wing strength

[Jeff Reiter]

I saw an old picture of a Mooney m20c with about 20 people standing on the wing, showing the extraordinary strength of the money wing. So why is 140 miles per hour the limit for speed in rough air? this makes no sense to me. if it has a strong wing, then why isn't the speed more like 175 miles an hour for rough air?

[KSMooniac]

The tail might not be strong enough to go faster...

Sent from my LM-V405 using Tapatalk

[philiplane]

yep. Tail comes off first.

[Hank]

10 minutes ago, Jeff Reiter said:

So why is 140 miles per hour the limit for speed in rough air? 

In my C, it's 132 mph.

[N201MKTurbo]

Has a tail ever come off?

[N201MKTurbo]

I believe the limiting speeds have more to do with control flutter than strength. But that doesn't explain the top of the green.

We need @Blue on Top to chime in on how these speeds are calculated.

[cbarry]

I believe a long body has had a tail separation due to a tail trim pitch assembly failure on an M20TN, but that’s the only one I’ve ever heard of.  I believe it was determined that there was a mishap in assembly versus design failure.  This resulted in an AD for certain serial numbers...to inspect for proper assembly.

[Hank]

50 minutes ago, N201MKTurbo said:

Has a tail ever come off?

Seems I recall reading about a poor soul whose Mooney hit a T-cell. He was spit out, made an emergency descent and precautionary landing somewhere in IL. His wing spar was bent, a lot of skin rivets were pulled through, but he made it safely down and had a normal landing. Nothing actually fell off the airplane, just bent and twisted. The plane, though, was totalled . . . . .

Edited August 29, 2020 by Hank

[Guest]

I believe that all of the tails are held on by the same two 1/4” diameter bolts.

Clarence

[Prior owner]

Regarding VNE: There’s more than the wing- sometimes it is something as simple as the windshield collapsing at a certain airspeed.

Edited August 29, 2020 by PilotCoyote

[Rwsavory]

1 hour ago, Jeff Reiter said:

I saw an old picture of a Mooney m20c with about 20 people standing on the wing, showing the extraordinary strength of the money wing. So why is 140 miles per hour the limit for speed in rough air? this makes no sense to me. if it has a strong wing, then why isn't the speed more like 175 miles an hour for rough air?

You’re describing a static load. When you are traipsing through the atmosphere, things aren’t so simple.  I’m neither an aeronautical engineer nor a mathematician, but, intuitively, I know the difference.  For those versed in these disciplines, this treatise might be instructive:

[jlunseth]

Lore has it that only one Mooney has had the tail separate in flight, in convection and before the TN incident mentioned above. Bruce Jaeger, who is definitely a Mooney historian, told me there have been two or three.  But what a record for an aircraft. Typical in the old days was for someone to blunder into a t-storm and come out in pieces.  Mooneys might get bent up pretty good, but coming out in pieces is not the Mooney way.

[M016576]

3 minutes ago, jlunseth said:

Lore has it that only one Mooney has had the tail separate in flight, in convection and before the TN incident mentioned above. Bruce Jaeger, who is definitely a Mooney historian, told me there have been two or three.  But what a record for an aircraft. Typical in the old days was for someone to blunder into a t-storm and come out in pieces.  Mooneys might get bent up pretty good, but coming out in pieces is not the Mooney way.

After seeing a couple of “rockets/missiles are dangerous; the airframes can’t handle that power/mod!” Posts here on mooney space, I did a (very) cursory look into in-flight break ups of Mooney’s on the inter webs.  I found 3.  2 were K’s, one was a C, if I remember correctly, one of the two K’s was a rocket.  I think that’s where the idea came from that the rocket was “more dangerous”
 

All 3 were in heavy convective turbulence (again, if I remember correctly)... I think the issue was not “what type of mooney” but “what were the conditions of flight.”

jmho.

[aviatoreb]

14 minutes ago, M016576 said:

After seeing a couple of “rockets/missiles are dangerous; the airframes can’t handle that power/mod!” Posts here on mooney space, I did a (very) cursory look into in-flight break ups of Mooney’s on the inter webs.  I found 3.  2 were K’s, one was a C, if I remember correctly, one of the two K’s was a rocket.  I think that’s where the idea came from that the rocket was “more dangerous”
 

All 3 were in heavy convective turbulence (again, if I remember correctly)... I think the issue was not “what type of mooney” but “what were the conditions of flight.”

jmho.

