View Full Version : B737-300. Should the Lights Test switch also check the Fire handle red lights
sheppey
5th Jul 2012, 11:53
Subject: "Lights Test switch" in the 737-300. Should the Light Test Switch also test the fire warning switches red lights? In one simulator not only does the fire warning switches light up when Lights test switch operated yet the red master fire warning light on the MCP panel does not light up at the same time.
The normal Fault/Inoperative and Overheat (OVHT)/FIRE TEST operates normally giving, among other indications, red lights in the fire switches as well as master Fire warning red light on as part of the test But the Lights Test switch also checks the red lights in the Fire switches. Is the simulator faulty?
porch monkey
6th Jul 2012, 03:22
What does the real aeroplane do? There you have your answer.......
Winston
7th Jul 2012, 15:32
Light test won't illuminate the fire warning switches
grounded27
8th Jul 2012, 04:12
In my experience most modern jet light test's do not illuminate fire warning. It is for a simple reason, you need to do a confidence check on the fire warning system. It is a safe practice.
Potsie Weber
15th Jul 2012, 16:13
737-400. The light test DOES illuminate the fire warning switches. At least it did today!
Easy Street
15th Jul 2012, 20:37
In my experience most modern jet light test's do not illuminate fire warning. It is for a simple reason, you need to do a confidence check on the fire warning system. It is a safe practice.
A good design feature incorporated in a couple of different aircraft I've flown is having 2 lamp test buttons - one that simply illuminates every single lamp, allowing a check of filament serviceability, and another that performs a group check of all the warning circuits by applying simulated failure conditions to light each lamp (including firewire tests). Any warnings that can not be simulated simply have their lamp illuminated. The result should be a 'full house' of lights on each test and this makes for a very quick and simple check!
I've not flown any big jets - do these have a similar kind of dual-test setup?
737-400. The light test DOES illuminate the fire warning switches. At least it did today!
Perhaps there are variations, hence the confusion.
Looking at a particular airline's wiring schematics for the 737NG fire handles, I see no Master Dim/Test test signal going to the red lights in the handles. There is only a DIM/BRT input. This is the same for the glareshield FIRE WARN lights.
However, annunciator lights for things like OVERHEAT and FAULT do receive a light test input from the MD&T system.
Rgds
NSEU
A37575
16th Jul 2012, 14:10
It is an operator option. Some elect to have the Lights Test wired into the Fire switches. Others don't.
RAT 5
16th Jul 2012, 16:51
"It is an operator option. Some elect to have the Lights Test wired into the Fire switches. Others don't."
And how daft is that? If the basic design has been thought through properly, and certificated as such, then when you buy a B737 why don't you get a B737? To allow such trivial tinkering of these, and many other items, is to start the holes lining up.