Water puddling outboard of extended tanks

[FlyingDude]

Hey all,

There are many drain holes forward of the spar, however there's only one aft of spar - and that is by the gear. Aft of the spar, access panels also have little drain holes. But, how does any water that gets between the drain of the access panel that is just outboard of the extended tank and the rib acting as the tank's outboard wall get drained? There's an ever slight slope which could let some water puddle. Any thoughts? Solutions? Thanks

[EricJ]

FWIW, the holes in the access panels are vents so the wing doesn't explode when you climb up to high altitude, or collapse when you come down in a hurry.   They do also allow moisture vapor out, but for the most part the wing spaces should stay dry.

[FlyingDude]

7 hours ago, EricJ said:

most part the wing spaces should stay dry.

Well, there's some puddling after having flown in heavy rain and IMC... I've been in and out of those wings since I've bought the plane 3.5 years ago... Never had this problem before, but also because I only flew in not-so-wet conditions... I'd like that water to drain.

 

 

[PT20J]

That's interesting. I fly in the rain (I live west of Seattle after all) and I never get puddles on the hangar floor under the wings. Do others get that?

[FlyingDude]

1 hour ago, PT20J said:

puddles on the hangar floor

It's not on the hangar floor. It's along the outboard rib of the extended tank... It's inside the wing and I want it to drain on the hangar floor...

[PT20J]

1 hour ago, FlyingDude said:

It's not on the hangar floor. It's along the outboard rib of the extended tank... It's inside the wing and I want it to drain on the hangar floor...

How do you know it’s there if it is inside the wing? How does it get in the wing?

[FlyingDude]

9 hours ago, PT20J said:

How do you know it’s there if it is inside the wing?

I opened the access panel and cleaned ice...

[Shadrach]

2 hours ago, FlyingDude said:

I opened the access panel and cleaned ice...

Do you have the Monroy Aerospace upgrade below? Have you contacted them for advice?  I believe there have been several different shops acting as installers of this STC since it was approved in the 80s. Not hard to imagine that there might be inconsistencies in those installations.  First thing I would do is verify that the installation complies precisely with the STC. It seems to me that drainage would have been a consideration during approval.

 

 

[FlyingDude]

@Shadrach mine was installed in 1984. No i haven’t contacted the company. haven’t they sold the stc to someone else? Yes, of course I’ve verified compliance with the stc that I have. The installation plans do not include any drain holes. Only 2 holes are for the fuel sampler and fuel vent. The fuel vent pipe hole is as far from the rib as the original Mooney drain hole is from the rib adjoining the gear well. We’re talking about small quantities which I’m sure seep between ribs and sheet metal. That’s how there’s no humidity in the other bays more outboard of this one.  I opened the bay next to the gear and there was no water/ice there either. Well, if riveted metal joints were waterproof, cs3204 sales would go to 0 and no more weep no more… However, the sealed tank blocks the down flow and you get a tiny accumulation in the area between the rib and the hole for the fuel vent pipe, which happens to be in the low-point.

at this point, I assume none of you have had this problem or noticed that you have it. I haven’t had it for 3.5 years either. I’ve been in those bays so many times but only lately have I flown in rain and wet clouds for 4 hrs straight.  I might stop cloud surfing or I might even sell the plane and rent…

I think I’ll keep cleaning it during winter and come spring, I might seal that side and stuff sealant to reverse the slope. 

 

[Shadrach]

1 hour ago, FlyingDude said:

@Shadrach mine was installed in 1984. No i haven’t contacted the company. haven’t they sold the stc to someone else? Yes, of course I’ve verified compliance with the stc that I have. The installation plans do not include any drain holes. Only 2 holes are for the fuel sampler and fuel vent. The fuel vent pipe hole is as far from the rib as the original Mooney drain hole is from the rib adjoining the gear well. We’re talking about small quantities which I’m sure seep between ribs and sheet metal. That’s how there’s no humidity in the other bays more outboard of this one.  I opened the bay next to the gear and there was no water/ice there either. Well, if riveted metal joints were waterproof, cs3204 sales would go to 0 and no more weep no more… However, the sealed tank blocks the down flow and you get a tiny accumulation in the area between the rib and the hole for the fuel vent pipe, which happens to be in the low-point.

at this point, I assume none of you have had this problem or noticed that you have it. I haven’t had it for 3.5 years either. I’ve been in those bays so many times but only lately have I flown in rain and wet clouds for 4 hrs straight.  I might stop cloud surfing or I might even sell the plane and rent…

I think I’ll keep cleaning it during winter and come spring, I might seal that side and stuff sealant to reverse the slope. 

