Elevator trailing edge reverse taper?

I have searched through posts looking for any explanation or opinions on why the RV14 elevator trailing edge has the reverse taper.

My own speculation is that it may have to do with dampening some sort of flutter, air flow efficiency, maybe easier to fabricate than a folded edge, something unique to get folks talking or scratching their heads, . . .

How about it RVBuilded2002, there has to be a reason that makes something better in some sort of design compromise?

The RV-14 prototype had the standard trailing edge when first introduced but later had the type you described installed for improved handling. Do not recall the specifics.

jeffw@sc47 said:

I have searched through posts looking for any explanation or opinions on why the RV14 elevator trailing edge has the reverse taper.

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Explain reverse taper on a trailing edge for those of us not building a 14. I can not picture what you mean.

plehrke said:

Explain reverse taper on a trailing edge for those of us not building a 14. I can not picture what you mean.

Click to expand...

The trailing surface of the 14 elevator tapers just like other RV elevators until about +1/2" from the trailing edge. At that point, the trailing edge then gets wider until at the trailing edge, it is about 1/4" thick.

I was told that this was done because during testing it was found that very tiny stick movements would not change pitch. It took some larger than desired stick motion to move out of this dead zone, hence the widened trailing edge.

When I flew the demo aircraft, which had the new reverse taper elevator, I found pitch response immediate with no dead zone.

That 's interesting Bob, thanks for the insight.

In design solutions there are usually compromises, i.e. you push in here and something pokes out over there - was there anything that had to be overcome, allowed for, or adjusted to make the control response improvement? or was it a win-win solution?

The trailing edge shape of the RV-14 elevators was selected for a number of reasons but none of them were to do with "dampening some sort of flutter, air flow efficiency, maybe easier to fabricate than a folded edge, something unique to get folks talking or scratching their heads, . . ."

The RV-14 has been flight tested to a high level of detail.
This includes test flights by a lot of different pilots doing a lot of different types of tests. Some of which even included use of stick force measurements acquired using pound scales and a custom control stick with strain gauges.

During the course of this testing, a couple of subtle differences in handing qualities when compared to some of the other RV's, were noted.

As a result, design effort was invested to make adjustment to these by making a change to the trailing edge shape of the elevators.

This removed a very minor dead band in the elevator control circuit (which by the way, only a very few test pilots who flew the airplane with the original elevators ever made any mention about), and it improved the stick force per G gradient.

There is no down side to the shape (no measured speed difference) other than speculation that it was to resolve a strange "problem".
We look at it more as putting out the effort to make the airplane fly and handle as well as possible.

BTW, an added benefit in designing the RV-14 to this level of detail, is another design change that was made to the control system. The one system link that has always been a challenge to build free of play in side by side RV's is the roll hinge point on the control stick. The bronze bushing. Even if the best fit possible was attained between the bushing and the reamed hole in the stick weldment, there is always some level of slop.
The RV-14 is using sealed bearings for this pivot point on the control column.
The elevator control is silky smooth with no discernible play.

Air Tractors too.

The big 800 gallon toting Air Tractor 802 has a similar thick trailing edge on the elevators. I was told that it "hunted" some in pitch mode and that solved the problem.

Best,

I learn something or a few things new every day, so it seems a win-win with the elevator trailing edge design.