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From another question asks about the possibility of dropping bombs from converted airliners. My question: is it possible to safely fly aircraft with a door open for the whole flight envelope? Would the aerodynamics be affected if we did not close the door?

I am not asking about the need of oxygen for the crew, just about the aerodynamics involved. I know the plane would not be pressurized.

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  • $\begingroup$ vasin, I changed the title to specify "an airliner," since that's what your question body and tags say. In this question, the answers differ quite a bit between those cases (it's completely a non-incident to open the door of the PA-28 I fly in flight, for example, and my instructor did so multiple times.) If you're interested in non-airliners, too, feel free to edit it back or ask another question. $\endgroup$ – reirab Jun 15 '15 at 21:46
  • $\begingroup$ It will add some drag, for sure, but C-130's regularly fly with their back doors open which you see in any movie where material or parachuters are jumping out the back. chivethebrigade.files.wordpress.com/2013/02/… $\endgroup$ – Dave Kanter Jun 16 '15 at 17:22
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    $\begingroup$ Flying with the rear door open isn't limited to military airlifters -- Skydive Perris has a DC-9-21 that had its rear airstairs removed and uses it for skydiving operations, taking folks up to 13,000' for a real D.B. Cooper experience. $\endgroup$ – UnrecognizedFallingObject Jun 17 '15 at 2:05
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The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a modified 747 that has an 5.5 m x 4.1 m door that is opened during flight for the installed in infrared telescope. But the door is usually closed during takeoff and landing.

But according to this story there are emergency procedures to land with an open door and it had to do so once, when it became stuck half open.

enter image description here enter image description here Images courtesy Wikipedia

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    $\begingroup$ Is the door closed at takeoff and landing out of aerodynamic concerns, or just to protect the equipment from bird strikes and foreign objects on the runway? $\endgroup$ – Jeffrey Bosboom Jun 16 '15 at 2:56
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    $\begingroup$ @JeffreyBosboom: There are other concerns as well for closing the door. For instance, IR telescopes must run very cool, so closing the door allows the team to cool the telescope cooler than ambient before take off, and additionally to flood the "trunk" with nitrogen to prevent condensation when returning to a higher-temperature environment on landing. $\endgroup$ – dotancohen Jun 16 '15 at 7:42
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    $\begingroup$ This seems to me the only "correct" answer, as it's the only one assuming a modern airliner opening a door in a way that the engineers considered "safe". Having survived structural damage (which other answers point at) doesn't equal "safe operation" the way I understood the question. Nice find! $\endgroup$ – DevSolar Jun 16 '15 at 11:44
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    $\begingroup$ @DevSolar I'd assume that this section of this aircraft is not within the pressure vessel, though (since the crew probably wants to breathe while it's open,) so it's quite different from opening a door in flight in a normal airliner. $\endgroup$ – reirab Jun 17 '15 at 17:55
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    $\begingroup$ @DevSolar I modified my answer to mention an actual (non-modified) airliner that did fly with a door open without any structural damage involved. $\endgroup$ – reirab Jun 17 '15 at 18:06
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Aloha Airlines Flight 243 proved that it's possible for a plane to fly with about 25% of its roof missing. The door, however, appears to have remained closed until landing.

https://upload.wikimedia.org/wikipedia/commons/1/1e/Aloha_Airlines_Flight_243_fuselage.pngImage courtesy Wikipedia

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    $\begingroup$ This does indeed imply that a door missing might also be survivable. $\endgroup$ – ArtOfCode Jun 15 '15 at 16:57
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    $\begingroup$ Virtually no one considers "survivable" to be "safe". $\endgroup$ – RBarryYoung Jun 15 '15 at 21:40
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    $\begingroup$ @FreeMan Of course I don't consider "safe" to mean "survivable"! That would be a ludicrous definition of "safe". If somebody says to you, "Have a safe flight!" do you think they mean "Have a flight where the roof blows off the aircraft, one of the flight attendants falls 24,000ft into the ocean, eight other people are seriously injured, almost everyone else receives minor injuries and the plane is written off?" I don't. I guess I expect more of an airline than you do. $\endgroup$ – David Richerby Jun 16 '15 at 7:51
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    $\begingroup$ @DavidRicherby the aircraft flew safely. The fatality happened due to the roof breaking open during flight in an uncontrolled manner, not due to there being no roof. $\endgroup$ – jwenting Jun 16 '15 at 8:32
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    $\begingroup$ @DavidRicherby Sorry but you reminded me of this... youtu.be/WcU4t6zRAKg $\endgroup$ – Basic Jun 16 '15 at 22:10
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Check out my answer here to a similar question (about what would happen if you open a door in flight). In short it depends largely on the plane but in the most general way of looking at it. You could do it up until you would need to pressurize the plane (or you would have wear O2 masks or something to be able to breathe).

UA Flight 811 was able to make a safe decent and return to airport after its door blew out so large planes are maneuverable with out door. enter image description here

Planes like the DC-3 used in WWII for paratrooping regularly ran with their doors open. enter image description here

If you consider rear cargo ramps doors, the C-130 can open its rear ramp for HALO jumping at high altitudes.

