Considering both factors, it's simply smart flying to keep the
"excursions" from normal flight to an absolute minimum. This is not to say
that the airplane will fall apart on you if you do a little "not straight
and level" flying with it, but it does say that doing this in aging
airplanes can increase that aging process somewhat.

Good point. This is something that concerns me, and I suspect I'm not
alone. Here's one recent experience that made me wonder about our aging
airframe.

While departing Iowa City last month, another pilot reported his position as
being 3 miles Southeast of the field, maneuvering. Since we were departing
to the Northeast, we determined that he would not be a factor.

Not! As we were climbing out, our direction-challenged fellow pilot became
visible in the haze, and I saw that he was on an intercept course -- with us
as the target.

For the first time in our flying lives (10 years, 1500+ hours), Mary and I
experienced an in-flight disagreement over what to do. She, in the left
seat, saw no reason for evasive maneuvers, determining that the plane would
pass over us with room to spare. I, in the right seat, saw the plane
growing larger in my starboard-side window by the second.

After a few more seconds of debate, I ended the discussion by pushing my
yoke firmly forward, inducing negative G and allowing us to pass harmlessly
beneath the traffic. We cleared the plane with room to spare.

Would we have hit him without my action? Probably not. Nevertheless, we
decided (after much debate) that I had acted correctly, given the
circumstances, since it fit into our pre-arranged agreement that the right
seater doesn't ever touch the controls unless they feel that their inaction
would put the plane at risk.

However, I did (and still) wonder about putting that much negative-G on our
34 year old airframe. Without a G meter it's impossible to know how much G
was induced, but I'd say it was 50% more than I've ever done before. (The
only negative G maneuver I ever do is the push-over at the top of a steep
pull-up, known by my kids as an "Up-Down".) Was 50% more too much?

We were climbing out, so our airspeed was relatively low -- probably around
80 knots. The entire maneuver lasted less than 5 seconds, and nothing
floated in the cockpit -- but in an old airplane, how much is too much?

As another reference point (and a crude way of measuring the negative Gs), I
routinely read about guys doing the "up-down" maneuver to the point where
their engine sputters due to fuel starvation. I've *never* done the
maneuver to that degree, even in this situation (although that may be due to
the short duration of the maneuver) -- so I'm assuming that I didn't push
the airframe beyond structural limits. Since that flight I've carefully
inspected the empennage, and there is obviously no visible stress or strain,
or I wouldn't be flying it -- but how can you really know without extensive
metallurgic testing?

If you've ever looked at the stabilator attachment on a Cherokee you will
marvel at the simplicity and apparent fragility of the design, so inducing
excessive negative-G is something we never, ever do. However, even though
there is (to my knowledge) no record of a stabilator departing the airframe
of a Cherokee, you've got to wonder how many days (weeks? months?) a sudden
push-over takes off the life of an airframe?

Thanks for the post, Dudley. As always, you have introduced a
thought-provoking angle to the discussion.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"