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<p>Rummaging around the internet, I found at:</p>
<p><a class="moz-txt-link-freetext" href="https://aviation.stackexchange.com/questions/15662/how-does-flight-control-surface-authority-change-with-aoa">https://aviation.stackexchange.com/questions/15662/how-does-flight-control-surface-authority-change-with-aoa</a></p>
<p>the following text:</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
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0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;">Control authority is a function of the local dynamic
pressure (the product of air density and speed squared), geometry
(the product of control surface area and lever arm), local angle
of attack<span> </span><span class="MathJax_Preview"
style="margin: 0px; padding: 0px; border: 0px none; font-style:
inherit; font-variant: inherit; font-weight: inherit;
font-stretch: inherit; line-height: inherit; font-size: 15px;
vertical-align: baseline; box-sizing: inherit; color: inherit;
background: inherit;"></span><span class="MathJax"
id="MathJax-Element-6-Frame" tabindex="0" data-mathml="<math
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role="presentation" style="margin: 0px; padding: 0px; border:
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display: inline; text-indent: 0px; text-align: left;
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0px; min-height: 0px; position: relative;"><nobr
aria-hidden="true" style="box-sizing: inherit; transition:
none 0s ease 0s; border: 0px; padding: 0px; margin: 0px;
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class="mi" id="MathJax-Span-13" style="margin: 0px;
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style="margin: 0px; padding: 0px; border: 0px
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style="margin: 0px; padding: 0px; border: 0px none;
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style="margin: 0px; padding: 0px; border-width: 0px;
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inherit; font-variant: inherit; font-weight: inherit;
font-stretch: inherit; line-height: normal; font-size:
15px; vertical-align: -0.063em; box-sizing: content-box;
transition: none 0s ease 0s; display: inline-block;
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width: 0px; height: 0.67em;"></span></span></nobr><span
class="MJX_Assistive_MathML" role="presentation"
style="margin: 0px; padding: 0px; border: 0px none;
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inherit; font-stretch: inherit; line-height: normal;
font-size: 15px; vertical-align: 0px; box-sizing: content-box;
top: 0px; left: 0px; clip: rect(1px, 1px, 1px, 1px); position:
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the angle of deflection<span> </span><span class="MathJax_Preview"
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id="MathJax-Element-7-Frame" tabindex="0" data-mathml="<math
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role="presentation" style="margin: 0px; padding: 0px; border:
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font-weight: normal; font-stretch: inherit; line-height: normal;
font-size: 15px; vertical-align: baseline; box-sizing: inherit;
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aria-hidden="true" style="box-sizing: inherit; transition:
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none 0s ease 0s; display: inline-block; position: static;
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0px; padding: 0px; border: 0px none; font-style: inherit;
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inherit; line-height: normal; font-size: 18.3px;
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0px;"><span style="margin: 0px; padding: 0px; border: 0px
none; font-style: inherit; font-variant: inherit;
font-weight: inherit; font-stretch: inherit;
line-height: normal; font-size: 18.3px; vertical-align:
0px; box-sizing: content-box; transition: none 0s ease
0s; display: inline; position: absolute;
text-decoration: none; clip: rect(1.861em, 1000.44em,
2.79em, -999.997em); top: -2.456em; left: 0em;"><span
class="mrow" id="MathJax-Span-15" style="margin: 0px;
padding: 0px; border: 0px none; font-style: inherit;
font-variant: inherit; font-weight: inherit;
