Prop Pitch Ground Adjust - Simple + Cheap

[SkyMenace]

As a new owner of a 2009 CTLS with a Ground Adjustable Neuform Prop I discovered the Prop Pitch was set too fat, lugging the engine and limiting Short Field with Obstacles performance.  (I fly out of a 2300 foot strip with 90+ foot trees at each end).

To gain Climb Out performance I decided to reduce the Prop Pitch to a fine, high RPM setting.

If you are new to adjusting the Prop Pitch you will find that in doing so the angle is sensitive to even the slightest movement and is difficult to keep in position by hand before tightening.

I found from other reviewers that the flimsy (and sometimes expensive) angle tools suggested elsewhere are difficult, inaccurate  and awkward to use

After numerous unsuccessful attempts I arrived at a simple and cheap method to accurately adjust with a minimum of effort and cost.  After blue taping at 75% of the Prop's Chord per the Neuform Prop Maintenance Manual (22.5" in my case), my A&P and I hung a Machinist Square with the Klein Gauge magnetically attached and moved each blade to same XX.X angle reading.  

Thanks to Arian Foldan at Flight Design in Woodstock Connecticut for suggesting the Klein Angle Gauge.  In combination with the Machinist Square, Easy, Peazy. (Both Items purchased from Amazon; <$40 for both, see images attached).

The new finer setting resulted in increasing the available Takeoff Vx RPM by 500; to the top of the allowable range (<4800 before the adjustment; now 5300+).  Now climbs out >1000 fpm at Max Gross Weight.

Please note: I noticed a 15+ knot decrease in Cruise Speed.  Not unexpected and not a negative for my local sight-seeing flights.

Be sure to torque the bolts per specs!

Prop Pitch Adjust, Simple + Cheap!.pdf

Klein Tools 935DAG Angle Gauge $30.pdf Steelex D3384 Machinist Square $9.pdf

[SkyMenace]

Finer Prop Pitch Landing Comment:

After reducing the Prop Pitch my CTLS now is less reluctant to land (less float).  Previously, she wanted to keep flying!  The additional Drag helps in this respect.  Also descends at a steeper angle and slows down quicker at Idle.  Most helpful when descending to land on my 2300 foot strip after crossing 90+ foot trees at, or near, the Runway Threshold.  As you might well imagine, I still Forward Slip aggressively to get down Short preventing my going off the far end of the Runway!

[Roger Lee]

Howdy,

You can set the prop pitch to even go as high as 5800 on climb out, but like you are noticing you give up cruise, fuel economy and even engine temps in hotter weather. Usually a flatter pitch setting is better for constant short field take offs, high altitude flying, amphibious aircraft and constant heavy loads.

Adjusting props including Neuform is actually easy. It can be done in 30 minutes start to finish. If you have questions give me a call. I do them on a regular basis and I've adjusted well over a a couple hundred props in my time because they either need an rpm change for the better or I find the pitch between blades are not equal. Anything more than 1/10th of a degree off is a sin. If done right the blades won't move after you turn it during the adjustment. Sounds like some bolts were too lose. Your glide really didn't change at the runway. Your speed is controlled by the stick. So you can land at the same speed and glide whether you're at 1700 rpm or 2600 rpm and  touchdown at the same speed. The only difference is the stick is back a little further if the rpm is higher. The minute prop pitch change you did did not affect this in any meaningful way.

Measurements can be done fairly easy without any special tools. One tool that helps is the prop protractor you can get from the Warp Drive group. The other tool is just a standard 12" digital level. Matter of fact you can do the whole thing with just this level if you want. Hec in the field at the Page, AZ Fly-In I've done props with just my Ipad with an Inclinometer app. 

 

 

[SkyMenace]

Hey Roger,

This is my first post on this forum.  I chose to insert the three images as pdf's, pretty much the same viewing quality as jpg's but smaller in size.  I see your image without having to download. Is that because you inserted it as a jpg?

Since Finer/Flatter Pitch creates more Drag, would not that result in a shorter Glide at the same Airspeed and RPM?  Additionally, before the adjustment it was more difficult to bleed off the Airspeed when in Ground Effect over the Runway.

I flew Twins for two decades and Feathering the Prop on a dead engine sure does increase Glide!  In Fine Pitch the Prop acts like a disc of plywood!

Your method has the advantage of knowing the blade is level at the same time the adjustment is made.  (We used a torpedo level for this, though I am not sure that affects the blade angle readout?) 

