Back to home pageAircraft General

Home > Aircraft Systems > Aircraft General

Contents

Illustrated technical information covering Vol 2 Over 800 multi-choice systems questions Study notes and technical information Close up photos of internal and external components A compilation of links to major 737 news stories with a downloadable archive Illustrated history and description of all variants of 737 Detailed tech specs of every series of 737 Databases and reports of all the major 737 accidents & incidents General flightdeck views of each generation of 737's Description & news reports of Advanced Blended Winglets Press reports of orders and deliveries A collection of my favourite photographs that I have taken of or from the 737 Details about 737 production methods A compilation of links to other sites with useful 737 content Get the book of the website A quick concise overview of the pages on this site

Contents

See more details about the book

All of the information, photographs & schematics from this website and much more is now available in a 360 page printed book or in electronic format.

*** Updated 15 Oct 2014 ***

Visit the 737 Tech Site on Facebook

Lights

From L to R along the panel:

O/B Landing: (Not NG) Three position switch Off - Extend (off) - On. These are located on the outboard flap faring

Retractable Landing: (NG only) Replaces the outboard landing lights on the earlier series. These are located on the fuselage just beneath the ram air intakes. The word is that they may be being moved back to their original position on the flap track faring due to excessive stone damage.

Note Use of both of these lights should be avoided at speeds above 250kts due to excessive air loads on their hinges.

Retractable landing light - NG

I/B Landing: Known as fixed landing lights on the NG. Are located in the wing roots, usually used for all day and night landings for conspicuity.

R/W Turnoff: Also in the wing roots, normally only used at night on poorly lit runways.

Taxi: This 250W light is located on the nose gear, on later models it will switch off automatically with gear retraction. It is common practice to have this on whilst the aircraft is in motion as a warning to other aircraft and vehicles.

Logo: Are on each wingtip or horizontal stabiliser and illuminate the fin. Apart from the advertising value on the ground, they are often used for conspicuity in busy airspace.

Position: Depending upon customer option this can be a three position switch (as illustrated) to combine the strobe. Strobe & Steady / Off / Steady, where steady denotes the red, green & white navigation lights. The three Nav lights are no-go items at night.

Strobe: (Not illustrated) Off / Auto / On. Auto is activated by a squat switch. They are also in the wing tips and are very brilliant. This gives rise to great debate amongst pilots about when exactly they should be switched on as they can dazzle other pilots nearby. many people choose to put them on as they enter an active runway for conspicuity against landing traffic.

Anti-Collision: Are the orange rotating beacons above and below the fuselage. They are universally used as a signal that the engines are running or are about to be started. They are typically not switched off until N1 has reduced to below 3.5% (or N2 below 20%) when it is considered safe for ground personnel to approach the aircraft.

Wing: These are mounted in the fuselage and shine down the leading edge of the wing for ice or damage inspection at night.

Wheel Well: Illuminates the main and nose wheel wells. Normally only used during the turnaround at night for the pre-flight inspection but must also be on to see through the gear downlock viewers at night, hence they are a no-go item at night in all but the NG's. There is also a switch for the main wheel well light in the port wheel well.

 

Water System

There is a 30 US Gal tank (40 US Gal 400 series) behind the aft cargo hold for potable water. This serves the galleys and washbasins, but not the toilets as they use chemicals. Waste water is either drained into the toilet tanks or expelled through heated drain masts.

The tank indicator (-3/4/500 version shown left) is located over the rear service door. Press to test, indications are clockwise from 7 O'clock: Empty, 1/4, 1/2, 3/4, Full. The NG has an LED panel that is always lit (below) for both potable water and waste tank.

Potable Water Quantity Indicator - NG

Potable Water Quantity Indicator - Classics

Airstairs

Forward Airstairs

May be operated from either internal or external panels. The internal panel requires the forward entry door to be at least partially open. Both panels have normal and standby systems. Normal requires AC and DC power, standby only requires DC. External standby system power comes from the battery bus and so does not require the battery switch to be on.

On classics, if the airstairs will not operate, check the striker pin (see photo below) at the bottom left of the door frame. Move it about and ensure it is vertical, this will often cure the problem. They have a tendency to freeze in position on long flights were the doors have got wet.

