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Subject:
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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