Enigma - Airspeed indication on ground

[leewwalton]

My Enigma recently started giving me a hard time. Two flights ago the ASI indicated properly until I noticed feeling a 'bit slow' on final. I realized the ASI has frozen at 126 mph (my actual was 93 mph verified by my steam backup). Once in the hangar I contacted support and they advised me to reset the ASI/VSI sensors. After doing that on the next flight everything seemed fine again until on approach when I saw the magic 126 mph on the Enigma and cross checked again with the backup). Once on the runway the Enigma read 96 then slowing to 62 mph sitting static. Has anyone seen this behavior before? I suspect the Enigma itself is getting tired but was hoping to throw a hail mary here. Thanks in advance.

[jheatheraus]

Hi Leewwalton, I am curious what the resolution has been to the ASI readout problem you experienced. I have similar on an Explorer iEFIS Lite, the readout eventually stuck at 44kts (since been relying on my analog ASI). As mentioned, I reset the EFIS ASI to zero, where it remains stuck. Tried gentle Pitot port pressure, still zero. Before removing my EFIS and despatching it for repair, what happened in your case, I wonder? Thanks John

[rainier]

the Enigma is quite a bit different so I don't think you can use that as a yard stick.

If the reset ASI to zero makes no difference the ASI sensor has most likely been lifted off its pads on the rear PCB. This can happen if a bit of force is used to press on the hose fittings. Newer devices have added strengthening here.
The ASI sensor is soldered onto 8 pads on the PCB, only three have electrical connections. The bottom of the sensor has a small hole and the PCB has a cutout underneath - this has a rubber 0-ring as seal and then there is another PCB fitted that contains another sensor - your altimeter. The bottom nipple of the ASI sensor is connected to the altimeter sensor via the hole (so that is the static pressure).

If you remove the rear panel you should be able to see immediately if the sensor has lifted. if yes it is simple to solder it back. It may be possible that the solder joint(s) were strong enough causing the entire pad(s) to separate from the PCB. In this case use a small amount of contact adhesive to glue the pads back (a very small amount - use a tooth pick). Then remove a little bit of solder resist (the green stuff) off the three tracks (if all three are broken) that connect to the sensor and solder small wires to repair the connection or usually you can just bridge the gap where the track broke with solder.

Once done, do the ASI zero again and you should be back in business.

[jheatheraus]

Thank you for your prompt reply Rainier. I’ll give feedback on my issue, anticipated a week from now. Regards John.

[jheatheraus]

Hi Rainier, re-soldered the connectors (sprung loose by the factory fitted cable tie), installed latest software, zeroised ASI sensor, and success, have fully functioning unit again. Thanks again, John

[Matt]

I need some help with my Enigma airspeed indication. My airspeed was working beautifully until I decided to do some regular maintenance on the pitot static system. I disconnected the lines from the Enigma and blew the lines out. When I reconnected the lines to the unit and turned it on, my airspeed indicator showed an airspeed of 45 kts. I was in a closed hanger on a calm day so I zero'ed the ASI,VSI, AOA sensors. The next I flew, my indicated airspeed read 13 kts slow at cruise and approach airspeed. When I landed, the IAS remained at 62 kts. My stall speed is 35 kts. The IAS was consistently 13 kts slow at any airspeed until 62 kts where it froze. I zero'ed the Enigma once again but continue to see an airspeed 13 kts slow. After I saw this thread I removed and disassembled the case of the Enigma. My unit has ports for the pitot/static lines as well as AOA ports. They do not look like the ports in this thread. The ports appeared securely connected to the circuit board. My pitot/static lines are secure and not leaking. Any suggestions would be appreciated. Thanks, Matt.

[rainier]

That's a tricky one - something must have changed when you did your maintenance on your air lines.
Are you sure you do not have a pitot tube leak ? Pressurize it and see if the pressure holds. You can go up to 0.5 bars/8 psi quite safely with these sensors.
I hope it's not a sensor that went bad - these sensors are no longer available and basically impossible to find.

[Matt]

Hello Rainier, I felt I had to update my issue and let others know your product was not the cause of my problem. I checked my pitot/static system and found it was holding pressure as it should. I assumed the sensors of the Enigma went bad and bought your Vega ASI-4 to take the place of the Enigma airspeed display. Once installed, I flew the airplane and found the new ASI was accurately displaying my airspeed. However, when I landed the new ASI displayed a speed on the ground. I zeroed the unit and when I flew next the Vega ASI acted exactly like the Enigma. The indicated airspeed was slower than actual airspeed. Knowing that both instruments were not bad, I replaced my entire pitot/static system. Now both instruments work beautifully. I wish I had replaced the pitot/static system earlier, but on the bright side I now have a supplementary ASI. I like the Vega unit.

[rainier]

Thanks - always great when a problem gets sorted - there must have been some kind of blockage in your static line I guess. Kinked hose by any chance ? I know those can drive you mad as they tend to be somewhat intermittent..