Cabin Heat Cooking Avionics

[Shadrach]

3 hours ago, Yetti said:

There should also be a radio cooling tube. Clear plastic 1 ".  Coming from copilot side vent. Top of vent. Check for obstructions

My 67 F has the cooling tube from the passenger side NACA duct, but it's is orange SCAT, not clear tubing.

[TTaylor]

Also, forgot to say that the defroster tube attachments on the 75F are terrible.  The SCAT tube can slide off easily and be pumping hot air directly into the top of the panel.

 

 

[Shadrach]

1 hour ago, kpaul said:

In our Fs you are only getting the heat from the center vent below the T-P-M controls.  I have considered using a tube from the center vent to the back, as it seems that only my daughter gets cold back there.  Once I move to cooler climates I will think about it more.

Here in Florida I occasionally run the heat a little at altitude.  I also occasionally run it just to watch my CO2 detector and check for any leaks/changes.  So far my Sensorcon has not shown an increase in CO2 with the heater on.  

I have five heat vents in my 67 F. Two separate defrost vents at the glare shield. Two individual vents in the foot wells that blow directly at the rudder peddles and the the center "blast furnace" vent.  My airplane is thouroughly insulated (passenger compartment completely encapsulated with closed cell foam. Heating has not been an issue since (never really was).  If anything my bird has a surplus of heat. The biggest challenge is finding that "set it and forget it" blend. I am often making small adjustments to keep everyone comfortable. That being said, my Mooney maintains a toastier cabin then any non pressurized GA aircraft I've ever flown. 

[Marauder]

I have five heat vents in my 67 F. Two separate defrost vents at the glare shield. Two individual vents in the foot wells that blow directly at the rudder peddles and the the center "blast furnace" vent.  My airplane is thouroughly insulated (passenger compartment completely encapsulated with closed cell foam. Heating has not been an issue since (never really was).  If anything my bird has a surplus of heat. The biggest challenge is finding that "set it and forget it" blend. I am often making small adjustments to keep everyone comfortable. That being said, my Mooney maintains a toastier cabin then any non pressurized GA aircraft I've ever flown. 

The 75s also have those footwell vents. Ours have little doors slide over them to cover them.


Sent from my iPad using Tapatalk Pro

[Marauder]

Do you still have the original square flap vent in the front, like the one pictured below?
 

I have since "upgraded" to this which would allow a tube to be attached easier.
 

Hey! I recognize that vent. How does it work without the wedge?




Sent from my iPad using Tapatalk Pro

[kpaul]

47 minutes ago, Marauder said:

 

Hey! I recognize that vent. How does it work without the wedge?




Sent from my iPad using Tapatalk Pro

 

Actually it has a wedge, just not enough of one.  When I have time I will build a better one.  But it works pretty well, thank you for the inspiration.

[Shadrach]

51 minutes ago, Marauder said:

 

The 75s also have those footwell vents. Ours have little doors slide over them to cover them.


Sent from my iPad using Tapatalk Pro

 

Mine have butterfly valves and they will absolutely, positively roast your feet if full heat is diverted through them.

[Browncbr1]

On 11/28/2017 at 11:12 AM, Shadrach said:

I have five heat vents in my 67 F. Two separate defrost vents at the glare shield. Two individual vents in the foot wells that blow directly at the rudder peddles and the the center "blast furnace" vent.  My airplane is thouroughly insulated (passenger compartment completely encapsulated with closed cell foam. Heating has not been an issue since (never really was).  If anything my bird has a surplus of heat. The biggest challenge is finding that "set it and forget it" blend. I am often making small adjustments to keep everyone comfortable. That being said, my Mooney maintains a toastier cabin then any non pressurized GA aircraft I've ever flown. 

Yea, I'm thinking my blend door or linkage must have some slop... a recent trip in -4c OAT was very comfortable though... didnt' have to adust too often.. though, I always have my fresh air vent wide open no matter what as precaution against CO PPM .

