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Single Trim Tab Operation- On purpose!

W

WrightsRV7

Well Known Member
Ran the experiment, not with the most forward CG limit, however found that with my std build RV-10 that single tab operation that it was fully acceptable at take off (full fuel and pilot, 30 lbs luggage) and landing (-16 gal fuel). Still ample up trim, far from full at landing. You ask why.... the single tab operation afforded less sensitivity and easier cruise adjustments. Just my two cents and a data point. I plan to keep flying under single-elevator trim tab, just a data point, not recommending anybody change or do anything different ...... but after all, we are ALL flying an EXPERIMENTAL aircraft....love this plane, and my continued kudos to VANS, they provide us with an exceptional airframe and product support.
 
If you were testing to meet FAR23 for trim effectiveness you would need to be able to achieve neutral trim at minimum approach speed with fwd C.G and full flaps.
I am not sure most RV-10's fully achieve this 100% but I would bet that with only one tab active it wont.
 
Scott
What was the rationale for not operating both trim tabs symmetrically for the -10? Sensitivity?
 
we are ALL flying an EXPERIMENTAL aircraft.
Click to expand...

Amen.

What did you do with the other trim tab?
tab operation afforded less sensitivity and easier cruise adjustments.
Click to expand...

A simple $20 speed switch easily takes care of trim speed, if that is of
concern.

Just curious if you simply wanted to experiment or hoped to gain some sort of benefit.
 
For one thing

There would be a significant lightening of the tail; those teleflex cables aren't light, and they're very far aft. Getting rid of one would offer some CG shift forward, if it were necessary (not saying it is, but most seem to think it can be a good thing).
 
Other trim tab at Neutral position

Just a bit more information. I ran both trim tabs to neutral, unplugged the right trim servo, so now only left servo was active (it is a dual electric servo system). In my system, this would be simulating a single-servo failure as well, another reason to run the test, at least from my perspective. But heck, I have landed the 10 with full flaps, or with no flaps, neutral trim, forward CG, and it still lands like a dream with just using a bit more muscle. What a great flying aircraft design it is.

FAR ? 23.409 Tabs.

Control surface tabs must be designed for the most severe combination
of airspeed and tab deflection likely to be obtained within the flight envelope
for any usable loading condition.


Lots of ways to interpret this FAR, full up trim, full power at take-off, can the pilot handle the stick forces.....we know that is not the case on many aircraft....so wanting to learn, where does it say and/or suggest neutral stick forces at stall speed, dirty, and full forward CG? Approach speed is very different and is very situation and pilot controlled. I personally "fly over the fence" at 70 KIAS with full flaps, and can I achieve neutral stick force with a very forward CG and one trim tab, yes. I think you are suggesting that the FAR 23 says one can stall the aircraft using up trim (i.e. no stick force by the pilot) dirty with full forward CG, which I don't see that in the FAR, but always wanting to learn.

I will add, that I personally never trim out all the stick force while on final, I prefer at least some applied back pressure on the stick, and I finish all my landings with the stick 100% back in my lap and that is done with arm muscle, not using the trim tab in the flare, and I never release until I stop the taxi or the winds demand a different direction (e.g. a severe tailwind on taxi, and yes, we get those here in the desert). The 10 has light and fantastic elevator control at the air speeds found in the flare, as always my compliments to VANs for a fantastic design.
 
WrightsRV7 said:
Just a bit more information. I ran both trim tabs to neutral, unplugged the right trim servo, so now only left servo was active (it is a dual electric servo system). In my system, this would be simulating a single-servo failure as well, another reason to run the test, at least from my perspective. But heck, I have landed the 10 with full flaps, or with no flaps, neutral trim, forward CG, and it still lands like a dream with just using a bit more muscle. What a great flying aircraft design it is.

FAR § 23.409 Tabs.

Control surface tabs must be designed for the most severe combination
of airspeed and tab deflection likely to be obtained within the flight envelope
for any usable loading condition.


Lots of ways to interpret this FAR, full up trim, full power at take-off, can the pilot handle the stick forces.....we know that is not the case on many aircraft....so wanting to learn, where does it say and/or suggest neutral stick forces at stall speed, dirty, and full forward CG? Approach speed is very different and is very situation and pilot controlled. I personally "fly over the fence" at 70 KIAS with full flaps, and can I achieve neutral stick force with a very forward CG and one trim tab, yes. I think you are suggesting that the FAR 23 says one can stall the aircraft using up trim (i.e. no stick force by the pilot) dirty with full forward CG, which I don't see that in the FAR, but always wanting to learn.

I will add, that I personally never trim out all the stick force while on final, I prefer at least some applied back pressure on the stick, and I finish all my landings with the stick 100% back in my lap and that is done with arm muscle, not using the trim tab in the flare, and I never release until I stop the taxi or the winds demand a different direction (e.g. a severe tailwind on taxi, and yes, we get those here in the desert). The 10 has light and fantastic elevator control at the air speeds found in the flare, as always my compliments to VANs for a fantastic design.
Click to expand...

I think 23.409 has to do with the design strength of the tabs, not the function of them (but I didn't take the time to check so could be wrong)
There is a part of 23 that requires the ability to trim hands off in power-off full flap approach. That doesn't mean you have to do that (I don't either) but it is a test to prove adequate performance of the pitch trim system and have some margin.

And no I wasn't suggesting that the FAR 23 says one can stall the aircraft using up trim (i.e. no stick force by the pilot) dirty with full forward CG, which I don't see that in the FAR, but always wanting to learn.

I said you are supposed to be able to trim to a hands off glide at minimum approach speed with full flaps at a fwd C.G.

Bill.Peyton said:
Scott
What was the rationale for not operating both trim tabs symmetrically for the -10? Sensitivity?
Click to expand...

Yes

It was to reduce the travel amounts (and sensitivity) in the mid range but still have a lot of trim influence at the extreme.

My opinion is that with just one tab functioning the controlability is being reduced at the fwd part of the C.G. envelope. I almost find it amusing that when customers first started completing and flying RV-10's there were complaints that it was overly nose heavy and there wasn't enough pitch trim when flying at fwd C.G. (A problem common to any 4 place or larger airplane with large effective flaps, when flown with no baggage or rear seat passengers), and now we have some people reducing the amount of pitch trim effectiveness...........
 
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thank you...

thanks to all for the comments, history, insight, and data...it is amazing how some pilots wishes drift around in direction....careful what you wish for...:) I personally feel there are a lot more certified airplane and high time pilots moving to the VANs aircraft...a compliment for sure to VANs...and I think this is bringing in a much broader perspective to comments & concerns. Heavy stick forces in a VANs...Lack of split second response to control inputs...not in a VANs...With ONE TRIM TAB to little effective trim tab...NOT in my opinion...I am sticking with ONE ACTIVE TRIM TAB on my 10, and yes, with me and full fuel, I will have something in the baggage compartment, I really like the collapsible 5 gal water container, cool idea! But for safe flight, that is not needed, just a cruise performance enhancer.
 
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