Emb-145 first officer reported that a malfunctioning lateral navigation mode caused a course deviati...

Narrative:

Departing [on] RNAV departure. At the positive rate callout I called for gear up; speed; and nav. I was following the flight director through 300-500 when I realized the navigation mode hadn't captured and we were still in heading mode. I disregarded the flight director and turned to the left back to our course. The captain had tried three times throughout the departure to arm the navigation mode to no avail. By the time I noticed the deviation and turned on course we were approximately one dot to the right of our course. I believe we might have penetrated a prohibited area. On the fourth attempt the lateral mode armed and I flew the remainder of the departure without incident. After several minutes we were given a phone number to call. [On arrival] I was being vectored to final for runway xy. I switched to green needles and armed the navigation mode to intercept the localizer with autopilot engaged. The autopilot captured the localizer and almost immediately dropped the lateral navigation mode and reverted to rol mode. The captain tried several times to rearm the approach mode to no avail. I disconnected the autopilot and followed the PAPI to an uneventful landing using raw data.

Original NASA ASRS Text

Title: EMB-145 First Officer reported that a malfunctioning Lateral Navigation mode caused a course deviation on departure and reversion to a raw data; hand-flown approach.

Narrative: Departing [on] RNAV Departure. At the positive rate callout I called for gear up; speed; and nav. I was following the Flight Director through 300-500 when I realized the NAV mode hadn't captured and we were still in heading mode. I disregarded the Flight Director and turned to the left back to our course. The Captain had tried three times throughout the departure to arm the NAV mode to no avail. By the time I noticed the deviation and turned on course we were approximately one dot to the right of our course. I believe we might have penetrated a Prohibited area. On the fourth attempt the lateral mode armed and I flew the remainder of the departure without incident. After several minutes we were given a phone number to call. [On arrival] I was being vectored to final for RWY XY. I switched to green needles and armed the NAV mode to intercept the LOC with autopilot engaged. The autopilot captured the LOC and almost immediately dropped the Lateral NAV mode and reverted to ROL mode. The Captain tried several times to rearm the Approach mode to no avail. I disconnected the autopilot and followed the PAPI to an uneventful landing using raw data.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1476522
Time
Date	201708
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	EMB ERJ 145 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Autoflight System
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Airspace Violation All Types Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types

Emb-145 first officer reported that a malfunctioning lateral navigation mode caused a course deviation on departure and reversion to a raw data; hand-flown approach.