Message-ID: <361CF970.8F577509@map.com>
Date: Thu, 08 Oct 1998 13:42:08 -0400
From: John Quinlan <jquin@map.com>
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Subject: Wave Drag
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    I've got a quick question that has stumped my CFI and has my
curiosity up.  In the Jeppesen Private Pilot Manual, page 3-33 reads "In
high performance airplanes with pronounced sweepback, [the sweepback] is
used primarily to maintain the center of lift aft of the CG and reduce
wave drag when operating at speeds...above Mach 1".  Now granted in my
172 I've not quite hit that speed yet, but what in the world IS wave
drag?  They don't go on to explain it in the book.

    Well, that's my serious question, but one more here, any engineer
pilots out there that know why the Negative G tolerance for normal
aircraft certification is precisely specific at 1.52 NegG's and a
utility class aircraft 1.76 NegG's? (Jeppesen PPM  pp.3-62)   I realize
that exceeding these limits may cause structural damage and such, but
why did they pick these as their specific limit rather than 1.6 and
1.8?  Is that the maximum tolerance of a specific make or model???
Anyone know why that is the case?

    Thanks...

                        --John A. Quinlan

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<HTML>
&nbsp;&nbsp;&nbsp; I've got a quick question that has stumped my CFI and
has my curiosity up.&nbsp; In the Jeppesen Private Pilot Manual, page 3-33
reads "In high performance airplanes with pronounced sweepback, [the sweepback]
is used primarily to maintain the center of lift aft of the CG and reduce
<U>wave drag</U> when operating at speeds...above Mach 1".&nbsp; Now granted
in my 172 I've not quite hit that speed yet, but what in the world IS wave
drag?&nbsp; They don't go on to explain it in the book.

<P>&nbsp;&nbsp;&nbsp; Well, that's my serious question, but one more here,
any engineer pilots out there that know why the Negative G tolerance for
normal aircraft certification is precisely specific at 1.52 NegG's and
a utility class aircraft 1.76 NegG's? (Jeppesen PPM&nbsp; pp.3-62)&nbsp;&nbsp;
I realize that exceeding these limits may cause structural damage and such,
but why did they pick these as their specific limit rather than 1.6 and
1.8?&nbsp; Is that the maximum tolerance of a specific make or model???&nbsp;
Anyone know why that is the case?

<P>&nbsp;&nbsp;&nbsp; Thanks...

<P>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
--John A. Quinlan</HTML>

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