OBS/Azimuth Required to Match Charted Course?

HighFlyingA380

HighFlyingA380

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Jim F.
I've always operated under the impression (probably from my instrument training way back when..) that the OBS/azimuth is required to be set the the charted course. Not sure if there was supposed to be a differentiation between en-route, terminal, and approach environments, but It's always come up when on an approach...

Specifically, this has come up several times from other pilots as we set-up for a LOC BC. Several folks wanted to set it to 060, opposed to the charted 240, Again, I was always under the impression that that wasn't legal, so I didn't allow it. The other week, I flew my first LOC BC with an EHSI on the G1000, and it automatically selected 060 to cancel out the reverse sensing.

So I'm leaning towards this actually being legal... Does anyone have some insight either way as to what's the correct answer? I've searched through the FARs (91 and 135), Instrument Flying Handbook, Instrument Procedures Handbook, and Mr. Google. Thanks!
 
You set it to whatever your instrumentation requires. For a LOC BC I set in the FRONT course and then push a Back Course button on my panel which swaps the EHSI. The old style OBS ILS indicators don't know which side of the localizer you are on. Steam HSIs work the same way, but you can rotate the CDI "card", if you will, 180 degrees to make the picture look "normal". It's a localizer. What you set in the OBS will do absolutely nothing course guidance wise.

http://stoenworks.com/Tutorials/ILS Back-Course Approaches.html
 
I'm not sure I completely understand what you are asking, but if you always want correct sensing when using an HSI for a localizer, always set the inbound of the front course.
I know of nothing illegal about setting the HSI pointing to the station while en route vs your course. I used to fly with an experienced captain that did just that, so when flying away from the VOR the needle head was pointing to the rear. That will still provide correct sensing.

If you're talking about the old swinging needle VORs, that's a bit different.
 
There is absolutely no legal/illegal aspect to this. On a localizer course, the OBS setting does not affect the CDI deflection, however, with an HSI type of presentation, setting the front course direction orients the HSI so that one has correct sensing verses reverse sensing. On a localizer with an HSI, I always set the OBS so that the CDI arrow points to the front course and the tail of the pointer to the back course.
 
As John said, there's no "legal/illegal" in this discussion...it's more a matter of understanding what you're doing and why.

As you discovered via Garmin, one of the advantages of an HSI is that you don't have to fly opposite the needle if you set it up the way it's intended.

Notice I didn't use the term "reverse sensing" there...the CDI doesn't actually "reverse sense". It simply tells you, in the case of a localizer, whether you're on the shaded side or the unshaded side of the feathered arrow that depicts a localizer on your chart. The HSI simply allows you to turn the needle around so that it's oriented with the front course, so so you don't have to get into the whole "reverse sensing" discussion.

When you REALLY understand an HSI, you'll be able to tell which way to point the needle when flying the back course-outbound portion of the LINDZ departure or the VOR/DME-C missed approach at Aspen (KASE). ;)
 
Thanks for the replies. Not sure where I got that it was required to match the charted course... Either way, it just kinda caught me off guard when I loaded it into the G1000 and the course was set 'wrong.' I ended up manually setting 240 to have fun with the handflown raw-data LOC BC.
 
John Collins said:
There is absolutely no legal/illegal aspect to this. On a localizer course, the OBS setting does not affect the CDI deflection, however, with an HSI type of presentation, setting the front course direction orients the HSI so that one has correct sensing verses reverse sensing. On a localizer with an HSI, I always set the OBS so that the CDI arrow points to the front course and the tail of the pointer to the back course.
Click to expand...
I'm having a little trouble understanding what "CDI arrow points to the front course" means. Are you setting the arrow so it points in the direction you're flying, or behind you?
 
Palmpilot said:
I'm having a little trouble understanding what "CDI arrow points to the front course" means. Are you setting the arrow so it points in the direction you're flying, or behind you?
Click to expand...
it has nothing to do with the direction you're flying...it's the direction of the localizer course. The front course would the the normal ILS direction. The back course would be the back course direction.
 
HighFlyingA380 said:
I've always operated under the impression (probably from my instrument training way back when..) that the OBS/azimuth is required to be set the the charted course. Not sure if there was supposed to be a differentiation between en-route, terminal, and approach environments, but It's always come up when on an approach...

Specifically, this has come up several times from other pilots as we set-up for a LOC BC. Several folks wanted to set it to 060, opposed to the charted 240, Again, I was always under the impression that that wasn't legal, so I didn't allow it. The other week, I flew my first LOC BC with an EHSI on the G1000, and it automatically selected 060 to cancel out the reverse sensing.

So I'm leaning towards this actually being legal... Does anyone have some insight either way as to what's the correct answer? I've searched through the FARs (91 and 135), Instrument Flying Handbook, Instrument Procedures Handbook, and Mr. Google. Thanks!
Click to expand...

Legal? Where in Part 91 would you find a regulation covering this? The basic rule for interpreting the regulations is that anything not specifically prohibited is legal.

I always counsel students to challenge their instructors... "Show me where it says that in the regulations." What would you say in response to such a challenge?

Bob Gardner
 
MauleSkinner said:
it has nothing to do with the direction you're flying...it's the direction of the localizer course. The front course would the the normal ILS direction. The back course would be the back course direction.
Click to expand...

That tells me what the back course direction is on an ILS approach, but I'm not sure that it tells me what it is on a back course localizer approach.

As John is using the term, when he's on the final approach course of a back course localizer approach, is the back course direction toward the airport? In other words, is he setting the HSI needle to point inbound for both normal and back course approaches?
 
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If the front course (full ILS or just LOC doesn't matter-it's only the localizer that's used for the back course) is, say, 090 deg for Runway 9, you'd set the HSI needle to 090 deg when using that localizer...whether flying it on the front course approach to 9 or the back course approach to 27.
 
Thanks. That clarifies it.
 
bobmrg said:
Legal? Where in Part 91 would you find a regulation covering this? The basic rule for interpreting the regulations is that anything not specifically prohibited is legal.

I always counsel students to challenge their instructors... "Show me where it says that in the regulations." What would you say in response to such a challenge?

Bob Gardner
Click to expand...
I agree; Exactly why I've been looking/asking around. It's only just come up recently as that's the first time I've shot a LOC BC with an EHSI.
 
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