[Shadrach]

17 minutes ago, Browncbr1 said:

Yea, I'm thinking my blend door or linkage must have some slop... a recent trip in -4c OAT was very comfortable though... didnt' have to adust too often.. though, I always have my fresh air vent wide open no matter what as precaution against CO PPM .

The "blend door " is viewable at the pax side footwell. Probably easiet to pull the instrument cover.

[jetdriven]

On 11/28/2017 at 8:03 AM, kpaul said:

FWIW most of those boxes get very hot even with cooling.  In my work planes - PC-12s, the 430W get blazing hot as does many of the other components we have installed.  Also we regularly operate in locations where the ground air temp is 55°C (130°F) and I have yet to have one shut down or have reduced functions due to heat.  The GTN 650 in my Mooney gets hot, but I have not noticed increased heat with the heater pulled, although I never run full hot with no fresh air mixed in, I do not currently live in an area that requires that much heat.

 

The gtn750 has an internal fan 

Edited November 29, 2017 by jetdriven

[podair]

my rear seat passengers used to complain systematically they were freezing at the back when flying high. I once measured the difference between pilot seat and rear seat and it was 20deg c! Always nice and toasty for the pilot, I never complained...

I tried a few times to run a duct from the centre vent and it helped. I was going to look at a neater solution but we then re did the intrerior and especially re-insulated the cabin. It has made an enormous difference. The better insulation means I never get any complaints and hardly have to use heat.

[Browncbr1]

2 hours ago, podair said:

my rear seat passengers used to complain systematically they were freezing at the back when flying high. I once measured the difference between pilot seat and rear seat and it was 20deg c! Always nice and toasty for the pilot, I never complained...

I tried a few times to run a duct from the centre vent and it helped. I was going to look at a neater solution but we then re did the intrerior and especially re-insulated the cabin. It has made an enormous difference. The better insulation means I never get any complaints and hardly have to use heat.

I too have noticed a less drafty, more comfortable cabin following my interior makeover.   Come to think of it, I haven’t had any complaints from the back seat either.

[Gary0747]

On 11/28/2017 at 5:43 AM, Yetti said:

There should also be a radio cooling tube. Clear plastic 1 ".  Coming from copilot side vent. Top of vent. Check for obstructions

There is actually a wafer valve in this line right at the copilots right knee that can easly get closed blocking outside cooling air to the back of the center avionics bay.   My tubing is not clear but is scat tubing approximately an inch in diameter. The valve is right where the tubing fits over the metal tube. 

Edited November 30, 2017 by Gary0747

[Shadrach]

On 11/29/2017 at 10:52 PM, Gary0747 said:

There is actually a wafer valve in this line right at the copilots right knee that can easly get closed blocking outside cooling air to the back of the center avionics bay.   My tubing is not clear but is scat tubing approximately an inch in diameter. The valve is right where the tubing fits over the metal tube. 

And I'll add that the internal wire in the SCAT tubing can corrode and disintegrate over time.  The remnants will collect at the valve blocking air flow. 

Public Service Announcement - if doing an internet search for SCAT tubing always use the "ing".  I once googled SCAT tube and it was a horrible mistake...

Edited December 4, 2017 by Shadrach

[MARZ]

I have a 67 and had an avionic cooling fan installed - The original design does not route air directly into the ports on the newer radios - it's basically a flat panel with slots to direct air across the stack (item 28)

 

 

[DualRatedFlyer]

Found that one of the defroster tubes had indeed slipped off the defroster port. Was able to get it reattached so well see if that makes a difference. 

 

Haven't seen the rumored cooling hose that goes to the avionics deck from the copilot side. Does anyone have a picture of theirs? I've attached what mine looks like. Sorry for the closeups. You can see only one large diameter scat tubing from the copilot side that goes to the mixer. 

[Yetti]

The bottom pic on that oval tube off the outside vent is absolutely horrible to try and reattach.  I think I ended up using a stainless clamp and or aluminum duct tape. 

