Flight Management, Navigation -Flight Management System Operation
737 Operations Manual
VNAV Cruise and Path Descent Profile (Nonprecision Approach)
Copyright . The Boeing Company. See title page for details.
June 8, 2001 11.31.23
Flight Management, Navigation -Flight Management System Operation 737 Operations Manual
Cruise
Before the top of descent, FMC is in cruise mode and uses VNAV PTH and ECON cruise speed.
Descent
After top of descent, FMC is in descent mode and VNAV changes to economy descent speed and descends in VNAV PTH.
Speed Restriction Deceleration
Before the speed restriction altitude, VNAV decelerates to commanded speed
using VNAV PTH.
When at restricted speed, VNAV commands decreased pitch and descends in
VNAV PTH.
Altitude Restrictions
The VNAV path conforms to altitude restrictions at MNO, EPG, and the FAF. If required, VNAV uses a level path until intercepting the idle thrust descent path to the next altitude constrained waypoint.
Approach
VNAV descends and starts approach in VNAV PTH at the commanded speed.
Missed Approach (U7 and on)
When TOGA is pushed during approach, or when crossing the missed approach point, VNAV disengages.
When VNAV is selected during missed approach, VNAV engages in VNAV SPD.
Missed Approach Level Off (U7 and on)
At missed approach altitude VNAV changes to VNAV PTH.
VNAV Speed Descent
A speed descent may be selected manually by selecting the SPEED prompt on the PATH DES page. With no E/D specified, the speed descent is the only descent mode available.
(Prior to U5) The descent must be initiated manually by resetting the MCP altitude, selecting the CAPTURE prompt on the descent page, and executing.
Copyright . The Boeing Company. See title page for details.
11.31.24 June 7, 2002
Flight Management, Navigation -Flight Management System Operation
737 Operations Manual
The speed descent maintains the target speed and makes no attempt to modify pitch for vertical path considerations. Normally, the target speed is economy above the airspeed restriction altitude and 240 knots below that altitude, until deceleration is necessary for approach. VNAV will not permit descent below the altitude restriction until the airspeed is at or below the restricted value.
(U5 and on) The speed descent normally begins automatically at the calculated T/D, provided the MCP altitude is reset for the descent. At the T/D, the FMC commands pitch to maintain target speed. LNAV does not have to be engaged in order to fly a VNAV speed descent.
The descent attempts to comply with waypoint altitude restrictions, and will not violate these restrictions. The VNAV speed descent will not, however, guarantee the airplane reaches an altitude restriction at the required point.
A speed descent cannot automatically revert to a path descent, except with a U7 or later FMC installed and during a STAR, approach transition, or approach leg with a vertical angle leg. However, if all required parameters for a path descent are available, a path descent may be manually selected at any time by selecting the PATH prompt on the speed descent page.
Flight Management, Navigation -Flight Management System Operation 737 Operations Manual
VNAV Cruise and Speed Descent Profile (Nonprecision Approach)
Copyright . The Boeing Company. See title page for details.
11.31.26 June 8, 2001
Flight Management, Navigation -Flight Management System Operation
737 Operations Manual
Cruise
Before the top of descent, FMC is in cruise mode and uses VNAV PTH and ECON cruise speed.
Descent
After top of descent, FMC is in descent mode and VNAV decelerates to economy descent speed and descends in VNAV SPD.
Speed Restriction Deceleration
Before the speed restriction altitude, VNAV decelerates to commanded speed
using VNAV SPD.
When at restricted speed, VNAV commands decreased pitch and descends in
VNAV SPD.
VNAV Path
During a speed descent, VNAV may not maintain the FMC computed VNAV path. However, if E/D shows, a VNAV path is available.
Altitude Restrictions
VNAV conforms to altitude restrictions at MNO and EPG. After MNO VNAV
continues an idle thrust descent using VNAV SPD.
Upon reaching the next altitude restriction, VNAV commands level flight using
VNAV PTH. The thrust mode changes to FMC SPD.
Descent and Approach
After EPG, VNAV continues the idle thrust descent using VNAV SPD.
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