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CTLSi Sport Upgrade


gbigs

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The loophose isn't IAS vs CAS they would be about the same.  I would argue that Rotax's 5,500 RPM limitation is  intended to be a 75% limitation.

 

Rotax does a poor job of limiting cruise settings to 75% and they use 5,500 RPM instead.  5,500 RPM doesn't reduce to 75% until 7,500'.  WOT @ 127kts @ SL is far above 75% and is not a cruise setting.  Pull back to a cruise setting and you will loose those 7 kts.

 

If you want to try and cruise at 123, 125 or faster (TAS) climb to 7,000 and do it with 75%.

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From FAR 1.2

VH means maximum speed in level flight with maximum continuous power.

From FAR 1.1

Rated maximum continuous power, with respect to reciprocating, turbopropeller, and turboshaft engines, means the approved brake horsepower that is developed statically or in flight, in standard atmosphere at a specified altitude, within the engine operating limitations established under part 33, and approved for unrestricted periods of use.

From FAR §33.5 Instruction manual for installing and operating the engine.

 

Each applicant must prepare and make available to the Administrator...

 

( B) Operation instructions.

 

(2) The power or thrust ratings...

From §33.8 Selection of engine power and thrust ratings.

 

(a) Requested engine power and thrust ratings must be selected by the applicant.

 

I am not claiming expertise, but based on the above and from what I've heard/read the manufacturer determines the maximum continuous operating power. We all know that aircraft such as the Cessna T210 and many other larger light aircraft and many WWII piston engine fighters had a takeoff setting or war emergency setting that allowed operation above maximum continuous power for 5 minutes or some other determined time. Someone who flew only C172s or FD CTSW may not be aware that maximum power and maximum continuous power are two different things. The idea that a manufacturer has the authority to "derate" an engine for continuous operation is not familiar to some who are used to running power settings just under red line for any length of time.

 

Whether the Carbon Cub has been "artificially" derated is not for me to say. :) However, the practice appears legal.

 

As far as an LSA being kicked out of the category, there were unconfirmed reports that a Sonex builder claimed to be an LSA, posted speeds significantly above 120 kts Vh on YouTube and was kicked out of the LSA category by the FAA. I have no proof of that, only passing on a rumor. Maybe some investigation in the Sonex type club sites would yield more info.

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As far as an LSA being kicked out of the category, there were unconfirmed reports that a Sonex builder claimed to be an LSA, posted speeds significantly above 120 kts Vh on YouTube and was kicked out of the LSA category by the FAA. I have no proof of that, only passing on a rumor. Maybe some investigation in the Sonex type club sites would yield more info.

 

As a former Sonex builder, I don't understand this...the Sonex is not IN an LSA category, it's E-AB.  As far as I know, Sonex has not submitted a factory example to the FAA to be exactly copied as an E-LSA, which would be a requirement.  Unless maybe copying the plans exactly qualifies.      

 

The Jabiru engine used in the Sonex is not a 3300, but a "3300A" whose maximum continuous RPM is derated from ~3200rpm to 2850rpm.  This is specifically done to make the Sonex Sport Pilot eligible.  The only difference in the two engines is the data plate, so you can do the math on how many pilots abide by the 2850rpm limitation.  

 

I'm sure the Carbon Cub's 180hp engine uses similar antics.  You can put a limitation on an airframe or engine, but you can't make pilots stick to it.

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The CTLS was tested to almost 160 knots, and they discontinued the test because it met cert requirements.

 

Usually max speeds are set with quire a bit of extra safety. The various speeds are likely the limit set because any more and it would cut into the margin of safety.

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The CTLS was tested to almost 160 knots, and they discontinued the test because it met cert requirements.

 

Usually max speeds are set with quire a bit of extra safety. The various speeds are likely the limit set because any more and it would cut into the margin of safety.

 

Interesting.  IIRC the Vne for the CTSW listed in the POH for Europe is 163kt.  I wonder why it's 145kt in the USA...higher chance of flutter because of the different flap settings keeping the flaperons more in the airstream?

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The answer is in the pages 100 posted. The 127kts is indicated airspeed, and the 120kt limit is calibrated airspeed. You can have both and still be in compliance.

 

True.

 

But airspeed indicators are calibrated to be most accurate at normal cruise speeds.

 

It's highly unlikely there would be anywhere close to a 7k difference in airspeed in that range.

 

There should be a IAS-CAS chart in the POH to put that one to bed.*

 

Interestingly, I don't see one. I thought there had to be one. Also not much in the way of cruise performance charts.

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There should be a IAS-TAS chart in the POH to put that one to bed.

 

Huh?  

 

IAS - TAS is about adjusting for conditions ( altitude, temp )

IAS - CAS is about removal of error ( like pitot tube at high AOA )

 

How would and IAS-TAS chart resolve the amount of IAS-CAS error?

 

I do agree 7kts shouldn't be there in cruise.

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Interesting.  IIRC the Vne for the CTSW listed in the POH for Europe is 163kt.  I wonder why it's 145kt in the USA...higher chance of flutter because of the different flap settings keeping the flaperons more in the airstream?

I think it has to do with the parachute, but not 100% on that.

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