Narrative:

Enroute to lga on the haarp one arrival; we crossed bdl at 16;000 due to turbulence above and request by boston center due to traffic. Approximately 20 NM south of bdl; we were instructed to cross basye at 9;000. The wind was from the north; varying in direction from 340 to 360 true from 5 to 7 KTS; causing continuous light chop. The perf init page had been programmed for the standard descent speed of 290 KTS/.76M and 3.0 degree angle. During the cruise and descent portions of the flight; full automation was utilized: the autopilot and auto throttles were engaged with FMS speed; LNAV and VNAV flight guidance modes. The 9;000 ft crossing restriction had previously been entered into the mcdu flight plan page; and the altitude select was set to 9;000. Standard altitude awareness procedures were followed; including verifying 'big (font) pink (mcdu display) and TOD (nav display and prog page 2)'. In addition; the 9;000 restriction was displayed on the vertical profile on both navigation displays. The first officer stated an estimated top of descent which I confirmed. We then began to brief the approach and enter the landing data for the expressway visual approach into lga. During the briefing; the pink FMS vertical deviation indicator appeared followed by an aural alert. At the depicted TOD; the aircraft began its descent to 9;000. We resumed the briefing items and the checklist. Up until 5 miles from valre intersection; all indications were normal; and we fully expected to meet altitude and speed restrictions. The FMS showed no deviation from the lateral or vertical path. Approximately 5 NM north of valre; the aircraft began a left turn to intercept the dpk 338 radial for the 158 course to basye...a 103 degree course change. The distance from valre to basye is only 7 NM; and the aircraft was flying an arc; cutting the corner. The FMS vertical deviation began dive; indicating we were too high. Midway through the turn; the lateral deviation indicated 2.0L. This coincided with my progress indication of 1.9 NM to valre. Until the aircraft had turned halfway and cycled the valre waypoint; the EFIS and mcdu provided no indication that we would not cross basye at 9;000. Once valre was cycled; the aircraft was in a position approximately 3 miles north of bayse at 10;000 ft and 270 KTS. Even with full speed brakes; we were too high and too fast; crossing at 10;000 and 250 KTS. Quite simply; the aircraft automation appears incapable of calculating a descent when a significant speed change and course change is involved. The crew has neither the means nor the time for analytic geometry to calculate arc segment vs. Linear distance. All indications were normal until the aircraft was almost half-way through its turn. At that point; it was already too late to make the restriction without aggressive handling. As it was; aside from deploying the speed brake; we did not intervene. We could have used vs or fpa to make the 9;000 ft restriction; but bust 250 KTS below 10;000. The FMS evidently calculates a descent based upon a linear model; in this case; approximately 8 miles were eliminated by the leading turn. An FMS overfly at valre or prior to basye or moving the crossing restriction to valre would have helped (although not entirely eliminated the problem). An alternative solution is to reduce the level of automation by selecting a fpa (flight path angle) or vertical speed descent and to move the TOD 10 NM earlier than the FMS calculated position. Typically; boston center or new york approach give a direct or a vector prior to the tight turn; so this is rarely a factor in line operations; but the fact remains that full automation is simply not capable of flying the procedure as charted; and a short segment like this one is the last place for a pilot to attempt to calculate a conic section. It is also unfortunate that other pilots have experienced this same problem; yet this knowledge has not been institutionalized. A simple message on the flight release 'use fpa or vs descent only for haarp one at valre' will be beneficial.

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Original NASA ASRS Text

Title: EMB190 Captain discovers that his aircraft's FMC cannot properly fly the HAARP 1 arrival into LGA from over BDL. The FMC begins a gentle turn well before VALRE and does not make the crossing restriction at BASYE.

Narrative: Enroute to LGA on the HAARP ONE arrival; we crossed BDL at 16;000 due to turbulence above and request by Boston Center due to traffic. Approximately 20 NM south of BDL; we were instructed to cross BASYE at 9;000. The wind was from the north; varying in direction from 340 to 360 true from 5 to 7 KTS; causing continuous light chop. The PERF INIT page had been programmed for the standard descent speed of 290 KTS/.76M and 3.0 degree angle. During the cruise and descent portions of the flight; full automation was utilized: the autopilot and auto throttles were engaged with FMS Speed; LNAV and VNAV flight guidance modes. The 9;000 FT crossing restriction had previously been entered into the MCDU flight plan page; and the Altitude Select was set to 9;000. Standard altitude awareness procedures were followed; including verifying 'Big (font) Pink (MCDU display) and TOD (Nav display and Prog page 2)'. In addition; the 9;000 restriction was displayed on the Vertical Profile on BOTH navigation displays. The First Officer stated an estimated top of descent which I confirmed. We then began to brief the approach and enter the landing data for the Expressway Visual approach into LGA. During the briefing; the pink FMS vertical deviation indicator appeared followed by an aural alert. At the depicted TOD; the aircraft began its descent to 9;000. We resumed the briefing items and the checklist. Up until 5 miles from VALRE Intersection; all indications were normal; and we fully expected to meet altitude and speed restrictions. The FMS showed no deviation from the lateral or vertical path. Approximately 5 NM north of VALRE; the aircraft began a left turn to intercept the DPK 338 radial for the 158 course to BASYE...a 103 degree course change. The distance from VALRE to BASYE is only 7 NM; and the aircraft was flying an arc; cutting the corner. The FMS Vertical Deviation began dive; indicating we were too high. Midway through the turn; the lateral deviation indicated 2.0L. This coincided with my PROGRESS indication of 1.9 NM to VALRE. Until the aircraft had turned halfway and cycled the VALRE waypoint; the EFIS and MCDU provided no indication that we would not cross BASYE at 9;000. Once VALRE was cycled; the aircraft was in a position approximately 3 miles north of BAYSE at 10;000 FT and 270 KTS. Even with full speed brakes; we were too high and too fast; crossing at 10;000 and 250 KTS. Quite simply; the aircraft automation appears incapable of calculating a descent when a significant speed change and course change is involved. The crew has neither the means nor the time for analytic geometry to calculate arc segment vs. linear distance. All indications were normal until the aircraft was almost half-way through its turn. At that point; it was already too late to make the restriction without aggressive handling. As it was; aside from deploying the speed brake; we did not intervene. We could have used VS or FPA to make the 9;000 FT restriction; but bust 250 KTS below 10;000. The FMS evidently calculates a descent based upon a linear model; in this case; approximately 8 miles were eliminated by the leading turn. An FMS overfly at VALRE or prior to BASYE or moving the crossing restriction to VALRE would have helped (although not entirely eliminated the problem). An alternative solution is to reduce the level of automation by selecting a FPA (Flight Path Angle) or Vertical Speed descent and to move the TOD 10 NM earlier than the FMS calculated position. Typically; Boston Center or New York Approach give a direct or a vector prior to the tight turn; so this is rarely a factor in line operations; but the fact remains that FULL automation is simply not capable of flying the procedure as charted; and a short segment like this one is the last place for a pilot to attempt to calculate a conic section. It is also unfortunate that other pilots have experienced this same problem; yet this knowledge has not been institutionalized. A simple message on the flight release 'Use FPA or VS descent ONLY for HAARP ONE at VALRE' will be beneficial.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.