Engine rubber blocks

[Warmi]

Hi,

Today during pre-flight I noticed that pilot side, front engine rubber "block" has some surface cracks - that's the only one with cracks ( the next one has a single crack ) , the other side is completely crack free...
The whole block appears to be "solid" and these cracks are very shallow but I am wondering how should I address - should I have it replaced right away or do I monitor this and see if it grows ?
The engine had 5 year rubber replacement done 1.5 years (150 hours ) ago ....

Thanks

EngineRubber.jpg (100.66 KiB) Viewed 10448 times

[drseti]

Those silentblocks should have been replaced at the 5 year point, along with the other rubber. You should check the logbook to see if this was accomplished. If it's not specifically documented, check with whoever did the 5 year rubber replacement. I suspect they were missed 1.5 years ago, since those cracks should not have appeared in so short a time.

In any case, this is something that has to be checked at every condition inspection. If I were doing an annual and saw those cracks, I'd advise you to have them replaced. You might ask whomever did your last annual if they were checked.

If it were my plane, I wouldn't ground it based upon what the photos show. But I would consider this a mandatory item to address at the next condition inspection. And, I wouldn't just replace the cracked ones; I'd do them all.

[3Dreaming]

Those silentblocks should have been replaced at the 5 year point, along with the other rubber. You should check the logbook to see if this was accomplished. If it's not specifically documented, check with whoever did the 5 year rubber replacement. I suspect they were missed 1.5 years ago, since those cracks should not have appeared in so short a time.

In any case, this is something that has to be checked at every condition inspection. If I were doing an annual and saw those cracks, I'd advise you to have them replaced. You might ask whomever did your last annual if they were checked.

If it were my plane, I wouldn't ground it based upon what the photos show. But I would consider this a mandatory item to address at the next condition inspection. And, I wouldn't just replace the cracked ones; I'd do them all.

I agree with Paul that they should have been replaced. I normally replace them at the rubber replacement. It is worth pointing out that they are not listed in Rotax's list of parts that require replacement. Since it is not on the list some mechanics or LSRM's choose not to replace them.

[Type47]

I am interested in the discoloration above on the fins. It looks like there has been liquid dripping from the fins onto the aluminum bracket and down the side of the rubber mount.
Residue color almost looks like mogas stains.
Could be coolant or just water running repeatedly over that area.

[Warmi]

There was no mention in the aircraft log except simply stating that the 5 year rubber replacement was done and a few more general details.

However, at that time, I did attach a bill I got from the shop to the logbook entry and it lists every item that was purchased ( and presumably replaced ) for that particular service - one of the items is listed as " Engine blocks " with a price of around $140 or so I presume these were replaced , unless they forgot
The plane never had any issues in terms of engine roughness or anything that could potentially over-stress the engine bushings - I mean beyond the unusual stuff - if the carbs get out of balance , the engine gets just a bit rough when going idle just before the landing, or in certain flight modes, but these we address rather promptly.

As far as fuel stains - I bought the plane almost 2 years ago with 150 hours on it from the dealer and there were already some old yellow stains on in various places around the engine - I pretty much always take the cowling off and check the engine every 2-3 hours , looking for any new stains , anything I haven't noticed before so I am reasonably sure nothing is leaking ( I hardly ever crawl under the engine though - that's why I am not sure how long this cracked bushing was there in the first place )
We did have a carb line leak related to the 5 year rubber service, which , thankfully, I detected early on ( http://sportpilottalk.com/viewtopic.php?f=19&t=5178 )

I should probably take some time to clean the engine instead of relying on my memory to detect new vs old stains

Thanks for your help guys.

[3Dreaming]

It is possible that the damage is caused by heat from the adjacent exhaust pipe. Maybe there was a heat shield that was not put back in place, or maybe it needs on at that location.

[Warmi]

It is possible that the damage is caused by heat from the adjacent exhaust pipe. Maybe there was a heat shield that was not put back in place, or maybe it needs on at that location.

That’s a great point.
It matches very closely since the front block is the closest one to the pipe and this only occurs on the pilot side of the plane.
I am gonna ping the dealer and see if he ha any suggestions on shielding it ...

Thanks

[Warmi]

One more question ....

When I try to burp the engine or in general try to put some load on the engine via the prop - there is some play within the engine ( not just the prop ) - in other words the engine moves a bit in relation to the firewall and the metal support frame - I don’t remember this being any different before so I presume that’s the function of rubber support blocks and it is normal ?

[3Dreaming]

One more question ....

When I try to burp the engine or in general try to put some load on the engine via the prop - there is some play within the engine ( not just the prop ) - in other words the engine moves a bit in relation to the firewall and the metal support frame - I don’t remember this being any different before so I presume that’s the function of rubber support blocks and it is normal ?

Yes. Some designs move more than others.

[FastEddieB]

Coincidentally, I just got 4 engine mounts for my Sky Arrow in the mail today. $290 shipped from Italy.

[ShawnM]

Coincidentally, I just got 4 engine mounts for my Sky Arrow in the mail today. $290 shipped from Italy.

Ouch, my SportCruiser uses 6 of the Barry Mounts and all 6 from Aircraft Spruce is $45.90.

[Warmi]

Well Shawn , look at these Italian blocks and compare to the ones on my plane ... my blocks look like 29.95 stuff from Aircraft Spruce ( or worse ) while his look like $290 items from Italy

[FastEddieB]

I had asked a couple places if anyone knew a source other than the factory for Sky Arrow engine mounts and got no response.

I just searched Aircraft Spruce for engine mounts, and at first glance don’t see anything similar to mine.

If I paid way too much, at least I’ll know for next time, and can warn others!

[FastEddieB]

One more question ....

When I try to burp the engine or in general try to put some load on the engine via the prop - there is some play within the engine ( not just the prop ) - in other words the engine moves a bit in relation to the firewall and the metal support frame - I don’t remember this being any different before so I presume that’s the function of rubber support blocks and it is normal ?

I had a Citabria where we noticed the backing plate of the spinner was starting to eat into the lower cowling.Tired mounts can let the engine sag that much.

Some movement is normal. My Sky Arrow used to be hard starting, especially with a marginal battery. The engine kicked back and moved around enough that the coolant tank cap started eating into the cowling and getting chewed up itself:



No longer an issue, but the kind of thing tired mounts can lead to.

[Warmi]

Well, my mounts aren’t really tired or saggy in any way - in fact they feel and do look pretty new ( as they should be if they were replaced 150 hours ago ) except that single spot where it is cracked ...

But yeah, that’s another lesson for me to learn and another place to look for trouble - it is funny how 2 years later I have worked on so many things and seen so many potential issues that a typical preflight for me makes a lot more sense and I am actually looking for stuff and failure modes I understand as opposed to mindlessly doing preflights in my student days where I had no idea what to look for and the whole thing seemed more like some kind of magical ritual ...