font-stretch: inherit; line-height: normal; font-size:
18.3px; vertical-align: 0px; box-sizing: content-box;
transition: none 0s ease 0s; display: inline;
position: static; text-decoration: none;"><span
class="mi" id="MathJax-Span-16" style="margin: 0px;
padding: 0px; border: 0px none; font-style: italic;
font-variant: inherit; font-weight: inherit;
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font-size: 18.3px; vertical-align: 0px; box-sizing:
content-box; transition: none 0s ease 0s; display:
inline; position: static; text-decoration: none;">𝜂</span></span><span
style="margin: 0px; padding: 0px; border: 0px none;
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line-height: normal; font-size: 18.3px;
vertical-align: 0px; box-sizing: content-box;
transition: none 0s ease 0s; display: inline-block;
position: static; text-decoration: none; width: 0px;
height: 2.462em;"></span></span></span><span
style="margin: 0px; padding: 0px; border-width: 0px;
border-top-style: initial; border-right-style: initial;
border-bottom-style: initial; border-left-style: solid;
border-color: initial; border-image: initial; font-style:
inherit; font-variant: inherit; font-weight: inherit;
font-stretch: inherit; line-height: normal; font-size:
15px; vertical-align: -0.263em; box-sizing: content-box;
transition: none 0s ease 0s; display: inline-block;
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width: 0px; height: 0.87em;"></span></span></nobr><span
class="MJX_Assistive_MathML" role="presentation"
style="margin: 0px; padding: 0px; border: 0px none;
font-style: inherit; font-variant: inherit; font-weight:
inherit; font-stretch: inherit; line-height: normal;
font-size: 15px; vertical-align: 0px; box-sizing: content-box;
top: 0px; left: 0px; clip: rect(1px, 1px, 1px, 1px); position:
static; height: 1px !important; width: 1px !important;
overflow: hidden !important; display: inline; transition: none
0s ease 0s; text-decoration: none;"><math
xmlns="http://www.w3.org/1998/Math/MathML"><mi>η</mi></math></span></span><span> </span>and
the relative flap chord. Generally, the control surface works
fairly linearly in a range between<span> </span><span
class="MathJax_Preview" style="margin: 0px; padding: 0px;
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class="MathJax" id="MathJax-Element-8-Frame" tabindex="0"
data-mathml="<math
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role="presentation" style="margin: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant: inherit;
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display: inline; text-indent: 0px; text-align: left;
text-transform: none; letter-spacing: normal; word-spacing:
normal; overflow-wrap: normal; white-space: nowrap; float: none;
direction: ltr; max-width: none; max-height: none; min-width:
0px; min-height: 0px; position: relative;"><nobr
aria-hidden="true" style="box-sizing: inherit; transition:
none 0s ease 0s; border: 0px; padding: 0px; margin: 0px;
max-width: none; max-height: none; min-width: 0px; min-height:
0px; vertical-align: 0px; line-height: normal;
text-decoration: none; white-space: nowrap !important;"><span
class="math" id="MathJax-Span-17" style="margin: 0px;
padding: 0px; border: 0px none; font-style: inherit;
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0px; padding: 0px; border: 0px none; font-style: inherit;
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inherit; line-height: normal; font-size: 18.3px;
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none 0s ease 0s; display: inline-block; position:
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0px;"><span style="margin: 0px; padding: 0px; border: 0px
none; font-style: inherit; font-variant: inherit;
font-weight: inherit; font-stretch: inherit;
line-height: normal; font-size: 18.3px; vertical-align:
0px; box-sizing: content-box; transition: none 0s ease
0s; display: inline; position: absolute;
text-decoration: none; clip: rect(1.587em, 1006.56em,
2.79em, -999.997em); top: -2.456em; left: 0em;"><span
class="mrow" id="MathJax-Span-18" style="margin: 0px;
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class="mo" id="MathJax-Span-19" style="margin: 0px;
padding: 0px; border: 0px none; font-style: inherit;
font-variant: inherit; font-weight: inherit;
font-stretch: inherit; line-height: normal;
