Emb-175 flight crew failed to secure and lock cockpit door prior to takeoff.

Attributes
ACN	1694988
Time
Date	201910
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	EMB ERJ 170/175 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Cockpit Door
Person 1
Function	First Officer
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Captain
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Security Deviation - Procedural Published Material / Policy

Narrative:

Cockpit door came open on takeoff. At ZZZ the captain and I; first officer; conducted the 'engine ground pneumatic start with jet bridge attached' checklist. Aircraft had two major mels of screen number 4 and the APU unavailable. As conducting the checklist; which is on two different pages in the fom; switching from the first to the second page is right after the engine number 2 has been completely started. The captain advised the flight attendants to secure and arm the doors that were not already armed per the checklist. The flight deck door closed and continued the checklist. Not having screen number 4 I looked at screen number 2 on the captain's side and check that indeed all doors were closed.leading up factors were that we arrived at ZZZ with a proposed flight to ZZZ1. That flight was delayed for a late incoming flight from ZZZ1. Not having my mfd screen operating. My first time completing this checklist in the actual plane.I recognize these threats can create errors and will manage them better in the future. Taking our time to complete checklists and it never hurts to reread through a checklist once completed if not as familiar with it.

Original NASA ASRS Text

Title: EMB-175 flight crew failed to secure and lock cockpit door prior to takeoff.

Narrative: Cockpit door came open on takeoff. At ZZZ the Captain and I; First Officer; conducted the 'Engine Ground Pneumatic Start with Jet Bridge Attached' checklist. Aircraft had two major MELs of screen Number 4 and the APU unavailable. As conducting the checklist; which is on two different pages in the FOM; switching from the first to the second page is right after the Engine Number 2 has been completely started. The Captain advised the flight attendants to secure and arm the doors that were not already armed per the checklist. The flight deck door closed and continued the checklist. Not having screen Number 4 I looked at screen Number 2 on the Captain's side and check that indeed all doors were closed.Leading up factors were that we arrived at ZZZ with a proposed flight to ZZZ1. That flight was delayed for a late incoming flight from ZZZ1. Not having my MFD screen operating. My first time completing this checklist in the actual plane.I recognize these threats can create errors and will manage them better in the future. Taking our time to complete checklists and it never hurts to reread through a checklist once completed if not as familiar with it.

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.