Learjet 45
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor
Flight Crew Last 90 Days 100; Flight Crew Total 10000; Flight Crew Type 150
Workload; Confusion; Human-Machine Interface; Situational Awareness
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Procedure; Aircraft; Airspace Structure; Chart Or Publication; Human Factors
I question the design of this arrival; specifically the descent profile [between] HOMRR intersection and VNNOM intersection.Today after crossing HOMRR at 16;000 feet and 250K; I discovered that I was unable to cross VNNOM at 11;000 feet. Why was that? The reason was that the two intersections are only 4.1 nm apart. That takes a minute at 250K and would require a 5;000 FPM descent rate. While my aircraft is capable of descending at that rate; to do so that quickly would have required some extreme pitch changes; negative G forces; and created a hazard for my passengers.After further review of the procedure I noticed that the procedure gave us the option of crossing HOMRR at a lower altitude. With the experience of flying it once behind me; I would be able to anticipate this and would do just that.That brings me to my original point that this procedure needs to be better designed as I believe it is overly complex. From the time I leave cruise altitude until joining the approach; I have 9 crossing restrictions and 3 airspeed adjustments to plan for. Seven of the crossing altitudes introduce an additional complication of giving me a block of altitudes at which to make the crossing. My FMS is a wonderfully capable device; but it does not know how to cross a fix at more than one altitude. This requires me to manually program all these crossing restrictions and determine what altitude I wish to enter.Suffice to say that makes this a very busy arrival for both pilots and a tricky nuance like the HOMRR to VNNOM transition is hard to foresee and plan for.Two suggestions here. At the very least; please fix this specific problematic procedure. Better yet; simplify these procedures. If it is necessary to fly this with so many requirements; make the requirements more straightforward. Do away with the block altitudes and at or below and make sure that aircraft can actually meet all that ATC is asking.
A Lear 45 flight crew; lacking sophisticated autoflight VNAV and autothrottle availability; failed to make the crossing restrictions at VNNOM on the EAGUL RNAV STAR to PHX. The reporter cited the excessive complications of this and other complex RNAV STARs; which require excessive flight crew workload to reconfigure and program their FMS to meet those demands.