[Flying Scotsman]

I'm a long way from avionics and panel layout stuff (a loooooooooong way LOL!), but still kind of starting to think of wiring and other stuff. So here's a question that I've been pondering this evening, when it's too late to work in the shop...

What are people doing for annunciator lights or what we'd call "Caution and Warning" lights? Not the wiring per se, but what do you want to see or not see?

My preference is for a "quiet, dark" cockpit for normal operations...lights on or noises indicate a condition to be handled. Would you use a Master Caution and Warning Light system? Or keep it to the bare minimum...which would be?...oil pressure/vacuum (if you have it)/alternator failure/whatever? Color schemes? (Red - critical, Yellow - serious, etc.)?

I wouldn't want to replicate some ginormous thing like a G-V or Citation or something...but something nicely designed and systematic in nature seems desireable.

Anyway, just relaxing at home, surfing the web and thinking waaaaay ahead (and doing a little dreaming ).

 

[Rick6a]

Here is a great link for those who wish to build an annunciating system from scratch:
http://www.vansairforce.com/community/showthread.php?t=5197


For those of us less ambitious, you can cluster two or more off-the-shelf "Legend Lights" into any grouping that pleases you. Use your word program to generate custom labels too.

 

[f1rocket]

Steve,

I like to have warning lights for critical stuff but prefer it dark otherwise. I wired a warning light panel for the top/center part of the instrument panel. They are small blinking diodes for the following:

- Low Oil Pressure (Red)
- Electronics Ignition On (Red) - Only comes on if I leave the ignition switch on and there's no oil pressure because I have this wired to the battery.
- Starter Engaged (Yellow)
- EFIS Warning (Red)
- Alternator Inop (Red)
- Switch Fuel Tanks (Yellow)

 

[Ironflight]

I'm also a "dark cockpit" guy - if a light is on, there is something that I still need to do. I have a master Alarm driven by the EIS which tells me if there is anything out of limits - that's RED. I also have an "oil Pressure" light driven directly by a switch on the oil pressure manifold - that is also RED. Those are the only two "warning" lights, since I have full message (caution and advisory) capability on the EFIS screen right in front of me.

The rest of my lights are "Hey Dummy" lights to remind me that I am out of my normal cruise configuration. One BLUE light each for the landing and taxi lights - the indicator is on when the big lights are on. A GREEN light tells me that the fuel pump is on - reminds me to get it off once I am through with take-off or landing, Then there is a GREEN light light for the pitot heat - that one might be left on for awhile if I'm in the clouds, so "green" is "good"....but it is still not normal cruise. Finally, I have a GREEN light telling that external power is connected on the belly connector.

I love annunciator lights, and when everything is normal, they are all out. "cool" colors - everything is OK, but we are out of normal configuration. Anything warm or hot needs attention! And EFIS messages have made almost all the rest of the lights I've had in cockpits before obsolete.

Oh, and I am using LED's and a panel that look a lot like Ricks (above). If you search for "Annunciator" here n the forums, you'll eventually find a post or two from me on how I built it.

Paul

 

[b17fe]

I'm only using 2 ... red = low oil pressure & green just above fuel pump switch on panel (so i don't forget to turn it off).

 

[N941WR]

I'm only using 1 green light just above the EFIS right in my line of sight. (So I don't forget to turn it off or on prior to takeoff.)

The EMS puts out all the other warnings, along with an audio tone, so no need for a bank of lights.

 

[Frank Smidler]

3 warning lights top center of pilots view

I have three lights they are:

1. Red - low oil pressure driven off of the oil pressure switch for the Hobbs. At shut down if it is on it indicates master is still on so I don't wear down the battery.

2. Green - Alternator warning. Plane power alternator harness wired for this.

3. Red - GRT EIS warning light.

Simple mind, simple panel.

 

[rvmills]

I put together a simple annunciator panel after reviewing Paul and Rick's work (thanks guys!). I used some LED lights from MPJA, after seeing some of Pete H's posts (thanks, and aint this site great!).

