June 22, 201213 yr So if you cycle/restart both IRU's mid-flight you lose all navigational information on your nav display - I actually didn't know that. I always assumed I'd be able to replug the current lat/longs and it would resupply me with a current position on the nav page. That sounds sort of silly from a pilot perspective; Flying without magenta lines is like flying without wings! :P [Disclaimer: That was a joke!] Is it also true you can align the IRU's during taxi so long as you remain below 5 knots? I heard that from a 747 pilot once. Take-offs are optional, landings are mandatory.The only time you have too much fuel is when you're on fire. To make a small fortune in aviation you must start with a large fortune.There's nothing less important than the runway behind you and the altitude above you. It's better to be on the ground wishing you were in the air, than in the air wishing you were on the ground.
June 22, 201213 yr No, aircraft must remain at the parking for the entire alignment, strong winds, passenger boarding or possibly also refueling could give errors during alignment. About IFSD, it will use NAV 1 to show navigation information like VOR or ILS. The last dual IRS failure on a 737-400 ended with a crash few years ago. Only one IRS was failed, but the crew realigned both at the same time to ATT inside a storm. Regards Andrea Daviero
June 22, 201213 yr The standby RMI uses IRS heading. In theory, the RMI should still point in the correct relative direction (i.e. if the station is directly left of your position, the needle should point left), but the compass card will be out if there is no IRS heading. David Zhong New video every Thursday: Aircraft Lighting - Boeing 777
June 22, 201213 yr I have a question: How should I navigate if both of the IRS (L and R) fail? Because when I switch them off inflight my ND goes blank and all that I have left is the old-school magnetic compass. I understand that autoland doesnt work because of the loss of IRS data mut it should not affect the GPS? Shouldn't the GPS of the aircraft be sufficient to provide waypoints, distances etc to the ND? Of course the atc can give me vectors etc but I dont believe its realistic that all the aids for navigation are lost if both IRS fail? Only procedure I can find in the QRH is the one that tells me to put the IRS to att to get attitude information and I get that but what shoud I do to know where I am and where I am going?? Could someone with more knowledge about IRS/GPS systems of the 737-/800/900 explain this to me? Thanks in advance! You can check this discuss. http://forum.avsim.net/topic/353058-one-irs-to-command-fmc-for-input-to-autoflight/page__p__2154269__hl__fjsharry__fromsearch__1#entry2154269 Jia-Hsing Fu
June 22, 201213 yr Author I also found out that if I turn off both IRS the app or VOR modes of my ND will not work either. So it seems if both IRS are swithed off/failed you have NO navigation aid whatsoever left. No idea where you are and no possibility to even go back to conventional navigation. How can the VOR receivefrs be dependent of the IRS?
June 22, 201213 yr Commercial Member I also found out that if I turn off both IRS the app or VOR modes of my ND will not work either. So it seems if both IRS are swithed off/failed you have NO navigation aid whatsoever left. No idea where you are and no possibility to even go back to conventional navigation. How can the VOR receivefrs be dependent of the IRS? You just need to look a little harder. Look between the ND and the EICAS, just above the Capt FMC... That's a type of VOR display you'd see in tons of aircraft. I won't let you tune a radial, but you could always fly that radial if you were good enough (though I doubt some peoples' skill on the matter, because the requirement for tracking NDB - or even NDB-like - courses is getting phased out with NDBs, and this would require that skill). Keep in mind that in this type of plane there really isn't a situation you wouldn't be talking to ATC, so they can always place you on vectors. Kyle Rodgers
June 22, 201213 yr I also found out that if I turn off both IRS the app or VOR modes of my ND will not work either. So it seems if both IRS are swithed off/failed you have NO navigation aid whatsoever left. No idea where you are and no possibility to even go back to conventional navigation. How can the VOR receivefrs be dependent of the IRS? I tried an ILS approach with the IRS failure and the the dots that show your ILS position showed up, both on the ISFD and on the PFD. That's a type of VOR display you'd see in tons of aircraft. I won't let you tune a radial, but you could always fly that radial if you were good enough (though I doubt some peoples' skill on the matter, because the requirement for tracking NDB - or even NDB-like - courses is getting phased out with NDBs, and this would require that skill). Does that mean that under a double IRS failure the relative direction to a VOR is visible on the RMI up or not? Manfred G. Ships are cooler that you think.
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