NEUFORM Prop Pitch

[Ed Cesnalis]

Nope. I'll keep it as it is for now, and hope it can provide insight to others.

 

Your choice,  I see the Rotax as a different animal and the prop pitch question has 2 additional variables that no-one includes in the discussion but me.

 

1. Leaning is limited and no economy power setting is available above 92% throttle.  This is not true in a lycoming or Continental or any traditional aircraft engine with a mixture control.  With my skyhawk I could access all available power by leaning for best power even at throttle settings between 92% and 100%  The additional question posed by the full rich limitation is Do I want access to all available power or will I accept less power in order to bring the needle circuit and its economy into play? (This is a question that comes into play at higher altitudes like above 7,500'.
2. Rotax limits power (redline) via RPM and not actual power settings. Our prop pitch and our cruise altitudes are variables.  You could select a cruise power setting above 75% by limiting cruise altitude and using enough pitch.  With a variable pitch prop an RPM limitation provides a different level of protection than a percentage of power limitation. It would be fun to have the fastest CT cruising the beach but perhaps pitching for this is a bad idea while not prohibited by the 5,500 continuous limitation.

[Anticept]

Your choice, I see the Rotax as a different animal and the prop pitch question has 2 additional variables that no-one includes in the discussion but me.

 

• Leaning is limited and no economy power setting is available above 92% throttle. This is not true in a lycoming or Continental or any traditional aircraft engine with a mixture control.

Edit: apologies for saying it is incorrect. Got ahead of myself on this

 

Both lycoming and continental use enrichment valves in carbureted engines, and economizer (no idea why it's called this, because it dumps MORE fuel) in fuel injected engines, that open above a certain throttle setting in carbureted and fuel injected engines and force a richer mixture.

[Doug G.]

I'm not sure, but I think you both said the same thing from different directions. ?

[Doug G.]

Rotax - no leaning (as in mixture adjustment - except by modifying the needle setting in the carb - not in flight).

- no economizer circuit. That is what I got from both of you.

[Ed Cesnalis]

This is incorrect. Both lycoming and continental use enrichment valves in carbureted engines, and economizer (no idea why it's called this, because it dumps MORE fuel) in fuel injected engines, that open above a certain throttle setting in carbureted and fuel injected engines and force full rich.

 

When you take-off from our field which will likely have over 9,000' density altitude if you don't lean for best power and have less than 200hp you will be lucky to outclimb the terrain.  Most crashes here come from full-rich take-offs.

 

Most of us do the lean at run-up and we do it at full throttle.  The result is that RPM will increase a dramatic amount as you lean. You say at a certain setting we are full rich yet we need our mixtures out 2 fingers ( thats a lot of turns ) to find max RPM and best power.  How can that work if the system defaults to full rich?

[Ed Cesnalis]

Rotax - no leaning (as in mixture adjustment - except by modifying the needle setting in the carb - not in flight).

- no economizer circuit. That is what I got from both of you.

 

The needle circuit only has control for a certain throttle range, in that range there is leaning due to pressure differential acting on the piston and raising/lowering the needle.  At WOT it is full rich.  The 912i mimics this and goes full rich at 92% throttle, below 92% is called econo-mode or something like that.

[Doug G.]

OK, I was under the impression the conversation was about carburated engines.

[Anticept]

When you take-off from our field which will likely have over 9,000' density altitude if you don't lean for best power and have less than 200hp you will be lucky to outclimb the terrain. Most crashes here come from full-rich take-offs.

 

Most of us do the lean at run-up and we do it at full throttle. The result is that RPM will increase a dramatic amount as you lean. You say at a certain setting we are full rich yet we need our mixtures out 2 fingers ( thats a lot of turns ) to find max RPM and best power. How can that work if the system defaults to full rich?

I thought about it after I had posted. I am incorrect in the fact that I said full rich. These valves act to greatly increase fuel mixture past a certain throttle point, likely for low altitude flight to help with the high air pressure.

 

I will have to dig out the old manual and read what it says about those valves.

[Ed Cesnalis]

OK, I was under the impression the conversation was about carburated engines.

 

The injected 912 mimmicks the carbed 912.  They both go full rich at 92% throttle or above.

[Farmer]

Right or wrong I am not sure, this summer on a long cross country trip with my CTLSi I found myself setting the engine, during cruise on the fuel flow numbers.  This seemed easier than looking for a certain RPM.  The Dynon will in a fairly short period of time  also indicate a range remaining number that helps, at least until something changes.  The problem was to keep engine turning as fast as possible while extending range to a  reasonable number.  The need for RPM was driven by the use of only 100LL, with Declin of course.  The numbers that worked best was a range of 3.5/3.7 gal per hour.  Beyond that the flow would jump about 22% or more, with very little middle ground in settings.  Push the aircraft and spend the injected engines advantage to nil.  This system worked for all air density or altitude of course.  Welcome any commets about any better system to solve range issue that does not  involve risk of "hiking out".

