Carl,
Microswitches do not regularely fail. Their MTBF is typical one ot 10
million.
However, thanks for confirming this, in this (Woodcomp) application they
fail for 2 reasons.
Wrong environment, not intended for outdoor use.
Underrated for heavy DC current.
Maybe an example helps. Take a look at the brake-light switch of your
car. It would be a typical place for a microswitch, but instead a 4
times bigger lump sits there. Why? Because it has to switch DC, although
far less then for a heavy motor. Becaue the inside of a car is not
classiefied as dry, although it will seldom rain there.
Failsafing with a second switch does not help.
It just doubles the fail factor.
In case of water ingress this might be clear, there are now 2 paths to
short.
As help for underrated switches, it is even for layman fairly easy to
understand that due to unavoidable mechanical tolerances, the switches
will never switch at te same time. As a result all load will be carried
by one switch.
Until it has melted, which will never be discovered until the second one
goes. Unless it melts to ground.
Another monkey story indeed is the mechanical stop. If all fails, that
should stop the blades from running in idle.
In flying you have to be sure that your minimal pitch is flyable. How
sure are you that your mechanical stop A does keep you in the air and B
does not burn your motor or break the gears? How many of you Woodcomp
jockeys do test their electrical endstops on a regular bases? Who has
ever tested the mechanical endstops?
Maybe its is easyer to forget and just enjoy flying. But recommending
your favourite deathtrap goes really one step too far. Wether you have a
regular, reversing or feathering woodcomp prop. The prop on OH-XJO took
182 hours before it tried to kill me.
Regards,
Jos OKhuijsen
27.6.2011 2:05, Carl Pattinson kirjoitti:
>
> As far as I am aware Woodcomp do not ban the use of the Smart Avionics
> controller Jiri was aware this was the controller of choice for me
> and didnt have a problem with it.
>
> Regarding the allegedly faulty micro-switches It has to be accepted
> that micro-switches occasionally fail and this is a potential risk. On
> the Woodcomp installation there are 2 microswitches that should
> prevent the prop going into superfine. If the first one fails, the
> second one cuts out 1 degree later.
>
> In addition to this, most of the Woodcomp props have a physical stop
> that prevents the blades from going into super fine. Its only when the
> reverse pitch option is used that this ultimate safety feature is lost.
>
> Moral of the story is dont have a prop that can go into reverse
> pitch. In the UK the LAA wont allow a CS prop without physical limit
> stops for that very reason.
>
> Carl Pattinson
>
> *From:*owner-europa-list-server@matronics.com
> [mailto:owner-europa-list-server@matronics.com] *On Behalf Of *houlihan
> *Sent:* 26 June 2011 22:25
> *To:* europa-list@matronics.com
> *Subject:* Re: Europa-List: Woodcomp after Sales Service
>
> Hi
>
> Further to Jos's comments about his very serious accident I seem to
> recall that the Austrian authorities planned to issue a report
> regarding the possible cause. I may have missed it so can anyone let
> me know what it contained, preferably in English.
>
> Not being an expert in these things I find I have problems linking the
> limit switch failure Jos talks about to the fact that for the
> propeller to go to fully fine or even beyond fully fine to a beta
> state requires the motor to be powered to drive it there. I am sure
> there may be a mechanism that will make that happen but I cannot see
> how it can do that just because a limit switch fails.
>
> Also my understanding is that Woodcomp do not support the Smartavioncs
> controller not surprising really as it is not their product and it is
> in competition with them but " banning" it is beyond their remit.
>
> Tim H
>
>
> On 26 June 2011 20:10, Jos Okhuijsen <josok-e@ukolo.fi
> <mailto:josok-e@ukolo.fi>> wrote:
>
> <mailto:josok-e@ukolo.fi%3eHi>
>
> Sorry to remember you all that my Woodcomp prop nearly took my life.
>
> I hate to repeat my words, but memories seem to be short.
> The propeller i had was equipped with microswitches, which were and
> ,after a change, still are not designed for outside use.
> Nethertheless these switches are mounted on the backplate, open for
> weather.
> These switches are designed for AC 240 V, not for DC 12 V, and the Amp
> rating is way below the current going through them.
> The cross-over diodes are specified for less then half the current drawn.
> Even when activated only occasionally, it's a design flaw.
>
> Know to me are 3 incidents with short circuiting micro-switches, both
> other pilots could land their plane without damage to their plane or
> themselves. An incident with a loose gear, causing one of the blades
> at a totally diffent angle then the others was reported to me, and
> never made it to this forum. This seems to be the happy family show,
> which i am now spoiling. :-(
> It may well be that there are others, or people never fly in rain. or
> are just very lucky.
>
> In my case, to the best of my knowledge, a microswitch short
> circuited, taking the prop to a feather situation, shortly after
> take-off. I had been flying in heavy rain for hours the other day.
>
> Unless thing have changed is Jyrki the only one who understands
> English, if he's not available you are on your own.
>
> After my incident Woodcomp banned the Smart Avionic controller. What
> that means is unclear to me. As far as i know, they never got there
> own controller working decently.
>
> As for the figures, i've had trouble to keep up with a 912 with a
> fixed prop and i was flying with a 914 and a Woodcomp 3000. The only
> good figure seems to be the price.
>
> So in short: Save a few, risk your plane and life.
> The choice is yours....
>
> Regards,
>
> Jos Okhuijsen
> (enjoying his second life :-)
>
> . 26.6.2011 19:16, Frans Veldman kirjoitti:
>
> Veldman<frans@privatepilots.nl <mailto:frans@privatepilots.nl>>
>
> On 06/26/2011 04:02 PM, Paul McAllister wrote:
>
> I was very impressed with the results that David Joyce got with his SR
> 3000W propeller from Woodcomp. I would like to some feedback from the
> forum about there after sales experience from Woodcomp. Please give me
> the 'good, the bad and the ugly'
>
> I got excellent support and advice when I was ordering the propeller
> from Woodcomp directly and delivery was prompt. After that I had no
> reason to contact them again as the prop works flawlessly and performs
> better than expected. Had to service it at 50 hours and did that at a
> local Woodcomp dealer. Found that one spinner screw was missing and got
> a complete new spinner fastening set free of charge. Ordered spare
> brushes, but at the 100 hour check I discovered that the brushes were
> almost like new and it looks like it is going to take a long while
> before I have to replace them.
>
> Have now 100+ hours but have had no issues with the prop.
> A few notes though:
> 1) I'm using the controller from Smart Avionics which is very
> configurable and able to match the prop exactly to the engine/airframe
> characteristics.
> 2) I have a prop with feather capability (to anticipate a potential
> future use of the glider wings). The props with feather capability have
> a stronger and faster motor. Maybe this is the reason why the Woodcomp
> prop behaves like a hydraulic prop and reacts so fast that it never
> allows the RPM to surge off its target.
>
> Hope this helps,
>
> Frans
>
>
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