A320 Triple IRS Failure

[captain87]

:confused: A320: In case of a Triple IRS Failure in flight (if possible) the NAV accuracy reverts to LOW. Do we continue navigation using GPS data or raw data ? I personally suppose that this scenario brings the pilots to fly by raw data only. Is the A320 approved to fly by GPS's only without any kind of NAV redundancy ? ...

Thank you and Best regards

by captain87

[flash2002]

I don't know anything about the airbus. But wouldn't this scenario mean you would loose all attitude+heading information??? Even if you could revive this info by putting it in manually you would still need to land asap...........

[dartagnan]

the nav1(ILS, VOR) is still working so you can navigate and make an ILScat1 approach.

[captain87]

Yes, all attitude + heading informations are lost even if we can perform a recover anytime by setting them manually (IRS sel from NAV to ATT).
This thread doesn't keep in mind the air data field but navigation.

Cheers

[flash2002]

Well so your back to gps or raw data vor/ndb/ils tracking. I would suggest using both... you never know what those americans are doing to the signal ;-)
I dont really understand the problem... you wouldn't / couldn't proceed all the way to destination, unless you are very close to it.

Its not yet allowed to fly a gps approach so you would need rawdata for this. With regard to airways, I think you could use gps only.

[captain87]

Dartagnan,
ILS + VOR are still working ... we navigate by using raw data. ... Are the GPS's still serviceable ? ... Could we still use them for navigation ?
I didn't succeed to find this information on FCOM's .

Thank

[Clandestino]

In case of a Triple IRS Failure in flight (if possible) the NAV accuracy reverts to LOW

Now that's as good as understatement as they go. While some folks might call it LOW, more accurate description of it would be: NONE.

GPS recievers are still serviceable but their output is used to feed IR part of the GNADIRS only (in order to calculate hybrid IRS-GPS position). There's no bypass or override that can send GPS position to the FMGSes - see scheme in FCOM 1.34.15. So with triple IRS failure (assuming complete failure, so ATT is lost too) in flight you're down to hand flying on stby instruments, in direct law. VOR/DME/ADF/ILS are still operative, but what will ND look like is anyone's guess as you will have no HDG data to allign your compass rose with your heading.

But don't loose any sleep over it, triple IR fault is considered to be so unlikey by the Airboos that there's no procedure to deal with it, unlike single or dual failures. Also all of the dual IRS failures I've heard of, developed after the airplane was dispatched with one IRS inop.

[captain87]

Clandestino,
thank you very much for your answer that is what I expected to know.
In fact there aren't procedures dealing with a Triple IRS Failure in PRH.
With the loss of three IRS, are the ADIRS still capable of providing AD (Air Data Informations) without IRS ? ... Are both GPS's still using their MMR (Multi Mode Receivers) to "supply" the ADIRS ?

That was I asked in this thread. Thank you at all.

by captain87

[NigelOnDraft]

I personally suppose that this scenario brings the pilots to fly by raw data only. How are you going to use "Raw Data"? No ADIRS = no ND as far as I can see, and even if fitted / serviceable, no DDRMI :{
How are you going to use GPS? You will have raw Lat/Long information only I think - great to try and "navigate by" ;)From a quick think, you are basically into "looking out of the window" or "ask the nice ATC man" to help you out :D
NoD

[captain87]

This kind of abnormal seems to be more difficult than I expected.
So there is no backup for navigation ... Should we proceed for visual ?

[DBate]

Should we proceed for visual ?

I would prefer radar vectors anytime. With a triple IRU fault you will be busy enough flying the airplane. Using all resources - and I consider ATC to be one - I would ask the controller for vectors to the nearest suitable field to shoot the approach.

[captain87]

:bored: Ok, so it depends on situation. Obviously visual navigation should be avoided anytime the IRS's are lost, expecially if flying within crowded airspaces.

[Loose rivets]

you're down to hand flying on stby instruments, in direct law. VOR/DME/ADF/ILS are still operative,


Luxury! We used to dream of having all that stuff.

[Clarence Oveur]

VOR/DME/ADF/ILS are still operativeDo the VOR and ADF indication require a valid heading?

[Wodrick]

VOR requires valid heading to show a valid bearing on a RMI, for the deviation bar to work against a pre set course a valid heading is also required.
ADF does not REQUIRE a valid heading to indicate correctly as it always indicates relative bearing, however, conventionally, this is usually in a RMI or HSI presentation which of course needs a heading input.
My (engineering) opinion is that you wold be up the proverbial creek wihout a paddle and vectors for visual on stby instruments with perhaps a little assistance from the NDBs is the only solution.

[Clarence Oveur]

Thanks Wodrick. I do know how VOR and ADF usually work, and was asking in the context of the thread. It has been suggested that VOR and ADF will still be available after loss of all 3 IRS on a A320.

I was just curious how that could be.

[jetjockey737]

erm....I might be wrong but in this situation surely you would be down to the use of the ISIS and the stby compass...In direct law! The ISIS only has LOC and Glideslope info. No heading info ( well it is an option but I have never seen it), so you would be relying on vectors to an ils / loc only approach. Or an SRA or visual I suppose.....good luck!!

[captain87]

:) It's quite ridicolous for an A320 being flown visually ... Direct Law - No NAV Info - No Attitude Info - No Heading Info ... if anything else might occur it would be a right way for the pilots to pull the "ejections seat" handle ! I think that flying by Standby Compass with the A320 would be very hard anyway ...

by captain87

[jetjockey737]

Captain 87.

