Could Someone Give me Advice on Optimizing CTLS Performance for Long Flights?

[lanawatsonn]

Hello there,

I have been a proud owner of a CTLS for about two years now; and I have enjoyed every moment of flying this fantastic aircraft. Although; as I have started planning longer cross-country flights; I am looking for ways to optimize the performance and efficiency of my plane. Specifically; I am interested in improving fuel efficiency, handling, and overall comfort during extended trips.

What techniques or modifications have you found most effective in improving fuel consumption? I've heard mixed opinions on power settings and propeller pitch adjustments. Any real-world data or personal experiences would be invaluable.

How do you manage weight distribution for optimal performance; especially when carrying extra baggage for long trips? Any tips on maximizing storage space while keeping the aircraft balanced?

Long hours in the cockpit can be challenging. What are your go-to modifications or additions to enhance comfort? This could include seat cushions, noise reduction techniques, or any other comfort focused upgrades.

How do you approach weather forecasting and route planning for cross country flights in a CTLS? Any specific tools or resources you rely on?

What preventive maintenance practices do you prioritize before a long journey to ensure a smooth and trouble free flight?

Also; I have gone through this post; https://www.ctflier.com/topic/5645-new-ctls-owner-needs-ccsp-landing-advice/ which definitely helped me out a lot.

I am keen to hear from both seasoned pilots and newer CTLS owners who might have fresh perspectives. Your shared experiences and tips will not only help me but also benefit others in our community who are looking to make the most out of their flights.

Thank you in advance for your help and assistance.

[FlyingMonkey]

Efficiency and fuel consumption is always a trade off.  From the CTLS POH:

Efficient cruise performance is achieved at about 4800 rpm. Greater rpm means
greater airspeeds but this can only be achieved at the expense of much higher fuel
consumption. The greatest range is achieved at the relatively low value of 4300 rpm.

I think this is correct and corresponds well to the Rotax manual, which I think lists best fuel economy around 4600-4800rpm.  The big questions become "how efficient do you want to be?" and "how much time do you have?"  You can get the fuel burn to less than 4gph, but will you be happy doing a 300nm leg at 90kt IAS or less?  I don't think any CT pilot is going to fly long distance at 4300rpm and 85kt.  The best travel experience for me is between 5000rpm and 5400rpm. 

5000rpm you can still get decent speed, the engine runs quietly which is less fatiguing, and fuel economy is very good.

5200rpm you get a little better speed and economy only goes down slightly.  This is probably the best speed/economy setting for long distance flight.

5400rpm is slightly faster still but the fuel burn goes up quite a bit.

Anything higher than 5400rpm makes a lot of noise and burns much more fuel, and gives very little additional speed.

I use 5000rpm for general cruising around or longer flights where I'm in no hurry or enjoying the scenery, and 5200rpm for normal cross-country cruise.  I go to 5300rpm if I'm trying to get somewhere a little faster and 5400rpm if I need to beat weather or am really in a hurry.  This has worked well for me for a number of years; I just don't have the patience to cruise at 4800rpm and very slow speed to save a gallon or two of fuel over a long distance.

 

[FlyingMonkey]

For comfort, I put some inflatable lumbar cushions under the seat covers that I can pump up to help my aging back.  These are the ones I have used for years:

https://www.aircraftspruce.com/catalog/pspages/inflatelumbar.php?clickkey=22205

The thinner/smaller shoes you wear, the more positions you can put your feet in to relieve cramps and stress.  Flying in socks with soles or Japanese tabi might be the best over long distances.  If you wear clunky boots you really limit what you can do with your feet.

I don't pay much attention to weight distribution other than making sure not to overload any weight station.  The CT has a very forgiving Cg envelope and I don't think the "lemon is worth the squeeze" to to try get better efficiency in moving things around other than obeying basic valid W&B configurations.
 

[Eddie Cesnalis]

I fly out west so a WOT @ 5,500 RPM pitched for cruising high works best for me.  It gives me the added bonus of enhanced climb rates down low as well as good cruise speed while throttled back.

I have found my best performance at 13,000' @ 5,500 and WOT.  There isn't much hp available at and above 10,000 so lower RPM doesn't buy you much.  The lower drag lower power combination seems to provide best performance at good economy.   

If you fly in the east it might not make much sense.

[Anticept]

Ser RPM for 100 knots, -6 flaps, assuming no headwind, and it will give you the best distance. It's called the Carson Number and it's applicable to all conventional aircraft. Any faster or slower in no wind conditions will decrease distance.

If you have a headwind, its a bit of fiddling to find what the best power setting over the Carson Number is needed. Headwind slows ground speed and will cause you to spend more time flying, which means more time using fuel. However, there won't be a lot of power increase before the increase in drag outweighs the decrease in flight time.

