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I really like the 737, it is perhaps my favorite airliner. One curiosity of this aircraft (afaik, it is the only commercial airliner) is that the main landing gear has no cover:

enter image description here

Here is another picture from the inside:

enter image description here

In this situation, how does the aircraft protect the gear mechanism from weather/freezing?

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    $\begingroup$ why would an aircraft need to protect the gear from weather/freezing? when the aircraft is parked isn't the gear exposed anyway? how would that be different? $\endgroup$ – Federico Jul 1 '15 at 7:51
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    $\begingroup$ Because the outside temperature when cruising is well below freezing. If ice can form on the wings - can't it form on the exposed area? $\endgroup$ – Burhan Khalid Jul 1 '15 at 7:57
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    $\begingroup$ Wouldn't the open holes cause more drag? $\endgroup$ – RoboKaren Jul 3 '15 at 6:39
  • $\begingroup$ Open holes causes more drag but complexity and weight penalty of gear doors outweigh the drag. $\endgroup$ – vasin1987 Dec 11 '15 at 16:11
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Aircraft icing is not caused by ice in clouds- it is formed by supercooled water droplets (Source). They freeze on impact with a surface that has some location with zero flow velocity, most often on the leading edge of the wing.

Ice accumulates on every exposed frontal surface of the aeroplane – not just on the wings, propeller, and windshield, but also on the antennas, vents, intakes, and cowlings. It builds in flight where no heat or boots can reach it. It can cause antennas to vibrate so severely that they break. In moderate to severe conditions, a light aircraft can become so iced up that continued flight is impossible. The aeroplane may stall at much higher speeds and lower angles of attack than normal. It can roll or pitch uncontrollably, and recovery may be impossible. Source

The gear as such as is not worse off than normal landing gear. The B737 has wheel caps visible in your first photo to cover towards the outside, and is not allowed to fly without them. If icing had been a problem, the same concern would extend onto landing gear doors being frozen shut. Landing gears bays are unpressurised and very cold normally anyways.

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  • $\begingroup$ the wheel caps cover the hub, I guess he is worried about the rubber. $\endgroup$ – Federico Jul 1 '15 at 9:02
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    $\begingroup$ The 737 Configuration Deviation List (CDL) does allow the aircraft to be dispatched without the wheel covers installed. Depending on the aircraft model and exactly what's missing there are performance limit requirements and the antiskid on that wheel may have to be deactivated with those requisite limitations. $\endgroup$ – Sports Racer Jul 1 '15 at 12:43
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Most of the aircrafts have covers (caps) so as to isolate the landing gear from the air around so as to prevent it from icing. Commercial airliners reach altitudes to the proximity of 35000 feet (and maybe more in some cases) and temperatures could drop 80 degrees below zero. In such cases, if the landing gear has caps and is isolated from the free stream, the heat retained in the landing gear bay from the hydraulics and the friction in the tires while takeoff does keep the landing gear warm and hence protect it from icing (source).

Heat from the plane’s hydraulic lines in the wheel well, as well as heat retained in the tires, could have helped the stowaway survive as the aircraft climbed to altitudes with sub-zero temperatures, the FAA reported.

Now, for airplanes like the one shown above, there is a possibility of the landing gear getting iced. When this happens, it might cause a range of problems. Problems ranging from skidding while landing to jammed landing gear. Usually, before landing when an airplane descents, the rise in temperature is good enough to deice the landing gear, but if that does not happen then pilots need to tackle with the icing problem in flight itself. Source

When surface temperatures are low enough for frozen deposits to be present, consider whether the mechanisms might have become frozen during flight as a result of prior extended taxiing through slush or wet snow. Flight above the freezing level for prolonged periods may result in the landing gear becoming frozen in the retracted position. This is less of a problem on most modern commercial transport aircraft, where the gear bays are largely enclosed by doors unless retraction/extension is in progress, but is a relatively common occurrence on aircraft such as the LOCKHEED AC-130 Spectre. If it is suspected that taxiing through slush or wet snow may have led to deposits adhering to the landing gear assemblies, then it may be advisable to cycle the gear after initial post take off retraction to try and shed any deposits.

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    $\begingroup$ There is no way the heat of the tires or hydraulic lines in a wheel well are going to help someone survive in a wheel well. The main reason landing gear has doors is to streamline the airplane and reduce drag. That's it. If it's -80 outside the wheel well, it will very shortly be -80 inside the wheel well. This poor guy was laying against the pneumatic supply ducting, the only really warm spot in a wheel well and it didn't help him one bit. nydailynews.com/news/world/… $\endgroup$ – Sports Racer Jul 10 '15 at 13:59
  • $\begingroup$ I gave the source which claimed that..!! Secondly, the reason caps are there, is because to streamline flow, and to prevent icing of the landing gear (Again please have a look at the source). I did not mention the streamlining of the flow because it was not required to answer the question. p.s. It feels bad when people dont read the complete answers and pass judgements :( $\endgroup$ – Victor Juliet Jul 10 '15 at 14:38
  • $\begingroup$ Your source is from the LA Times quoting someone from the FAA. With 30 years in this industry I can assure you that neither of these sources is reliable. You may however continue to believe what you wish. I hope however that you choose to never try this on your own or you will end up like the stowaway in the DL wheel well. I also don't know where this protection from ice thing comes from but carry on with that delusion as well. $\endgroup$ – Sports Racer Jul 10 '15 at 18:35
  • $\begingroup$ Let's say SFO-NRT is 10+ hrs. How insulate is landing gear door? $\endgroup$ – vasin1987 Aug 8 '15 at 23:56
  • $\begingroup$ Wheel well temperatures even on aircraft with doors get well below freezing in flight. On the 737, the only exposed part of the gear is the tire sidewall and aerodynamic hubcap. $\endgroup$ – OSUZorba Mar 15 at 0:27

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