Cabin airflow with all vents and defrost closed

[Paul Klouda]

Hello All!

Got a '64 PA24-250 that even when all side vents, heater, defroster, cabin air controls are closed I get a large amount of air movement in the cabin. It feels like it is coming from the rear of the passenger compartment possibly from the baggage compartment. I checked for loose or missing hardware on the rear bulkhead covers just in front of the battery but everything appears to be tight.

I did not notice the air in the summer because we kept the side vents open all the time (higher OAT and all) but with temps in the 30's - 40's its getting a bit cold! You feel it on the back of your shoulders, neck and head. Passengers in the rear seats will freeze on a trip of any length.

Air movement inside increases greatly with airspeed.

Any suggestions? Similar situations? Possible solutions?

Have a great Thanksgiving to all!

Paul

[rstan]

Paul
I plug the exterior air intake vent on the vertical stabilizer for the winter.
That stops most of the cold air flow
Good luck
Richard

[9089P]

Hi Paul,

I own a 260B which has a solid floor from front to back as the rear seats(3&4) are on tracks and removeable. However, I recall a discussion many years ago on the COF site indicating that there is a gap in the flooring of the 250 basically under the rear seat. This gap if I recall correctly is covered with canvas(?) which can rot over the years and allow air to flow thru the access hole between the fusilage and the wings. Again this is just what I recall from an old discussion.

Good luck, Don

[Mike Foster]

Paul,

To tag onto what Don is saying there is a fairly large port that exists at wing root where the gear conduit exits the fuselage heading to the main gear linkage.

Matt Kurke of Comanche gear has some neat little covers made up for that opening which should take care of most of the air movement.

I've never had to cover vent openings on vertical stabilizer, but we are in Southern California and don't head into the "frozen north" except in summer. So that may help some too.

Hope this helps, Mike Foster

[N8632Y]

Rich,
just how do you plug the opening in the vert stab? What material? Obviously, it has to be retrievable.
i'm headin out there today to plug holes,,it's gettin cold out
thanks, steve

[Paul Klouda]

Thanks for the input everyone. I don't see a vertical stab vent but do have one on the top of the fuselage near the rotating beacon. It had some upholstery type foam in it when I bought the plane, I removed it as it was summer. I will check the conduit seals per suggestion and the canvas cover under the rear seats.

Happy Thanksgiving to all! and keep the shiny side up!

[Chris Kuyoth]

Paul,

I was provided the following tip and it made a huge difference in my 65 260:

1) Buy a sheet of 1/2 in. closed cell adhesive backed sound insulation from Spruce - part no. 09-00444 - @ $19.
2) Pull out your rear seat, and locate the egress points of your flap and aileron cables.
3) Cut a piece of foam @ 4" x 4" (or whatever fits given the structure around the egress hole) and cut a slit into the center. Slip the foam onto the cable (into the slot) and adhere the foam to the skin on the inside of the airplane over the hole. The closed cell foam will not retain moisture which would lead to corrosion on the cable.
4) Do this on all openings into the wings including the gear conduits. I also plugged the holes in the empenage bulkhead at the rear of the baggage compartment that lead under the load floor. You will have to accommodate the battery cable, elevator and rudder cables....

Even if the canvas under your rear seat cushion is in good condition, it will not stop the airflow like the modifications I just described. Your airplane will be warmer and quieter.

Chris

[BobPicker]

Sounds exactly like the problem I had on my '63 250. I had checked and screwed, reinforced the rear bulkhead and still had quite a draft from the rear area. During an annual I spoke to my A&P. He started looking for something that caused pressurization of the fuselage aft of the bulkhead. Here is what he found and fixed. There is a scoop on the roof just aft the the bulkhead. The scoop feeds to a 2-3" round and 4-5" high can with a drain and air lines to feed cabin air vents. This can had a crack running about 1/2 way around it due to some stress on it by the hoses and air pressure. He repaired the crack sealing the leak into the rear fuselage area.

Guess what? The air flow through the rear bulkhead stopped and the cabin is comfortable in the winter. Take a close look at this area. You may have the same problem.

Bob

[Paul Klouda]

Thank you Bob and all for the suggestions and possible fixes!

We have been plugging, insulating and checking for openings all around the aircraft. It looks like the majority of the air is coming in under the rear seat (no canvas sling present) along the spar carry through. There may be additional air coming from behind the rear bulkhead but it is more difficult to identify.

The plane is tolerable now but my quest if far from over! If I find any other areas I will post them to help any other owner.

Again, thanks to all for your assistance!

Paul