EMB ERJ 190/195 ER/LR
Flight Crew Air Transport Pilot (ATP)
Time Pressure; Human-Machine Interface; Workload
Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Aircraft; Chart Or Publication; Procedure
On initial contact with Boston Approach; were given the KRANN 3 Arrival; descend via Runway 27 transition. We had already flown into BOS earlier in the day and had flown the same arrival and approach. All required briefings for the arrival and approach had been completed; as well as the Descent Approach checklist. On that arrival; we had experienced a common phenomenon on the E-190 wherein the aircraft has 'difficulty' making crossing restrictions below 10;000 FT. For the Runway 27 transition; the aircraft has 28NM to descend from 11;000 FT to 8;000 FT while slowing from 270 KIAS to 250 KIAS. This is significantly better than the 33L transition; with only 17NM.On the previous leg; with full automation LNAV/VNAV; the aircraft remained at 11;000 FT too long. Because of the strong tailwind component; we had programmed a descent angle of 2.5 degrees instead of the standard 3.0. The aircraft followed the VNAV path from 11;000 FT to 10;000 FT then slowed to 250; deviating well above the path. Crew intervention requiring full speedbrakes was required to make the crossing restriction. On this flight; all required arrival and approach briefings had been completed as well as the descent approach checklist. The only difference was that instead of leaving the default ANSLY crossing altitude as 8;000 FT or above; I changed it to 8;000 FT. This time after crossing KRANN at 11;000 FT and 270; the aircraft started down a path which was steeper than 2.5 degrees (3;000 feet in 8NM). Coupled with the 40 knot tailwind; the aircraft needed a high vertical speed descent and full speedbrakes to make ANSLY at 8;000 FT. I had asked the FMS to deliver the impossible. Usually the E-190 respects the 10;000 FT 250 restriction over lower crossing restrictions; but not this time.  Thrust at idle; 3/4 Speedbrakes; at a high rate of descent; the aircraft deviated from the vertical path; unable to arrest the descent at 8;000 FT. The speed had remained above 250 and the aircraft descended to 7;640 as I used TCS to gently return the aircraft to the desired path as the engines spooled. The obvious cause of this incident is my changing the crossing restriction and delayed intervention. Many of the arrivals we fly have a common problem. While a constant descent and gradual deceleration to 250 knots at 10;000 FT and continued descent below looks good on paper; the E-190 just cannot operate that way. When the procedure and the conditions do not permit the aircraft to simultaneously make a crossing restriction and a speed restriction; the result is that often that it delivers neither. Look at LGA's HAARP at BAYSE. That arrival combines a crossing restriction below 10;000 FT with a sharp turn. The result is the aircraft is about 1;000 FT high. Try flying BOS KRANN 3 at BEREI and BBOGG with a tailwind greater than 15 knots or a speedbrake on MEL. The KAROO into RDU has similar issues for GAZER and FOBAT. Ironically; my solution in such arrivals is similar to the cause of the problem for this arrival. What I should have done was worked backward from KLEBB. Knowing that I needed to cross KLEBB at 8000/250; I needed to be at 10;000/250 at CRADL. Allowing for a 20 knot deceleration segment means 3 Miles prior to CRADL at 10;000 FT. EVERY arrival needs a 10;000 FT crossing point and a level segment at 10;000 FT before continuing to lower restrictions.
An ERJ-190 Captain describes how that aircraft's FMS design makes complying with the BOS KRANN 3 and LGA HAARP crossing restrictions below 10;000 FT difficult. Both Arrivals' profiles require a deceleration to 250 knots followed by a crossing constraint in too short a distance.