On Jun 1, 8:54*am, Bob Whelan wrote:
On 5/31/2010 8:07 PM, Rolf wrote:

Over the years (30 or so) Caesar Creek Soaring Club has vacillated
with setting the altimeter to zero or MSL. Last year the Board decided
to put the Club ships on an MSL basis (private gliders exempted).
There are however a number of members who are continuing to make it an
issue. I would be interested in your thought and comments.

Wearing my dry humor hat just a bit...

Do we U.S.-ers live in a democracy? If yes, then the preponderance of
replies-to-now suggests your club whiners are outvoted. ('We' don't, for
the seriously curious and unknowing, but that's another topic entirely...)

Is CCSC run like a democracy? (You poor devils...)

I learned at an 800' msl gliderport/general-aviation field, long ago and
far away. I remember my instructor's first preflight instruction; it
included setting the altimeter to 0'. I asked, "Why not to field
elevation?" He gave me the, "It's easier for your puny, overworked
brain," answer. I said, "OK," and got with the program. (It was the
first time I ever disagreed with my instructor, though...)

Eventually it was solo time. I did so without breaking anything. Next
flight, Tom (my instructor, and not Knauff), hopped in back after I
preflighted and instructed me to set the altimeter to field elevation. I
asked, "Why?" He said, "Because now you're a fledged pilot, and real
pilots care how high they are above ALL the ground, not one single
airport in the entire United States." I'd cared all along, but I didn't
tell him so & silently complied. It confused me a nano-second or two
fretting about my 'new' pattern height while on tow, but I figured it
out and have never been confused since...well, about this particular
issue, I mean!

Fast forward to another mountain airport and another time... There I wuz
about to launch from a field at 8149' msl elevation, with a steenking,
howling crosswind of 20+ knots. Naturally, I didn't want to land right
off tow, so I decided I'd tow to 3,000' agl instead of my normal
2,000'...insurance against broken thermals and getting blown downwind
away from the only landable pace for miles around (i.e. the airport).

I pop off at what my poor overstressed brain said was 3000' agl, known
that instant to be an indicated 10,150' (I rounded up 'for safety's
sake'!), in a decent-feeling upwelling and begin grinding around,
keeping a beady eye on my drift relative to the field. I begin climbing
too, but for some reason I couldn't get comfortable as fast as I thought
my climb rate should be permitting...something about that lurking ground
bugged me. About 500' into my climb I realized it was because the ground
was WAY too close for being 3500' agl. Apparently my instructor had been
right about my 'puny overworked brain' all those years ago!

Or maybe I was just an idiot that particular day. Also, I like to think
I'd'a entered the pattern 'by eye' and not at 0' agl had that thermal
not worked for me.

Legality aside, use agl...*please!!!*

Flying's real safe so long as you don't inadvertently hit anything.
Though I don't know this for a fact, I'll bet my retirement that at
best, it'll be embarrassing to inadvertently hit the earth when your
'field level' altimeter suggests you're still OK.

Bob - sometimes 'common sense' isn't - W.

These days it'a mostly a non-issue. PDA-type glide computers, and
some built-in units, provide constantly updated AGL height since they
are loaded with a digital elevation map and know your GPS position.
Just make sure the local atmospheric pressure is set. Some even set
that for you at takeoff: (Hmm, GPS says I'm at BDU and we're not
moving so we must be on the ground which, according to my airport
database, is 5288' which means the station pressure is 29.92".)
Airborne, you can just listen to an AWOS to get station pressure.

BTW, that last bit, airborne altimeter setting, IMHO is the biggest
reason to set altimeters to MSL. Altimeters can only be set
accurately to MSL when airborne since that's the only station pressure
data anyone transmits. Professionals worked this out a long time
ago. It isn't up to us to figure out yet another way to do it.