My mechanic -- a guy with over 40 years of experience as an IA, A&P,
grand champion home builder, and owner of an engine and prop shop --

Is he a pilot? airplane owner?

He's an expert pilot, and a very experienced owner. He has hand-built
several airplanes from scratch -- no "kit planes" for him. (His next
project will be to recreate -- from photos only -- a 1916 aircraft
that flew out of Grinnell, IA.)

They make it to TBO because they are flown many hours per week, the
numbers add up fast, and they are monitored, inspected and maintained
every 100 hours (which might be every other month) ... not simply
because flying them every day enables the engine to withstand doing the
"worst" possible thing 75% of the time it is in use.

Correct. That's what I was aiming to say, even it if didn't come out
quite right.

And you do half of that every time you take off and land. That doesn't
damage your engine, but the one extra application of power during a
touch-n-go or go-around is going to do your engine in?

Well, your engine has a limited number of those cycles in it. It's
the same thing I explain to my 17 year old son: Yes, you can floor
the car and spin the rear wheels a certain number of times, without
harming the engine. Sooner or later, though, that kind of treatment
*will* break something.

Airplanes are no different. Cycling from full power to idle is just a
bad thing to do with your engine.

Plenty of people practice touch-n-goes in their own airplanes ... if
they are THAT damaging to an engine, we'd be hearing of this engine
damage all the time. People with Cubs or other small tailwheels are out
doing touch-n-goes ALL THE TIME...doesn't seem to bother their engines.

Is this damage something you can quantify? When my buddy's engine
crapped out 700 hours before TBO, was it directly attributable to his
doing a zillion touch & goes?

I don't know, but I can safely say that if he had simply let his
engine run at a steady-state 2200 RPM, it would still be running
today. THAT is an indication of the wear and tear inherent with full
power/idle power engine management, versus cruise flight.

I understand and agree about inactivity and that most privately-owned
airplanes aren't flown enough. But you're saying that an engine that
flies for 8 hours/month and does touch-n-goes/engine-out practice during
ONE of those hours is more likely to be damaged than an engine that
flies 80 hours a month and does the damaging maneuvers during 60 of
those hours. If it's THAT bad, subjecting it to 60 hours a month would
still take a heavy toll even it flies every day.

I would agree with that. Full power/idle power cycles are very hard
on engines -- and that is what you're doing in a touch & go.

In fact, wasn't part of your training getting so familiar with
the airplane that you know how it acts and reacts to as many different
conditions/configurations as possible? How can you do that if you're
afraid that touch-n-goes or simulated engine failures are going to ruin
the engine?

Touch & goes aren't necessary to practice after your first 1000 or so
landings, IMHO. If you don't have it down pat by then, a few more
T&Gs isn't gonna help, and the beating your plane takes during the T&G
process is something to be avoided.

That's why airplane ads say stuff like "Never used as a trainer."

Engine out practice IS a good thing to do, however, and is why I do
feel badly about my reluctance to do them. I'm thinking maybe we'll
do some next time we go up, maybe at reduced (not idle) power...

I've never seen anything in my engine documentation that says it was
designed to be run every day.

Optimally, in order to run the longest possible number of hours, you
would never shut the engine off. I'll bet a Lycoming could run 10,000
hours easily if all you did was keep it running at 2000 RPM, and keep
adding oil and gas.

But that's not "real world". Looking at trainers at big flight
schools, they usually fly daily, often for many hours per day. And
they usually get some pretty impressive time on their engines that
way. (Hours-wise, not calendar-wise, of course.)

I just spent at least that much, too, and I'm sure as heck not going to
intentionally abuse the engine. But I'm not going to skip some aspects
of ongoing skill retention drills that I've seen the pay off firsthand
in an emergency because I'm thinking about the $20K I just spent.

Yep, I agree. You're the voice of experience here, which is why I'm
engaged in this thread. I *am* worried about not practicing the
procedures enough, but I just don't want to shorten the lifespan of a
very expensive engine needlessly...

In skating, we used to teach students that they could expect to lose up
to 25% of their actual ability/competence during their 4 minute routine
in a competition due to nerves and pressure; so if they wanted to show
the judges 100% of their capabilities, they have to be skating at 125%
in the weeks prior to the competition. I don't know if those numbers
translate to flying, but I think the concept itself does. I would hate
to lose a percentage of my ability in an actual emergency if I was only
at 80% to begin with. YMMV, of course. Everyone's different.

Agree. Staying sharp is your best defense.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"