737 IRS alignment

[A350]

Can anyone provide some information as to why we use the GPS L for initial alignment in the 737? Why not the GPS R?

A350

[FlyingStone]

Boeing’s guidance is to use the most accurate source of position information for IRS alignment.

If your airline prefers GPS L, it is likely because MMR 1 is powered by the AC standby bus, and will likely get a valid GPS fix before MMR 2 (GPS R).

[A350]

Unfortunately our manuals are very light on information on MMR, two lines just.

Thanks for the info.

A350

[737pilotguy]

Originally Posted by FlyingStone

Boeing’s guidance is to use the most accurate source of position information for IRS alignment.

If your airline prefers GPS L, it is likely because MMR 1 is powered by the AC standby bus, and will likely get a valid GPS fix before MMR 2 (GPS R).

Correct 👍 No other reason, they're identical in every way except for their power source.