Jet and Cone

[roland]

But why can not Jet and Cone enhancement be combined?

[Kelly Pedersen]

Because they do similar, but mechanically incompatible things. An attack with Cone is an area effect attack, that fills the cone you've described. A jet attack, on the other hand, is basically a melee attack with a long reach - it only attacks a single target, and it doesn't use the rules for large-area injury (that is, you're hitting a specific hit location on the target).

In order to build an attack that can be either a narrow, single-target jet, or "adjust the choke" and spread out into a wider cone that affects everyone in an area, you'd build them as separate innate attacks, and then apply the Alternate Attack modifier to the cheaper one, and define them as different "modes" of the same weapon.

[roland]

and if I wanted a character that has an attack that starts from his hands and whose trajectory can be moved like that of a flamethrower, but wider than a jet?

[Anaraxes]

If the attack affects an area, it's not meaningfully a "jet", regardless of the fluff text. Jets are melee attacks, and are not the same as single-hex-wide Cones. (Take a look at the mechanics again, particularly with how you target, defend against, and Dodge melee attacks compared to area-effect attacks.)

If you want to splash in an area around your arc's impact point, buy a regular Area Effect. If you want to wave a stream around and hit lots of people, buy a Cone as wide as it needs to be to accommodate your mental image of how much waving you can do. (In this case, the fact that the fluff text says you're waving it around "like a flamethrower" is interesting, but not relevant to the mechanics. You're attacking all these people in a area in a single turn.)

[Kelly Pedersen]

Originally Posted by Anaraxes

If you want to splash in an area around your arc's impact point, buy a regular Area Effect.

This is all correct, though it is possible to spray an attack with Jet over more than one target - the rules for this are in High-Tech (p. 178). The limitation there, however, is that you can only affect a three-yard wide spread, you have to divide the damage between the spaces affected, and it takes an All-Out Attack. So, if you want an attack that's normally a single target but can be spread over multiple targets with those restrictions, you can just take Jet. But if you want the spread to cover more area, with less-reduced damage, or without requiring an All-Out Attack, buy one with Cone and just describe it as being a spray covering an area.

[Not another shrubbery]

Originally Posted by Kelly Pedersen

This is all correct, though it is possible to spray an attack with Jet over more than one target - the rules for this are in High-Tech (p. 178). The limitation there, however, is that you can only affect a three-yard wide spread, you have to divide the damage between the spaces affected, and it takes an All-Out Attack. So, if you want an attack that's normally a single target but can be spread over multiple targets with those restrictions, you can just take Jet. But if you want the spread to cover more area, with less-reduced damage, or without requiring an All-Out Attack, buy one with Cone and just describe it as being a spray covering an area.

You probably should have Selectivity on top of Cone to show that the attack can focus on one target w/o hitting a wide area, or use the AA Jet you mentioned (in which case you might want to match the ranges).