font-size: 18.3px; vertical-align: 0px; box-sizing:
content-box; transition: none 0s ease 0s; display:
inline; position: static; text-decoration: none;">−</span><span
class="mn" id="MathJax-Span-20" style="margin: 0px;
padding: 0px; border: 0px none; font-style: inherit;
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font-stretch: inherit; line-height: normal;
font-size: 18.3px; vertical-align: 0px; box-sizing:
content-box; transition: none 0s ease 0s; display:
inline; position: static; text-decoration: none;">15</span><span
class="texatom" id="MathJax-Span-21" style="margin:
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class="mrow" id="MathJax-Span-22" style="margin:
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inherit; font-variant: inherit; font-weight:
inherit; font-stretch: inherit; line-height:
normal; font-size: 18.3px; vertical-align: 0px;
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0s; display: inline; position: static;
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inherit; font-variant: inherit; font-weight:
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class="mo" id="MathJax-Span-24" style="margin: 0px;
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class="mo" id="MathJax-Span-26" style="margin: 0px;
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class="mn" id="MathJax-Span-27" style="margin: 0px;
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class="texatom" id="MathJax-Span-28" style="margin:
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class="mrow" id="MathJax-Span-29" style="margin:
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height: 2.462em;"></span></span></span><span
style="margin: 0px; padding: 0px; border-width: 0px;
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15px; vertical-align: -0.263em; box-sizing: content-box;
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class="MJX_Assistive_MathML" role="presentation"
style="margin: 0px; padding: 0px; border: 0px none;
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font-size: 15px; vertical-align: 0px; box-sizing: content-box;
top: 0px; left: 0px; clip: rect(1px, 1px, 1px, 1px); position:
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0s ease 0s; text-decoration: none;"><math
xmlns="http://www.w3.org/1998/Math/MathML"><mo>−</mo><mn>15</mn><mrow><mo>°</mo></mrow><mo><</mo><mi>η</mi><mo><</mo><mn>15</mn><mrow><mo>°</mo></mrow></math></span></span><span> </span>for
a relative flap chord of 25% rsp.<span> </span><span
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role="presentation" style="margin: 0px; padding: 0px; border:
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0px; min-height: 0px; position: relative;"><nobr
aria-hidden="true" style="box-sizing: inherit; transition:
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class="math" id="MathJax-Span-31" style="margin: 0px;
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0px; padding: 0px; border: 0px none; font-style: inherit;
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none 0s ease 0s; display: inline-block; position:
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0px; box-sizing: content-box; transition: none 0s ease
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class="mo" id="MathJax-Span-40" style="margin: 0px;
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class="mn" id="MathJax-Span-41" style="margin: 0px;
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style="margin: 0px; padding: 0px; border-width: 0px;
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class="MJX_Assistive_MathML" role="presentation"
style="margin: 0px; padding: 0px; border: 0px none;
font-style: inherit; font-variant: inherit; font-weight:
inherit; font-stretch: inherit; line-height: normal;
font-size: 15px; vertical-align: 0px; box-sizing: content-box;
top: 0px; left: 0px; clip: rect(1px, 1px, 1px, 1px); position:
static; height: 1px !important; width: 1px !important;
overflow: hidden !important; display: inline; transition: none
0s ease 0s; text-decoration: none;"><math
xmlns="http://www.w3.org/1998/Math/MathML"><mo>−</mo><mn>25</mn><mrow><mo>°</mo></mrow><mo><</mo><mi>η</mi><mo><</mo><mn>25</mn><mrow><mo>°</mo></mrow></math></span></span><span> </span>for
a relative flap chord of 15%. Interpolate for values in between.
