DC9: One blue light remains lit on the panel

[thrillsandchills]

I'm so close to getting it right. The one light that's illuminated is the one about how the rudder has free range of travel.
So, how do you extinguish the blue light re: free range of rudder travel? Then I'll be good to go.

Thanks.

Thrills and Chills

[aerofoto - HJG Admin]

Uning the HJG/HILMERBY/CARTY DC9 panel series .... that particular OH panel annunciator lamp does, sometimes, activate and remain 'ON" .... and other times it won't (it could just be the result of activating variaous panel/systems switches in a certain specific order .... I'm not sure) .... BUT .... in cases where it "does" iluminate then its doing so won't adversely affect your flight .... at all

In cases where it illuminates .... prior to T/O .... then it will extinguish again, automatically, once airbourne .... and then, possibly, display once again, automatically, after landing.

Prior to T/O .... be sure that "all of the necessary panel switches/systems" are activated "correctly" and strictly in accordance with the pre-flight/panel configuration drill .... stated within "SECTION 2" of my "DC9 PANELS INSTALATION & HANDLING NOTES" posting (the online/forum based manual for the HJG DC9 simulations) .... and in particular .... using the CP panel check that the yellow Rudder Power lever (located to the right of the Speedbrake Lever and which is marked with a black circle with a white letter "R") is set to its "PWR" position .... prior to T/O

That should be sufficient to see you right .... and without any problems at all

Mark C
AKL/NZ

[thrillsandchills]

Thanks so much for the reply; That's good news that I went through the panel/system configuration steps successfully.

Thanks.

Thrills and Chills.

[acourt]

Thrills and Chills,

Mark has it right. The blue light shouldn't really affect your flying, as I'm not sure the related system is modeled. Here's what's happening (engage techno-babble)...

An airplane must have sufficient rudder travel to provide adequate controlability at low speeds.  But that same amount of rudder at high speeds would likely rip the tail off the airplane.  To prevent ham-fisted pilots from self-destructing their airplanes, designers came up with a system to prevent it: the rudder limiter.

The DC-9 (and other airplanes) is equipped with a rudder limiter. The system does just what it's name says: limits the amount of rudder input available to the pilot. The level of rudder restriction is directly related to airspeed, i.e. high airspeed = high restriction, low airspeed = low/no restriction.

On the Nine (and 717...it's essentially the same system), rudder restriction begins at about 153 KIAS. At 177 KIAS, rudder travel is restricted to 17 degrees. Maximum restriction occurs at about 300 KIAS, and leaves the pilot with only 2 1/2 degrees of rudder travel. These numbers aren't actually based on indicated airspeed, as the system has it's own speed sensing system. (Ever wonder what the pitot tube sticking out the front of the vertical stabilizer is for? Ah ha!)

So...the illumination of the blue RUDDER TRAVEL UNRESTRICTED light means just that: the rudder is operating without restriction. Any time you're below appoximately 153 KIAS, the blue light should be on, which means it should be on for every takeoff. The light should come back on again when slowing through about 153 KIAS during approach and landing. It it's not on at those times, then your rudder is improperly restricted, which means you won't have full rudder available to cope with crosswinds or an engine failure on takeoff, landing, or go around. An improperly restricted rudder essentially increases Vmc.

There is a limiting function based on flap extension in the real airplane, but it definitely is not modeled here.

There is no switch in the cockpit to control the rudder limiter. It is a purely mechanical-pneumatic system that operates all the time.

Also, keep in mind that rudder limiting is available whether the rudder is hydraulically powered or operating manually.

(Disengage techno-babble...)


So for the HJG model, the blue light should be on below about 153 KIAS, and must be on for takeoff.  (Whew!)

[ram1220]

Thank you so much for this very informative reply. I fly the DC9-30 quite a bit and have always wondered about this light.