Cockpit Heat at Altitude

[Lance F]

A previous thread with comments about the many advantages of flying the higher altitudes (let's say above 15,000') and a comment by Bill S made me wonder about cabin heat. Is that a problem for those of you with single engine turbocharged planes? The back seat of my Mooney gets cold even with OATs at 5 deg. C. (according to my wife) even though my shoe soles are melting, since the only source of heat is at the front, and there's no ducting to the back.
If this is a problem, are there any solutions other than bankets?

 

[wsuffa]

Lance,

Cockpit heat can be a problem with most singles because it's taken off at one place: the exhaust stack. My experience is that twins w/cabin heaters are better.

The heater ducting on my plane goes into the back seats, but it can still get cold (even in the front) at night in the winter. Compounding the problem is an air vent under the back seat... strategically placed blankets or foam works wonders to block that source of cold air.

bill

 

[John J]

Lance;

I had the same problem when I had my Turbo Arrow. It did have some ducting to the rear but it was not enough to keep warm on cold days. I did cut up a heavy blanket to fit floor area where the feet would go and that did help some. Did find that the baggage area was a great source of cold particularly flying away from the sun. I would be roasting up front and the folks in the back were cold. Like your experience did use blankets for them. Had temps in the winter time down to minus 20c and more. Did a lot of flying in the Northeast during the winter in that plane.

I looked around to see what could be done at the time (15 to 20 years ago) but could not find an easy way to get more heat in the back.


John J

 

[ejensen]

My F heats the back OK thru the center console. Air really blast between the seats. Don't have much time is a J but the ducting must be different.

You might also check for draft. I had a real cold spot on my left leg. It turn out was coming back from the tail along the wire bundles. Sealing the hole where they penetrated the cabin help a bunch. Air should go out the back of the cabin vents and pull heat thru.

 

[Iceman]

We have this problem too in the winter up high when we are running 50 LOP. We find if you go to peak you will produce more heat and stay warm.

 

[Ed Guthrie]

A previous thread with comments about the many advantages of flying the higher altitudes (let's say above 15,000') and a comment by Bill S made me wonder about cabin heat. Is that a problem for those of you with single engine turbocharged planes? The back seat of my Mooney gets cold even with OATs at 5 deg. C. (according to my wife) even though my shoe soles are melting, since the only source of heat is at the front, and there's no ducting to the back.
If this is a problem, are there any solutions other than bankets?

Lance, you may be aware of this and therefor the following is totally irrelevant to your problem, but there are two air/heater vents, one in each foot/leg well on the Mooney. The pilot side vent is mid-way back and mid-height on the ride side kick panel. The co-pilot side vent is similarly located, left side. The airflow is controlled by rotating plates that cover/expose the vent opening. Many folks don't know those vents are present and the vents are either left off (pilot & co-pilot suffer cold feet) or left full on (pilot & co-pilot are comfy, but back seat passengers suffer cold feet). From your description I'm betting your vent (pilot side) is full on. Close it (or partially close it) and open the floor vent (bottom of center console) fully should solve the back seat foot warmth problem.

Or not. YMMV.

 

[Dave Siciliano]

Lance:

I definitely had that problem in the A-36 when very high or when it was cold at altitude. The A-36 has a manifold heat system that wraps the exhaust stack. When below -10C, the front seat occupants were O.K. but folks in the rear got very cold. I did a couple of things to assist: Check for any air leaks or air coming in through the back panel behind the rear seats. Have someone get back there while it's cold and check. If no leaks, make sure the heater vents are operating correctly: mine was not flowing to max potential. When operating the engine, LOP will produce hotter EGTs which will produce the most heat into the system.

I discussed this with the Gami folks and they have an after market upgrade that produces more heat if you fly high a lot. It could be worth checking.

Hate to say it, but this is another reason I went to the twin. The Janitrol heater actually burns avgas from the left main of the Baron and will run you out of the plane if you set it for max heat. Also, these planes just weren't made to deal with all the elements at high altitude--at least the A-36 wasn't. The after market upgrades will help as will getting the best performance out of the existing system, but you are pushing the envelope.

