ILS approaches in True at Hight Latitudes (B744).
Whilst flying UK-Canada northern route recently the discussion came up in the flight deck about what procedures are required to fly a coupled ILS in True?
Say to places like Thule where the ILS is promulgated in True and have very a large variation. Does anyone know on the B744 (or probably the same on other Boeing's) if the Hdg switch is left True twill he aircraft fly a coupled approach OK? |
noblues:
Does anyone know on the B744 (or probably the same on other Boeing's) if the Hdg switch is left True twill he aircraft fly a coupled approach OK? The rub comes in for the guys who go to those airports that don't have IRUs or true AHRs. |
Since the ILS is a radio beam the coupled approach will bracket it without reference to the True or Mag setting. Seems to me anyway. Long time since I flew one though.
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Thule (THU / BGTL) is N76 deg 31' 52.
B767 / 757 manuals class north of N73 deg, and south of S60 as 'Polar'. (I presume other models of Boeing similar). In Polar regions the HSI map will ONLY be showing T (True), regardless of the position of the Heading Reference Switch. And as the ILS course, 18 Nov 11 (Jepp) is shown as 085T, it will be just like any other ILS. |
The ILS is tracked according to radio beams, irrespective of selected heading. Think of a crosswind when heading would be offset, but when the track would still be aligned with the pavement. By the way: The B747 main gear is also stressed and approved for touchdown in a crab, if necessary. :ooh:
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