What exactly is 'steer lock'?

[oneleg]

Taken literally, it means you can't steer. The nose wheel is locked and therefore you can't move it manually.

But that is not how it behaves in Xtreme Prototype's Lear 25D which is study level ie. simulates real life to the extent possible in the sim.  Apparently, the nose wheel can still be turned 45 degrees to the left or right when steer lock is on or engaged.  On the annunciator panel the 'steer on' lights up when steer lock is electronically engaged.

So the question is, what is 'steer lock'?  What is it locking?

[tiger1962]

1 hour ago, oneleg said:

So the question is, what is 'steer lock'?  What is it locking?

 

It is locking the nosewheel to the tiller or other steering mechanism in the cockpit. It needs to unlocked for towing or pushback: Nose Wheel Steering | SKYbrary Aviation Safety

 

"Many aircraft are subject to pushback procedures in the course of day-to-day operations and virtually all are routinely towed from place to place whilst on the ground. As normal towing or pushback protocols have the potential to exceed maximum nose wheel deflection limitations or to damage hydraulically actuated steering components, features are often incorporated in the nose wheel steering design to ensure safe towing operations. In many cases, the mechanical steering linkage can be physically disconnected allowing the nose wheel to freely castor. In others, a hydraulic bypass mechanism, which can be "pinned" to disable the steering actuator, is incorporated. In all cases, the aircraft must be properly configured prior to commencing towing or pushback operations. It is also important that the bypass pin be removed or that the steering link be reconnected before the aircraft commences taxy."

 

 

[oneleg]

Great explanation. Thank you.

So if the plane is going to be towed, it needs to be unlocked. While taxing, it should be locked so as to give the pilot control over the nose wheel steering.

But at take-off, should it be locked or unlocked?

[tiger1962]

The steering should only be unlocked for pushback or towing.

[nsproles]

7 hours ago, oneleg said:

Taken literally, it means you can't steer. The nose wheel is locked and therefore you can't move it manually.
 

On the FBW A320, during push back and towing, the annunciator in the cockpit shows a warning, in red, indicating that nosewheel steering is disconnected.  'Disconnected' may be a clearer statement than saying that the steering is locked.

[oneleg]

1 hour ago, nsproles said:

On the FBW A320, during push back and towing, the annunciator in the cockpit shows a warning, in red, indicating that nosewheel steering is disconnected.  'Disconnected' may be a clearer statement than saying that the steering is locked.

Thank you all.  It seems to me another alternative is to simply avoid the word 'lock'.  Maybe it would be clearer if it simply says: 'Steering Ok' and 'Steering Not OK'. But that may be problematic also since my understanding is that the pilot can still steer the plane even though it is unlocked.... hmmmm.... maybe it should just say 'Tow OK' and Tow Not Ok'....