marky_24

Mooney spar design

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After reading the preliminary report on the ERAU Arrow wing separating, it got me wondering what the Mooney spar and wing look like. I'm not worried about my wing falling off, just curious. Does anyone have any pictures of a wing without skins, or a drawing?

 

https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20180404X13226&AKey=1&RType=HTML&IType=FA

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There’s about 15x more rivets and metal holding the wing on a Mooney than a Piper.  And the mooney wing has a rear stub spar while the Piper does not. 

Edited by jetdriven

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At Oshkosh last summer, during a presentation, a Mooney’s company staff mentioned that sometime in the past, they tested the wing with 20000 pounds on the wing and it would still hold.

Yves

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Somewhere around here (or elsewhere) is a drawing/ad of what a Mooney looks like as if the skin were removed...  aka a cut-away view.

Kind of an 90’s drawing technique where cadcam (or other) made removable layers popular...

Anyone remember this fancy Mooney drawing?  Possibly a long body showing where all the major systems are located...

 

There is also some pics of Grimmy the reaper, cutting up an M20E last year.  One pic shows a dozen or so East Coast Mooniacs standing on the wings....

Not quite the same as another Mooney ad where 20 or so Mooney employees were sitting on the wing of a new plane.

The story from the factory early on...  they tested the strength of the wing, until the test rig failed....

Mooney provides a few drawings in the maintenance manual that may be worth seeing...

 

All this discussion about the main wing...  not much mentioned about the other wing.... you will need both to fly successfully...  Look up Brand B for dissertations on failures of the other wing...

 

Amazing how strong and light a Mooney actually is...

There is one known Mooney that bent its wings flying in/near thunderstorm activity(?).  Pilot landed well.  Plane was not useable without significant repairs...

Wings falling off are not the usual challenge for Mooneys.  There are yellow zones on the ASI that indicate speed limits, by weight, that help keep that from happening...  be familiar with maneuvering speed.  

Good news... the wings didn’t bend....  bad news... the wing stalls instead, the wild ride has just begun....

Flying into icing conditions and thunderstorm activity are best to be avoided.  Like VFR into IMC....

PP ideas only, not a CFI...

Best regards,

-a-

 

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Nothing like the Piper.   The Piper is a three piece design.  The mooney wing is a single piece design.   It the main spar starts in the middle then goes out to the wing tips.

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Reading the accident report... it appears the accident flight didn’t have anything to do with the broken wing spar of the Erau plane....

Something probably happened to it somewhere along the way..... not in the report...

See if there is a final report on that somewhere...

PP thoughts only

Best rgeards,

-a-

 

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The Arrow had over 7,600 airframe hours, which is not a lot for a GA trainer with evidence of fatigue within the structure of the wing root area.  It will be interesting to read about the past history of this aircraft.  

I can see an AD release in the future for Piper wing inspections.

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here is a picture of the center wing with the spar sticking out both sides. It is a little hard to see. The yellowish green is the spar. 

IMG_0024.JPG

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This Piper had over 7,000 hrs of hard landings. That is more than twice the average of old Mooneys. Aside from the wing spar the Mooney also has the structural steel tubing in the fuselage that helps on carrying the load.

José

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I know the Mooney wing is a great wing,  I just like knowing about these things. Like I am surprised at the Piper spar. Basically just a formed "T" shape. What does the Mooney  spar look like? "I" beam shaped? 

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Take a look under the rear seat coverings....

Your kids are kicking it, spilling soda on it, and generally not knowing what they are sitting on... :)

you might even recognize the yellow paint from the above pic...

under the rug is the splice plates... often victims of the same soda, sand, and other dirt...

It is hard to get corrosion to start, but when it does, it can spread quickly and deeply.  

If the anti-corrosion coating is coming off, it is pretty easy to get it resprayed.  Check in with your mechanic for this...

 

PP experience from a 65C...

Best regards,

-a-

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Piper issued a SB a few months ago, basically adds more inspection openings to inspect the spar.....I know the Cherrokees were included but not sure which others

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Marky,

Nice work finding that drawing...

The main spar is pretty much an I beam with continuously changing dimensions...

All the important stuff is attached to the spars...  in the drawing, the back spar is where things like flaps and speed brakes(?) are often attached.

