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Another Heated Pitot Wiring Question
- Thread starter azflyer21
- Start date
I put all the wires for the pitot tube in wing just in case (with enough wire to reach cabin). (14 Ga) IIRC, one power wire supplies controller which in turn supplies the pitot tube itself.
In talking with Steinair folks during my panel build it turns out the harness has a power supply for pitot in one of the molex connectors but not a ground - so I'll run my ground wire to the grounding block but use the molex supply for my hot.
Since you have Dynon may be different (I'm using Garmin) but I'm sure if you give the guys at Steinair a call (Josh is the RV14 guru) they will give you the information you need.
In talking with Steinair folks during my panel build it turns out the harness has a power supply for pitot in one of the molex connectors but not a ground - so I'll run my ground wire to the grounding block but use the molex supply for my hot.
Since you have Dynon may be different (I'm using Garmin) but I'm sure if you give the guys at Steinair a call (Josh is the RV14 guru) they will give you the information you need.
Can you not just ground the black to the wing? Do you have to go All the way to your grounding block?
You never "have to" take a ground all the way to the grounding block. The reason for taking grounds to the grounding block is to avoid ground loops which can cause noise in audio circuits. Bringing as many grounds as possible to a single point (establishing a uniform ground potential) avoids this risk. Grounds that carry more current through structure back to the reference ground (negative battery terminal attachment point to airframe) have the potential to produce more noise, since more current has more energy to induce noise.
Everyone should really read the whole Aeroelectric books and site.
The forum is good for specific questions. Last I looked bob was still active.
No problem grounding the pitot heat locally.
I clicked on this for a heated discussion 
The Van's fuselage harness (built and sold by SteinAir) has a 14AWG pitot heat wire to the wing root. The Van's wing harness does not include pitot heat. I added 14AWG twisted pair and ran the ground to the wing root grounding point on the fuselage. I used the 22AWG wire in the wing and fuselage harness originally for the stall warning switch for the pitot heat controller status (assuming the Dynon controller has status wire like the Garmin).
Plans built 14 (mine) has the pitot tube heat running right by the magnetometer (what could go wrong) so decided to use 14 awg. shielded twisted pair back to the tree of grounds on the firewall after reading about multiple failed magnetometer interference testing on the 14. Tried moving the cable as far aways from the magnetometer as possible. Still no joy. The good news is zero noise in my headset but still fails the magnetometer interference test. I have 2 AHRS and G5 and do not get a mis-compare but still not satisfied.
The shield is useless at magnetic shielding, but the twisted pair should help. Make certain there’s no way for the return current to get back (like thru the wing skin) except the return wire.
I’d just relocate the magnetometer to the opposite wingtip. A bit of a pain in the butt but probably only a few hours work at worst.
Sure, locate magnetometer opposite wing. Get Richard to help. Only need to re-route 6 or 7 wires down the opposite side of the fuselage of a (in my case) flying Rv-14 and then down the wing. Just a few hours work. Then re-pin the avionics harnesses. Easy pisé. I am kidding, this is at least 2 weeks work, flying RV.
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Ha! Try that in a -10. That side panel is a bear to remove and reinstall (especially if you want the paint to survive), and there is no other easy way to run the wiring.
Been there did that, test with pitot heat on, fails. Test with wing strobe on, fails. If you don't do the interference test no problem. Running pitot heat wiring near a magnetometer never a good idea, or at least a marginal idea,
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Have done! More than once. I rerouted many wires chasing a ghost AHRS problem in phase 1.
Sure it’s not “easy” but heck if you can spend a few years and who knows how many hours building it, this is trivial.
Let me know how many hours you all waste trying other suggestions before you end up putting it on the other side.
It is more like major surgery if done after the fact.
I agree that if you aren’t putting it in the tailcone, the wing opposite the pitot would be the next place I’d choose.
I put mine in the tailcone, no issues.
BigBadBob
Active Member
Where in the tailcone, or is this already a well-known mod with 16 threads?
One bulkhead aft of the baggage compartment bulkhead, located near top using the available mount. I also added a piece of 3/4” aluminum angle between the mount and top skin stringer to make the mount rigid.Where in the tailcone, or is this already a well-known mod with 16 threads?
In the article, Mr. Bob Nuckolls wrote:
“...Ideally, one would like to use none of the airplane's structure as part of the electrical system [emphasis mine]. . . especially the engine mount.
Having said that, a time proven compromise that does not materially affect noise issues is to use the airframe as ground for the following items:
- Battery
- Strobe supply
- Landing, nav and taxi lights
- Pitot heat
- Hydraulic pumps for gear
While some of these are strong antagonists or sympathetic antagonists (due to their high current draw), remote grounding to airframe does not represent a threat to potential victims as long as victim grounding remains true to the single point ground philosophy: Sensitive accessories get a SINGLE quality ground not shared with any potential antagonists."
The revised illustration of single-point grounding for a tractor aircraft: http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z15L1.pdf
Reviving an old thread. Ran an extension down the J channel to the wingtip and now passes the magnetometer interference test perfectly. Should have done this years ago. RV-14A with GMU-22, Garmin. Strobe, heated pitot, landing lights, taxi lights all made the magnetometer interference test fail. Took all of 2 hours and no swearing !
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glider_rider
Well Known Member
I went to great lengths to limit the effects of the Dynon heated probe on the Dynon AHRS. Used every trick in the book.
The end result is that whenever I (or the controller) turn the heat on the compass moves a few degrees
If I would be building again, I would place the AHRS in the fuselage, just like in the 10
The end result is that whenever I (or the controller) turn the heat on the compass moves a few degrees
If I would be building again, I would place the AHRS in the fuselage, just like in the 10
rexbrewer
Active Member
I grounded my DYNON heated pitot controller and pitot tube to the wing. Works!
