Direction of Engine Mount Bolts?

Hello all,

 Does it matter if the bolts that attach the engine mount to the fuselage go from inside the fuselage out or  from the engine mount through the firewall into the plane?

 I have the Viking 130 mount on a 650. I attached the mount temporarily today to help move from the basement to the garage,  The Viking mount needs about a 2 1/2 inch bolt.

  With the 10 degree angle on the front of the fuselage mount brackets I don't see how I'd be able to get a long bolt to go from inside out.  The AN6-7A in the Zenith plans work ok that way but they aren't nearly long enough.

What do you think?

Thanks - Jim

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Replies to This Discussion

Permalink Reply by Joe Hopwood on February 2, 2018 at 6:17am

Not sure I understand the issue.  I don't recall anything preventing a long bolt going from inside.  I will look tomorrow to refresh my memory.

Permalink Reply by Patrick Hoyt on February 2, 2018 at 8:39am

I did mine with the bolts protruding forward from the inside, through the firewall. In other words, with the threads forward of the firewall.  If it were the other way around, the nuts would be very difficult to tighten and inspect.

I recall it being a tight fit (on an XL, with a 13 degree rake), but doable. 

- Pat

Permalink Reply by Brad Rawls on February 3, 2018 at 2:28pm

My 601 came with the bolts attached to the motor mount with the treads facing forward. - no issue there and it passed the DAR inspection. 

Permalink Reply by Joe Hopwood on February 3, 2018 at 2:42pm

Come to think of it, I believe mine did too.  But now that I am thinking about it, I think those were superceded or perhaps it occurred when I went with 650 canopy, but in any case I got new ones and used bolts but I still do not recall there being an issue with them having heads on inside and threads forward of firewall.

Permalink Reply by Jim Davis on February 3, 2018 at 5:29pm

Thanks guys. Viking is sending me some with my updated ECU and flywheel drive plate. I'll try to get them to face out like normal. Patrick - good point about inspection too.

Permalink Reply by Glenn Davis on February 3, 2018 at 6:25pm

According to the FAA acceptable methods ,techniques and practices it is preferred to torque the nut if possible but torquing the bolt is not prohibited. Page 7-298 for those interested.

Glenn Davis 

5362P

Permalink Reply by Jim Davis on February 3, 2018 at 7:19pm

Hey Glenn,

  Did you use bolts from Viking? If not, what did you use?  Are they facing out (threads on the engine side of the firewall)?

Thanks - Jim

Permalink Reply by Glenn Davis on February 3, 2018 at 7:31pm

No, My bolt heads are FF. I know I'm a disappointment to the Davis name but I could not get the bolts to go thru like you guys did short of beating the hell out of it or elongating the hole .I researched it and put em in back asswards, I can't remember if Viking supplied them or not but I don't think so.

Glenn Davis

5362P

Permalink Reply by Jim Davis on February 3, 2018 at 7:36pm

I think I'll be doing the same as you - Davis's Unite :-)

Permalink Reply by Joe Hopwood on February 4, 2018 at 7:08am

Do you mind sharing what the immovable object was that was in the way?  Some times just a slight change in assembly order can make all the difference in the world.

Permalink Reply by Jim Davis on February 4, 2018 at 7:31am

Sure, it's the engine mount brackets themselves. The front edge is canted back about 10 degrees I think. There just isn't room to get a long bolt through from the inside. I'll take a pick later today.

Permalink Reply by Joe Hopwood on February 4, 2018 at 10:51am

Thanks Jim,

I must have slightly elongated the hole but don't remember for sure.  I do for sure remember that first ones that came with kit, bolt was welded in place.  For only 10 degrees, the elongation required would not be very much.

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