Sheltered Air Door or Inlet

BIG, double-deck, four-engine, medium to long range, high altitude, high speed, commercial transport airplane
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kforten
Airman Basic
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Joined: 16 Jun 2014, 15:29

Sheltered Air Door or Inlet

Post by kforten »

Not a pilot. Investigating the crash of Boeing 377 N90944 in November 1957 and wondering if anyone might be able to help. If the "sheltered air door" or inlet is malfunctioning what would the effect be on the aircraft? If the door doesn't close all the way, for example, how might that impact the plane? Thanks,

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Jacques
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Joined: 26 Jun 2011, 17:54
Location: West Coast, USA

Sheltered Air Door or Inlet

Post by Jacques »

The sheltered air doors are a means of managing the air used by the carburetor. Unsheltered air is just that, mainly ram air from the front of the cowling. Engaging sheltered air closes or partially closes off the air coming in through the front of the cowling and draws it in instead through inlets on the bottom side of the cowling. The result is drier air arriving at the carburetor and a reduced risk of carburetor icing. Carburetor icing ( the risk of which is indicated by a lowering of Carb Air Temperature ) would be the primary reason for using sheltered air. If the door were to fail open, the risk of carburetor icing would increase, but that could be mitigated by increasing turbocharged air coming into the carburetor. So, in your instance, the pilot might reduce manifold pressure by drawing back the throttles, then raising the manifold pressure back to the desired figure by adding in more boost.


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kforten
Airman Basic
Posts: 3
Joined: 16 Jun 2014, 15:29

Re: Sheltered Air Door or Inlet

Post by kforten »

Thank you. That is very helpful

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