Date: 201208
Local time of day: 0001-0600
Location: MEM.Airport, TN
Flight conditions: VMC
Light: Night
Aircraft: Widebody; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
Airspace: Class B MEM
ATC / advisory: Center ZME
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface; Workload; Time Pressure; Situational Awareness; Distraction
Second reporter function: Pilot Flying; First Officer
Anomaly: Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Flight Crew FLC Overrode Automation; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Aircraft; Procedure; Human Factors; Chart Or Publication
Primary problem: Ambiguous

Narrative: Somewhere prior to ARG we were cleared to 'descend via the FNCHR1 arrival' and the pilot flying set 4;000 in the altitude window (lowest altitude on the arrival). Our FMS cost index [CI] for this flight was 55. This CI typically gives you a less than 290 KTS descent IAS. In this instance it was producing a descent speed of 265 KIAS. However; there is an airspeed restriction of 290 KTS at ARG. I have never been in a situation where you are in an ECON Profile mode and your CI speed is BELOW an upcoming speed restriction. I mentioned this to my First Officer and said to watch it and make sure it speeds up to make that restriction. At a point 2 miles prior to the restriction; we were still at 265 KIAS and the aircraft was making no attempt to increase its speed. I told the First Officer that I was going to put 290 in the Tactical Page; which I did; and we made the 290 KTS restriction at ARG. As we proceeded down the leg to FNCHR with an altitude restriction of 10;000 FT I mentioned to him that we needed to start slowing (we had 290 in Tac Mode) so as to be at 250 KTS crossing FNCHR because the aircraft was going to descend below 10;000 FT at that point. Speed reduction wasn't happening fast enough in Tac Mode so we went to LVL Change. When we crossed FNCHR we had slowed to 250 KTS; but since we were in LVL Change and had the lowest altitude of 4;000 in the window; we continued descending below the next altitude restriction of 9;000 FT at LOONR. I caught the error as we went through approximately 9;100 FT and the First Officer arrested the descent at 8;600 FT and began an immediate climb back up to 9;000. Nothing else was said and the remainder of the flight was uneventful.There were several factors here: The first was the fact that the 55 Cost Index was giving a descent speed not compliant with the arrival restriction of 290 KIAS; and was apparently not going to correct; causing us to come out of PROFILE mode. This inevitably caused us to miss the next restriction further down the leg of 9;000; having set the 4;000 FT in the altitude window per the SOP for this arrival. The second was our lack of familiarity with the new RNAV arrivals. This was my second time flying one of these; my first being the week before (a daytime arrival) which never had us flying the profile due to ATC traffic flow; vectors; etc. The third factor for me was the fact that I had my EFB display of the arrival page in 'night' mode which makes an otherwise cluttered procedure look even more cluttered visually. Looking back on this if I had switched to 'day mode' I think the info on the page would have 'popped out' a bit more and would have made it easier to interpret. I think since we are flying these arrivals; we need to seriously look at deleting the 55 Cost Index. Again; I don't know why the aircraft did not attempt to speed UP to make the 290 KTS restriction that WAS programmed in the FMS; and it WAS in Profile/ECON mode. But I have never had any problems with the aircraft SLOWING to make restrictions.


Second narrative: After leveling at 10;000 at FNCHR the next restriction was 250 KTS at JESTI then 9;000 [at] 210 KTS at LOONR. At this time Level change was selected to keep up with the descent. Profile was going to be reselected after the plane caught up. Because Profile mode was the original plan for the descent; 4;000 was left in the select window. Profile was never reselected and thus did not level at 9;000 for LOONR. Once the Captain and I noticed the mistake I hand flew the airplane back up to 9;000 immediately. The rest of the descent and approach was uneventful.I have less than 100 hours in the airplane and these are brand new arrivals so experience and proficiency in the airplane will help.


Synopsis: When the flight crew felt it necessary to override autoflight vertical navigation to meet the altitude and airspeed restrictions of the FNCHR RNAV STAR to MEM they momentarily descended below the crossing restriction an LOONR.