Ended up putting them in a small array over my D100 to match the size/form of the Monroy Traffic Watch over the D10A.

I went with yellow for the alternator lite, green for landing lite on, blue for fuel pump on, and red for low oil p. I concur with Paul and others on the dark panel concept. I wanted all yellow and red lights off for normal ops, and the "cool" colors (blue and green) are on for TO/LNDG, but are "hey you, ya need to do something" lights in normal flight. I chose blue for the fuel pump because at work the fuel lights are blue (X-feed, etc).

I sorta geeked out and used matching colored toggle switch covers for the corresponding switches.

Currently the Alt off (yellow light) is a really an Alt switch light...comes on when the switch is off...another "hey you". Would really prefer to rewire it to come on when either the switch is off or when it is on, but volts are low. However, the Monroy flashes a warning and gives a voice warning if bus voltage drops low, so I'm happy with it for now.

I also installed a bight/dim/test switch for night ops, and used a zener diode to lower the intensity of the lights in dim. Had some help from an avionics guy on that one.

If I replace the VM-1000 with a Dynon EMS to go with the EFIS's, I may replace the Alt light with a master caution (from the EMS/EFIS) and the Oil P lite with a canopy unlocked lite...concur with Bill, the EFIS warnings provide a lot of redundancy.

Fun DIY project though. Here's a pic:

Cheers,
Bob

 

[David-aviator]

Here is a great link for those who wish to build an annunciating system from scratch:
http://www.vansairforce.com/community/showthread.php?t=5197


For those of us less ambitious, you can cluster two or more off-the-shelf "Legend Lights" into any grouping that pleases you. Use your word program to generate custom labels too.

Those lights are cute, Rick, I've used them but they are all but impossible to see in bright sun light.

I am back to one big fat red warning light from EIS and another from the oil pressure sender. I can see them.

dd

 

[roee]

Battery discharging

Seems like a common annunciator that people include is alternator INOP or alternator offline, something to that effect. Or in some airplanes a low voltage annunciator also serves a similar purpose. All makes sense, but I'm planning on a slight twist that I think is better yet than all these options.

Instead of alternator state or bus voltage, detect/annunciate that the battery is discharging, i.e. that current is flowing out of rather than into the battery. So when the alternator is offline or failed, this annunciator will be on, same as before, because the battery will be carrying the load. But now the annunciator will also be on any time the alternator is online but unable to supply enough juice for the full bus load. This could occur due to any of several reasons: 1. a partially failed alternator or regulator (I've been there before), 2. reduced alternator output at low engine RPM (which is normal) with too many loads switched on, or 3. abnormal excessive bus load due to a fault in an accessory or elsewhere in the electrical system.

The key point is, what you really want to know is that your battery is discharging and that you need to rectify that situation, whether your alternator is alive, dead, or anything inbetween.

 

[Mike S]

Steve, one thing to consider is what make of EFIS---you are going to use glass, I presume----you choose.

The GRT provides a big red warning light that will let you know if something is wrong, and the EFIS will tell you what is wrong, and why. AFS has audio tattletale that lets you know if something is wrong----"Check EGT" in your ear. Other brands may have similar capabilities.

I think this is a good time to start thinking along these lines, but you say it is going to be a long time before you actually start the panel, and at the rate the industry is advancing, I would not be too concerned with the exact setup at this time.

I would suggest you start developing some design parameters, but wait for the actual details until you are ready to purchase the units.

In addition to the big red light, I have two green test lights for door closure, yellow lights for each alternator-----mainly because the output for the light was provided in the regulator, a yellow light for the ignition if it goes into failure/mag backup mode, and one to indicate when I have the battery cross tie contactor engaged.

 

[mburch]

Instead of alternator state or bus voltage, detect/annunciate that the battery is discharging, i.e. that current is flowing out of rather than into the battery. So when the alternator is offline or failed, this annunciator will be on, same as before, because the battery will be carrying the load. But now the annunciator will also be on any time the alternator is online but unable to supply enough juice for the full bus load.