 

Have a nice day

Farmer

[FlyingMonkey]

Right or wrong I am not sure, this summer on a long cross country trip with my CTLSi I found myself setting the engine, during cruise on the fuel flow numbers.  This seemed easier than looking for a certain RPM.  The Dynon will in a fairly short period of time  also indicate a range remaining number that helps, at least until something changes.  The problem was to keep engine turning as fast as possible while extending range to a  reasonable number.  The need for RPM was driven by the use of only 100LL, with Declin of course.  The numbers that worked best was a range of 3.5/3.7 gal per hour.  Beyond that the flow would jump about 22% or more, with very little middle ground in settings.  Push the aircraft and spend the injected engines advantage to nil.  This system worked for all air density or altitude of course.  Welcome any commets about any better system to solve range issue that does not  involve risk of "hiking out".

 

Have a nice day

Farmer

 

That makes sense to me.  It seems if you set your cruise based on fuel flow, while also keeping an eye on airspeed, you could easily get very close to either best range (distance flown on a existing fuel) or best endurance (longest time aloft on existing fuel) if either were your goal.

 

I have often said the only instrument I wish my CT had but doesn't is a fuel flow gauge.

[Anticept]

... They are cheap...

[FlyingMonkey]

... They are cheap...

 

Until you add labor and the stupid "engineering study" that Flight Design will require.   :angry:

[Anticept]

Oh right, ctsws didn't have fuel flow as an option, did they?

[FlyingMonkey]

Oh right, ctsws didn't have fuel flow as an option, did they?

 

I think just the one built into the D-120 EMS.  I don't think there was an option for an analog FF gauge.

[Ed Cesnalis]

Don't you need a transducer? 

[Ed Cesnalis]

First you state that I am incorrect when I am correct.

 

Then when you realize that I am right you confess to being incorrect too.  Actually you are alone and should take back the correction to my post.

 

At WOT we lean for best power when flying behind a lyc, conti, franklin, etc and it works, period.

 

High altitude ops without leaning for best power are dangerous and often lead to departure crashes.  

 

It would be interesting to lean a Rotax for best power and see how much power we give up for the sake of full rich protection at WOT.

 

 

This is incorrect. Both lycoming and continental use enrichment valves in carbureted engines, and economizer (no idea why it's called this, because it dumps MORE fuel) in fuel injected engines, that open above a certain throttle setting in carbureted and fuel injected engines and force full rich.

 

 

I thought about it after I had posted. I too am incorrect in the fact that I said full rich. These valves act to greatly increase fuel mixture past a certain throttle point, likely for low altitude flight to help with the high air pressure.

I will have to dig out the old manual and read what it says about those valves.

[FlyingMonkey]

Don't you need a transducer? 

 

Yes.  I did some research, and asked Dave Armando at FD about it.  He said that the engineering has already been done previously, so I just need to pay $150 to FD to file and record the MRA for my airplane.  

 

I can get a fuel totalizer and the FD-recommended FT-60 transducer together for $369 at ACS.  That will give me fuel flow accurate to 0.1gph, fuel used, fuel remaining, endurance, and it even runs a wire to GPS to give you MPG and range.  Way more than the sight tubes tell me.      I think my A&P would let me "owner assist" on this work, so I could probably get it done all in for $700-800.  

 

That's more than I want to spend at the moment for "nice to have but not strictly required" work, but I'm filing this in the future wishlist for the CT.

 

EDIT:  It will cost more money than figured above if I need a new breaker and can't piggy-back off an existing one.

[Anticept]

First you state that I am incorrect when I am correct.

 

Then when you realize that I am right you confess to being incorrect too.  Actually you are alone and should take back the correction to my post.

 

At WOT we lean for best power when flying behind a lyc, conti, franklin, etc and it works, period.

 

High altitude ops without leaning for best power are dangerous and often lead to departure crashes.  

 

It would be interesting to lean a Rotax for best power and see how much power we give up for the sake of full rich protection at WOT.

Easy charlietango, i am typing from an iphone and sometimes when i fat finger, words get inserted when i misspell. That "too" was not supposed to be there, it was supposed to be "think".

 

I apologize for offending

[ctfarmer]

What have i noticed in my CTLS (now with 50hrs TT and -12 flap setting). 

 

I started adding pitch in ~1.5 deg steps with the last at 2deg. It was set up accurately with a jig and digital inclinometer. I have done 3 steps.

