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#1
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Localizer Back Course vs. ILS
Hello.
My home base airport (KOSU) has ILS 9R approach and NDB 27L approach. My question is, Can they have Localizer Back Course 27L? I am wondering if the signal is always avaialble on the reverse side of Localizer. Or should there be something extra to have Localizer back course? I tested the signal while landing on runway 27L, and it seemed that the signal was available. But there is no published instrument approach like Localizer back course 27L approach. Can you give me input on this? I think Localizer Back course would be more accurate than NDB approach. Thank you. Ilsub Jung |
#2
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Not always. AIM 1-1-9 cautions against using the back course signal unless
an approach has been authorized. At some locations, the back course is screened off in some way to make it unavailable (don't know the details). I would be reluctant to fly the back course in actual IMC just because it exists. Bob Gardner "ilsub" wrote in message om... Hello. My home base airport (KOSU) has ILS 9R approach and NDB 27L approach. My question is, Can they have Localizer Back Course 27L? I am wondering if the signal is always avaialble on the reverse side of Localizer. Or should there be something extra to have Localizer back course? I tested the signal while landing on runway 27L, and it seemed that the signal was available. But there is no published instrument approach like Localizer back course 27L approach. Can you give me input on this? I think Localizer Back course would be more accurate than NDB approach. Thank you. Ilsub Jung |
#3
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"Roy Smith" wrote in message ... A proper "flight check" involves an FAA aircraft filled with fancy electronics which checks the signal for strength, accuracy, etc, not just on the centerline, but also at the edges of the approach corridor. The "test" you did yourself just isn't good enough. The loc offset for 9R is 5 degrees, pretty close to the max allowed (5). The back course might point you off into some obstacle. You could always get a GPS there are GPS approaches to both ends of the runway :-) |
#4
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ilsub wrote: Hello. My home base airport (KOSU) has ILS 9R approach and NDB 27L approach. My question is, Can they have Localizer Back Course 27L? I am wondering if the signal is always avaialble on the reverse side of Localizer. Or should there be something extra to have Localizer back course? I tested the signal while landing on runway 27L, and it seemed that the signal was available. But there is no published instrument approach like Localizer back course 27L approach. Can you give me input on this? I think Localizer Back course would be more accurate than NDB approach. Thank you. Ilsub Jung Back courses are more often not available to flight inspection tolerances for approaches because of shielding of the antennas to make the front course perform to requirements. |
#5
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Greg Esres wrote: The loc offset for 9R is 5 degrees, pretty close to the max allowed (5). TERPS says that any localizer that's more than 3 degrees off will be identified as an LDA. Where does your 5 degrees figure come from? One pertains to course width, the other to course offset. |
#6
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One pertains to course width, the other to course offset.
No, I don't think so. A localizer can be 3-6 degrees in width, so that goesn't jibe with either my figure or Ron's. |
#7
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Greg Esres wrote: One pertains to course width, the other to course offset. No, I don't think so. A localizer can be 3-6 degrees in width, so that goesn't jibe with either my figure or Ron's. Well, here are the pertinent TERPS criteria. There is no criterion for a 5-degree offset. It goes from LOC to LDA at 3 degrees offset, and a back course cannot be offset at all, nor can a back course have a course width in excess of 6 degrees: 901. USE OF LOCALIZER ONLY. Where no usable glidepath is available, a localizer-only (front or back course) approach may be approved, provided the approach is made on a LOC from a FAF located within 10 miles of the runway threshold. Criteria in this section are also applicable to procedures based on localizer type directional aids (LDA). Back course procedures shall not be based on courses that exceed 6° in width and shall not be approved for offset LOC. {New-2002-24 902 Revised May 15, 2002} 902. ALIGNMENT. Localizers which are aligned within 3° of the runway alignment shall be identified as localizers. If the alignment exceeds 3°, they will be identified as LDA facilities. The alignment of the course for LDA facilities shall meet the final approach alignment criteria for VOR on-airport facilities. See chapter 5, paragraph 513, and figure 48. |
#8
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There is no criterion for a 5-degree offset. It goes from LOC to
LDA at 3 degrees offset, And that was the substance of my original post. I asked Ron where he got the 5 degree figure. He said 5 degrees was the maximum offset for a LOC. |
#9
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"Greg Esres" wrote in message news The loc offset for 9R is 5 degrees, pretty close to the max allowed (5). TERPS says that any localizer that's more than 3 degrees off will be identified as an LDA. Where does your 5 degrees figure come from? The number in the parens is a typo. Second, I made a mistake. When I looked up the runway heading, I didn't notice that I was reading the true runway heading. Add in the 5W variation at OSU and the runway heading is precisely aligned with the localizer course. Never mind :-) |
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