REFLECTOR: Elevator Trim Spring

Wed Feb 1 19:38:53 CST 2006

Al, you said it better than I did...

I don't think I could fly my plane with the trim spring as it is if the 
trim was stuck full up or down. At least I'd have to two hand it. But if 
I trim the spring narrower as you suggested that would reduce the trims 
effectiveness at full up and down and would make hands off flying 
impossible.

Another reason I am considering the Strong Trim System.

Scott

Al Gietzen wrote:
>
> The stiffer the trim spring, the more stick force is required to 
> overcome the force of that spring in the case of an in-operative trim 
> unit.
>
> My opinion is that the criteria should not just be the ability to 
> control/land the plane if the trim unit fails in cruise position; but 
> if the trim unit fails in either extreme position; as would be the 
> case with a shorted wire or stuck/failed trim switch. Unless you are 
> VERY strong; the standard, untrimmed spring may not allow you to meet 
> this condition. In other words, the spring needs to be trimmed 
> (narrowed) until you can reasonably achieve full down elevator 
> (trailing edge down) with the trim set to full up (trailing edge up) 
> elevator.
>
> If proper trimming ability is not achievable with such a spring, then 
> perhaps an alternative trim system should be considered.
>
> I am reasonable strong, and found that I needed to trim the width of 
> the spring to 1 ¾” to meet the criteria. I haven’t flown yet, so don’t 
> know how well the trim system will work.
>
> FWIW,
>
> Al
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] 
> On Behalf Of Chuck Jensen
> Sent: Wednesday, February 01, 2006 7:36 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: RE: REFLECTOR: Elevator Trim Spring
>
> Scott,
>
> You wrote that "I think it would be hard enough trying to fly it with an
>
> inoperative trim system as it is, any stiffer and I'd be out of muscle
>
> pretty fast." If I understand the issue here (and that is not a given),
>
> the installation of a stiffer trim spring would assist you, not create
>
> additional resistance that you would have to overcome, in other words,
>
> the stiffer spring would be a force-multiplier for you.
>
> Then, instead of using your muscles to compensate for the trim spring,
>
> you can use them for important things like tuning your Sirius radio.
>
> Chuck Jensen
>
> -----Original Message-----
>
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>
> Behalf Of Scott Derrick
>
> Sent: Wednesday, February 01, 2006 10:08 AM
>
> To: Velocity Aircraft Owners and Builders list
>
> Subject: Re: REFLECTOR: Elevator Trim Spring
>
> I can see how he might need more travel.
>
> As my trim is set up, I have just enough down trim to cruise at 65%
>
> power with just me in the front. If its bumpy I don't have enough, I
>
> have to constantly give it a shove forward or use George. If have two
>
> in the front I don't have enough up trim for a hands off 90 knot
>
> approach, just me its fine. If I fix it so I can fly a 90 knot
>
> approach hands off with two, I'd loose my hands off cruise trim
>
> setting.
>
> So as Scott B. said, I could possibly stiffen up the spring, I don't
>
> like this option because Or I could use a trim actuator with more
>
> travel. I had not considered that and will have to think about it.
>
> However I do like the design of the Strong Pitch Trim system and would
>
> welcome the added space behind the panel if I removed the fiberglass
>
> spring trim system. Strong now has a PWM controller for his trim system
>
> for fine pitch adjustments at fast speeds. A problem I partially solved
>
> on the original system with a electric brake.
>
> Scott
>
> Ron Brown wrote:
>
> > John,
>
> >
>
> > I don't think you will need more travel if you use the unmodified
>
> > factory ? shaped spring installed per the manual
>
> >
>
> > You'll just need to adjust its location to get the amount of up and
>
> > down trim needed for your plane.
>
> >
>
> > Ronnie
>
> >
>
> >
>
> >
>
> > ----- Original Message ----- From: "John Dibble"
>
> <aminetech at bluefrog.com>
>
> > To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>
> > Sent: Tuesday, January 31, 2006 6:56 PM
>
> > Subject: Re: REFLECTOR: Elevator Trim Spring
>
> >
>
> >
>
> >> Where can I get an actuator with more travel?
>
> >>
>
> >> John
>
> >>
>
> >> Scott Baker wrote:
>
> >>
>
> >>> While its interesting to think about the benefits of variable
>
> geometric
>
> >>> wings, canards, and winglets - lets remember the practical elements
>
> of
>
> >>> system design as it applies to weight, complexity of design and
>
> >>> maintenance,
>
> >>> and of course cost. The Beech Starship had a base list price of
>
> >>> $3.9M when
>
> >>> it was introduced in 1989. There are lots of cool things that would
>
> >>> be fun
>
> >>> to try - given relief from $$ constraints. The subject of
>
> >>> pitch-trim has
>
> >>> been discussed on the Reflector off and on in the past. The basic
>
> >>> linear
>
> >>> actuator/fiberglass spring system works well to my liking. I happen
>
> to
>
> >>> think it is one of the finer flying attributes of the Velocity. If
>
> an
>
> >>> aircraft does not have enough pitch trim (in cruise or in slow
>
> >>> flight) the
>
> >>> answer in most instances is to re-mount (adjust the location) of the
>
> >>> linear
>
> >>> actuator so that it gives the needed travel. Sometimes the
>
> fiberglass
>
> >>> spring needs stiffening - this can be done by adding a few plies of
>
> >>> glass -
>
> >>> or replacing the spring with a new one from the factory. A few
>
> >>> builders
>
> >>> have installed linear actuators with an additional inch of travel
>
> >>> (in order
>
> >>> to get enough up _and_ down trim).
>
> >>> Scott Baker
>
> >>>
>
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