Glass VSI's in airliners.

[JordanD]

I've noticed that on some older planes they will have a "glass" VSI but all of the other instruments will be the old "steam guages". I've seen this on WN 733's and in a few cockpit shots of DC-8's. Why did they choose only to install a new VSI? Might be a dumb question but I'm really curious about it.

[RJP]

Because its usually also the TCAS display.

Rgds
RJP

[JordanD]

Oops I didn't think about that. Makes sense though. Thanks for answering.

[uy707]

Because its usually also the TCAS display.

Rgds
RJP

and also probably the navigational aides. Also saw some on stage II 707s as early as 1988.

Alain

[LRJet Guy]

I haven't seen one used as a navaid, but I don't see why that's not possible.

The TCAS function on the VSI shows a distance arc from your aircraft and targets aircraft with transponders on it.

If you get a traffic advisory, the blip for that airplane turns yellow, and you get an audible voice as well. A resolution advisory turns the blip red, and an arc appears on the VSI to prompt the required descent or climb. You also get an audible voice telling what to do.

[screaming_emu]

While taking a class in CRJ systems here at school, I got to wondering why they dont use the voice of "Frau" from Austin Powers for any warnings/resolution advisories. Would certainly get your attention.

[ACman]

FedEx has glass VSI's, they can update and make glass PFD's and HSI's but that costs $4 mil to do on one 727, and that upgrade is worth more than the aircraft.