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Flap Overspeed RV7A

Tcheairs

Well Known Member
Took off yesterday with full flaps (inadvertently). I have an excuse but it doesn't matter so please don't ask..Was at 130kias before I realized what was going on. Retracted the flaps and proceeded to cruise flight. Noticed slight vibration which unfortunately is something new for my RV7A.

What components of the flap system are most likely to have been damaged due to this bonehead stunt? How should I proceed with an inspection. Does anyone have a drawing of the system that they could share..I am not the builder of this (once) beautiful airplane..

Sadly..Thanks..:(
 
Ive done the same, but never got to that speed with full flaps ! Thats fast with all that drag. I personally think you are fine, no harm to plane. Also I believe there is much more potential for damage doing 130 and deploying full flaps . If they retract and extend , and the trailing edge looks in alignment, my opinion is go fly, forget about it. Many post over the years on this, I never recall reading of damage, other than ego :)
 
Rest assured you are not the only RV pilot to blow past flap speed.

Most likely there is no damage to the airframe but the first thing you want to check is the flap pushrods to make sure they aren't bent. Not sure about the vibration, maybe an issue with the pilot instead of the airplane? :)

You need to order the plans for your aircraft so you and your mechanic have them for servicing questions. You can get them for a minimal price on a thumb drive from the Vans store.
 
There is now a noticeable vibration in flight with the flaps retracted which has never existed before. Thought it might be the engine as it just came out of annual which was done by a very reputable shop. (no engine vibration noted on engine runup). I have not had an opportunity to start troubleshooting (flap alignment and rods) today yet, but I will do so.
 
Check everything in the flap retraction system. Actuators, Push rods, weldments, bearings, bolts. Look for anything that looks bent and any type of freeplay. Your vibration could be the flap flapping due to something bent and causing freeplay.

Thread Drift, do builders that sell their RVs not include the plans, manuals, and builder notes with the sale? I guess I would not buy one if they were not included.
 
Time for a full inspection. Off the top of my head:
- With the flaps fully up, use a straight edge across the wing skin and flaps. Look for variances between the two flaps and for variances inboard to outboard on each flap.
- Lower the flaps and look for new vibration marks on the bottom of the fuselage where the flaps tuck in when fully retracted.
- Remove the flap rod and drop the flaps so you can check the flap hinge. Look for broken or bent hinge eyes.
- If anything looks odd, pull the flap hinge pin and inspect the flap on the bench, and further inspect the flap hinge half on the wing trailing edge.
- As previously discussed, inspect the removed flap rod to see if it is still straight.
- Inspect the flap rod fuselage pass through hole to see if the flap rod has been rubbing it.

Let us know what you find.
Carl
 
Time for a full inspection. Off the top of my head:
- With the flaps fully up, use a straight edge across the wing skin and flaps. Look for variances between the two flaps and for variances inboard to outboard on each flap.
- Lower the flaps and look for new vibration marks on the bottom of the fuselage where the flaps tuck in when fully retracted.
- Remove the flap rod and drop the flaps so you can check the flap hinge. Look for broken or bent hinge eyes.
- If anything looks odd, pull the flap hinge pin and inspect the flap on the bench, and further inspect the flap hinge half on the wing trailing edge.
- As previously discussed, inspect the removed flap rod to see if it is still straight.
- Inspect the flap rod fuselage pass through hole to see if the flap rod has been rubbing it.

Let us know what you find.
Carl
Good review, thanks. For reasons that are unclear, my recently-upgraded AFS EFIS now only displays fully up, or fully down flaps. Partial flaps show only as fully retracted. I recently took off with flaps incompletely retracted (they were about 10-15 degrees down) and discovered that in cruise, well above my flaps speed of 90 kts. Glancing at them over my shoulder while banking out of the pattern didn’t suggest to me that they might be deployed at all. I don’t think there’s any damage but Carl’s post clarified what I should be looking for.
 
