I'm starting to fly on my own, and just did a 1500NAM flight in LRC. It took 5 hours, which is OK, but during that time I was *really* cold. Is this normal on the P180? Are there any tricks to make the cabin warmer? I've heard about "preheating", but don't think that would last 5 hours.

Edit: it was F400, SAT -63

Which aircraft serial number do you have? Which heating system, the (older) ACM or the Enviro system?

I have heard using manual heat instead of auto can help. You might try switching to Manual mode and turning the heat up.

Mine has the Enviro system, and so far has kept up acceptably. But it cycles between air flow that's a little too warm and a little too cool - on average it's about right, but it doesn't get to "just right" and then hold, it's more of a warm/cold cycle. That's in Auto mode, I haven't yet felt the need to try manual.

This suggests your system has a fault. The control system is oscillating. Besides being annoying, it will eventually wear out the actuator prematurely.

This sort of cycling is indicative of missing some feed forward term in the control system. This can happen predominantly for two reasons, loss of a feed forward sensor or aged capacitors in the control system not providing the right damping.

If your system has two temperature sensors, one for the cabin and one for the duct, then the duct sensor is the feed forward sensor. Its job is to sense changes in the output air early so the system delays moving the actuator while the cabin catches up.

It might be worth testing your duct temperature sensor to see if it is working right. I had a case on my MU2 where the duct temperature sensor worked when removed from the airplane, but failed when installed in the duct, so best to measure it in the duct if you can.

If that is bad, replace it and see if you system behaves more smoothly.

If the sensor works, then the controller might not be working right. No simple test for this outside swapping it or sending it to a shop that can repair it.

Mike C.

...
This sort of cycling is indicative of missing some feed forward term in the control system. This can happen predominantly for two reasons, loss of a feed forward sensor or aged capacitors in the control system not providing the right damping.

If your system has two temperature sensors, one for the cabin and one for the duct, then the duct sensor is the feed forward sensor. Its job is to sense changes in the output air early so the system delays moving the actuator while the cabin catches up.

It is most often just a thermistor, so an ohmmeter. The CMM will have a resistance versus temperature chart. if you don't have that, but observe decreasing resistance with temperature, it is probably working right.

Here is the chart for my ACM duct sensor, which may or may not be similar to yours:

Mike C.

Can you get to the controller? You can measure the sensor resistance at the controller plug. This also checks the wiring as well.

At the controller plug, you can also then check the cabin sensor resistance, and the cockpit setting potentiometer (assuming it works like my ACM controller does).

Mike C.

Yeah, was thinking along those lines too. I haven’t had the interior panels off where these things live, so am not yet certain, but I think they should be easier than where the sensors are described. Will see what I can get to.

The serial is 3016 and I guess it's the newer system. I haven't tried the manual setting yet. I have set both cabin and cockpit to 30C, but it didn't help much. The day before we were doing a normal, max cruise flight at F370 and the cabin was warm.

Ah, you have an Evo! Nice. You should have the Enviro system AFAIK. I would try manual mode to see if you can get more heat, but it sounds like maybe something’s not quite right with auto mode.

Just looked up the p/n of my duct sensor - 754691-1. Looks remarkably similar to the p/n on your chart!

If SAT was -63 that probably doesn’t help either. ISA is -57 at fl400. -63 is cold

-57 C or -63 C won't make that much difference trying to keep your toes at 25 C.

Mike C.

The reply I got from a trusted source in Genoa is that there’s not enough bleed at low power settings. The solution is cashmere blankets

Anthony figured out how to get a bit more heat a while back and I have used his technique a few times successfully.

When heat is on auto and full blast and still not warm enough you can switch to manual and barely bump warmer.

If you are not patient enough you will get a duct overheat and have to turn it off to cool down.

Switch to manual and do 6 or 7 ‘clicks’ to hot. You will be nice and toasty in minutes. Feel the air coming out of floor vents by pilot feet to gauge how hot you want it.

I fly long flights high up constantly and never have trouble staying warm with this technique. Only thing is with a full load of pax they will complain about the extra heat before you do.