6 degree vs 12 degree flap setting

[NC Bill]

I presume the reason US registered FDCTs are restricted to -6 degrees is to reduce a/s.

 

What's the difference in a/s between the European -12 and a US -6 CT?

[Runtoeat]

Some general thoughts on the discussion of "tweaking" flap travel. We all enjoy our priviledge of flying as Sport Pilots due to a lot of hard work by individuals to convince the FAA that this sport would be a "self governing" organization. A set of rules were drawn up, hashed over by the Light Sport founders and the FAA, and then after taking a leap of faith that this self governing Light Sport aviation group would follow these rules, the FAA approved the rules. I consider myself very fortunate to be able to fly without the encumbrances of mandatory medicals, the added training required for nite flight and instrument flight and I especially enjoy the fact that I can fly an airplane that does not require TSO'd equipment since this translates into some of the cheapest flying, especially if one wants to find an old classic such as a cub or Aeronca, etc. We are a truely fortunate group to enjoy our freedoms. With these freedoms though, comes a committment to follow the rules. The problem with following the rules is that we are seldom checked on our faithfullness by the authorities and can sometimes go astray by thinking that we are not being watched. I say "seldom checked" because I know of at least one instance where a Light Sport pilot was "ramp checked" for compliance to the Light Sport rules by an FAA agent. I won't go into details because I really don't have all of the details but suffice to say that the some changes were made to his airplane that were not in compliance with Light Sport rules and the cost to get things straightened out would end most Light Sport pilots ability to fly.

 

Personally, I try to follow all Light Sport rules regarding flight and maintenance of my airplane and to not deviate from the original design or intent of it's manufacture. I want to make sure that when the FAA looks at the statistics each year to see if this experiment called "Light Sport" is holding up under the bright lights, it continues to demonstrate that their decision to allow a group of fliers to excercise the priviledge of Sport Pilot flying has resulted in a system that works well and that it is a safe system.

[Tom Baker]

I presume the reason US registered FDCTs are restricted to -6 degrees is to reduce a/s.

 

What's the difference in a/s between the European -12 and a US -6 CT?

 

Bill, it has to do with the clean stalling speed. Our stall speed with -6 flaps is 44kts if you go to -12 the stall speed is greater than the 45kts allowed by the regulations. This is taken from CFR 1.1 .

Light-sport aircraft means an aircraft, other than a helicopter or powered-lift that, since its original certification, has continued to meet the following:

4) A maximum stalling speed or minimum steady flight speed without the use of lift-enhancing devices (VS1) of not more than 45 knots CAS at the aircraft's maximum certificated takeoff weight and most critical center of gravity.

For us making the change would mean the airplane meets the requirements of a LSA. Tom

[Tad Olmsted]

If we were in Europe and the flaps were set at -12, you could expect to cruise at 140. If we were in Europe....

[bseager]

If we were in Europe and the flaps were set at -12, you could expect to cruise at 140. If we were in Europe....

 

In Canada we are allowed the -12 flap setting and constant speed or variable pitch props. I can get about 140 TAS. Under the rules up here there is no speed or altitude restrictions but weight is limited to 1232 lbs.

[Jim Meade]

If we were in Europe and the flaps were set at -12, you could expect to cruise at 140. If we were in Europe....

 

140 what?

[Tad Olmsted]

OOPS... 140 MPH

[NC Bill]

Is that 140 MPH or Kts?

[S4Flier]

Other than the "I want to go to -12 because it's there" reason, I can see no material advantage in being able to change the max setting on the CT's flaps from -6 to -12. The speed difference will be about 8% -- assuming the Canadian performance numbers are evenly split between controllable prop and flap setting. This is probably being generous. The 100lb weight difference needs to be factored in as well but I'm ignoring that one

 

Most CT's seem to be able to get around 120kts at altitutde with 5300+ rpm. So -12 should get 130 kts. Not bad. But it really has no practical effect on cross country times. Assume no wind, ignore the pattern and a 260nm trip takes 2hrs at -12 vs. 2:10 with -6. Not going to change your life. Sit back, relax and enjoy the flight!

[sandpiper]

Sometimes I don't like the sport pilot rules. After all, I've been flyng at night, IFR, faster than 120K, more than 1320#, constant speed prop, retractable gear, etc for over 40 years. So, why not a constant speed prop & minus 12 flaps for another 12-15 knots and maybe a little night flying. It's nothing I can't handle without even thinking about it. And why 1320#? There are lots of good planes out there that qualify in every other way. Cheaper too.

 

That's one way to look at it.

 

But, the correct way to look at it is that we should be glad that the FAA has agreed to sport pilot/ LSA and the rules which have been established that allow us to fly. If we don't like those rules then we should go get a medical and use planes that don't need to comply with LSA. Or, work to have the rules changed although opening up that can of worms may give us an end result we don't like.

 

In the meantime we should accept the privilege we have been given and not give the FAA any excuse to try to change or eliminate sport pilot/LSA rules. You can bet there are those in the FAA that were never happy with the creation of sport pilot/LSA. They would love to have any excuse to come down on us. If we (either the pilots, mechanics or the industry in general) prove to be a bunch of renegades they would be more than happy to start making our life miserable. Lets not give them a reason to even think about this.

 

So, in the end analysis, I agree with Dick.

 

My 2 cents.

