Rear Door departs a DA40 after takeoff

[Kyle]

I've heard the same thing, let the safety latch do it's job and keep the door closed. Pushing the door back down or messing with the handle will likely disengage the safety latch and result in the door opening and departing. Part of my preflight briefing is to instruct passengers not to touch the handle or latch even if the door partially opens.

[Rich]

This incident made the "Wait, Wait, Don't tell me." broadcast today

That 17 or so sounds about right. I see these show up on the FAA Accident and Incident page with some regularity. It seems like a couple per year.

[Karl]

Further to my earlier comment about checking and lubricating the red button, it is also important to check the operation of the latch mechanism.
The latch mechanism has an over-centre lock design utilizing a spring, older versions have a steel spring while newer versions have a gas strut. If the spring is not doing its job the latch can vibrate open in flight.
To check it, open the door a few inches and move the latch lever, it should snap to both the open and closed position and be held there by the spring.
If it is possible to leave the latch lever in any position the the spring is not doing its job and the latch could vibrate open during flight.
A weak or ineffective spring on the latch combined with a sticky red button on the secondary catch could result in loss of the door even if you correctly check it is closed and latched before flight.

[Rich]

Max Prescott put out a podcast where he tries to go into the details of the locking mechanism but overlooks/misstates numerous things,

1. There are two lugs for the passenger door: fore and aft. His podcast would lead you to think there is only the one in front.
2. Doesn't reference the potentially sticking safety release button, which can need attention.
3. Makes no mention of the "Door" annunciator.
4. Doesn't mention checking that the latch clearly goes "over-center" as part of preflight. The gas spring in particular clearly has some reliability issues.

My comments:
"Door" annunciator:
Way in the past the "Door" annunciator was flaky in mine until I replaced and readjusted the actuating arms for it. (In the old design like mine, the switch assembly for both the canopy and passenger door is in the left center post, behind the large rear seat vent control.) Note that on power-up all indicators should light up briefly so you can see that at least the bulb hasn't burned out.

At least occasionally, check that the "Door" light comes on independently whenever either the canopy latch is released.

Preflight:
The preflight checklist in the POH glosses over the rear door inspection. I always double-check that the "child safety latch" button operates correctly. It's also worth working the latch itself to check for that over-center feel. These checks need to be redone after loading anything in the rear, such as passengers or cargo.

An anecdote worth repeating: When we picked up the plane from the factory I mentioned to the sales dude who accompanied us that it seemed like some curious two-year old might undo the rear latch in flight. He actually got kind of huffy and stated he didn't consider it a problem. Obviously this childless guy (his wife was expecting their first child at the time) had a lot to learn. The AMM in part refers to the safety lock as a "Child Safety Lock" (ref DA40 52-10-00 fig. 9 and similar).

[Rich]

Another one - Las Vegas, NV yesterday:
https://www.asias.faa.gov/apex/f?p=100: ... 24,DIAMOND

[Soareyes]

“AIRCRAFT DEPARTED, LEFT DOOR FELL OFF AND RETURNED TO LAND, LAS VEGAS, NV.”

Kind of like the first stage of a Space-X rocket.

[Steve]

“AIRCRAFT DEPARTED, LEFT DOOR FELL OFF AND RETURNED TO LAND, LAS VEGAS, NV.”

Kind of like the first stage of a Space-X rocket.

Maybe we could rig up the rear hatch to act as a Rogallo wing similar to what was proposed for the Gemini spacecraft:

https://airandspace.si.edu/collection-o ... he%20ocean.

In case of an engine failure over inhospitable terrain, you could deploy the rear hatch (retained to the airframe by straps of course), and glide back to land. Facetious, of course...

[dant]

To check it, open the door a few inches and move the latch lever, it should snap to both the open and closed position and be held there by the spring.
If it is possible to leave the latch lever in any position the the spring is not doing its job and the latch could vibrate open during flight.

I performed this check a couple days ago and afaict failed it. The latch more or less could be put to any position.

It's also a bit stiff and squeaky - could it be possible that insufficient lubrication could prevent the gas piston from doing its job?

[Karl]

To check it, open the door a few inches and move the latch lever, it should snap to both the open and closed position and be held there by the spring.
If it is possible to leave the latch lever in any position the the spring is not doing its job and the latch could vibrate open during flight.

I performed this check a couple days ago and afaict failed it. The latch more or less could be put to any position.

It's also a bit stiff and squeaky - could it be possible that insufficient lubrication could prevent the gas piston from doing its job?

It could, but more likely the gas spring.

Try lube it first and see what happens.