air flow

[David Callon]

I have this vent that looks like it does nothing. The twin has very poor air circulation. I know where the hose goes I just don't think it does anything. During the summer at 150 kts the airflow from the little ball vents in the dash barley move any air. Anyone have an idea how to get better airflow?

[skipsouthernsky]

Dear David,

Not sure what I am looking at. What part of the plane is that? Is it behind the baggage compartment? Inside the fuselage under the instrument panel? Where is it that we are looking at? Please be more descriptive about the picture. Thanks.

Sincerely,
Skip Dykema

[N3322G]

David,

Can't tell from Pathfinder what model you fly. I have a 39 and the eyeball vents in the front move air just fine. My apologies if you have already checked this - on a 39, in the lower right, the panel vent and air flow levers need to be to the left. There are also forward footwell vents that will move air. In the summer, we point the mid-cabin eyeball vents forward as Texas can be hot.

There are some nice diagrams in the Service manual on this website under the Tech tab. Section 13 on where airflow originates and therefore, it would give you the areas to check. Hope this helps.

[9089P]

Hi David,

Based on a WAG, I'd say that the scat tube I'm looking at is behind the rear bulkhead in the tail of the plane. On my 260B there is a similar tube that takes air from the cabin, from a vent in the hat shelf, out thru a vent on the belly of the plane. The scat runs between those 2 vents. Yours looks disconnected from the upper vent, perhaps done as a winteriztion project? The eyeball vents at the front of my aircraft put out enough air to make your eyes water if you are not wearing sunglasses.

Good luck, Don

[David Callon]

The scat tube is behind the baggage compartment. The air flow out of the front eye balls is very low. I have checked all scat tubes and see no restrictions

[Don Nelson]

Hi David,

We're still not getting your model twin. If an early model and if like the early singles, I think that scat tube you show comes from the bottom of the hat shelf.
If a later model like my 30B, it probably comes from the bulkhead above the smaller hat shelf. Both exhaust cabin air thru the belly.
(In an earlier post, regarding too much cold air, I mistakenly thought that scat coming from the dorsal fin vent. Later I discovered the dorsal fin vent supplies air to the eyeball vents for the middle, or back, two seats.)

In my 30B, the fresh air to the eyeball vents at the panel corners comes from a scoop in the nose, as does the air to the heater. And it's a lot of air - so much that as one of my eyeballs won't shut off, I've put a plug in it.

The service manual has a pretty good diagram of the fresh and heated air systems.

Best, Don

[Kevin Bolender]

Some time ago, tired of low air flow, I opened the hood on 8871Y (PA39) and found the ventilation door in the nose not moving freely with the cabin control lever. Lubricated an worked the door nice and free but still had limited air coming through. I used a blower on the nose for air induction and eventually found two scrubby type sponges deep in the hoses, probably inserted long ago to prevent criter entry. After removing the obstruction the air coming through is unbelievably
Strong and provides the fresh air that was in the original design. Good Luck with yours!! KB

[Francois Marquis]

David,

In order for any vent to work, you need to create a negative pressure inside the cabin.

That scat on your picture normally connects the upper hatshelf vent to the lower belly exit. In orther for that to work it needs to be exempt from leaks. Have a close look at the rearmost right hand side floor section. That whole box needs to be sealed. Including the side lightning holes in the floor support formers. They originally were covered with fabric. That also include the grommets for the cable exit and so on.

Any leak there, will cause that suction generated from the lower belly exit to be stolen by anything else than the cabin air you wish to evacuate.

My $0.02

Francois Marquis
C-FTWK