Citation Excel (C560XL)
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Human-Machine Interface; Distraction; Confusion; Training / Qualification; Communication Breakdown
Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem
Aircraft; Human Factors
Departing Runway 19R from LAS on the COWBY 5 RNAV Departure. Before takeoff we briefed the RNAV departure including the retraction at ROPPR between 5;900 and 7;000 and discussed the used of LNAV and VNAV after climbing through 400 FT AGL. The takeoff and initial climb were accomplished without incident and LAS Tower handed us off to Las Vegas Departure. After our check-in Departure instructed us to disregard the climb restriction at ROPPR and as the pilot not flying I deleted the restriction in the FMS. At this time the pilot flying had already engaged the autopilot and the Flight Director was in LNAV/VNAV. He then asked me if there were any speed restrictions on the departure. We had not briefed any speed restrictions and I did not remember seeing any when I reviewed the chart. I elected to look at the chart and confirm there were no speed restrictions. At this time the pilot flying stated something to the effect that the autopilot was leveling off even though I had deleted the restriction at ROPPR. I looked up from the chart and noted that the FMS speed bug had moved from 200 KTS to 250 KTS and stated that it was just increasing speed to the 250 KTS. I had NOT observed that the pilot flying had reduced power to maintain a reasonable climb rate at 200 KTS when I returned to looking at the chart to verify there were no speed restrictions on the departure. I confirmed there were no speed restrictions. When I looked back at the instruments I saw that we were now descending through 5;300 FT as we approached ROPPR and that is when I saw that the pilot flying had the power reduced. I stated that he needed to increase power in order for the autopilot to climb and he replied that the airspeed was now at 250 and 'it' should be climbing as he increased the power slightly and asked me what the next crossing restriction was. I looked at the chart and saw that CEASR was at or above 8;000 FT and only 7 miles away. I told the pilot flying this information and that we needed to climb now (at this time we were at approximately 5;000 FT) simultaneously ATC advised us of a low altitude alert for terrain and to expedite our climb. At this point the pilot flying reverted to VS mode and selected 2;500 FPM climb and increased power to the climb detent and I acknowledged ATC and confirmed we were climbing expeditiously. We crossed CEASR at approximately 8;200 FT. The remainder of the flight was concluded without further incident.The VNAV function of the Excel/XLS is often misunderstood or not fully understood. During climb VNAV will maintain a programmed airspeed until it reaches an 'at' or 'at or below' altitude; at which point it will level off. VNAV during a climb will not deviate from the programmed airspeed in order to ensure it reaches an 'at or above' or 'at' crossing restriction. It is the pilots' responsibility to ensure power is set high enough so that the aircraft will have sufficient climb performance to meet those restrictions.The pilot must also be aware that the aircraft is normally programmed to climb at 200 KTS until reaching 2;500 AGL at which point the aircraft will increase its speed to 250 KTS. If power is set too low for the aircraft to continue to climb and maintain 250 KTS it will level off or even descend in order to achieve 250 KTS. Although it may be good technique to reduce power while the aircraft is climbing at 200 KTS in order to maintain a reasonable rate of climb; you must be prepared to increase power for the transition to 250 KTS. And if; due to weight or temperature; you cannot maintain a climb that is sufficient to meet the crossing restriction you can either type a slower speed into the FMS or revert to VS mode and climb at a greater rate. I feel that if I had been focused more on the instruments I could have coached the pilot flying sooner and not allowed the situation develop as much as it did. That being said I also feel that it is important not to rely on memory and to confirm ifprocedural information is in doubt. Unfortunately the chart for this procedure is rather complex and it takes time to properly review.
A CE560XL; departing LAS via the COWBY RNAV SID suffered a CFTT incident when ATC deleted the crossing restrictions at ROPPR and the pilot flying flying failed to insure adequate thrust settings to continue the climb after the pilot not flying deleted the crossings from the FMS. A low altitude alert from ATC re-energized the flight crew's awareness.