Today's Message Index:
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0. 12:25 AM - What Listers Have Been Saying (Matt Dralle)
1. 03:28 AM - Re: Kitfox mishap in Colorado (Tom Beirne)
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| Subject: | What Listers Have Been Saying |
Wow! Many of the members making a List Support Contribution this year have been
using the Comments field to leave a personal message about the Lists. Thank
you! I have included a number of them below. Please read over a few and see
if you perhaps can echo some of the same sentiments regarding the value of the
Lists to you...
There is only a couple more days left for this year's List Fund Raiser and we're
still way behind previous years. If you've been waiting until the last minute
to show your support, Now is the Time! Please make your Contribution and pick
up a great gift at the same time!
By Credit Card or Paypal:
http://www.matronics.com/contribution
or By Personal Check:
Matronics / Matt Dralle
PO Box 347
Livermore, CA 94550-7227
Thank you in advance!!
Matt Dralle
Email List and Forums Administrator
Here is some of the great feedback members have been including along with their
personal Contributions this year...
Over the years, the info I have received from the RV-List has
saved me thousands of dollars, and dozens of hours of time by
helping me avoid bad purchases, pointing me at vendors with
low prices and excellent support, and providing solutions to
the typical head scratchers that you run into.
Kevin H
Valuable service. Best List(s) on the Internet!
George A
Please accept this token not as an indicator of what
this list has been worth to me this past year.
Lew G
Great information and entertainment.
Tim V
Thanks again for another great year of service. This
project would be beyond me if it were not for the list.
Moreover, the friendships I have found are worth their
weight in GOLD!
Robert B
Great support you provide to all the subscribers!
Freddie H
Read it every day.
PF B
Thanks for your excellent management of the Matronics
Lists! Your services are head and shoulders above the
rest.
James M
Without the "List", there would be no Kolb "community".
Bill T
Thanks, Matt, for a great service! I've been monitoring
and using the lists since 1999.
Richard D
Thanks for such a terrific site and for all the work and
effort you put into it.
John R
A great service year after year.
John D
..another year of fantastic service.
Jerry B
This list is a great resource.
Arden A
Great list.
James M
Lists were a great help while building HRII N561FS.
John S
Great resources for both the beginner and experienced.
George R
Good service.
Gary G
The List is an invaluable resource!
William C
AeroElectric list is a great source of info and learning!
Janice J
Thank you, Matt for being there for us making it all happen
on the List for so many years - Great JOB!
Sam S
Thank you for providing a great venue. You definitely hit
the nail on the head with your solicitation asking if
readers look forward to receiving the email digests. I
certainly do and when I move from a dreamer to a builder, I
expect the anticipation will only increase.
Joe S
Thanks for a Perfect working list.
Hans-Peter R
Great List
Bryan K
Such a great selection of valuable forums!
David G
Nice job!
Walt E
Good resource...
Robert P
Thank you for another great year!
Scott S
I could not do this without you...
Robert D
I believe I've been a list member for over a decade
now. Thanks for the service!
Tim L
Great List
Hendrik W
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| Subject: | Re: Kitfox mishap in Colorado |
>
> Well, that is not true. Beta is the angle of the propeller at 3/4 radius. A negative
Beta would result in reverse thrust.
>
> Propeller pitch can be specified in two different, but equivalent, ways. The
first is the blade angle, and the second is the pitch.
Not quite right, Alpha is the blade Angle of Attack
The term Beta in this usage means the following
On Turboprop aircraft with a constant speed prop, power lever settings between
flight idle and maximum power allow the prop governor to select the appropriate
blade pitch to maintain a set RPM and this is called the Alpha mode of operation.
When the power lever is moved below flight idle the lever directly controls
the pitch angle of the blades and this is referred to as Beta mode where the
pitch can be changed from the flight idle position to full reverse, also known
as Full Beta.
For those interested in propeller aerodynamics
In aerodynamics the Greek letter alpha is commonly used to denote the Angle of
Attack of an aerofoil (wing shape), that is the angle between the chord line and
the relative airflow. This is also true for propellers as they are really just
aerofoils in rotation, in this case the reference Alpha is taken at 75 percent
span from the centre of the hub.
Note that this is a completely separate measure to the blade pitch angle which
is a geometric angle of the blade relative to the plane of rotation of the prop.
Where Angle of Attack (or Alpha) will change with both the airspeed and RPM
the pitch angle remains constant,hence the term "fixed pitch". Constant speed
props operate differently by continually changing the blade pitch angle to achieve
a constant RPM.
As Alpha changes so too do the lift and drag properties, the most efficient use
of power is when the blade achieves its best lift to drag ratio. Every blade
design will have its own optimum Alpha for best lift to drag which, at a given
pitch angle, is dependent on relative airspeed and RPM. Thus a fixed pitch prop
is only operating at its most efficient at a given RPM and airspeed. One can
choose the best operating regime by setting the blade pitch angle to give max
efficiency at that speed and power setting. Ground adjustable props make this
a once per flight deal but In-flight adjustable (or variable pitch) props allow
the pilot to select the best pitch angle, and in doing so optimize Alpha for
the conditions.
What may surprise people is that a negative blade AoA can occur at positive blade
pitch angles because it is relative to the airflow and not the aircraft. At
zero airspeed a nearly flat pitch angle would be required to get negative Alpha
but as airspeed increases it can be achieved at coarser angles because as forward
airspeed increases at a given RPM the AoA of the blade decreases. Hence
at higher airspeeds the pilot will require a coarser blade pitch to keep the
prop working at its most efficient Alpha. Also because higher forward airspeeds
decrease AoA, if you take your in-flight adjustable prop in cruise flight and
send it to fully fine too quickly there is a good chance that it will achieve
negative thrust and provide a rather effective airbrake until the airspeed reduces
sufficiently and equilibrium is once again reached. This might not be too
good for your engine though.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=216855#216855
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