MAIN and STBY generator failures after severe turbulence/ice ingestion

[dcowsill]

Flying from MMAA to MPTO I encountered severe turbulence.  I was looking at my instruments and I was almost certain I was just gonna fall out of the sky in that thing.  My fault for not being more diligent reading weather reports out of Active Sky.  Also had NEXRAD off, so that didn't help.  I was in another room and heard thunder which was what alerted me to the situation.

Autopilot kicks out and I'm stick and rudder at around FL300 being bucked around by a thunderstorm.  I start hearing ice hitting the windshield and immediately flip the switches on everything, separator on.  I'm losing altitude, indicated airspeed jumping +-40 knots and I start hearing stall warnings.  I remember I need to feed in throttle to compensate for the loss of thrust from the separator and start doing that, noting that my torque is about 10-15% lower than the LRC cruise value I had set earlier (49%).  I feed in more throttle, but I found it difficult to check that the torque wasn't going too high and also keep the bloody plane from rolling over 90 degrees or more.  I set it a bit higher than where I needed it and forgot about it until I could regain control of the plane.

Thankfully before I got into the worst of it I was able to turn on NEXRAD and then switch over to and activate the weather radar, so I had a decent idea of what was in front of me.  I was already deep in the middle of it and didn't see an obvious heading that would give me an easier time of things.  Nothing left to do but soldier on.

Eventually the turbulence subsided and I was able to maintain steady, wings-level flight.  AP back on with a heading about 10 degrees west of a bit more of this storm, engine instruments all green and nothing on CAS but INERTIAL SEPARATOR, as expected.  I cleared the remainder of the storm, intercepted the GPS course and turned back towards Panama.

Good.  Time for a cigarette.

About 10-20 minutes later I hear the warning tone from the CAS (again from another room) and find that the plane is drawing about 31 amps from battery and I've got a LOW VOLTAGE warning.  ELEC system page doesn't show me much useful, except that neither the primary nor standby generator appear to be connected to the bus.  System page also confirms the 31 amp draw I see on the instruments.

I didn't have the POH handy and was still handling this plane in real time at that point, so I just started trying things I thought might work.  First thing was to turn it off and on again, so I switched the generator off then on.  No effect.  I remember the stand by generator and switch to it.  ELEC system page shows that the standby too is not connected to the bus and not producing power.  Instruments still show a 31 amp draw from the battery and low voltages.  I found the generator reset buttons and found that pushing the standby generator reset got me a brief blip of 70 amps of power before it died.  Main generator reset didn't appear to have an effect.

Again, I'm flying blind without my POH and have only a rudimentary idea of how to troubleshoot a problem like this.

At this point I started planning to land at the nearest airfield and found that there was one inside of 50 miles, MGSJ in Guatemala.  I tuned its VOR frequency, set a heading about 30 degrees east of my GPS course and started a 1200 ft/m descent to 10000 feet.  There are mountains east of me, an ocean to the west.  After checking the weather in San Jose and making sure to set my backup instrumentation's baro as well as the primary, I started planning a visual approach to runway 33.  I turn around, start heading west out over the ocean and try to prepare myself to make this approach using only my backup PFD in hazy conditions.

After a rather precarious descent (reaching up to 3500 ft/m at points) I was able to locate the runway and make a safe landing using my primary instruments.  The battery held up the whole time and even had a descent charge in it on the ground when I tested it.

