Originally Posted by
esscee
Got to be an error or mistake. Maybe it should be 1 nm/12hrs drift or 1.2nm/hr but 12 nm/hr is outside most if not all IRU unit limits!
Remember being taught the 3 + 3t years ago too.
The 12 nm/hr (LCR100) is for an AHRS, not for an IRS.
The LCR110 is an IRS with the stats quoted below.
But it's not meant for long range inertial navigation, so the limits you are talking about don't apply.
It is just to ensure RNP capability by providing short term IRS for RNP approaches in case you lose GPS.
PERFORMANCE (95 %)
• Pitch / Roll 0.1deg
• True Heading 1.0 deg Typical 0.5deg
• Inertial Position 2 nm/15 min
• Hybrid Position GNSS accuracy
• Hybrid Coasting after loss of GNSS 0.1 nm/10 min, 0.3 nm/17 min, 0.5 nm/20 min, 1.0 nm/28 min
• Hybrid Velocity 0.5kts
• AAIM supports RNP 0.1 capability
https://northropgrumman.litef.com/fi...tt_LCR-110.pdf
Based on the navigation grade sensors and AAIM
the LCR-110 enables continuation of even critical
RNP approaches after loss of GNSS data, helping
the operator to reduce fuel consumption and save
time. The AAIM also ensures required integrity of
satellite based navigation at low level flight
operations in mountainous areas important for
helicopter SAR operations.