This question is for WW2-era naval aircraft.

I noticed that some cruisers and battleships carried a couple seaplanes, launched by catapult and recovered with cranes.

enter image description here

Obviously these are unprotected by a hangar. So it raises the question, is a hangar really necessary to protect naval aircraft from the weather? Naval aircraft should be more stalwart against seawater at the very least, and I can't imagine that freshwater rain would do anything to even a land-based plane. Dirt and sand also seem a remote possibility. Only thing left I can think of is sunlight over long periods.

The question pertains to seaplanes as well as wheeled aircraft, if they are carrier aircraft. (I understand that carriers have a hangar for maintenance and/or an armored roof, but my question is about the need, or not, for weather protection.) Can naval aircraft just be left on the deck without ill-effects?

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    $\begingroup$ That's a Curtiss SOC Seagull. It had an operational life (first flight to retirement) of 11 years. If the F-35 was treated that badly, they would have all been retired by 2017. $\endgroup$ – Coomie Jul 18 '19 at 6:43
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    $\begingroup$ @Coomie 11 years sure, but that alone does not prove it was due to harsh weather or bad maintenance. This was WW2 when technology was rapidly progressing. Any bi-plane was already obsolete by the time WW2 started anyway. $\endgroup$ – DrZ214 Jul 19 '19 at 21:29
  • $\begingroup$ Aren't the main reasons carriers have hangers a) so that planes don't take out half the ship's air arm if they botch a landing and b) to protect the planes from air attack, with weather being at most a minor consideration? $\endgroup$ – Sean Oct 7 '19 at 2:00

Naval aircraft cannot be just left on deck without maintenance and expected to operate after an extended period of time. I will restrict this to storage on deck and avoid going into operational issues like spray effects on engines as OPs question does not ask that.

There are a multitude of technologies in use to protect metal parts from corrosion, but in the end these all fight a losing battle against entropy and their effectiveness is more accurately measured in how long they can stave off corrosion.

Painted parts are probably the most resistant, as organic coatings provide a hard barrier over the vulnerable surfaces. Paint is not foolproof, however, as it can chip and crack, due to thermal stresses, FOD, etc. Furthermore, not all parts can be painted and corrosion can develop underneath paint if it has an entry point, like a rivet hole , a static discharge connector or a crack in the paint.

Filiform corrosion

Where organic coatings are not suitable, for example on shock absorber struts, other coatings can be applied. For steel a common solution is a chrome layer; for aluminium, chromate conversion and anodizing. These solutions are not as effective as a coat of paint, and an aggressive-enough environment will attack even chrome layers. As an example, take landing gear struts, which have multiple exposed moving parts, many crevices to accumulate moisture and diverse metals ready to form galvanic cells.

Finally, there are places where no coating can be used at all: static dischargers. These do exactly what the name implies, ground the aircraft to allow for built up static charges to flow into the ground, so they need to be exposed and to contact (almost)bare metal on the airframe to ensure conductivity. Their connection points are typically covered in sealant after installation, but these sealants do not last forever: they weather and end up cracking after some years in the field, turning into a moisture trap and destroying the part they are on if not monitored.

Finally, a note on composite airframes. CFRP parts are conductive and very noble, so they can easily corrode whatever metal is attached to them. This can be mitigated with careful engineering, but can come as an unexpected problem for systems suppliers that are used to installing equipment on metal airframes: an aluminium airframe will corrode before a steel tray attached to it without insulation, but the opposite will happen with a composite airframe.

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    $\begingroup$ Can you comment any on the photo then? Were those exposed seaplanes not expected to last longer than a year? 2 years? Or maybe they were supposed to be covered by a tarp? Also, i did not explicitly mention spray effects, but i think that qualifies as weather for a naval aircraft. Maybe you can expound upon that, but if it is too big a topic i will open another q on it. $\endgroup$ – DrZ214 Jul 18 '19 at 18:20
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    $\begingroup$ Naval aircraft on an aircraft carrier are either parked on the flight deck or the hangar bay. Hangar bays have huge side doors that close, but typically they are only closed in foul weather and normally left open. Aircraft in both places are quite exposed to breezes of salty air, which are quite common when the ship is traveling at 20-30 knots. Covering aircraft with tarps is not practical because the aircraft need to be accessed, maintained, and used frequently. $\endgroup$ – rclocher3 Jul 18 '19 at 20:45
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    $\begingroup$ Sorry, I was speaking of modern aircraft carriers. It may have been practical for the seaplanes carried by WWII-era cruisers and battleships to be covered by tarps. $\endgroup$ – rclocher3 Jul 18 '19 at 21:05
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    $\begingroup$ in WW2 planes were initially often carried inside a hangar, fueled and ready to go. After the first few naval battles led to ships being lost due to hangar fires set off by a single shell hitting the hangar and turning those planes into torches, fueled planes were kept outside and/or the hangar doors open in order to make it easier to throw the planes overboard when and if a fight started. And yes, that does decrease the service life of the plane, but planes are a lot cheaper than heavy cruisers and easier to replace as well. $\endgroup$ – jwenting Jul 19 '19 at 3:41
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    $\begingroup$ @DrZ214 I do not have enough knowledge of the operational procedures for interbellum observation planes to comment directly, but a quick search does point to an early retirement for the entire fleet. I'll try to find more, but information about the storage procedures for embarked aviation from 75 years ago is hard to come by. On the issue of spray, for stored airframes it only helps add saltwater to inconvenient places; for operating aircraft it is more troublesome as it can be ingested by the engines, but all naval craft have some design requirement to withstand this. $\endgroup$ – AEhere supports Monica Jul 19 '19 at 10:59

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