How Long Can An Airplane Sit?

Bill,
The citabria I bought last year had been serviced regularly with exxon
elite semi-synthetic oil. I've continued using this product. According
to exxon, I'm a very smart guy Whether it really works or not remains
to be seen but even exxon recommends changing the oil before extended
periods of downtime and having a sample tested for water content every
60 days. I haven't had that done but I think I will. Check out their
admittedly biased website, exxonelite.com.
Dave
68 7ECA

Bill Denton wrote:
A pilot owns an airplane.

He isn't able to fly the plane very often, but when he does it's usually two
hours out for a $100 hamburger, then two hours back.

The airplane is always hangered; all inspections and maintenance are done by
the book.

How long could the airplane sit between flights before it begins to
deteriorate?

"Bill Denton" wrote in message ...

How long could the airplane sit between flights before it begins to
deteriorate?

At least every two weeks you need to fly it for at minimum 30 to 40
minutes. And if you're gonna fly it that very little much, then you
need to make those short flights at or above 75% power setting to make
sure the oil gets fully up to temperature to cook out any moisture.

Thanks to all who've posted so far. Unfortunately it appears I might not
have been very clear in what I was looking for. Please allow me to
clarify...

Our pilot wants to own his own airplane, and he doesn't want others to fly
it. Therefore he doesn't want to put it on leaseback or some other situation
that would increase the "flight frequency". The plane would only be flown
when he could fly it himself. Because his flying time is limited, whenever
he does have time to fly he would like to go to the airport, do a thorough
preflight, get in and go, while not sacrificing safety.

As several pointed out, corrosion begins as soon as you shut the engine
down. Let's assume our pilot has plenty of money and really enjoys flying,
so he is willing to accept even a 20% reduction in TBO in order to own his
own plane.

I noticed that engines were about the only things mentioned. We al so want
to consider all of the airplane, including tires, landing gear, lights,
instruments, avionics, and whatever else.

So let's look at it this way: how long could the airplane sit without
incurring extremely excessive wear or situations that would make the
airplane even slightly unsafe to fly?





"Bill Denton" wrote in message
...
A pilot owns an airplane.

He isn't able to fly the plane very often, but when he does it's usually
two
hours out for a $100 hamburger, then two hours back.

The airplane is always hangered; all inspections and maintenance are done
by
the book.

How long could the airplane sit between flights before it begins to
deteriorate?

"Bill Denton" wrote in message
...

So let's look at it this way: how long could the airplane sit without
incurring extremely excessive wear or situations that would make the
airplane even slightly unsafe to fly?

Quite honestly, if you are willing to accept the maintenance cost, it can
sit for a month or more. Many airplanes do not fly all winter. It helps if
the hangar is dry, etc.

I have seen airplanes, literally covered with moss, which have been sitting
outside in the grass for over a year in the moisture laden Puget Sound
region. Pump up the tires, check the battery, oil, and gas and get three
strong men to pull the plane out of the holes the landing gear made, and it
starts up and flies just fine. Granted, the plane needed an annual, but
there was nothing particularly unsafe about it. The cylinders showed no
corrosion.

"Stealth Pilot" wrote in message
...
lets blow away the mystery here. yes corrosion can start in a few
hours ....but why????

Because moisture is always present. No mystery...not sure why you say there
is.

Corrosion is a constant process, and the longer you go, the worse it is.

bull**** (and I mean that in the nicest way :-) )

Doesn't matter how nice you mean it...you're still wrong.

ok why??? what is the actual process going on here that makes the
running better?

Mostly it's the recurrent coating of corrosion-susceptible surfaces with
oil, protecting them from moisture. Again, no great mystery.

[...] I'm not aware of any unbiased
tests that would indicate one way or the other.

of course there are. you just havent read of them. :-) :-)

I'm all ears. Show me an unbiased report that compares efficacy of the
corrosion-preventative oils. I would love to be proved wrong, as such a
report would be very useful to aircraft owners.

moisture in the engine is primarily the bad guy here.
it condenses in the oil as the engine cools after use

It is also present in the air, and the engine not being a sealed
environment, humidity will get into the engine as it sits, regardless of how
much moisture got into the oil as a result of operating the engine.

[...]
the second time I took precautions to minimise water in the oil and
had no identifiable damage.

How did you attempt to identify the damage? Did you disassemble the engine
and inspect it for corrosion? Where was the airplane stored? Was it in a
desert (extremely low humidity) or in a coastal environment (high humidity)?

Regardless of the answers to the above questions, two years in service is
not enough time for you to notice the effects of corrosion. If you think
that corrosion did not occur in your engine during the second year it sat
unattended and unoperated, you are fooling yourself. The degree of
corrosion is highly variable, but to say that corrosion did not occur is
just stupid.

