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Paul12

Align ATT mode

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When and why would a pilot switch to ALIGN ATT mode ?

What are the advantages and how would he continue to fly ?

 

I noticed that after switching to ATT mode VNav and the autopilot disconnect and cannot be

reconnected again  ?

 

So what then is the purpose of ATT mode ?

 

Thank your for you explanations/help

 

HubertWerni

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Its just a downgraded mode that only supplys ATTitude info only and heading info. And no NAVigation whatsoever!

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You don't want to get yourself in this situation. In fact, I would welcome something that prevented anyone from switching off the IRUs accidentally or intentionally during flight.

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Its just a downgraded mode that only supplys ATTitude info only and heading info. And no NAVigation whatsoever!

 

It only provides attitude, it does not provide any heading info.  You need to manually enter the heading into the CDU in the ATT mode.

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Hi joe that is correct i was going to quote that from my FCOM 2 but i was hoping the OP would of read that up !???

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Hi joe that is correct i was going to quote that from my FCOM 2 but i was hoping the OP would of read that up !???

 

Hoping someone reads the manual? Man, if people did that my job would be stupidly easy...

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Hoping someone reads the manual? Man, if people did that my job would be stupidly easy...

 

So would my "studies" be ( stupideasy ) if the questions were propely answered.

Namely : why and under what circumstances would a pilot switch to ATT ( I assume the ATT switch is not there

just for fun  ) and how would he continue ?

 

HubertWerni

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Namely : why and under what circumstances would a pilot switch to ATT ( I assume the ATT switch is not there

just for fun  ) and how would he continue ?

 

I figured that, based on the responses (to include and FCOM reference - though my point is somewhat proven by this), it would be somewhat obvious:

 

Since ATT only supplied ATTitude information, then it's obviously a downgraded mode to give you attitude information from an IRU NAV failure.

 

Switch to ATT. Enter heading. Continue flying (at this point, you'd likely need to switch to /A and use VOR radials).

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You don't want to get yourself in this situation. In fact, I would welcome something that prevented anyone from switching off the IRUs accidentally or intentionally during flight.

Not a bad idea. In the aircraft you'd have to pull the knob out to be able to rotate it out of NAV. In the sim a double click could do a similar thing (one click to pull then another click or use the mouse scroll to rotate). The CIVA INS panel has this feature. It prevents you inadvertently losing alignment.

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When and why would a pilot switch to ALIGN ATT mode ?

What are the advantages and how would he continue to fly ?

 

I noticed that after switching to ATT mode VNav and the autopilot disconnect and cannot be

reconnected again  ?

 

So what then is the purpose of ATT mode ?

 

Thank your for you explanations/help

 

HubertWerni

 

The QRH abnormal procedures are a great learning aid for when you are trying to figure out the "why" behind things.  There is a lot of good supplemental information buried in there.

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When and why would a pilot switch to ALIGN ATT mode ?

What are the advantages and how would he continue to fly ?

 

I noticed that after switching to ATT mode VNav and the autopilot disconnect and cannot be

reconnected again ?

 

So what then is the purpose of ATT mode ?

 

Thank your for you explanations/help

 

HubertWerni

You'd use ATT reference in the event of one of your IRS's losing Alignment whilst in flight.

 

You'd get the wailing sound (A/P Disconnect), you'd lose attitude/nav information on the failed IRS side and you'd get Master Caution, IRS and the Fault light would illuminate.

Its just a downgraded mode that only supplys ATTitude info only and heading info. And no NAVigation whatsoever!

I see a lot of people have mentioned no navigational information is available. If you were unfortunate to have a dual IRS failure (you're having a very bad day) you would have to navigate traditionally. Having just a fault with just one IRS you can still navigate using the FMC, it just won't give information to the PFD. You can use the IRS transfer switch to feed information to both PFD/ND's from one IRS. Both autopilots are however unavailable as they need to use information from the IRS so you'd have to fly raw data.

 

IRS ATT mode is designed to partially restore basic attitude information to the failed side (pitch roll and heading). Using ATT mode is irreversible in flight and once selected you have to maintain straight and level and at a constant airspeed until the failed attitude display recovers. Once the alignment is complete and the Fault light extinguishes you have to manually update your magnetic heading on the POS INIT page in the FMC or on the overhead IRS display.

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There was a case in january 2007 with a crash from ADAM air caused by the malfunction of IRS and pilot error:On 25 March 2008, the inquiry ruled that pilot error and a faulty navigation device downed the airliner.[1][85] While cruising at 35,000 feet (10,668 m), the pilots became preoccupied with troubleshooting the aircraft's two inertial reference systems (IRS), part of the navigation system. The autopilot became disengaged and the pilots failed to correct for a slow right roll even after a "bank angle" alarm sounded. Despite the bank angle reaching 100° with almost 60° nose down attitude, the pilots did not level the wings before trying to regain pitch control. The aircraft reached 490 knots (910 km/h) at the end of the recording, in excess of the aircraft's maximum rated speed for a dive (400 knots (740 km/h)). The descent rate varied during the fatal dive, with a maximum recorded value of 53,760 feet per minute. The aircraft began to suffer small structural failures twenty seconds prior to the end of the recording, at which time the investigators concluded the aircraft was in a "critically unrecoverable state". Both flight recorders ceased to function when the 737 broke up in mid-air at 9,000 feet above sea level."

Read the hole article here: https://en.m.wikipedia.org/wiki/Adam_Air_Flight_574

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When and why would a pilot switch to ALIGN ATT mode ?

What are the advantages and how would he continue to fly ?

 

I noticed that after switching to ATT mode VNav and the autopilot disconnect and cannot be

reconnected again ?

 

So what then is the purpose of ATT mode ?

 

Thank your for you explanations/help

 

HubertWerni

You'd use ATT reference in the event of one of your IRS's losing Alignment whilst in flight.

 

You'd get the wailing sound (A/P Disconnect), you'd lose attitude/nav information on the failed IRS side and you'd get Master Caution, IRS and the Fault light would illuminate.

Its just a downgraded mode that only supplys ATTitude info only and heading info. And no NAVigation whatsoever!

I see a lot of people have mentioned no navigational information is available. If you were unfortunate to have a dual IRS failure (you're having a very bad day) you would have to navigate traditionally. Having just a fault with just one IRS you can still navigate using the FMC, it just won't give information to the PFD. You can use the IRS transfer switch to feed information to both PFD/ND's from one IRS. Both autopilots are however unavailable as they need to use information from the IRS so you'd have to fly raw data.

 

IRS ATT mode is designed to partially restore basic attitude information to the failed side (pitch roll and heading). Using ATT mode is irreversible in flight and once selected you have to maintain straight and level and at a constant airspeed until the failed attitude display recovers. Once the alignment is complete and the Fault light extinguishes you have to manually update your magnetic heading on the POS INIT page in the FMC or on the overhead IRS display.

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