The first pic that black hose has 100LL in it.   You might want to upgrade to stainless covered hose with teflon inner core.  Or an E I gauge and leave the fuel out side. 

[N201MKTurbo]

18 hours ago, Yetti said:

The bottom pic on that oval tube off the outside vent is absolutely horrible to try and reattach.  I think I ended up using a stainless clamp and or aluminum duct tape. 

The first pic that black hose has 100LL in it.   You might want to upgrade to stainless covered hose with teflon inner core.  Or an E I gauge and leave the fuel out side. 

That hose does have a stainless braid. It is covered by nitrile rubber and then the fabric over braid. They are quite robust. Try to cut one some time, you need an abrasive cutoff wheel and then it isn't that easy. 

[N201MKTurbo]

You are supposed to use a sheet metal screw to attach the duct to the defroster diffuser. Just slide it on (not easy) screw the screw in till it just bottoms out (almost impossible) don't over tighten it and strip the hole. Then put a ty-rap around it for good measure.

The job is a lot easier if you remove the windshield and all the avionics first!

[takair]

On 11/28/2017 at 11:12 AM, Shadrach said:

The biggest challenge is finding that "set it and forget it" blend. I am often making small adjustments to keep everyone comfortable

I have just the thing for you.  Has a mix mode too.  

[Ross Woodley]

I got my M20C in the fall, but recently went flying in winter and it was incredibly cold.  I look at other pics and believe I'm missing a tube that connects from the left side of the co-pilot seat to - not sure where.  Can anyone tell me the diameter and length of that tubing and where it connects.  The top picture is of my plane and the bottom is what I believe is missing...Thanks.

[milotron]

On 12/2/2017 at 5:41 PM, DualRatedFlyer said:

 

@DualRatedFlyer

 

In this picture, just to the left of the big black hose, there are two red pipe caps ( barely visible behind the carpet ). These are the ports from the NACA duct on the copilot side meant for the avionics blast cooling. I believe it is 5/8". I don't think this method of cooling is generally recommended any more due to the possible ingestion of wet air.

I just pulled the stub of clear poly hose off that was on mine. I have an avionics blower and evidently when they installed it, just cut off the old hose leaving a jet of cool, wet air left to douse the copilots legs. It must have been like this for 20 years!  I put a pipe cap on it and put my 120V power plug though it for the heater and dehumidifier as I am tied down outside.

 

iain

[carusoam]

This system has changed a bit over the years...

It would be good to mention what year your plane is...

By Mr. Woodley's tail number, his is newer than my 65C... But, Mr. Woodley's hand cranked gear indicates an older plane than ‘65...

Things to know about the air heating....  in 1965.

1) There is an air plenum with two slide gates up on the FW...

2) one gate is for outside air.

3) the other is for heated air from the heat muff.

4) make sure the knobs are working the gates.

5) follow the hoses...

6) if a hose doesn’t come from the muff to the plenum... no heat.

7) The plenum delivers the blended air to the splitter box in front of the co pilot.

8) a movable gate allows the co pilot to have all of the heat... or share it with the three other hoses.

9) pilot's heat hose is pretty short

10) back seaters have Long small diameter hoses that hardly deliver any air under best conditions...

11) original hose materials can’t possibly be working after 50 years.  The materials degraded, or got crushed, or just fell apart...

12) Check the splitter box’s gate for proper operation.  Hardware could break, fall apart, or go missing...

13) Dimensions and length of tubing can be measured by their connections.

14) The slide gates in ‘65 were mild steal and liked to rust, making operation difficult without lubrication just before the chilly season.

15) in later years the slide gates were replaced with rotating valves with rubber disc seals.  Plan on getting new pieces of rubber cut and installed...

16) get a copy of the parts and maintenance manuals for your plane... some are posted around here somewhere.

So....

if you see a round hole that looks like a hose is supposed to attach to it.... try to find a matching one further upstream.... 

How is that?

PP thoughts only, not a mechanic...

Best regards,

-a-