IMC and Rotax engines

Rotax Wizard wrote:

Jason Knight wrote:

I don’t think it’s rare to have a heated pitot now days. My RANS S21 with Rotax 916 is IFR into IMC legally equipped and capable. Generally I would not fly a plane without icing protection in extended hard IMC, but have used an IFR clearance to poke through a cloud layer many times.  Nothing in the regs say the plane has to be certified, just meet the requirements and inspections. I have a lot of redundancy in avionics and backup batteries. If I planned to fly more into IMC I’d install an external alternator for further redundancy (especially considering the recent stator issues). 

Jason please check the specs on what it takes to have a heated pitot.  Most have 2 power settings, low power is 10 amp and high is 20 amp.  Without adding electrical generation supply it seriously puts your generator into max.  Drawing more than 80% of your power generation to run a heated tube could lead to some serious problems down the line.  As an experimental for sure you can fly iFR with the correct equipment but over taxing the electrical generator will defeat all of your redundant systems.  

If you have found a heated pitot that draws less than 10 amps then I would welcome some information on that. 

Cheers

The Garmin GAP 26 heated and regulated pitot tube draws only as much as needed to maintain operating temperature. The max it can draw, at initial turn-on when temp is -40C, is 12 amps. Once up to operating temp the draw is much lower, around 4 amps. 

See the attached image from the Garmin G3X installation manual (Rev AW), page 2-17.  The high current draws shown are for initial turn-on only, and are directly related to probe temperature.  The current demand reduces as the probe heats up, whether they're actively regulated or passive.

The Dynon heated probe manual doesn't specify current draw, except to mention 100W at the end of the manual, but does call for fusing the circuit at 10A, both of which suggest that maximum current demand is significantly less than that.

Thank you for looking that up Eric.  This suggests that a load calculation should be done on an aircraft to stay under the demand of the consumers.  I am worried when people load the system up to its max. 

Cheers