INS vs IRS
 

Hi folks,

This is probably an old question, but what is the main difference between INS and IRS?

INS= older less complex basic accellerometer/gyro nav system
IRS= more modern ring laser gyro system incorporating various other nav inputs.

Just need to know if I'm on the right track here (pardon the punn)

Cheers

JK:ugh:

How about:

INS = older, self contained nav system with mechanical gyros and accelerometers.
IRS = an integrated inertial reference system using RLGs with no navigation function but outputs to navigation and other systems (FMS, autopilot, wx radar instruments etc.)

...and a period of transition where aircraft like the TriStar and 747 were built with old INS systems integrated into the design and fulfilling the functions of a modern IRS.

Many Thanks Alex!!!!!!!:ok:

I believe this answer is innacurate. Our Litton-92 INS has laser gyros. It is used to power one of the aircraft ADI's as well.

http://www.irconnect.com/noc/press/p....mhtml?d=16594

To quote "The Litton LTN-92 system is an ARINC 561 strapdown INS with full ARINC 704 digital interface capability. The LTN-92 uses state-of-the-art ring laser gyroscopes and is the ideal choice for replacement of earlier, low reliability "spinning wheel" inertial systems."

I think it's more of a 'tomayto vs tomahto' thing...

INS, IMU, IRS, and maybe several more names for the inertial reference that provides acceleration and re-position (somebody has to provide it with an initial position...) data to the navigation system.

Current systems have many more inputs and outputs than the older ones, and use fewer moving parts to do essentially the same thing, better.

Call it what you want. I think the common word will still be "inertial."

INS is an Inertial Navigation System The box can navigate all by itself. Fitted to B737 Classic B757 B767 and all older aircraft.
IRS is an Inertial Reference System. A box full of laser gyros which gives position and attitude but cannot navigate. B777 .

Easy way to tell the difference is can you enter posn on the IRS? NO you can only turn it on.

Maybe I am misunderstanding your definition but when we are out of class 1 navigation service volume we receive a message "IRS ONLY", I believe this counts as navigation, am I missing something, thanks.:confused:

Dream - my understanding is that that system is not certified for sole-use navigation UNLESS updated by DME/DME etc. Yes it will tell you where it THINKS it is, which may not be where it really is (and I have seen 30 mile errors in NDB only land) but it will always give you attitude 'REFERENCE', hence the 'R'. Most SOPs accordingly call for basic navigation checks on receipt of the 'IRS only' warning.

INS navigates (tell it where you want to go and it will tell you how to get there - usually via the flight director and almost always can be coupled to the autopilot. The heading and attitude outputs are a useful by product of the stable platform (either virtual or physical) used to supply the navigation circuits with groundspeed and direction information) The system is stand alone.
IRS only supplies reference information (attitude, heading, speed, acceleration, etc,etc,etc. This is then fed to other systems which calculate a navigation solution (FMGS) or display the output as a compass rose or attitude ball.) The system cannot navigate, it can only provide present position information.
The details of the internal mechanisms are irrelevant. There are INS's that use RLG's and IRS's that use standard rate gyros.


Swedish, :=


I think you need to read up on your INS/IRS theory. All 757 and 767's have IRS fitted (there may be some private/modded ones that don't but I'm not aware of any) as do the 73 classic (i.e 300/400/500) and you DO have to put PPOS into it. How can an inertial system tell you where you are if you don't tell it where you started!!???????
You may be confused with systems which automatically input PPOS based on GPS data. However the data still needs to be inputted (sp?)
Hope you're not flying or maintaining a/c based on this rather sketchy information??!!