That one rocket break up - this is from a vague memory of reading about it many years ago - was an airplane in convective leading to loss of control and then dramatically overspending in a dive.  That can get any airplane in any fleet.

...and after typing that - I found this quickly on google - https://planecrashmap.com/plane/ca/N231BY/

[kortopates]

3 hours ago, Jeff Reiter said:

I saw an old picture of a Mooney m20c with about 20 people standing on the wing, showing the extraordinary strength of the money wing. So why is 140 miles per hour the limit for speed in rough air? this makes no sense to me. if it has a strong wing, then why isn't the speed more like 175 miles an hour for rough air?

So lets say it was 20 people per wing X2 and assume 150 lbs average per person - that's only 3000 lbs per wing totaling 6000 lbs

The Mooney like most every GA aircraft is certified to handle a positive load factor of 3.8 G's. With a Max gross weight of 2575 lbs. X 3.8 = 9,785 lbs! Clearly the wing has to hold up all that weight. 

So there is nothing remarkable about putting all those people on the wing, the weight is still well below certification requirements for any light GA plane. Nor does it relate directly to any of the V speeds other than saying you can exceed that 3.8 G limit  above maneuvering speed with a sudden full defection of any flight control.. But it sure was effective marketing though since many were very impressed by it!

[Nukemzzz]

13 hours ago, Jeff Reiter said:

I saw an old picture of a Mooney m20c with about 20 people standing on the wing, showing the extraordinary strength of the money wing. So why is 140 miles per hour the limit for speed in rough air? this makes no sense to me. if it has a strong wing, then why isn't the speed more like 175 miles an hour for rough air?

Each wing needs to carry around 1,250lbs static.  It’s many times that in reality as turbulence multiplies this. You also need a fatigue margin and a safety factor on top of that. Standing 20 people on the wing is very much easier than having 10 people jump up and down on the wing many millions of times. Aluminum doesn’t have an endurance limit. No matter how low the load, aluminum will eventually fail unlike steel. 

I believe the main factor for Vne (Not the bottom of the yellow)is sometimes fluttering.  At high speeds the tail can resonate and break up. 

My understanding of the bottom of the yellow arc is it represents the maximum safe maneuvering speed when unloaded. Above this speed, with no passengers, the plane can no longer stall with strong rising convection currents without exceeding the structural limits of the plane.  In other words, in the yellow, extreme turbulence can damage the wing because the angle of attack of the convection can’t stall the wing before damage occurs (remember it’s not just a a single overload risk, it’s also fatigue). A stalled wing has less lift and thus load. 

In other words there are complex answers to your question. Lol

[carusoam]

Jeff,

All it takes is one broken part to end the flight....

• we’re there any people standing on the tail in that pic?
• anyone leaning against the rudder?
• how about the ailerons or elevator?
• At what speed to control rods bend, or hinges fail?
• What speed is the windshield good til?

 

There are two parts to this equation...

1) When it comes to laws of physics...

Don’t use the ancient advertisement as guidance on how to fly a plane... back in the 70s it was normal to oversell everything, all the time... using very little truth in advertising... people gently sitting, with their weight nicely distributed over the wing’s surface area... believe it or not... is not actually like flying loads....
 

 Mooneys don’t have wooden tails any more... because one fell off... (there is a whole story to go with that) all the wooden tails got removed and replaced by aluminum...

 

There is guidance written in the POH, and primary flying text books...  these apply directly to flying Mooneys safely...

There are a lot of things pilots can get away with, like loading 20people on the wing....  

What happens if all 20people start jumping up and down in unison?   That picture does a disservice doesn’t it?
 

Planes easily can exceed Vne... As long as there is no turbulence...  Nothing but smooth air...

If you think there is no turbulence today... and you fly past Vne...   turbulence will find you...

 

Vne is written about flying straight into the wind, with no abrupt changes in the controls... when you hit turbulence.... you are no longer flying straight into the wind... what you do next will be very important...

 

 

 

So...speed matters, sticking with know, POH procedures matters...  when you go outside the guidelines it is more of an experiment...

Don’t accidentally become an experimental pilot...
 

2) The important second part... Mooneys are incredibly strong airplanes, they go incredibly swiftly... Efficiently... and safely... when  compared to other planes...