 

For what it's worth, I have never found water or evidence of water inside my wings.  If water was pooling inside, I would expect to see evidence of some sort.  Even using a light duty pressure sprayer (600PSI) the outside did not cause my wings to leak.  I know this because the last time I did tank repairs I hosed out the wing tanks as well as the surface of the wings. In less than hour I was into the outboard wing reconnecting the outer sending unit. No water to be seen anywhere inside wing. It's conceivable that it is entering through the bottom wing skins during flight, but again no evidence.

I have flown in rain so heavy that the noise was competing with the engine/prop. I have had small amounts of water find its way past the firewall and even into the ventilation system, yet I have never seen evidence of water inside the wing. Not saying it does not happen. Just saying I have never seen visible evidence.  My apologies for suggesting something so obvious as verifying all aspects of the installation STC.  Given you are the only person that has ever raised this issue, I thought it might be tied to your particular installation.  Good luck. I hope you figure it out.

[FlyingDude]

@Shadrach thanks… i know you’re trying to help me.

water ingress is envisaged and accounted for: that’s why they put all those drain holes… it could be entering from anywhere… 

last summer I applied corrosion x. Tons of it sept through all sorts of joints. And it was puddling at the same spot, outboard of the extended tank. I’d clean all of it and I’d still find more a few days later.  That’s actually what prompted me to check the bays this time…

 

 

 

[Fly Boomer]

5 hours ago, Shadrach said:

Do you have the Monroy Aerospace upgrade below? Have you contacted them for advice?  I believe there have been several different shops acting as installers of this STC since it was approved in the 80s. Not hard to imagine that there might be inconsistencies in those installations.  First thing I would do is verify that the installation complies precisely with the STC. It seems to me that drainage would have been a consideration during approval.

Did long range tanks in all Mooney models installed by José have the same layout?

[Shadrach]

9 minutes ago, Fly Boomer said:

Did long range tanks in all Mooney models installed by José have the same layout?

I don’t know for sure, but given that compartment and station had been deemed useable for the initial STC, I would not be surprised if it’s the same for all.

[PT20J]

I never thought about theses hole or their purpose before. It doesn't seem like they are intended to be drain holes; they are not at the lowest spots that water would accumulate. My first airplane lived outside for many years and I never noticed water in the wing. The cabin and tail (which also have a lot of skin lap joints) never leaked. Does Mooney put sealer on the lap joints before riveting skins?

[FlyingDude]

4 hours ago, PT20J said:

they are not at the lowest spots that water would accumulate

They are. Use an inclinometer app on your phone and measure the angle with the phone edge resting flat on the bottom skin at the holes. Fuel drains are at the lowest point with the plane parked and drain holes are at the lowest point in flight attitude.  

[PT20J]

I asked Frank Crawford (tech support) and Shana Weiss (manufacturing engineer) at Mooney about the holes. Neither knows why they are there. Frank speculated that they may be tooling holes since they didn't show up on the engineering drawings. He did confirm that Mooney does not use any sealant in the wing skin joints, so I guess it is just the tightness of the joint and the paint film that keeps water out.

Since most holes seem to be forward of the wing tanks, perhaps they are there to vent the wing in case of a tank leak. It wouldn't make sense to me to have water drains that are  not at the low spot when parked because many airplanes spend a lot more time tied down in the rain than flying in the rain.

 

 

[FlyingDude]

@PT20J I don't know what to tell you. My mechanic had mentioned keeping "drain holes clean" at our very first annual together. I follow you when you say that parking attitude is more adequate for drainage than flight attitude but while there's one single official flight attitude, parking attitude could be anything based on surface slope, amount of fuel, pucks' ageing, you name it. 

Anyway, thanks for trying to help out...

[Shadrach]

2 hours ago, PT20J said:

Since most holes seem to be forward of the wing tanks, perhaps they are there to vent the wing in case of a tank leak. It wouldn't make sense to me to have water drains that are  not at the low spot when parked because many airplanes spend a lot more time tied down in the rain than flying in the rain.

