Narrative:

At rotation, the door of the small transport popped open to the safety catch. At 400' MSL we entered the clouds requesting an ILS to return and secure the door. At assigned altitude of 2500' on the downwind vector for the ILS, one of the passenger in the rear seat (also on ATP with a great deal of time) reached up in an attempt to close the door. His intent was to pull the door inward in an effort to get the primary latch to catch. I slowed the aircraft to approximately 100 KTS and was preparing to yaw the airplane when the secondary latch released and the door blew open about 4 inches. By the time I had secured my charts and approach plates which were lying on the unoccupied front seat and were being sucked toward the door, reapplied power which had been reduced, 400' of altitude had been lost. The altitude was recovered, the approach completed, door secured and trip continued. Factors leading to the problem include: 1) I had not flown an small transport for a couple of months and one tends to forget the idiosyncrasies of the small transport door latch. 2) since the door was closed by a passenger with much more small transport experience than myself, I incorrectly assumed the door had been properly latched and although I did not intentionally skip any sections of the checklist either this area was overlooked or not enough pressure was applied to the handle when checked. 3) power should have been applied immediately when the door blew open but I found myself reluctant to allow my approach plates to blow out the door in low IFR conditions, especially with the 1600' cushion of altitude I had. Although this was not the first time I have had a door come open on an small transport it will be the last for awhile. The door latch system on the small transport is a weak link in an otherwise very fine aircraft.

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Original NASA ASRS Text

Title: ALT EXCURSION BY SMT DURING A RETURN TO LAND BECAUSE OF AN UNLATCHED COCKPIT DOOR.

Narrative: AT ROTATION, THE DOOR OF THE SMT POPPED OPEN TO THE SAFETY CATCH. AT 400' MSL WE ENTERED THE CLOUDS REQUESTING AN ILS TO RETURN AND SECURE THE DOOR. AT ASSIGNED ALT OF 2500' ON THE DOWNWIND VECTOR FOR THE ILS, ONE OF THE PAX IN THE REAR SEAT (ALSO ON ATP WITH A GREAT DEAL OF TIME) REACHED UP IN AN ATTEMPT TO CLOSE THE DOOR. HIS INTENT WAS TO PULL THE DOOR INWARD IN AN EFFORT TO GET THE PRIMARY LATCH TO CATCH. I SLOWED THE ACFT TO APPROX 100 KTS AND WAS PREPARING TO YAW THE AIRPLANE WHEN THE SECONDARY LATCH RELEASED AND THE DOOR BLEW OPEN ABOUT 4 INCHES. BY THE TIME I HAD SECURED MY CHARTS AND APCH PLATES WHICH WERE LYING ON THE UNOCCUPIED FRONT SEAT AND WERE BEING SUCKED TOWARD THE DOOR, REAPPLIED POWER WHICH HAD BEEN REDUCED, 400' OF ALT HAD BEEN LOST. THE ALT WAS RECOVERED, THE APCH COMPLETED, DOOR SECURED AND TRIP CONTINUED. FACTORS LEADING TO THE PROBLEM INCLUDE: 1) I HAD NOT FLOWN AN SMT FOR A COUPLE OF MONTHS AND ONE TENDS TO FORGET THE IDIOSYNCRASIES OF THE SMT DOOR LATCH. 2) SINCE THE DOOR WAS CLOSED BY A PAX WITH MUCH MORE SMT EXPERIENCE THAN MYSELF, I INCORRECTLY ASSUMED THE DOOR HAD BEEN PROPERLY LATCHED AND ALTHOUGH I DID NOT INTENTIONALLY SKIP ANY SECTIONS OF THE CHECKLIST EITHER THIS AREA WAS OVERLOOKED OR NOT ENOUGH PRESSURE WAS APPLIED TO THE HANDLE WHEN CHECKED. 3) POWER SHOULD HAVE BEEN APPLIED IMMEDIATELY WHEN THE DOOR BLEW OPEN BUT I FOUND MYSELF RELUCTANT TO ALLOW MY APCH PLATES TO BLOW OUT THE DOOR IN LOW IFR CONDITIONS, ESPECIALLY WITH THE 1600' CUSHION OF ALT I HAD. ALTHOUGH THIS WAS NOT THE FIRST TIME I HAVE HAD A DOOR COME OPEN ON AN SMT IT WILL BE THE LAST FOR AWHILE. THE DOOR LATCH SYSTEM ON THE SMT IS A WEAK LINK IN AN OTHERWISE VERY FINE ACFT.

Data retrieved from NASA's ASRS site as of August 2007 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.