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Post by nohippychicks on Nov 2, 2023 2:07:58 GMT
BLUF: Check your toe brake to master cylinder hardware! Now.
Long form: I started looking into a problem that originally started out as "No left turn input from pilot's side of aircraft," or some such. Turned out to be a broken link between the #1 rudder pedal and the master cylinder on the same side. It was sheared right in twain. Replaced and moved on, but I started looking at other '8s in the fleet and saw a few disturbing trends. Well, lo and behold, amongst the myriad of the fleet I uphold I begin see doglegs, joggles, and distortions a plenty in this particular part! A part that is not typically held suspect for failure.
So I thought I'd make it known to you, good crew, another thing to pay particular observance to on your LSA craft!
Behold! What I seem to remember Tecnam calling the "Brake pump plate," that lies lowly on your pilot and copilot left brake pedal, meekly connecting toe brake to Master cylinder:
T'one on the left is a stock unit, part number unremembered as I'm not at work, one on the right is the almost faltered link!
Funnies aside, the right one is supposed to look like the one on the left. The typical pilots of these planes, where I reside, weigh in at a smidge under 170 while I weigh in right at. I've got to assume that this bending is done at static RPM while full body pressure is on the brake to avoid scooting along while into the wind.
Speaking as someone who's been around planes for more than just a few years, this isn't a part of the plane that the average mechanic would expect to fail; and, in the above fail condition, may not clearly have known that it was a problem. If I weren't just a hair Tecnam savvy, one may have looked right at the problem and skipped over it thinking it was a bend intend to be there from the factory, so I wanted to put this out there into the world.
This little stainless abomination could be lurking on your very aircraft and I caution you, good folk, to look right into it. You don't need anything more than a flashlight and an intrepid spirit of investigation to see if you have or will have a problem in the future.
These 2008 aircraft being set upon by the FAA generously as an LSA, there may be leeway to remove the washers between the stainless link and the clevis on the master cylinder and replace with a doubler of some sort...
Any thoughts here?
Sorry for any inconsistencies, I'm dealing with a toddler, so I hope you'll bear with me.
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Post by ronin5573 on Nov 3, 2023 20:22:05 GMT
I looked at mine very carefully today. Either mine is fine or I have no idea what you’re talking about. Do you have any pictures to show?
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Post by nohippychicks on Nov 4, 2023 0:26:38 GMT
I looked at mine very carefully today. Either mine is fine or I have no idea what you’re talking about. Do you have any pictures to show? I thought I'd added the pictures when I posted! Don't know what happened, but either way I edited the post to include some pictures. One is at the back of the rudder pedal and shows the (bent) link as installed on the AC, the other is the removed bent link and the new link side by side. If you need more pictures, let me know and I'll see what I can do when I get back to work. |
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Post by LSA Flyer on Nov 5, 2023 0:39:04 GMT
That 90 degree bend looks like it done at installation in order for the parts to connect. I don't see how the attachment can be made if the "link"/bracket is flat. I looked at the MM and the IPC but couldn't find an illustration. It wouldn't be unusual for Tecnam to send you a "pattern' part that required drilling or bending to install. Regrets my plane is 1000 miles away or I'd have a look.
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Post by nohippychicks on Nov 5, 2023 1:37:40 GMT
That 90 degree bend looks like it done at installation in order for the parts to connect. I don't see how the attachment can be made if the "link"/bracket is flat. I looked at the MM and the IPC but couldn't find an illustration. It wouldn't be unusual for Tecnam to send you a "pattern' part that required drilling or bending to install. Regrets my plane is 1000 miles away or I'd have a look. Good point, I should have addressed that in the original post!
While it isn't unusual for Tecnam to send a part that needs finishing, this doesn't seem to be one of them.
The aircraft in question is part of a flight school, so it's entirely possible it gets beat up on more than your personal plane does, but the other day one write-up we got in actually had that link break right in two so I wanted to just put the information out there for you good pilots.
The straight link in the photo is a take-off from a different '08 and I've inspected our fleet of a couple over ten '08s and the majority had doglegs in that link on the pilot's side, with two others having the 90 degree bend. The two brand new aircraft, which haven't had students in them, have that link nice and straight. Also, the co-pilot's side links (which have the same part number in the IPC...which isn't 100% as all four seat rails ALSO have the same PN in the IPC...) are all straight.
The reason that the link can connect to the master cylinder with and without the dogleg, 90 bend or whatever is that the master cylinder lower link has a ton of slop built into it. If you were to disconnect the upper link of any of the master cylinders, they have several degrees of movement in any direction. I should have gotten a better picture, but I wasn't thinking of forums when I took the pictures, so I only have what I have.
Off topic, do the pictures look OK to you guys? I was expecting to be able to directly upload them to the forum but I wound up having to figure out how to save them to a Google something-or-other, then use a link for the photos to show up and I'm using a Linux machine so I wonder if I'm seeing the same thing you see...which is absolutely HUGE pictures.
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Post by LSA Flyer on Nov 6, 2023 23:46:09 GMT
Thanks for the additional description, I'll be sure to inspect that link when I get down to FL next month. Your pictures look great!
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Post by technammech on Nov 7, 2023 22:11:00 GMT
Thanks for sharing the information from one flight school to another. We don't have any 2008's but we do have a P2006T, a P92 Echo MkII and 3 P-Mentors on delivery. Even though we don't have any, they typically make things the same way as a manufacturer. So thanks again.
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