In typical HALO/HAHO insertions the troops jump from altitudes between 15,000 feet (4,600 m) and 35,000 feet (11,000 m)

enter image description here

There is at least one other powered glider I can think of that can open its doors mid flight... enter image description here

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    $\begingroup$ Agreed however there are other cases involving pressurized planes mentioned here that should not be over looked. $\endgroup$ – Dave Jun 16 '15 at 13:13
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    $\begingroup$ Your last picture (Spaceshuttle) may very well be taken outside the atmosphere. In my opinion, it has nothing to do with the question unless you provide an example of a Spaceshuttle opening it's doors during atmospheric flight. $\endgroup$ – Mast Jun 17 '15 at 10:55
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    $\begingroup$ @Mast - I think that last picture was meant with tongue firmly in cheek. I thought it was funny, at least. $\endgroup$ – Floris Jun 17 '15 at 14:36
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    $\begingroup$ @Mast, Floris is correct it was meant to add some humor, the rest of my answer is on topic and through enough. $\endgroup$ – Dave Jun 17 '15 at 14:44
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    $\begingroup$ @Dave, interesting that it doesn't seem to require a multi-engine rating. $\endgroup$ – FreeMan Jun 18 '15 at 15:34
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Since comments mentioned that not all of the outcomes from Aloha 243 were exactly safe, here's another example that actually was quite safe:

Southwest 812

Southwest 812 had a large hole open in the roof during flight at cruise altitude, resulting in rapid depressurization at 34,000 ft. 2 of the 123 people on board (a flight attendant and a passenger) suffered minor injuries. The plane diverted to Yuma, Arizona and landed safely about 26 minutes after the depressurization. As with the other cases, the doors were technically shut, but I'm not so sure that that made much difference.

Furthermore, this was not the first time this had happened. Less than 2 years before this incident, Southwest 2294 had a similar incident (though with a smaller hole) and safely diverted to Charleston, WV with no injuries at all.

What's more: according to the FAA's registry and airfleets.net, it looks like both of these aircraft were returned to service and are still actively flying for Southwest! So, it looks like both the "you can walk away from it" requirement and the "the aircraft is reusable" preference were met in both instances.


The Boeing 727

Another case that actually doesn't involve any structural damage at all is the 727 and its airstair. In the famous case of D.B. Cooper's hijacking, this occurred while the aircraft was pressurized. According to the wiki on the incident, the result was the following:

The crew soon noticed a subjective change of air pressure, indicating that the aft door was open.

At approximately 8:13 pm the aircraft's tail section sustained a sudden upward movement, significant enough to require trimming to bring the plane back to level flight.[33] At approximately 10:15 pm Scott and Rataczak landed the 727, with the aft airstair still deployed, at Reno Airport.

Additionally, some skydiving clubs even offered dives from the 727 for many years, though these presumably didn't pressurize the cabin. I'm not sure whether this is still offered.

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  • $\begingroup$ Well done! I just went with the one I knew of. $\endgroup$ – FreeMan Jun 16 '15 at 12:52
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Convair 880 with cargo door open.

Yes they can, here's a Convair 880 with cargo door open.

DC-8 with Door open

DC-8 with cargo door open.

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For the whole flight envelope, maybe not. Depends on the door design. Gear doors frequently have speed limits before they fly off on their own. Large openings create substantial drag, so we may find that the envelope is self-limiting: the aircraft can no longer reach speeds and/or altitudes where the opening is a big problem.

There are too many variables for a simple answer.

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  • $\begingroup$ gear doors have speed limits because they extend into the airflow during flight. The cabin doors would rotate inward, keeping them out of the high speed air flowing past the outside. It would probably get rather noisy... A greater concern I have is maintaining structural integrity for long periods on an aircraft that has a cabin designed to be used while pressurised. This would mean the aircraft can only operate at low pressure altitude with the door open. $\endgroup$ – jwenting Jun 16 '15 at 8:34
  • $\begingroup$ @jwenting Why would being unpressurized affect the structural integrity of the aircraft? Wouldn't the aircraft actually experience much less stress in the case of being unpressurized (until it crashed due to unconscious pilots, at least?) There have been quite a few instances of pressurized aircraft becoming depressurized and continuing at cruise flight levels (due to incapacitated pilots) and I don't recall any structural problems in any of them, prior to the aircraft running out of fuel and flying into terrain. The occupants may experience lots of stress, but the airframe shouldn't. $\endgroup$ – reirab Jul 8 '15 at 18:45
  • $\begingroup$ @reirab It's not the lack of pressurisation I'm concerned with, it's the dynamic stresses on things like the door frames from the turbulent airflow that would result from the doors being open during flight. They're not designed to handle those stresses in most aircraft. $\endgroup$ – jwenting Jul 9 '15 at 5:38
  • $\begingroup$ @jwenting: Or, potentially, the dynamic stresses from the process of depressurisation. $\endgroup$ – Sean May 5 '18 at 17:58
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Biplanes and ultra-lights don't have any doors at all. In general, for any plane the wing, the empennage and, to a lesser extent, the surface area on the lower part of the fuselage is all that is important. If you installed structure-reinforcing crossbars you could remove the entire fuselage wall of a commercial jet and it would still fly.

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  • $\begingroup$ [Citation needed]. A reinforced airliner with the fuselage wall removed would have a lot of drag. And how much of the fuselage wall is needed for strength? (Admittedly, I assume there'll be no cargo or passengers so you could afford to weaken the structure somewhat.) $\endgroup$ – David Richerby Jun 17 '15 at 21:27
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    $\begingroup$ @DavidRicherby Note that I specifically said "structure-reinforcing crossbars" would be needed. He just asked if it would fly, not if it would fly well. $\endgroup$ – Tyler Durden Jun 17 '15 at 21:31
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    $\begingroup$ Also note that the question specified "airliner". Not too many ultra-light airliners that I'm aware of, though I may be wrong. $\endgroup$ – FreeMan Jun 22 '15 at 15:47
  • $\begingroup$ 3 seats is the most I can find in anything that qualifies as an ultralight. $\endgroup$ – Camille Goudeseune Oct 24 at 21:19

protected by Farhan Jun 17 '15 at 16:41

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