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Some odd Dynon behaviour


Ian

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A little advice on where to look would be very welcome please....

 

A little background - my CTLS is based at a grass field which is now very muddy (this is England in winter!) and only just flyable. I flew just over a week ago and on landing the aircraft picked up a fair amount of mud spattered over the fuselage and onto the elevator - I couldn't wash it off as the water supply at the airfield automatically cuts of if there is a danger of freezing (and there was and still is!!) - however on the flight everything seemed perfectly normal and all instruments worked fine.

 

Today - it had stopped raining and I decided to go flying (still too cold to get a hose and wash it), so pulled the aircraft out and started it up - Outside temp was 0, QNH 1025mb which I set on the Dynon D-100 giving an indicated field elevation of 174' which is about as expected. After a couple of minutes I noticed that the manifold pressure indicated on the Dynon D-120 EMS was off the scale with the numbers in red! Other indications (oil pressure, oil temp, volts, amps etc seemed OK)

 

So I switched off, took a look around, took the cowling off and checked all the wires that I could, nothing obvious - so started up again. Immediatey the MAP indication went to the top of the scale, the D-100 changed its display colours and gave a message "Attitude Recovering" - eventually apparently resetting itself - BUT - the indicated altitude was now 190' with no change having been made to the Baro setting.

 

In addition on the D-100 as I increased the power (still stationary) the Indicated Air Speed started saying 19 knots and the OAT section on the screen said:

 

OAT 6C

-1260 FT

000KTS

 

and the angle of attack indicator suddenly displayed - as I reduced power the airspeed dropped back to zero and the AOA indicator disappeared (all with the brakes on standing still!!!!)

 

I'm somewhat puzzled at what is going on here - unlikely that both instruments, D-100 and D-120 have failed but both are giving spurious readings - however airspeed, altitude and Manifold pressure all rely on the static pressure - I'm wondering if that's the clue - could operating in very muddy conditions cause such a problem?

 

I'm ashamed to say I don't understand where the static source is taken from - no static vent on the fuselage that I can see, and no way to switch to alternate air.

 

Any thoughts anyone?

 

Many thanks

Ian

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The static inlet is on the belly of the aircraft, about the size of small coin. With the conditions you mentioned, it's likely you have some mud/gunk in there.

John Stamper, in the UK, had posted some questions about the orientation of the port here a couple of years back.

Tim

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Hello Ian,

 

I hope you know this - be care do NOT blow compressed air from outside in static port.

 

EFIS reseting has probable another cause - is happened that some units develop some strange behaviors in cold climate. Check if you have the latest firmware on it v5.4.3.

 

Regards,

Alec

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Thanks Alec

 

I was puzzled by the Dynon reset as all the other symptoms I could put down to a blocked or restricted static vent (and I don't have an air-line to blow compressed air from!!) - I don't have the very latest software on, and it has been below zero here (though it was even colder last winter without any such problems) - I will clean out the static vent, then check things out before updating the firmware - don't want to do too many things at once

 

Cheers

Ian

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