Difference between IRS and INS

[bluehawaii]

Ladies and Gents, does anybody know the difference between an IRS (inertial reference system) and an INS (inertial navigation system)?

[bfisk]

IRS is essentially a newer version of the INS. Works on the same principles but contains solid-state electronics instead of moving mechanicas parts (ie ring-laser gyros as opposed to mechanical gyros). IRSs are often referred to as strapdown systems because they don't need to be gyroscopically stabilised/motored, but can be fixed to the fuselage.

Both are however rather generic terms so other differences an nuances may also exist.

[BOAC]

That is incorrect. There has been confusion here since the first systems appeared.

IRS - Inertial Reference System - "which way up am I and where am I pointing"? That's all!

INS - Uses IRS, and in addition feeds acceleration data into a computer to work out where you are now, knowing where you started and how fast you have flown and in which direction.

The clues are in the 'R' and the 'N'.

Both IRS and INS can work in any way, from gears and rubber bands through to solid state 'strap-down' systems. The terms do not denote any particular sort of construction or operation.

[BizJetJock]

Still not quite right. That is the difference between AHRS and INS.
IRS output position data as well, which is then used used by an FMS or similar as one of its position sources to compare with GPS, VOR/DME, etc.

[BOAC]

OK, then BJJ - now tell us what an INS is.

[ampclamp]

IRS uses laser gyros and accelerometers ie 737-400 767-200/300, INS uses mech gyros ie 747 classics.
They to change the name cos they like new acronyms.:rolleyes:

[BizJetJock]

An INS, as found on older machines that predate FMS, is capable of standalone navigation with waypoint entry and output of track error and distance to go, usually with multiple waypoints and automatic sequencing.
So you have:
AHRS - attitude and heading only
IRS - also position (and TRK/GS)
INS - able to navigate you to where you want to go.

I have used all three.

In principle any of them can be either mechanical or laser gyros, but in practice the more modern AHRS and IRS are almost always Laser. I don't know of any INS's that weren't mechanical, but I didn't use all of them, so wouldn't like to be quoted on that.

Trivia to pass a long flight really.

[411A]

SVA had triple ISS (Inertial Sensor System) on thier L1011 aircraft, essentially an IRS, which fed dual Hamilton Sundstrand FMS units, which in turn provided complete LNAV/VNAV/full time engine thrust management....and a CRT moving map, thrown in for good measure.
Worked very well in service....circa 1977, and beyond.

[PENKO]

BOAC, I have not seen anything but IRS on any aircraft I fly.
The original explanation was correct according to my books. IRS does the same thing as an INS, however the IRS uses laser gyroscopes in stead of mechanical ones. That is also the answer that the JAA-ATPL guys prefer :}
Or maybe we are both right and it comes down to semantics. But there certainly is no INS on the 320.

Further more, the IRS's deliver all the attitude data to the glass cockpit of the 320 and 737.

[BOAC]

Maybe, Penko - I'm actually out of this thread.

If that is the answer the 'JAA-ATPL guys prefer' then that is the one to give to get a licence!:)

[PENKO]

I'm sure you'll understand why I used that big smiley BOAC!

[superiorfly]

Can I say the INS do the thing about navigation itself, and IRS just send the signal of position to the machines, FMSs most of time, and let that machines do the job?:confused:

[syedo]

INS : Inertial navigation system - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Inertial_navigation_system)

go wiki!! ;)