Regional Jet 700 ER/LR (CRJ700)
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Ground Event / Encounter Other / Unknown; Inflight Event / Encounter Wake Vortex Encounter
General None Reported / Taken
Procedure; Environment - Non Weather Related
This [report] is due to a possible hard landing while on Runway 33 in DCA. The approach to Runway 33 looked stable to me. I was on speed during final and we hit some wake turbulence from a departing [Embraer] 170 or 175 aircraft that rotated right in front of us on Runway 4. It wasn't much; but enough to roll the aircraft slightly left and right. This happened between 30 - 40 feet AGL. I started my landing flare immediately after clearing the turbulence and reduced the trust levers to idle as if it was a normal landing. Right before touchdown I felt the bottom drop out on us. I had checked around 2 seconds prior and I was on airspeed then as I transitioned to outside. The landing was very firm; much more so than either of us are used to. The struts did compress and extend prior to settling but we definitely did not bounce. Neither the Captain nor I noticed the VSI on touchdown.  We did not believe that landing met the qualifications to be considered 'hard' by the FOM. As such; this landing was not written up as a hard landing in the AML. During the walk around I did not see anything abnormal. As it wasn't written up; neither of us believed it was a hard landing. This [report] is in response to a phone call informing us of passengers saying the landing was hard and there were possible injuries. No one said anything to me as they exited the aircraft; I thanked them for flying. I'm still thinking about this. I know I was on speed; the turbulence was over during the landing flare so I don't think that caused it. I may have reduced the power too soon. It felt like a normal approach and landing until the very end.
CRJ-700 First Officer reported flying through wake turbulence on final; resulting in a hard landing.