Hot Fuel Selector

Txbyker · November 29, 2011

Now that temps aloft are requiring me to use my cabin heat I recall just how hot my fuel selector gets from the hot air blowing out of the vent. It is so hot I can hardly hold the fuel selector to change tanks. In some ways I worry that there may be some heat conductivity to the fuel line. Today I placed a notepad on top of the fuel selector to deflect the hot air a bit. The paper got very hot.

Does this affect anyone else and have any of you come up with some sort of vent deflector? I am sure I can fabricate one pretty easily.

**jetdriven** · November 29, 2011

Does yours have the vent which has a plate you can adjust? Early 201s had that, you can make it blow horizontal. The cabin heat is about 4X more powerful than it needs.

scottfromiowa · November 29, 2011

I have the vent deflector. I usually add some vent to the heat to moderate temps and angle higher...

**carusoam** · November 29, 2011

I am with Scott on this. Moderate with vent air.

You won't need max heat until you are in New England winter above 10,000'.

Then you can't get enough.

Best regards,

-a-

Txbyker · November 30, 2011

My vent is fixed in one position, no adjustment. Its a Lean Machine, not sure if it is different. I tried moderating a bit but my cabin heat at its lowest puts out a lot of very hot air. I think I will try to make a deflector out of lexan.

DaV8or · November 30, 2011

Quote: txbyker

My vent is fixed in one position, no adjustment. Its a Lean Machine, not sure if it is different. I tried moderating a bit but my cabin heat at its lowest puts out a lot of very hot air. I think I will try to make a deflector out of lexan.

sleepingsquirrel · November 30, 2011

If you fly LOP that temperature is bound to go down!

201er · November 30, 2011

Quote: sleepingsquirrel

If you fly LOP that temperature is bound to go down!

sleepingsquirrel · November 30, 2011

I mean really LOP, mine goes stone cold when I pull hard on the red knob!

**jetdriven** · November 30, 2011

Sounds more like a Lean Mean grilling machine. Had to say it!

Quote: txbyker

My vent is fixed in one position, no adjustment. Its a Lean Machine, not sure if it is different. I tried moderating a bit but my cabin heat at its lowest puts out a lot of very hot air. I think I will try to make a deflector out of lexan.

**jlunseth** · December 1, 2011

If You think New England at 10000 is cold you should try North Dakota at 21 thousand. It was -40 a couple of weeks ago, take your pick on C or F, they are the same at that temp. I had the problem with the fuel selector heating up. Had the A & P change the output adjustment at annual, but I think I am going to have them put it back and mix in vent air to cool it when OATs are more moderate. In winter at altitude I need all the heat I can get

M016576 · December 1, 2011

Quote: txbyker

Now that temps aloft are requiring me to use my cabin heat I recall just how hot my fuel selector gets from the hot air blowing out of the vent. It is so hot I can hardly hold the fuel selector to change tanks. In some ways I worry that there may be some heat conductivity to the fuel line. Today I placed a notepad on top of the fuel selector to deflect the hot air a bit. The paper got very hot.

Does this affect anyone else and have any of you come up with some sort of vent deflector? I am sure I can fabricate one pretty easily.

Txbyker · December 1, 2011

Hahaha, Byron I am going to come pick you up for a Texas BBQ at 8000 ft.

Ok, Carusoam please don't laugh at the newbie M20J owner but when you said moderate the air I think I understand now that there is a cabin vent knob next to the cabin heat. Duh. I guess they both come out.

Ok next question, where does this air come from? Any fear of carbon monoxide?

**carusoam** · December 1, 2011

Russ,

Pull them both...

My fault, "modulate" would have been a better word for this...

Hot air comes from a "muff" around the muffler. If there is an exhaust leak in the muffler, it can enter the heater muff, thus contaminating your cabin air. This device usually gets fully disassembled and inspected during annual. Hot air always smells like hot metal from here. CO sensors are a good idea.

The vent air source is separate from this, but gets combined with the hot air in an air box in front of the fire wall. (co-pilot side)

The flow of air from the different sources is controlled by slide gates that are at the end of your control knobs. If the knobs are difficult to operate, clean and lube the slide gates. They are on the air box.

This air mixture is then delivered to the cabin. In my m20c, it was through tubes that lead to each of the four seats. In my R, one big vent in front of the fuel selector.

