ILS approaches in True at Hight Latitudes (B744).
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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?
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?
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noblues:
I can't speak specifically to any Boeing aircraft in this respect, but the concept is to use true heading source when using true ILS or VOR IAPs.
The rub comes in for the guys who go to those airports that don't have IRUs or true AHRs.
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.
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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.
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.
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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. 
