EAA Sport Aviation - February 2010

would not believe how much smoke that little engine would put out. The more exhaust gas you put out the better. A really fast plane like a Mooney would not work well because you need to run at full power but still not go very fast. Most small planes that are not speed demons would work fine. You see, the faster you are going, the thinner the trail of smoke behind you, and you need thick billowing smoke.

Skywriting is relatively inexpensive. The only expenses are gasoline for the plane and some smoke oil. I do not claim to have invented smoke systems. They have been around much longer than I have. I do claim to have come up with a system that makes more smoke than anyone else. Basically, what you are doing to make all this smoke is pumping oil into your red-hot exhaust pipe. The oil will burn and put out smoke. Simply put, that’s all there is to it. I have made that process more efficient with a homemade smoke system and injectors. You’ll find the hardware list and instructions at www.SportAviation.org.

There are three types of oil used for skywriting, Exxon Coray 22, Texaco Canopus 13, and AeroShell Smoke Oil. It is usually only available in 55-gallon drums from a large petroleum bulk plant. Depending on how many barrels you buy, you could get the cost down to $5 per gallon.

Quite some time ago while at an air show I ran out of smoke oil, and there was no more on the field. In desperation I tried using some automatic transmission fluid purchased at a nearby gas station. It worked fine, but the cost was far too much to burn such expensive stuff. Use it for emergencies only. A while later on I had a bright idea. If new transmission fluid works, why not try some of the used stuff? To make a long story short, it works just as well as the new oil did. You cannot tell the difference in the amount of smoke generated by it and the $5 per gallon regular smoke oil.

But, there are some common sense considerations in using this nasty-looking stuff. First of all, transmission rebuilders usually sell their old oil for people to put on dirt roads to keep down dust or to burn in garage heaters or whatever. They usually get about 25 cents per gallon for it, and you must pump it out of their underground storage tanks yourself. These tanks are full of all kinds of dirt, water, floor sweepings, and solid objects like gasket material and such. The best way to get this oil is to furnish them with a barrel and a large funnel, and they will drain it directly into your barrel. Then you do not have nearly so much dirt and trash in your oil.

The next step is to go down to an auto supply store and
buy a really good rotary barrel pump and a large canister-type
diesel fuel filter. I bought mine at a NAPA auto parts store.
The pump and filter and a couple of pipe fittings cost me $75;
this is less than the cost of half a barrel of the regular smoke
oil. The filter will
have pipe threads
both on the input
and output sides of
it, and so will your
barrel pump. Simply
attach the filter to
the output side of
your pump and you
are in business. Now as you pump the oil out of the barrel it is
being filtered at the same time. Just catch the filtered oil in a
clean container. You will need to replace the filter after a few
barrels of oil go through it.