Got my first real trip with family Thursday and wouldn't you know it the heater thermostat relay is out so heater is inop. I've been flying low without heat and doing just fine. How much heat can I expect from eyeball vents if I totally close the heat exchanger? Flying to Florida so worst case I can just file lower and should be fine. I was looking forward to up high and tail winds.

None.

"None" may be a little extreme - I'm sure there is some difference in the temperature from the eyeballs if the heat exchanger butterfly valves in the wing root are closed, but it's not a lot.

I'd plan to bring blankets and fly low. The cabin's going to get chilly in the flight levels without a heater.

FYI, the heater in the 421 works extremely well and will keep the cabin warm pretty much no matter what the outside air temp is.

Robert

The difference is 9 degrees IME. So, in cruise the eyeballs will go from cold to 9 degrees warmer than cold.

If you turn on the heater before you open the air flow a CB in the nose will pop and make heater inoperable. This can only be reset on the ground.

This is what I was told. Just verifying.

Thanks everyone.

Well if it makes you feel any better, neither Robert not I are currently possessed of an airworthy 421...

I've only made one cross country round trip in a twin without heat and the only way I'd do it again is if I'm being well compensated.

I'd be hard pressed to put my family in that situation. I'd go to Academy or a snow ski store and pick up heated socks, gloves and whatever else is on the market these days......blankets don't get the job done IMO.

One of the guys at the local flight school wanted to fly an Apache back from Kansas to Ohio, without heat in the winter. All to get some multitime. I loaned him my electric heated motorcycle suit which was helpful. I think he had no idea how cold it would be without an operational heater.

I flew a 320 over the cascades once without a heater. Feet have never been colder!! BH

Made it with no problems. Flew down at 13,000. OAT hovered about -3. In the back they kept their coats on. Up front we had to take coats off once the sun started coming in. The 70 knots tail wind shortened the flight.

I rarely have to turn the heat on in my 421 and I flew down to Florida the other day and it was -8 C. With the heat exchangers completely closed you should get pretty good heat coming from the floor. The heated air is your pressurized air coming off of the turbos.

Anyone know if you can get a 24 volt dc plugin heater? Seems like a great backup for trips.

Pascal Goesslin had something like that rigged in the back of his P210. Unsure if it was STC'd or a portable install. I'd be a little wary of something drawing that much current, though presumably you could get an outlet capable of drawing major amperage wired pretty easily.