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From: dsmith@hplabsc.UUCP (David Smith)
Newsgroups: net.aviation
Subject: Re: Acrobatics
Message-ID: <2658@hplabsc.UUCP>
Date: Fri, 26-Jul-85 17:41:05 EDT
Article-I.D.: hplabsc.2658
Posted: Fri Jul 26 17:41:05 1985
Date-Received: Sun, 28-Jul-85 06:41:27 EDT
References: <740@infopro.UUCP> <11624@brl-tgr.ARPA>
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Organization: Hewlett Packard Labs, Palo Alto CA
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> Regarding the "slow four-point roll" mentioned about the 707 -- this
> started me thinking in general terms about acrobatics. I'm sure this is
> obvious to those of you out there who have really studied aviation, but
> I have some novice questions:
> 
> 1) On the stages in a slow roll, where you hold the positions for some
> period of time, and where you are on your side: what is holding the
> airplane up? Momentum? Faith? (The wings are vertical at those times.)
> 
Watching the Blue Angels do this, they pull up just before they start the
roll, and fly an arc.  At the end of the roll, they have to pull out of a
shallow dive.  When they are knife-edged, the nose is up a bit, so I
suppose they get some lift out of the fuselage.


> 2) We have seen diagrams and descriptions of wing cross-sections and
> airfoils in basic physics classes, describing the differential airflow
> over the top and bottom, and how this creates lift. OK; so how does a
> plane fly inverted? Is it just by holding enough of an angle of attack
> that you get some lift from the inverted airfoil? 
> 
Yes.  High speed airfoils are fairly symmetric, although I suppose the
supercritical airfoils may be less so.  I once read of an exchange where
a pilot claimed his plane flew very well upside down, even better
than right side up.  To which the other pilot replied that the designers
must have done a poor job.

		David Smith
		ucbvax!hplabs!dsmith