British twin engine design

[shake307]

This may have been asked and answered before.  Why did the British place their engines so far coward on twin engine craft?  The Beaufighter is quite distinct with this but the Mosquito is also somewhat "engine forward."  I started noticing this when I looked into the Westland Whirlwind heavy fighter and it also has the distinct engine forward design.  Is it just these three aircraft, or were all twin engine fighter bombers like this?  Any info on this would be appreciated just to satisfy my curiosity.   Thanks in advance.

[shake307]

Seems like a lot of twin engine designs of the era were that way.  The Me 410,  the P-38 to some extant, even the Me 110 was designed like this.  I am probably missing others, but doing my bit of research doesn't answer my original question.  In fact, it just creates more.

[Mace2004]

I'm sure there are other reasons but one of them was the size of the props.  The bigger the props the farther out the engines have to be mounted for the props to clear the fuselage.  Extend the engines forward and shorten the nose and the engines can be moved inward closer to the aircraft's centerline.  This would have effect on the weight of the aircraft structure and concentrate more of the engine weight inboard improving roll rate.  Of course the big downside is that visibility is reduced.

[Ratsy]

Some of it has to do with stabilizing the 'gun platform'.  Engines forward helped balance the cannons and ammo in the belly and provided the design a slightly longer tail moment.  When you put a little dihedral in the horizontal stabs you have some serious longitudinal stability.  These are just guesses on my part but I've modeled all these elements with RC airframes.  Dave Platt incorporated these elements into a twin design called "Duelist" and it was one of the sweetest models I've ever flown.

Just another Beau Junky.

 

Can I add the 'B.O.S.S' to my sig?

[Randy1]

It is really all about balance.  That is getting the center of gravity in the  right spot which is usually very close to dead on the main spar.  If you could jack up a plane supported just at the main spar the plane should jack up level.  Of course consumables like fuel alter this.

The weight of the motors and how far they are forward  is to counter the weight behind the main spar.

V12s and radials engines alter the distance forward the engine has to be placed.

This is just a basic reason.  Other issues like cooling or airflow wil figure in as well but the cg is main reason.

[shake307]

Thanks for all the replies.  I figured it had something to do with balance, but wasn't quite sure.  I did not consider the engine placement on wings and how it affects roll.  Lots of good info here.  Thanks all for giving me input.  Curiosity is now somewhat fulfilled.  I guess the British just really went all out with their designs.

[Greebo]

Early variants of the Hercules radial engines used in the Beaufighter had problems with vibration. Bristol found the easiest way to get round this was to make the engine mounts longer. This created a big gap between the firewall and the engine, but the long mounts acted like a shock absorber to damp out the worst of the vibration. IIRC in later versions they used hydraulic engine mounts to fix the problem.

[PR3D4TOR]

Randy is right that it is about balance, but if I read him right he got it backwards. The engines are the heaviest components of a WWII single or twin engined aircraft. In an early Spit or 109 for example the engine accounted for about a third of the (dry)weight of the entire airplane. For several reasons the engines have to be mounted ahead of the wing, which moves the center of gravity forward of the wing. The center of lift however is somewhere aft of the wing due to the combined lift of the wing and tailplane. To move the center of gravity closer to the center of lift they built the rest of the plane mostly behind the wing.

[dirtdart]

Ease of maintenance?