Strut collapsed

[murphey]

Finally, two days free of work and great weather. Friday lunch, I headed to the hangar, stepped up on the starboard wing of the cherokee....clunk. big CLUNK! The port strut completely collapsed. Ok, so I'm not going flying today. May as well update the 175 database and load the car with the Young Eagle stuff we hand out.

Shop is closed until Monday, altho I did leave a voice mail.

My ignorant estimate is the seals failed in the strut. But I won't know until the shop pulls it into their hangar and figures it out.

rats.

 

[Doc Holliday]

Finally, two days free of work and great weather. Friday lunch, I headed to the hangar, stepped up on the starboard wing of the cherokee....clunk. big CLUNK! The port strut completely collapsed. Ok, so I'm not going flying today. May as well update the 175 database and load the car with the Young Eagle stuff we hand out.

Shop is closed until Monday, altho I did leave a voice mail.

My ignorant estimate is the seals failed in the strut. But I won't know until the shop pulls it into their hangar and figures it out.

rats.

Any fluid on the floor from the strut failure?

 

[murphey]

Any fluid on the floor from the strut failure?

Hm....didn't notice anything but wasn't looking specifically for fluid. All the tires sit on heavy duty foam, which have water stains on them, so unless I'm looking, I wouldn't notice any other discolorations. I'll check tomorrow if I get out there.

 

[Doc Holliday]

Hm....didn't notice anything but wasn't looking specifically for fluid. All the tires sit on heavy duty foam, which have water stains on them, so unless I'm looking, I wouldn't notice any other discolorations. I'll check tomorrow if I get out there.

If you don't see fluid on the floor, it may have lost pressure through the Schrader valve. Typically when a seal blows on the oleo it releases the fluid.

 

[Magman]

Flying with a flat strut is never good; but on a retract the wheel may not

fit in the well and bend linkage.

 

[aterry1067]

Just curious…has it suddenly become much cooler where you are located? As in, has ambient dropped 30 degrees or more in the last week or so?

 

[murphey]

Just curious…has it suddenly become much cooler where you are located? As in, has ambient dropped 30 degrees or more in the last week or so?

Still in the 80s during the day, going down into the 50s at night. But this is the first time in over 20 years it's happened. I expect the tires to be a bit flat but not the entire strut collapsing. It's gone down to 2-3 inches at times (4 in is the minimum as per the Cherokee specs) but never to zero! I'll grab a photo tomorrow if I get out there.

 

[aterry1067]

Still in the 80s during the day, going down into the 50s at night. But this is the first time in over 20 years it's happened. I expect the tires to be a bit flat but not the entire strut collapsing. It's gone down to 2-3 inches at times (4 in is the minimum as per the Cherokee specs) but never to zero! I'll grab a photo tomorrow if I get out there.

Thanks. As stated by Doc, if there’s no fluid loss, then it just lost air pressure. Pump it up and go fly. Just be aware that something caused it to lose pressure. When you service it back up, take a spray bottle of water and a couple spoonfuls of dish detergent and spray around the valve and elsewhere; see if you can find a leak.

It could very well be the orings on the schrader valve, or the valve core could have worked it’s way loose…simple fix.

 

[murphey]

Thanks. As stated by Doc, if there’s no fluid loss, then it just lost air pressure. Pump it up and go fly. Just be aware that something caused it to lose pressure. When you service it back up, take a spray bottle of water and a couple spoonfuls of dish detergent and spray around the valve and elsewhere; see if you can find a leak.

It could very well be the orings on the schrader valve, or the valve core could have worked it’s way loose…simple fix.

Great idea but I have nothing to pump it up with and second….defintely don’t want to land and have this happen….don’t need the it going thru the wing.

 

[Domenick]

If you replace the schrader valve, the aluminum washer under the valve MUST be replaced with new.

It could very well be the orings on the schrader valve, or the valve core could have worked it’s way loose…simple fix.

Do you mean those teeny-tiny o-rings on the valve core?
Good idea to check the valve core is tight. Sometimes a bit of silicone grease on the valve core will help seal.

 

[Dan Thomas]

Most likely the strut is sticky, and the pressure slowly bled away past the valve's gasket or its core or past the O-ring on the slug at the top of the cylinder. Once you climbed on the wing and disturbed it, it unstuck and collapsed.

 

[Gary Ward]

Might try pumping it back up and then see what you have in 24 hrs? 48 then 72 or something and see if it leaks out before you fly it?

 

[Gary Ward]

I don’t know if this means anything ?

When I first got my 172 one day when I opened hangar the front strut was flat. I pumped it up with an air compressor, it doesn’t take much air.
The next day it was flat again. I was seriously bummed and ordered the strut rebuild kit.

