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Buckaroo

Newbee with landing flap questions.

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Am impressed by all the great advise offered here.  Roger Lee's advise about choosing an instructor who has experience in the CT is very helpful.  Many of the accidents that we have seen here in Florida are a result of an otherwise competent instructor with no CT experience attempting to check out a new CT pilot.  At best it is a poor experience for both.

 

One area that seems to be missed is the importance of teaching landings at -6 and 0 deg flaps.  It is necessary to be comfortable landing the CT at these flap settings also.  Using the rule of primacy, I start at 0 deg to make sure the pilots are comfortable there, next we do 15, then we practice 30 or 40.  Finally we practice -6 in windy, gusty crosswind conditions.

 

Landing at 15 can be easier in some situations, especially in low wind conditions; however, it is important to be comfortable landing at 0 or -6 as winds get heavier.  Also, I suggest 0deg at night as it is easier to misjudge the flare.  There is more momentum at 0, and the wing is at a lower angle of attack making the CT more forgiving if the flare starts too early, or if it is windy.

 

We have seen accidents that could have been prevented had the pilot only selected 0 or -6 flaps.  When asked why he chose 15, the response is universally, "I just always land at 15".

 

John

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I bought a CTLS and did most of my PP training in my CTLS. My flight instructor had about 5 hours in a CTLS prior to my training so we learned together. I struggled but after talking to Roger Lee several times I became proficient and I loved the plane. The biggest challenge was the sight picture. I recommend you as PIC line up the plane on the ramp so you are lined up with a crack in the cement. Ask your CFI in the right seat what he sees. You will be amazed how different the sight picture is. Next change seats and take a look. It is nice to know that you have different perspectives when training. I lined the plane up on the runway and put a piece of tape on the windscreen on the center line. I used it as a point of reference until I became one with the sight picture. This may help. You may not need this because you are a high time pilot but it helped me. Good luck and have fun.

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Someone posted you let the center line split you between your legs and ignore the dash. On my historical two landings I remembered that and it helped with that part of the puzzle.

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Someone posted you let the center line split you between your legs and ignore the dash. On my historical two landings I remembered that and it helped with that part of the puzzle.

 

Yes.  I pointed that out.  The nose is small and drops out of sight.   You need to put the center line of the runway between the rudder peddles and your legs and don't look at the nose.  Some have put a piece of tape on the panel to remind them of that...   People here are just trying to point out the plane requires finess...it is light and the controls are rod based and have no play.  Once you are level over the runway just remember to pull the nose up slowly and the stick back continuously as the plane loses energy and align as above and you will grease them in calm winds.   If xwind and stronger upwind you will need to slip or crab and and align with the runway while dipping a wing and don't try to force the plane down...it can't be muscled like some of the bigger planes.

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One thing I have found helpful, is that I don't add flaps past 15° until established on short final.  Otherwise the airplane is so slow and the descent rate quick enough, that you can run out of altitude in the event of an engine outage.  If I go to 30° flaps on base, more times than not I will have to add some power to make the runway.  And I fly tight patterns, I turn base probably less than 1/4 mile from the end of the runway.  I would rather be high than low on short final, I can always adjust out excess altitude with a slip.

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For SkyCatcherPilot..I've done some instructing in both aircraft (Remos GX and CTSW). As I said in another thread...the Remos flies like a C172 and is a much more stable and easier to fly aircraft than the CT. (CT is more pitch sensitive.) Additionally, the flaps in the Remos are not nearly as effective as those in the CT; it's night and day in terms of both the additional drag and the tendency of the aircraft to pitch up. The CT approaches slower for landing and loses energy faster. I don't consider them that similar at all, even before you add in the differences in sight picture.

 

BTW, I approach teaching students how to land in the CT the same way John does, though I start at flaps 0 and move to 30 and 40 afterwards and go back to minus 6 last. I consider the minus 6 a "contingency" setting (as in total electrical failure traps them there) or something to try on a really gusty day when flaps zero won't work (though if you're having trouble at zero it's probably best to divert to a runway more aligned with the wind if the problem is related to a crosswind).

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-6 is cleaner. In the CT, it's the full flaps up setting and where you can fly her using the highest g-loads and airspeeds. You can feel the airplane accelerate when you go to them and she's harder to slow down if you forget or use them during an approach.

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-6 is negative 6 degrees of flaps.  The wing on the CT is designed for max cruise using negative flaps.  This is from the POH, explains all flap settings and how they are to be used:

 

post-940-0-00442100-1480452752_thumb.jpg

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Don't the European aircraft come with a minus 12 degree setting for more speed?

 

The Euro version has different flap settings, yes.  But they are also not constrained to 120ktas cruising speeds.

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Yes, the European aircraft has a minus 12 degree setting that results in faster cruise.  My understanding is that the -12 degree flap stall speed is greater than the maximum LSA permissible speed of 45 kts.    

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I haven't talked about this for 10 years, but it's time to dump the myth. Only 3 people have ever known.

