Gulfstream V / G500 / G550
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 18250
Workload; Situational Awareness; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Deviation - Altitude Overshoot; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action; Flight Crew Returned To Clearance
Airspace Structure; Procedure; Aircraft
While departing Teterboro Airport in day VMC conditions on the RUUDY 4 RNAV Departure; we exceeded our initial level-off altitude of 1;500 FT by 160 to 180 FT (copilot's altimeter vs. pilot's altimeter.) At approximately 800 FT we received a TCAS TA alert and noted an amber target about 3 miles behind us and 1;200 FT above us. I have been flying in and out of Teterboro for 27 years and am very aware of the critical need to NOT BUST that 1;500 FT mandatory altitude when departing Runway 24 due to the proximity of arriving Newark traffic over-flying our departure path. Further; having availed ourselves of training videos for the pilot community utilizing Teterboro; we were aware that most level busts on our departure route occur on spectacular VMC days just like the one we had on departure. As a result the crew thoroughly briefed the departure procedure. So what happened? One factor was that we were very light due to the short leg and the desire to land at destination as light as possible due to our destination's short runway (5;090 FT). Next; due to the length of Teterboro runway and noise abatement consideration/procedure; we utilized Rated Takeoff Power (Maximum Power); autothrottles; and Flaps 20 degrees. As a result we had great takeoff and climb performance. In our brief this was noted as both a strength and a weakness; a strength as it related to runway required and noise abatement performance and a weakness in terms of our need to level off at 1;500 FT. This was discussed and it was determined we would take two actions to address this weakness. The first was to leave the flaps at 20 degrees until after we were cleared above 2;000 FT (the second altitude restriction) in order to decrease the workload on the pilot not flying. The second mitigation strategy was to engage the autopilot at 500 FT to let it perform the level off. That turned out to be a mistake. Every time I had executed that departure in the past I had done so manually with no problems. However; in this case I was attempting to see if utilizing the autopilot to decrease our workload would allow us to better monitor the level off. Initially all went well as the autopilot was engaged at 500 FT and the aircraft immediately began its level off. Unfortunately; with our performance; it was quickly evident the autopilot was not going to keep us below 1;500 FT. Upon realizing this I disconnected the autopilot and autothrottles while abruptly reducing thrust to idle and pushing over to minimize the altitude exceedences. There was no communication from Approach regarding the bust. In fact I'm not sure it qualified as an official bust. The purpose of the ASRS report is to bring to the communities attention the downside of utilizing the VNAV climb function when leveling off so soon after takeoff; especially if you are very light. The departure procedure calls for a level off at 1;500 FT until passing a close in intersection and then climbing to maintain 2;000 FT by the next intersection. We discussed whether or not to 'back ourselves up' by putting 1;500 FT in the altitude window of the flight guidance panel or putting 2;000 FT in the window and allowing VNAV to fly the departure. We had become very confident in the VNAV automation function and decided to put 2;000 FT in the window AFTER VERIFYING 1;500 FT was indicated in the FMS and on the PFD. In the end; due to our light takeoff weight and early level off requirement; I believe we put the autopilot in a position it simply was not designed to handle. In the future I will stick to using what has worked when performing a critical maneuver while utilizing the simulator to test; AND PERFECT; any new procedures.
After departing on the TEB RUUDY 5 RNAV; the Captain of a GV engaged the autopilot at 500 FT; but exceeded 1;500 FT by about 180 FT; so the autopilot was disconnected and the aircraft returned the constraint.