Broken Cessna Wing Strut?

[JayAlarm]

I want to really get rid of this irrational fear that is always on my mind when I am up in the air. I have not read anywhere about a wing strut failing on a Cessna, but what is the outcome if a strut were to fail? This is obviously not going to have any positive outcome right? I know this is a ridiculous question too

 

[JeppUpdater]

I've not dealt with the smaller ones, but on the 206/208 the strut is two C-channels back to back, each capable of supporting the max wing loading individually, attached at both ends with heavy duty bolts. The attachment points themselves are probably 5/8"-3/4" thick on both sides of the strut which is an inch give or take.

In simple terms - the tail will snap off before you over stress the wing enough for the strut to let go.

 

[RDoug]

Translation: You're worrying about the wrong part. It's the tail that's going to kill you!

Sorry. Couldn't resist. I'll go back to my room now.

 

[Cessnaflyer]

It's running into the trailing edge of the wing doing a walk around that's going to kill you. Or smashing your head against the prop after sumping the fuel from the nose.

 

[Roger Roger]

I've not dealt with the smaller ones, but on the 206/208 the strut is two C-channels back to back, each capable of supporting the max wing loading individually, attached at both ends with heavy duty bolts. T.

Correct about the 208, incorrect for all other strut braced cessnas. I'm busy ATM but as an IA maintaining 8 Cessnas I've got some good input on this.

 

[Hacker15e]

Take a look behind you at the horizontal stab and the vertical stab when you're doing stalls or MCA flight.

That will completely erase any worry you have about the wing struts being a potential failure point.

 

[mshunter]

If the wing strut breaks, it's certain death! Usually because the rest of the airframe came apart first.

 

[JayAlarm]

Take a look behind you at the horizontal stab and the vertical stab when you're doing stalls or MCA flight.

That will completely erase any worry you have about the wing struts being a potential failure point.

Well as my concern is generally the plane coming apart, what kind of stresses can you put on the vertical stabilizer and elevator then...?

 

[mshunter]

Well as my concern is generally the plane coming apart, what kind of stresses can you put on the vertical stabilizer and elevator then...?

A LOT! You'd have to try to get the thing to come apart.

 

[JayAlarm]

A LOT! You'd have to try to get the thing to come apart.

Thanks. I seem to be the only one in the world with this concern. I watch so many damn videos of GA flying on YouTube and nobody seems concerned in the slightest.

 

[Roger Roger]

I've not dealt with the smaller ones, but on the 206/208 the strut is two C-channels back to back, each capable of supporting the max wing loading individually, attached at both ends with heavy duty bolts. The attachment points themselves are probably 5/8"-3/4" thick on both sides of the strut which is an inch give or take.

In simple terms - the tail will snap off before you over stress the wing enough for the strut to let go.

Just some numbers pulled from the Internet for funsies: the shear strength of the 7/8" NAS close tolerance bolt used at the upper end of the Caravan lift strut is about 57,000 lbs (based on the published 95000 psi shear strength). The 3/4" bolt at the bottom is a little less, about 41,000 lbs. Both joints are designed so that the bolt is in shear in multiple places-in other words in an ideal environment the bolts can stand on the order of 110-120,000 lbs of shear forces on the joint. *edit* I'm just an IA, not an engineer, but I think I did my math right. This is a little more @inigo88 's forté.

On the other 200 series Cessnas (actually, I think all the other strut-braced Cessnas) the lift strut is much less robust, just a heavy duty aluminum fitting at each end bolted to the strut which carries all its load through the streamlined tubing vs the back to back u-channels with a non-structural streamlined fairing on the Caravan. I've still never heard of one breaking short of major inflight loss of control or impact with terrain.

Take a look behind you at the horizontal stab and the vertical stab when you're doing stalls or MCA flight.

That will completely erase any worry you have about the wing struts being a potential failure point.

It is true that the tail is the section of aircraft where we generally find fatigue damage first in propeller GA land. I made the mistake once of watching the horizontal of the Navajo while doing power on stalls. NEVER. AGAIN. However, in the little skimming I've done of in flight breakup accident reports in an overload situation a wing or portion of a wing seems to generally be the first to go at least on small GA.

Well as my concern is generally the plane coming apart, what kind of stresses can you put on the vertical stabilizer and elevator then...?

