Hartzelll 3 blade prop

[Matt Whiting]

Anyone here converted an Arrow 180 to a three-blade prop? My flying
club recently converted its Arrow when the two-blade prop was found to
be shot during its overhaul. The three-blade was cheaper than a
two-blade, which seems odd to me still, so that was the choice. The
problem is that it vibrates a lot, especially at lower RPM (below 2200).
I joined the club just after the replacement so I don't know what the
two-blade was like, but it now vibrates a lot more than my Skylane did
(I realize the 6 vs 4 cylinder engine likely makes some difference
here). However, other club members say it vibrates a lot more. We were
told that the prop could be mounted in one of two possible positions,
180 apart and that there was no way to know in advance which position
was correct (this also seems odd to me). After the first test flight,
the prop was remounted and the vibration was less, but still seems
excessive.

I'm just curious if others have noticed this. I would have thought the
three-blade would have been smoother if anything, but that certainly
isn't the case. We're considering taking the plane to a shop that can
do a prop balance, but the engine is near overhaul so we're considering
waiting until next winter when we'll get both done.


Matt

[BTIZ]

if installed properly.. the tach should be marked for non continuous
operation in a range somewhere between 1900 and 2200 RPM.. (don't trust my
memory.. look it up) I've flown a 3 bladed arrow.. and yes.. when you pull
the power back.. it does vibrate as it comes down through that RPM range..

BT

"Matt Whiting" > wrote in message
...
>
> Anyone here converted an Arrow 180 to a three-blade prop? My flying
> club recently converted its Arrow when the two-blade prop was found to
> be shot during its overhaul. The three-blade was cheaper than a
> two-blade, which seems odd to me still, so that was the choice. The
> problem is that it vibrates a lot, especially at lower RPM (below 2200).
> I joined the club just after the replacement so I don't know what the
> two-blade was like, but it now vibrates a lot more than my Skylane did
> (I realize the 6 vs 4 cylinder engine likely makes some difference
> here). However, other club members say it vibrates a lot more. We were
> told that the prop could be mounted in one of two possible positions,
> 180 apart and that there was no way to know in advance which position
> was correct (this also seems odd to me). After the first test flight,
> the prop was remounted and the vibration was less, but still seems
> excessive.
>
> I'm just curious if others have noticed this. I would have thought the
> three-blade would have been smoother if anything, but that certainly
> isn't the case. We're considering taking the plane to a shop that can
> do a prop balance, but the engine is near overhaul so we're considering
> waiting until next winter when we'll get both done.
>
>
> Matt
>

[EDR]

Sounds like the prop needs balanced.
You have a four cylinder engine with at three bladed prop. The cylinder
and prop impulses are oddly synched. More mass and inertia than with
the two blace.

[PaulH]

I did the conversion on my Arrow and had the same problem. I had it
dynamically balanced and rotated 180 and it is now very smooth. There
should be a placard to avoid continuous operation at low power
settings within a certain range - can't remember the numbers, since
it's not a range I normally use for any length of time.

Be careful of power off approaches with prop in high pitch. Those 3
blades form a very effective speed brake in idle mode. It's useful to
do a crowbar approach while staying above jet vortices but requires
some practice.

[Matt Whiting]

BTIZ wrote:

> if installed properly.. the tach should be marked for non continuous
> operation in a range somewhere between 1900 and 2200 RPM.. (don't trust my
> memory.. look it up) I've flown a 3 bladed arrow.. and yes.. when you pull
> the power back.. it does vibrate as it comes down through that RPM range..

Our tach was not remarked and there is no placarded prohibited range.
Ours vibrates from 2200 down to about 1200.


Matt

[Matt Whiting]

PaulH wrote:

> I did the conversion on my Arrow and had the same problem. I had it
> dynamically balanced and rotated 180 and it is now very smooth. There
> should be a placard to avoid continuous operation at low power
> settings within a certain range - can't remember the numbers, since
> it's not a range I normally use for any length of time.

That's encouraging to hear as we're considering a dynamic balance. The
prop was already rotated 180 and that made some difference, but not
much. No RPM prohibition was mentioned, but that may have been an
oversight.


> Be careful of power off approaches with prop in high pitch. Those 3
> blades form a very effective speed brake in idle mode. It's useful to
> do a crowbar approach while staying above jet vortices but requires
> some practice.

Yes, we learned this very quickly. At less than 1600 RPM the airplane
drops like a rock.


Matt

[BTIZ]

Matt... the rental Arrow POH (in the airplane).. has information for both 2
blade and 3 blade prop installations from the factory... it has the limits
on the non-continuous operations in there.. and with a 3 blade prop
installed.. the limits should also be placarded and marked in red on the
tach..

Sounds like an incomplete installation... unless the STC that governs the
installation does not mention it... would be surprising..

The arrow performs nicely with a 3 bladed prop on an ILS approach..
configured and keeping the RPM as desired.. you need to practice the
approach speeds and "fly by the numbers".. screw up the configuration.. ie
needing idle power to get down to the glide slope and that prop really
complains... or when pulling the power during the flare after breaking out
at 200ft.

BT

"Matt Whiting" > wrote in message
...
> BTIZ wrote:
>
> > if installed properly.. the tach should be marked for non continuous
> > operation in a range somewhere between 1900 and 2200 RPM.. (don't trust
my
> > memory.. look it up) I've flown a 3 bladed arrow.. and yes.. when you
pull
> > the power back.. it does vibrate as it comes down through that RPM
range..
>
> Our tach was not remarked and there is no placarded prohibited range.
> Ours vibrates from 2200 down to about 1200.
>
>
> Matt
>