SNIPI recently took off with flaps incompletely retracted (they were about 10-15 degrees down) and discovered that in cruise, well above my flaps speed of 90 kts.

Partial flap speed is higher than the standard 87kt specification but I do not have any numbers for you. I vaguely recall something from Van’s on this.

I have the Showplanes flap position system and tend to put out one notch when entering downwind when below 95kts or so. I like to have full flaps out before turning base.

Carl
 
Just a few random thoughts;
- Does the in flight vibration changes by speed? Does it changes by RPM?
- Is there any movement of the flap when on the ground?
- Is there any noticeable twist/deformation of the flap? (This should affect how the plane flies straight or not and if it has a wing heavy tendency)

Anyway, grab your flap trailing edge and see if there is any movement both retracted or deployed. There should be very little, if any at all, movement.
The weakest part of the flap system, I believe is the round push rods unless they were upgraded to the hex version.
Also you can visually look at the piano hinge that attaches the flap to the wing and see if you observe any deformation or issues. Lastly, take a look at the rod end bearing and make sure the jam nut is tightly in place.

Good luck
 
Took off yesterday with full flaps (inadvertently). I have an excuse but it doesn't matter so please don't ask..Was at 130kias before I realized what was going on. Retracted the flaps and proceeded to cruise flight. Noticed slight vibration which unfortunately is something new for my RV7A.

What components of the flap system are most likely to have been damaged due to this bonehead stunt? How should I proceed with an inspection. Does anyone have a drawing of the system that they could share..I am not the builder of this (once) beautiful airplane..

Sadly..Thanks..:(

For drawings of the systems, I would recommend you also purchase the thumb drive for the RV7 along with the drive for the RV6. The 7 is a pre-punched 6 (for the most part) and is close enough that you will have a better understanding of how the aircraft is built.

If you need to build a replacement part, that is where you are way ahead of the RV7 group..... The RV6 plans show you how to manufacture almost every part for your plane.

Here is the order page.... https://store.vansaircraft.com/products/rv-kits-and-plans.html?p=2 you are looking for FD PLANS RV6/6A FD PLANS RV7/7A.
 
You need to order the plans for your aircraft so you and your mechanic have them for servicing questions. You can get them for a minimal price on a thumb drive from the Vans store.

If you register your airplane serial number on the new Vans web store, the latest plans for your plane are always available online in your account, for free.

I have my G5 set to show white arc, “first notch” (about 10°), as 105kts, then slowing down until about 87-90 for full flaps and on final. Is that too fast for first notch? Never really thought about it before (I didn’t build my RV-6).

I have done a go around with full flaps before, but never gotten that fast, noticed the crazy trim needed by 100kts. Didn’t ever notice any damage or anomalies from it (has happened more than once :eek:)
 
Flap speed

On page 15-22 of the RV-7 build manual it states

“ FLAP SPEED: On the RV-4/6/6A/7/7A/8/8A, 110 Statute for 20o and 100 mph statute for full 40o flap deflection.”

Converted to knots it’s 95 for 20 degrees and 87 for full.
 
Most of the advise here is on the mark.

While you have the flap pushrods off, whether they are bent or not, make new ones from 4130 steel tubing. Buy 5/16" tubing and run a 1/4-28 tap into the ends. The aluminum pushrods are the weakest link in the flap system by far.

But also while the flap pushrods are out, check to make sure that the threaded stud for the rod end that is affixed to the flap root rib is tight. It is really hard to get at the nut for that thing. (I made a special wrench just for that). Again, ideally, replace those rod ends with proper rod-end bearings with an AN bolt and an AN970 washer to keep the rod end captive. You will need a couple of washers or a spacer to position the rod-end bearing out from the root rib of the flap the right distance, matching the height of the stud assembly that was removed.

Next on the list is to check to see if the flap is twisted. Since it is driven by the root end, there is a lot of torsional load through the flap, and that load increases as velocity squared. If it was twisted, it might be evident from diagonal skin wrinkles on either the upper or lower flap skin, or both.