But first I got my nitrogen tank from my race shop and filled it again. The next day it was still up and the next and the next and it was still up. Then I flew it and it was up when I landed. This was in 2018 and I am still flying it without rebuilding it. 1000+ hours later I add nitrogen in the fall early winter once a year. It has never gone all the way flat since I used nitrogen. I can tell when it needs a little and it actually lasts longer than 1 year.

Our bicycles tires last longer with nitrogen I have proven over and over.

Might help you, might not?

Good luck with it. I realize a main might be more important than a front strut on a Cessna.
Like some one said, leak test bubbles are your friend.

 

[Magman]

Cherokee Main struts have much more pressure than a Cessna nose strut.

Many compressors will have little effect if strut is compressed.

It is possible there was no fluid in the strut

As was said; my call would be to service and check for leaks at Shrader

valve. They may be VERY small and slow.

If you are unsure of last service I would do all.

 

[RyanB]

I’ve had that happen before. Not to say with certainty, but the strut may have to get rebuilt, as it did in my case. Not the end of the world - the kit is like $20 and about 4hrs labor. It could be as simple as some of the suggestions above, however!

 

[Gary Ward]

I have always removed the weight before pressurizing the strut.

I get it, you don’t know what you got when you start. Best to cover all “bases”

 

[NordicDave]

Others have mentioned compressed air... check your service manual which likely specifies nitrogen and for good reason. Also lowering the tail to fully extend the nose is usually required to get the oleo tube sufficiently charged. Follow the service manual.

 

[aterry1067]

Others have mentioned compressed air... check your service manual which likely specifies nitrogen and for good reason. Also lowering the tail to fully extend the nose is usually required to get the oleo tube sufficiently charged. Follow the service manual.

The service manual doesn’t specify other than a “strut pump” or a “high pressure air system.”

General practice is to use nitrogen or dry shop-air. The main thing is to ensure the air is dry, which is the main reason to use nitrogen. It would be good practice to do a complete strut service at annual, to include fluid flush and replacement. If an owner were to actually follow that, standard compressed air would be fine, as any accumulated moisture would be flushed out along with the old fluid. Strut fluid gets nasty fast, mostly from contaminants introduced past the wiper seal every time the strut compresses. This is, of course, assuming the airplane flies and doesn’t just sit.

 

[Domenick]

A Cherokee on the ground will need about 450 psi to inflate a main strut. Lifted off the ground it will take about 125 psi.

I keep a high-pressure mountain bike pump in my baggage bin: https://www.amazon.com/gp/product/B00D0SFMJS/
There are other brands that provide even higher pressure.

A schrader valve adapter will be useful. They are available from other places rather than Amazon.

Amazon.com

 

[aterry1067]

A Cherokee on the ground will need about 450 psi to inflate a main strut. Lifted off the ground it will take about 125 psi.

I keep a high-pressure mountain bike pump in my baggage bin: https://www.amazon.com/gp/product/B00D0SFMJS/
There are other brands that provide even higher pressure.

A schrader valve adapter will be useful. They are available from other places rather than Amazon.

Amazon.com

That is exactly the same pump that I carry. It works great. I pump it up to about 250psi and rock the wing. The strut extends a little bit and the pressure reduces. Repeat until desired x-dimension/extension is achieved.

 

[NordicDave]

Check with your local FBO to use their nitrogen tank. Probably pretty cheap. These tanks are under 2000 psi and have a PSI adjustable regulating valve. Compressed shop air or via a hand pump will have water as a byproduct which can introduce internal corrosion.

 

[mandm]

A Cherokee on the ground will need about 450 psi to inflate a main strut. Lifted off the ground it will take about 125 psi.

I keep a high-pressure mountain bike pump in my baggage bin: https://www.amazon.com/gp/product/B00D0SFMJS/
There are other brands that provide even higher pressure.

A schrader valve adapter will be useful. They are available from other places rather than Amazon.

Amazon.com

Should I carry one of these pumps in the baggage compartment?

 

[Doc Holliday]

If the struts are maintained, and filled with nitrogen, then why have to carry a pump?

 

[aterry1067]

If the struts are maintained, and filled with nitrogen, then why have to carry a pump?

Because strut seals are wear items, and because of post #1. That would have sucked a lot more if it had happened at a fuel stop in the middle of nowhere, and no pump.

 

[Doc Holliday]

Because strut seals are wear items, and because of post #1. That would have sucked a lot more if it had happened at a fuel stop in the middle of nowhere, and no pump.

OK. Some of us never had this problem.

Curious, do you carry extra tires and tubes, alternator belt and alternator brushes? Those are wear items as well.

 

[mandm]

OK. Some of us never had this problem.

Curious, do you carry extra tires and tubes, alternator belt and alternator brushes? Those are wear items as well.

I had a flat tire after landing and the tire was swapped out, but now I’m wondering if it just needed air.

I carry an extra tube, oil and oil filter.

