The Fuselage
The tail section is a full monocoque assembly, made of aluminium, whilst the intermediate section, where the engine lives, is semi-monocoque. They are bolted together through large castings that are checked every hundred hours. The forward section
(i.e. the passenger compartment) is an aluminium honeycomb structure.
The skids are designed to absorb energy in a hard landing.
The hook can normally carry 1200 lbs, but there is a 1500 lbs version.
In the LongRanger, the horizontal stabilizer assembly has a movable rear elevator connected to the cyclic to provide greater authority. The side fins are offset, opposite to the vertical fin angle (the horizontal stabilizer is also offset in relation to the tailboom, in that it protrudes more one side than the other). These are designed to improve the efficiency of the vertical stabilizer.
An increased tail rotor pitch travel is provided by the rigging procedure for greater authority.

The Engine
Somebody once said that this looks like a dustbin with the garbage on the outside!

The III model has an Allison 250-C20B, which weighs 158 lbs. Although it can produce 420 shaft-horsepower, the transmission limits it to 317. Inside its compartment, there is enough space between the bottom of the engine and the titanium deck underneath to allow the servicing of accessories without removing the engine.
Essentially, a six-stage axial flow, one-stage centrifugal compressor is bolted to a two-stage turbine, which itself consists of 2 two-stage free turbines (the first of which drives the compressor), feeding into the second, which drives the power output shaft. Air is initially compressed to over 6 atmospheres then transferred to the combustion chamber at the rear, through two air transfer tubes that are plainly visible on each side.
After passing forward through the turbines, it is exhausted upwards through twin exhaust ducts. All this means the engine can occupy much less space.
Inside, the air ducts are shaped so the flame does not come into contact with the casing, or any other part of the engine, but is contained within a cocoon of cooler air called a toroidal vortex, which is why the intake air is ducted along both sides of the engine, through 180° and up through the hot section in the direction of travel, for better control. In fact, 60% of the air sucked in the front is for cooling. There have been several types of engine over the years, and the original 250 designation was because it was intended to push out that amount of horsepower, but actually was rated at 300 up till the 400 or so of the present day.
Lubrication uses a circulating dry sump system which has an external reservoir and heat exchanger. Various pressure and scavenge pumps in the engine are driven by the accessory gear box. Only the pressure and scavenge lines to the front and rear bearings are external.