How to quickly tell an SA.316 from an SA.319? What are the major visible differences between an SE.313 and an SA.318?

Obviously the main differences are in the installed engine; Artouste versus Astazou respectively in each case. But there is seldom any discussion of how to distinguish one from another and this is complicated by magazines and websites that mis-label photos.

The main consistent difference, which is quickly discernible, is the location of the electrical generator ( or alternator ).

Artouste

In the Artouste, as shown below, the generator is forward of the intake and overhangs parallel to the driveshaft.

artouste_keyed-2013-01-22.JPEG

The generator mounting and gearing can be seen on this cutaway of an Artouste in the SAAF Museum in Swartkop ( cropped from Creative Commons BY-SA image linked here ). This example is missing the reduction gearbox casing.

Turbomeca_Artouste_IIIB_Cutaway.jpeg

Astazou

The Astazou has the generator inboard of the engine and the intake and reduction gearbox form a forward-facing cone. In general it is much more "pill-shaped" than the Artouste:

astazou_keyed-2013-01-22.JPEG

The following cutaway from this image in the Flight archives shows the accessory gearbox and generator tucked neatly under the engine; what the perspective doesn't show is that it was mounted to starboard.

Turbomecca-Astazou_IIN_Cutaway.JPEG

Intake screen

Do not rely on the presence or absence of the intake screen. Although most Astazou intallations do not have a port-mounted screen it is an option.

In summary

From a distance, then, look aft of the rotor mast for an object protruding above the gearbox. If it's there, you're looking at an Artouste-powered Alouette. Determine the exact model by reference to its family.

Here's a worked exercise: Alouette III aeroframe with the electrical generator clearly visible above my head. So this is an SA.316!

Me_IAC_SA316-2012-08-25_7750.JPEG