B717 (Formerly MD-95)
Flight Crew Air Transport Pilot (ATP)
Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem
Aircraft
Here is the setup:  1) I have had this happen on different aircraft over the last 3 months or so.  It coincides with the introduction of the KRANN ONE RNAV arrival into Boston.  2) Usually what happens is we pre-program the entire route on the ground; via OOD then   J42 RBV J222 JFK KRANN1 BOS.  I either program no approach or I put in the 4R ILS BOS.  3) We depart normally and Departure Control turns us towards OOD then clears us direct.  4) We are cleared up to FL230 and the Autopilot is engaged.  The FMA is all magenta indicating FMS controlling Speed; Lateral Navigation; Level off altitude.  We are in CLB1 thrust.  5) Going through ~10;000 MSL; the FMS stops the climb and starts an UNCOMANDED LEVEL OFF and reduces speed to something like FMS Speed 210 KIAS.  Due to our rate of climb the FMS level off altitude can be anywhere from 10;500' msl to about 12;000 msl.  6) In order to keep the aircraft climbing I have to remove the FMS from the equation:  I White Bow Tie everything except lateral NAV by Setting Speed 300 KIAS and Setting ALTITUDE 230 (by pulling the knobs on the FCP).    7) Once the aircraft is climbing again I start to look at FMS to see what is going on.  8) INIT page 1 shows the cruise altitude has dropped out and has been replaced by 3 dashes (---).  9) Going to the PERF page shows the the FMS is in the DESCENT mode.    10) Re-initiating the cruise altitude does nothing.  It will not take and the FMS remains in the DESCENT mode.  11) The first time this happened it was at night and there was traffic and weather and I had no time to troubleshoot the FMS.  I white bow tied the FCP the rest of the flight.  Attempts to get the box back in the CLIMB mode or once we were at cruise; in CRUISE mode proved fruitless.    12) On a subsequent BOS flight I notice that the KRANN arrival has manual heading that is annotated differently than every other MANUAL heading on every other arrival in the database.  In Atlanta on the FALCON arrival; for example; the Flight Plan Page shows a manual heading of 'heading 275' or whatever it is.  On the KRANN ONE arrival; after KRANN intersection it shows on the Flight Plan Page 'KRA075' instead of the normal 'heading 075'.    13) After this happened again today; on a hunch; while still in the climb I deleted the MANUAL after KRANN intersection leaving the above mentioned route and crossing altitudes to KRANN and then a Flight Plan Discontinuity and then the outer most fix of the ILS 4R approach; WINNI and the rest of the approach.  The results were immediate and positive.  14) I could now re-Init the cruise altitude on the INIT page 1.   The FMS once again showed Climb mode when pressing the PERF page and I was able to toggle the PERF button to show the CRUISE and DESCENT pages on the PERF part of the FMS.  FMS operation for the rest of the flight was normal. Conclusions:  1) The NAV DATABASE with the KRANN1 arrival to BOS in our 717-200 FMS is corrupting the normal operation of the FMS.  It has to do with the MANUAL KRA075 after KRANN intersection.    2) Our use of this arrival should be terminated immediately or the MANUAL deletion 'work-around' should be published to the 717 pilot group.  3) There are other new RNAV arrivals into BOS which may also have the same corruption.  This needs to be investigated.    4) The manufacturer of the NAV Database should be contacted to find out what they are doing differently on the KRANN RNAV arrival that is causing this.
B717 Captain describes anomalous FMS operation that seems to occur only when the KRANN1 arrival to BOS is loaded.  When the MANUAL track after KRANN is deleted the The FMS returns to normal operation.