What's Your "Nose UP" Speed?

[Runtoeat]

I wanted to work on stabilizing my final landing speed and set out flying the other day to practice doing this.  After entering final at my airport, I pulled power, set my flaps to 15 degrees, then turned my pitch trim to adjust my power off speed.  To my surprise, I could not get my CT to go slower than 60kts with full "nose up" trim (i.e., the trim wheel was rolled back to full stop).  Referring to the Line Maintenance manual for specs, it appears that my stabilator trim tab is not set to the recommended dimension and should be adjusted. Before re-rigging my pitch trim, I am wondering if my speed is normal or do other CTSW owners achieve lower speeds?  If any of you know what speed full nose up trim provides when in this condition of one person aboard, 15 degree flaps and power off, I would appreciate your response to this post.

[FlyingMonkey]

Dick, mine usually trims out around 62-65kt with full nose up trim.  This is not ideal for me, since I usually fly at 55kt from the point abeam the numbers, and have to hold some back stick pressure to accomplish this.

 

Before getting too deep into re-rigging things, have you thought about moving the trim indicator nub my the throttle a little forward on the cable?  My understanding is that if you do that you can change the trim range a bit.  I'm sure Roger or somebody who knows for sure will chime in on whether that method will actually work, but I thought I had read that that is what Charlie Tango did to change his trim range to trim out slower.

[Runtoeat]

Hi Andy.  The trim indicator only shows a position of the trim and this can be varied by moving it on the actual trim cable.  It does not affect actual trim.  You have the same situation as I do.  We want to lower our "coasting" speed when trim is fully "nose up".  It is fairly easy to do this but it does require a mechanic with knowledge of how to properly and safely rig flight controls.  Basically, we need to shorten our two control rods that operate our stabilator trim tab.  Remove the control rods at the bell crank seen inside the tail, screw the rod ends into the rods 1/2 or 1 turn and this should increase our "full stop nose up" trim and bring down our speed a few knots.  Caution here though because there is a trade-off.  Just as this increases the "nose up trim" it will reduce the "nose down" trim.   One must flight test to verify nose up and nose down trimmed conditions provide acceptable air speeds after this adjustment.

[FlyingMonkey]

Hi Andy.  The trim indicator only shows a position of the trim and this can be varied by moving it on the actual trim cable.  It does not affect actual trim.  You have the same situation as I do.  We want to lower our "coasting" speed when trim is fully "nose up".  It is fairly easy to do this but it does require a mechanic with knowledge of how to properly and safely rig flight controls.  Basically, we need to shorten our two control rods that operate our stabilator trim tab.  Remove the control rods at the bell crank seen inside the tail, screw the rod ends into the rods 1/2 or 1 turn and this should increase our "full stop nose up" trim and bring down our speed a few knots.  Caution here though because there is a trade-off.  Just as this increases the "nose up trim" it will reduce the "nose down" trim.   One must flight test to verify nose up and nose down trimmed conditions provide acceptable air speeds after this adjustment.

 

Ah, got it.  CT mentioned changing his trim indication, I didn't realize there was more to it than that.

 

I wonder why it's set so fast...after all, I never use full nose down trim even at very high speeds, so there is definitely a bias toward high speed in the trim configuration.  I guess this might be a liability issue, where FD does not want a lawsuit for setting trimmed speed too slow and allowing an inattentive pilot to fly right into a stall without any stick pressures to give them an inkling of what's about to happen.  

 

Where are the rod ends that need adjustment, in the tail under the stab?  I will talk to my A&P about this.

[Ed Cesnalis]

... I never use full nose down trim even at very high speeds...

 

Where is your trim if you close your throttle and use 30 or 40 degree flaps and trim for 50kts?

[FlyingMonkey]

All the way back and I still need back pressure on the stick to maintain that speed.

[Ed Cesnalis]

All the way back and I still need back pressure on the stick to maintain that speed.

