No longer at the coal face but I remember that in the early 80’s we had a Delco Carousel INS strapped down in the back of the Chinook to aid our long range navigation options (pre GPS!). It was very accurate for the first couple of hours (measured against Decca/Omega/Doppler) but several hours later (long range tanks fitted), low level over the water at night, we almost learned to our cost that a single INS is not that accurate. We learned about Schuler Loop that night!
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