"Bart D. Hull" wrote

Did ya know Warp drive was designed and owned by Ivo as well? I have NEVER
found ANYONE that has actually had a Ivoprop fail on them.

just my 2 cents.

Bart

Bart, I was looking at a Dragonfly that shed it's Ivo prop; I was told to
investigate it carefully because last they saw it... "we were waiting for
them to arrive we saw a streak on final and as they landed the three blades
of the Ivo prop went sailing somewhere."

I also heard that there was no good way to assemble and align the prop
before mounting it on the engine but rather it had to be built right on the
hub with no really good way to align it in all dimensions.

You mentioned that stainless steel inspection tape. Seems copper tape was
used initially but broke too often. Was switching to steel fixing the
symptom or the problem?

Comment(s)?

Eric

I looked on the net for supporting info and found the following (which,
granted, is a few years old):
------------------------------------------------------
From: Dennis Jackson
Subject: Adjustable Props..
Date: 1997/09/08
Message-ID:
References:


Reply-To:
To: "prof S. A. Campbell"
Organization: TMS
Newsgroups: rec.aviation.homebuilt


prof S. A. Campbell wrote:

In article ,
Dennis Jackson wrote:

Can anyone suggest a reasonably low cost in-flight adjustable pitch
prop 2or3 blade in the 250-340 h.p. range? Thanks, Mike


I say the IVO Magnum prop will kill someone soon if it hasn't already.
It is very dependent on careful assembly and constant monitoring to make
sure it's not coming apart. It might be OK for ultralight engines but
forget it for high horsepower apps.

DJ

OK DJ, what is your basis for making this claim? Have you owned a
Magnum? Do you personally know someone who has had problems with them?
If so, with what engine? A number of people have tried putting them on
O-360 and IO-360's with decidedly mixed results, but if you stay aware
from these engines, I have heard nothing but good things about the
Magnum. Are you just ranting, or do you have real information?
Steve


Steve:
I guess I might as well drop the whole enchilada and get it over with.
Wait just a minute while I put on my asbestos underwear. I am not a
mechanical engineer, so my opinions should only be given the weight they
deserve, but I do speak from experience and know two people personally
who have had similar experiences with the Magnum prop, both RV builders
using 160 hp Lycs. This discussion is also taking place on the RV-List
so you can get more opinions there (http://www.matronics.com). At least
I am not alone in my opinions. I am glad to say that I have not heard
of any fatalities due to this prop and I have seen a couple of them
flying so maybe Ivo has solved the problems but I still remain
skeptical.

Anyway, after my experiences I became concerned about others use of this
prop and wrote a warning letter to other RV builders. Here is the
letter I sent at that time to Ken Scott at Van's Aircraft who published
an edited version in the RVator.


11/22/95

Ken:

Here's a little writeup on my adventures with the Ivoprop Magnum
propellor. If you could use it in the Rvator then feel free. I think
something should be published as a warning. This prop is not safe.

I installed an Ivoprop Magnum model MR-68-2 on my RV-4 with a Lycoming
IO320-B1X 160 hp engine (the X means that I changed the sump to fit the
RV-4). This prop is a 2 blade 68 inch dia ground-adjustable carbon
fiber unit that has steel torsion rods that run lengthwise in the blades
that can be twisted with a cam to adjust pitch. Each blade is a
separate piece held on by two hub bolts and separated by spacers which
are held under the two remaining bolts. The prop can also be set up as
a three-blade in which case no spacers are used. I had heard that some
people have experienced structural failures with this prop (of course
not until I bought one) so naturally I was concerned but figured I could
put a few hours on the prop without worry. Wrong.

Before I started the engine, I received a factory directive to install
tell-tale copper tape strips across the prop root junctions. This tape
will break if there is any movement of the blades. I ran the prop on the
ground for approx 10 minutes and then flew two times about 15 minutes
each. At no time did the engine speed exceed 2400 RPM, therefore power
to the prop was limited to no more than 135 HP. Upon ground runup I
found that the tape had broken on all joints. I then checked the bolt
torque and retaped the joints. The engine was again run up and 3 of the
4 joints failed again. After retorqueing and taping the airplane was
flown (first flight by Mike Seager) for about 15 minutes, landed, and
found all four joints broken. Retorqued, retaped, flew again (me this
time) for about the same amount of time with the same results.

I then removed the prop and I found that the prop blades showed friction
burning on the surfaces around the bolt lugs with a residue of black
(carbon?) dust around the area. The hub and front spinner plate showed
similar rubbing and residue where in contact with the prop blades.

While I like the basic idea of a ground or in-flight adjustable
propellor, I think this design is flawed in that there is too much
leverage at the base of the propellor for the clamping forces of the two
bolts to hold. Taking measurements on the hub, bolts, and prop bolt
barrels, I found that the bolts measured 0.496 o.d. and the hub and prop
barrels were 0.500 i.d., thus leaving about .004 inches slop in the
fit. This allows enough movement to overcome the clamping friction. If
this were a zero tolerance fit, it might work. I would be more
comfortable with extended bolts barrels that were a zero tolerance fit
into the hub holes.

The only thing preventing rotation of the propeller blades with engine
power pulses is the friction between the blade and hub on one side and
blade and spinner plate on the other. Perhaps this arrangement is
reliable with shorter blades and smaller engines such as 2-stroke
engines on ultralights, but it is insufficient on larger engines with
heavier power pulses and the larger and longer blades necessary with
higher power. There is simply too much inertia in the blade and too
much leverage on the small base at the hub. The blades will work back
and forth with each power stroke.

Another area of concern is the minimal edge distance of the bolt barrels
to the prop base. There does not appear to be any reinforcing around
the barrels. How are the barrels anchored into the prop? Are the
barrels connected together? If not, then what will prevent the barrels
from working loose in the prop and fracturing the base with a resultant
loss of a blade?

I talked with another RV-4 driver in Kentucky and he experienced the
same chafing due to movement of the blades against the hub and in
addition found that one bolt barrel was starting to loosen in the hub
and the hub had fractured across the base parallel to the barrel. He
had put less than 3 hours on the propeller.

Another negative is the necessity of leaving the spinner off to
facilitate inspection. For aesthetic and aerodynamic reasons this is
not an option for me.

I called Ivoprop and spoke to Ivo about the situation. He stated that
the copper tape was giving false readings and they are now recommending
stainless steel tape which will not break so easily!? He said that it
was normal for the blades to have some movement at first while seating
and then they should stabilize. He said that they have other ideas to
make the prop safe but I told him that I was just too much of a chicken
to test his theories and was not comfortable flying with his prop. To
Ivo's credit, he did not hesitate to offer a refund when I expressed my
desire to return the prop even though it was long past the 30 day
money-back guarantee period.

To sum up, it is my opinion that this design is UNSAFE. Anyone with the
Ivoprop Magnum propeller should immediately ground their aircraft and
remove the propeller. It is not a matter of IF it will fail, the
question is just WHEN will it fail. It is very likely that a fatality
will result if a blade suffers a catastrophic failure in flight, as the
resulting vibration can and probably will tear the engine from the
aircraft. Do not fly with this prop even one more hour!

Your pal,
Dennis