 

That don't sound right, check it next time you fly.   When I am abeam I use 15 with a level attitude and closed throttle to slow to 62kts.  At 62kts I deploy 30degrees and drop my nose a huge amount, something like 15degrees+.  I need that very nose low attitude to maintain 55kts and I need to trim nose low to the stop to trim off the pressure.  How could yours be the opposite?

 

At 14 seconds on this video is where I deploy 30degrees and trim full nose down to hold that speed/attitude.  How is your CTSW different?

 

 

You need to know where you need full nose down and full nose up before you can adjust the range.  Before adjusting the trim range you should ask yourself why? What changed?  If it has been in need of an adjustment since it was new then ok.  

[FlyingMonkey]

Nothing has changed since I got it...I will check it next time I'm up.

 

When I put 30° flaps in, the nose does drop and needs to stay there, but I never remember having to push trim forward to maintain that.  I could be wrong, and might have just been using stick against the pressure to compensate without thinking about it.  I have not been using flaps more than 15° until just recently, I'll pay closer attention next time around.

[Ed Cesnalis]

Its real handy to trim for 55 or the speed you like and I believe this is the configuration that tests your forward limit so you want to be familiar before you change your range.  If you elect to give yourself more nose up you will possibly give up the ability to trim for approach with full flaps.

[FlyingMonkey]

Its real handy to trim for 55 or the speed you like and I believe this is the configuration that tests your forward limit so you want to be familiar before you change your range.  If you elect to give yourself more nose up you will possibly give up the ability to trim for approach with full flaps.

 

Got it, I was thinking of trimming for 15° flaps...it did not really occur to me that you'd need opposite trim for 30° - 40°.

[Runtoeat]

CT, your questions are what started my quest to use trim to stabilize my speeds during landing.  Like Andy, I use my stick to control my airspeed and have gotten away from using my trim to do this.  When I first got my SP license, I did use trim but this was on the trainer CTSW.  For some reason, I didn't continue to use trim after getting my CTSW.   Thank your for your questions regarding airspeeds at the higher flap settings.  I know I'm at about 60kts with 15 flaps and power off.  I will check out my airspeeds with 30 and 40 flaps with power off and see what I get.  I shoot for 55kts on short final and about 50kts over the numbers for 15, 30 and 40 flaps but use my stick to control my speed. 

[Ed Cesnalis]

We hear FastEddie advising approaches with a closed throttle, one less thing to mess with.  Trimming for approach speed adds to that simplicity, 2 less things to mess with.

 

I also keep it simple by using 1 configuration and 1 speed from abeam the numbers.

[Tom Baker]

The CTSW has used 2 or 3 different stbilator control system set ups. Advice given based on experiences in one airplane might not work in another. My late 2006 required very little trim adjustments when flying, but a mid 2007 had springs in the system and it required all of the trim adjustment that was available. The CTLS is all together a different beast.

[Jim Meade]

I flew my CTSW today and got the following trim speeds with throttle at idle and trim wheel completely rolled back. No hand on the stick.

-6° flaps 58 kias, stall horn on, top of the yellow on the AOA

0° flaps 55 kias, stall horn on, top of the yellow on the AOA

15° flaps 47 kias, no stall horn, AOA in yellow

30° flaps 43-47 kias (couple of trials), no stall horn, AOA in yellow

40° flaps 45 kias, AOA top of the green

 

As you can imagine, the -6° was at the verge of a stall. The 0° was close to a stall but a little less so. On my plane, I would not want the trim to give me any more nose up at those flap settings. At all other flap settings there was no immediate concern about a stall (although in gusty circumstances that might be different).

 

BTW, after doing this, I did a couple of partial elevator trim stalls. CFIs are required to demonstrate them but others are not. If you like power on stalls at max thrust you will love a fully developed elevator trim stall. It makes one be a bit slow to think about changing trim tab adjustments without some thought. Airplane Flying Handbook pp 4-11, 4-12.

[FlyingMonkey]

58kt is near a stall at -6?? The book says 48kt or something, and it's not LSA legal unless it's 51kt or less. 58kt sounds really high.