Next after that are the piano hinge eyelets, near the ends of the flap. Look for any elongation of the holes, or distorted loops of the hinge.
 
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Most of the advise here is on the mark.

While you have the flap pushrods off, whether they are bent or not, make new ones from 4130 steel tubing. Buy 5/16" tubing and run a 1/4-28 tap into the ends. The aluminum pushrods are the weakest link in the flap system by far.

But also while the flap pushrods are out, check to make sure that the threaded stud for the rod end that is affixed to the flap root rib is tight. It is really hard to get at the nut for that thing. (I made a special wrench just for that). Again, ideally, replace those rod ends with proper rod-end bearings with an AN bolt and an AN970 washer to keep the rod end captive. You will need a couple of washers or a spacer to position the rod-end bearing out from the root rib of the flap the right distance, matching the height of the stud assembly that was removed.

Next on the list is to check to see if the flap is twisted. Since it is driven by the root end, there is a lot of torsional load through the flap, and that load increases as velocity squared. If it was twisted, it might be evident from diagonal skin wrinkles on either the upper or lower flap skin, or both.

Next after that are the piano hinge eyelets, near the ends of the flap. Look for any elongation of the holes, or distorted loops of the hinge.
Here is a picture of the better way to attach the flap pushrod to the flap, instead of the integral studded rod bearings that are used in the kit which do not have a positive capture feature:
flap attach hardware.jpg
 
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Hex push rod

If you don’t want to work with 4130 tubing, you can buy the VA-256 flap push rod from Vans. They are made from aluminum hex rod and comes already threaded.

I tossed out the push rods I made from aluminum tube (per the kit instructions for the -7A) and went with the hex push rods from the beginning.
 
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Answer: OK..here goes. The more I thought about it the more I suspected my flaps down takeoff and flap retraction at 130 kias. This morning did a thorough inspection which did not reveal any obvious damage to the flaps or actuation rods. I was able however to move the flaps up about 1/16" in additional to the electric retracted position. Went flying, all flight regimes, all speeds, all engine power settings.. smooth as silk. Landed and toggled the flaps up electrically. Took off again and everything was still smooth.

I suspect that raising the flaps from full down to up in flight at 130 kias somehow prevented them from retracting fully. I did attempt to raise the flaps further during on the way home, but the "flutter" continued. I don't understand the situation fully, but the airplane is flying fine now. I suspect that if I had slowed the plane to 100k and cycled the flaps they may have retracted.

I did some measurements in the hangar of the trailing edge of the flaps vs the straight edge of the mid section of the wing. I did this with a yardstick at a point on the wing where I had about 20" of "flat" straight edge. Measuring the gap at the trailing edge of the flap, the gap is 5/8". I did this on both flaps at the fuselage and at mid flap. Everything measured the same 5/8" gap. I had the opportunity to compare my measurements with those of an RV8. The RV8 measured 1/4" gap at similar points on the wing. I'd appreciate some feedback as to how closely other's trailing flap edges "fair" to the mid section of the wing.

Here are some photos for your reference..Hope this clears up the question of this incident.

12_Q4V5R3ROPYmMF4oIqHgESl4Nc0w-Hh
 
I agree with Butch, everything sounds OK. You may benefit in speed by rigging your flaps and ailerons up just a bit more. Are the lower skins of the flaps up tight against the belly of the fuselage?

Although everything here sounds fine, you might still consider making the improvements I described above, to the pushrod and the attachment. The aluminum hex pushrods are an improvement, but they are fatter, and may require enlarging the hole in the fuselage (not a big deal). The steel ones are stronger yet, and retain the original diameter.

