Originally Posted by
EasternATC
Pardon the thread drift, but you're not serious about this are you? I think you made it up.
Fly international much? A 90 degree off course turn is quite common as an authorized contingency. Below is an excerpt from the info panel for the NOPAC charts. I'll bet that you'd see similar information coming up L637.
6. INFLIGHT CONTINGENCIES.
a General. Not all contingencies can be covered in this Advisory Circular (AC), but the following procedures provide for cases such as inability to maintain FL due to weather, aircraft performance, and pressurization failure. They are useful when rapid descent, turn back, or both are required. The pilot's judgment determines the sequence of actions taken.
b. Basic Procedures. If an aircraft experiences navigational difficulties, it is essential that the pilot inform ATC as soon as possible so that the appropriate action can be taken to prevent conflict with other aircraft. If an aircraft is unable to continue flight according to ATC clearance, a revised clearance shall be obtained whenever possible before any action is taken. If prior clearance cannot be obtained, ATC clearance shall be obtained at the earliest possible time. In the interim, the aircraft shall broadcast its position and intentions, including the ATS route designator, on 121.5 MHz at suitable intervals until ATC clearance is received. In such circumstances, communication may also be accomplished on VHF with certain stations, such as ADAK approach on 134.1 MHz; Shemya Tower on 126.2 MHz; Anchorage Center on 118.5 MHz (Cold Bay); on 124.4 MHz at Dutch Harbor; on 127.8 MHz at St. Paul Island; and on 128.2 MHz at Shemya.
If unable to comply with these procedures, the aircraft should leave its assigned route by turning 90 degrees to the right or left whenever possible. The direction of the turn should be determined by the position of the aircraft relative to the route system. Aircraft operating on ATS Route R 220 under these circumstances should, if possible, avoid turning northward to leave the route because of the route's proximity to the boundary between Anchorage/Tokyo and the USSR (Russia) FIR. An aircraft that is able to maintain its assigned level should climb or descend 500 feet while acquiring and maintaining, in either direction, a track laterally separated from its assigned route by 20 NM. For subsequent level flight, a level should be selected that differs by 500 feet from those normally used.