B737 NG ANTISKID INOP NNC

[owl-attack]

Why does the ANTISKID INOP NNC in the QRH ask you to not arm the speed brakes for landing and deploy it manually.

A lot of people have said it is because with ANTISKID INOP wheel spin detection may be affected. But i have read in the FCOM if wheel spin up is not detected the speed brakes will still deploy if the speedbrake lever is in the arm detent and either main gear touches down

So what could be the reason behind not arming speedbrakes with antiskid inop?

Regards

[latetonite]

Think you can be more quick manually, and so reduce your landing distance.

[Skyjob]

Anti-skid may be only be deemed inop due to inoperative required associated systems which can be shared between the anti-skid and other systems.

Thus when anti-skid is deemed inop its root cause may also affect proper functioning of other systems such as but not limited to automatic speedbrake deployment.

As it would take to many scenarios to be described, manual speedbrake deployment is taken into account when the anti-skid is deemed inop, as it could be an associated system such as the wheel spin up sensor or weigh on weels logic not functioning properly.

[de facto]

Anti-skid may be only be deemed inop due to inoperative required associated systems which can be shared between the anti-skid and other systems.

Thus when anti-skid is deemed inop its root cause may also affect proper functioning of other systems such as but not limited to automatic speedbrake deployment.

Correct,the speedbrake lever arm switch sends input to the AACU.Its relationship can be seen by retracting the speedbrakes after landing which will cause a disengagement of the AUtobrakes.
A safeguard for the autobrakes not to engage upon landing when the other inputs to the aacu occur.

latetonite Think you can be more quick manually, and so reduce your landing distance.


Not sure what you mean..

[masalama]

From the MRG ,

ANTI SKID is one of the inputs to the Autobrake arm logic that if INOP gives SPEEDBRAKES DO NOT ARM annunciator .

From one of our engineers, the wheel spin up signal is derived from the anti-skids, therefore if INOP cannot provide the wheel-spinup signal necessary for Auto Speedbrake deployment.This automatically would give the SPEEDBRAKE DO NOT ARM annunciator if we tried to arm the speedbrake lever.

Therefore, the requirement in the ANTISKID INOP checklist to manually deploy the speebrakes on landing.

[owl-attack]

the wheel spin up signal is derived from the anti-skids, therefore if INOP cannot provide the wheel-spinup signal necessary for Auto Speedbrake deployment.This automatically would give the SPEEDBRAKE DO NOT ARM annunciator if we tried to arm the speedbrake lever.

Therefore, the requirement in the ANTISKID INOP checklist to manually deploy the speebrakes on landing.

I get what u say, but the FCOM clearly says that if wheel spin up is not detected the speedbrakes will still deploy when the main gears compress

So with antiskid inop if you are telling me that we do not arm the speedbrakes because wheel spin up detection might be affected and automatic speed brake deployment might not happen, but I am saying as per fcom automatic speedbrakes deployment should still happen when the main gear is compressed

I still didnt get the answer

[latetonite]

Think you answered the question yourself.
If you wouls arm the speedbrake, it would only lead you to another unnecessary checklist.