I found the one-point decimal readout of the Klein Gauge most helpful.  Placing even the slightest pressure - enough to get a movement response - would often cause the angle to jump by .3+ degrees!  I also found that each one tenth of a degree would generate a 100+/- rpm change.

Re:  Vx (related to Prop Pitch)

I have viewed numerous of your Posts on this forum and have found them most helpful.  Thank you for all the terrific input.  

Since you are so knowledgeable on the CTLS, could you help me out on nailing down the Optimal Takeoff/Climbout Speed over (what at my home strip, VA99) are 90’ trees at each end of the runway?

My AOI states Vx as 62 KIAS with 15’ Flaps.  Yet elsewhere I have read 51 -52 KIAS.  I have found 52 KIAS to work out well and within my comfort zone.  62 does not cut it for getting over the trees.  Or, perhaps, rather it would, cut the trees!

I have a RAM Checklist that states Vx with 15’ Flaps as 51 KIAS.

Which is it? Or rather, which do you recommend? 

RAM Checklist 1-stack.pdf

[GrassStripFlyBoy]

2 hours ago, SkyMenace said:

(I fly out of a 2300 foot strip with 90+ foot trees at each end)

Thinking this is a private strip?  That would leave some fairly short remaining runways with displaced thresholds. 

I fly from a 2k' strip but clear one direction another 1k', and 50' wires 600' beyond the other way.

My experience is in a lighter SW, and prop has the normal / optimal pitch setting.  Input I'll toss out is consider your climb out and approach speeds are variable depending on loading (solo or passenger / fuel level) as well as density altitude and wind gusts.  Those tall tress could present wind shear concerns?  

Climbing out at 52 is probably as low as I'd push it, be aware if engine quits you're needing to adjust nose down fairly quick.  On that note, in the past months I've worked some low speed departure simulated engine outs, this only take you to idle and prop keeps spinning.  Being solo I found there to be a lot of margin to enter best glide.  Might want to go up with full fuel and practice some of those situations.  These CT's really like to fly, but when they quit flying it's like a switch is flipped.

If strip is grass then that's a whole new topic of optimum take off distance.  Those of us who fly a lot of grass tend to get nose up ASAP, and let airplane fly off ASAP.  Don't linger in ground effect but gradually increase climb and airspeed to your targeted stabilized number.  And if strip is paved that same approach would apply due to need to clear those 90' trees.

[GrassStripFlyBoy]

Here's a clip of climbing out hanging on the prop, note the airplane takes off and climbs out as the ASI is catching up.  I'd call this about as much STOL you can get on a CT, weight is everything in these birds.  If you're at gross and it's hot, those 90' trees are a risk.  Be very aware of your wieght.

Flying into Friends Yard - Landing and Flying - CT Flier Forum

[Tom Baker]

Here is a few pictures of my prop adjustment fixture. Very homemade, but is accurate to .1°. It is shown on a fixed pitch prop, because that is what was in the shop at the moment. 

[SkyMenace]

A better photo of my homemade Pitch Angle device as used would have shown the horizontal portion of the Machinist Square resting on the Prop Leading Edge and secured by a simple clamp.  I realize now I failed to shoot that arrangement.

[SkyMenace]

Numerous cool options.  Thanks for the photos.

 

[Roger Lee]

Hi Tom,

Nice prop tool. Definitely shows imagination that works well.

[Bill3558]

Grass strip Fly Boy,  be aware when your practicing engine outs, if your prop stops, glide goes to hell real fast. I don’t know exactly but I think I was coming down at about 1200 fpm at 65 knots when my engine seized. 

[Anticept]

A few knots is a huge deal. I have actually done flight tests with windmilling and complete stoppage.

For a CTLS, you want to be at -6 flats, and 73 knots. 78 knots in some manuals really is incorrect.

You can expect a decent rate with a windmilling prop to be about 850 to 900 ft per minute while at around 1100 lb. If you stop the prop, that descent rate slows To around 800 ft per minute. However, to actually stop the windmilling requires you to drop your airspeed to an extremely low value, which is going to severely impact your descent rate in the process for a time.

Please remember that weight of an aircraft has no bearing on glide speed or distance. The glide speed is fixed, it just means that you will hit the same ground point faster with the heavy load then if you had a light load.

