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inertial navigation system LTN 72


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hello guys i need to now in wich condition of aligment i could start the engines or move the plane. i saw on the books that starting the engines causes a more slowly aligment of the ltn 72 and i must not move the plane until the system is completed alligned, but some people said to me that i can start the engines or move the plane on certains conditions of aligment.


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Hmmm...if you want to spend the money, you can probably buy a operator's guide


Its been quite a while, but as I recall the 72 was just an improved 51 with a couple more features. We had both kinds in addition to several with LTN-92. Generally, you should have as still or motionless a platform as possible for an accurate alignment. Just because you could get an alignment while starting engines would not necessarily mean that you should. I can't imagine moving the machine during ins alignment being a smart thing to do.

What does your flight manual say about it?

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“It is recommended that the system is aligned and the switch is placed in the NAV mode PRIOR to engine start....â€

With that said, you can start engines and stay in LSGI until you get a RDY NAV status (which may (WILL) take longer due to <vibration> (interpreted by the INS as movement) then select NAV.

"The aircraft MUST remain STATIONARY while the INS is in ALIGN...."

If you "Start" the alignment at the beginning of your preflight you will have plenty of time for the process to align the INS (15-20 min or so…) select NAV and the system will run on battery power if you must remove AC power.

If you are short on time you can "quick align" but you MUST do the full alignment prior to “quick align†but the accuracy is degraded by up to 4 miles per hour. So not so good…

AND You must do a FULL preflight alignment and select NAV, the switch MUST NOT stay in NAV for more than 5 sec... then select OFF.

When you return to the aircraft you can Rapid align by selecting STBY, select POS, press HOLD,9, and INSERT. Verify POS, select ALIGN…. Should take about 6-7 min.

Bottom line you should ALIGN and select NAV prior to engine start…. If you move the aircraft PRIOR to selecting NAV your solutions will be invalid.

If you are just starting to “move†the aircraft you can select ATT REF and taxi…..

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