[Janicki]

Basic Changes: 1. Fly-by Hold Entries and Exits
Version U10.7 of the FMC OPS calculates fly-by hold entries and exits that are available when the path geometry is permitted. Before U10.7, only fly over entries and exits were calculated. When the hold pattern is set, the airplane will over-fly the fix on all circuits of the holding pattern until it exits. Fly-by hold entry and exit gives better Required Navigation Performance (RNP) in U10.7. The airplane can stay on the holding side of the hold course.

2. Lateral Steering Overshoot EnhancementsOperators sent reports of "S-turns" that were controlled by the Lateral Navigation (LNAV) without pilot input. This occurs at airspeeds of less than 200 knots groundspeed when trying to lock on and hold the lateral path. Changes to the LNAV control laws in FMC U10.7 will make it more stable at low speeds. The output in U10.7 for LNAV roll command makes better changes between path segments.

3. UNABLE REQD NAV PERF-RNP Message Revision
FMC U10.7 includes two changes to the UNABLE REQD NAV PERF-RNP message. First, the message will be a caution level for all flight phases. As a result, the UNABLE REQD NAV PERF-RNP message will show on the Navigation Display (ND) when the Actual Navigation Performance (ANP) is more than the RNP.Second, FMC version U10.7 changes the default RNP alert times. FMC U10.7 also lets the OPC software make changes to the RNP alert times.

4. Vertical Deviation Displayed in all Descent Phases
Before FMC U10.7, the vertical deviation (VDEV) was not shown in the descent modes if the airplane was upstream of the calculated top of descent waypoint. With U10.7, the Path Pointer for Vertical Navigation (VNAV) and Deviation Scale on the ND are shown in all descent phases and at the start of the descent modes.

5. Revised Lateral ANP Calculation
Before FMC version U10.7, the left FMC and the right FMC could give different ANP values. This was caused when the two FMCs start to calculate the ANP at different times with different position data. Operators have sent reports that landings were aborted in low RNP approaches because of the ANP differences. In FMC U10.7, the two FMC's will continue to calculate values independently for ANP. The two FMCs will compare their calculated ANP values and the larger value will show on the display.

6. Revised Vertical ANP Calculation
The vertical ANP that was calculated in FMC U10.6 with data that could have been too conservative. Some in-service vertical RNP alerts could have been the result of how vertical ANP was calculated. With FMC U10.7, the ANP is calculated with Mach to get a more accurate ANP. Analysis shows that the result of the new formula to calculate ANP is that vertical RNP alerts for operations at vertical RNP of 200 feet or less have gone down.

7. Waypoint Speed Constraint Enhancements
The FMC versions through U10.6 showed speed limits on the LEGS page as "AT or BELOW". The Air Traffic Control (ATC) gives a speed and the airplane must keep that speed. The FMC could only make sure that the airplane did not go more than that speed. VNAV holds the applicable speed for the vertical path and makes sure that it is not more than the limit set for the route. The flight crew had two alternatives to hold the speed (with the autothrottle on). It could use Speed Intervention, if that optional feature was enabled, or disconnect the autothrottle and keep the speed manually. FMC U10.7 lets a flight crew record a waypoint speed limit as "AT" (with no suffix), "AT-or-BELOW" ("B" suffix), or "AT-or-ABOVE" ("A" suffix). An "AT" speed limit is important to VNAV operations. It is most important in the terminal area. This feature will decrease the number of times that flight crews go above the ATC speed limits. Navigation Data Bases (NDB) do not give the "AT", "AT-or-BELOW", or "AT-or-ABOVE" qualifier for waypoint speed limits. When these qualifiers are included in the NDB, FMC U10.7 will use the waypoint speed limit. When the qualifier is not specified, FMC U10.7 will see the waypoint speed limit as an "AT" limit.