Catto Prop - How about slowing down?

I enjoyed the great discussion about Catto props. I am expecting mine in August. Would some of you Catto owners please discuss any challenges you are experiencing in slowing down, for example when preparing to land. Does the three-bladed Catto slow the plane a little better than a two blade fixed pitch prop?

Thanks in advance for any info.

Neal Powell
RV-9A
working on second wing
Quickbuild Fuse waiting for attention

Glide is good

My 3 blade glides like crazy. I would expect the 2 blade to glide even better, but one of those guys can tell you for sure.

I love my 3 blade except when I have to take the bottom cowling off, then I curse it from the depths of my soul

Flying alone slowing down is not a problem because you an prepare for it. If you're really fast say on downwind, I tend to pull the power almost completely and then pull the nose up to bleed off the speed.

When in formation and say coming in for the overhead break, then it can be more challenging. Haven't done it lately but the first couple of times lead would break then pull power and do the magic with the C/S prop and slow down instantly. Meanwhile I in the back would pull the power and glide right past him as he's turning base/final. I had so much extra momentum without the aid of a C/S prop acting like an air brake.

It is "different" ...

The slowdown with the Catto 3-blade versus a 2-blade Ed Sterba is just "different". You have to manage both and they can be managed. The point at which props feel like they are providing drag is at a different speed for the two.
It *might* be easier to manage with the Sterba on our 6 but then again, I have 100 times more hours with it so I probably have a better feel for things.

The Catto seems to want to fly down the runway (at full idle) a bit longer for a given approach speed.

If you plan the slowdown in advance, then everything works just fine.

James

More Than Just the Prop

I've been flying behind my 3 blade C. Catto prop now for about 5 years. Smooth operation is the key word. You become used to the performance of you aircraft and intuitively know when to slow down. In the pattern, however, you should (mostly) be at the proper speeds / altitude for flaps and then approach. If you pay attention to approach speed, you should never have too much speed over the threshold (and full flaps will slow you quite well).

As earlier identified, however, your ability to slow down "quickly" could become something to think about when flying with 'dissimilar' aircraft. But, since each RV is a 'custom built' aircraft, they are all dissimilar.

Bottom line is that you will appreciate your Catto prop. The props have a number of other attributes that I can describe to you in another thread sometime.

npowell said:

I enjoyed the great discussion about Catto props. I am expecting mine in August. Would some of you Catto owners please discuss any challenges you are experiencing in slowing down, for example when preparing to land. Does the three-bladed Catto slow the plane a little better than a two blade fixed pitch prop?

Thanks in advance for any info.

Neal Powell
RV-9A
working on second wing
Quickbuild Fuse waiting for attention

Click to expand...

The slowing-down ability of a fixed-pitch prop is strictly a function of its efficiency and its effective pitch. A lower pitch prop or a lower efficiency prop will cause more slowing down regardless of the number of blades, although a lower-efficiency, lower-pitch prop will probably generate more drag. Basically this harkens back to the mis-informed belief that the more blades there are on a prop the more loss it will have. This is only true if it's a poorly-designed prop, the kind that has klunky root shapes and wide, lossy tips. Keep in mind the operative word belief; beliefs are based on feelings and widely-held notions and are not subject to proof or scrutiny. 'Not that beliefs are wrong; everyone has a right to their beliefs, but anything that passes the test of rigorous provability is no longer a belief but is, instead, a fact! Don't take this as an observation on religion, it is instead an observation on acceptable science.

npowell said:

I enjoyed the great discussion about Catto props. I am expecting mine in August.
RV-9A
working on second wing
Quickbuild Fuse waiting for attention

Click to expand...

Don't expect too much, I was expecting mine LAST August and still waiting. Fortunately, I don't need mine yet.....

gbrasch said:

Don't expect too much, I was expecting mine LAST August and still waiting. Fortunately, I don't need mine yet.....

Click to expand...

You may want to call Craig...I put in my order on his "initial" list last July. Then got on the "real" list in late October when I sent him a 50% deposit. He just shipped my prop on Friday I believe, because it's at the Post Office waiting for me to take delivery.

elippse said:

The slowing-down ability of a fixed-pitch prop is strictly a function of its efficiency and its effective pitch.

Click to expand...

The diameter of a F/P prop also affects drag because of the disc area. A shorter prop will produce less drag than a longer one.

Another really big factor is idle rpm! Just a couple of hours ago during a hard x-wind approach to an airport some distance from home, I thought "How did I misjudge this so much--I'm really high." Then I pulled the last 1/8" of throttle that I thought I had done earlier. A little power makes a big difference.

I have my idle set at a really low--around 450. I never pull all the way on the ground, but down final it makes for pretty good braking. On the landing earlier today, I probably had the throttle in to about 700 ground rpm. If your compressions are nice and close, you can idle back pretty far. As always, do this gradually and with great care. YMMV.

Bob Kelly

What

What... a Catto slow you down... NOT!

videobobk said:

Another really big factor is idle rpm! Just a couple of hours ago during a hard x-wind approach to an airport some distance from home, I thought "How did I misjudge this so much--I'm really high." Then I pulled the last 1/8" of throttle that I thought I had done earlier. A little power makes a big difference.

I have my idle set at a really low--around 450. I never pull all the way on the ground, but down final it makes for pretty good braking. On the landing earlier today, I probably had the throttle in to about 700 ground rpm. If your compressions are nice and close, you can idle back pretty far. As always, do this gradually and with great care. YMMV.

Bob Kelly

Click to expand...

Bob,
You make a really great point. My last airplane was a PulsarXP...a slick little composite bird with a Rotax 912. Lots of guys had trouble slowing it down because they had their idle set at the "book value" of 1800 RPM.

The problem is, that with forward velocity there is little resistance so with the throttle pulled all the way out they could only get the RPMs down to about 2200. I tested landing (on a long runway) with throttle idle position set at 1800 and at 1600. The lower setting made slowing down MUCH easier...and that's how I left it.

lostpilot28 said:

You may want to call Craig...I put in my order on his "initial" list last July. Then got on the "real" list in late October when I sent him a 50% deposit. He just shipped my prop on Friday I believe, because it's at the Post Office waiting for me to take delivery.

Click to expand...

Thanks, I did and left a message. When I first put in my order, I offered him a deposit, but he told me I didn't need to. Thanks for the tip.

Mel said:

The diameter of a F/P prop also affects drag because of the disc area. A shorter prop will produce less drag than a longer one.

Click to expand...

Hi, Mel! That could be because a larger diameter prop has a higher tip speed
at a given rotational velocity so that the tip losses are greater the larger the diameter. I was surprised at how much higher the efficiency was shown in my equations by just reducing a prop design diameter 2". And this with a very low drag tip!