Large Transport
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 208
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance
Flight Crew Overcame Equipment Problem
Procedure; Aircraft
On the JANNY3 Arrival we leveled at FL240 passing the JOEES waypoint. As the aircraft started to descend to meet the DNUTT FL230 restriction it started to level off at FL23.8 then start down again. This put us off path. I selected Vertical Speed to try to make the restriction but was unable to make it and crossed it about 500 feet high. I'm not sure why the aircraft did not make the restriction. I felt like the arrival was correctly programmed. The bad part of having an arrival with 1000 foot step down between points is that if there is any problem; you have no room to correct the error and still make the restriction with only three miles between descent point and crossing altitude restriction.
LNAV/VNAV path was engaged and all altitudes verified on the LEGS page in the FMC. The first Top of Descent was three miles from the DNUTT waypoint. DNUTT crossing altitude was FL230. The aircraft began a descent then leveled off 800 feet high (which the Pilot Flying and Pilot Not Flying did not expect). The Pilot Flying intervened with vertical speed; but we still crossed DNUTT 400 feet high.
Air Carrier flight crew reported that while descending on the JANNY3 Arrival into BUR with LNAV/VNAV engaged; the aircraft leveled momentarily resulting in crossing DNUTT 500 feet high.