The airbus is an aircraft like any other, if it all goes wrong then you revert to basics. You would get attitude info on the isis along with airspeed and altitude. You also get glide and loc info. As well as that you have the standby nav instruments for VOR/DME/ADF info, so all in all you are just reverting to a jet powered seneca.

My point in my previous post, which having reread didnt come across, was that at the point when it all goes dark and you are relying on stby instruments maybe an ILS would be the most desired choice.....

[NigelOnDraft]

JJ737
The airbus is an aircraft like any other :confused:
You would get attitude info on the isis along with airspeed and altitude'isis' ?? But yes, A320 series do have tiny Sby AI, Alt and ASI...
you have the standby nav instruments for VOR/DME/ADF info, so all in all you are just reverting to a jet powered senecaReally? My understanding is that the DDRMI (Sby DI thing) is powered by the IRS output, so no IRS = no DDRMI = no ADF/VOR etc.
Bear in mind in e.g. our fleet, most DDRMIs have been "inop" for years, and the newest aircraft do not even have them fitted...
NoD

[Honkozzie]

NigelOnDraft,
all correct as regards the stby instrumentation, however, GPS position, goemetric altitude and groundspeed info is all still avble on the GPS monitor page in the MCDU, although the last one may be blended with IRS info....i'm pretty sure the 320 bus has that facility- certainly the 330 and 340 bus' do. Rather useful page to have up on a dark and stormy night when it all goes black.

[NigelOnDraft]

however, GPS position, goemetric altitude and groundspeed info is all still avble on the GPS monitor page in the MCDUIf you have GPS ;) (not all ours do...)
As I said earlier though, navigating by Lat/Long readout while flying on Sby Insts is not a skill well practiced. There if required, but you'd be bl**dy unlucky not have a radar service and/or look out of the windows :confused:
Anyone for a "No Compass No Gyro" let down "turn left now.... stop turn now" :eek:
NoD

[jetjockey737]

NOD.

Yes the airbus is like any other aircraft....:confused::confused::confused:
Yes you can revert to basics....:sad::sad::sad:
Yes you are right..the DDRMI is fed from the IRSs..( I humbly apologise for this mistake).:D

Cheers JJ

P.s. The ISIS is the integrated standby instrument system!! And you have always got the standby compass;)

[captain87]

Yes the airbus is like any other aircraft....


I think Airbus should never be considered like another aircraft ! ... is always much more than simply an aircraft ... I think that level of redundancy offered by Airbus cannot be compared with others manufacturers anyway. Mechanical Backup means that sever failures have occurred before; considering a Boeing 737 with the same number of failures, I would consider it as already crashed ! ...
I kept in mind a Triple IRS Failure having a doubt about what should be do in that situation, but when does this kind of failure go to happen ? ... it's nearly impossible !

;) Best of all,
captain87

[Kraut]

Anyone for a "No Compass No Gyro" let down "turn left now.... stop turn now" from NigelON draft

That was how I recovered it last in the Sim. However, are civil controllers trained to do that?

[Nick 1]

Captain 87 ,
don't be so sure that Emergency Proc. on the books are impossible to occur, and that 320 is not like any others aircraft .
Because one of this days maybe you have to learn to flying it like stick and rudder a/c.
If you loose both AC bus during the take off ( image by night) until the Ram Air Turbine pressurize the Blue hyd and emergency generator come online , you are on STBY intruments only.
And i don't think is the right moment to learn some row data handling.
Cheers.

[cribble]

:cool: Pas de problem. Get/stay visual, radar facillitated circling R/V, lead change, pairs approach, kiss-off at short final.

[captain87]

Nick1

:ok: I absolutely agree with you ! ... said that, I think that everyone who hold a commercial license must be able to revert to basics anytime. Obviously night-flying is not the best moment in which we should train to do that !

An Airbus 320 is never an airplane like another, because in that situation the other aircraft we keep in mind would always crash before ... We can analize a similar to Airbus in terms of redundancy: the new Dassult Falcon 7x.
" Mechanical controls means flying roughly, FlyByWire means flying safely ! "

Best Regards,
captain87

[Togue]

FCTM ADR/IRS FAULT AO-34 P 1/8

[giggitygiggity]

:cool: Pas de problem. Get/stay visual, radar facillitated circling R/V, lead change, pairs approach, kiss-off at short final.

Get visual, stay visual..? Should Airbus be banned from UK airspace?!

[vilas]

Nick 1
If you loose both AC bus during the take off ( image by night) until the Ram Air Turbine pressurize the Blue hyd and emergency generator come online , you are on STBY intruments only.
Time for ground refresher and Capt87 you surely don't agree with him. You always have PFD from batteries. After 8 seconds the RAT powers blue and you also get ND.

[Max Angle]

Is the 8 year gap between posts 28 and 29 a new record I wonder.

[vilas]

Wow! Never noticed that. Why was reopened I wonder.

[vilas]

Max Angle
Wow! Never noticed that. Why was it reopened I wonder.

[Togue]

Vilas,
I resurrected the thread because I was looking for another topic and found that this one has and interesting one. Triple IRS failure is interesting. Very improbable scenario but not impossible. And by discussing this type of troubles we get to know and understand the aircraft systems better. Had I opened a new thread on it, I am sure someone would have posted a link to another thread that relates to the topic. So I decided to use the "search" function. I thank you for your explanation.

Max Angle,
I guess is a new record.
Did I earn a medal?