Don’t be afraid to use them in accordance with their POH...
 

Go find the picture where a baggage door came off in flight...   see how the pilot handled the ensuing incident... the plane is very strong, but metal bends and rivets can be pulled out...

Do what you can to avoid these situations...

To get a better feeling of limitations... it helps to study engineering, strength of materials, and machine construction...

 

PP thoughts only, not a CFI...

[Guest]

8 hours ago, kortopates said:

So lets say it was 20 people per wing X2 and assume 150 lbs average per person - that's only 3000 lbs per wing totaling 6000 lbs

The Mooney like most every GA aircraft is certified to handle a positive load factor of 3.8 G's. With a Max gross weight of 2575 lbs. X 3.8 = 9,785 lbs! Clearly the wing has to hold up all that weight. 

So there is nothing remarkable about putting all those people on the wing, the weight is still well below certification requirements for any light GA plane. Nor does it relate directly to any of the V speeds other than saying you can exceed that 3.8 G limit  above maneuvering speed with a sudden full defection of any flight control.. But it sure was effective marketing though since many were very impressed by it!

Except that in the picture the people were on top of the wing making it a negative loading, making the Mooney wing strength even greater than required.

Clarence

[skykrawler]

Wow.  You guys need to go back and review your V speeds from your Private Pilot training.   You might loose your tail or flutter if you exceed Vne.    philiplane, with all those attributes you should be more succinct in your responses.  I will no doubt be scalded for this.  Oh, and 25 people standing on a wing is advertising, not engineering.  If they were jumping up and down.....

 

[Jerry 5TJ]

10 hours ago, jlunseth said:

Typical in the old days was for someone to blunder into a t-storm and come out in pieces.  Mooneys might get bent up pretty good, but coming out in pieces is not the Mooney way.

Generally if you lose control of your Mooney in IMC the airframe is still intact on impact.  

[skykrawler]

This might be an affect of exceeding Vne

 

 

[Jeff Reiter]

how do rv's and other comparable aircraft compare with our speed limitations? I understand the concept of breaking up, but a "fast" Mooney M20C with a 132 mph limitation? seems ridiculous. What about later model Mooney's. what is their rough air limitation and why higher than the C?  Someone said that the tail may come off, but that only happened with a wooden tail, so why blame the tail? I love my Mooney C, but I want to fully understand why so slow?

[Nukemzzz]

Something to remember is these planes were designed for a decent amount of fatigue stress safety margin with SLIDE RULES.  It’s the technology that came not long after the abacus. Then it was test flown some number of times and didn’t crash and so they put the colors on the ASI.  If you follow the guidelines, you are safe.  If you don’t then all bets are off. 

[Nukemzzz]

18 minutes ago, Jeff Reiter said:

how do rv's and other comparable aircraft compare with our speed limitations? I understand the concept of breaking up, but a "fast" Mooney M20C with a 132 mph limitation? seems ridiculous. What about later model Mooney's. what is their rough air limitation and why higher than the C?  Someone said that the tail may come off, but that only happened with a wooden tail, so why blame the tail? I love my Mooney C, but I want to fully understand why so slow?

Everything you are reading here is educated speculation and nothing more. Only the project engineers know the facts and those facts will be confidential. 
 

My speculation is that materials and analysis of material strength and design has improved. Thus the safety margin could be reduced.  I think in the yellow region you CAN use some of these margins if the wind does the wrong things and the analysis tools of the day weren’t precise enough to make that region smaller. 

Remember these planes were designed in the Apollo days. The full backing of the US Government had just sent a man into space and the Saturn rocket had a computer that could complete hand calculator level of computations. The M20 was designed on manual drafting boards using slide rules and hand calculations. 

[skykrawler]

It's perfectly fine to fly in the yellow arc (above Vno).   Just be mindful of turbulence potential and consider the cumulative affect of stressing the air frame.

You no doubt have read a lot about fuel leaks and landings, but consider what happens to the wings during turbulence encounters.    If the turbulence is bad I will slow down to maneuvering speed.    Flying in the Mid Atlantic seaboard one will often get mountain wave across the Piedmont that turns into a nasty chop.

The SR-71 design was 1966.  The P-51 had one of the first laminar flow wings.  Slide rules are just calculators - the engineering is the same.