Cabin comfort 1965 M20E

[Chris Strube]

My heater works well, but the back seat is a meat locker.  I've replaced door and baggage hatch seals, and can't feel any air infiltration from either during flight.  However, a cold draft from somewhere keeps the back seat, and the backs of our necks very cold.  We regularly fly above FL180, so it's a real concern.  Has anyone found a cure for this problem?

 

thanks in advance...

[outermarker]

I too have a 65' E. There are ducts going to the baggage compartment and to the back seat area. Pull the belly pans and be prepared to scratch your head and say, "how'd they do that?!" I felt so overwhelmed when I saw it that I just left it in place. It was the original ducts and I knew that it was a can of worms I didn't want to mess with if I had any intentions of flying this past summer. Good Luck and take lots of photos to educate us all. Oh Yeah, make sure you can get the proper type/size before beginning or the lead times will leave you wanting to kick a dog on the way home!

Edited December 9, 2022 by outermarker

[Chris Strube]

Thanks for this.  I had a "Spatial Interior" installed a few years ago, and all the heater ducts had their furbish replaced.  Heat makes it's way back, but it's overwhelmed by that pesky cold draft.

[Shadrach]

Is the cabin well insulated?  We removed all of the old insulation decades ago and upgraded to 3/4 inch closed cell foam. We covered everything from baggage panels to ceiling. Only the floor was left un insulated and it has extra thick carpeting.  It made a noticeable difference in cabin comfort but only a small difference in sound proofing. Single digits are about the coldest we fly but no issues for pax.  It was 18df at 9500 when I flew to New York last week and my niece was asleep in the back with no jacket.  Also, make sure the louvered, cabin exit vents at the trailing edge of the wing are open, if they are not, heated air will not flow as well from front to back.

[DCarlton]

19 minutes ago, Shadrach said:

Is the cabin well insulated?  We removed all of the old insulation decades ago and upgraded to 3/4 inch closed cell foam. We covered everything from baggage panels to ceiling. Only the floor was left un insulated and it has extra thick carpeting.  It made a noticeable difference in cabin comfort but only a small difference in sound proofing. Single digits are about the coldest we fly but no issues for pax.  It was 18df at 9500 when I flew to New York last week and my niece was asleep in the back with no jacket.  Also, make sure the louvered, cabin exit vents at the trailing edge of the wing are open, if they are not, heated air will not flow as well from front to back.

Been curious about the intent and design of those exit vents at the base of the rear seat back.  Wonder if there is always a suction on them from the airflow in flight?  

[Shadrach]

1 minute ago, DCarlton said:

Been curious about the intent and design of those exit vents at the base of the rear seat back.  Wonder if there is always a suction on them from the airflow in flight?  

I’m pretty sure the louvered outlets are located in an area of low pressure under almost all flight scenarios.

[Chris Strube]

Thanks for the ideas.  I'll check the louvered outlets first.  I may be chasing an impossibility, as I've seen OATs in the -50C range.  My most northerly office is in Norman Wells, NWT (CYVQ), and I've flown there in winter!  

[EricJ]

Anything in my baggage area gets really cold.   My tow bar is nearly frosty sometimes when I take it out.    I'm guessing it's just air coming up through the floor or from the tail.  It's good for keeping food back there. 

 

 

[Shadrach]

25 minutes ago, Chris Strube said:

Thanks for the ideas.  I'll check the louvered outlets first.  I may be chasing an impossibility, as I've seen OATs in the -50C range.  My most northerly office is in Norman Wells, NWT (CYVQ), and I've flown there in winter!  

That is brutal cold. That’s a big ask for a light weight structure.

In those temps, if your baggage compartment walls aren’t well insulated, I don’t see how you’re going to keep the rear cabin warm.  If you have a retractable step, air is likely flowing through the rear fuselage and out through the tail. 

[BobbyH]

1 hour ago, Shadrach said:

In those temps, if your baggage compartment walls aren’t well insulated, I don’t see how you’re going to keep the rear cabin warm.  If you have a retractable step, air is likely flowing through the rear fuselage and out through the tail. 