Mix the drawing with the pic of the actual wing above...

You will see the Center splice that has a bunch of rivets in it... That is where the left wing and right wing come together in one ‘solid’ piece.  The splice is a stack of pieces for added strength...

Compare all that to what you see under your rug in the back seat...

PP thoughts only, not a mechanic...

Best regards,

-a-

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I've still got a center section at my hangar...I'll try to remember to take some pics on Friday when I plan to fly next...

Sent from my LG-US996 using Tapatalk

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Here's a close-up of the center section I took at Paul's salvage hangar in Lakeport:

IMG_1644.thumb.jpg.bbafe0445220c6a082c1a135e553baa8.jpg

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There’s a picture from someone’s Mooney factory tour somewhere with a picture of a jig. 

I am never worried about the strength of the mooney wing. Something else may fail but it won’t be the wing.  

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23 minutes ago, bradp said:

I am never worried about the strength of the mooney wing. Something else may fail but it won’t be the wing.  

It has been shown to usually be the loose nut behind the yoke . . . .

Strength of design is one of the (several) things I really like about my Mooney.

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The inner portion of the Piper wing is an aluminum “I” beam, further out it transitions to riveted aluminum structure.

Piper wings have a rear spar, just like a  Mooney.

Piper wings have a front attachment fitting, just like a Mooney.

Piper wings are subject to fatigue and corrosion just like a Mooney.

Pray that your spars aren’t corroded inside your fuel tanks like we’ve seen here, they could fail just as easily.

Not all of its flights resulted in a hard landing, just like your landings, not all are hard.

From the picture above you can see that the Mooney spar is not one piece from tip to tip as many here believe.  It is assembled from many different pieces all fastened together with hundreds upon hundreds of fasteners.  The butt end of the main spars are joined with several splice plates which are under the aft seat, take the plates off and you have 2 separate spars.

Clarence

Edited by M20Doc
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7 hours ago, marky_24 said:

I know the Mooney wing is a great wing,  I just like knowing about these things. Like I am surprised at the Piper spar. Basically just a formed "T" shape. What does the Mooney  spar look like? "I" beam shaped? 

What you see on that picture is just a T shape Wing spar cap that failed, not the whole spar. Spar is build up "I" beam (upper and lower caps plus web) similar to Mooney's and you can see it on the Isometric view attached to the report. Wing shapes are, of course different with early PA28 having Hershey bar wing while later one have outboard portions of the wings tapered.

Similarly to Mooney, PA28 have laminar wing profile so the main spar is at maximum airfoil thickness (40% of the chord) and passes aft of the pilot's seats.

I'd be interesting to read the final accident report and more about history of the aircraft. Making a left crosswind definitely didn't break the spar; previous flights did.

 

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2 minutes ago, Igor_U said:

What you see on that picture is just a T shape Wing spar cap that failed, not the whole spar. Spar is build up "I" beam (upper and lower caps plus web) similar to Mooney's and you can see it on the Isometric view attached to the report. Wing shapes are, of course different with early PA28 having Hershey bar wing while later one have outboard portions of the wings tapered.

Similarly to Mooney, PA28 have laminar wing profile so the main spar is at maximum airfoil thickness (40% of the chord) and passes aft of the pilot's seats.

I'd be interesting to read the final accident report and more about history of the aircraft. Making a left crosswind definitely didn't break the spar; previous flights did.

 

There was a vendor at Sun N Fun from Alaska, who had the butt end of a PA32 Cherokee 6 spar with the same crack.  He was a fleet operator who had found similar cracks when re-skinning a wing on a much higher time airframe.  I’m guessing that Alaska airframes lead a tougher life than a trainer in Florida.

Clarence

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Cherokees have ben flying for half a century, many if not most in a primary flight training role.  They do not routinely fall out of the sky.  I can't imagine what Embry Riddled did to that poor thing, but I must have seriously rude.

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14 minutes ago, steingar said:

Cherokees have ben flying for half a century, many if not most in a primary flight training role.  They do not routinely fall out of the sky.  I can't imagine what Embry Riddled did to that poor thing, but I must have seriously rude.

Or it was a single missed manufacturing or material defect that manifest itself over time.

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