As others have said, you have to have either serious upset (like complete spatial disorientation or full-on monster thunderstorm encounter) or intentional maneuvering to break these aircraft. For the most part primary structure is absurdly overbuilt and even after decades and 10s of thousands of hours they retain an astonishing amount of structural integrity.

Thanks. I seem to be the only one in the world with this concern. I watch so many damn videos of GA flying on YouTube and nobody seems concerned in the slightest.

There are a very few niches of GA where structural failure is a legitimate worry. One is aerobatics, especially aerobatics done by untrained hacks in non-aerobatic aircraft (one reason I lose my bananas whenever someone opines that it's pretty neato to go do rolls in the flight schools 172). Another is certain series of aircraft that have known design weaknesses or aging issues, a prime example being the Pipers and Tailorcrafts with lift struts-they lost a few aircraft due to internal rust in the lift struts before the AD was issued. It should not be a problem anymore because of the inspection requirements and because so many have been replaced with better struts but still something to be cognizant of.

 

[lightspeed]

I watch so many damn videos of GA flying on YouTube and nobody seems concerned in the slightest.

Loss of control is currently the #1 cause of general aviation accidents according to the NTSB.

Between 2008 and 2014, about 47 percent of fatal fixed-wing GA accidents in the United States involved pilots losing control of their aircraft in flight, resulting in 1,210 fatalities.

I sometimes thought it was overkill how much we spent teaching stall recognition, awareness, and recovery to brand new pilots. Some guy is just getting into an airplane and getting a handle of it, and now we're going to send him right into stall training. Or how we expected them to handle steep turns and slow flight. The unfortunate reality is that while you're worried about regularly inspected spars failing, the vast majority of fatalities occur when a perfectly airworthy airplane impacts the ground (either under control, or most often out of it).

At some point we have to be realists about our fear, and use it to help save our lives. Departing controlled flight at low altitude is very scary to me.

 

[JayAlarm]

Loss of control is currently the #1 cause of general aviation accidents according to the NTSB.


I sometimes thought it was overkill how much we spent teaching stall recognition, awareness, and recovery to brand new pilots. Some guy is just getting into an airplane and getting a handle of it, and now we're going to send him right into stall training. Or how we expected them to handle steep turns and slow flight. The unfortunate reality is that while you're worried about regularly inspected spars failing, the vast majority of fatalities occur when a perfectly airworthy airplane impacts the ground (either under control, or most often out of it).

At some point we have to be realists about our fear, and use it to help save our lives. Departing controlled flight at low altitude is very scary to me.

I agree with that completely. I don't think you should be teaching stalls under 20hrs especially. I think getting comfortable with the plane really takes much longer than that - at least I know that it is going to take me more than 20 hours to get any comfort whatsoever

 

[Roger Roger]

Oh and to answer your original question when a lift strut does depart the result is invariably and unavoidably fatal.

 

[lightspeed]

I don't think you should be teaching stalls under 20hrs especially.

My personal rule is that I won't allow a student to handle the flight controls below 1000' unless they have demonstrated to me proper stall entry, recognition, and recovery. Is it possibly overwhelming to teach this stuff so early? Probably.

Is it essential to build a strong foundation early? I say yes. You'll learn more about how an airplane flies by regularly taking it to the edges of the aerodynamic envelope and back than anything else you can think of doing for 20 hours.

 

[NickH]

I agree with that completely. I don't think you should be teaching stalls under 20hrs especially. I think getting comfortable with the plane really takes much longer than that - at least I know that it is going to take me more than 20 hours to get any comfort whatsoever

Solo before 20 hours is not unreasonable or uncommon. Everyone learns at a different pace, of course.

 

[JayAlarm]

Solo before 20 hours is not unreasonable or uncommon. Everyone learns at a different pace, of course.

Well my irrational fear continues anyway. I will just fly with a clenched ass and tense shoulders and hope that wing stays put...

 

[JeppUpdater]

Correct about the 208, incorrect for all other strut braced cessnas.

The 208 I was intimately familiar with, the 206 I copied that straight out of the flight controls PowerPoint for new hires.


Annnnnd...pandora's box opens...

Thanks Roger.

 

[CFI A&P]

If wing strut failure bothers you, may I suggest these two things for you: Piper and Beechcraft.


Sent from my iPhone using Tapatalk

 

[USMCmech]

Well my irrational fear continues anyway. I will just fly with a clenched ass and tense shoulders and hope that wing stays put...

As everyone said, the wing will probably be the LAST part of the airframe to fail.


This is what happens past Vne