Hi:

Does anyone know what's the meaning of a message in green that's frequently (I always get it) displayed on the EWD in the ATR saying "TLU LO SPEED". According to the ATR's FCOM TLU stands for Travel Limiter Unit, which is related to the movement of the rudder to structurally protect it against forces produced at high-speeds. 

Until now, I don't have any idea on know how to get rid of it and be able to complete/pass the TO Config OK check, as it's always displayed and there's the ringing suggesting something's wrong with the aircraft's configuration before T.O..

Edited May 14, 20233 yr by edpatino

I can't offer a very detailed answer but here's an article describing a failure resulting in an in-flight emergency caused by the TLU. It gives a pretty good description of the system. I've not had a problem on MSFS as far as TO Config test is concerned but the TLU Lo Speed message is green which tells me it's a normal function at a given airspeed. If I'm not mistaken (and I am quite often) a given message would illuminate red if an imminent danger is present or amber as a caution for an impending or possible failure. In other words, I'd say it's normal other than your TO Config light. Flaps, trim, open crew doors and parking brakes set would be among the conditions that would trigger the config warning.

ATR 72 Rudder Travel Limitation Unit Incident: Latent Potential for Misassembly Meets Commercial Pressure - Aerossurance

 

I was wondering this myself, and I think I found the answer. When the aircraft is below 185 KIAS it shows TLU LO SPEED and the rudder has a wider range. Light should go out when you pass 185 KIAS and rudder range decreases.

Hi there,

The TLU LO SPEED should be there, atleast it is in real life.

It will be illuminated when your speed is below 185kts.

 

Check on the overhead panel that it is in the AUTO position (should be somewhere up on the left side, over the captain)