When i started my initial takeoff rpm was around 5500rpm which has steadily reduced to about 4900 now. My speed has progressively increased from about 105kts TAS at 5000 and 13.5l/hr to 116+kts at 5000 at around 18l/hr. I now see aroubd ~123kts TAS at around 5300 and a fuel burn of 20 to 21l/hr at approx 540kg all up weight and 6000' density altitude. My WOT test done immediately after taking this photo yesterday was 5450rpm. Speed at WOT was over 125kts.

 

Air turbulence was nil.

 

After reading these posts i will go back a little finer on pitch to see what happens but based on what i have found so far with my CTLS at -12 flaps, i will drop top end speed which goes against the consensus in this wise forum. I do not understand why 

 

[ctfarmer]

What have i noticed in my CTLS (now with 50hrs TT and -12 flap setting). 

 

I started adding pitch in ~1.5 deg steps with the last at 2deg. It was set up accurately with a jig and digital inclinometer. I have done 3 steps.

When i started my initial takeoff rpm was around 5500rpm which has steadily reduced to about 4900 now. My speed has progressively increased from about 105kts TAS at 5000 and 13.5l/hr to 116+kts at 5000 at around 18l/hr. I now see aroubd ~123kts TAS at around 5300 and a fuel burn of 20 to 21l/hr at approx 540kg all up weight and 6000' density altitude. My WOT test done immediately after taking this photo yesterday was 5450rpm. Speed at WOT was over 125kts.

 

Air turbulence was nil.

 

After reading these posts i will go back a little finer on pitch to see what happens but based on what i have found so far with my CTLS at -12 flaps, i will drop top end speed which goes against the consensus in this wise forum. I do not understand why 

 

[ctfarmer]

What have i noticed in my CTLS (now with 50hrs TT and -12 flap setting). 

 

I started adding pitch in ~1.5 deg steps with the last at 2deg. It was set up accurately with a jig and digital inclinometer. I have done 3 steps.

When i started my initial takeoff rpm was around 5500rpm which has steadily reduced to about 4900 now. My speed has progressively increased from about 105kts TAS at 5000 and 13.5l/hr to 116+kts at 5000 at around 18l/hr. I now see aroubd ~123kts TAS at around 5300 and a fuel burn of 20 to 21l/hr at approx 540kg all up weight and 6000' density altitude. My WOT test done immediately after taking this photo yesterday was 5450rpm. Speed at WOT was over 125kts.

 

Air turbulence was nil.

 

After reading these posts i will go back a little finer on pitch to see what happens but based on what i have found so far with my CTLS at -12 flaps, i will drop top end speed which goes against the consensus in this wise forum. I do not understand why 

 

[ctfarmer]

What have i noticed in my CTLS (now with 50hrs TT and -12 flap setting). 

 

I started adding pitch in ~1.5 deg steps with the last at 2deg. It was set up accurately with a jig and digital inclinometer. I have done 3 steps.

When i started my initial takeoff rpm was around 5500rpm which has steadily reduced to about 4900 now. My speed has progressively increased from about 105kts TAS at 5000 and 13.5l/hr to 116+kts at 5000 at around 18l/hr. I now see aroubd ~123kts TAS at around 5300 and a fuel burn of 20 to 21l/hr at approx 540kg all up weight and 6000' density altitude. My WOT test done immediately after taking this photo yesterday was 5450rpm. Speed at WOT was over 125kts.

 

Air turbulence was nil.

 

After reading these posts i will go back a little finer on pitch to see what happens but based on what i have found so far with my CTLS at -12 flaps, i will drop top end speed which goes against the consensus in this wise forum. I do not understand why 

 

[ctfarmer]

What have i noticed in my CTLS (now with 50hrs TT and -12 flap setting). 

 

I started adding pitch in ~1.5 deg steps with the last at 2deg. It was set up accurately with a jig and digital inclinometer. I have done 3 steps.

When i started my initial takeoff rpm was around 5500rpm which has steadily reduced to about 4900 now. My speed has progressively increased from about 105kts TAS at 5000 and 13.5l/hr to 116+kts at 5000 at around 18l/hr. I now see aroubd ~123kts TAS at around 5300 and a fuel burn of 20 to 21l/hr at approx 540kg all up weight and 6000' density altitude. My WOT test done immediately after taking this photo yesterday was 5450rpm. Speed at WOT was over 125kts.

 

Air turbulence was nil.

 

After reading these posts i will go back a little finer on pitch to see what happens but based on what i have found so far with my CTLS at -12 flaps, i will drop top end speed which goes against the consensus in this wise forum. I do not understand why 

 

[Ed Cesnalis]

If  I read your post correctly and you are currently WOT 5,300 RPM then  you can look at the power curve chart and see to access max continuous power you need more RPM.

 

If you have been increasing pitch ~1.5 deg steps with the last at 2deg, then unlike an old CT you began too flat for max cruise and went past max cruise and are now just a little too coarse. You can increase speed this way and have a little more left by decreasing pitch a little.