Is there is spec for our prop pitch? Wikipedia says there is

[Ed Cesnalis]

http://en.wikipedia....light_Design_CT

 

'The CTSW is so efficient that it needs to have the pitch of the propeller reduced significantly to stay within the 120-knot (222 km/h) maximum speed of the American Light-sport Aircraft (LSA) rules'

 

I suspect the above quote is not correct and I think if we can verify that we should edit the Wikipedia content or at least challenge it

• The first reason I think it is suspect is that I have never seen a pitch limitation in my POH perhaps it wouldn't have to be there but since it is allegedly and important and significant limitation I think it would have to be there
  
• My speed is already limited via excess drag via limiting my reflex flaps.
  
• The language is wrong, it wrong it should read reduced pitch.
  
• Aren't CTs now delivered with flatter pitches?
  
• Excess load creates unnecessary engine wear.
  
• Excess load is a safety issue at altitude.
  
• The source seems to predate CTSWs and its Canadian Owners and Pilots Association, October 2004 - it seems to report on a CT2K and implies a resulting limitation on a CTSW
  

Is there a pitch specified in the maintenance manuals?

 

Anyone have a definitive answer on the pitch? Anyone experienced in editing Wikipedia?

[Jim]

I put a "citation needed" request after the statement on the Wikipedia article. It is now the author's responsibility to provide the cite.

[Roger Lee]

Quote and old thinking:(this conversation is only for ground adjustable and not the in flight adjustable props in other countries)

 

"The CTSW is so efficient that it needs to have the pitch of the propeller reduced significantly to stay within the 120-knot (222 km/h) maximum speed of the American Light-sport Aircraft (LSA) rules"

 

 

The pitch has no definitive setting and can legally be changed. To my knowledge the pitch can't be controlled by FD or any LSA Mfg. The pitch from FD years ago was set too course and only allowed 5200 rpm at WOT with no accounting on different field elevations or flight altitudes. This caused poor climb, cruise, fuel economy, engine stress and extra vibration. After some complaining from 1-2 people and Rotax they changed the pitch to achieve 5500 rpm. If they thought 5200 was right and it would achieve speed over 120 knots then 5500 was sure to do that. In the real world that really didn't happen for the ground adjustable planes. Now also consider that FD along with most other LSA MFG's state in their paperwork to follow the recommendations of Rotax. There are 3 types of props on the CT here in the US and others world wide. Neuform 2 and 3 blade, warp Drive and Sensenich. They're all different.

Pitch should be set with the aircraft, engine and altitude performance characteristics in mind. The exact pitch is whatever it takes to achieve your goal.

 

If you live and fly at sea level and never get over 2000' AGL verses someone that lives with a field elevation of 7100' and fly's at

11k-13K those prop pitch settings should always be different.

The CT is usually right at the speed limit for a balanced pitch setting that also allows good balanced performance for your specific flights.

Prop pitch other big considerations and affects from the prop pitch are engine temps, vibration, crank stress, fuel economy, climb, cruise speed. Planes with high temps can many times reduce prop pitch and workload and which help the cooling.

 

 

I actually remember when one member here on the forum changed his prop pitch from 5200 rpm WOT and then shouted, "Woodstock comes alive".

A balanced prop pitch is everything.

[C ICEY]

Which again begs the question, what are regulators protecting individuals from, in that they are prohibited against installing a variable pitch propeller on a CT in the USA?

 

Seems to me that an inflight adjustable or true constant speed is such a sensible (and indispensible) addition to these great little planes.

It is the essence of versatility to operate at optimum performance in all flight conditions.

why aren't you mad a he#?

 

mike

[Roger Lee]

Those regulators don't think us dumb Ole LSA pilots can manage or understand in flight adjustable props. :huh: (Bring'em on )

These planes are flown by private pilots, but also the original intention was for less educated LSA pilots to fly these planes. Don't confuse smart with less education. Private pilots have a 40 hr requirement and get more instrument, weather and radio and other flight info that a 20 hr. LSA student doesn't. So they drew the line in the sand on several LSA pilot items.

I see no reason that the FAA couldn't have made the variable pitch prop issue for the sport pilot a 1 hr. CFI sign off in the logbook and if you were a private pilot you were good to go or make it a sign off for everyone and cover all the bases.

 

The only problem with this idea is how do you decide what plane gets a variable pitch prop when it comes off the line. Do you make it an option? Make them an after market add on? All sounds good to me.

 

As you said it would make our LSA perform more closer to peak performance at different flight envelope times.

I don't ever see this changing for the LSA plane in the US.