The improved rod-end attachment is a long-term safety thing. Funny story: When the DAR came to sign off on my RV-8, he did all the paperwork and was pretty much ready to go, so I asked him if he would look over the airplane and give me any opinions on what he saw. He said he doesn't usually inspect the airplane much unless he is going to do the test flight, which he was not in this case. But since we knew each other, he said sure, i'll look it over. The very first thing he looked at was my flap pushrod attachment and he already had the words half way out of his mouth to complain about the non-captured ball+stud fittings, when to his surprise he saw that I had done it "right." He sat up and said, "if you thought to do that, I think the whole airplane is surely fine." He did have some additional constructive comments about my FWF that I heeded.
 
Flap linkage

While it might be true the round aluminum flap linkage may be the weakest link in the system that does not mean it’s not up to the task at hand. Vans has addressed this issue on VAF before and said that the linkages is more than adequate to handle the aerodynamic loads asked of it. Builders can change the flap linkage to your hearts content but don’t fool yourself, your not gaining a thing IMHO.
 
While it might be true the round aluminum flap linkage may be the weakest link in the system that does not mean it’s not up to the task at hand. Vans has addressed this issue on VAF before and said that the linkages is more than adequate to handle the aerodynamic loads asked of it. Builders can change the flap linkage to your hearts content but don’t fool yourself, your not gaining a thing IMHO.

Well, yes you are..... It is easier to tighten the jamb nut with the hex to place a wrench on.....:D
 
Touché ;)

(Strength wise)

I have forgotten the exact numbers, but I once calculated the airspeed needed for the standard aluminum tube to buckle. It was closer to the max flap speed than I would like. the OP here probably came pretty close to buckling the tubes. No harm getting extra margin for those goofs when you leave the flaps down.

When I was a student pilot I flew a night cross country with the flaps at TO Flap setting the whole way. The instructor had asked for a short-field TO, so the flaps where at +10. Since it was dark it was not readily apparent that the flaps were down some, but the airplane seemed out of trim, slow, etc. I noticed my mistake when I turned downwind and started my checklist.
 
I have a micro switch on the flap torque tube so I have a FLAPS eicas message whenever the flaps are not retracted.
You can probably guess why I did that.
 
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nightmares

Of course RV builders have various bad dreams. Probably all kinds of airframe thoughts floating around at about 3 am. One of mine is how fast my RV would be rolling should one flap come up without the other.
If pushrods could be afforded made of titanium.... I would buy them.
In the meantime... my hex rods give me a good nights sleep.
And as Paul Harvey would say, "Good Day"
 
I have a micro switch on the flap torque tube so I have a FLAPS eicas message whenever the flaps are not retracted.
You can probably guess why I did that.

Probably for the same reason I have a "boost pump on" light on my panel:D
Figs
 
SNIP One of mine is how fast my RV would be rolling should one flap come up without the other. SNIP

This happened to an RV-8 builder in Phase 1 many years ago. One flap did not come up. The rod was not the cause.

He was able to fly the plane (at a reduced speed) and safely land.

Carl
 
....If pushrods could be afforded made of titanium.... I would buy them....

Titanium isn't as good a material for this as the 4130 shown in Steve's post (#15 above). Its modulus of elasticity, and hence it's capability to resist buckling, is about half that of steel. Of course you could increase its thickness and outer diameter and get back the loss, buy why bother? You could do that with aluminum, which has even lower modulus of elasticity.

Dave
 
I have a micro switch on the flap torque tube so I have a FLAPS eicas message whenever the flaps are not retracted.
You can probably guess why I did that.

I have a stick between the seats that makes it obvious where the flaps are set.
 
Here is a picture of the better way to attach the flap pushrod to the flap, instead of the integral studded rod bearings that are used in the kit which do not have a positive capture feature:
View attachment 26914

Could you share more about how that design is better, to someone who doesn't know what "positive capture" means? I'm assuming that you're saying the bolt+locknut design is less likely to work itself out than the threaded stud+nutplate version in the plans?

Also, from a practical perspective: The nut in your drawing is inside the flap--totally inaccessible from the outside. How would you inspect it or remove the rod end later? Access panel in the bottom of the flap?

