Boeing plans to send the second 787, ZA002, to the north pole at the weekend. The flight will be a key test of the Honeywell-developed navigation package, as magnetic heading in the polar region is unreliable or completely useless for navigation.
The 787 will, for the first time, be penetrating deep into the Canadian area of magnetic unreliability in which magnetic variations are extreme, frequently not constant at the same point, and change rapidly as an aircraft changes position. The point of convergence of magnetic field lines in the northern hemisphere wanders over time and is not at the geographic pole. It presently lies in Canada’s Northwest Territories and is about 11.6° south of the geographic north pole, and about 104.3° west longitude.
The Honeywell system includes flight management, the air data system, and two integrated nav receivers (INRs). The INRs contain ILS (localizer and glideslope), marker beacons, VOR, GPS and GLS (GPS landing system) and provide capability for Cat IIIB ILS and Cat I GLS approaches. The package also includes inertial reference systems, part of which is made up of two micro-IRS units, as well as two AHRS (attitude heading reference system). Another component is the Earth Reference System (ERS) which combines the air data inertial reference unit and secondary attitude and air data reference unit. During the flight the crew will expect to see the magnetic variation begin as ZA002 nears the southern portion of the Canadian Northern Control Area (NCA) – roughly around a line joining Yellowknife and the southern shores of Hudson Bay.
Although Boeing does not comment on specific flight tests, it is likely the crew will perform runs to and around the north pole in various modes and simulating various system failures. In 1989 I was lucky enough to be on a polar test flight during the latter stages of the MD-11 certification program, and joined the crew on the flight deck along with the FAA and JAA officials to see how the displays would cope with the transition over the pole itself. With darkness cloaking the scene outside, all eyes were on the large screens as the moment arrived. Despite several failure modes deliberately added to the mix, the system coped admirably – the displays momentarily ‘blinked’ before a rapid heading and track reversal occurred as we passed over the polar waypoint.
It was a strange thought that one second we were hurtling north at transonic speed, and the next we were pointing straight south. Our flight had begun in London and transited to the pole via Norway before crossing the top of the world and continuing south across Canada and the U.S. to McDonnell Douglas’s test site in Yuma, Ariz. It was a memorable day, not least for allowing me to witness two sunrises and two sunsets in the space of 14 hours!
As with the 777, Boeing is likely to suggest the preferred mode over the pole is lateral navigation (LNAV) with the autopilot engaged. In the 777 LNAV may be used with the heading reference switch in the normal position. Heading select/hold and track select/hold are functional but require the manual selection of TRUE for the heading reference. Boeing says when operating the autopilot in the polar region in a roll mode other than LNAV, the TRUE position on the heading reference switch must be selected.
Interestingly, when flying close to the pole, crews have noticed navigational display (ND) track and magenta lines may exhibit ratcheting. When operating in the polar region with the ND plan mode displayed, the aircraft position symbol disappears when flying into the polar region
The extensive test flight also includes evaluation of the autoflight, flight management functions, the displays themselves, hydraulic and fuel system and auxiliary power unit.