Menu Sign In Contact FAQ
Banner
Welcome to our forums

In solid IMC suddenly I didn't know which instruments I could trust.

Seemed highly to be the case an engineer myth (though doing it on ground is probably more safer than doing it while flying: things are moving on then screen, sensors are sending signals and busy processor)

Last Edited by Ibra at 11 Jan 12:33
Paris/Essex, France/UK, United Kingdom

@eddspeter pulling the CB would have definitely solved the problem of distraction but the way the PFD/MFD had been configured I would also have lost distance to next waypoint info and bearing info which was needed.
From the RNAV approach the minima were just about met but we were informed that the wind was 200/25G45 runway 285. I took the decision not to take the risk, I knew also that now I was on track and heading in the right direction so if the PFD flashed turn right to xxx in 5 secs I could try to keep on the pre set flight plan for the return by looking at the track info on the MFD. I was however later given vectors to get me onto the ILS. This caught me out a little again as it meant the compass now became the most important instrument to maintain headings and I was back to the mental problem of remembering that it turned the opposite direction to a DI/HSI.
In making the decision I also had the misguided (as it turned out) thought that the CDI/glide slope might be accurate although as I wrote before the glide slope seemed accurate. Although the winds were a little stronger here they were from 200 and the QFU was 253, a little more manageable.

France

If you pull out the PFD CB, MFD revert to show pfd. The problem is that you may have the same problem on the second pfd as it looks like issue was in the navigation tools (ahrs,…). Keeping the MFD allows to fly a course and your route, or even a suitable alternate in a bigger screen, and you can revert to alternate horizon, speed,…
I had this on my IR exam, but we were actually VMC with ir googles.
Da42 manual says you must keep away from CB because it’s an electric plane and CBs like to strike electric stuffs. Probably EM disturbances stroke the flux vanes.
Issues comes when lightning strikes the fadecs…

Last Edited by greg_mp at 11 Jan 15:17
LFMD, France

@greg_mp there would have been little point in the MFD reverting to the PFD as it wouid just have transferred the distraction feo left side to right side.
The large map on the MFD did show active legs as the magenta line but firstly I found it difficult to join the magenta line as the aircraft symbol never pointed in the same direction as the aircraft was flying. Once on the magenta line it was difficult to stay on the magentta line for the same reason. Imagine steering and trying to hold 180 when the aircraft symbol points to 270 one minute 360 a few seconds later and then just continues spinning. Add to that an 80 something knot wind which of course changed direction to the aircraft as we moved from active leg to activenleg on different tracks.
Yes I do understand that the aircraft manual says avoid CB’s, fortunately we didn’t rund into any because they would have been embedded in the TCU’s a dangeeous situation. Although the TAFs for the flight did indicate CBs in the region they were supposed to be few, not embedded, tempo and much later in the day.
As I wrote I learnt a lot from this flight which is why the thread is under this heading.

France

Ouch… you can train for AHRS failure, but in your case it was sending garbage to the G1000, which is even worse! I can imagine it was a stressful experience..

Did you try to pull the AHRS CB? That would have probably stopped the erroneous readings..

Did you announce the instrument failure to ATC?
If it happened to me (single pilot / struggling to maintain instrument scan) I would declare a MAYDAY…

I think you did extremely, well, gallois, and thank you for posting it.

It sounds like a fluxgate magnetometer and/or AHRS failure. An AHRS is used to stabilise the (otherwise quite wobbly) heading data from a fluxgate.

The lesson might be carrying a huge post-it sticker and reverting to a handheld GPS and flying the track on that.

The reason the lateral and vertical bars continued to work is because they are driven directly from the nav source. Well, that is the case with ILS, and with a GPS source you still get the same stuff from the navigator box.

Administrator
Shoreham EGKA, United Kingdom

In such a problem I think you did well and got you asses out of this and, at the end get back to safe flight. A failure with one of more red crosses is manageable but untrustful informations as you had are misleading and can either distract you at best or lead you to wrong assumption and is of course more dangerous.
Thank a lot for sharing that, actually I will keep it mind for next g1000 flight.

LFMD, France

I’ve kept a cover (with a suction cup) ever since I bought my plane, to hide the AI if it was ever to fail. Now that I’ve replaced it with a PFD, I don’t have anything to cover it and am vulnerable to disorientation in the situation you went through. Thanks for sharing it, it’s led me to look for something.

EGTF, LFTF

Peter wrote:

The lesson might be carrying a huge post-it sticker

Last Edited by Ibra at 12 Jan 18:16
Paris/Essex, France/UK, United Kingdom

Does the DA42 have static discharge wicks? Wildly speculating, but this reminds me of a report on COPA from the owner of a G5 SR22 which would develop strange avionics faults only when in IMC. I think the owner sold the plane in the end. It seems that this is not unheard of and the solution involves verifying every bonding and measuring the current flows through the different parts of the airframe to make sure they’re all connected to each other and to the wicks.

Don’t know anything about DAxx planes though.

Sign in to add your message

Back to Top