Alternator Failure and Accidents due to Avionics

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rt4388

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rt4388
Two quick questions if anyone has insight.

Today, I had an alternator failure on my right engine. The ammeter showed negative 70 amps and the functioning alternator showed about positive 30. Would this net actually drain my battery? I'm guessing it could since its alternating current from the alternators. Also, I've heard you can calculate how long your electrical system will last with a dual failure by taking the amp hours on the battery and dividing by the total amps on the circuit breakers. How would a -40 charge play into this calculation?

Second, my students don't quite understand the importance of understanding how to program avionics. Any accidents/reports/articles you've read where a pilot incorrectly programmed the GPS, etc. Want to show them how deadly it can be if they don't read up on their avionics.

Thanks guys!
 
Alternator: Depends on how it failed and whether the negative charge indicated was real, or just a side effect of the type of failure. Best bet, isolate it, which most POHs call for on a twin with an alternator down, anyway. Pull the breaker.

Misprogramming: Well, the guy who programmed a Cirrus to fly straight from Colorado to somewhere in Utah and plowed directly into the only mountain in his direct flight path, probably qualifies. As does the CAP crew who plowed into the only mountain for a hundred miles in AZ.

Those are just two off the top of my head. There are plenty of accidents where the gadgetry flew people directly into terrain because they “misprogrammed” it. Or more accurately, programmed it to kill them. And the electronics obliged.

I’d have to dig some more if you want more subtle examples. Many people have stories of “what the hell is that thing doing now?” before they decided to hand fly the airplane and figure out what stupid programming made its way into “the box”.

I know of one guy who put in the wrong waypoint in a GPS on his Instrument ride and was going 180 degrees the wrong direction for a very short period of time. He thought about it, caught it, told the examiner, and fixed it, and still passed. Not sure pat examiners would. But he caught it really fast. He had a recording of the cockpit audio and it was seconds, not minutes, before he noticed his key punching mistake.
 
denverpilot said:
Alternator: Depends on how it failed and whether the negative charge indicated was real, or just a side effect of the type of failure. Best bet, isolate it, which most POHs call for on a twin with an alternator down, anyway. Pull the breaker.

Misprogramming: Well, the guy who programmed a Cirrus to fly straight from Colorado to somewhere in Utah and plowed directly into the only mountain in his direct flight path, probably qualifies. As does the CAP crew who plowed into the only mountain for a hundred miles in AZ.

Those are just two off the top of my head. There are plenty of accidents where the gadgetry flew people directly into terrain because they “misprogrammed” it. Or more accurately, programmed it to kill them. And the electronics obliged.

I’d have to dig some more if you want more subtle examples. Many people have stories of “what the hell is that thing doing now?” before they decided to hand fly the airplane and figure out what stupid programming made its way into “the box”.

I know of one guy who put in the wrong waypoint in a GPS on his Instrument ride and was going 180 degrees the wrong direction for a very short period of time. He thought about it, caught it, told the examiner, and fixed it, and still passed. Not sure pat examiners would. But he caught it really fast. He had a recording of the cockpit audio and it was seconds, not minutes, before he noticed his key punching mistake.
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Sweet. Thanks for the thoughts! Happen to know anymore details about the Cirrus or CAP incidents? I would like to dig up some aviation articles or accident case studies on those if possible.
 
Tampa executive airport was formerly called Vandenberg airport. Apparently too many pilots who intended to go to Vandenberg AFB accidentally set their sights on the East coast.

Could possibly have been due to inattentiveness when setting up the GPS :rolleyes2:
 
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rt4388 said:
Sweet. Thanks for the thoughts! Happen to know anymore details about the Cirrus or CAP incidents? I would like to dig up some aviation articles or accident case studies on those if possible.
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Well, that’s a problem with CFIT caused by tech. There’s often not enough of the avionics left or any recording features to prove what was typed into the devices.

This is the prelim on the Cirrus. What it doesn’t say is the crash occurred on nearly a straight line (in other words, “GPS Direct”) from the departure to destination airports. NTSB usually doesn’t add that sort of speculation into their reports.

https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20170916X12649

Surprisingly I couldn’t find the CAP accident report but it was a long time ago. Similar thing. Two very experienced instrument pilots took off out of PHX for somewhere and plowed straight into the only mountain in their planned route of flight.

One could also call these “flight planning” errors instead of “misprogramming” errors. But every Instrument pilot who’s survived it, has at least one story of punching in the wrong thing and then thinking the moving map depiction of where they want the airplane to be, looks wrong, and figuring it out and correcting it.

When you survive it, there’s no accident report.

When you don’t, there’s not anything but a very straight line leading into the terrain as a hint that you were following the “magenta line”.

Speaking of that, duh... that’s probably the best presentation of them all about this. Look up “Children of the Magenta Line” on YouTube.