High altitudes, cold air, low HP settings, and leaky cabin seals conspire to make it difficult to stay warm in the winter.

JL,

I have been to the Dakotas a few times. Emergency planning takes on a whole new meaning. Leather wrapped yokes become mandatory.

Best regards,

-a-

**jetdriven** · December 1, 2011

Try pulling the cabin air knob all the way out, and then cracking open the cabin heat slightly to modulate the temp.

xftrplt · December 1, 2011

Preheating the fuel, whether it's JP-5, 100LL, or wood, does increase the efficiency (very, very slightly) of the combustion event. In heavy metal that I've flown, the fuel-oil heat exchangers' function was first to cool the oil and, second, to warm the fuel to avoid ice clogging the fuel filters. There were also hydraulic-fuel heat exchangers in the fuel tanks to cool the hydraulic fluid. IMHO, wouldn't worry in the slightest about the temp of the fuel selector, or at least I'd rank it below asteroid strikes.

231BB · December 2, 2011

The fuel selector on my K model got pretty hot one morning in mid winter flying into Truckee airport near Lake Tahoe. I had the heater full on; it was very cold at altitude. As I was about to change fuel tanks, the lever came off. The set screw was just a little loose, and the heat caused sufficient expansion of the lever's collar to allow it to slip on the fuel valve shaft. So there you go, it can cause problems. And BTW, one night over the Sierras a meteorite narrowly (< 100 ft) missed my right wing. Granted, this would not have been as bad as an asteroid.

M20/KCCR

**jetdriven** · December 2, 2011

If gravity stoped working we would all be screwed. What is the market value of a 201 when you can just lift off and fly wherever you wanted for free? Whats the value of a A36 Bonanza? Gosh. that just scares me to death. Better sell now!

**jetdriven** · December 2, 2011

Was the probem the set screw was loose and you ignored it? Or was the problem was the hot air heated the plastic lever enough it moved without turning the valve? And how far in CA do you have to fly where running one tank dry can cause a crash beause you cannot access the other tank?

231BB · December 2, 2011

In my aircraft the lever is cast metal. Didn't ignore it, it just didn't reveal itself as an issue until it got scorching hot from the heater. I didn't want to jimmie over to the other tank in flight, reasoning that the greater danger was in trying to change tanks with a slipping lever and having the fuel selector shaft get stuck in mid position between right and left. Over the Sierras, small things take on a little more importance. It was a non-event, but it's just curious how things decide to fail.

M20K/KCCR

**jetdriven** · December 2, 2011

You are saying the lever is made of metal it was tight, and the set screw was loctited in place before takeoff with no slop? You flew it 121 NM (50 minutes) to Truckee, the fuel selector is now slipping and that created a hazard in an aircraft that burns 14 GPH and holds 37 gallons per side? It might slip when changing tanks yet you decided not to do it? Am I missing something? Do you blame a 15 knot crosswind for the "airplane getting away from you" and running though a ditch?

231BB · December 3, 2011

OK last entry on the subject:

Lever cold = Tight

Lever hot = Loose (as in off, in my hand, not connected to shaft)

Landed.

Tightened set screw with Allen wrench purchased in local hardware store (GA stimulating local economy).

Alive today. Non issue. End of story.

Hmm, jetdriven, 1493 posts I see in <1 yr.

**jetdriven** · December 3, 2011

How does a set screw loosen to the point the fuel selector is able to be pulled from the shaft from any heat delivered from a cabin heat vent?

TXByker has the deleted

231BB · December 3, 2011

http://en.wikipedia.org/wiki/Thermal_expansion

α =

1	$\partial V$
V	$\partial T$

xftrplt · December 4, 2011

Quote: 231BB

The fuel selector on my K model got pretty hot one morning in mid winter flying into Truckee airport near Lake Tahoe. I had the heater full on; it was very cold at altitude. As I was about to change fuel tanks, the lever came off. The set screw was just a little loose, and the heat caused sufficient expansion of the lever's collar to allow it to slip on the fuel valve shaft. So there you go, it can cause problems. And BTW, one night over the Sierras a meteorite narrowly (< 100 ft) missed my right wing. Granted, this would not have been as bad as an asteroid.

M20/KCCR

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