Challenger CL600
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 50; Flight Crew Total 5000; Flight Crew Type 90
Situational Awareness; Distraction
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Human Factors
While being vectored on the ILS 6 into TEB we were given a descent clearance to 3;000 feet. In the descent we were also given a traffic advisory report at our 2 to 3 o'clock. As we were looking for the traffic we received a GPWS [TCAS] 'TA'. About the time we received the GPWS warning we noticed our aircraft was 450 feet low. We immediately climbed back to 3;000 feet. We continued the ILS 6 with no further issues and landed safely at TEB. The reason the deviation occurred was due to a break down in CRM. Training SOP's are very clear that as a non-flying pilot sets a new altitude in the altitude selector the flying pilot then verbally verifies the new altitude. Both pilots then verbally verify the new altitude as 'armed'. In the heat of being vectored at a low altitude in turbulence into a busy airspace while looking for close proximity aircraft we both got distracted and did not verify the 'armed' portion of that SOP. Looking forward; following the training SOP's will be the main focus for every flight to keep this from ever happening again.
CL600 First Officer reports becoming distracted during vectors for the ILS6 at TEB; by turbulence and nearby traffic. During descent to 3;000 feet the new altitude is set in the alerter but not armed; resulting in a 450 foot deviation below 3;000 feet.