Can't you determine that just by looking at voltage? Speaking practically, a battery will only charge if it's terminal voltage is above some value (~13V). If your battery voltage is less than that, then either the alternator is overloaded or is otherwise inop. What am I missing?

mcb

 

[Flying Scotsman]

Steve, one thing to consider is what make of EFIS---you are going to use glass, I presume----you choose.

The GRT provides a big red warning light that will let you know if something is wrong, and the EFIS will tell you what is wrong, and why. AFS has audio tattletale that lets you know if something is wrong----"Check EGT" in your ear. Other brands may have similar capabilities.

I think this is a good time to start thinking along these lines, but you say it is going to be a long time before you actually start the panel, and at the rate the industry is advancing, I would not be too concerned with the exact setup at this time.

I would suggest you start developing some design parameters, but wait for the actual details until you are ready to purchase the units.

In addition to the big red light, I have two green test lights for door closure, yellow lights for each alternator-----mainly because the output for the light was provided in the regulator, a yellow light for the ignition if it goes into failure/mag backup mode, and one to indicate when I have the battery cross tie contactor engaged.

Yep, going glass...been looking at the Dynon units like the D180, but you're right...equivalent capability seems to be the case for others. This is all really good info and has given me some ideas. Like I said, it's a fun topic for the moment while I slog through building the airframe and save for that engine .

 

[Ironflight]

Those lights are cute, Rick, I've used them but they are all but impossible to see in bright sun light.

I am back to one big fat red warning light from EIS and another from the oil pressure sender. I can see them.

dd

I didn't buy mine from ACS David - I got them at a local Electronics Parts place - so they may be different inside (but they sure look the same....haven't had any trouble with them in bright sunshine in the -8, and have a pretty good pot in the system to dim them at night. There might very well be different brightness LED's in the same case, and I got lucky.

Paul

 

[roee]

Low voltage as discharge indicator: sorta, kinda...

Can't you determine that just by looking at voltage? Speaking practically, a battery will only charge if it's terminal voltage is above some value (~13V). If your battery voltage is less than that, then either the alternator is overloaded or is otherwise inop. What am I missing?

mcb

Using voltage for this purpose is valid, but has its limitations. It's only an indirect and imprecise way of determining battery current direction. In gross situations like a complete alternator failure it would generally be good enough, but not in more subtle situations. Yes, if your bus voltage is 14V, then you're probably charging. If 12V, then you're probably discharging. But the actual threshold in between is a function of many factors (battery type, battery condition, battery charge state, temperature, etc.), is not a fixed number, and cannot be accurately predetermined.

If for example your bus load is 45 A, your alternator is putting out only 40 A while your battery is supplying the other 5A, and your bus voltage is sitting right around the threshold region, it isn't so obvious which way the current is flowing by only looking at bus voltage. If the annunciator's voltage threshold is lower than the actual discharge threshold under your current conditions, then you will only get an indication eventually, after your battery has already discharged sufficiently and the voltage drops below threshold. But by then you have less than a fully charged battery as your reserve, and you don't know by how much. Not a good position to be in. Alternatively, if you set up your system more conservatively and the annunciator's voltage threshold is always higher than the actual discharge threshold, then you will get false indications when there really is no problem.

Whereas with a direct measurement of battery current direction, you would become aware of the problem accurately under all conditions, and immediately, while you still have a fully charged battery.

 

[uk_figs]

simple system with dynon

I used the Vans circuit for the low oil pressure/hobbs trigger with the light top center of the pilots panel, with the Dynon you can add a switched ground into the same circuit that is triggered by any alarm so the single light warns of master on, low oil pressure and any dynon alarm in flight and master on warning on shutdown. Simple but like a master caution light. I also added a small red LED light in the lower left of the engine control sub panel for the boost pump circuit as I kept forgetting to turn it off after takeoff.

