Why wouldn't a helicopter ejection seat eject sideways? Or forwards?
Well to me it seems that in your question you consider the helicopter flying straight and level and clear of any terrain. Well that's not true so let's take each case separately:
Eject forward
That seems like the most dangerous option to me. What if you are into CFIT? The ejection system will actually &quot;spit&quot; you into terrain with your helicopter's speed plus the speed of the acceleration. Ouch. Even if you survive this, the point is to escape the helicopter. And guess what its trajectory is: forward.
Also consider that the free stream works against you so you will need more acceleration to get away of the incoming helicopter.
Finally, right in front of you there is equipment like dashboards machine guns sensors et al. that need to get out of your way before you go.
Eject sideways
That sounds a least dangerous option. But what if the helicopter is banking to one of the sides? If the crew is seated side by side do they have time or even the option, &quot;I go first you go after&quot;?
Also bear in mind that attack helicopters' nature is to fly low and maneuver a lot. So there are high chances to be low and bank at the same time when in need to eject.
So the above 2 leave you with one option: eject upwards. But then you have one (or maybe 2) big propellers rotating above your head. But that's &quot;easy&quot;: you get rid of them the same way you get rid of the canopy and then eject. Once the blades are released, the centrifugal will do what it knows best and the blades will be out of your way in no time. Well, hopefully.
Considering the &quot;too many explosives above ones head&quot;, it's not rare practice to use explosives to get rid of things that are in the pilot's way like for example the canopy. That's been around for a while. But changing the trajectory of escape that will be a new concept and it will need lot's of testing.