Date: 201909
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: Thunderstorm; Turbulence
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Situational Awareness; Communication Breakdown; Time Pressure
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: General Physical Injury / Incapacitation
Contributing factors: Human Factors; Procedure; Weather
Primary problem: Procedure

Narrative: We were on the filed the [RNAV] arrival into ZZZ. On initial ZZZ Approach contact we were given descend via the arrival and ILS RWY XY (which was on the ATIS and briefed). The Pilot Monitoring (First Officer) dialed down to 6;000 feet. After we began the descent; we had a frequency change where the Controller gave the flight in front of us and then us instructions to cross ZZZZZ at 14;000 [feet] and expect ILS XXR. This was so far outside the arrival I believed there must be some event they were moving us for in such a rapid succession. There may have been a speed given also (310 kts). This brought us thousands of feet above path (Chart says--ZZZZZ at 280 kts; between FL200 and 17;000 [feet]). The flight in front of us was given the same possible; yet maximum effort slam dunk down to 14;000 [feet]. We were descending around 310 kts to reach ZZZZZ at 14;000 [feet]. The wording on crossing ZZZZZ was ambiguous enough the First Officer dialed in 14;000 [feet] and then returned it to 6;000 [feet] (the bottom altitude) which I wasn't comfortable with and directed the altitude back to 14;000 [feet] until clarification of instructions could be accomplished. As the First Officer asked ATC for clarification; we were given a frequency change. Upon check-in of the next frequency; the First Officer stated Aircraft X is descending to cross ZZZZZ at 14;000 [feet]; then asked if we were still cleared to descend via the arrival down to 6;000 [feet]. The new ATC voice stated turn right to a heading and direct ZZZZZ1 to resume the arrival. To the best of our recollection he also stated slow to 280 at this point (which is on the arrival anyway; so in the box). We were now given expect ILS XXR. Being above 18;000 [feet] I initiated another runway change and had already pulled landing data for both [Runway] XY and XXR. (In cruise while accomplishing our arrival brief; I discussed the possibility of runway change as we were coming to a gate on the north side of ZZZ.)The best recollection at this point was another frequency change with a check-in. Upon contact we were given RNAV (Area Navigation) Y RWY XY. The First Officer had pulled up the RNAV Y XY but not executed it until I verified. As I was now heads down trying to verify the routing with new approach; the Controller stated 'Aircraft X radio check' to which I stated ya; go ahead or something near that. He said I have been trying to contact you as I show a cell of moderate or extreme (can't remember) precipitation in about 10 miles. As we were descending to cross this fix at maximum descent; I looked out to see a white puffy cumulonimbus coming up directly in front of us as we were almost leveling out at the 14;000 [feet]. We were somewhere around 16;000 [feet] almost leveling off at the 14;000 [feet]. This cell was somewhere between 16;000-15;000 [feet] over the shoreline on the vector to head direct to ZZZZZ1. This was a line of cotton shaped cells along the shore line. Not large; but probably growing in the morning sun with the humidity. As we punched through; we got 2 bumps which started in the front into whipping the back; tossing flight attendants in the aft around. This possibly took 4-5 seconds total. Both flight attendants in the aft were not seated. The two in front were seated. All passengers were down also; as the final good bye message was completed and seatbelt sign was on. After we came through; it was back to normal as we arrived at 14;000 [feet]. During the bumps; the First Officer stated out loud flight attendants take your jumpseats; and I said yes please. The First Officer then said over the PA; flight attendants take your jumpseats; flight attendants take your jumpseats. When in the clear; I asked him to contact the back and see who was hurt; hoping for good news. This is when we found out one was in the aft lav and hit her head. The other aft Flight Attendant later stated she hurt her leg trying to get in the jump-seat but slid down onto the floor. As the FirstOfficer was receiving the medical news; the same Controller now asked how the ride was or how was that? (I was pissed) and stated SEVERE! (It wasn't severe turbulence in the sense of severe; but it was severe as this entire event continued to get worse by these extreme intents. We later discussed the amount of turbulence which would match moderate only). This was all brought on by some nonsensical imposed emergency. I stayed on the radios and flew the plane at that point. The First Officer pulled up the RNAV Y XY for me to accept; but had so many different approaches he had to go down 3 pages to find the final approach fix of the RNAV to bring to page 1 and clean up. Now I stated we will no longer be staying on any course and will be diverting around all cells in front of us. This is when we were told we could now expect a visual to [Runway] XY. No ILS XY; ILS XXR; RNAV Y XY; but a visual XY. I asked the First Officer to type a note to Dispatch for medical at the gate. As we taxied to ramp entrance; we asked again if there would be medical waiting. They were on the way. After the passengers deplaned; I went back to see the Flight Attendant being loaded into an aisle chair with a neck brace on. Whatever emergency brought on this disaster descent; way under assigned and initially flown arrival; must be ferreted out and removed. I hurt flight attendants trying to accommodate their disaster.


Second narrative: While executing the RNAV (Area Navigation) arrival to ZZZ; the aircraft descended through a towering cumulus cloud and encountered moderate turbulence for a period of 4-6 seconds. The resultant disruption of the aircraft's smooth descent resulted in the Flight Attendant assigned to the aft portion of the aircraft and occupying the aft lavatory at the time of the turbulence to sustain an impact to the head which necessitated medical attention from first responders followed by examination at a local medical facility. A second Flight Attendant; while attempting to take her jump seat; fell to the floor and subsequently sought attention from the [Company] medical clinic at ZZZ. The following is presented to the best of my recollection. The aircraft was originally cleared to descend via the arrival. Prior to and following the turbulence event the pilots had received and complied with multiple instructions from Air Traffic Control which were not in keeping with the altitude gates (cross ZZZZZ at 14;000 [feet]) and course on the arrival. The pilots queried ATC for clarification as to the requirement to adhere to the original 'descend via' clearance; however the requested clarification was slow in being communicated due to the transition of ATC controllers and controlling frequencies. Ultimately; the aircraft was directed to proceed direct to ZZZZZ1 and resume the arrival. Additionally; the expected approach was changed from the ILS RWY XY as advertised by ATIS (Automatic Terminal Information Service) and ATC upon initial check in to the ILS RWY XXR to the RNAV (RNP) Y RWY XY to the Visual to RWY XY; which was the approach from which the landing was completed. The flight scenario summarized in the paragraph above created an environment where the assessment of the risks associated with the cloud build ups in the terminal area and the implementation of strategies to avoid them could not be adequately completed due to the pilot's efforts to fly the aircraft in compliance with ATC instructions and to configure the aircraft's navigation and communication equipment to execute the various approaches advised to expect. As a result; an avoidable turbulence event occurred resulting in completely unnecessary injuries.


Synopsis: B737 flight crew reported they encountered moderate turbulence on approach causing injuries to crew.