That’s one of the first formal safety presentations most pilots became aware of about blindly following what the moving map style avionics tells you to fly. It’s been out so long it’s become a catch phrase for people blindly following a GPS / moving map course line without thinking about whether the route is actually safe.
 
Another thing to keep in mind is programming on the ground with the engine running. Just holding the brakes it’s not unheard of to start rolling while ‘heads down’. Most of us want some engine warmup time, especially on a cold day. That’s a fine time to program, just keep an eye on movement, maybe set any parking brake.

Glass avionics make Nav much easier, but nothing wrong with some ‘old school’ thought patterns mixed in. One element of aviation 101 is awareness of terrain and obstacles anywhere near planned flight.
 
I don't get the misprogramming the wrong identifier. Even on the now ancient 430, when you dial in the ID it gives you the name and location of the facility right there on the page you're dialing it in on.
 
EdFred said:
I don't get the misprogramming the wrong identifier. Even on the now ancient 430, when you dial in the ID it gives you the name and location of the facility right there on the page you're dialing it in on.
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Well it gives the name but that doesn’t mean someone is looking. I once had a CFII ‘splain to me that I should be able to accomplish tasks by counting clicks...
 
rt4388 said:
Also, I've heard you can calculate how long your electrical system will last with a dual failure by taking the amp hours on the battery and dividing by the total amps on the circuit breakers. How would a -40 charge play into this calculation?
Click to expand...

FYI, adding up the numbers on the circuit breakers will not tell you much about actual electrical load. Breakers are sized to the wires attached to them. Wire is sized by the actual load, loss, temperature rise etc, sometimes its just what the installation documents show.

For example, all of my comm radios are on 10 amp breakers as required by STC documents and hooked to 18 gauge wires, one is a GTN650. Typical GTN COMM consumption (@ 14 volts) is 0.6 amps and maximum 4.02.

Other example, a lot of folks have replaced lights with LED versions which can use less than half the power but the breakers were never changed, which mechanically there is nothing wrong with it, just the breaker is a lot bigger than the load.
 
Clark1961 said:
Well it gives the name but that doesn’t mean someone is looking. I once had a CFII ‘splain to me that I should be able to accomplish tasks by counting clicks...
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I have to look. I can't ever remember if the A-Z comes before or after 0-9, and every time I program I seem to turn the wrong direction to start. Of course I could solve that issue by never flying to any locations with a number in the ID - but then I could never get home.
 
Why count up the amps on the circuit breakers (which are maximum ratings anyway, not actual use) when the ammeters tell you the number of amps you're using?
 
Clip4 said:
With a suspected 70 amp discharg on one side I would be concerned about a short and fire.
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With the info given, that's like a 100 amp load he's showing. I have no idea what airplane it is but that seems really high for most piston aircraft unless it has some sort of electric air conditioner. I wonder if the meters are really showing what's happening.
 
EdFred said:
I have to look. I can't ever remember if the A-Z comes before or after 0-9, and every time I program I seem to turn the wrong direction to start. Of course I could solve that issue by never flying to any locations with a number in the ID - but then I could never get home.
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I have to look too. I suspect there are people who don’t always look.
 
No one ever crashed due to an avionics or electrical problem. People crash because they respond to these problems incorrectly.
 
rt4388 said:
Would this net actually drain my battery?
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Yes.

rt4388 said:
I've heard you can calculate how long your electrical system will last with a dual failure by taking the amp hours on the battery and dividing by the total amps on the circuit breakers. How would a -40 charge play into this calculation?
Click to expand...
You can calculate duration but using the actual load and not the CB values as mentioned above. Every battery spec list the Amp Hours (AH) which is the duration of available power for a 1A load over 1 hour. However, these bench ratings and can be greatly off depending on the condition of your electrical system and battery. Most GA aircraft batteries have an AH value between 8AH to 30AH. If your battery is mid-range of 20AH then a 40A load would give you 30 minutes power in a perfect world example.
 
Bell206 said:
Yes.


You can calculate duration but using the actual load and not the CB values as mentioned above. Every battery spec list the Amp Hours (AH) which is the duration of available power for a 1A load over 1 hour. However, these bench ratings and can be greatly off depending on the condition of your electrical system and battery. Most GA aircraft batteries have an AH value between 8AH to 30AH. If your battery is mid-range of 20AH then a 40A load would give you 30 minutes power in a perfect world example.
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The circuit breaker to amp hour of the battery is just a good off the cuff measurement, and if anything it's overly conservative which is good if you're on a flight that's depending on electronic avionics.
 
There was a report (may be the one someone mentioned earlier) where a guy read the L 51 (which is the field is lighted and the runway is 5100 feet long) as the identifier for his destination airport and put it in his GPS and went off into the wrong direction totally and hit a mountain.
 
