What Was Wrong?

[Garavar]

I am a low time instrument rated pilot, only have a few hundred hours. Trying to figure what the issue was on my last flight and if I acted appropriately.

I was flying from Orlando to Fort Lauderdale in a rented DA-40 (G1000). Shortly after departure I noticed the voltage started to drop. I was losing about 1.0 volts every 8-9 minutes. Curiously though the Amps showed a positive charge. I ran through the "Low Voltage" check list items but it didn't fix the problem. The volts continued to drop.

I calculated that if I continued my trip I would arrive at airport with about 18 volts left. But at the same time I was thinking I don't know many total volts I need. (The whole thing could go pitch black at 20 for all I knew). I also realized then that I am not as familiar with electrical equipment as I thought. I started thinking what is volts/amps etc. What matters ahhh small panic.

Since the checklist wasn't helpful I did the only thing I could think of next and that was to turn off all non essential equipment/lights and search for an airport.

I called my instructor see if he could provide any input (Thanks Bluetooth A20) and he said that it was a non-issue and I would be fine to fly home. I trusted his assessment and decided to proceed.

I made it back to home airport got to parking spot and shut down. I forgot to adjust rudder peddles to put in gust lock so I tried to turn the system back on but it was totally dead all displays pitch black. I secured the plane and left.

Couple days later I called the company I rented the plane from to ask if they knew what was wrong. They told me nothing. That the plane was fine and people we flying it the next day. I tracked it on flightaware and they were right. It flew a bunch of flights after me.

So now I am confused. What the hell happened? I don't have the planes manual to look through. Were my actions correct or was it get there-itis.

 

[Eric Pauley]

Is the ammeter an alternator ammeter or a battery ammeter? I'm no DA-40 expert but depending on the setup could "positive" mean draining the battery somehow?

The first thing I'd have tried would be to cycle the alternator. Did you try this?

 

[Vance Breese]

I have no experience in that aircraft. In my aircraft if I forget to turn the alternator on I will run out of power before too long. The radio and the transponder drop off as the voltage gets low.

 

[Garavar]

Is the ammeter an alternator ammeter or a battery ammeter? I'm no DA-40 expert but depending on the setup could "positive" mean draining the battery somehow?

The first thing I'd have tried would be to cycle the alternator. Did you try this?

Yes I cycled alternator. Was part of the low voltage check list. Been baffled since this happened trying to figure it out.

 

[geezer]

First step is to download the manual for the exact model plane that you were flying. Then find out where the ammeter is located, and what it really tells you.

I do not trust schools to tell me the truth of the condition of their rental planes. They may have had a student report that your plane would not start, blamed you for leaving the master on, and charged the battery for the subsequent flights. One school I used did this repeatedly for various intermittent problems. A Piper Arrow with a microswitch that failed to give a green light intermittently for the last 2 weeks should at least have been on the squawk sheet.

Personally, I would have landed and trouble shot on the ground, as indeed, everything could go black in the air. Running through the checklists in the manual calmly idling on the ramp is much safer than in the air, and if you find that the problem is real and serious, you have avoided an expensive outcome.

Your problem in getting back home is minor, in the big picture. Their problem in getting the plane fixed and back home is their problem. Just be sure to get a mechanic at the airport where you landed to make a note in the log that he has observed the problem. If he finds that YOU have caused the problem by incorrectly preparing the plane for flight, you quietly eat that charge, run the engine until the battery is fine, and continue.

I have left a plane tied down and bought 4 full price airline tickets home when we had a problem that could not be fixed that day. Later, another airline ticket to go get the plane home. I PROBABLY could have flown home safely, but probably sits on the ground until everything is working right. Several times, I have had an inflight problem, landed, made the required repairs, and continued, including an alternator failure, and a radio the filled the cockpit with electrical smoke.

 

[Lndwarrior]

After building my own plane, including wiring, as well as flying for 25 years, I thought I knew all I needed to know about my simple panel and steam gauges. However, during flight testing I had a few anomalies in flight which raised a similar question to yours.

These anomalies weren't total failures, just things that were off a bit from where they should be.

On two occasions I could not be certain just how serious these "something isn't quite right" to the safety of flight issues. After educating myself on the issues, I realized that there were other systems in my plane that I didn't fully understand how serious it was when something was just partially abnormal.

To be clear, I have an electrically dependent aircraft, so I have a few more gauges, warning lights, and switches than most aircraft, including a triple backup electrical system (main bus, endurance bus, and a holy sh%t everything's failed switch).

I decided this was something I needed to understand, so I decided to go through every button, gauge, warning light, and circuit breaker on my panel and create a "System Emergencies" checklist.

The intent of the checklist was to document the appropriate action from each abnormal condition for everything on my panel. I wanted to clearly understand for each item the following:

Does this abnormal condition present a high risk, medium risk, or low risk. Secondly, does the abnormal condition require I land immediately, potentially off-field (High Risk), fly to the nearest airport (Medium Risk), or it's ok to fly home (Low Risk). I also recorded the correct response to the abnormal condition (ie: shut down main bus and run on endurance bus, for example).

When I started this exercise I really wasn't sure it was worth the effort. By the time it was done, I knew that it had been.

For example, Voltmeter Reads High in flight. Was this a high risk, medium risk, or low risk (with the above noted actions)?

What if the EGT or CHT reads high, or low, on one cylinder? High, medium or low?

Low battery light from my EarthX battery? High, medium, or low?

What if the oil pressure reads slightly low, or slightly high? What do I do Right Now?

Most of our training and emergency procedures in our POH's deal with total failures. There s little guidance on partial, or abnormal indications.

I don't know for a fact but I'm guessing there are more than a few accidents because some pilots did not understand the seriousness of a abnormal, or partial failure, of a system and continued to fly past the point of no return.

I keep my nine page System Emergencies checklist on my kneeboard along with my (standard) Emergency Checklist. I'll probably never need it, but it's there if I do. There is some comfort that I have already decided on a conservative plan should an abnormal conditon present itself.

FYI - I never return to a thread once I've posted on it, so there is no point in asking me questions or directing comments directly to me. I won't see them. It's my way of avoiding aggravation from responders who want do tell me how wrong I am...

 

[chemgeek]

If bus voltage is decreasing there is a problem with the charging system. Avionics can start to go wonky at around 10 V (12 volt systems) or 20 V (24 volt systems). Failure of the electrical system is an emergency if IFR, especially if not able to land in VFR conditions. If you have a vacuum system, you have partial panel backup. If you are using electronic instruments, useful flight time by instruments is limited by the lifetime of your internal backup batteries, but failure of the main bus may lead to loss of external support devices such as magnetometers, etc.

If flying IFR or at night, I would immediately abandon flight until the issue was identified. If day VFR, you have more options to get home safely, but perhaps without electric instrumentation and electrically operated gear such as flaps, etc.

 

[Shepherd]

You guys have electricity? sigh........

 

[Sundancer]

I've heard the transponder draws a lot of power - if correct that could be a good candidate for shedding load. But no clue what caused your issue. I don't see you did anything "wrong" in handling it - don't worry about it flying OK after you got it back.