Takeoff: get to a safe altitude to turn back, then power back to a gentle climb of 300-500 feet a minute. The aircraft weight is a factor here so no specific power setting is an answer. The important point is to get out of the full rich position of the carbs/fuel controller.

Monitor wind patterns at various altitudes. Pick the one that gives you the greatest forward groundspeed (headwind and 2% per thousand rules apply). You might change altitudes from time to time.

Also, check wind patterns. Very long trips actually make it worthwhile to look at the cyclonic activity and to plan your route so that you get more favorable winds. It can, and I have done this, make HOURS of difference on journeys to reroute even though it might add a hundred miles to the trip.

For descent: at idle power, these aircraft descend at about 800 feet a minute at best glide. So ideally you plan your descent so that you remain in favorable conditions as long as possible, then power chop and descend. DO NOT drop into a pattern, aim for pattern altitude 3-4 miles from the airport. You won't shock cool a rotax (its hard to shock cool anything but chop and drops like this can do it) so don't worry.

Generally, more preferred would be sticking to a 500 foot decent rate. Nice thing is, its easy to calculate TOD. Take your altitude, subtract the target altitude, double the result, and move the decimal three places (basically just read the thousands and ten thousands place). That's the time it takes in minutes to descend/climb at 500 feet a minute... Add a few minutes and wait until your GPS's time to destination or time to next waypoint says that and do the maneuver.

[shiny.ice]

1 hour ago, Eddie Cesnalis said:

I fly out west so a WOT @ 5,500 RPM pitched for cruising high works best for me.  It gives me the added bonus of enhanced climb rates down low as well as good cruise speed while throttled back.

With the 912iS I typically run at 97% throttle, as above that the computer goes into open-loop mode (eg too rich). The higher the better for fuel consumption, I typically go at 8500/9500 unless the headwinds (or terrain) favor something else.

 If I want more range I’ll throttle back, I keep a nm/gallon number on the Dynon so I can choose the trade off I want. But at under 4gph it’s usually pretty close to 97%!

[Eddie Cesnalis]

23 minutes ago, shiny.ice said:

But at under 4gph it’s usually pretty close to 97%!

wow, that seems to be a 1 gallon per hour improvement. (over carberated 912uls)

[FredG]

 

8 hours ago, Anticept said:

Ser RPM for 100 knots, -6 flaps, assuming no headwind, and it will give you the best distance. It's called the Carson Number and it's applicable to all conventional aircraft. Any faster or slower in no wind conditions will decrease distance.

Corey, as you know, the Carson number is the best glide speed multiplied by the value 1.316.  100kts divided by 1.316 equals 76 kts.  How did you identify 76kts as the best glide speed at -6 deg flaps for the CTls?  Is that a published value? (I own a CTsw and the best glide at -6 deg flaps is not provided in the Aircraft Operating Instructions (POH)).  I would be curious what the Carson number is for the CTsw. 

[Eddie Cesnalis]

My high altitude cruise uses the Carson number approximately.   Carson number IAS @ Wot @ ~12,000' will  increase the speed an impressive 52 percent for that same 16-percent rise (over best economy/glide) in fuel consumption.

[Eddie Cesnalis]

WOT at Carson number happens at the altitude that your prop is currently pitched for.  Adjust the prop pitch to cruise at Carson number @ WOT at your desired altitude and get up to a 52% improvement over the 16%

[Anticept]

16 hours ago, FredG said:

 

Corey, as you know, the Carson number is the best glide speed multiplied by the value 1.316.  100kts divided by 1.316 equals 76 kts.  How did you identify 76kts as the best glide speed at -6 deg flaps for the CTls?  Is that a published value? (I own a CTsw and the best glide at -6 deg flaps is not provided in the Aircraft Operating Instructions (POH)).  I would be curious what the Carson number is for the CTsw. 

Chart is in the AOI for the LS. It also says it for 0 and -6, but recommends best glide using 0 degrees in the paragraph on the prev page.

It's a nice round number. 64 to 78 are the best glide numbers depending on weight and chances are people are close to the 1320 (78) limit.

100 is close enough. And since SW and LS are similar enough, you should be fine too. You can always tweak.

[Anticept]

14 hours ago, Eddie Cesnalis said:

WOT at Carson number happens at the altitude that your prop is currently pitched for.  Adjust the prop pitch to cruise at Carson number @ WOT at your desired altitude and get up to a 52% improvement over the 16%

Please be aware that the climb can also negate your savings. Plan with fuel consumption and correct ground speed during the climb.

I found that for trips less than a couple hours, only winds made a significant enough of a difference to climb to high altitudes from where we are in the lowlands. For you it's a little different with all those mountain winds!