The pressurized single or twin has a sealed cabin which elimates all outside air unless you allow it in. As some point, if you fly high a lot and in cold or hot weather, the pressurized plane with better heating and airconditioning will perform substantially better. I haven't run the heater in the P-Baron yet other than to test it. Even at 0 C, I sometimes have to run the air conditioner to keep cool.

I know everyone can't go to a pressurized plane, but there are limitations on what the unpressurized plane can do because you are just exceeding design limitations. When it gets real cold out, even the heat transfer through the rear plexiglass can be substantial.

Best,

Dave
Baron 322KS

 

[Lance F]

Many thanks for the ideas. Looks like the heating/ducting system is just one more thing I'm going to have to get educated on. On the Mooney the heat that comes out of the bottom of the center console is substantial (Once I level out. There's virtually no heat output in the full power climb). I'm thinking about making something (that can be easily taken in or out that dividies this outlet in half. One half would discharge where it does now for the benefit of the front seats and the other half would go through a duct bringing the hot air into the rear seat area. Anybody ever try something like that?
At the same time I'll look for air leaks and make sure all hose connections and such are as they should be.

 

[Dave Siciliano]

Lance:
One other thing that worked for me on the A-36 was there was a fresh air inlet up in the engine area. That let outside air into the heating system. In the winter, I would block one inlet (letting less outside air in). There was another inlet; when I did that, the heat circulating inside got warmer. In the spring, I would remove the plug. Don't know your plane, but you might look into the concept.

BTW, I'm sure you know this but there is a leak detector you can use in the air; a very sensitive microphone that you can wave by door and window seals; it will pick up leaks you may not feel with your hand.

Best,

Dave
Baron 322KS

 

[ejensen]

Another probably obvious suggestion-- Try the fresh (cold) air vent fully open, especially in climb. You have to move more air when slow. Also might shallow out the climb.

 

[Henning]

Many thanks for the ideas. Looks like the heating/ducting system is just one more thing I'm going to have to get educated on. On the Mooney the heat that comes out of the bottom of the center console is substantial (Once I level out. There's virtually no heat output in the full power climb). I'm thinking about making something (that can be easily taken in or out that dividies this outlet in half. One half would discharge where it does now for the benefit of the front seats and the other half would go through a duct bringing the hot air into the rear seat area. Anybody ever try something like that?
At the same time I'll look for air leaks and make sure all hose connections and such are as they should be.

You could try the simple fix and climb at a higher airspeed and keep properly leaned adjusting it throughout your climb to maintain near peak EGT (within CHT of course) all the way up. From what you just told me, that should solve your problem.

 

[bbchien]

If this is a problem, are there any solutions other than bankets?

In Mooney N201MZ I had a second exhaust Muff added. It was ESSENTIAL at FL 21 in the winter. Lotsa heat. Bruce Jaeger at Willmar Air Service is the guy to see....it was on a 337.

 

[Lance F]

You could try the simple fix and climb at a higher airspeed and keep properly leaned adjusting it throughout your climb to maintain near peak EGT (within CHT of course) all the way up. From what you just told me, that should solve your problem.

This would certainly increase EGTs and therefore the temp of the air coming out of the heater. However, I'm a little concerned about climbing at peak EGTs. I am a big LOP fan, but even the gurus like Deakin don't promote peak or lean of peak operation during climb.

I do lean as I climb, but generally keep the EGTs approx 200 ROP (and even that makes me feel a little guilty). That 200 degrees should make the cabin heat hotter, but at what cost to the engine?

 

[ejensen]

Maybe because I'm almost at 75% on T/O, I start lean and keep it at 100 ROP on the climb. I know it is not very comparable but my CHT are all in the mid-low 1300s (30 degree spread). Hotest CHT is +/- 370. Oil temp is really the limiting factor on how long I can hold max climb at least in the summer.