[Runtoeat]

Tom, good point. If two people might have the same year CT, there is no guarantee that the flight controls will function similarly.  Early CT's were works in progress regarding flight control configurations with changes made during production runs.

 

Jim, thanks for the speeds.  It is interesting that your full nose up trim condition produces a fairly consistent 43 to 47kts speed when at 15, 30 and 40 flaps. Of particular interest to me is your 15 flap speed of 47kts. which compares to my speed of 60kts. I have not found any recommended air speeds provided by FD Germany to support adjustment of the pitch trim.  The manual only shows recommended distances in mm of the trim tab and what's really needed is to have air speed referenced.  Without this, it appears that the target speed is up to the personal preference of the operator. 

[Jim Meade]

58kt is near a stall at -6?? The book says 48kt or something, and it's not LSA legal unless it's 51kt or less. 58kt sounds really high.

These trim setting tests are not stall tests.

 

My speeds for -6° stalls at a stabilized altitude are from 42 to 47 kias. 0° is 43 kias. 15° is 37-39 kias. 30° is 34-35 kias. 40° is 29-33 kias. These were replicated trials about 2 years ago trying to hold altitude.

 

Stalls where one tries to hold a constant descent rate, such as were one is stretching an approach, were very similar and about 2 kias higher. You may note that in every case a higher flap setting resulted in a lower stall speed.

 

All the above were in level flight. 15° flaps in 20° banked turns had stall speeds around 40-42 kias.

 

Probably different pilots in different airplanes at different weights and CG locations with different density altitudes would have different results, perhaps markedly different. There is nothing magic about my numbers. I did them to see if I was in agreement with the book, per your question. I am satisfied that I'm close enough.

[Jim Meade]

Seems like you would want full aft trim to hold short field landing air speed with full flaps and certainly no slower than that.  IDK.

I think that one should always trim the aircraft to fly the way you want it to hands off. That would agree with what you said. My reasoning is that as one's attention wanders, the aircraft is not likely to deviate from your desired attitude. It would make for a more stable approach.

 

But, some eminent people disagree. Some prefer to hold some back stick elevator pressure on final so that if you have to go around the plane is someone predisposed to pitch down and set at a more desirable AOA. Maybe they have a point.

[Roger Lee]

To be LSA it can not stall more than 45 knots with full load and clean.

This is one reason we don't have -12, the stall is higher at full load.

[Mike Koerner]

At low speeds tail loads, stick forces, elevator angle & trim position are all sensitive to weight and balance. If your c.g. is in the aft portion of the envelope the full aft trim speed will be slower. If the c.g. is forward it will take more down-force on the tail and thus more trim to get the plane slowed down.

Mike Koerner

[Runtoeat]

Are there any more CTSW or CTLS owners who might know their full nose up trim speeds at 15 and greater flaps with engine off?  Of particular interest are those CT's that are new or fairly new that have original factory rigging.

[207WF]

I too, can easily trim to 55 knots or less at flaps 15.  It seems that you might need an adjustment.  WF

[FlyingMonkey]

I tested today with 30 flaps. It's the same as 15 flaps...the trim full nose up is insufficient to maintain my preferred 55kt approach speed. If I let go of the stick the airplane noses down and picks up speed, even with full nose up trim.

[Runtoeat]

100hamburger, I'm  polling the forum to get a general idea of what airspeed one attains with a CT with power pulled to idle, 15 flaps and pitch trim wheel (switch in your case) set to full "nose up".  Some pilots will choose to adjust the pitch trim so that the airspeed is set to a stabilized airspeed in the final approach to a runway.  My choice for final approach speed is 50 to 55 kts and I would like my pitch trim to be able to hold this speed on my final approach to the runway.  I'm wondering what speeds other owners  the pitch tndering if other CT aircraftrim should be capable of slowing the CT to 50 to 55 kts.

[FredG]

Dick, with power at idle, 15 degrees of flaps, and full nose-up trim, my 2006 CTsw stabilized at an indicated 48 kts.  (Flight performed at approximately 75 pounds below gross.)