[GrassStripFlyBoy]

Don't have the first hand experience of the prop stopping, the concern I was expressing is the situation of being climb attitude, low airspeed, loosing engine - and then having to transition to nose down / glide, when very close to the ground in a tight short strip with tall trees.  Not trying to diminish your points, simply clarifying this is not cruise flight at altitude, rather based on the question from SkyMenace of best speed for climb out.   Loosing the engine may quickly result in stall / spin without even getting to the point of considering what ASI and resulting best glide.  If you're at 52k in steep climb attitude, a hundred foot up, best glide is not in the equation. 

[Warmi]

The risk of engine suddenly going south is the main reason I rarely climb out at less than 60 knots … I would like to think that if that happens I will have enough presence of mind to push to stick forward right away but having a bit more airspeed in the bank can only help … that and the fact that I can’t see crap what is in front of me when climbing at such steep angles …

[Mike Koerner]

Corey,

I'd like to clarify one thing you said: The speed at which the maximum glide angle is achieved is sensitive to weight.

The maximum L/D (lift to drag ratio or glide angle) does not change with weight, but the speed at which it occurs goes up with weight. It increases by the square root of the ratio of weights. So, if you've determined your max glide speed is 73 knots at max gross, and you're flying alone and without baggage and low on fuel at 900 lbs instead, then your best glide speed will be 73 x (900/1320)^.5 = 60 knots.

That's an extreme case of course. And note that you will not glide any farther at lower weight. You'll end up in the same place whether heavy or light. But if you're light and flying at a lower speed, you'll have more time to consider your sins on your way down.

A rule of thumb is to reduce the maximum glide speed by 5% for every 10% you are below max gross. In the example above, you were at 68% of max gross, so the rule of thumb would suggest 16% lower speed or about 61 knots.

Maybe that speed difference is not enough to worry about. The L/D curve is flat near its maximum, so a little more or less speed probably isn't going to break any branches.

Wind, of course, will also come into play. Another rule of thumb is to increase speed by half the head wind component and decrease speed by 1/4 the tail wind component.

The inverse of this is to add weight when you want to glide fast. My sailplane holds 44 gallons of water. On strong summer days, I load it up until water is gurgling out the vents.

[Anticept]

This would be the first time I've heard about best glide speed changing with weights. Some references just simply state that heavier aircraft will arrive sooner at the crash point than lighter ones, which I expect, but there are a couple that mentions said glide speed actually does change (but not the glide angle).

[MEH]

I have found that reproducibility is key when adjusting the pitch of the props.  Here is how we have solved the reproducibility problem.  I covered the prop with clear packing tape and placed parting compound (paste wax) on it.  Using resin and fiberglass, I made a cast of the end of the prop.  The cast was easily removed and trimmed on the back side. We affixed a wooden block and a bit of steel.  The digital level is magnetic and sticks to the steel.  The arm is bolted to the open, threaded hole on the left front cylinder and is the reference to make each prop come to the same location.  It takes seconds to switch from prop to prop and easily reproducible allowing each prop to be adjusted to within 0.1 degree. Because the inside of the cast is very smooth, there is no damage/scratching of the prop blades.   It works well for us. 

[Roger Lee]

A Rubber band around the front of the blade holds it on just fine too.  

[sandpiper]

On 11/7/2021 at 6:34 AM, SkyMenace said:

 

Since you are so knowledgeable on the CTLS, could you help me out on nailing down the Optimal Takeoff/Climbout Speed over (what at my home strip, VA99) are 90’ trees at each end of the runway?

My AOI states Vx as 62 KIAS with 15’ Flaps.  Yet elsewhere I have read 51 -52 KIAS.  I have found 52 KIAS to work out well and within my comfort zone.  62 does not cut it for getting over the trees.  Or, perhaps, rather it would, cut the trees!

I have a RAM Checklist that states Vx with 15’ Flaps as 51 KIAS.

Which is it? Or rather, which do you recommend? 

RAM Checklist 1-stack.pdf 284.44 kB · 2 downloads

I have a 2007 CTSW. When I bought it, I found in the literature that Vx is 51K with flaps 15. That was about 15 years ago so I would have to do some digging to find that again.

I have never had to use that speed for real but I practice it a couple of times a year just to stay acquainted with it. I find it to be uncomfortable. Not because the plane isn't capable, but because if the engine quit at 50' AGL recovery is unlikely. 

My normal take off climb is flaps 15 at 60-62K until about 400' AGL, then Vy at flaps 0 (78K), then Vy at flaps -6 (86K).