[mocfly]

Here we go again.

 

i have a neuform prop on 530ct and the manual has a angle to adjust to based on using the nueform gauge.

 

There is also a disclaimer which states.

 

The Angle of Incidence

 

For microlight aircraft, that are type registered, the angle of incidence s defined in the registration must be adjusted.

 

The figure for the angle of incidence must be obtained from the microlight aircraft manufacturer if necessary.

 

For experimental aircraft and microlight aircraft, that need to be tested, standard and recommended figures can be obtained from Neuform,

 

NOTE:

 

Faulty propeller adjustments lead to losses in performance ( I can see Roger smiling) and therefore can cause accidents. They can also cause unnecessary high noise emissions.

 

We warn against tests with anything other than the recommended adjusting figures.

 

FYI

Our prop is set to 11.750 deg.

 

 

Just in case someone wants to say a microlight isn't an LSA

 

The US definition of an LSA is similar to some other countries' definition of "microlight" or "ultralight" aircraft. Except for the LSA's relatively generousMTOW of 1320 pounds, the other countries' microlight definitions are typically less restrictive, not limiting airspeed or the use of variable-pitch propellers.

[Ed Cesnalis]

Thanks Chris,

 

I don't have a Neuoform so I don't have that limitation. Warp drive manual is silent.

 

Can you provide a max RPM and does your setting match the spec?

 

Does Neuform continue to provide this limitation on new CTs? Seems that a new CT is faster than how a 2006 was delivered have they reduced the limitation?

 

This brings the Rotax document to mind that says 5,500 RPM is best practice for cruising. Which document would supersede?

[FastEddieB]

My Sky Arrow Maintenance Manual gives a certain pitch setting for its Warp Drive prop, expressed in degrees at a certain blade station.

 

I was not getting quite 5,000 rpm on takeoff and initial climb. After I was Experimental, I dialed in 1° less and now get about 5,300 rpm, giving much better performance.

 

Pretty sure my cruise performance has suffered a bit, needing more rpm and fuel flow for any given airspeed.

[Roger Lee]

Remember that many manuals like Rotax and others are usually written for not just the US use, but world wide. So unfortunately there is some interpretation and some things are also lost in the translation from one language to another. Rotax is a perfect example. Here in the US a company can tell you what prop to use, but they can't legally tell you a pitch setting. That would mean they could also tell you how to accomplish a maint task. They can tell you what maint. is to be performed, but can't tell you how to do it. Also remember our post on prop use. If a prop was listed in the manuals as an option for your year aircraft then you don't need an LOA to use it. Prop pitch's in manuals are good starting points, but each plane may live in different elevations and have very different needs for different flight characteristics.

 

 

Hi Eddie,

You have a better climb prop now, but lost some top end. I would bet your WOT in flat and level is above 5800 rpm? It isn't any big deal, just what the end user wants out of his plane for certain flight characteristics.

 

Hi Chris,

 

I wouldn't get to hung up on what the book says about prop pitch. I find factory delivered aircraft as much as 1 degree off between blades. That would mean FD would have been in violation of their own manual.

[Ed Cesnalis]

Its all clear as mud to me now. I'll say this, with other means available such as limiting flaps, or even just level IAS limiting prop performance through pitch is a dumb way to go and has unintended consequences.

 

For LSA certification I'm not at all clear on how or even if speed is limited.

[Roger Lee]

The only speed that FD had to worry about for the US CT's was the 45 knot stall and the 120 knot max speed. This applies of course to all LSA.

[Ed Cesnalis]

The only speed that FD had to worry about for the US CT's was the 45 knot stall and the 120 knot max speed. This applies of course to all LSA.

 

It seems pretty clear that the -6 limitation is about the 120kt limit. Certainly the Neuform reads as though a pitch spec is used to comply with the 120kt limit. What is FD relying on for compliance for certification? Air frame is slow enough or limiting flaps alone or flaps and prop pitch?

 

Is this info that we are not privy to?

[Roger Lee]

Hi Ed,

The -12 for us is more about the stall speed. I know several that have -12 and their top speed tends to be fairly equal to -6 so long as the WOT rpm is the same and the weight. Weight is a major factor for us. This is from actual test. I don't always put a lot of stock in manual specs. They can be off quite a bit because they test only under certain conditions and weights. I'm more of a real world type tester and believe in side by side comparisons which most MFG's don't do. And for them there is no need to do. They only need to show compliance with certain regs.

 

[Ed Cesnalis]

Your right, I forgot, -12 exceeds max stall speed.