Another practical consideration: The face of the flap root rib is significantly outboard of where the pushrod hangs down. You would need about 3/8" worth of spacers between the bearing and the root rib in order to keep the pushrod more or less perpendicular to the attach bolt.
 
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Could you share more about how that design is better, to someone who doesn't know what "positive capture" means? I'm assuming that you're saying the bolt+locknut design is less likely to work itself out than the threaded stud+nutplate version in the plans?

If the bearing fails, it can fall off of the shaft that goes into the flap. Voila! Split flaps. Unlike on (say) the throttle controls for your carb and fuel injection where there is a large washer that holds the heim joint captive, just in case the bearing fails and loses capture.
 
I'm pretty sure if there had been a reported failure, there would be a service bulletin on the matter.

One of our local RVs had a flap rod failure several years ago but not sure if it was due to operational or installation error.
 
One of our local RVs had a flap rod failure several years ago but not sure if it was due to operational or installation error.

Yep. There were also a couple back in the day of the RVator where the rod was chafing on the hole cut in the fuselage and the rod eventually failed. The admonition was to make sure there was enough clearance that the rod NEVER hit the sides of the hole.
 
Could you share more about how that design is better, to someone who doesn't know what "positive capture" means? I'm assuming that you're saying the bolt+locknut design is less likely to work itself out than the threaded stud+nutplate version in the plans?

Also, from a practical perspective: The nut in your drawing is inside the flap--totally inaccessible from the outside. How would you inspect it or remove the rod end later? Access panel in the bottom of the flap?

Another practical consideration: The face of the flap root rib is significantly outboard of where the pushrod hangs down. You would need about 3/8" worth of spacers between the bearing and the root rib in order to keep the pushrod more or less perpendicular to the attach bolt.

Hi Ryan,

Kyle answered your primary question I think. The fitting that is supplied in the kit is a combination of a rod bearing and a threaded stud that is attached to the spherical ball - it is all an integral assembly. If the bearing were to fail (they do sometimes) then the rod end would become separated from the threaded stud. Whenever rod end bearings are installed, it is proper practice to put a large diameter washer on the head of the retainer bolt that goes through the spherical ball, so that if the bearing were to come apart, it would at least be captive and stay more or less together.

Your observation about the nut being inside the flap - yes it is kind of a pain to get a wrench on that nut. The end "rib" of the flap is not a full rib; it is open toward the front, so you can get your fingers in there, and a very short box wrench. It seems like a good place for a plate nut to me, but that is not part of the kit assembly, at least on my RV-8.Does your RV-7 have a plate nut there? If so, great, just screw the AN4 bolt right into the plate nut.

Your other observation about the position of the root rib and the orientation of the pushrod -- The pushrod does not come down perpendicular to the attach bolt. The pushrod angles outward some as it comes down. It does take a short spacer or a small stack of washers to replicate the position of the rod bearing with the integral threaded stud. This will put the pushrod in the same position so it passes through the fuselage hole correctly. You don't want to add any more spacer than that because it starts being a pretty long cantilever attachment for the bolt. I think my spacers are just about 3/16", but I would have to verify that.

Hope that helps.
 
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Thanks, Steve, that was understandable! It's good to understand why people do particular mods, even if I don't plan to do them. I'm replacing my aluminum pushrods with 4130 steel tubes, since I gouged the aluminum ones pretty badly, and I entered this thread looking for ideas of what else I could do "once I'm in there".
 
I think everyone could agree that there is always a weakest link. If you find one and you strengthen it, now there is a new weakest link. The main question to always consider is is something strong enough for the job that it is expected to do.
We have done compressive static load testing of the standard aluminum tube flap link rod. The load that it failed at was way above any load it ever experiences in service.
The only actual failures on builders airplanes that I am aware of were able to be explained by errors made during construction. Some were tubes that had been bent slightly (which is a very bad thing to do on any load member that has compressive force applied to it) or the tubes had become damaged because they were rubbing on the exit opening in the fuselage, probably showing evidence of that for quite a while, but it apparently being ignored.
 
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