- IE cruise/Vs. 

The std Jab prop pitched less than 2800-2850 static will perform very poorly on TO roll. So pitched at 2400 wow it must be a real dog. 

 

My 1st suggestion is move to more blades. Going from two to three blades means    each of the blades are not so loaded (think of it as more effective AoA) for a given poor efficiency scenario  , and in the TO roll, this WILL translate to better performance .  3 vs 2 wont cost too much in cruise but that depends on the blade profile. Maybe try a four blade from Bolly- They do have one and will sell it if you really want it.  

2nd- The airmaster is a good solution and there is a guy Marc Halcomb with an Arion Lightning in the US i know with one on his supercharged 3300 that he flies over the rockies with. 

But- be aware the Airmaster moment of inertia exceeds the Jabiru maximum spec by 'quite alot' . Now, FWIW, I dont know if there is any science to the Jabiru specification- IE maybe it is just what their propellor is ! That is what I think, however, this would be treated, in my opinion (I am not an aero engineer)  with some care because the Jab prop hub / flange is a bit of a weak point AND  the engine normal operatign conditions DO NOT assume a big heavy prop- this affects vibration behaviour....

Nevertheless Marc with his Arion  has not had any trouble so far. If you would like to be put it touch let me know. https://www.kitplanes.com/supercharger-for-jabiru-3300/

 

 

Edited November 10, 2023 by RFguy

[facthunter]

Yes a C/S seems like a necessity but a fixed pitch prop can be better at ONE particular speed than any C/S or in flight adjustable. With the Jab if there's any added possibility of a prop failure it's no good idea to go there for your business.  Nev

Edited November 10, 2023 by facthunter

[TurbAero]

1 hour ago, facthunter said:

Yes a C/S seems like a necessity but a fixed pitch prop can be better at ONE particular speed than any C/S or in flight adjustable. With the Jab if there's any added possibility of a prop failure it's no good idea to go there for your business.  Nev

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