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Date: Thu, 16 Feb 2012 08:08:48 -0500
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From: cwfmd@yahoo.com
Subject: 4P flight control pressure
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Looking back on engineering and test (before paint and upholstery), the 4P =
flight control system must have been designed for an ES or IV(sans P), and =
pressurization added later. Otherwise, priorities are out of order. It is f=
airly unusual to have cabin pressurization influence trim and control stiff=
ness. We generally start to notice it at high altitude( > FL180), especiall=
y in a higher speed enroute descent, where aero loads add to the feedback o=
f heaviness, especially on the roll control.
=A0Anybody look at fixing this?=A0=A0 Fly by wire?=A0 Fly by light?=20
=A0Occam says a rotating bearing might achieve a better seal and force tran=
sfer mechanism that a push pull with=A0 bellows, compensating pistons, atta=
ched to=A0 a counter pressure hose!=20
But then, Hydraulic connections(across pressure bulkhead) might be better i=
n a retro-fit, and permit feedback for both trim, fly by wire, and autopilo=
t,
R/ Bill

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<table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D"=
top" style=3D"font: inherit;">Looking back on engineering and test (before =
paint and upholstery), the 4P flight control system must have been designed=
 for an ES or IV(sans P), and pressurization added later. Otherwise, priori=
ties are out of order. It is fairly unusual to have cabin pressurization in=
fluence trim and control stiffness. We generally start to notice it at high=
 altitude( &gt; FL180), especially in a higher speed <span>enroute</span> d=
escent, where aero loads add to the feedback of heaviness, especially on th=
e roll control.<br>&nbsp;Anybody look at fixing this?&nbsp;&nbsp; Fly by wi=
re?&nbsp; Fly by light? <br>&nbsp;Occam says a rotating bearing might achie=
ve a better seal and force transfer mechanism that a push pull with&nbsp; b=
ellows, compensating pistons, attached to&nbsp; a counter pressure hose! <b=
r>But then, Hydraulic connections(across pressure bulkhead) might be better=
 in
 a retro-fit, and permit feedback for both trim, fly by wire, and autopilot=
,<br>R/ Bill<br></td></tr></table>
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