 

[aterry1067]

OK. Some of us never had this problem.

Curious, do you carry extra tires and tubes, alternator belt and alternator brushes? Those are wear items as well.

No. Alternator belt and tires are inspected every preflight. Tubes are inspected/replaced with every tire change. Alternator brushes inspected at annual.

I understand the problem hasn’t happened to many, probably most. But your earlier post said “a well maintained strut…” I’m willing to bet that there is a large overlap of “it’s never happened to me” and “I’ve never overhauled my struts” and likely “I’ve never flushed my struts with clean fluid and reserviced them with clean fluid and nitrogen.” which would imply that most struts out there aren’t properly maintained. And if that’s the case, then carrying a tiny pump is not a bad idea, if it gets one out of a jam and back home.

 

[brcase]

I don’t know if this means anything ?

When I first got my 172 one day when I opened hangar the front strut was flat. I pumped it up with an air compressor, it doesn’t take much air.
The next day it was flat again. I was seriously bummed and ordered the strut rebuild kit.

But first I got my nitrogen tank from my race shop and filled it again. The next day it was still up and the next and the next and it was still up. Then I flew it and it was up when I landed. This was in 2018 and I am still flying it without rebuilding it. 1000+ hours later I add nitrogen in the fall early winter once a year. It has never gone all the way flat since I used nitrogen. I can tell when it needs a little and it actually lasts longer than 1 year.

Our bicycles tires last longer with nitrogen I have proven over and over.

Might help you, might not?

Good luck with it. I realize a main might be more important than a front strut on a Cessna.
Like some one said, leak test bubbles are your friend.

I have nitrogen tank left over from my previous glider that had hydraulic struts. I think I used it maybe twice in the 20 years I owned the glider.

Good idea I should try pumping up the glider tire it needs pumped up about twice year, and maybe the bicycle tires as well.

Brian

 

[Domenick]

...Check with your local FBO to use their nitrogen tank. Probably pretty cheap. These tanks are under 2000 psi and have a PSI adjustable regulating valve. Compressed shop air or via a hand pump will have water as a byproduct which can introduce internal corrosion.

No offense Dave, and I'm not trying to start an argument. No doubt cylinder N2 is drier than ambient air and contains 100% N2 as opposed to ambient air which contains 78%.

I've heard this criticism of using ambient air versus nitrogen for years and years. I've never seen any evidence the minute quantity of water present in the tiny volume of the strut has any effect. After 20+ years of using only air in my struts, when one main seal failed, I rebuilt them both. Internals were pristine. When I rebuilt the nose strut, same thing, pristine.

... Curious, do you carry extra tires and tubes, alternator belt and alternator brushes? Those are wear items as well.

I carry an alternator belt.

 

[Magman]

Some Lycoming folks secure an Alternator Belt to the Crankcase behind the Prop.

Especially with Constant Speed Props.

I have questioned w hat condition they would be in if actually needed.

An extra spark plug and torque wrench would be items I might carry.

 

[NordicDave]

No offense Dave, and I'm not trying to start an argument. No doubt cylinder N2 is drier than ambient air and contains 100% N2 as opposed to ambient air which contains 78%.

I've heard this criticism of using ambient air versus nitrogen for years and years. I've never seen any evidence the minute quantity of water present in the tiny volume of the strut has any effect. After 20+ years of using only air in my struts, when one main seal failed, I rebuilt them both. Internals were pristine. When I rebuilt the nose strut, same thing, pristine.


I carry an alternator belt.

I appreciate your perspective Domenick. For me... Cessna explicitly specifies nitrogen and it's required for my plane, if I want the log entry to state "serviced as per factory maintenance manual". For the benefit of others... Nitrogen molecules are larger and less prone to leakage and temperature changes. I've been using it not only in the strut, but also all three tires.

I bought a mid sized Nitrogen tank 5 years ago and have since regularly serviced my truck and plane with it, not to mention most of the planes on my end of the airport. Made a lot of friends with that tank of gas. Time is up for the hydro static test and refill. The local welding shop wants $35 to trade it out for new full bottle.

 

[murphey]

Shop pumped up the strut, left it for 2 days then took it for a test flight (I was at work, couldn’t get away) and looks like everything is fine. I like a shop that’s willing to put skin in the game. I’ll head out tomorrow and try it out.

 

[Domenick]

Some folks secure an Alternator Belt to the Crankcase behind the Prop.

Especially with Constant Speed Props.

I have questioned w hat condition they would be in if actually needed.

An extra spark plug and torque wrench would be items I might carry.

My spare alternator belt lives in the baggage bin.
I also carry spare spark plugs, wrenches (including torque), and more. Since I fly almost exclusively solo, I keep a full toolbox in the baggage compartment (passenger side) weighing 40 lbs. It also helps set the CG back a smidge.