Pete

"Bill Denton" wrote in message
...
Thanks to all who've posted so far. Unfortunately it appears I might not
have been very clear in what I was looking for. Please allow me to
clarify...

Thank you. It's very hard to answer very vague questions.

I noticed that engines were about the only things mentioned. We al so want
to consider all of the airplane, including tires, landing gear, lights,
instruments, avionics, and whatever else.

So let's look at it this way: how long could the airplane sit without
incurring extremely excessive wear or situations that would make the
airplane even slightly unsafe to fly?

What CJ said. Most of the airplane is relatively immune to long-term
corrosion; aluminum winds up with a thin layer of oxidation that prevents
any further corrosion, and that's what most of the airplane is made of. In
a humid, salty environment (coastal) you may still get more significant
corrosion, but even so you can go months and months without anything serious
happening to most of the airplane.

The reason everyone's talking about the engine is that the engine is what's
most susceptible to sitting there. As far as the rest of the airplane goes,
the main things that will be affected are the battery and the tires. The
battery will gradually lose its charge, and discharging a lead acid battery
will shorten the battery's life. The tires will gradually lose pressure,
and even after relatively short periods of time (weeks) will develop a flat
spot (even if the pressure hasn't noticeably been lost during that time)
that you'll notice taxiing around and during takeoff; it will probably
return to its round shape by the time you land.

You can minimize the problem with the battery by charging it periodically
when the airplane's not going to fly. If the airplane's hangared, I
wouldn't sweat the tires too much, other than maybe checking the pressure
occasionally and adding air if necessary (at the extreme, if they get
completely deflated the weight of the airplane will be resting on the
rubber, squeezing it between the ground and the wheel hub, which isn't all
that good for the tire...but if it doesn't take an extraordinarily long time
for the tire to lose all its pressure, there's something wrong with it, like
a leaky valve stem, a puncture, or something).

Other stuff you mentioned, like landing gear, lights, instruments, and
avionics are all going to be basically unaffected, especially in a hangared
airplane (outside, in hot sun, some things like avionics and o-rings in
gas/oleo landing gear struts can bake and deteriorate).

One of your biggest concerns is probably the local wildlife finding the
airplane to be a desirable home. This is mostly a problem if the airplane
is kept outside, but even in a hangar, sometimes birds can find their way
in.

The bottom line here is that, while letting an airplane sit isn't exactly
good for it, it's not going to destroy it either. Most of the issues
associated with letting it sit will be economic, not safety-related. It's
not possible to economically justify owning an airplane if you don't fly it
often, and your annual inspections will, at a minimum, cost you much more
per flying hour than if you flew regularly, and there may be additional
costs due to the lack of use. The per-hour costs of an airplane that isn't
used regularly are likely to exceed the cost of a rental by a significant
amount, perhaps a factor of two or three or more.

So, for someone considering buying an airplane and not being able to fly it
regularly, personally I think the greater issue is the cost issue. By
taking appropriate steps, you can ensure that the airplane is safe, but
there's nothing you can do about the much greater cost that will be
incurred.

Pete

"Geoffrey Barnes" wrote in message
ink.net...
You have a voice annunciator for corrosion?

I've never heard of one of those. However, I have found a very effective
voice annunciator for flying too *often*. It's very sensitive, and it
adjusts the stridency of its warnings in direct proportion to both the
last
3-6 weeks of flying history and the amount of the previous month's flying
club bill. If not much flying has been going on, it stays quiet. If you
have flown only a little bit, it merely emits frustrated sighs as you
leave
for the airport. If you have been flying as much as you probably should
to
maintain currency, it begins speaking aloud, usually asking questions
like,
"Again?", and "So when are you going to get insert some non-flying task
here done?". And finally, if you have been flying as much as you wanted,
you will see the volume increase to ear-splitting levels, the voice
frequency reach into the soprano range, the questions turn into both
declarative statements and dire predictions, and the language evolve into
something that would make most sailors blush. As an added option, it can
also start throwing dishes, frying pans, and rolling pins at you.

My annunciator is called a "wife". If you want to buy mine, let me know!

Really honey, if you happen to catch this on Google, it was all a big
joke,
OK. No, no! Look, it was just a little joke. I thought the guys would
all
get a big laugh over it! I'll get the lawn cut as soon as the weather
clears up, I promise. What? Yes, dear. I'll get those shelves up right
now, dear. Yes, dear.

You been peeking in my windows?

Cub Driver wrote:

One week

If you can 't fly it every week, pickle the engine.

Sorry - but that's how it really is.

