Date: 201704
Local time of day: 1201-1800
Location: APA.Airport, CO
Flight conditions: VMC
Light: Daylight
Aircraft: Light Transport
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E D01
ATC / advisory: TRACON D01
Reporter organization: Corporate
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Distraction; Situational Awareness; Training / Qualification; Workload
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airspace Structure; Chart Or Publication; Procedure; Human Factors
Primary problem: Chart Or Publication

Narrative: I was flying the PUFFR.PUFFR4 RNAV Arrival into Denver's Centennial Airport. I have flown this procedure many times in the past and am actually quite familiar with this arrival. I am kicking myself over this flub-up because I got caught up in helping a relatively new jet pilot learn the intricacies of flying an RNAV arrival and using the old school; but very helpful 3 to 1 descent planning and execution. The emphasis on this arrival was the descent planning and of course complying with the published restrictions.I will jump ahead here before I list the details of my flub-up. When I was asked to call the TRACON I asked the Controller a question or two. I knew the answers before I asked; but I asked these questions anyway. (1) Was I the first to have made this mistake? I said it is rare for me to be the trailblazer in the mistake department. There are usually pilots that had blundered the same mistake before me and there will probably be others to follow. (2) I took full responsibility; but when I asked ATC for the relief on the altitude restriction why didn't they say something RIGHT NOW. They knew I was blundering; but made no mention of it.I said that I have a partial fix to this RNAV Arrival that could offer some relief to perhaps a large percentage of the flub-ups. Please excuse my use of the word flub-up. I can't think of any other at the moment! Please refer to the PUFFR.PUFFR4 RNAV arrival that pertains to landing on Runway 17L at Centennial airport. This arrival when landing to the south is very intense. It is a high energy; go down and slow down arrival when landing south. When landing to the north it takes forever and you have time to knit a sweater; landing south it is a different matter and it is a poorly designed arrival.My last statement was confirmed by the Denver TRACON Controller who mentioned there are a lot of issues with this procedure. As I write this; I still take full responsibility; but I suggested to the TRACON a possible solution that will help with future pilots conducting this approach.Take out all fixes not associated with an altitude or speed restriction. Eliminate the SLMON FL210 restriction and show the SAYGE restriction at a hard FL210. If possible show the holding pattern at SAYGE and eliminate the SLMON fix altogether on this procedure. Either change the turning point at FFFAT to transition to landing on Runway 35R to DHATT which has the crossing restriction of 15;000 feet which would conform to the LADDA at or above 13;000 feet restriction and then the only restriction at HUUKK would be a speed change/reduction to 210 knots. If they can't make the changes I am suggesting simply use the coding PUFFR.PUFFR4 for landing on Runway 17L. That arrival would not have the intersection of FFFAT depicted. For landings required on Runway 35R; have a new procedure that is identical to the PUFFR.PUFFR4; but it would be used only for that runway. I suggest they call it the FLLUB.FLLUB4 for Runway 35R at APA.The reason I flubbed-up was because this arrival is overly complex and of course I could have done better. My goal is to print out this arrival and make the suggested changes and drive them over to the TRACON. I know it is not an easy thing to change a procedure; but this must be done. Why and how did a seasoned and usually very successful aviator make such a stupid mistake?We crossed SAYGE at FL210; MOKME at 17;000 feet and DHATT at 15;000 feet. All was well and I do not remember what took place; but as a guess between my flight instructing; running the approach checklist; perhaps a frequency change; sneezing. I looked at the distance to the next fix and said; we have got to get down to make the CREEQ crossing restriction. When it looked doubtful I asked approach for relief on the 11;000 foot CREEQ restriction. When I called on the telephone after the flight; I was told I asked for this when we were descending through 12;400 feet. I place no blame on the Controller; but I sure wish they would have told me I was messing up. They could have even said I was flubbing-up and stop your descent. How about 'climb and maintain 13;000 feet; you obviously need help flying this procedure!Of course what I did was I believed that FFFAT was the LADDA intersection. The airplane I was flying has an old Universal UNS-1D FMS and unlike the more modern displays doesn't show the altitude restrictions in printed form on the map. I have always said that there is nothing difficult to flying airplanes. If you take each and everything we do individually it isn't so hard. I guess you can say that about most occupations; flying; Air traffic Controlling; etc. But; when you put everything together it can get complex and of course once you fixate on one thing; you are destined to miss something important. That of course was I got ahead of myself and confused fixes.The fix I confused is a fix that does not even matter for the arrival and the runway we were going to land on. Get rid of FFFAT when landing to the South or as I suggested make the turn at DHATT. I am at the mercy of the higher ups on this one. I am a career aviator and must fly for a living for many years. What I would give to know that this flub-up perhaps might help others and I am off the hook. It just popped into my head the movie 'Catch Me If You Can'. You know where they put Frank in jail and then later the FBI realizes that he might be able to help them catch other crooks. I am not saying that I'm as good as Frank in writing hot checks; but I will offer my services to help the FAA clean-up RNAV arrivals anywhere where there is a history of possible pilot deviations. Similar to the hot spots on Airport Diagrams; could these reoccurring issues be highlighted on all instrument procedures plates?




Synopsis: A pilot reported he confused the fixes on an RNAV STAR and descended below a published restriction of the RNAV STAR.