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Technical Service Bulletin - Kavlico Fluid Pressure sensors

Original Bulletin: December 4, 2014

PLEASE READ THIS BULLETIN IN ITS ENTIRETY BEFORE CONTACTING DYNON AVIONICS

Description

Some Kavlico fluid pressure sensors sold by Dynon Avionics exhibit behavior which results in incorrect fuel pressure indications during altitude changes. This may be apparent in Rotax 912 and 912 iS engines, or other applications that utilize 5 PSI, 15 PSI, and 50 PSI fluid pressure sensors. After holding altitude, fuel pressure may or may not return to the normal expected value. The maximum error due to this issue is 0.5 PSI per 1000 feet of altitude change.

Operators should be careful to not attribute other fuel system issues to this sensor issue. Fuel pressure effects induced by (but not limited to) changes to power, fuel flow, attitude, or airspeed are not caused by this sensor. This bulletin ONLY applies to you if fuel pressure is affected by changes in altitude in a way that is unexpected for the design of the fuel system.

Units Possibly Affected

Not all Kavlico sensors are affected; Dynon believes this issue to be uncommon. Potentially affected parts are:

  • Kavlico, 1/8-27 NPT, 5 PSI (Dynon P/N 101715-000, Kavlico P/N P4055-5G)
  • Kavlico, 1/8-27 NPT, 15 PSI (Dynon P/N 101690-000, Kavlico P/N P4055-15G)
  • Kavlico, 1/8-27 NPT, 50 PSI (Dynon P/N 101716-000, Kavlico P/N P4055-50G)

The red box in the image above illustrates where to find the pressure range of the sensor. 5G, 15G, and 50G represent 5, 15, and 50 PSI sensors, respectively.

Troubleshooting Information

The root cause of this issue is an environmental seal that does not allow the pressure sensor to correctly equalize its ambient pressure reading as altitude changes. Since these are gauge pressure sensors, they measure fluid pressure with respect to the ambient atmospheric pressure.

The behavior of incorrectly low fuel pressure indications due to this issue will be most noticeable during climbs and descents. If your sensor is affected, you may see lower than expected fuel pressure by up to 0.5 PSI per 1000 feet of altitude change during a climb. Similarly, you may see higher than expected fuel pressure by the same amount during descents.

Incorrect change in fuel pressure due to this issue is also proportionate to the change in altitude. If your fuel pressure sensor is affected, you will not see an immediate drop in fuel pressure as a climb is started.

If your fuel pressure indication exhibits this behavior, you can test whether your fuel pressure sensor is affected by this issue by removing the silicone gasket from the connector, reseating the plug, and then retesting the system in another flight. If the problematic behavior is significantly decreased or eliminated after removing the silicone gasket, you have an affected sensor.

The silicone gasket does not protect the ambient pressure port - it has its own water-rejecting coating. However, operating the sensor without the silicone gasket may adversely affect the long term durability of the sensor due to connector corrosion in high-moisture environments. The operator and/or installer is responsible for determining whether or not the sensor’s installation allows for continued use without the silicone gasket.

Replacement

If you have a sensor which exhibits the issue described above, Dynon Avionics will replace the sensor at no cost if the sensor was manufactured between July 1, 2013 and June 30, 2014. Dynon will only warrant sensors that were purchased for use with Dynon Avionics products. Customers should provide proof of purchase when requesting warranty replacement of an affected sensor. If you have a sensor outside of this date range and believe your sensor is affected, please contact Dynon for further assistance.

To replace an affected sensor, contact Dynon Avionics Technical Support (425-402-0433, support@dynonavionics.com) to receive a Return Material Authorization (RMA). Do not return affected units to Dynon Avionics without first obtaining an RMA.

Replacement fuel pressure sensors are shipped with a connector / pigtail, but installation of a replacement fuel pressure sensor DOES NOT require replacement of the connector / pigtail.

Sensors that are returned under warranty will still carry the remainder of their 1 year warranty, but the replacement sensors will not have additional warranty period added to them.

Determining the date of Manufacture

The date of manufacture can be determined using the stamped code indicated in the red box. The first letter indicates the month of manufacture, followed by the day and year. In the example photo, the date of manufacture is December 06, 2011.

Notice to Special Light Sport Aircraft (S-LSA) and Other Non-experimental Customers

Light Sport Aircraft may require authorization from the manufacturer to replace a fuel pressure sensor affected by this issue. Contact your LSA aircraft manufacturer or dealer for clarification. Dynon Avionics does not reimburse for labor required in replacing fuel pressure sensors affected by this issue.

Check your 912 and 912iS Fuel Pressure Ranges

It remains the aircraft operator's responsibility to ensure that all settings, including fuel pressure ranges, are set correctly for the aircraft. However, Dynon provides initial configuration as a courtesy to its customers.

Dynon has recently updated both the 912 and 912iS defaults to reflect Rotax's most up-to-date guidance, whch has changed since the introduction of these engines. This includes changes to the acceptable 912iS fuel pressure range for all 912iS engines. It also includes changes to carbureted 912 fuel pressure ranges, which depend on the serial number of the fuel pump.

Updated SkyView starting setups for both engines are available for download.

Alternatively, for customers that have customized their engine sensors and/or engine page layouts, the following files update ONLY the fuel pressure ranges:

Customers with EMS-D10, EMS-D120, and FlightDEK-D180 should ensure that their Rotax engine ranges match the latest guidance in Rotax's Operator's Guides.

Additional Questions?

Contact Dynon Avionics Technical Support via phone (425-402-0433) or email support@dynonavionics.com