IRS Fault 737NG

[high flyer 13]

Hi guys just a quick question

Regarding an IRS Fault on a 737NG and can i still use the F/D, according to the QRH checklist im no longer able to use the autopilot.
But im wondering can i still use the F/D if i switch the IRS mode selector on failed side to ATT and let it re-level after 30secs etc etc ??
I know autopilot uses pitch data from on-side IRU and roll data from the other IRU so this would tell me that if i reset the IRS using the ATT selection and the outcome is successful i can use the F/D ??
The other option in the QRH is to switch the failed side onto the functioning IRS using the IRS switch L or R, so im thinking if this option is used the F/D can no longer be used as i then just have one source of data.

Just want to clear this up and thanks for any replies.:ok:

[latetonite]

What is your dilemma with one data source? What are the requirements for an ILS approach? What are the requirements for an Autoland?

[FlyingStone]

If you put IRS transfer switch to the operating side, you will have both F/D and A/P.

The reason why QRH (and the MMEL) say A/P should not be used is because you are left with only one source of data and no way of knowing whether the supplieed data is faulty or not.

[repulo]

Nope, AP will not necessarily work. Depends on the config, eg with the analog SBY ATT indicator it won't work. With the ISFD usually the AP will work with one ADIRU failed.
Had one fail on me and had to handfly quite some time..