Atpl's Nav/Inst problem

[nunos]

As you can see i'm blue in the face trying, (possibly too hard!)to understand the working's of inertial navagation systems, has/is anyone else out there having/had a similar headache with this small, yet very confusing,little instrument, did you get any "outside" help? or what?. .any advice greatly appreciated! <img border="0" title="" alt="[Confused]" src="confused.gif" />

[Tucano]

Ah, the INS.... .. .The only question I have ever heard of in the JAA Instrumentation paper is:. .. .What is the Schuler period?. .. .a) 84 minutes. .b) 12 minutes. .c) 72 Seconds. .d) 84 seconds. .. .Maybe this helps? <img border="0" title="" alt="[Razz]" src="tongue.gif" />

[nunos]

thanks for the reply. I'll answer 'a'. does this mean i've passed? chr1st if it were only that easy!

[avrodamo]

It's a nightmare isnt it? I put a very similar post on here a few months back.. .My advice is to sit down with your notes, and make headings to break down its operation.. .Cover firstly the 2 systems-stable platform and strapdown.Into these then cover the operation of each what really makes it work. In a stable platform its accelerometers and rate integrating gyros, in a strapdown it's ring laser gyros and accelerometers.. .Its important that you always remember that even if the aircraft is stationary the platform is is moving to remain fixed in azimuth to account for earth rotation. With the aircraft moving it then has to account for aircraft movement and transport wander. This really applies to the gyros wether it be ring laser or RI gyros.. .The accelerometers need to sense only aircraft acceleration. To do this it has to remove accelerations caused by centripetal force, and coriolis effect.. .Schuler tuning ensures that the platform correctly follows the curvature of the earth in relation to horizontal. To do this it oscillates at a period of 84.4 minutes to correct errors, and these are bounded errors.. .On your breakdown then put key points for what it requires in a working environment in particular what it requires at startup, and how by using gyro compassing it aligns itself in azimuth.. .Lastly you must be able to caculate its error rate. This is a fairly simple calculation that will be explained in your notes.. .I just didn't get it at all until i broke it down like this.. .Hope this helps !! Best of luck <img border="0" title="" alt="[Razz]" src="tongue.gif" />

[Chris2]

Thanks Avrodamo. .. .That is the best summary of INS I have found!. .. .Regards. .Dutchie

[Dutchie]

What a nice name you carry mate..... .. .Kind regards, . .Dutchie

[Chris2]

Hey Dutchie is that better !!!. .. .Sorry mate hope you feel better now <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> . .. .Regards. ."Cloggie"

[nunos]

hi avrodamo. .thanks for the tip and good advice, sometimes it's just good to hear from others who know exactly what your problems are (the usual, been there and have the T shirt senario). .you seemed to have had it sussed! good on U!

[jessie01]

dont worry yourself about understanding the concepts because they dont ask about it in the exam. Just remember the answer to the question and you'll get it right.Its the same as compass swing questions that take up about 15 pages in the notes, have you ever seen a question that asks for co-efficiency of a , b and c? No , and i dont think your likely too.Just concentrate on the practical side of navigation and you wont go far wrong.You are also likely to get no more than 2 questions on PNR and CRit point plus 1 on relative velocity and the rest made up of whizz wheel questions and a bit of INS nav with learnt answers.. .. .i have taken this exam twice so hope to get through this time , but my advice is to get up to speed on plotting etc and be a dap hand at whizz wheel.. .good luck