wrote: Van probably says no N>acN>ro with electrics because they have much slower = response time than hydraulic props. Still not as bad as *no* response time from a fi= xed pitch, & they do acro all the time. :-) The issue is over-speed if they are in flat pitch going up & can't respond quickly enough to limit rpm going down. The throttle can solve this, just like it would with a fixed pitch pr= op; just extra work load for the pilot. A more significant question is whether = MT approves it for acro. Charlie -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.= html --0-501965462-1241408952=:2821 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable

Hydraulic and electric constant speed pr= ops are two totally different animals.

You could say that hydraulic props are analog and that electrically ad= justable props are digital, as a good analogy.

Hydraulic constant speed props are constantly adjusting as the oil pre= ssure changes due to the output of the governor.

They are designed to have a relatively quick response and be operated = continuously and therefor ideal for aerobatics.

Conversely an electrically adjustable prop only changes the pitch in i= ncrements when the power to the motor is applied.

Most electric governors have an adjustable band (dead band) of rpm in = which the motor will not activate so that it is not continuously hunting to= find the correct RPM.

This is necessary because the motors are not usually rated for 100% du= ty cycle.

If the adjustment motor is run continously it would= tend to over heat and its life would be severely shortened.

The dead band is the reason for the slow response of and ele= ctric prop.

That is probably why aerobatics is not recommended with these props.

It's all about compromise.

If a large enough motor were used to provide continous operation (with= out the deadband) it could certainly keep up with the rigors of aeroba= tics, but would probably require too much current and be too heavy to mount= out there on the nose.

Jim

--- On Sun, 5/3/09, Charlie England <ceengland@bel= lsouth.net> wrote:

Van probably says no N>ac<=
/SPAN>N>ro with electrics because they have much slower re=
sponse
time than hydraulic props. Still not as bad as *no* response time from a fi=
xed
pitch, & they do acro all the time. :-) The issue is over-speed if they=
 are
in flat pitch going up & can't respond quickly enough to limit rpm goin=
g
down. The throttle can solve this, just like it would with a fixed pitch pr=
op;
just extra work load for the pilot. A more significant question is whether =
MT
approves it for acro.

Charlie

--
Homepage:  http://www.flyrotary.com/
Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.=
html

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