My thoughts exactly.  I've been contemplating making a rubber boot for the step to reduce air-flow in the empennage after retraction.  Hopefully it will also reduce the dust and stuff that accumulates while taxiing.  

[Shadrach]

1 hour ago, BobbyH said:

My thoughts exactly.  I've been contemplating making a rubber boot for the step to reduce air-flow in the empennage after retraction.  Hopefully it will also reduce the dust and stuff that accumulates while taxiing.  
 

 

 

There is an even larger open around the flap jack shaft. My airplane has soft (used to be) synthetic fabric boots surrounding the jack shaft on each side. The shaft runs right under the baggage floor. I swear it came from the factory with the boots but no else has seen it before.

since sealing and insulating my cabin, it’s been pretty comfortable for passengers front and rear. However I’ve only tested in temperatures down to around zero while in flight. All bets are off at 60 below zero.

[Utah20Gflyer]

Might also check your mouse boots in the main landing gear wells.  

At the temperatures you are talking about cold prevention is going to be more important than heating.  You may want to take someone up with you who can pinpoint exactly where the air is coming into the cabin, then figure out the airs path, then figure out how to block it.  

In my case I had a round hole in my floor right by my trim wheel.  Cold air shot up out of the hole.  A piece of duct tape now blocks that hole and I'm a lot warmer.  You situation is unlikely to be that simple but in principle it's what you need to do.  

[takair]

Open the aft equipment panel and check that the harness feed through immediately on the workers side is sealed.  I’ve seen a number of these left open and it seems to draw in cold air…..or suck out warm.  I also plug my overhead exit vent in the hat rack during winter.   Still plenty of other leaks.  One issue with the aft heater vents n my E is that they are blocked by the front seats.  Not a great geometry.  As others have said, those are some seriously cold temps you are flying in, I suspect you would need to take extreme measures in sealing, insulating, optimizing to get effective heating.

[gmonnig]

My 65’ E is the coldest airplane I’ve ever flown in. I have all new hoses, so nothing blocking them. Checked and lubed up the heat box on the firewall, it’s working ok. Now I’m on to finding air leaks. My over head vent is permanently open for some reason so there is a little air coming through the four overhead vents. They can/are closed but I might have to make a cover to go over the exterior vent. There just isn’t a lot of pressure coming through the vents. Hell by time the air gets to the defrost holes, it’s not warm at all. Super weird. Good luck! I wouldn’t want a turbo on my E just for the fact that I’d freeze to death at FL180.

[Chris Strube]

The turbo didn't seem to affect the heat output.  Max heat output to the front is WAY too hot to handle, so I have to juggle the controls to make it bearable.  I have the same problem with defrost being anemic.

[MikeOH]

6 hours ago, Chris Strube said:

Thanks for the ideas.  I'll check the louvered outlets first.  I may be chasing an impossibility, as I've seen OATs in the -50C range.  My most northerly office is in Norman Wells, NWT (CYVQ), and I've flown there in winter!  

Well, speaking as a southern California native, I quit flying when the temps drop below +50F

[Ragsf15e]

29 minutes ago, Chris Strube said:

The turbo didn't seem to affect the heat output.  Max heat output to the front is WAY too hot to handle, so I have to juggle the controls to make it bearable.  I have the same problem with defrost being anemic.

Ha! -50c is colder than the “limit” on the SR-22T!  I think it’s-43C or so.  That’s cold.

Best bang for the buck is sealing the pass through for the avionics wires from baggage to tail compartment.  That’s a good draft.  Other thing is pulling your carpets front, back and baggage.  Seal up any/all openings with aluminum tape.

Good luck!

[takair]

One thing I also learned…counterintuitive, but it works.  The 64 E has some crude heat valves that are under the panel and between the legs of the two front seat folks.  I used to open them wide and had some really hot localized air.  Problem was, some parts of your body were really warm  and others really cold.  I have since found that if I keep these two valves close….or mostly closed,,,,it forces much more air to the rear outlets and defrost vents.  This has made a big difference for me…..much more consistent temps in the cabin. 

[M20F]

I found layering clothes, gloves, and an electric blanket fixed my issues with flying at 210 at night in the winter.  Keeping the windows defrosted is a challenge I still haven’t overcome.