Page 16 - August 2015 Volume 9, Number 8

12 feet of aircraft cabin – way more cubic feet than the automobiles for which they were designed. The A/C on all King Airs has its roots in automotive systems.
One of my favorite stories concerns an A100 owner out of Utah. He was in Las Vegas on business on a really hot day in June, and had no A/C. He heard about me and hopped over to my location. Right away I determined the system was out of Freon. I serviced it and got out my sniffer. Sure enough, I found a substantial leak at the compressor drive seal. While the owner fretted over an expensive part from Beech and time involved to ship it, I had other ideas.
I knew from experience that a Ford F-150 had the same compressor. Remember the two-cylinder on the early 90s and 100s? In the days of yore at Beech West in Van Nuys, I used to rebuild those compressors with a kit from the auto parts store. So I got on the phone and found the seal I needed at a freightliner dealer across town. My wife zoomed over and got the part, I installed it, and he was good to go. I think I charged him $30 for the seal. He was flabbergasted that I knew what to do and ecstatic that I saved him so much money. We became friends on the spot. When he bought a second King Air, he brought them both to me for as long as he owned them. To this day, we get a good chuckle over that one.
Engine-Driven System Decreases Cooling Capacity
Although happy with the engine-driven system taking the burden off the generators, Beech wasn’t a fan of the horsepower coming off that R/H engine. So, they took the same five-cylinder compressor they were using in the newer 90s and plugged it into the engine-driven A/C systems of the larger King Airs. Fortunately, it took less horsepower off the R/H engine. Unfortunately, it pumped less Freon. The cylinders on the new compressor were much smaller than those on the original six-cylinder unit. So fewer cylinders and smaller cylinders meant less Freon moving around. This made the expansion valves less effective in dropping the air temperature because there’s less volume moving through the system. The result? Less cooling capacity than before.
To review: King Airs with engine-driven A/C have no air conditioning on the ground unless the R/H engine is running. And when the engine is running and the A/C is turned on, it doesn’t cool the cabin very well because of the reduced capacity of the smaller compressor. Plus, the engine is not running at max power on the ground. It’s just like running the A/C in your car while at idle – it blows much more cold once you get on the freeway. In a King Air with engine-driven A/C, it doesn’t really kick in to cold until you are airborne.
The final blow was the switch from R-12 to R-134a refrigerant. That didn’t do King Air air conditioning any favors. Even the motor-driven system is less effective.
14 • KING AIR MAGAZINE
The Air is Barely There – A/C in the 350
Anemic A/C is a common complaint with 350 owners. Beech’s 350 added two feet to the cabin of the 200/300 series. I’m guessing this added roughly 30-36 additional cubic feet to be cooled, but they kept the exact same A/C system. The 350 made its debut after Beech switched its engine-driven system to the much smaller five-cylinder compressor, so it’s no big surprise that the A/C in a 350 is a big disappointment.
There is a very expensive factory option for 350s (also available as a very expensive STC) which provides for an electric motor-driven A/C system. It ties in with the existing system to service the whole cabin. It can be used with a GPU to pre-cool a heat-soaked cabin on the ground before boarding passengers. It’s not common and it’s not cheap, but for a 350 it’s very cool ... literally.
Maintenance Tip – Find a Good A/C Guy
When your A/C goes out and it’s beastly hot, your desperation level goes up and you may be tempted to go with what you can conveniently get. Frankly, you are better off putting a wet towel around your neck, gritting your teeth and flying home or somewhere that has a proven record with King Air A/C, than to try your luck with a shop you are not sure about. I’m not one to toot my own horn, and I’m not one to bash other shops, but I have seen many attempts to fix air conditioning go horribly awry in the hands of people who don’t know what they are doing. Guesswork doesn’t cut it.
To work on air conditioning, I must be licensed to buy Freon; I need the special gauges, fittings valves and oils that every air conditioning technician must have, and I need them for R-12 as well as R-134a; I need a sniffer for leak detection; I also need expensive machines to evacuate Freon from a system and save it until the system is ready to be serviced. Even though Freon is heavier than air, I mustn’t allow any of it to escape, for fear that it fly 12-19 miles above the earth to assault the ozone layer (but that is a topic for another time and place). Here’s my point: Whoever works on your A/C needs all the equipment needed. They also require a full subscription to the manuals for all King Air models (which aren’t cheap) and an understanding of King Air air conditioning systems, quirks and all.
True story: A King Air 300 that comes to our shop regularly for phase inspections is based in another state. The pilot/manager relies on local sources if there’s a squawk between inspections. He had what he thought was a simple A/C problem and an important flight coming up. He turned to a local shop which assured him they could fix it in a jiffy, but it turned into a nightmare. The pilot called me over and over, apologizing like crazy in his frantic attempt to troubleshoot the problem for the shop and get his King Air back in service. They didn’t even know the proper amount of refrigerant required by that system, the pilot had me look it up for them!
AUGUST 2015