Flap failure point?

[Joshua Blackh4t]

Luckily this is just a theoretical question, but its something that worries me.

If someone steps on the flaps, what's the part that breaks and is it repairable?

Mine are hydraulic flaps, so looking at the diagram maybe it can allow them to go down by themselves?

Would it be better to leave them down (I don't like it when parked outside not tied down) or with the lever up so the master cylinder is free to suck in hydraulic fluid?

 

Hopefully I never find out, but it would be nice to know how much to stress about it. 

[markgrue]

Usually their face when they face plant on the wing.   The only thing holding them up is a spring and they will go down when stepped on.

 

Mark

[Joshua Blackh4t]

4 minutes ago, markgrue said:

Usually their face when they face plant on the wing.   The only thing holding them up is a spring and they will go down when stepped on.

 

Mark

That is good to know. So if a bunch of kids decide to climb over my wings, they might not hurt it?

This is unfortunately a very real possibility in one of the places I go. Unlikely to be vandalised, just looked all over by curious aboriginal kids. Luckily the fuel caps are tight so hopefully they don't get them open to sniff the avgas

[Fly Boomer]

2 minutes ago, Joshua Blackh4t said:

That is good to know. So if a bunch of kids decide to climb over my wings, they might not hurt it?

This is unfortunately a very real possibility in one of the places I go. Unlikely to be vandalised, just looked all over by curious aboriginal kids. Luckily the fuel caps are tight so hopefully they don't get them open to sniff the avgas

Or leave a gift in your tanks.

[Ragsf15e]

18 minutes ago, Joshua Blackh4t said:

That is good to know. So if a bunch of kids decide to climb over my wings, they might not hurt it?

This is unfortunately a very real possibility in one of the places I go. Unlikely to be vandalised, just looked all over by curious aboriginal kids. Luckily the fuel caps are tight so hopefully they don't get them open to sniff the avgas

Lots of people leave them down for this reason.  I don’t think it’s “a spring” holding up hydraulic flaps, but i could be wrong.  There is a torque tube attached to the aft spar going between the flaps and there’s a common crack that occurs at the attachment and an sb to install a doubler to fix the crack.  Obviously not definitive, but I had a guy step on mine and a crack was discovered at the next annual.  It’s expensive to repair because access is through the baggage compartment floor.  Someone chime in with the sb number for me…

 

Edited August 31, 2023 by Ragsf15e

[Echo]

Calling B.S. on somebody breaking flap by inadvertantly stepping on it.  NoT a thing...

[Ragsf15e]

1 hour ago, Echo said:

Calling B.S. on somebody breaking flap by inadvertantly stepping on it.  NoT a thing...

But cracking at the attachment is definitely a thing… something cracks it there and I think stepping on a flap is as much force as anything else.

[Joshua Blackh4t]

Interesting, it seems no one knows for sure.

I would have thought it was a common occurrance, but apparently not.

The cracks are directional, and as far as I know are to do with up force i.e. flaps left down. I might be wrong though.

Still not keen to test it, but it does reassure me a bit.

 

 

 

[Echo]

1 hour ago, Ragsf15e said:

But cracking at the attachment is definitely a thing… something cracks it there and I think stepping on a flap is as much force as anything else.

No, I don't think it is even close (when up in neutral and deployed by an errant foot vs.) Being left deployed in a climb with increasing airspeed because they were forgotten far beyond max 100...That is a LOT of air pressure on the attach points imo.  Not even a close comparison.

Edited September 1, 2023 by Echo
100 not 120

[Ragsf15e]

2 minutes ago, Echo said:

No, I don't think it is even close (when up in neutral and deployed by an errant foot vs.) Being left deployed in a climb with increasing airspeed because they were forgotten far beyond max 120...That is a LOT of air pressure on the attach points imo.  Not even a close comparison.

When mine was stepped on by a ~200lb person, it deflected pretty much full down.  I’m not saying what causes the cracks at the attach points, but we probably shouldn’t step on the flaps, overspeed them or otherwise mistreat them if we want to avoid future cracking at a known weakness.

[Echo]

13 minutes ago, Ragsf15e said:

When mine was stepped on by a ~200lb person, it deflected pretty much full down.  I’m not saying what causes the cracks at the attach points, but we probably shouldn’t step on the flaps, overspeed them or otherwise mistreat them if we want to avoid future cracking at a known weakness.

On that I agree 100% sir.   

[Echo]

I would NOT leave flaps deployed while tied down.  Pilot is first in on loading.  Just pump in take off position to lesson liklihood of mistep by uninitiated.

