Date: 201410
Local time of day: 1201-1800
Location: ZME.ARTCC, TN
Flight conditions: IMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Learjet 45
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B MEM
ATC / advisory: Center ZME
Aircraft component: FMS/FMC
Component problem: Design
Reporter organization: Corporate
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Situational Awareness; Distraction
Second reporter function: Captain; Pilot Not Flying
Anomaly: Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Aircraft; Procedure; Human Factors
Primary problem: Human Factors

Narrative: After avoiding weather in the Memphis area we were cleared direct to the Vanze intersection and later cleared to descend via the SID.  The single FMS in the aircraft is a UNS1C (Universal) which does not have the capability to intercept the VNAV and fly the vertical track throughout the SID.  Our company has another aircraft which we fly much more often that has two UNS1Es that automatically adjusts for the various vertical descents between fixes.  since it is flown more often; and in an effort to promote standardization; when a 'descend via' clearance is received the altitude select is scrolled to the lowest altitude on the SID.  We followed this procedure and monitored and adjusted accordingly until around the Larue intersection.  I was the pilot flying and we were in IMC conditions.  The Captain switched frequencies to check the ATIS for updated weather.   We had several young children on board who were screaming and causing quite a scene in the back.  We were both distracted and ATC called with a climb immediately to 7000 feet.  We did not get any TCAS warnings or RA's.  We were told caution wake for a nearby [heavy] jet.  We did not experience any wake.  I know that the Captain and Director of Operations are planning a new procedure for 'descend vias' with the aircraft so that there will be an extra layer of protection to an altitude alerter.  I can assure that I will never let this happen again on my part.


Second narrative: After avoiding weather in the Memphis area we were cleared direct to Vanze intersection and later cleared to descend via the SID. The single FMS in the aircraft is a UNS1C (Universal) which does not have the capability to intercept the VNAV and fly the vertical track throughout the SID. Our company has another aircraft which we fly much more often that has two UNS1Es that automatically adjusts for the various vertical descents between fixes. Since it is flown much more often; and in an effort to promote standardization; when a 'descend via' clearance is received the altitude select is scrolled to the lowest altitude on the SID. We followed this procedure and monitored and adjusted our altitude accordingly. I was in the right seat and as we continued to be in IMC conditions; about Larue intersection I switched to check on the ATIS for updated weather. As I was listening for that info the passengers; a young mother and four under 10 year old boys began screaming boisterously in the back of the airplane distracting both of us. By the time I had addressed the situation in the back and I was returning to monitor the ATIS; the FO who was flying the airplane recognized the altitude error.At that time we were called by ATC and given a hard altitude of 7000 ft and a heading for vectors into Memphis. We got no TCAS warning or RA but were told to beware of Wake turbulence from a Jet nearby. We never experienced any.As a Check Airman; and a company instructor on this airplane I believe our effort at standardization to improve safety must be mitigated by the reality that scrolling the altitude to the lowest altitude on the arrival removes the value of the altitude alerter to notify the crew when they are both reaching an altitude and passing beneath a set altitude.As Director of Operations I will implement immediately that any aircraft that enters our fleet that is not capable of vertical 'descend via' adjustments within the FMS; will be handled as individual step down altitudes and the step altitudes will be set in the altitude select for each leg of descent. This will add the extra layer of protection of the altitude alerter and be active in the background when such distractions occur in the future.


Synopsis: Corporate jet flight crew describes and altitude deviation during the VANZE 1 arrival to MEM; due to distractions from the passengers and the inability of the FMS to fly the vertical profile. The altitude alerter is set to bottom altitude for the procedure for standardization and provides no warning of the deviation from the profile.