James331 said:
circuit breaker to amp hour of the battery is just a good off the cuff measurement
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A better guess would be what the ammeter is reading not CB labels. A 30A landing light CB rating and three misc 10A CBs would only give you 3 minutes vs. 30 mins calculated at a 40A ammeter load on a 20AH battery. But to each their own.
 
Bell206 said:
A better guess would be what the ammeter is reading not CB labels. A 30A landing light CB rating and three misc 10A CBs would only give you 3 minutes vs. 30 mins calculated at a 40A ammeter load on a 20AH battery. But to each their own.
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Depends, the amp readout on a PC12, sure, the jumpy little ammeters Ive seen on most 172s and PA28s, nah.

Also if you lost your alternator and you're in cruise with your landing light on, I dont have a good deal of faith that you have the common sense to pull off an abnormal situation, god forbid a emergency.
 
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flyingron said:
There was a report (may be the one someone mentioned earlier) where a guy read the L 51 (which is the field is lighted and the runway is 5100 feet long) as the identifier for his destination airport and put it in his GPS and went off into the wrong direction totally and hit a mountain.
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That would be this guy:

I have no words...

Keep in mind, though:

"According to records obtained from the pilot's Veteran's Administration Hospital, in January 2013, he was documented as having multiple chronic medical conditions including spinal stenosis, hypothyroidism, depressive disorder, posttraumatic stress disorder, panic disorder, gastroesophageal reflux disease, esophageal stricture, chronic neck pain, paraplegia, peptic ulcer disease, type 2 diabetes, and emphysema."
 
asicer said:
That would be this guy:

I have no words...

Keep in mind, though:

"According to records obtained from the pilot's Veteran's Administration Hospital, in January 2013, he was documented as having multiple chronic medical conditions including spinal stenosis, hypothyroidism, depressive disorder, posttraumatic stress disorder, panic disorder, gastroesophageal reflux disease, esophageal stricture, chronic neck pain, paraplegia, peptic ulcer disease, type 2 diabetes, and emphysema."
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Uhh, so how was he able to fly a plane for so long with all of that, does the VA get paid per diagnosis?
 
flyingron said:
There was a report (may be the one someone mentioned earlier) where a guy read the L 51 (which is the field is lighted and the runway is 5100 feet long) as the identifier for his destination airport and put it in his GPS and went off into the wrong direction totally and hit a mountain.
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Looking at his compass or DG might have rectified the problem.
 
steingar said:
Looking at his compass or DG might have rectified the problem.
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Apparently he was too used to navigating by pilotage. His logbook had these entries in it:

“Flew over parade 10 feet off ground made six passes.”

“Landed on Rt 66 4 July Parade. With Mayor.”

“Flew to the barn landed on Rt. 66 for auto show.”
 
asicer said:
Apparently he was too used to navigating by pilotage. His logbook had these entries in it:

“Flew over parade 10 feet off ground made six passes.”

“Landed on Rt 66 4 July Parade. With Mayor.”

“Flew to the barn landed on Rt. 66 for auto show.”
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Well, we certainly know where he got his kicks.
 
Lachlan said:
Well, we certainly know where he got his kicks.
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A-80847-1459259806-2484.jpeg.jpg

Knows what you did there.
 
bnt83 said:
FYI, adding up the numbers on the circuit breakers will not tell you much about actual electrical load. Breakers are sized to the wires attached to them. Wire is sized by the actual load, loss, temperature rise etc, sometimes its just what the installation documents show.

For example, all of my comm radios are on 10 amp breakers as required by STC documents and hooked to 18 gauge wires, one is a GTN650. Typical GTN COMM consumption (@ 14 volts) is 0.6 amps and maximum 4.02.

Other example, a lot of folks have replaced lights with LED versions which can use less than half the power but the breakers were never changed, which mechanically there is nothing wrong with it, just the breaker is a lot bigger than the load.
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Sweet! This makes a lot more sense. Always thought that sounded a little fishy because the circuit breakers add up to quite a bit.
 
denverpilot said:
...Surprisingly I couldn’t find the CAP accident report but it was a long time ago. Similar thing. Two very experienced instrument pilots took off out of PHX for somewhere and plowed straight into the only mountain in their planned route of flight...
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Not certain, but perhaps this is the CFIT accident you were trying to find? Not all that long ago. But out of Vegas, not PHX. A G1000 equipped turbo-Skylane (with terrain proximity). Clear night, no moon.


https://www.ntsb.gov/_layouts/ntsb....ev_id=20071121X01832&ntsbno=SEA08FA023&akey=1
 
rt4388 said:
Sweet! This makes a lot more sense. Always thought that sounded a little fishy because the circuit breakers add up to quite a bit.
Click to expand...

