KISW SDF RWY02

[jxdrl]

I was just looking up this airport in case I fly there to pick up a truck and noticed they had an SDF approach. I know it's not anything special but I have never flown one and would like to if I go there.

If I remember everything correctly (rusty IFR), the ADF required on the planview is there to be able to fly the procedure from enroute (BANKY) to terminal without vectors from ATC and also for the missed approach.

If your ADF receiver is INOP, could you then get vectors to final and use Stevens point VOR and DME at 22.9 miles to determine your FAF and then fly the approach? Or just use the OM at NEPCO? An alternate missed would be required.

Could you also just fly the 223 radial outbound from STE for 22.9 miles/intercept the approach course (backcourse), fly the procedure turn and then the approach?

 

[flyingcheesehead]

I was just looking up this airport in case I fly there to pick up a truck and noticed they had an SDF approach. I know it's not anything special but I have never flown one and would like to if I go there.

You're right, it's nothing special - It's basically like a sucky localizer.

I flew the old SDF 36 into KFLD... They have since replaced that one with a real localizer.

If I remember everything correctly (rusty IFR), the ADF required on the planview is there to be able to fly the procedure from enroute (BANKY) to terminal without vectors from ATC and also for the missed approach.

And to identify the FAF, though the OM can do that too.

If your ADF receiver is INOP, could you then get vectors to final and use Stevens point VOR and DME at 22.9 miles to determine your FAF and then fly the approach? Or just use the OM at NEPCO? An alternate missed would be required.

While you could fly it that way, I don't think that's technically legal. ADF Required means ADF Required, though you can substitute an IFR GPS for it in this case. Do you not have an IFR GPS?

Could you also just fly the 223 radial outbound from STE for 22.9 miles/intercept the approach course (backcourse), fly the procedure turn and then the approach?

Again, you could, but I don't think you'd be legal.

BTW, those R-areas are often hot on the weekends - There's an ANG base near there ("One weekend a month, two weeks a year"). The "B" one is actually a firing range - There's a bunch of trees there and they send airplanes in to shoot the **** out of them. Fun! I actually flew not far from there one night and saw the tracers. Very cool... But will also prevent you from flying that approach.

 

[roncachamp]

If I remember everything correctly (rusty IFR), the ADF required on the planview is there to be able to fly the procedure from enroute (BANKY) to terminal without vectors from ATC and also for the missed approach.

And also to identify the FAF.

If your ADF receiver is INOP, could you then get vectors to final and use Stevens point VOR and DME at 22.9 miles to determine your FAF and then fly the approach?

No. We know from the plate that it's 22.9 miles from STE to NEPCO but the FAF is not defined by DME. Use of non-collocated azimuth and DME to form a fix is limited to an angular divergence of 23° in any case, and, without doing any arithmetic, the fix displacement error in this case appears to exceed the one mile maximum for use as a FAF.

Or just use the OM at NEPCO?

Probably not. It's counterintuitive but an OM generally can't be used to establish a FAF because the fix displacement error is too great.

An alternate missed would be required.

Yes, and what could that be? Low altitude radar coverage is rather poor in this area.

Could you also just fly the 223 radial outbound from STE for 22.9 miles/intercept the approach course (backcourse), fly the procedure turn and then the approach?

Yes, you don't need ADF to fly the STE feeder route. But you'd still have the problem of identifying the FAF.

 

[roncachamp]

And to identify the FAF, though the OM can do that too.

Actually, the OM probably can't identify the FAF. It's counterintuitive because marker beacons exist only to identify position along a track formed by another navaid, but the fix displacement error of a normal marker beacon is plus or minus two miles and the maximum error for use as a FAF is usually one mile.

 

[jxdrl]

Do you not have an IFR GPS?

Not yet. But I am strapped with portables. (Good enough for practice) - An AWM mistake for XM weather and my Galaxy Tab with Naviator. Hopefully we will pick up a 480 (my preference) or something else after they start getting replaced with the new line of Garmins.

The panel could use a little work. It could be a lot worse. I believe our ADF is inop and the old Apollo GPS isn't certified for IFR. Tomorrow will be when I finally get to fly her for the first time. I'll find out then. When I fly for travel, my AWM will be on the yoke in place of the 296 or maybe stuck to the glass. Figure that out later.

BTW, those R-areas are often hot on the weekends - There's an ANG base near there ("One weekend a month, two weeks a year"). The "B" one is actually a firing range - There's a bunch of trees there and they send airplanes in to shoot the **** out of them. Fun! I actually flew not far from there one night and saw the tracers. Very cool... But will also prevent you from flying that approach.

Sounds pretty cool. I would like to see that. My high school physics teacher told me about a hill that lost a significant portion of its height from repeated blasts from their Air Force firing. I can't remember what he flew though.

And also to identify the FAF.

No. We know from the plate that it's 22.9 miles from STE to NEPCO but the FAF is not defined by DME. Use of non-collocated azimuth and DME to form a fix is limited to an angular divergence of 23° in any case, and, without doing any arithmetic, the fix displacement error in this case appears to exceed the one mile maximum for use as a FAF.

Thanks for the technical info - I did not know those specifics and since it was only in (**), I realized it wasn't an accurate DME distance.

It's counterintuitive but an OM generally can't be used to establish a FAF because the fix displacement error is too great.

Probably another reason why they keep getting decommissioned. But wasn't that their intention in the past?

Yes, and what could that be? Low altitude radar coverage is rather poor in this area.

Direct to and maybe a hold at STE? Thanks for the local knowledge. Radar coverage or lack there of could probably be inferred since they don't list a local approach authority, only Minneapolis center which I know we typically have to be up fairly high for radar across Northern Michigan.

Do you have your MVA chart available for that area?

Yes, you don't need ADF to fly the STE feeder route. But you'd still have the problem of identifying the FAF.

So the OM is essentially worthless here.

And a portable (under radar coverage, if available) could not be used for identification of FAF? Hopefully that doesn't open a can of worms.

I can always fly it for fun using a portable for identification.

 

[jxdrl]

Actually, the OM probably can't identify the FAF. It's counterintuitive because marker beacons exist only to identify position along a track formed by another navaid, but the fix displacement error of a normal marker beacon is plus or minus two miles and the maximum error for use as a FAF is usually one mile.

So it would give your position along the course to the SDF? The position would be the FAF, correct?

However, the accuracy here isn't enough to legally have the OM be designated as the FAF - hence the LOM/ADF and ADF REQUIRED?

Did I have that right?

 

[RussR]

The "OM can't be used as a FAF" statement is completely incorrect. OMs are used to identify the FAF routinely, and that's the whole purpose of having OMs in the first place.

Fix displacement for a "low-powered fan marker", which is the type installed for approach procedure use, is +/- 0.5 nm (TERPS 286c), and therefore within the 1nm "normal limit" for FAF use.

The +/- 2nm "normal powered fan markers" were those used to identify fixes on airways, which is not done anymore, though TERPS still refers to them.

But even then, a fix displacement value of greater than 1 nm but less than or equal to 2 nm IS indeed allowed, providing the beginning of the 40:1 OCS on the missed approach is delayed by the amount greater than 1 nm, to provide additional buffer for the missed (TERPS 287c).

 

[John Collins]

The ADF is required to follow the missed approach procedure and the feeder route from BANKY. It isn't required for the feeder route from STE, or the hold, or the FAF. Regardless, without a working ADF receiver or a GPS substitution, you would not meet the 91.205 (d)(2) requirements for this approach.