Da-40 student and instructor reported rear door separated from aircraft during climb out.

Narrative:

During the aircraft pre-flight; it was noted that the door closure annunciation system was tagged as inoperative. The aircraft was still airworthy per maintenance. The inop had been labeled in a conspicuous spot and was noticed. The issue was also documented in the flight binder with the maintenance records. The pre-flight was unremarkable; doors were secured in position I; down and locked. No abnormalities noted while taxiing to runway xxl. No incidents in which the door may have opened. Prior to departure; the rear door was again checked and found to be in the closed position. The latch handle was flush against the door panel in the closed position. A soft-field takeoff was performed at the request of the instructor. At approximately 900' AGL; the instructor heard an abnormal sound coming from the rear canopy. He turned around to diagnosis the issue and discovered the door appeared to be still in the latched position; however; the door was cracked open. I continued to fly the aircraft while he determined what to do. At approximately 1;000' AGL the door separated from the aircraft. The controls were not affected; however; it became difficult to hear radio communications due to the wind noise in the cockpit. I reported the issue to the tower. The instructor took control of the aircraft. On review; the rear door was missing; the tail appeared to be intact and the airplane was flying well. ATC approved us for an emergency landing on xyl. The aircraft was turned; flaps to landing and a successful landing was made on xyl. Arff (airport rescue and firefighting) arrived and advised the aircraft looked okay to taxi and were actively searching for the missing door. The door was found near xxl and in one piece. It had sheared from the door pins at the carbon fiber hinges. The door latch was covered in mud from contact with the ground and in the open position. Aircraft was taxied to the ramp successfully and the issue was reported to school staff.

Original NASA ASRS Text

Title: DA-40 student and Instructor reported rear door separated from aircraft during climb out.

Narrative: During the aircraft pre-flight; it was noted that the door closure annunciation system was tagged as inoperative. The aircraft was still airworthy per maintenance. The inop had been labeled in a conspicuous spot and was noticed. The issue was also documented in the flight binder with the maintenance records. The pre-flight was unremarkable; doors were secured in position I; down and locked. No abnormalities noted while taxiing to runway XXL. No incidents in which the door may have opened. Prior to departure; the rear door was again checked and found to be in the closed position. The latch handle was flush against the door panel in the closed position. A soft-field takeoff was performed at the request of the instructor. At approximately 900' AGL; the instructor heard an abnormal sound coming from the rear canopy. He turned around to diagnosis the issue and discovered the door appeared to be still in the latched position; however; the door was cracked open. I continued to fly the aircraft while he determined what to do. At approximately 1;000' AGL the door separated from the aircraft. The controls were not affected; however; it became difficult to hear radio communications due to the wind noise in the cockpit. I reported the issue to the tower. The instructor took control of the aircraft. On review; the rear door was missing; the tail appeared to be intact and the airplane was flying well. ATC approved us for an emergency landing on XYL. The aircraft was turned; flaps to landing and a successful landing was made on XYL. ARFF (Airport Rescue and Firefighting) arrived and advised the aircraft looked okay to taxi and were actively searching for the missing door. The door was found near XXL and in one piece. It had sheared from the door pins at the carbon fiber hinges. The door latch was covered in mud from contact with the ground and in the open position. Aircraft was taxied to the ramp successfully and the issue was reported to school staff.

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	1632272
Time
Date	201904
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	DA40 Diamond Star
Operating Under FAR Part	Part 91
Flight Phase	Initial Climb
Route In Use	Vectors
Flight Plan	VFR
Component
Aircraft Component	Exterior Pax/Crew Door
Person 1
Function	Trainee
Qualification	Flight Crew Student
Experience	Flight Crew Last 90 Days 42 Flight Crew Total 55 Flight Crew Type 55
Person 2
Function	Instructor
Qualification	Flight Crew Flight Instructor Flight Crew Multiengine Flight Crew Instrument Flight Crew Commercial
Experience	Flight Crew Last 90 Days 250 Flight Crew Total 1100 Flight Crew Type 450
Events
Anomaly	Aircraft Equipment Problem Critical Inflight Event / Encounter Other / Unknown