Adding up the amperage capacities of circuit breakers on a bus has no correlation whatsoever with the system electrical load. Breakers are sized to protect the wiring of the circuit from overload, not the connected devices. The actual load on the individual circuits must be calculated by adding the amperage draw of the devices attached to the circuit.

As mentioned above, a 10 amp breaker protecting a circuit powering a couple of radios might have a current draw of one or two amps. The landing light circuit might have a 20 amp breaker while the light itself draws 12 or 13 amps.

The ammeter readings you experienced indicate something is not right, and that level of current could melt wires and start a fire if the stars line up against you.

This isn't meant as an insult, but it's obvious you aren't knowledgeable about things electric. Schedule an appointment with your mechanic.
 
3393RP said:
Adding up the amperage capacities of circuit breakers on a bus has no correlation whatsoever with the system electrical load. Breakers are sized to protect the wiring of the circuit from overload, not the connected devices. The actual load on the individual circuits must be calculated by adding the amperage draw of the devices attached to the circuit.

As mentioned above, a 10 amp breaker protecting a circuit powering a couple of radios might have a current draw of one or two amps. The landing light circuit might have a 20 amp breaker while the light itself draws 12 or 13 amps.

The ammeter readings you experienced indicate something is not right, and that level of current could melt wires and start a fire if the stars line up against you.

This isn't meant as an insult, but it's obvious you aren't knowledgeable about things electric. Schedule an appointment with your mechanic.
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Is it a common point of confusion with people when they loose their charging source, whether or not they should run high output lights in cruise?

Because when it comes to the breaker thing people always bring that up
 
James331 said:
Is it a common point of confusion with people when they loose their charging source, whether or not they should run high output lights in cruise?
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Funny you mention that. The Archer II and the Cirrus I usually fly where both unavailable recently so took another plane, a new Archer III.. well about 30 minutes into cruise the alternator annunciator light came on.. mind you, as I was already in cruise and it was day VFR there was very little load on the system.. only systems on were avionics (two 430, Garmin xponder) and the beacon. No fan, A/C, landing lights, autopilot (which actually was on but I shut it off), pitot, fuel pump, etc.

Later, when I was telling people about it the first question everyone asked was "did you turn off the landing lights?" <- it struck me as a little peculiar. Perhaps there are some people that were taught to leave everything on? My airspace is pretty busy.. I safetied for someone a few weeks ago and noticed that the fuel pump, pitot heat, landing lights, pretty much every switch was left on the whole flight. Again, day VFR, +10*C outside. But even if you are just doing a short 75 mile XC I think it builds good discipline to do at least a basic climb / cruise / descent checklist
 
Tantalum said:
Funny you mention that. The Archer II and the Cirrus I usually fly where both unavailable recently so took another plane, a new Archer III.. well about 30 minutes into cruise the alternator annunciator light came on.. mind you, as I was already in cruise and it was day VFR there was very little load on the system.. only systems on were avionics (two 430, Garmin xponder) and the beacon. No fan, A/C, landing lights, autopilot (which actually was on but I shut it off), pitot, fuel pump, etc.

Later, when I was telling people about it the first question everyone asked was "did you turn off the landing lights?" <- it struck me as a little peculiar. Perhaps there are some people that were taught to leave everything on? My airspace is pretty busy.. I safetied for someone a few weeks ago and noticed that the fuel pump, pitot heat, landing lights, pretty much every switch was left on the whole flight. Again, day VFR, +10*C outside. But even if you are just doing a short 75 mile XC I think it builds good discipline to do at least a basic climb / cruise / descent checklist
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It is possible in just about any airplane to overload the charging system, in other words the battery is making up for demand. Its most likely to occur at night, when moving flaps/gear.
 
rt4388 said:
Second, my students don't quite understand the importance of understanding how to program avionics.
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I bet this happens much more often than we think, it just doesn't usually result in an accident and hence a report. Personally, it is surprising to me how limited most people's understanding of these systems are. Funny, because instruction focuses so much on your primary 6 pack instruments, E6B, etc., but just glosses right over the 430 / 650, etc. G1000 training is pretty solid, but in my experience most people have a very limited understanding of the 430 / 650. Even among IFR pilots. I feel like a lot of people turn and twist knobs until they accidentally get it to do what they wanted to. Just the other day in one of our rentals I found a user added waypoint "KHMT" that was in the runup area.. I bet someone tried to enter "direct to" KHMT but instead ended up creating a user waypoint. Sigh. I deleted it.

The best way to teach that would be to, during instruction, get the student used to creating flight plans, changing them mid flight, navigating to different waypoints on the flight, and setting up some of the different aux features like timers, etc. Using the OBS mode and understanding how the AP tracks to a VOR vs CGI track and switching the CDI is also important. I've seen people follow an errant CDI thinking it was something else
 
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