REFLECTOR: Pitch Cycling (was Pitch Trim Mystery)

Scott Derrick scott at tnstaafl.net
Thu Feb 16 16:49:13 CST 2006


> John,
>  no adjustments available/allowed on the high dollar, certified
> S-TEC.

Thats odd as my certified Century has a mutlitude of adjustments on the
front panel for just about anything you can think of..  I think there are
16 different ones that you are supposed to verify when installing and
thats not all of them.

Scott

>

> Chuck Jensen
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of John Dibble
> Sent: Thursday, February 16, 2006 4:55 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Pitch Cycling (was Pitch Trim Mystery)
>
> Pat,
> My cycling is WITH the ap on.  And it is very short cycles (a few secs).
> If I
> disengage the ap, it goes away.  It only happens once in a while and
> usually a quick
> jab of the stick stops it.  If not, I just fly manually for a while.
> Maybe the ap
> gets tired.
>
> John
>
> Pat Shea wrote:
>
>> I posted a query a while back about cycling. Flying
>> solo and trimmed for level flight, my XLRG has a
>> tendency to cycle in pitch. It can settle into 2
>> minute cycles with an amplitude of +/- 100'. With two
>> people up front this cycling tendency goes away. My CG
>> is comparable the most XL's.
>>
>> What's interesting is that the refecltor replies at
>> the time reported negative cycling. I've since spoken
>> to multiple fliers who do experience pitch cycling.
>> I'm still curious if anyone has been able to combat
>> this by means other than using the auto pilot or
>> adding ballast up front.
>>
>> Pat
>>
>> --- John Dibble <aminetech at bluefrog.com> wrote:
>>
>> > Scott,
>> > Thanks.  That helps a lot.  I was concerned about
>> > pitch stability because sometimes my
>> > S-TEC ap starts cycling, so I don't want to make it
>> > worse.  But if having the strainer
>> > inverted provides the same stability, then no
>> > problem.
>> > Any easy way to remove the strainer without
>> > incurring a lot of cosmetic work?
>> >
>> > John
>> >
>> > Scott Baker wrote:
>> >
>> > > Hello John,
>> > > Removing the sparrow strainer will cause the pitch
>> > control motion to become
>> > > more sensitive - but not to the point of
>> > instability.
>> > > I'm not sure of the aircraft's behavior if the
>> > sparrow strainer were
>> > > reversed - thinking about it, the upward lifting
>> > of the strainer will lend
>> > > itself to favor nose pitch down - which left
>> > unchecked will result in
>> > > greater air speed - which gives more power to the
>> > sparrow strainer - which
>> > > causes the nose to pitch down some more --- I
>> > suppose at some point, the
>> > > pitch spring will halt this cycle of events.
>> > > SB
>>
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