Date: 201911
Local time of day: 0601-1200
Location: LGA.Airport, NY
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B LGA
ATC / advisory: TRACON N90
Aircraft component: Flight Director
Component problem: Design
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Fatigue; Situational Awareness; Workload; Confusion
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Deviation - Speed All Types; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Flight Crew Returned To Clearance
Contributing factors: Aircraft; Procedure; Human Factors; Airspace Structure
Primary problem: Ambiguous

Narrative: On this particular flight we were assigned the KORRY 4 Arrival which has a bottom altitude of 10;000 feet. A few minutes after arriving we were vectored off the arrival and direct LGA. Still being at 10;000 we were at 300 knots which is not an uncommon request by the NY TRACON controllers. Shortly after; we were given a descent from 10;000 feet to 8;000 feet. As the pilot flying; I adjusted the altitude pre-select to 8;000 feet; but failed to recognize we were still at 300 knots and in manual speeds as to override the FMS automatic speed reduction.Around the 9;400 foot mark; I noticed the speed barber poll getting closer to my target speed as I was in FPA mode (Flight Path Angle). At this time I immediately used the TCS button (Touch Control Steering) to override the autopilot to arrest the speed increase now at 5 knots faster than set and observed that I had not selected FMS speeds and accomplished the speed reduction prior to descending below 10;000 feet. I adjusted the flight path; retarded the throttles and engaged the spoilers to reduce my speed immediately. Once at 250 knots; I continued the descent.The cause was the extended time at 10;000 feet at 300 knot assigned with an altitude reassignment to 8;000 feet without recognizing I was still in a manual speed mode prior to descent. I feel a contributing factor was a divert from the original destination of LGA to ZZZ due to an extremely intoxicated passenger who became very ill on the original leg causing us to divert. The divert consumed a great deal of energy and did increase my stress level between wanting them to get the medical assistance they required and also the delay for all the additional customers on board. Although I feel I was fit for duty upon departure from ZZZ; during our descent I was starting to feel the effects of the stress and some tiredness which I feel contributed to me improperly identifying the required speed reduction prior to descent. The following morning of the flight I was also sick and although I wouldn't have attributed it to it at the moment; I also feel coming down with a sickness my body may not have been running optimally; but I wasn't aware of it at that time. As always; do your best to be fit for duty and maintain situational awareness.


Second narrative: As we descended on the KORRY 4; everything was going according to plan and as briefed. The Expressway Visual Runway 31 was in use; and I was trying to get a word in on the busy approach frequency to request the RNAV visual for Runway 31 instead. As my focus was on the radios at that particular moment as I was the pilot monitoring; the Captain made a mistake of allowing the automation to slow us to 250 knots when we were assigned 300 kts transition speed. The automation has a flaw of slowing the aircraft down automatically when getting close to 10;000 feet when in FMS speed mode even though we bottom of the arrival was 10;000 feet. We were assigned 300 so we had 300 kts transition speed input in the descent profile. This speed automatically goes to 250 kts when reaching close to 10;000 feet to avoid busting the 250 kts speed restriction under 10;000 feet.The Captain forgot to choose a mode of automation at this time to avoid this slow down from happening. We slowed to 250; ATC pointed it out and had us descend to get out of the way of traffic behind us. The Captain used the wrong speed mode for this particular instance. There are multiple ways to accomplish any task in the E175; but personally I would have put it into manual speed 300 and paid close attention to flip it back to FMS speeds when it was time to descend below 10;000 feet. Another contributing factor to this occurrence was that I was giving my attention to the radios at that moment and not monitoring the Captain during this area of vulnerability. In the future; it would have been wise for me to verbally point out this area of vulnerability to the Captain. I then should have asked what mode of automation he was planning on using to mitigate this threat so that I could have paid close attention to make sure he accomplished the task at the right time.


Synopsis: EMB-175 flight crew reported difficulty complying with ATC's speed request while meeting the altitude requirements of the KORRY4 Arrival to LGA airport.