The same is true of the pilot, of course.

If you can't fly every week, pickle the pilot? I'll drink to that!

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

Geoffrey,
The good news is that this device can be removed.

The bad news is that it will cost you half of everything you own, except,
perhaps, the plane itself.


The good news is that it will be worth every penny!



"Geoffrey Barnes" wrote in
ink.net:

You have a voice annunciator for corrosion?

I've never heard of one of those. However, I have found a very
effective voice annunciator for flying too *often*. It's very
sensitive, and it adjusts the stridency of its warnings in direct
proportion to both the last 3-6 weeks of flying history and the amount
of the previous month's flying club bill. If not much flying has been
going on, it stays quiet. If you have flown only a little bit, it
merely emits frustrated sighs as you leave for the airport. If you
have been flying as much as you probably should to maintain currency,
it begins speaking aloud, usually asking questions like, "Again?", and
"So when are you going to get insert some non-flying task here
done?". And finally, if you have been flying as much as you wanted,
you will see the volume increase to ear-splitting levels, the voice
frequency reach into the soprano range, the questions turn into both
declarative statements and dire predictions, and the language evolve
into something that would make most sailors blush. As an added option,
it can also start throwing dishes, frying pans, and rolling pins at
you.

My annunciator is called a "wife". If you want to buy mine, let me
know!

Really honey, if you happen to catch this on Google, it was all a big
joke, OK. No, no! Look, it was just a little joke. I thought the
guys would all get a big laugh over it! I'll get the lawn cut as soon
as the weather clears up, I promise. What? Yes, dear. I'll get those
shelves up right now, dear. Yes, dear.


---
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Checked by AVG anti-virus system (http://www.grisoft.com).
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"Peter Duniho" wrote in message ...
"Bill Denton" wrote in message
...
Thanks to all who've posted so far. Unfortunately it appears I might not
have been very clear in what I was looking for. Please allow me to
clarify...

Thank you. It's very hard to answer very vague questions.

I noticed that engines were about the only things mentioned. We al so want
to consider all of the airplane, including tires, landing gear, lights,
instruments, avionics, and whatever else.

So let's look at it this way: how long could the airplane sit without
incurring extremely excessive wear or situations that would make the
airplane even slightly unsafe to fly?

What CJ said. Most of the airplane is relatively immune to long-term
corrosion; aluminum winds up with a thin layer of oxidation that prevents
any further corrosion, and that's what most of the airplane is made of. In
a humid, salty environment (coastal) you may still get more significant
corrosion, but even so you can go months and months without anything serious
happening to most of the airplane.

The reason everyone's talking about the engine is that the engine is what's
most susceptible to sitting there. As far as the rest of the airplane goes,
the main things that will be affected are the battery and the tires. The
battery will gradually lose its charge, and discharging a lead acid battery
will shorten the battery's life. The tires will gradually lose pressure,
and even after relatively short periods of time (weeks) will develop a flat
spot (even if the pressure hasn't noticeably been lost during that time)
that you'll notice taxiing around and during takeoff; it will probably
return to its round shape by the time you land.

You can minimize the problem with the battery by charging it periodically
when the airplane's not going to fly. If the airplane's hangared, I
wouldn't sweat the tires too much, other than maybe checking the pressure
occasionally and adding air if necessary (at the extreme, if they get
completely deflated the weight of the airplane will be resting on the
rubber, squeezing it between the ground and the wheel hub, which isn't all
that good for the tire...but if it doesn't take an extraordinarily long time
for the tire to lose all its pressure, there's something wrong with it, like
a leaky valve stem, a puncture, or something).

The trace of ozone in the air will attack the rubber and make
it brittle, and it cracks and the moisture can get into the cords and
weaken them. Covering the tires helps, and keeping them out of the sun
also reduces the reaction.

Other stuff you mentioned, like landing gear, lights, instruments, and
avionics are all going to be basically unaffected, especially in a hangared
airplane (outside, in hot sun, some things like avionics and o-rings in
gas/oleo landing gear struts can bake and deteriorate).

The bearing in the tach tends to dry out and seize up over time,
breaking the cable. Cockpit heat really kills the radios, and also
cooks the upholstery. Both take considerable time, but it's a shame to
see a 500-hour airplane in need of a complete refurbishing.


One of your biggest concerns is probably the local wildlife finding the
airplane to be a desirable home. This is mostly a problem if the airplane
is kept outside, but even in a hangar, sometimes birds can find their way
in.

Amen to that. Mice love our hangars here, as they afford protection
from the
cold winds in winter, and there is almost no way of keeping them out
except to use mothballs or something really objectionable like that.


Dan