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Balancing the Brolga Prop


Guest MundooTriker
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Guest MundooTriker

Hello All,

 

I have tried to locate the Brolga prop manufacturer to confirm the procedure for balancing/servicing the prop.

 

Before I contact/bother Airborne does anyone have any suggestions to point me in the right direction.

 

Thanks

 

Andrew

 

 

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Guest MundooTriker

John,

 

The Airborne Manual basically tells me just to check the bolt torques, and not touch anything else unless absolutely certain about what you are doing.

 

The LAME doing my 100hr asked for a prop manual to check the tracking.

 

What do do you generally do for servicing your prop?

 

Regards

 

Andrew

 

 

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There is no tracking adjustment possible on the Brolga props as the blades are held in by pitch-blocks which establish tracking and pitch simultaneously. No mention of shimming pitch-blocks in the hub for tracking adjustment is made in the manufacturer's documentation, therefore it is not necessary. The blade-bolts are to be torqued to 120 inch-pounds, the bolts securing the propeller-hub to the engine pro-flange are to be torqued to 168 inch-pounds (14 ft-pounds). My documentation of the prop (Assembly & Care Of Your Brolga Propeller) makes no mention at all of any tracking tolerances or adjustments of any kind.

 

Most maintenance required is filling in the dings in the leading edge in the last foot or so towards the tips caused by stones, gravel etc hitting the prop. This is especially so in trikes where the low-point of the prop-disc is quite close to the ground. A badly-dinged propeller runs out of balance and feels "rough" when you fly it.

 

To repair a ding, the affected area is first cleaned with a good solvent such as MEK or isopropyl alcohol and allowed to dry. Then high-strength Araldite (NOT the 5-min stuff) is mixed and a small amount applied to the dinged area. Immediately place adhesive-tape over this to make the epoxy resin conform to the propeller profile and leave for 24 hours. Remove the adhesive tape and carefully dress the repair if required.

 

Brolga recommend high-strength Araldite for repairs. The alternative, bicarbonate of soda wetted with Superglue (which cures in seconds to form a very hard and strong material) is something I haven't tried, but might be useful for a speedy repair if you haven't got 24 hours to wait for full bond-strength to be obtained with Araldite. This trick with bicarb and Superglue is also very useful on dinged wooden props because the material has a density close to that of the sort of wood used for props and it adheres to wood very well.

 

About the only other thing I have had to do is clean off the two-stroke oil from each blade where it sweeps past the trike exhaust, and re-paint the yellow tips. When doing this, I find a base-coat of brilliant white first helps the yellow to really shine through.

 

Brolga state the prop has no definite life, and I have done 1100 hours on one which is still emiently serviceable. They recommend re-torquing blade-bolts and hub-bolts every 20 hours. When re-torquing, loosen the nuts first and bring them back up to the rated torque slowly and evenly, then double-check each nut again.

 

Every 200 hours dismantle the propeller and inspect the blades, pitch-blocks hub-halves and steel hub reinforcement plate for cracks and obvious damage such as delamination or elongation of the holes.

 

Any prop-strike is cause for a complete disassembly and inspection and replacement of any components displaying stress-fractures of cracking of any kind. Also, surface corrosion on any prop-bolts or nuts is cause for immediate replacement of the hardware affected. Every 1000 hours the entire set of hub and blade bolts is to be replaced.

 

The Brolga is a very durable propeller and will last one heck of a long time with proper maintenance and care. FWIW, the only Brolga prop-blade I ever saw delaminated was on a prop that suffered contact with the runway whilst under power. The blade(s) were decommissioned, and I think the entire prop was replaced.

 

Hope this helps.

 

 

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You beat me to reply DieselTen and a comprehensive answer. Maybe you could fax or post a copy of the brolga service doc to Andrew if it would help satisfy his LAME ( think he is getting a bit carried away wanting a specific manual for the prop).

 

Cheers

 

John

 

PS the superglue + bicarb of soda does work well as a get you home repair but alraldite (or devcon) makes a better quality repair IMO

 

 

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.... The blade-bolts are to be torqued to 120 inch-pounds, the bolts securing the propeller-hub to the engine pro-flange are to be torqued to 168 inch-pounds (14 ft-pounds).....

From my personal experience I would also point out that any higher torque than that specified will result in the hub, which is made up of layers of plastics and steel deforming and delaminating.

 

On my trike I think the previous owner had over torqued mine because I could never reach 120 while feeling that the hub wasn't deforming.

 

I also identified that the brolga prop is actually brolga blades in a 3rd party hub. While the pitch blocks are fixed in place the hub, if purchased from overseas is available with a number of different pitch block combinations so as to be able to end up with finer or courser prop pitch overall. For me, I identified this just after I had paid for a brolga replacement and I recall that the difference in AUD to USD was eyebrow lifting and caused wallet spasms from memory it was $70USD vs $270AUD. Of course the USD didnt include postage etc so would have cost more, but less than 270 by lots

 

the website in the US is here, click on products link in the following page for the hub details. The details that dieslton gave are reproduced on the following page.

 

http://www.competitionaircraft.com/Brolga.htm

 

Andy

 

P.S note the coment on the page identified above "These propellers utilize the same proven hub and pitch block system as our standard props, with blades made with glass reinforced nylon. However, the hubs and pitch blocks are modified to use 5/16" hardware in place of the 1/4 " on the standard Ultra-Prop." What the modofocation is, I dont know, it could be a different hub or the 1/4 holes are simply oversized to 5/16 so care is required. I'd also draw your attention to the certified nature of the Aircraft and point out the potential problem of sourcing alternate components on the certification status.

 

P.P.S the torque setiings on the web page identified above arent the same as that which Dieslton identified so care should be taken and Airbornes specification (which from memory is that which diesleton provided) should be followed.

 

 

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Guest MundooTriker

Thanks Chaps,

 

I appreciate the advice - Dieselten, Andy and John. I thought that all I had to do was what was in the Airborne Manual, but I got confused when asked for tracking specs.

 

Thanks for putting my mind at ease.

 

Andrew

 

 

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