Flight Management System (FMS) Vertical Path Angle (VPA) recommended default value

Effectivity: Global aircraft equipped with Collins Aerospace Fusion Avionics Suite 

ATA: 34-60 

By: Maxime Boyer-Beaucage, Technical Services 

During the design development of Global aircraft, it was been determined that any Vertical Path Angle (VPA) greater than 2.5 degrees during enroute descent will likely require flight spoiler deployment to reduce speed during initial descent from very high altitude, and then also during the transition to 250 KIAS below 10,000 feet.

As stated in the Flight Crew Operating Manual (FCOM) Volume 1 ROPAT (Recommended Operational Procedures and Techniques) section, the FMS default VPA value should be set to 2.5 during programming of the FMS DEFAULTS pages (see Figure 1). This default value will be shown on the FMS VNAV-THRST page, DES tab (see Figure 2), and will be applied on the entire descent portion of a flight plan.

However, when performing an IMAA-6000 software set loading via avionics software update Service Bulletin (SB) or using Aircraft Maintenance Manual (AMM)/Aircraft Maintenance Publication (AMP) data loading task, the FMS VPA default value resets to the Collins Aerospace factory value of 3.0. The same applies when loading the FMS Performance (PERF) database (DB) file.

Therefore, as specified in the AMM/AMP or when performing an avionics software update SB, it requires re-entry of the Bombardier recommended 2.5 value.

Note that all FMS default values are also reset to the Collins Aerospace factory preset values when the IMAA-6000 software set and/or the FMS PERF DB is loaded. Operators should review and change the values of the default FMS value to their own operating requirements at the same time as the VPA if they are different from Collins’ preset value.

Nevertheless, it has been reported that some aircraft were delivered with a VPA default value set to 3.0 from initial loading of latest avionics software version on the production line. Per the FCOMs or AMM/AMP, flight or maintenance crew shall review and change any FMS VPA default value not showing the Bombardier recommended value of 2.5.

Bombardier has reviewed and modified its internal procedure to avoid any future VPA value adjustment omission.