Page 12 - Volume 11 Number 8

Beware
it increases its acidity. This could be why Black Death rears its ugly head more frequently in R134a systems. That, and the fact that there are fewer R12 systems that exist these days.
of Black Death
I was never a fan of converting R12 systems to R134a because R12 cools so much better. The R134a systems in cars and airplanes today, however, are greatly improved over the anemic systems of 20 years ago. As long as I could procure R12 – good R12 – I kept servicing those systems. R12, although pricey, continues to be available today, but you must search for a reputable supplier.
by Dean Benedict, A&P, AI
During the hot summer months, nearly everyone is running their air conditioner, and it would be an awful thing for it to stop working. Black Death could be the culprit and it isn’t what you want to happen to your King Air. Black Death is a sludgy disgusting goo that gums up the air conditioning compressor, condenser, evaporator and everything else in the system. Essentially, it destroys all the components. Everything must be replaced and the lines flushed clean – this is a miserable and expensive process.
On King Air 200s and 300s, the air conditioner (AC) compressor is on the R/H engine and the plumbing goes through the wing root, so the R/H leading edge must come off. It’s a nightmare.
The crux of the problem is moisture in the system. AC systems are sealed to keep moisture out. When it is opened to replace a switch or a component, a vacuum pump is used to remove all the air, and the moisture in it, before recharging the system with Freon. Some think Black Death only affects R134a systems, but it can bring down an R12 system too.
Freon and Moisture
Freon becomes acidic when mixed with moisture, and the acid corrodes the aluminum in the condenser, the evaporator and certain parts of the compressor. Also, in aircraft AC systems, the lines (tubing) are aluminum. Think of the black residue on your rag after polishing the aluminum wheels on your car or the aluminum spinners on your King Air. That’s the “black” in Black Death. The AC system is being eaten away from the inside out. Corroded aluminum mixes with the Freon and oil in the system and this mixture is subjected to extremes of temperature. The result is a gooey black sludge that eventually chokes the system to death, quite literally.
R12 and R134a
Dichlorodiflouromethane (R12) boils at -21.6o F; Tetrafluoroethane (R134a) boils at the warmer temperature of -15.34o F. This is why R134a doesn’t cool as well as R12. Another difference is that R134a is slightly acidic to begin with, and adding moisture to
10 • KING AIR MAGAZINE
Freon – the Good, the Bad and the Ugly
Ten years ago, I had a customer who owned a couple of King Airs with R12 systems. He chafed at the cost of R12, so he brought me his own cylinder. I knew that he flew frequently to Mexico and was worried his R12 was purchased there, so I was careful not to mix his Freon with my own. In refrigerant circles, Freon from Mexico and other countries has a reputation for impurities that muck up AC systems. I heard that Mexican R12 has butane added as a filler. Pure R12 is non-flammable.
There is nothing wrong with recycled Freon, whether it’s R12 or 134a, as long as it is good quality (clean and pure). The air conditioning machines used by knowledgeable
Air conditioning systems that require R12 Freon are decreasing and make finding good quality R12 harder to come by. A quick way to identify R12 is the color of the cylinder; they are color- coded per type and white is reserved for R12.
AUGUST 2017
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