Caution: The handrails must be stowed before retraction. The use of standby system from either panel will bypass the handrail and lower-ladder safety circuits. Note that the NG has an red covered EMERG switch underneath the airstairs for emergency retraction, this also bypasses any safety circuits.

Maximum wind speed for airstair operation: 40kts.

Maximum wind speed for airstair extended: 60kts.

Airstairs should not be operated more frequently than 3 consecutive cycles of normal system operation within a 20 minute period.

Note that there have been at least 4 cases of children falling through the gaps in the rails of the airstairs FAA SAIB refers.

 

Aft Airstairs

In the drive for self sufficiency, these were fitted to about 120 737-200's. They were much more complicated than forward airstairs as they folded in two places and took the door downwards with them. If you have ever considered the forward airstairs to be temperamental then you would not get on with aft airstairs.

There were several reports of inadvertent deployment and even two instances of them extending after take-off. Boeing say that after one of the in-flight deployments the crew landed with little control problem and apart from some scuff marks on the foot plates where they made contact with the runway, they were still in working order after the event!

              

737-3/4/500 Door showing latch fitting (above), striker pin (below) and 3 stop pin fittings

 

 

 

 

 

 

 

 

 

 

 

Underneath NG Airstairs - Notice the red guarded MAINT switch.

 

Doors

Amber light will illuminate with Master Caution "DOORS" when a door is unlocked. Air Stair must be fully stowed, even if fwd entry door is closed. Equip is for E & E bay and Radar bay.

The sequence of door lights is changed in the NG's to accommodate the left and right overwing annunciators. They are located between the fwd & aft entry/service door lights.

On the NG, it is not uncommon to get an overwing caption illuminate for a fraction of a second as you start the take-off run. This is due to the overwing exit automatic locking function being slightly slow.

Maximum wind speed for door operation: 40kts.

The doors may remain latched open in winds of up to: 65Kts.

(AMM 52-10-00-011 Rev 0 09)

200C door panel

Classic door panel

NG door panel  

Nose, wing tip & tail clearance

The following table shows the increased radius of turn of the wing and tail relative to the nose during a turn with full nose wheel steering applied. This table shows that turning in a 737-600 is probably most hazardous because the wings and tail turn out much further than the nose.

 

Radius of turn (ft)

Series

Nose

Wing

Tail

-300

55

+5

+ 9

-400

61

+1

+ 7

-500

50

+9

+10

-600

51

+17

+11

-700

56

+13

+10

-800

66

+6

+9

-900

71

+2

+7

 

 

Cargo Holds

Both cargo holds are designed to confine a fire without endangering the safety of the aircraft. A cargo fire detection and extinguishing system may be fitted as an option (see Fire Protection). NB If a hold ceiling light lens cover is broken or missing this is a fire hazard and the bulb should be removed if the cover can not be fixed.

Cargo-Compartment Class
Model Lower cargo compartment Main cargo compartment
737-100/-200/-300/-400/-500 (line no. 1-3078 Class D Not required
737-300/-400/-500 (line no. 3079 and higher) Class C Not required
737-600/-700/-800 (line no. 1-90) Class D Not required
737-600/-700/-800 (line no. 91 and higher) Class C Not required
737-C/QC Class D Class E

Class C: Compartments that contain both the smoke-detection and fire-suppression of a minimum initial concentration of 5 percent Halon throughout the compartment to suppress any combustion to controllable levels. Thereafter, the system must sustain a minimum concentration of 3 percent Halon for 60 min to prevent reignition or spreading of the combustion.

Class D: Compartments that depend on oxygen deprivation to prevent and suppress combustion.

Class E: Compartments that have a smoke-detection system alert the flight crew within 60 sec from the time smoke first appears in the compartment.

The holds are sealed and pressurised but have no fresh air circulation. They have no temperature control but are heated by exhausting cabin air around their walls. The forward hold also has additional heating from E & E bay air. Live cargo can be carried on either cargo compartment but the forward hold is preferred.

The optimum distribution for loading the cargo holds to keep the aircraft in balance is as follows: 

Series

Fwd

Aft

-300/700

1/3

2/3

-400/800

0

All

-500/600

All

0

 

For a technical questionnaire on this subject, click here.

This site has had visitors to date.