Fast-Slow speed indicator in B732

[md-100]

Condition:

A/c : B732
Autopilot : Sperry 177

Situation:
A/T : Disengaged
A/P : Disengaged
F/D : On
APP Mode : Capture (LOC & GS)
MCP Speed : Selected Target Speed

Question:
How does the FAST-SLOW SPEED INDICATOR work?

Thanx

I forgot..... Does anyone know where I can find a Sperry 177 manual or operation in the net?

thanx again

[Charles Darwin]

I would presume the F/S indicator simply uses the current speed according to ASI versus the commanded speed on the MCP. If you are flying faster than commanded MCP speed, the F/S indicator shows "fast". Actually very simple.
Rgds,
CD.:8

[md-100]

well, not at all, because in the situation i stated, the F/S indicator, i guess, it shows you thrust demand.

[A-FLOOR]

It does.

What it shows it a reference line and a moving indicator. If the indicator indicates "Slow" (IAS falls below MCP speed) you should increase thrust to keep the indicator on the reference line. Vice versa when you're going to fast... indicator is above reference line, so retard throttles a bit to bring it back. It's nothing more than a comparator if you insist on being technical.

It's probably the simplest instrument in any flightdeck, apart from maybe the whiskey compass ;)

This is it, F/S bar with the little yellow indicator slightly to the left of the ADI:
http://www.airliners.net/open.file/559521/L/

In this case the IAS/Mach matches the one set on the MCP, so the bar is centered. Every dot above or below the reference line accounts for 10KIAS, if I recall correctly.

[Old Smokey]

md-100,

For the Sperry 177 (and other Speed Command systems of the B737-200 era), it has nothing to do with selected speed.

In the APP (Approach) mode, it references Angle of Attack, seeking to provide the Angle of Attack equivalent to 1.3 X Vs.

In this mode, you could set 300 KIAS on the speed bug (a bit fool-hardy on approach), and if you were flying at 250 KIAS, i.e. 50 knots below the MCP speed, it would still show 'FAST'.

Regards,

Old Smokey