IFR NAV (DME/HSI) Failure in Flight

UNDPilot91

UNDPilot91

Member
Hello, question.. Is there a chance your DME reciever would fail inflight without the VOR failing (aka getting a flag). if so... what would the indication be other than a blank DME.

Also.. I've seen a few scenerios, but no definite answer on what happens when an HSI fails during flight. You can get 1) double flag indication or 2) tumbling of the HSI or 3) HSI stuck on a radial and requires manual slave.

anything to add to those?

thanks!,
(... AvitGuy studying for his instrument written)
 
UNDPilot91 said:
Hello, question.. Is there a chance your DME reciever would fail inflight without the VOR failing (aka getting a flag). if so... what would the indication be other than a blank DME.

Also.. I've seen a few scenerios, but no definite answer on what happens when an HSI fails during flight. You can get 1) double flag indication or 2) tumbling of the HSI or 3) HSI stuck on a radial and requires manual slave.

anything to add to those?

thanks!,
(... AvitGuy studying for his instrument written)
Click to expand...

You asking about the receiver itself, as in what's installed in your aircraft? Or the overall system. If you're asking about the instrument itself, any electronic piece of equipment can fail. Mainly a blank indication (if digital), or the numbers get a barberpole across them (if analog). If you're asking about the DME system, if the TACAN feature of the VORTAC fails for whatever reason, you as a civilian will lose DME. Military using TACAN will lose all navigation for that station.

As for HSI failure, it can be the above, though with #3, its usually the slave feature failing for whatever reason.
 
UNDPilot91 said:
Hello, question.. Is there a chance your DME reciever would fail inflight without the VOR failing (aka getting a flag). if so... what would the indication be other than a blank DME.
Click to expand...
Sure. On the airplane I fly, you see "DIST ----" when the DME fails.

Also.. I've seen a few scenerios, but no definite answer on what happens when an HSI fails during flight. You can get 1) double flag indication or 2) tumbling of the HSI or 3) HSI stuck on a radial and requires manual slave.
Click to expand...
All highly dependent on your equipment.


Depending on your equipment, scenario (1) might present itself as a NAV flag plus a COMPASS, HDG, or whatever else the HSI has (HDG FAIL). (2) is highly dependent on your equipment - it could be a mechanical failure of the instrument, or it could be that the heading reference itself is tumbling. (3) is possibly slaved compass failure - push the DG button and slew it around - but with the terminology you used, ("stuck on a radial") slewing the compass won't do you any good - your OBS is broken.
 
Yes. The DME is a separate antenna, separate antenna coax, separate coax connector, separate receiver components. Lots of opportunity for it to fail without the VOR failing.

In fact, I just got my airplane back from the avionics shop where they were troubleshooting a VOR indicator issue. They fixed that (sort of) and now my DME quit working... I'm 99% sure they knocked something loose.
 
Yah the only thing the DME actually has in common with the VOR is about 3 wires that tell the DME which channel your VOR is tuned to.
 
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