CL600 flight crew reported a rejected takeoff due to the main entry door opening.

Attributes
ACN	1591953
Time
Date	201810
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	TX
Environment
Light	Dawn
Aircraft 1
Make Model Name	Challenger CL600
Operating Under FAR Part	Part 91
Flight Phase	Takeoff
Flight Plan	IFR
Component
Aircraft Component	Exterior Pax/Crew Door
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 50 Flight Crew Total 14250 Flight Crew Type 1550
Person 2
Function	Pilot Flying Captain
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Flight Engineer Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 49 Flight Crew Total 16000 Flight Crew Type 1250
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

Main entrance door came open on initial takeoff roll at about 60 knots. The door contacted the runway at which time the takeoff was aborted. Raised door; secured it and then taxied off runway and return to [company].the initial inspection of the door revealed there was sheet metal damage to the outer skin at upper end of the air stair door. The foot of the door was broken off as well. The door locking mechanism was checked and found to be working as designed. The initial inspection of the damage to the door didn't rise to the criteria of an accident.the contributing factors to this incident were:1. Flight crew was operating on only a couple of hours sleep after a late arrival that morning. Should have declined to do flight under these circumstances in advance. 2. Had not flown this particular aircraft type for a couple of months and had been operating a 'new' type by another manufacturer. I was distracted when closing the door and did not catch the usual 'door unsecured' indications as we prepared for taxi and takeoff. I believe that there was a mental transfer of 'door unsecured' indications from the new aircraft that I was applying to this model. Mental confusion!3. Complacency from having operated this aircraft for 1500+ hours; closing and successfully securing the door for multiple hundreds of time without incident.this has all led to deserved self-evaluation and awareness that operating under any of the above conditions can easily lead to a mishap of minor significance as this; bent metal; or more serious consequences.

Original NASA ASRS Text

Title: CL600 flight crew reported a rejected takeoff due to the main entry door opening.

Narrative: Main Entrance Door came open on initial takeoff roll at about 60 knots. The door contacted the runway at which time the takeoff was aborted. Raised door; secured it and then taxied off runway and return to [company].The initial inspection of the door revealed there was sheet metal damage to the outer skin at upper end of the air stair door. The foot of the door was broken off as well. The door locking mechanism was checked and found to be working as designed. The initial inspection of the damage to the door didn't rise to the criteria of an accident.The contributing factors to this incident were:1. Flight crew was operating on only a couple of hours sleep after a late arrival that morning. Should have declined to do flight under these circumstances in advance. 2. Had not flown this particular aircraft type for a couple of months and had been operating a 'new' type by another manufacturer. I was distracted when closing the door and did not catch the usual 'door unsecured' indications as we prepared for taxi and takeoff. I believe that there was a mental transfer of 'door unsecured' indications from the new aircraft that I was applying to this model. Mental confusion!3. Complacency from having operated this aircraft for 1500+ hours; closing and successfully securing the door for multiple hundreds of time without incident.This has all led to deserved self-evaluation and awareness that operating under any of the above conditions can easily lead to a mishap of minor significance as this; bent metal; or more serious consequences.

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.