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Date: Wed, 12 Mar 2008 09:53:02 -0400
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From: "John Barrett" <2thman@cablespeed.com>
Subject: re: Spoilers
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Jeff writes:
  Well you had to ask so here is my .02 cents.
    1. Why reinvent the wheel? The electric speed brakes offered by =
Precise
Flight work well and already are engineered into the design of the IVP.
Unless, of course, you (like the rest of us) just like doodling in the =
shop.
(BTW-- I have your carbinge hinges and they are great!)
    2. How are you going to plumb the hydraulic lines? I imagine you =
will
use the existing hydraulic system for hydraulic pressure. Three distinct
disadvantages:
  ?????? a. it is bound to be heavier than the existing electric system
  ?????? b. it will likely result in an increase in the likelihood of a
hydraulic failure. This?is not good. A hydraulic failure will probably
result in a gear up landing. IMHO the hydraulic system has one purpose. =
Put
the gear "up" and most importantly "down". Anything else results in a
greater chance of that not occuring.
  ?????? c. I just pulled my wings off to rewire them for deice. I =
cannot
imagine chasing a hydraulic leak in the wing.
 *************=20
  Thanks for the input Jeff.  Your comments are well taken.  When I =
built
these I did not consider one additional use of the hydraulics as a =
safety
hazard.  They now perform three functions: gear, flaps, and spoilers.  =
You
point out that Prescise Flight brakes would be better and maybe lighter. =
 I
doubt they are lighter but they might be.  The only significant added =
weight
for the spoilers include one small poppet valve, a spool valve and 2 =
small
hydraulic cylinders.  The tubing is fairly short and there's not much =
else
in the spoiler system.  Seemed smart to take advantage of a system =
already
there.  Your observation about hydraulic safety is a new thought process =
for
me.  When I flew fighers in the Navy back in the '60's we thought we had
more sophisticated aircraft because the controls were hydraulic.  =
However,
recalling the commercial aircraft that crashed in the late '90s because =
all
three redundant hydraulic systems were cut in the tail section - was =
that an
L-1011?) and they landed with differential power saving most of the =
PAX's
may give cause to think of hydraulics as a necessary evil.  Have to give
this one some serious thought!=20

At the time I installed this system around '97 or '98, the Precise =
Flight
speed brakes were cable operated and were not satisfactory to me.  They
usually would not retract completely once deployed until you put the
airplane on the ground.  It took Bill Maddox to design a decent speed =
break
in a box and then Precise Flight apparently copied his ideas.
Unfortunately, Bill had not built his invention until after I'd already
installed most of my system.  I likely would have used his technology if =
it
had been available.

Anyway thanks for these and  all your good comments.

Oh yeah, and I do like doodling in the shop - apparently :)

Regards,
John Barrett


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