[Shadrach]

9 hours ago, Ragsf15e said:

When mine was stepped on by a ~200lb person, it deflected pretty much full down.  I’m not saying what causes the cracks at the attach points, but we probably shouldn’t step on the flaps, overspeed them or otherwise mistreat them if we want to avoid future cracking at a known weakness.

We should not be stepping on flaps, but I think with hydraulic flaps the placard is primarily to protect unaware passengers.  I was about 7 or 8 years old first time I ever saw a woman's panties (in use) My Dad took a family friend flying while we waited on the ground. Upon return, she stepped on the flap as she exited the wing....ass over tea kettle...skirt follows gravity...bright yellow panties. 

Indeed the hydraulic flaps are held up solely by a return spring. Without the aerodynamic load of flight, something needs to counteract gravity.  Highly unlikely that a person (regardless of weight) stepping on the flaps cracked the stub spar. Those types of cracks typically propagate slowly over repeated use. The stress occurs when the flaps are deployed. The actuator as it is mounted to the stub spar is in compression as the piston extends to deploy the flaps against the aerodynamic load.  When someone steps on a flap or pushes it down, the actuator is in tension pulling the piston through its travel.  Very little stress on the system comparatively.

 

[47U]

17 hours ago, Joshua Blackh4t said:

If someone steps on the flaps, what's the part that breaks and is it repairable?

The crack in the stub spar might be hard to see.  To look for a crack, first pump the flaps all the way down.  The flap torque tube tries to rotate the torque tube support bracket that is bolted to the stub spar and the crack will be more visible.  That’s how I discovered my stub spar was cracked.

Flaps are up in this pic.   See a crack?  I don’t…

But it was there.  And not a small crack, either.

[Jim Peace]

If the flaps are up, stepping on the flap just extends the spring as far as I know on my C....I put two new springs on when I did the FLAP AD or SB whatever it was...I did have cracks on the rear spar...glad I did it...

I was in Charleston SC  recently and an older mooney taxis in beside me and I signal to him his flaps are still down...he seemed aggravated/angry that I told him, he said he always keeps his flaps down 100% of the time and spoke in a manner that either I was not educated in that procedure or I was below him being that I was in a glasair 3.......whatever..

in an older mooney with hydraulic flaps, if they are down you have pressure on the system working against the up spring...I would not leave them down and my guess is that over time they will bleed up...unnecessary wear and tear if you ask me...

[Shadrach]

2 hours ago, Jim Peace said:

If the flaps are up, stepping on the flap just extends the spring as far as I know on my C....I put two new springs on when I did the FLAP AD or SB whatever it was...I did have cracks on the rear spar...glad I did it...

I was in Charleston SC  recently and an older mooney taxis in beside me and I signal to him his flaps are still down...he seemed aggravated/angry that I told him, he said he always keeps his flaps down 100% of the time and spoke in a manner that either I was not educated in that procedure or I was below him being that I was in a glasair 3.......whatever..

in an older mooney with hydraulic flaps, if they are down you have pressure on the system working against the up spring...I would not leave them down and my guess is that over time they will bleed up...unnecessary wear and tear if you ask me...

They should not bleed up over time.  My final test of the system after maintenance and bleeding is to pump them down 3/4 (3 pumps) and leave them for several days or weeks.  When I come back they should be in the same position.

[MikeOH]

My '70F has electric flaps.  I'm thinking the 'return spring' thing isn't on mine, and stepping on the flap would be bad news.

I'd love to hear otherwise.

[PT20J]

Here’s a drawing of the electric flap mechanism from my M20J IPC. There are no springs and the whole mechanism is rigidly connected. 

[generalaviationguru]

On 8/31/2023 at 5:04 PM, Joshua Blackh4t said:

Luckily this is just a theoretical question, but its something that worries me.

If someone steps on the flaps, what's the part that breaks and is it repairable?

Mine are hydraulic flaps, so looking at the diagram maybe it can allow them to go down by themselves?

Would it be better to leave them down (I don't like it when parked outside not tied down) or with the lever up so the master cylinder is free to suck in hydraulic fluid?

 

Hopefully I never find out, but it would be nice to know how much to stress about it. 

Ours was pretty bad.  Near having holes.  The ‘67 (ours) design was the weakest (slowest flap speed limit). 
 

before 

 

Repair:

[Shadrach]

5 hours ago, MikeOH said:

My '70F has electric flaps.  I'm thinking the 'return spring' thing isn't on mine, and stepping on the flap would be bad news.

I'd love to hear otherwise.

No return spring and yes, stepping on them would be bad, but for a different reason.