Hi Jos.
Thanks for your prompt reply.
I think you have cleared up my problem I could not see how a limit switch
failure could cause the blade angle to change if the blade was within its
normal operating range. Yes a limit switch failure could allow the blade
to travel beyond its normal limit but the pitch change motor would still
have to be driven ( commanded or uncommanded ) to move the blades beyond
their normal range. This was the part I did not understand. As the Smart
controller in its normal ie not in manual control, acts as a closed loop
servo system with a given engine RPM as its target it should have increased
the pitch as the RPM approached the target, I may be wrong but I would NOT
have expected the blades to reach their fine pitch limit at that phase in
the flight .
As to my expertise I do not claim to be an expert in anything at all. But I
do have experience, I was trained by the Royal Air Force as an airborne
radar technician and spent ten years ( admittedly forty years ago !)
working in what was then Signals Command on a electronic counter measures
squadron. On leaving the Air Force I was for seven years a Flight Trials
Engineer with British Aerospace military aircraft division commissioning
developing and maintaining what was then the worlds first digital airborne
data acquisition system. In later years I worked on large format printing
systems using both analogue and digital servo systems.
We have to accept that homebuilt aircraft are not as reliable and safe as a
fully certified one and we therefore take on extra risk with our types of
aircraft. In the UK we try minimise the risk by having our association
double check that our alterations from the standard design appear to be safe
and the changes are justified.
You mention the RPM reached 6,200 just a little story I was told by a friend
who is no longer with us. He operated out of a small strip and set his
propeller to reach max RPM of 5,800 and flew it like that for some years he
then had reason to have his RPM gauge calibrated and found that what he
thought was 5,800 was actually 6,200. his gauge had never been calibrated
and was under reading
Enjoy your second life Jos
best regards
Tim H
On 26 June 2011 23:46, josok-e <josok-e@ukolo.fi> wrote
> Tim,
>
> I've sent the report to somebody who is German en fluently in English, on
> his offer to translate. This translation takes an incredible amount of time
> obviously.
> But, as a matter of fact, the investigator thanks me for diverting from my
> line of descent into an occupied office building to trees. The wreckage was
> badly burnt. He also reports that he had Woodcomp check the remains of the
> propellor, and that they stated that the blades "must have been at a flyable
> angle" Also there was no obvious fault with the engine. It has not been
> possible to determine what the cause of the accident was. You may doubt of
> course that i have summarized properly as well.
> Significant might be also that after the accident Rotax was the first to
> talk to me, smartavionics next, the factory was very interested also. But no
> question, no word from Woodcomp.
>
> I find it strange that you start an argument by telling us that you are not
> an expert. And reach a conclusion, which is false. I am an expert,
> electricity, electronics have been my profession and hobby. I know
> microswitches and diodes, and if i tell you they are grossly underrated and
> not up wet conditions, you can take my word for it.
>
> My only interest is to save your lives. If you don't want it, please let me
> know.
>
> So, let me explain how the prop ended in a non-flyable position, so simple
> that a non-expert can understand. I commanded via the controller to go
> finer. That makes the motor run the blades to fine. The motor runs then as
> long as the controller command it to go finer or the fine limit switch cuts
> the current. In this case, because the desired rpm was high, and i was
> climbing, the fine limit switch should cut in. But it didn't because it was
> burnt, and short circuited to earth. The controller reversed it voltage to
> increase pitch and we had a short circuit on the plus now. The
> circuitbreaker popped. The revs went to 6200, with no pull. Attempting to
> reset it booted the controller. Which proved it was still working, And after
> the boot it popped again, The accident conditions were there, low on
> altitude, low on speed.
>
> I find it amazing that people defend such a product. Everybody i spoke to
> privatly admids there have been problems with communication, with quality of
> parts, with forgotten or loose parts, splitting blades, whatever. Oh, of
> course, they will cut the blades in a banana form, or apple, or anything
> else you fancy as fast. Very flexible indeed.
>
> There is a good working product available, has been for years, factory
> choice, with only plusses but the price.
> Everybody makes a mistake, and i can admit it was my mistake to go on the
> cheap and settle for a Woodcomp.
>
> Regards,
>
> Jos
>
>
> 27.6.2011 0:25, houlihan kirjoitti:
>
>> 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:
>>
>> <josok-e@ukolo.fi>Hi <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:
>>
>> --> Europa-List message posted by: Frans
>> 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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