Broken duct hose - what is this?

[Matt Ward]

Underneath the pilot panel, I noticed a broken hose. I think this is part 14 in the MM drawing but I can’t be sure. Does anyone know what this does and the consequences of the break? I’ve got an annual in a month and trying to figure out if it it can wait or not. 
 

[MB65E]

Looks like the hose to the defroster. 
it can wait just verify it’s not going to get caught in the flight controls. 
-Matt

[Matt Ward]

It’s still 20 percent attached so no impediment to controls. Thanks!

[Matt Ward]

By the way, what controls the defroster? Is it activated by the cabin heat? My 66 E doesn’t have any switch to control a defroster. 

[MIm20c]

If you close the vent at your knees it will increase the flow to the defroster. 

[Matt Ward]

Got it, thanks.  From the MM manual I couldn't tell if the air was coming in the black hose and then going on to the orange scat hoses, or, coming through the orange scat hoses and then going out the black (broken) hose.  Sounds like it's the latter so it really shouldn't be an issue so long as I don't need any defrosting.  Thanks for clearing that up.

[ShuRugal]

EDIT: looking at this again, that's hose 16. It supplies air to a 2" vent just behind the pilot seat aimed at the back passenger's foot.

 

Disregard everything I said below - it's all true for hose 14, but that's not hose 14 in your picture.

 

Hose 14 stuff:

 

You won't get any air to the defroster with that hose broken.

 

Those two metal things with shutters on them, one above each set of pedals, are what blow cabin heat and fresh air on the pilot/copilot.

 

Tube 14 supplies the pilot side vent from the distributer box

 

The defrosters are supplied by the distributer box always. When the pilot and copilot foot vents are shut, air goes to the defroster.

 

The defroster feeds are smaller diameter than the foot vent feeds, so if a foot vent is open, the defroster will let very little air.

 

With that hose broken, you are always venting at the pilot foot vent, though the aim is wrong.

 

Is there enough spare length on the tube to trim the damage off and connect the remainder? You certainly don't *need* it for flight in warm weather, but it sure is nice to have that vent working...

 

 

[Matt Ward]

Thank you very much for the insight. It’s quite helpful to a new owner! I will get it fixed. I just like to show up at my A&P having already done the troubleshooting and with a plan. This gives me that. Many thanks. 

[Matt Ward]

Thanks for the edit @ShuRugal  I’m going to fly in the am and I’ll check the rear vents and confirm with you I don’t feel air flow. Any way to confirm the defroster is working (in warm weather)? Seems like that should be unaffected if this is the rear vents. 

[ShuRugal]

Turn the heat on, close the foot vents, and stick your hand on top of the glare shield. If the defrost is working, you'll know pretty quick.

[alextstone]

Hey, @Matt Ward, while you are at it, ask the A&P to re align the hose clamp on the other duct...the one circled below.  The line is the border of the duct and the clamp is not fixed properly with overlap...

 

[alextstone]

Oh, and you seem to have dead body stuffed under the panel who appears to have COVID haircut...(please take that with the lighthearted humor with which it is intended).

[Matt Ward]

Definitely a COVID haircut by the wifey!

[alextstone]

2 minutes ago, Matt Ward said:

Definitely a COVID haircut by the wifey!

At least your wife will give you one...I look like a member of "A Flock of Seagulls" (that will give you something to Google for a laugh) and she keeps telling me to let it grow...

[Guest]

From the drawing, hose 14 supplies air from the firewall box on the copilots side, hose 16 supplies the back left seat, hoses 18&19 supply defrost air, hose 20 supplies the back right seat, hose 24 supplies cold air from the right side scoop to the firewall box,  closing valves 3&12 forces air to the defrost and aft seats at the same time.  
 

The other hoses on the left and right side wall scoops supply fresh water to your avionics.

Clarence

[Matt Ward]

Thanks @M20Doc! Do you agree my broken black hose is #16?

[Guest]

2 minutes ago, Matt Ward said:

Thanks @M20Doc! Do you agree my broken black hose is #16?

It sure looks like it is.  It should disappear behind the side Uphostery panel.

Clarence

[Matt Ward]

I’ll look again but it appeared to disappear in the direction of the firewall. That’s why I originally thought it was air coming in from the engine compartment. 

[ShuRugal]

I’ll look again but it appeared to disappear in the direction of the firewall. That’s why I originally thought it was air coming in from the engine compartment. 

The large tube coming in the back of the pilot vent is #14 in the diagram, it supplies the pilot side vent with air.

 

The tube going out the left side of the pilot side vent *should* be routed behind the upholstery to the pilot-side rear passenger footwell.

 

This is very easy to check on the ground with any source of air. Stick an air nozzle (or vacuum cleaner) into the broken hose. There should be airflow at the vent just above the floor behind the pilot seat. You will probably need two people to do this with the seat installed, unless you have really long arms.

 

[Immelman]

If your plane is like mine was, the hoses to the rear seat heat vents were quite degraded not only near the heater box but behind the interior paneling as well.

I replaced them all, and the ventilation and defrost all operate much better. I had no air out of the foot-vents because of all the holes.

Second note: SCAT tube is OK. Just OK. The orange hose in your pic is SCAT. SCEET is a much better product and easier to work with. More money but not excessive. I believe the original black hose is called CEET.

[Guest]

Scat and Sceet are an orange silicone/fibreglass duct, Cat and Ceet are rubber/fibreglass.  An easy way to differentiate them, single vowel is single ply construction, two vowels is two ply construction.

Clarence

[carusoam]

Two hoses of air enter the system....  

• Hot...
• Cold...

Five hoses of air leave the system...

• Defrost...
• Copilot... copilot has the important control, mixing box and a valve...
• pilot
• back left
• back right

If the copilot’s valve is broken... they get all the heat...

The chance of any air getting to the back seats is pretty slim... that takes having new hoses in there...

Closing either the hot air or the cold air limits the amount of total air being delivered...

PP thoughts on how the airflow can be enhanced...

Best regards,

-a-

[cctsurf]

On 5/5/2020 at 6:02 PM, Matt Ward said:

Does anyone know the diameter of pipe 24 on here?  I bought some 2.5", but it seems -REALLY- hard to get on the fittings, is it 2.75"?

Thanks!

[Matt Ward]

I'm sure you know this, but it's listed as part # 912007-503 in the MM, but only described as "duct" without any dimensions.  But it's coupled with a clamp numbered # an737-tw-91 which is described on Spruce as a 2.25" clamp, for what that's worth.

[cctsurf]

1 hour ago, Matt Ward said:

an737-tw-91 which is described on Spruce as a 2.25" clamp, for what that's worth.

That's significantly more helpful than I initially believed.  I knew the part # for the duct was useless, but I hadn't looked at the clamp...  Good catch!  I was initially groaning, 'cause a 2.25" duct would NEVER go on.

Looking at other websites, the last number (91) is the largest diameter of the pipe in 32nds of an inch, so 91/32nds is 2 and 27/32nds, or 2.84375", making 2.75" pipe really quite possible.  the smallest size it's supposed to close is 2 13/32nds, which is 2.40625", more than the 2.25" that Aircraft Spruce quotes.  Really, 2.5 is closer to the butter zone, better get back to trying the duct I have...