 

[MCA]

Using voltage for this purpose is valid, but has its limitations. It's only an indirect and imprecise way of determining battery current direction. In gross situations like a complete alternator failure it would generally be good enough, but not in more subtle situations. Yes, if your bus voltage is 14V, then you're probably charging. If 12V, then you're probably discharging. But the actual threshold in between is a function of many factors (battery type, battery condition, battery charge state, temperature, etc.), is not a fixed number, and cannot be accurately predetermined.

Roee, I agree, sort of. Voltage alone, and good system design, can solve this problem without adding more parts on the plane. I agree voltage can measure the gross situations. But if you design your electrical system properly you know what the max current draw is for all your electrical devices, and the alternator should be sized accordingly.

In other words, you should not be in a position to draw 45 amps with a 40 amp alternator. That means you (ok, not you specifically, but any of us builders) goofed somewhere along the way in system design. Same with running on a backup alternator - you should know what your load shed scenario looks like before it happens. If you are in this "intermediate zone" then you will see the voltage decay slowly. Not as quickly as with a meter, but it is something you should determine during initial testing. Either the alternator can handle the load or it can't. And there should always be some margin built in for changing conditions.

Ideally, you'd want a system that shows voltage and total current draw. But if you don't have that some work up front with system design and testing can make this work with minimal parts. Ultimately though, you should go with what you are comfortable using. I don't any of the solutions discussed are unsafe. Just food for thought.

 

[roee]

Roee, I agree, sort of. Voltage alone, and good system design, can solve this problem without adding more parts on the plane. I agree voltage can measure the gross situations. But if you design your electrical system properly you know what the max current draw is for all your electrical devices, and the alternator should be sized accordingly.

In other words, you should not be in a position to draw 45 amps with a 40 amp alternator. That means you (ok, not you specifically, but any of us builders) goofed somewhere along the way in system design. Same with running on a backup alternator - you should know what your load shed scenario looks like before it happens. If you are in this "intermediate zone" then you will see the voltage decay slowly. Not as quickly as with a meter, but it is something you should determine during initial testing. Either the alternator can handle the load or it can't. And there should always be some margin built in for changing conditions.

Ideally, you'd want a system that shows voltage and total current draw. But if you don't have that some work up front with system design and testing can make this work with minimal parts. Ultimately though, you should go with what you are comfortable using. I don't any of the solutions discussed are unsafe. Just food for thought.

Marc, I agree with you too, sort of. I agree completely that good system design and a load budget with ample margin for all operating configurations is essential. But even so, in the approach you describe for detecting battery discharge using voltage measurement there are still implicit assumptions that may not always hold true. For example, the assumption that a "40A alternator" can always put out 40A (or whatever its specified nominal current capacity may be). Even a well functioning alternator will have a significantly less-than-nominal current output capacity at lower RPM's. It is usually impractical to make your worst case load current work at your worst case alternator output (say, at 600 RPM). And a damaged alternator may have a significantly less-than-nominal current output capacity at any RPM, which is indeterminate and can't be accounted for in the load budget. Another implicit assumption is the accuracy of the budgeted load currents. As you said, one could and should verify the current drawn by each load in testing. But that still only verifies them under nominal operating conditions. There may be fault conditions under which a load may exceed its nominal current draw. Some such conditions you may be able to anticipate and budget for, others not. So in this respect, the advantage of the approach I described is that it is a direct measurement of current, and therefore removes these assumptions about alternator and load currents from the equation.

Now, to be clear, I'm not at all trying to suggest that one approach is "safe" and the other is "unsafe". That would be a subjective and mostly meaningless judgment anyway. I'm just offering what I think is an improvement over the presently adopted approach, an improvement which may help make things "safer". And not necessarily with more parts, just different parts. In any case, absolutely, we each should make this judgment for ourselves, and go with what we're each most comfortable with. I'm glad we have that freedom. And I always enjoy a good debate.

 

[Bob Axsom]

Two yellow lights

1 - Battery discharging/ alternator not supplying power
2 - LASAR ignition failure (operating in standard magneto mode)

Bob Axsom