 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
carl(at)flyers.freeserve.
Guest
|
 Posted: Wed Mar 18, 2009 8:18 am Post subject: Europa-List: Woodcomp Propellers |
 |
|
Hello Jos,
I was advised that all Woodcomp in flight adjustable propellers are set up
so that there is a physical stop which prevents each blade going outside the
specified operating range. The hub/ blades are set up at the factory to each
individual customer requirement. I understand there is a groove along the
circumference of the blade roots and the stops locate within the groove. The
length of the groove determines how far the blades can travel.
Most Woodcomp setups can only go from coarse to fine pitch because of the
length of the groove and consequently there is no risk of the blades
travelling outside the operating range.
The only Woodcomp props which can go into neutral or reverse are the ones
where the customer has specified this (ie: the reverse pitch option). My
prop (second hand) is one of the ones that have a longer groove and can
currently go past neutral (ie: superfine and reverse).
I believe your accident had a bearing on the PFA's decision to ban reverse
pitch propellers. My understanding is that no one has identified why these
propellers can go into an uncommanded reverse pitch situation and therefore
the ban would seem to be a perfectly sensible precaution.
As one who speaks from bitter experience I can understand your strong
feelings over this matter.
Best wishes,
Carl.
---
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
 |
carl(at)flyers.freeserve.
Guest
|
| Posted: Fri Mar 20, 2009 12:40 am Post subject: Europa-List: Woodcomp Propellers |
|
|
My Woodcomp propeller (the one I need to modify) is William Mills old one
(it was not fitted to his aircraft at the time of his accident). It is about
three years old and was probably one of the first to be fitted in the UK.
For the avoidance of doubt these propellers are definitely fitted with an
end stop mechanism. If you look at the photo there is a machined groove to
the right of the bronze coloured cog. There is an M6 bolt through the front
of the hub which locates in the groove limiting the blade travel.
The problem is that this prop has the facility for reverse thrust so the end
stop is of no use if the motor takes the blade beyond fine pitch. Thats why
I need to get it modified. I assume that your propeller Jos will have been
the same.
To say that there is no mechanical stop is untrue. The majority of Woodcomp
propellers have a shorter groove which limits the travel between coarse and
fine (or fine and feathered if it is the feathering variety). Anyone with a
"normal" Woodcomp prop has nothing to worry about in this respect.
If a motor burns out you have to question whether it was protected properly
with the correct rating fuse. If the motor is subjected to extreme demands
it will draw more current and blow the fuse before the windings failed. Were
such a failure occurr with the normal mechanical stop arrangement the
propeller would still be in the normal range, continue to produce thrust and
the aircraft should be flyable.
Knowing what I know now I would still buy the Woodcomp propeller again but I
would not fit a propeller (of any make) that didnt have mechanical end
stops.
Variable pitch propellers carry additional risks (compared to fixed). So
does flying!!! All you can do is try and minimise them.
The moral is dont fly with a prop that can go into reverse - it isnt worth
the doubtful advantages.
Carl Pattinson
G-LABS
_______________________________________
No viruses found in this outgoing message
Scanned by iolo AntiVirus 1.5.6.4
http://www.iolo.com
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
| Description: |
|
| Filesize: |
82.75 KB |
| Viewed: |
9127 Time(s) |
|
|
|
| Back to top |
|
|
carl(at)flyers.freeserve.
Guest
|
| Posted: Thu Mar 26, 2009 9:56 am Post subject: Europa-List: Woodcomp Propellers |
|
|
As David says there is definitely a groove and a limiting stop in Williams
prop - photos herewith..
I have just sent it back to Woodcomp for them to shorten the length of the
groove so the blades can't travel beyond the fine setting (ie: into reverse
pitch).
It isnt clear but the end stops are 6mm allen head bolts through the front
hub. These slot into the grooves limiting the blade travel.
It should be fairly obvious that if a prop is capable of going into reverse
pitch, a physical end stop wont prevent the blades going into a dangerous
condition if the servo motor continues to run past the fine setting.
Presumably that is the reason there is a backup microswitch which should cut
off the power if the primary switch fails.
However both the fine setting switches will be over ridden if the control
circuitry initiates reverse pitch !!! One assumes this would not normally
happen unless the reverse pitch switch was engaged (ie: by the pilot).
Carl Pattinson
---
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
| Description: |
|
| Filesize: |
35.26 KB |
| Viewed: |
9107 Time(s) |
|
| Description: |
|
| Filesize: |
56.67 KB |
| Viewed: |
9107 Time(s) |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
