Report of the Second Piloted Aircraft Flight Control System - Acgsc.org

CENTERING CHARACTERISTICS OF POWER BOOSTED
AIRCRAFT CONTROL SYSTEMS
Within fi basically different aircraft, the Glenn L. Hartin Cagp~y h e
designed and put into service 30 different pouered surface control system of
Mch 1S wore power operated. The remnining fi power boosted surface control
eystsaPs have presented an umwual combination of requiremanta for sensitivity,
stability, and oenterlng, To meet such requiranants while m&Lntabing a
simple, reliable mchanlsm, devoid of functionally oanplicated acoeesaries,
the designer muat provide the optimtun system arrangement Md go to a high
degree of reiinemant in designing the elements.
i
The design considerations in a powa: boost& Waft controls ayutcrn
are as follows:
1. To provide optimum sensitivity and tbe correct amount of ponm at
all coaPbinatlo~ of speed and load.
2. To prevent any fom of imtability such aa ohattor or hunt Yithkl
. the meohanism in spite of the rensitivity and 1w break-atmy
iriotion.
3. To obkin a high degme of system raversibility ro that th.
mechanism will accurately centor or return fo the t M podtion,
ud so that a good forcre gradlent will k felt by the pilot at vexy
low aerodynsrPic moments.
Theee considerations are close2 y interrelated by m~ll~r 6y8tem perpplbtms
which generally am determined by one consideration and haw a direct effeot
on the other tuo. Consideration #1 determines eyetan rate gain, drcuit
powor, and valve chprrcteriaticr, each of which has a dinat effmt upon
rtability (consideration #2). Stability ale0 concams the irlction or damp-
In# throughout the system, the point of application of the actuator, md the
method of obtaining proportional feel, each of which vitally affwte tho
csntsrlng charactaristics (considaration #3).
There an definite perfonaance requirement6 hlch rmst be mat for
sensitivity, stability, and cgltering to make any system ratirfmtary in
r&oe. The ability of the designer to maat .those roquiruaatr depend.
upon hlr undarrknding the effect of woh rymtsrp p.ramstw upon tb, roquirm
ds. For amupla, to nuke a Judioious deoidon mgardlnq the magnituda
md dlrtribution of fiiotion, the designer must &tormine the mulmum
pumisrible frlctlon pattorn from his ertabllahod oentoring roq-mmnb, -
nut det8rmlne by rnolysis or tat the mlnbmm Mction pattarn ro@s~d to
arintaln stabill*, and then he our establirh the quality aontrol llritr of
mation dtbin eaah el-t of the qmtau.
*
Centering charrctsrlrtlor M reford to harein ary be dofY.nod u the'
rolaWonahip be- force, podtion, and rate of motion of a oontrol ~ Ifrr
in the rlcinity of the tadmned neutral position, Tho oritioal paiotr
ordinarily oonai&nd rre u followst