[Runtoeat]

Hi John. I think you said it better than I did.

[sandpiper]

Roger - I thought it was dinner but a cheap lunch works for me!!

[Jim Meade]

I guess I'm not "grateful" enough to the benevolent FAA. I'd like to do all the things that I am physically and mentally able to do, not be limited to a rule imposed to capture some free-flying ultra-lights and "get them under control".

 

I'm only offering my opinion, not engaging in a debate and don't presume I'll convince anyone, so say what you like, I'll not try to dissuade you.

[ozairangel]

My Sw [-12] was test flown at factory and showed 132kts. Since adjusting WOT to what I shall call Rogers Range, [5500] S&L Ican get 135/136 tas. I cruise at 120kts at around 5150rpm

[Jim Meade]

I looked for the German site of FD and couldn't find it. Maybe it knows I'm from the US and sends me back here. I was looking for some German factory data on CTSW and CTLS performance. I can handle the German. Can anyone help me on the URL?

 

Thanks

[Tom Baker]

I looked for the German site of FD and couldn't find it. Maybe it knows I'm from the US and sends me back here. I was looking for some German factory data on CTSW and CTLS performance. I can handle the German. Can anyone help me on the URL?

 

Thanks

 

Jim, it is www.flightdesign.com . The AOI's on the Flight Design USA website have both European and US specs. Tom

[bseager]

Is that 140 MPH or Kts?

140 knots, our CTSW is just slightly faster than our Diamond DA20 which advertises and realizes about 138 knots TAS.

[24-8003-ms]

We're based in Australia where it's OK to go -12º. The problem we're having is finding the process to get there in our US-imported SW. I was led to believe it was a matter of changing a chip. If so, where do they come from?

[FlyingMonkey]

I want to add my two cents on the sport pilot rules. Even though I have wanted to fly all my life, I actually made it happen relatively late (started flying at age 42). I could have gotten a medical, and I debated a long time between sport and private pilot. In the end, I decided to go sport, not because of the medical issue so much (though being aware as I get older the medicals get harder), but more because the type of flying I wanted to do is right in line with sport rules. Also, no medical means less federal bureaucracy in my life, and I'm all about that.

 

Maybe because I've never flown in the flight levels at 170 knots I don't know what I'm missing, but for recreational purposes I never found the sport pilot rules to be terribly burdensome. Especially when planes like the CT can fly faster and carry more weight per seat than a 172, at lower cost and with more modern equipment...and a parachute!

[kentuckynet]

I went from -6 to -12 and changed my dramatically about 7 knots. Its amazing the difference. But im certain that Roger is telling the truth but as we all know each one of these planes are very different. Anyone that doubts me just start comparing the numbers of washers between the engine mount and the firewall....

 

The procedure to change the flap setting is not too difficult but you have to have two switches and follow the directions carefully.

 

I would never go back to -6

 

mack

[Tom Baker]

The only problem with going to -12 is that your airplane is no longer LSA complient because the clean stall speed is above 45 knots.

[Adam]

I'm sure everyone knows that if you put the flaps in manual mode you can manually run the flaps through the entire range without disturbing the calibrated settings. A fellow forum member and I did this on my CTSW on the ground and measured to see the difference at max negative. We could get to about -9 on my old bird

 

I have never tried this in the air but thought I'd throw it out there for all to criticize!

[Russell Croman]

It works in the air, too, but take care: you have to turn the flap selector rather quickly through the "normal" settings (15, 30, 40), past the manual "down" detent, and get it to the manual "neutral" or "up" detents without letting the flaps deflect downward too much in the process. Usually you will be doing this at fairly high airspeed, so you don't want to overspeed the flaps. If in doubt, do it while you're still around 80kts.... then you could let the flaps go as low as 15 degrees with no worries about overspeed.

 

I find my flaps go to -10 degrees, and it gives maybe 3kt of extra airspeed. I don't find it to be worth the trouble unless I'm on a long cruise leg.

 

Here's one thing I noticed, though: at -6 degrees, my ailerons are still deflected downward a bit, maybe 5 degrees lower than the flaps. If I read the manual correctly, they're supposed to be lined up with the flaps in this setting. I think this is probably robbing a few knots... might have to tweak the rigging. Anyone else notice this?

 

-Russ

[sandpiper]

Russ,

 

My experience is the same as yours, +3K and the ailerons deflect downward a small amount. I haven't measured, but if mine is the same -10 degrees as yours, I don't think 2 more degrees would make much more difference. But, each plane is different. I remember one day that Roger H. and I took of together with Tony right behind us. He then proceded to pass us at a pretty good clip. Maybe it was the beans he had for lunch??

[Runtoeat]

Hi Russ. My CTSW was out of rigging regarding ailerons being flush with flaps @ -6. Had to get them tweaked to be correct. Not hard to do but if rod ends need to be backed out, make sure that rod end threads are sufficiently engaged into control rods when done. I have to believe that adjusting the ailerons to be flush iimproves aerodynamics.

 

Question regarding using manual flaps. Can this be done on the ground to see of the manual control will give us negative flap travel greater than our pre-set -6? The other question I have is are the ailerons set to be flush with the -12 flaps? I'm thinking that to see the full airspeed improvement with higher negative flaps, one must have ailerons flush with flaps at all of the higher negative settings similar to how they're set with -6.