learsimmer

From the photographs I have seen, the buttons on the autopilot panel that engage the autopilot functions seem to have LEDs in them that light up when they are pushed. My question is do any of them have two colors of LED, one to show the function is armed, and a second color to show when the function is engaged. If so, which buttons and what colors?

Thanks
Nick

spannersatcx

They're not LED's they are normal filaments.

Modes are displayed on PFD.

captjns

Same illumination as the other Boeing jet autopilots... when a mode is engaged, the light within the mode switch illuminates. Earlier models I've flown have two little "dot" lights within the switch. Later models have the single thin bar light accross the mode switch.

FCS Explorer

what would be the use of "arming" auto pilot? either it's on or off.

ChristiaanJ

You're right in that you wouldn't "arm" the autopilot as such.
But with the autopilot engaged, you can arm certain modes, which won't engage until the engage conditions are met.
As an example, to capture a VOR radial, you would arm VOR mode, then fly towards the radial in HDG mode. At the right moment, VOR mode will engage and start the turn towards the radial, and the HDG mode disengages.

Manual Reversion

744 doesn't have VOR mode

ChristiaanJ

LOL .....
Reminds me of the time we spent trying to get VOR mode to work acceptably on Concorde, only to discover afterwards most people didn't use it....
So they finally gave up on it, I see !
I should have used one of the other "acquire" or "capture" modes (GS, LOC, ALT) as an example.

learsimmer

Sorry to be pedantic, but I want to be quite clear about the operation of these buttons. When you write "when a mode is engaged" do you refer to an armed mode becoming active, or do you refer to pressing the button?

What color(s) do the buttons display?

Nick

learsimmer

Thanks - the pictures have insufficient resolution for me to tell that they are filament bulbs rather than LEDs.

Am I right in thinking that on pressing a button to switch on a mode, the button lights up (what color?), the PFD displays a mnemonic to indicate that the mode is either armed or engaged - it's a Rockwell Collins Pro Line PFD, isn't it? - and the light in the button remains on (same color) until the button is pressed again to disengage/disarm the mode, or until another incompatible mode is selected/engaged. If the mode is initially armed, the indication that it is engaged is announced on the PFD.

I am familiar with the Collins Pro Line 4 annunciation of autopilot modes in the Learjet.

Thanks to everyone for helping me out.

Nick

ChristiaanJ

Nothing pedantic about that to me.
My description is valid for Concorde, but I don't think the basic principle has changed at all since.
Yes.No.
Use glide slope as an example.
Imagine yourself on centerline during the approach, ALT HOLD mode at 3000 ft, but still far enough out to be well under the glideslope.
ALT HOLD engaged and illuminated.
Press the GLIDE SLOPE button.
The G/S mode is now "armed" or "primed". The button does not illuminate, but the "prime" light under it lights up.
When the AFCS detects you're at the right point, G/S mode engages automatically, takes over control and eases you onto the glideslope.
At this point the "prime" light goes out and the GLIDE SLOPE button itself illuminates, indicating the mode is now engaged and controlling the aircraft.
The ALT HOLD mode disengages at the same time, and the ALT HOLD light goes out.
For more recent aircraft, you'll have to ask somebody else....
On Concorde the buttons themselves are white, with black letters.
The "prime" light is a triangle under the button, but not sure of the colour (it's over 30 years...).

spannersatcx

If you have a look at this pic you will see that the Left A/P is in CMD and is indicated by white switch light illuminated by normal filaments (bulbs).

This is from a flt sim but pretty accurate I think

Oldy

The switch lights have two filaments each. I have seen many times only half of a white bar showing, left or right half. From the above picture you can see LNAV and VNAV and a SPEED mode engaged by looking at the three green symbols at the top of the Primary Flying Display. This is the only real way to see which modes are active in the autopilot system. The lights in the switches themselves are relatively unimportant and could be totally unserviceable without affecting the operation at all. Of more concern in the above picture is the amber caution warning at the top of the centre screen. This would be the focus of my attention but the picture resolution does not enable me to comment further.

If a switch light is pressed and the mode is just armed instead of active, as in the case of the Glide Slope Capture mentioned above, then the symbol/mnemonic on the PFD will show in amber rather than green, but the corresponding switch light will still show white. The switch lights are only on (armed or active) or off (inactive).

ChristiaanJ

I see my post was a "blast from the past".

Question: how are "armed" or "primed" modes shown on the PFDs?

FCS Explorer

active modes for roll, pitch and thrust are green in the mode announciator (MDA) in the top line of the PFD. first ten secs after activation in a green box. armed modes show in small white letter below the respective active mode.

best example: on ILS intercept heading, APP button pressed:
HDG SEL in green, VORLOC in white below
ALT HOLD in green, G/S in white below

UL975

As previously mentioned the ONLY way to tell which modes are engaged or armed is to look at the PFD. The lights on the mode buttons tell lies! Infact one major European airline removes the bulbs/filaments for exactly this reason.
The only thing that the lights tell you is if a mode can be deselected/unarmed/turned-off or however you want to think about it.

ChristiaanJ

Thanks both!
Perfectly clear for me.

learsimmer

Why would they do that if they're working off the same data that feeds the PFD?

Which aircraft have lights on the mode buttons that change color?

Nick

learsimmer

Has anyone seen a button like this in a real aircraft?




Nick

parabellum

Bit of a guess here as I'm rusty now but I would say the amber caution message is something like 'Fuel Config' as I see that the stab tank is feeding to the Centre Wing Tank but the engines are being fed from Main wing tanks when, in this config, I'd be expecting the CWT to still be feeding all four? (Unless it says that the clock has stopped?!).
Spanners will know!
Learsimmer never seen that presentation on a Boeing, 737, 747, 757, 767.

Terrey

Also 747-400s do not use Collins Proline Avionics. It is a 747-400 only installation. All Boeings are slightly different in their avionics and each display seems made fro that aircraft type.
I have not seen a large airliner (737 and above) with collins proline. I think they are corporate jet kit only.