10
$\begingroup$

I forgot the model of that plane but I believe it's a 737.

I labeled each element for clarity.

What are they?

Click here for high-res.

enter image description here

$\endgroup$
24
$\begingroup$

Main outflow valve door

enter image description here
(Source)

A valve used for controlling the pressure in the cabin. Air is pushed into the cabin by the air conditioning packs, and exits by this hole. The flow can be adjusted using a valve which is located behind this door.

enter image description here
(Source)

The valve opening is controlled by the pressure controller when the automatic mode is selected, and by the crew when the manual mode is selected.

The design of the door includes teeth to decrease the aerodynamic noise, by better mixing air from the cabin and air ram air.

For more details about the air system, see this answer.


Safety pressure relief valve

enter image description here
(Source)

This is one of the two safety valve used in case the main valve mechanism is jammed or ineffective. It's like a safety pressure relief in a pressure-cooker.

It limits the pressure within the cabin below a maximum value, to prevent pressure to damage the cabin vessel and/or create discomfort for the passengers.


Drains

enter image description here
(Source: Question)

Unknown function drains. I believe they are used to evacuate flammable fluids leaking from the APU.


Tail-strike assembly:

enter image description here
(Source)

This tail-skid is used to limit the contact between the aft section of the fuselage and the runway. It absorbs some of the tail strike force. While I'm not sure for the B737, on other models (B757, B777) the tail-strike assembly contains a sensor to alert the crew of the strike occurrence, by displaying a message on the EICAS (thanks to @RalphJ for questioning).

enter image description here
(Source)

The intensity of tail strike force is registered by the color indicator. A force higher than the maximum permissible hides the green strip and requires a maintenance check before the next take-off.

This strip is checked during the pre-flight inspection (walk-around) to prevent flying with a possibly damaged aircraft.


APU drain mast.

enter image description here
(Source: Question)

Drains oil from the forward accessory and the compressor bearing of the APU.


Aft drain mast.

enter image description here
(Source: Question)

Heated drain mast, part of the water system, and used to evacuate water and waste from the aft galley and the lavatory wash basins ("gray water"). Schematics of the B737 NG water system:

enter image description here
(Source: B737 NG General Familiarization)

$\endgroup$
  • $\begingroup$ @RalphJ: I've no document for the B737 tailskid, but this page explains how it works for the B757. I assumed, maybe too quickly, the B737 could be retrofitted. Reading this Boeing publication, I see no mention of the sensor for the B737, so I'll update my post. $\endgroup$ – mins Jun 26 '16 at 15:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.