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Getting under cockpit floors F-830 and F831

Saville

Well Known Member
So my intention is to install a GPS antenna on the top of the fuselage right near the passenger seat. I'd have to run the RG-400 coax forward to beneath the instrument panel.

I notice that the two forward cockpit floors - F-830 and F-831 are riveted along their after-most edges. I took out most of the screws to F-830 and that afforded me very little access underneath. I haven't taken out the screws along the left hand edge because that would require removing side panels in the cockpit. Furthermore the floor is fitted very tightly around various vertical members and the riveting along the back edge does not allow me to pull the panel inboard. I'm afraid I'd have to twist the floor too much, and put a bend in it, in order to gain access underneath.

Unfortunately the builder did not provide any means to retrofit wires through the access holes in the bulkheads underneath the floors.

Has anyone removed all the screws from either 830 or 831 and can you tell me whether or not you can lift the floors enough to get at the wiring underneath? I'm willing to take apart more of the plane if that would get me the access I need but it doesn't really look or feel like it would.

Thanks.
 
If you remove all the screws the floor boards come out semi easily. Its not much fun, its alot of screws. I just did it for my condition inspection. Electric screwdriver is pretty much mandatory.
 
If you remove all the screws the floor boards come out semi easily. Its not much fun, its alot of screws. I just did it for my condition inspection. Electric screwdriver is pretty much mandatory.

Maybe they come out on the -4 but on the -8 the back edges are riveted so they cannot come out. All you can do is bend them. And as they are fitted tightly around vertical members of the left hand cockpit wall you'd have to over bend them too much, I fear.
 
rivets vs screws

Maybe they come out on the -4 but on the -8 the back edges are riveted so they cannot come out. All you can do is bend them. And as they are fitted tightly around vertical members of the left hand cockpit wall you'd have to over bend them too much, I fear.
The plans show riveting them in, but most install nutplates and screws. If you have to remove them, you just need to drill out the rivets. Probably not much more work than removing and replacing screws.
 
The plans show riveting them in, but most install nutplates and screws. If you have to remove them, you just need to drill out the rivets. Probably not much more work than removing and replacing screws.

So you're suggesting I drill out the pop rivets, do the work I need to do, and then re-install with pop rivets?

I'd have to look but I think there is a riveted baggage floor that shares rivets with F-380. I don't think I can get under THAT floor easily as it runs aft to the battery tray.

I don't know if I could clean out any drill debris - have to look. Plausible idea though.
 
Actually, those entire floor panels are riveted to the underlying ribs with LP4-3 pop rivets per the plans. The front edges are riveted with solid rivets securing the nutplates for the foot-well screws. Sounds like you may have a hybrid.

But, have you looked at running the coax under the cockpit rails and upper longeron? If not occupied by a static line/tube, there is enough room in the bulkhead rib corners to feed RG400 through.
 

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Actually, those entire floor panels are riveted to the underlying ribs with LP4-3 pop rivets per the plans. The front edges are riveted with solid rivets securing the nutplates for the foot-well screws. Sounds like you may have a hybrid.

But, have you looked at running the coax under the cockpit rails and upper longeron? If not occupied by a static line/tube, there is enough room in the bulkhead rib corners to feed RG400 through.

Yes I noticed in the plans there were holes for running a static line and the builder did not use those. So that's an option. I'm figuring out how the run will go - I notive there are holes near the top of the vertical supports that the plans say you need to open up for a 1/2"ID snap bushing. THe hole I'd make would be smaller than that. So I think I understand how that's supposed to work up through F-804C-AL and F-804C_FL center section bulkheads where the static line is supposed to go through some notches at the top of the bulkheads. (DWG 69)

Not sure what to do after that though....what a builder was then supposed to do - dive under the panel somehow and go through the gear tower?

Go through the panel?

Dive down through a gap in the footwell and then through the spar, into the gear tower and up?
 
So my intention is to install a GPS antenna on the top of the fuselage right near the passenger seat. I'd have to run the RG-400 coax forward to beneath the instrument panel.