On the ground, I found that the standby alternator was completely busted, but everything else (including the primary generator/starter) was fine.  The log from the aircraft has this to say for itself:

2019-07-13 15:33:37 TBM900[fail.c:932]: Component standby alternator has failed due to excessive wear (worn: 100.000000%, slope 1.0). You can prevent this by observing performance limitations and servicing the aircraft regularly in the maintenance hangar.
2019-07-13 15:33:37 TBM900[fail.c:935]: Failure impact: sim/operation/failures/rel_gen1_lo
2019-07-13 15:33:37 TBM900[elec.c:1210]: STBY GEN tripped (120.6A, 28.3V, rpm: 1)
2019-07-13 15:33:57 TBM900[fail.c:932]: Component standby alternator has failed due to excessive wear (worn: 100.000000%, slope 0.1). You can prevent this by observing performance limitations and servicing the aircraft regularly in the maintenance hangar.
2019-07-13 15:33:57 TBM900[fail.c:935]: Failure impact: sim/operation/failures/rel_g_gen2
2019-07-13 15:34:09 TBM900[elec.c:1210]: STBY GEN tripped (120.0A, 25.1V, rpm: 1)
2019-07-13 15:34:18 TBM900[elec.c:1210]: STBY GEN tripped (121.5A, 25.1V, rpm: 1)
2019-07-13 15:39:53 TBM900[elec.c:1210]: STBY GEN tripped (121.4A, 24.9V, rpm: 1)

This would support my theory that the standby generator failure was unrelated to turbulence or ice ingestion.  If it were ice ingestion, from the minute or so that I flew through hail and rain without the inertial separator on, then I would expect to see the engine instruments show some sign of trouble.  They remained green the entire time.

At 15:33 we see the failure, apparently due to wear.  12 seconds later STBY GEN is tripped, but I don't see a failure in the main generator that would support that condition.  After that, since both main and standby are gone, I'm on battery and have to land.  The subsequent trip at 15:39:53 is likely a result of my playing with buttons.

Now, I don't know if the main generator should necessarily have been rendered inoperative by a standby generator failure, but this was a wild ride and I genuinely enjoyed the experience.  I have never had an experience anywhere close to this in any other simulator using any other product.  Not only did I encounter turbulence and conditions that somewhat match what's actually going on over Guatemala at that time of day (thank you Active Sky), but I experienced a string of failures subsequently that forced me to land the plane in order to safely conduct the flight.

What's even cooler is I cared about the plane, which changed what decisions I made after encountering the failure.  I lost 3 airframes in the first couple weeks of owning the TBM and this fourth one has more than 60 hours on it.  I wasn't gonna lose it.  It didn't even occur to me that I might pause the sim or quit and reload.

Anyway, this plane is amazing and it keeps getting better it seems the more I fly it.  Thanks!

 

[EGT]

I've found the gens trip if the RPM surges. I'm not sure if there is an over-speed disconnect or not.

I encountered some mild turbulence where the engine RPM surged, and then icing conditions. A bit later I noticed the gen had tripped, though there was no reason for it to have done (that I saw).

While the engine audibly surged, the engine instruments didn't really support this (prop RPM did fluctuate slightly but remained in the green).

I did get popping from the turbine (intake icing?). I powered back, switched on all the de-ice systems, and held on.

I had deliberately flown into icing to see what happens. I've never had a situation like that in the sim where I was actually wondering if I'd make it out the other side.

I also lost the gen once sometime around landing or shortly afterwards. Again, not sure why, and didn't see anything that indicated it should trip.

I now keep an eye on the voltages and the gen bus during icing and other engine events to check it is still connected.

Edited October 20, 2019 by EGT

[LKN]

On 7/14/2019 at 1:45 AM, dcowsill said:

What's even cooler is I cared about the plane, which changed what decisions I made after encountering the failure.  I lost 3 airframes in the first couple weeks of owning the TBM and this fourth one has more than 60 hours on it.  I wasn't gonna lose it.

I feel you! I read your post carefully, I had some kind of similar experiences and now I have a cemetery of TBM. May they all Rest In Peace.

That makes this bird unique in our flight sim world, I believe that it is the only one that can provide such a sens of realism!

I have a long flight to make today with fseconomy LFOK/UKWS 1663 nm... it's tied, it's icing conditions, I feel worried like I am for real flights sometimes, I love this feeling at home that the TBM 900 offers...