N1 speed indication awareness

Effectivity: Global aircraft (GX, Global 5000, Global XRS, Global 5000 Global Vision Flight Deck, Global 6000, Global 5500, Global 6500)

ATA 73-21

By: Dominique Lessard – Technical Services 

This article provides details on differences between engine N1 speed indications on Global aircraft equipped with Honeywell avionics and Global aircraft equipped with Collins avionics. When these differences are not understood,  it can lead to unnecessary troubleshooting.

On Global Express, Global 5000, and Global XRS aircraft fitted with the Honeywell avionics , the engine N1 speed is displayed on EICAS in the form of a dial and digital numerical indication.

On Global 6000, Global 5000 GVFD, Global 5500, and Global 6500 aircraft fitted with the Collins avionics, the engine N1 speed is displayed on EICAS only in numerical format, which is a change from the Global aircraft fitted with Honeywell avionics.

In a Honeywell cockpit, the dial gauge display of the engine N1 speed indication permits the display of pointers: the red tick mark represents the N1 limit of 102% RPM, while the amber tick is at 100.5% RPM. See the image below:

The amber tick pointer enhances visual awareness that the aircraft is nearing the maximum N1 speed limit indicated by the red tick mark.

On Global aircraft equipped with the Collins avionics cockpit, the N1 speed indication is provided only in numerical format, as seen in the image below:

With N1 speed displayed in numerical format, visual awareness is enhanced by changing the colour of the N1 speed indication to amber upon reaching 100.5% (for Global 5000 GVFD and Global 6000 aircraft) or 101.5% (for Global 5500 and Global 6500 aircraft):

Similarly, the N1 speed indication will be displayed in red upon reaching 102% (for Global 5000 GVFD and Global 6000 aircraft) or 102.1% (for Global 5500 and Global 6500 aircraft):

The limits of the N1 speed are associated with the engine type installed on the aircraft.

BR700-710A2-20:

BR700-710D5-21:

These tables are available in the FCOM 1 of each aircraft model.

Remember: While operating a Global 5000 GVFD, Global 6000, Global 5500 or Global 6500 aircraft, the purpose of an amber N1 speed indication is only to remind the crew that the N1 speed is close to the limit. No maintenance action is required unless the speed limit is exceeded (N1 in red) and the associated exceedance report is triggered.