Bruce wrote:

 I'm rebuilding my LIV and intend to move my engine forward 2" to help
alleviate rearward CG.
 
 Has anyone moved their engine further forward?
 

Bruce,

Please look at the geometry and layout of the motor mount and gear as you start into this.

I moved my engine (IV-P with TSIO-550E) forward 1”, which was all I could move without relocating the nose gear pivots or modifying the firewall to allow the nose gear to partially reside in the engine compartment. This causes lots of extra build-out to isolate the engine compartment from the wheelwell/rest of the aircraft for fire protection. At 2” forward, you’ll have to extend the edges of the cowling and make changes to the motor mount, the firewall, or both. Not impossible, but significant re-work, especially to re-build the engine mount. (I mounted 1” aluminum spacers between the old mount and the firewall (5 required), but I’d want to do some analysis on the shear and bending loads at the attach points before using 2” spacers. The (required?) alternative is to rebuild/rework the engine mount.

You said you were building a IV, and not IV-P. My bet is that unless you plan to fill the tail with gas tanks or similar, you’ll not have the same aft CG issue us “heavier” fellows have. You might run some numbers on this to see how much of a problem you have before starting a major change…  These airplanes started life in Lance N’s brain as rather light-weight IV’s—unpressurized and well balanced. I understand that some were built in the 1800# empty weight range. Then Lance added pressurization…a true delight, to be sure…but everything from that point started going south…or toward the tail…and the weight started piling on. My empty weight is 2290#; some IV-P’s are lighter; many are heavier. Almost impossible to add weight in front of the CG, so “extra” anything mostly adds to the CG problem; not so bad for the unpressurized planes…

Glad to talk to you on this if you want to give me a call, but bottom line is that I’ve had very good luck with my engine 1” forward, and the mods to do it were really minor. Go more than 1” however, and you take on some serious re-engineering. As you start sticking the heavy engine farther out front,  the polar moment of inertia around the yaw axis increases, adversely affecting spin recovery and overall handling…just to get you thinking.

Good luck, and tell me what you decide to do.

Bob Pastusek

757-286-4802 cell