"John Carrier" wrote in message
. ..

A complex question. Units are, of course, not degrees. Issue, exactly
what equates to "zero" in the calculation? Usually the armament datum
line, waterline, or whatever the manufacturer chooses to call it. In the
case of the Turkey, the aircraft's envelope exceeds the AOA display limits
... you can be flying at pegged AOA, well sort of flying. Adverse yaw
could bite you pretty hard if you had a heavy hand. For that matter, the
old Phantom could be there too ... but not for very long. The point, your
assumption that the gauge equates to the envelope is faulty.

IIRC, aircraft attitude (as reflected on the VDI attitude indicator and
mirrored on the HUD) was about 11 degrees nose high in level flight at
optimum AOA, somewhere around 8 degrees on a 3 degree glideslope (anybody
with more recent time in the jet ... feel free to chime in with
corrections). The airplane had a pretty pronounced cocked-up attitude on
speed, but not necessarily more so than the Phantom. It also had a large
hook/eye value (which affected lens setting for the target crossdeck
pendant).

The Hornet (and its bigger friend, the Rhino) are the only USN aircraft I
know that actually display AOA in pure and simple degrees as opposed to
the artificial "units." Of course it's capable of sustaining prodigious
AOA, on the order of 55 degrees with the current control programming.

Approach speed for a carrier aircraft is a brew of several objectives.
You want to be as slow as is practical. Attitude on touchdown is
critical. You want to be comfortably faster than L/D max. You need to
preserve good visibility over the nose (a big driver in the F-8J in which
the engineers came up with one number and after a few T&E passes at the
ship had it lowered slightly for pilot vis).

R / John




Thank you John. Part of my confusion stems from this post, from
rec.aviation.military:

****************
"Units are the arbitrary form used to express angle of attack on some
systems. For example, the F14 flies a typical approach at 51 thousand pounds
more or less at 130kts at 15 units AOA. The T38 flies a typical approach at
9200lbs.at 155kts plus 1kt per each 100lbs fuel remaining 1000lbs. with
the indexer on speed ( Indexer shows green donut at .6 units AOA in the
Talon.) Basically, units are expressed as a decimal on the T38 between 0 and
1. (.6 is optimum for approach ). The F14 uses aoa units from 0 to 30. This
is roughly equivalent to a range from - 10 degrees to +40 degrees of
rotation of the aoa probe. The on speed indexer in the Turkey is amber
instead of green like the 38.

Hope this helps,

Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/Certificated Flight Instructor
Retired
****************

This implies (or mayb I inferred ;-) a linear relationship between units and
degrees, but I suppose there's no reason that would be mandatory... (and it
looks like it's not linear after all). I just thought 12 degrees nose up on
approach seemed... well, wrong. Even the F-16 comes in at "only" 13 degrees
AoA. I know the F-15E uses units as well, and comes in more nose-up than
most, but I have no idea how many degrees that is either. The rationale for
unist vs. degrees... who the hell knows. (I suppose it would have something
to do with precision and/or the need for a non-linear scale?) I appreciate
the info though about attitude on approach..
Scott