I notice that the two forward cockpit floors - F-830 and F-831 are riveted along their after-most edges. I took out most of the screws to F-830 and that afforded me very little access underneath. I haven't taken out the screws along the left hand edge because that would require removing side panels in the cockpit. Furthermore the floor is fitted very tightly around various vertical members and the riveting along the back edge does not allow me to pull the panel inboard. I'm afraid I'd have to twist the floor too much, and put a bend in it, in order to gain access underneath.

Unfortunately the builder did not provide any means to retrofit wires through the access holes in the bulkheads underneath the floors.

Has anyone removed all the screws from either 830 or 831 and can you tell me whether or not you can lift the floors enough to get at the wiring underneath? I'm willing to take apart more of the plane if that would get me the access I need but it doesn't really look or feel like it would.

Thanks.

Greg,

F-830 (front floor panel) comes out with screws. If your builder built to plans, the F-831 (rear seat floor panel) panel requires drilling out all the rivets. I know if several builders who modified their build and replaced the rivets with nutplates and screws; nice for future service. Reference drawing 77 "seat and floor wells" in the plans.

If you are talking about going forward up through the tower, that's not a problem. You should be be to go under F-881-1 on the left or right side and up either tower.

Brian
 
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Should be a hole in the lower section of the panel "pie slices" just under the longeron, then you're behind the panel and you can go right to your avionics box. That's all before the gear towers.
 

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Greg,

F-830 (front floor panel) comes out with screws. If your builder built to plans, the F-831 (rear seat floor panel) panel requires drilling out all the rivets. I know if several builders who modified their build and replaced the rivets with nutplates and screws; nice for future service. Reference drawing 77 "seat and floor wells" in the plans.

If you are talking about going forward up through the tower, that's not a problem. You should be be to go under F-881-1 on the left or right side and up either tower.

Brian


On my plane F-830 and F-831 are both riveted along the after most edge. My plans show this as how it's supposed to be fastened as stated in DWG 77:

"LP4-3 rivet along aft edge of seat floors. Rivet with F-834-1 aft baggage floor to F-807-1 bulkhead assembly". See attachment.
The instruction circled in red.

Also I l know how to go through the tower. It's going from exiting F-804C-FL and getting TO the tower that has me stumped.

Thanks
 

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Should be a hole in the lower section of the panel "pie slices" just under the longeron, then you're behind the panel and you can go right to your avionics box. That's all before the gear towers.


That would be great. The builder mounted some switches and other gadgets in that area of the pie slice. But the hole may still be unused. See attachment.

I'll look. If it's still there then I'm golden.
 

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Go under the rails

Make it easy on yourself and go from the antenna, forward under the rails. With the coax run that way it is out of sight and a straight shot to the panel. Easy peasy! Support as needed.
 
Not to belabor the point, but from a plans perspective, only the nutplates get a solid rivet. Although I never understood that, as you could just rivet the nutplates to the cross-brace support and spacer, and the floor rib, since the floor panel will be sandwiched in place by the aft control mount, and the foot wells. Otherwise you have to drill out those solid nutplate rivets in addition to the pop rivets to remove the floors. Kind of goofy. (not to mention, a PAIN to buck)
 

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Although I never understood that, as you could just rivet the nutplates to the cross-brace support and spacer, and the floor rib, since the floor panel will be sandwiched in place by the aft control mount, and the foot wells. Otherwise you have to drill out those solid nutplate rivets in addition to the pop rivets to remove the floors. Kind of goofy. (not to mention, a PAIN to buck)

That's what I did with mine. Didn't seem to make any sense to me to go to the trouble of riveting those nutplates in assembly with the floors, so I riveted them to the braces/angles way back when the seat rib assembly was sitting on a workbench.
 
Make it easy on yourself and go from the antenna, forward under the rails. With the coax run that way it is out of sight and a straight shot to the panel. Easy peasy! Support as needed.

Now that I know there is provision to run a line from under the longeron through the "pie panel", this is what I'm going to do. The holes will have to be widened but not nearly as much as they would if you were running a static line through there. I have some snap bushings on order and the GPS will be mounted on the fuselage this weekend.

It would have been nice to run the cable under the floor boards but the construction makes that too difficult.

Thanks, everyone, for your help and advice.
 
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