Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction; Situational Awareness
Deviation - Altitude Undershoot; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Chart Or Publication; Human Factors
Descending on the LTOWN SIX RNAV arrival into MEM we descended below FL240 approximately ten miles prior to AXXEL. I realized this at 23;500 then quickly corrected and climbed back to FL240. Nothing was said by ATC.This could have been prevented by paying closer attention to the notes on the arrival as well as the Commercial Chart enlarging the arrival to a fold out page and having the restrictions labeled next to the fix instead of a note located elsewhere on the page. The fact that the arrival has been split into two sections on the small page indicates that there is not enough room on the standard page for this arrival.
[We were] cleared to descend via the LTOWN SIX RNAV ARRIVAL. The altitude window was set at 14;000 for the lower restriction at SPKER. The Captain initiated the descent and I was looking down at my weight and balance sheet; computing landing weight for predicted fuel on arrival (for V speed computation). I felt the aircraft level out; looked up and saw 23;300 FT; I looked at the MFD and saw that we were approximately 5 miles from AXXEL. The Captain initiated a climb back up to 24;000 FT. Looking at the Commercial Chart; I saw that the crossing restriction was at or above FL240 at 290 KT. The LTOWN SIX RNAV ARRIVAL is printed on a standard size Commercial Chart plate. The volume of information requires abbreviated alpha markers for detailed altitude and speed information. This and all of these detailed RNAV arrivals should be printed on the large; folded Commercial Chart plate to allow enough space to clearly note these restrictions and limits. CASOT; AXXEL and KELNE have a definite altitude and speed limit; yet the 'A' is only about 3 mm across and buried on a cluttered and busy page.
An air carrier crew descended below FL240 10 miles prior to AXXEL because the chart note describing the common restriction at CASOT; AXXEL and KELNE is printed some distance from the waypoints and not clearly associated with the them.