Cabin preheat

[Marion]

Was wanting to use small space heater with a fan for cabin preheat. Will the electric fan cause a problem with my compass? my old flight instructor told me never run an AC motor in my cabin because it would cause a compass to be inaccurate is that a wise Tale .1968 c model

[ShuRugal]

Does the electric motor in your turn coordinator foul up your compass every time you turn the battery master on?

I'd just do it from outside the plane. Length of dryer tubing and a duct booster fan to blow air into the plane with your heating equipment on the ground outside it. Better than putting one of those fire hazards inside your cockpit, no?

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[Nokomis449]

OP mentioned an AC motor.   I've used a small ceramic heater sitting on the floorboard, and also used a small electric blanket draped over the seats.  Luckily where I live it's only an issue a few times a year, such as tonight when it's supposed to get down to around 16F.

What is this "compass" of which you speak? 

[Marion]

7 hours ago, Nokomis449 said:

OP mentioned an AC motor.   I've used a small ceramic heater sitting on the floorboard, and also used a small electric blanket draped over the seats.  Luckily where I live it's only an issue a few times a year, such as tonight when it's supposed to get down to around 16F.

What is this "compass" of which you speak? 

 The magnetic compass

[N201MKTurbo]

An AC motor will not magnetize things, it may actually demagnetize things. It’s magnetic fields are constantly reversing. A DC motor may magnetize things, it has a constant magnetic field. 
 

 

[ShuRugal]

An AC motor will not magnetize things, it may actually demagnetize things. It’s magnetic fields are constantly reversing. A DC motor may magnetize things, it has a constant magnetic field. 
 
 

You may want to "brush" up on your basic electromechanics. A DC motor still must produce a changing magnetic field, or it cannot produce rotation. The only difference between a "DC" and AC motor is the mechanism for varying the position of the field.

A magnetic motor with a non-changing field would act like a rotary solenoid. Not tremendously useful for producing continuous motion.

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[N201MKTurbo]

23 minutes ago, ShuRugal said:

You may want to "brush" up on your basic electromechanics. A DC motor still must produce a changing magnetic field, or it cannot produce rotation. The only difference between a "DC" and AC motor is the mechanism for varying the position of the field.

A magnetic motor with a non-changing field would act like a rotary solenoid. Not tremendously useful for producing continuous motion.

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Hummm, I work with motors of all types every day.

A brush DC motor has a static magnetic field in the stator created by a permanent magnet or an electro magnet, the magnetic field of the armature is somewhat stationary a few degrees ahead of the magnetic poles of the stator. It is kept there by the commutator. 

An AC induction motor applies AC current to multiple poles in the stator, this induces eddy currents in the rotor that makes opposing magnetic fields in the rotor that makes it turn. 

Either way you look at it, the DC motor has relatively stationary magnetic fields and the AC motor has rapidly reversing magnetic fields. 

[Brian E.]

I love my simple heater on a remote switch. that bridges the gap between the seats  I turn it on every time I preheat the engine as well.  No issues what so ever, hasn't melted anything and will turn off if it should ever be unsettled which it never has been.  

Use your heater and enjoy the benefits.

[ShuRugal]

Hummm, I work with motors of all types every day.
A brush DC motor has a static magnetic field in the stator created by a permanent magnet or an electro magnet, the magnetic field of the armature is somewhat stationary a few degrees ahead of the magnetic poles of the stator. It is kept there by the commutator. 
An AC induction motor applies AC current to multiple poles in the stator, this induces eddy currents in the rotor that makes opposing magnetic fields in the rotor that makes it turn. 
Either way you look at it, the DC motor has relatively stationary magnetic fields and the AC motor has rapidly reversing magnetic fields. 

Hmm, you may be right. Perhaps it is my brushes which require replacement. Or at least a healthy application of dielectric caffeine solution.

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[KB4]

14 hours ago, Marion said:

Will the electric fan cause a problem with my compass?

Not unless it’s on the glare shield touching your Compass.  Just put it on Px floor, a small ceramic heater with tip over protection works just fine. It warms up cabin to very comfortable temp in 10-15 min.  Run a cord thru pilot window with some foam to fill around cord. 

[Marauder]

Before I knew what a magnometer was, I had a love/hate relationship with my magnetic compass. I am convinced after degaussing my plane a few times that most of the time when a magnetic compass has become “magnetized” it is caused by power leads being tie wrapped to the roll cage.

Thank goodness for balancing balls.


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[steingar]

I've been running a small space heater (recommended on this very site!) but my compass is off big time, going in for repair next week.  I hope to hell the heater didn't start it, since the compass started going wacky about the time I started using the space heater.

[N201MKTurbo]

It is simple enough. Just take a portable compass and see if it points at the space heater. try it when it is off and on.

Even though the space heater has AC running into it, a lot of modern motors have permanent magnets in them. Especially if they are variable speed. They will use brushless DC motors where they can change the speed with software, or brush motors with resistors on the switch. 

Edited January 7, 2022 by N201MKTurbo

[carusoam]

There is a lot of pre-heat options discussed around here…

including remote operation using the latest cell phone switch options…

Use caution with big electric motors inside the plane… you can accidentally magnetize the steel cage…. Degaussing it can be really hard…

The magnetic compass can hang up on certain headings, if you ever have to execute compass based turns in simulated IMC….

Find @OSUAV8TER he is our remote heat supplier…. Has an excellent engineer supporting his product… who can supply this detail…

Best regards,

-a-

 

[EricJ]

On 1/6/2022 at 6:20 PM, Marion said:

Was wanting to use small space heater with a fan for cabin preheat. Will the electric fan cause a problem with my compass? my old flight instructor told me never run an AC motor in my cabin because it would cause a compass to be inaccurate is that a wise Tale .1968 c model

As already mentioned, AC is less likely to cause problems than DC.    The degaussers used to demagnetize things are AC.   The AC scrambles the existing field and then you draw the degausser away slowly to reduce the influence of the AC field so all you're left with is a random small residual.

+1 to just take a compass and bring it near the heater when it's running.   That let you know right away whether it is generating a static field.

[PT20J]

I tried this today. Turned on 1500W ceramic heater and brought it near the compass. No effect. I turned it on and off near the compass. No effect. One thing I noticed is that if I put the heater in the baggage compartment with the hangar near freezing it heats the cabin up in about 5 minutes and I have to put it on pretty low or it bakes me out of there. I guess all that mylar/foam insulation works. 

[Bartman]

Does this pose a risk of magnetizing the steel roll cage ?

We occasionally see a thread about degaussing and I wonder is this how the roll cage gets magnetized ?

[carusoam]

18 hours ago, Bartman said:

Does this pose a risk of magnetizing the steel roll cage ?

We occasionally see a thread about degaussing and I wonder is this how the roll cage gets magnetized ?

Read from top to bottom…

The thread became a discussion of magnetization and degaussing…

resulting in no harm no foul… and methods of knowing…

-a-