Technical Service Bulletin - Heated AOA/Pitot Probe

Date: May 6, 2014

The following bulletin is superseded by the October 10, 2014 Heated Pitot Service Bulletin. The information on this page is provided for historical reference only.


Applicability and Affected Equipment

This bulletin affects the Dynon Avionics Heated AOA/Pitot Probe (p/n 100667-000).


Dynon Avionics has received reports from pilots who have experienced degraded airspeed indications while their Dynon heated pitot probes are in operation. Dynon Avionics has identified an issue where the pitot probe is unable to adequately separate and drain water that is encountered in some flight conditions. As a result, it is possible for water to enter the pitot system and subsequently freeze in unheated areas. This can cause inaccurate, fluctuating, or zero airspeed indications.

Operating Recommendations

Aircraft equipped with a Dynon Avionics Heated AOA/Pitot probe should be operated as if the aircraft is equipped with an Unheated AOA/Pitot Probe.

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

You are solely responsible for ensuring that your aircraft is airworthy. In the case of S-LSA aircraft, owners may need special authorization to remove, replace, or update the firmware on a SkyView display(s) if such operations are not permitted in the maintenance manual. Please refer to your aircraft maintenance manual or contact your aircraft manufacturer concerning removing, replacing or updating firmware on your SkyView display(s).

Frequently Asked Questions

Question: Is Dynon working on a solution to this issue so that the heated pitot can be used?
Answer: Yes. Dynon Avionics takes this issue seriously and is devoting significant resources to resolving it. Dynon Avionics is implementing design changes to address the root cause: inadequate water separation/draining for the target environment. Dynon is also evaluating software-based solutions to improve the attitude indication in the event of pitot system issues. We are not quite ready to release specifics about any design changes; when we reach that point, we will communicate next steps. Please sign up for the Dynon Avionics Email Newsletter to ensure you receive future notifications about this issue.

Question: Once Dynon has a solution for the issue, will I have to buy a new heated pitot?
Answer: Dynon is committed to supporting our customers. If any hardware change needs to be made, the parts to resolve the issue will be provided to all existing heated pitot customers at no charge.

Question: When do you expect to have a solution available?
Answer: We are testing solutions now, but do not currently have a release timeframe available.

Question: Can I still purchase a Dynon Heated AOA/Pitot Probe?
Answer: No. As of 5/6/14, the heated pitot is on a stop-ship. We will resume sales when a design that addresses these issues is available.

Question: Are you recalling Heated AOA/Pitot Probes that are in the field?
Answer: No. Dynon Avionics is not issuing a recall at this time. Dynon Avionics recommends that pilots comply with the Operating Recommendations portion of the Heated AOA/Pitot Probe Service Bulletin until a design that addresses these issues is available

Question: Does the Dynon pitot probe get hot enough?
Answer: Yes. The 120 watt heater which heats the body of the probe, including the drain holes, is sufficient to melt external ice in the conditions experienced by piston-powered Experimental and Light Sport Aircraft. Our data indicates that the root cause of this issue is inadequate water separation inside the pitot.

Question: Is there a problem with the pitot’s heat regulation?
Answer: No. The regulated heater is a safety feature which prevents the pitot from becoming dangerously hot on the ground. The regulator controls the heat output as necessary to keep the pitot probe clear of ice in sub-freezing temperatures. Though the heater system design is more than adequate to melt ice, inadequate drainage in some conditions can allow water into unheated portions of the pitot system.

Question: Is there a problem with the drain holes’ size or location?
Answer: The issue appears to be related to draining moisture, so yes, there is likely an issue here. The drain holes are larger than required by TSO-C16a, so it is not as simple as size. Drain holes cannot be made larger without adversely affecting airspeed indication in normal operation. The location of the holes and other internal features are currently being investigated.

Question: Are the D1and D2 Pocket Panel Portable EFIS products affected?
Answer: No. As standalone backup instruments, these products use GPS ground speed as part of the attitude calculation, and are not connected to the pitot/static system.

Question: Can this issue occur if I am flying through clear air?
Answer: Yes. Pilots have reported this anomaly in clear air, but only when the outside air temperature was below freezing, and the pitot had previously encountered precipitation or otherwise ingested water.

Question: Does this affect the unheated pitot probe?
Answer: No. The unheated Dynon AOA/Pitot (p/n 100141-000) is not designed for use in flight conditions where pitot icing is expected. Therefore, this bulletin does not apply to that product.

Question: Does this affect the unheated boom mount probe?
Answer: No. The unheated Boom Mount Dynon AOA/Pitot (p/n 100532-000) is not designed for use in flight conditions where pitot icing is expected. Therefore, this bulletin does not apply to that product.

Question: Should I continue using the heating function of the the heated pitot probe?
Answer: Yes. Applying pitot heat does help mitigate pitot icing. Dynon still recommends you use the heat function of the pitot when it is appropriate for your flight conditions.

Question: What are the symptoms of various pitot system failures?
Answer: There are a variety of airspeed indications that are possible with a blockage of any kind in a pitot system:

  • Indicated Airspeed may go to zero. This may happen quickly or take minutes to occur.
  • Indicated Airspeed may fluctuate or become erratic.
  • Indicated Airspeed may become directly related to altitude. If the pitot system is completely blocked, then airspeed varies with static pressure only. In this case, as you descend, airspeed indication will decrease. If you climb, airspeed will increase. This is opposite from the normally expected reaction of airspeed which increases as a plane descends at a constant power setting.
  • If you hold altitude, your airspeed indication may stay fixed without relation to the actual aircraft airspeed. This may be perceived as high or low airspeed if you have climbed or descended since the blockage occurred.


Contact Dynon Avionics Technical Support via phone (425-402-0433) or email