Note that flap effectiveness is proportional to the square root of
the relative flap chord, such that a flap of 15% needs twice the
deflection angle to effect the same control authority than a flap
of 60% relative chord.</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;"><br>
</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;">I haven't a clue whether this is correct but it does
suggest that control authority depends on local aerodynamic
pressure. So I ask again, assuming that reduced stick force
reflects reduced forces acting on the HS and elevators, then it
would appear that local aerodynamic pressure is reduced. And if
so, according to the quoted text, presumably control authority
will have been reduced.</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;"><br>
</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;">So, in 737 MAX with MCAS not in operation, when the
stick force reduces while the nose pitches up, how close is the
overall system to a trajectory through its phase space that enters
a deep stall?</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;"><br>
</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;"><br>
</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;">If nobody here can answer this, then I'd suggest that
we're all wallowing in our own ignorance-induced BS.</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;"><br>
</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;">Olwen</p>
<p style="margin-top: 0px; margin-right: 0px; margin-bottom:
var(--s-prose-spacing); margin-left: 0px; padding: 0px; border:
0px none; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-variant-numeric: inherit;
font-variant-east-asian: inherit; font-weight: 400; font-stretch:
inherit; line-height: inherit; font-size: 15px; vertical-align:
baseline; box-sizing: inherit; clear: both; color: rgb(36, 39,
41); letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); text-decoration-style: initial; text-decoration-color:
initial;"><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 03/12/2020 16:06, Grazebrook, Alvery
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAN4+gRY=6-=1SHF6hGYA04vkj55xK1h5cXsJArjCA59biww=MQ@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">
<div dir="ltr">Sorry - that was badly worded - the MAX (they
say) isn't unstable. I guess it's more like critical damping -
not enough damping leads to a higher risk of an overshoot, but
still ultimately stable.<input name="virtru-metadata"
type="hidden"
value="{"email-policy":{"state":"closed","expirationUnit":"days","disableCopyPaste":false,"disablePrint":false,"disableForwarding":false,"enableNoauth":false,"persistentProtection":false,"expandedWatermarking":false,"expires":false,"isManaged":false},"attachments":{},"compose-id":"7","compose-window":{"secure":false}}">
<div><br>
</div>
<div>Cheers,</div>
<blockquote style="margin:0 0 0 40px;border:none;padding:0px">
<div>Alvery</div>
</blockquote>
</div>
<br>
<div class="gmail_quote" style="">
<div dir="ltr" class="gmail_attr">On Thu, 3 Dec 2020 at 16:03,
Grazebrook, Alvery <<a
href="mailto:alvery.grazebrook@airbus.com"
moz-do-not-send="true">alvery.grazebrook@airbus.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div dir="ltr">Hi Olwen,
<div><br>
</div>
<div>Authority and Stability are different things.
Authority still exists in an unstable aircraft. The
problem is that the authority also includes positive
feedback. The loss of authority in a high-tail
aircraft is caused when the tail is so much in the
turbulence of the wing that it doesn't matter what you
do to the elevator, it has no significant effect. The
MAX problem is different. No loss of authority, but
loss of stability. This occurs when the centre of lift
is in-front of the centre of mass. At this point, a
movement of the elevator will produce a rotation
effect that increases with increasing AoA. It's quite
possible to correct this by reversing the movement,
but it is likely that a human will over-correct. </div>
<div><br>
</div>
<div>Cheers,</div>
<blockquote style="margin:0px 0px 0px
40px;border:none;padding:0px">
<div>Alvery</div>
</blockquote>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Thu, 3 Dec 2020 at
13:57, Olwen Morgan <<a
href="mailto:olwen@phaedsys.com" target="_blank"
moz-do-not-send="true">olwen@phaedsys.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex"><br>
On 03/12/2020 12:43, Dewi Daniels wrote:<br>
><br>
><br>
> That isn't what is meant by a deep stall. A deep
stall is one in which <br>
> the elevators have no authority,<br>
<br>
<br>
If the aircraft is in a condition where there is much
reduced force on <br>
the column due (presumably) to much reduced
aerodynamic pressure on the <br>
HS and elevators, does this not constitute, if not
loss of authority, <br>
then at least much reduced authority?<br>
<br>
Once again, I'm trying to get at what kind of flight
physics is going on <br>
with the 737 MAX airframe.<br>
<br>
<br>
olwen<br>
<br>
<br>
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