 

I have had 3 aircraft here with -12. Neither speed was over the limit. Matter of fact -12 didn't have any better performance than -6. Everyone here forgets this works with an in flight adjustable prop that they get to use around the world except the US. If you have that prop setup and -12 then it's better.

-12 is worse for high altitude flying. At gross weight it is harder to maintain high altitudes without switching back to zero.

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Roger Lee, on 30 Nov 2016 - 4:51 PM, said:

 Everyone here forgets this works with an in flight adjustable prop that they get to use around the world except the US. If you have that prop setup and -12 then it's better.

-12 is worse for high altitude flying. At gross weight it is harder to maintain high altitudes without switching back to zero.

-12 is flaps full up & clean. Each other setting is creating more drag.

 

A mate once accidently took off with flaps at -12, he started to wonder at about 60kts why it hadn't rotated and didn't get off the deck until around 70kts.

 

I don't understand why the US won't allow inflight variable props. ~13L/hr if your not in a hurry, ~25L/hr if you are.

 

http://www.neuform-propellers.com/_downloads/pdf/operating-manual-v3-r2-20100428.pdf

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When I talked to the FAA on this (variable pitched props) they said it wasn't their idea at the beginning. When the 3 big players in our experimental industry started the LSA movement and started writing up the rules they wanted that and wrote that in. It's been there ever since. I don't see why they won't just put it in and at least just make it a sign off.

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-6 is negative 6 degrees of flaps.  The wing on the CT is designed for max cruise using negative flaps.  This is from the POH, explains all flap settings and how they are to be used:

The POH , also states , the CTLS can be landed at "any" flap setting.

 

Cheers

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The POH , also states , the CTLS can be landed at "any" flap setting.

 

Cheers

 

I wouldn't try a -6 flap landing unless you REALLY wanna have a white-knuckle experience.

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I understand all of that.  I just would have thought -6 degrees of flaps would impart an element of drag that did not exist with zero degrees is relative to the wing and puts the flaps exactly parallel to the relative wind.  IDK.

The airfoil on the CT droops at the trailing edge. It provides for great low speed characteristics, but as speed increasesthe loading on the trailing edge goes up. The reason for the negative flaps is to reduce the aerodynamic load on the trailing edge. This also reduces the overall drag. This type of airfoil is common in the sailplane community, as are the negative flaps.

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The airfoil on the CT droops at the trailing edge. It provides for great low speed characteristics, but as speed increasesthe loading on the trailing edge goes up. The reason for the negative flaps is to reduce the aerodynamic load on the trailing edge. This also reduces the overall drag. This type of airfoil is common in the sailplane community, as are the negative flaps.

 

It makes some sense if you think about it.  On a curved airfoil, the air over the top of the wing has to follow the wing shape.  The air changing direction to follow the curve must impart some drag.  reflexing flaps makes the air over the top of the wing have less directional change, resulting in less drag.  After all, a straight, flat wing would have the lowest drag...it just wouldn't make any lift.    :)

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It makes some sense if you think about it.  On a curved airfoil, the air over the top of the wing has to follow the wing shape.  The air changing direction to follow the curve must impart some drag.  reflexing flaps makes the air over the top of the wing have less directional change, resulting in less drag.  After all, a straight, flat wing would have the lowest drag...it just wouldn't make any lift.    :)

One of Flight Design's engineers explained to me that the reason was for the loading on the bottom of the trailing edge.

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One of Flight Design's engineers explained to me that the reason was for the loading on the bottom of the trailing edge.

 

Sure, I wasn't arguing with you.  I meant that the more curved the air flow the more it would load the trailing edge, and raising the flaps to -6 would give  "straighter" airflow than 0  and thus not put as much pressure on the trailing edge.  Sorry if I wasn't clear what I meant.

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I haven't talked about this for 10 years, but it's time to dump the myth. Only 3 people have ever known.

 

I have had 3 aircraft here with -12. Neither speed was over the limit. Matter of fact -12 didn't have any better performance than -6. Everyone here forgets this works with an in flight adjustable prop that they get to use around the world except the US. If you have that prop setup and -12 then it's better.

-12 is worse for high altitude flying. At gross weight it is harder to maintain high altitudes without switching back to zero.

I can't argue with your empirical evidence, Roger, that there was no difference in performance between -6 and -12, but surely if you change the shape of the wing so that angle of attack and subsequent drag is reduced, it simply has to change the performance too, even if it's a very small change.  

And if there is no difference in performance, why would FD make a special model exclusively for the US market with its own flap setting?

I can't reconcile the physics and your experience with the two negative flap settings -?

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That's what I thought.

 

But Roger's point was that in his experience, there's no difference between -6 and -12 regarding top speed.

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It makes some sense if you think about it. On a curved airfoil, the air over the top of the wing has to follow the wing shape. The air changing direction to follow the curve must impart some drag. reflexing flaps makes the air over the top of the wing have less directional change, resulting in less drag. After all, a straight, flat wing would have the lowest drag...it just wouldn't make any lift. :)

Technical point...it would still create lift via AoA and impact lift. Just like your hand out the car window.

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