Light Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Distraction; Confusion; Workload
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Procedure; Chart Or Publication
On departure from IAH issued the MMUGS ONE departure to climb via SID per PDC. Reviewing the SID the pictorial shows at or below 11;000 at GRAYN. The route description in text gives headings and altitudes for TTAPS at or below 4;000 and BOTLL [at] or below 5;000 thence. Then down below it has the rest of the route that reads on track 090 to MMUGS then on (transition). Maintain 4;000. Expect filed altitude 10 minutes after departure. This information is in 3 separate locations and clearance is issuing a PDC wit the verbiage climb via and not specifying a hold down altitude. The maintain 4;000 is in the last place you look and refers to MMUGS which is past the pictorial and route description that has you climbing to 5;000. The SID description is poorly written and information is disjointed and in too many places. I was given a number to call and did; I was asked what happened and I explained. I was told there were two other deviations within 30 minutes of mine for a total of 6 for the day. The text needs rewriting with pertinent information in same place. They should not be clearing you climb via SID if not going to utilize it. They should send the PDC climb via the SID to maintain 4;000.
The White Lake (LLA) transition requires one to cross GRAYN at or above 11;000. Then the textual description states on track to MUGGS maintain 4;000. When we interpreted the 'climb via SID' clearance; we understood that to mean cross TAPPS at or below 4;000; MUGGS at or below 5;000; then GRAYN at or above 11;000. What was not understood until after the fact; due to ambiguity between graphic/textual/and PDC was the need to level off at 4;000 FT and await further clearance to higher altitude at fixes beyond TAPPS. This resulted in an altitude deviation of 500 FT; from 4;000 FT MSL after TAPPS; while climbing to cross MUGGS at or below 5;000 FT MSL as per the graphic. Aircraft separation was not compromised and no evasive action was required. Was asked to contact ATC via telephone and wished 'good luck' by the Controller who made us aware of the deviation. ATC; via telephone; admitted there were 6 deviations from the 'climb via SID' clearance on this MUGGS1 departure on today's date alone. This indicates that many flight crews are confused by the ambiguity in the procedure; as well as ATC procedures and phraseology. There is a very ambiguous disparity between the instructions as written in the graphic and textual description of this SID. The procedure needs to be re-written to eliminate the ambiguity and to make the instructions more clear. Also; descend via STAR and climb via SID procedures are new to the Houston area airports. I believe both pilot training and ATC training needs to focus on using these clearances correctly.
A Corporate Jet flight crew reported the disparity between graphic and textual crossing restriction on the MUGGS One IAH RNAV Departure.