Ivoprop service bulletins 2

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Ivoprop service bulletins

Ivoprop ultralight & model 3:1 gearboxes
or direct drive engines or 3 cylinder engines. Note This Service Bulletin supersedes any previous operational alerts issued by Ivoprop Corp.

Purpose: To detect blade movement inside the hub due to improper installation and, or harmonic resonance between prop and power plant; To prevent further flight if this situation is detected and develops in unsafe condition (aluminium bushings becoming loose breaking bolts, blades etc ... ) "new blades do not have bushings"

Introduction: Above mentioned combinations produce high level of torsional pulses during their firing cycle which several times exceed their nominal torque and also torque reversal pulses. If the prop is mounted loose and or gets in harmonic resonance with the engine the blades could move inside the hub back and forth in a plane of prop rotation.

What to do: Prior to the next flight, accomplish the following:

Get torque wrench and check its calibration by hanging a known weight on its arm and multiplying the weight in pounds by arm in inches. This reading should be as close as possible to actual recommended torque on mounting bolts. (We tried several torque wrenches and most of them were off by a lot.) Check torque on mounting bolts. 200 inch x lbs.

Direct drive engines only: Mark the prop position in relation to the crankshaft. There are two positions to mount 3-blade prop and three positions to mount 2-blade prop; this makes a great difference in how

the prop and engine vibrate together and each position creates a totally new situation. It is impossible to determine which position is best for your particular prop engine airframe combination without actually testing it on it.

Run the engine momentarily on the ground trough the full RPM range.

Check the torque on the mounting bolts and, if you are not using locknuts, safety wire the bolts.

Cut the strips of stainless steel tape about 2" long and '/4" wide (tape supplied with this service bulletin) Clean the area around the gap between blades, or gap between blades and blade blocks with MEK solvent.

Apply stainless steel tape across the gap next and parallel to mold parting line. Use a round object to press the stainless steel tape on the surface.

Follow this inspection schedule to check if the tape is broken: After short ground run up through full RPM range, and then first 15 min, 30 min, I hour, 2 hours, 4 hours, and then every preflight inspection. Also follow this schedule from the beginning if the prop has been reinstalled in a different position in relation to crankshaft.

If tape breaks or cracks remove the tape, clean the surface with MEK solvent and apply new tape and start inspection schedule from the beginning. If tape breaks again, do not fly with the prop and contact Ivoprop Corp.

Request to dealers: Please forward this service bulletin and stainless steel tape to your customers who are subject to this S.B. Keep the record of addresses of your customers to which this Service Bulletin applies. Make sure that any prop being sold for the above-mentioned combinations is accompanied by this Service Bulletin.

Compliance: Mandatory

Note: Do not use prop in 2-blade configuration without blade blocks 
(missing pieces of pie, which fill out the big gaps between the blades.)


Ways your prop can come loose!

Not torquing the bolts 
Do not rely on feel. Get torque wrench and calibrate it by yourself. Torque on mounting bolts is 200 inch x lbs. ( not 200 ft x lbs.)  

Bottoming the thread of the mounting bolts into the flange or lock nuts. Use extra washers if the bolts are too long.  

Inserting spinner composite baking plate anywhere between what bolts is supposed to compress together. 
These fiberglass or composite backing plates compress with heat and pressure resulting in torque loss on the bolts.  

Using wrong hardware. 
Rotax engines are supplied with prop crush plate which has stamped oversized holes. Do not use it.  

Important :

Do not modify the prop in any way.

Do not weld super cams on torsional rod.

Direct drive engine adaptors need AN5 bolts not 8mm bolts. 

Knurled Plates Instructions - Ultralight Model

The knurled plates should be installed so that knurling finish on each plate is in contact, with blades.  

The knurled pattern is 60 degrees symmetrical so, if you re-install the blades between crush plates later in a different position, the imprint on the blades should match the knurled pattern. However, due to manufacturing tolerances, to get the best match, number the blades and plates and always put the blades back in the same place.  

Torque the mounting bolts to 200 inch x lbs.  Dry (no oil or lubricant the thread) and run the prop momentarily through full RPM range. Re-torque the bolts.  

Install the Service Bulletin stainless steel tape and follow the inspection schedule from the Service Bulletin. Any time you inspect the tape, check the torque on the bolts during first four hours. After that, check torque every ten hours.  

If your blades have aluminum bushings around the bolt holes, make sure that knurled plates supplied to you are counter bored around the bolt holes. 


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