Tire pressure matters. Whether it’s making takeoff roll performance numbers, hauling it to a stop after landing or just getting maximum life out of a set of tires, proper inflation plays a big role.
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For owners who want an easy way to check tire pressure before getting in the airplane, Southern Precision Components’ Tire Pressure Monitor System (TPMS) may be it. Small pressure sensors attached to each tire’s valve stem measure and transmit tire pressure and temperature to a monitoring unit that receives the data when it is within 25-50 feet.
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The monitor can be programmed to read pressure in units of PSI, KPA, bar or kg/cm squared and temperature in Fahrenheit or Celsius.
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Installation proved to be easy. The kit contained everything needed, even a hex wrench for the nuts on the anti-rotation collars. AAA batteries are placed in the monitor and flat batteries in the sensors—expected life is two years.
Each valve stem cover is removed, then the anti-rotation collar—optional, it snugs up against the sensor to keep it from vibrating off—is slid on, and the sensor (each is coded for the appropriate gear leg) is screwed on tightly enough so that the tire pressure reads on the monitor. Once installed, a visual check is made to assure that there is sufficient clearance for the tire to rotate without the sensor hitting anything.
Robust Sensors
The sensors proved to be robust. They are designed to be “impervious to dust, dirt, salt mist, acids and alkalis.” The manufacturer recommends that each sensor be cleaned with water and a cleaner such as Simple Green at each annual inspection. To add air to a tire, its sensor needs to be removed. That means having the hex wrench handy if the anti-rotation collars are installed.
The system goes into sleep mode when the tires have not been rotating for 10 minutes. To activate the system during preflight, the airplane needs to be moved about a foot.
We made a number of takeoffs and landings with the sensors installed—afterward there was no indication that the sensors had started to vibrate loose, anti-rotation collar or not, even though we purposely allowed the airplane to stay on the ground to well above normal liftoff speed on a couple of takeoffs. We did not record the Richter-scale number of our landings.
We were interested to note that our testing clearly revealed that tires that “looked right” were generally inflated 10-20 PSI below the level called for in the POH or Owner’s Manual. Because all takeoff and landing performance is based on inflation to POH standards, that got our attention.
For anyone who operates in an environment where tire performance matters, the TPMS, in our opinion, provides a simple way to quickly know when tire pressure isn’t where it should be.
The TPMS can be purchased directly from Southern Precision Components, where the price quoted to us was $339.95, or through Aircraft Spruce and Specialty, where it lists for $344.00.