 

The rest remains clear as mud to me. Do any or all CT LSA have a speed limiting limitation that was used to get LSA certification?

 

If prop pitch was used then logic would say that there are some restrictions on optimizing prop pitch. If prop pitch wasn't used than lacking any limitation from the prop manufacturer I would guess we are free to optimize.

 

It is an interesting question from a couple of perspectives. For instance if the CTLSi had its speed limited ( technically ) in such a manner than claims to additional speed, or at least any speed above the limitation if it is artificial become less valuable.

 

At this point I would assume that If I am in formation with a CTLS, at altitude and we are both 131kts TAS that I am likely not violating any limitation while the CTLS with the Neuform might be. We are at that speed, due to less drag at altitude, cold winter day makes the Rotax stronger and buys 5 kts, and an optimized prop.

[chanik]

120kts at sea level http://www.law.cornell.edu/cfr/text/14/1.1

-10 deg seems to add about 2.5kts by my estimation. In your case, it also makes you safer in all that mtn turbulence since it adds ~4kts to the stall speed. That's 10kts more in max maneuvering speed, Va

[paul m]

Adding the exact language from Kurt's link:

 

(2) A maximum airspeed in level flight with maximum continuous power (VH) of not more than 120 knots CAS under standard atmospheric conditions at sea level.

 

Doesn't the Carbon Cub play wih this language to hang that engne on it?

[WmInce]

. . . "Doesn't the Carbon Cub play wih this language to hang that engne on it?"

 

At this year's LSA Expo - Sebring, I ask that same question to Cub Crafter's Chip Allen. He told me that the Carbon Cub SS prop was pitched at the factory, so as NOT to exceed the 120 knot LSA rule.

 

I think that is one of the reasons why the climb performance of that aircraft is so spectacular.

[Tom Baker]

It was my understanding that the reason for the reduced power placard for the Carbon Cub is because of weight issues. For ASTM complience you have to be able to carry a 180-190 pound person per seat (I don't remember the exact number, but it is more than the FAA 170 figure), and 1 pound of fuel for each max continuous HP to meet the minimum useful load requirement. If the number is 180 and the engine was 180hp then they would need to have a 780 pound empty weight. By making it 80 hp continuous they gained 100 pounds of empty weight they could use.

[S3flyer]

And I'm sure nobody exceeds the placarded RPM.....

[Adam]

The Carbon Cub has a massive engine with crap fuel efficiency. Thats why it climbs fast. THe engine is twice the weight of the Rotax 912i at 250 pounds, and is rated at 180 horsepower for takeoff and climb, and 80 horsepower for continuous power settings

 

Comparing a Carbon Cub to a CTLSi is like comparing an Apple to an Orange

 

Each has a place in the aviation community. In the bush, off airport in a place like Alaska, this is why you buy a Carbon Cub! In aviation you get a license that meets your mission, and you fly a plane that fulfills that mission (in my humble opinion).

 

 

 

 

The Carbon Cub is an AWESOME STOL aircraft! (and when you get the plane certified not as an LSA it can haul whatever you can fit in it).

[Jim]

http://en.wikipedia....light_Design_CT

 

'The CTSW is so efficient that it needs to have the pitch of the propeller reduced significantly to stay within the 120-knot (222 km/h) maximum speed of the American Light-sport Aircraft (LSA) rules'

 

I suspect the above quote is not correct and I think if we can verify that we should edit the Wikipedia content or at least challenge it

• The first reason I think it is suspect is that I have never seen a pitch limitation in my POH perhaps it wouldn't have to be there but since it is allegedly and important and significant limitation I think it would have to be there
  
• My speed is already limited via excess drag via limiting my reflex flaps.
  
• The language is wrong, it wrong it should read reduced pitch.
  
• Aren't CTs now delivered with flatter pitches?
  
• Excess load creates unnecessary engine wear.
  
• Excess load is a safety issue at altitude.
  
• The source seems to predate CTSWs and its Canadian Owners and Pilots Association, October 2004 - it seems to report on a CT2K and implies a resulting limitation on a CTSW
  

Is there a pitch specified in the maintenance manuals?

 

Anyone have a definitive answer on the pitch? Anyone experienced in editing Wikipedia?

 

 

After the usual Wikipedia editing silly walk, I got the author of the article to remove that sentence. He said it was from a CT2K review and he could not find any substantiating references.

[Ed Cesnalis]

After the usual Wikipedia editing silly walk, I got the author of the article to remove that sentence. He said it was from a CT2K review and he could not find any substantiating references.

 

Good Job Jim!