 

 

Bingo. I’ve been told by multiple Mooney mechanics and pilots over the years that these holes are to allow fuel that has leaked though the front wall of the tank to vent from the wing structure. That’s exactly what it does. Indeed there are scenarios where fuel at the drain hole is the only external evidence of a leak.

[Igor_U]

2 hours ago, PT20J said:

I asked Frank Crawford (tech support) and Shana Weiss (manufacturing engineer) at Mooney about the holes. Neither knows why they are there. Frank speculated that they may be tooling holes since they didn't show up on the engineering drawings. He did confirm that Mooney does not use any sealant in the wing skin joints, so I guess it is just the tightness of the joint and the paint film that keeps water out.

Since most holes seem to be forward of the wing tanks, perhaps they are there to vent the wing in case of a tank leak. It wouldn't make sense to me to have water drains that are  not at the low spot when parked because many airplanes spend a lot more time tied down in the rain than flying in the rain.

 

 

Skip,

Are you referring to the hole in the removable access panels? tooling hole is a reasonable explanation, I also use them to hook in a piece of the wire and hold them down when re-installing the panel.

As for lack of Fay surface seal on skin laps and ribs; if they used it our integral fuel tanks would not leak. 

[PT20J]

2 minutes ago, Igor_U said:

Skip,

Are you referring to the hole in the removable access panels? tooling hole is a reasonable explanation, I also use them to hook in a piece of the wire and hold them down when re-installing the panel.

As for lack of Fay surface seal on skin laps and ribs; if they used it our integral fuel tanks would not leak. 

In addition to the small holes in the access panels, there are some ~1/4” holes in the lower inboard skins a few inches back from the leading edge. 

[Igor_U]

15 minutes ago, PT20J said:

In addition to the small holes in the access panels, there are some ~1/4” holes in the lower inboard skins a few inches back from the leading edge. 

Yes, I always considered those as fuel vent/drain holes...

[FlyingDude]

42 minutes ago, Shadrach said:

these holes are to allow fuel that has leaked though the front wall of the tank to vent from the wing structure.

I disagree. There are 1/4” holes in each bay forward of the spar. Leaked fuel doesn’t move against gravity towards the wing tip. 

Aft of the spar, the ribs have a crescent cut-out for the stringer. All fluids drain along that stringer which happens to be at the low point of the wing profile and there’s only 1 drain hole at the lowest bay, right next to the gear… there’s no such stringer river forward of spar, so you can’t rely on water transfer into lower bays. That’s why those bays have their individual holes.

access panels can also have some fluid due to the joggle that makes them into a pool. The pinholes are for that.

i think the opening for the aileron pushrod is plenty huge for pressure equalization.

 The extended tank interrupts the river along the stringer by plugging the crescent cutout in the rib…

 

[Shadrach]

1 hour ago, FlyingDude said:

I disagree. There are 1/4” holes in each bay forward of the spar. Leaked fuel doesn’t move against gravity towards the wing tip. 

Aft of the spar, the ribs have a crescent cut-out for the stringer. All fluids drain along that stringer which happens to be at the low point of the wing profile and there’s only 1 drain hole at the lowest bay, right next to the gear… there’s no such stringer river forward of spar, so you can’t rely on water transfer into lower bays. That’s why those bays have their individual holes.

access panels can also have some fluid due to the joggle that makes them into a pool. The pinholes are for that.

i think the opening for the aileron pushrod is plenty huge for pressure equalization.

 The extended tank interrupts the river along the stringer by plugging the crescent cutout in the rib…

 

The holes are located just ahead of the the front tank wall. There are numerous cases of fuel weeping from them including threads started on this forum and in my personal experience. Just providing information. Agreement is not required.

[FlyingDude]

Got any pictures showing fuel leaking from the outboard holes forward of the spar?

Water gets into the wings. Whether you admit it or not...

[Shadrach]

On 1/9/2024 at 7:27 PM, FlyingDude said:

Got any pictures showing fuel leaking from the outboard holes forward of the spar?

Water gets into the wings. Whether you admit it or not...

No one is disputing that water has breached your wings. It’s not personal. It seems you want us alll to admit we have a water problem too even though none of us has seen any evidence of water in our wings.