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Your King Air Cabin Should Be Up To 26° Cooler Than Outside Air Temps – Is Yours?


Your King Air Cabin Should Be Up To 26° Cooler Than Outside Air Temps – Is Yours?
Written by EFA 

How regular maintenance will keep your a/c running through the hot summer months

Summer is here and in addition to the typical seasonal maintenance checks, it’s time to make sure your aircraft’s air conditioning (a/c) system is ready for the long hot days ahead.  It is important for all aircraft owners and operators to properly maintain and check their systems after a long winter, but King Air operators tend to have a unique set of issues they may need to address.

There are still many King Air’s operating using R12 Freon and as of 2004, R12 Freon used in the original King Air cooling systems went out of production in the United States and other countries around the world.  An R134a retrofit for the system was developed which converts the old system to the new, approved and in production coolant. While in our experience the old style coolant resulted in slightly better cooling capacity it is becoming increasingly difficult to maintain those systems. If your King Air has an R12 system in it and you suffer a compressor loss or have other significant a/c system issue arise, you will be dollars and cents ahead to spend the money at that time to convert to an R134a system.

The cooling systems, with or without the retrofit, consist of the receiver dryer, compressor, evaporator, condenser, expansion valves, and evaporator blowers. The system has extensive ducting for air travel and a large amount of plumbing from front to back, which means it can take a significant amount of time for the air to cool the aircraft during the hot summer months, especially after it has been sitting in heat.

There are some universal issues that all King Air operators face when trying to keep their aircraft cool.

  • Maintenance- The a/c system is something a lot of operators don’t like or don’t think to spend money on until it is broken but this is one of those cases where an ounce of prevention is worth a pound of cure. A couple of hours spent in the spring to check Freon levels and specifically look at some of the a/c components for condition can save a lot of money and aggravation in the long run. We frequently see systems that are over-serviced or under-serviced and when caught early can prevent a failure from happening due to poor maintenance.
  • Leaks – The extensive duct work and numerous valves used in the system provide a high potential for leaks. There is insulation around the ducting and plumbing that helps prevent temperature loss between the evaporators and the outlets which can be removed, disturbed or damaged during other maintenance procedures as well as by decay due to aging. Poor ducting maintenance is akin to running the air conditioner in your car with the windows open.  It’s not that the system isn’t working,  you are just feeling a partial benefit of it.
  • Compressor Failure – The compressor motors are a costly failure point. In addition, when the compressors fail it often causes metal contamination to the rest of the system.  If not properly flushed and cleaned it will cause a secondary failure in a short amount of time and lasting effects of “mysterious” and often recurring failures for a long time to come.

Blower Motor Failures – Whether you are running your system on vent or on a/c this motor is running so it gets a lot of wear. It is a sturdy motor, however it runs so often that it fails with some regularity. During scheduled maintenance procedures the brushes and condition should be checked anyhow, but in our experience we have seen this is one of the items that often gets put off until a failure happens when it is largely preventable with proper maintenance.

All of the differing factors of the a/c systems combined with these common issues are the reasons that King Air operators must be vigilant in understanding their specific system and keeping it up to date and ready for use.

So what is a King Air owner to do?

According to EFA, regular maintenance is key:

Check Your Freon Levels – It is important to check the Freon level of the system at the beginning of every season to ensure the proper pressures are being applied to each component of the system.  The wrong high or low pressure will affect component life and overall performance.

  • Change Your Filters – The evaporator has a filter that needs to be changed frequently and checked for blockage.  A dirty evaporator can cause system freeze-up and lead to poor performance.  Evaporator filters are easily changed during routine inspections and are very inexpensive.  The return air filters in the cockpit are also very easy to replace during routine inspections.
  • Keep Your Drains Clean – It is very common to find standing water in the belly of a King Air under the rear evaporator.  It is important to keep the drains in the aircraft clean and working to ensure that corrosion is kept to a minimum under the evaporator.
  • Flush Your System – After an a/c component failure, it is very important to flush the system thoroughly.  Foreign object damage (FOD) or metal shavings can collect in the receiver dryer, condenser, expansion valves, and evaporators, causing blockage and damage to new parts being installed.
  • Replace Valves – It is a good rule of thumb to always replace the receiver, dryer and expansion valves, any time the system is opened up for maintenance.  These components are the least expensive and are very critical to maintain a reliable system.  The expansion valves work from a thermocouple and must be installed correctly and wrapped to ensure proper operation.
  • Secure Your Ducting & Insulation: All ducting must be secure and in good condition to provide the maximum amount of airflow into the cabin, and duct insulation needs to be repaired or replaced as needed.  The insulation helps to prevent temperature loss between the evaporator and the vent outlets, meaning more cold air in the cabin.

With some diligence (both on the part of the operator and of the maintenance facility) early on we can prevent major headaches and financial costs down the road. Operators should plan on doing an a/c checkup every spring to prepare for the summer heat. When planning a checkup make sure to select a maintenance facility that understands your aircraft system and its particular nuances. When properly maintained your King Air a/c system should provide you with reliable cooling all summer long.


About EFA

Specializing in King Airs EFA (English Field Aviation) provides professional aircraft maintenance, avionics upgrades and inspections and refurbishment services. From small inspections to complete renovation packages, EFA has the comprehensive capabilities to meet client requests and deliver concierge quality customer service. Contact EFA today to learn about how their King Air maintenance can keep your a/c system working this summer. From R134a retrofits, installations and duct insulation services, EFA can keep you cool this summer.  Visit www.efa.aero to learn more.