Clear high-temp heat shrink....
  
     
  

Most engine fire detection systems come in two forms,  Systron-Donner or Kidde .

CF6-80A and CF6-80C2 that use Systron fire detection systems have three equal resistance loop sensors. Each loop measures 4.5K Ohms. They are wired in a parallel circuit.

In a functional system 1.5K Ohms should be read at the fire detection card pins 19 & 20.
  
     
  
If 2.25K Ohms is read..... you've lost one loop. If 4.5K Ohms is read..... you've lost two.
  
     
  
The "only" way to verify an open loop is to disconnect one (or both) wires from the loop terminals and measure resistance at the terminals (if the wires are connected..... you're reading the other loops and possibly the card).

A loop is either good or bad. There is no halfway. 4.5K Ohms or open.

If a bad loop has been isolated, throwing a decade box across the terminals should at least give you a valid test from the cockpit.
  
     
  
Or..... just throw a 4.5K Ohm resistor across them.
  
     
 

Cockpit Voice Recorders save approximately two hours of cockpit conversations that can be used in conjunction with Flight Data Recorders to ascertain the cause of accidents.

There are four channels of recordings. An area microphone, the capt's audio system, the F/O's audio system, an observers system or the cabin public address system.
  
   Flight data recorder information is usually downloaded at regular intervals with the use of components such as the  WQAR .

There is no need to monitor CVR recordings continuously, but functionality of the units must be checked periodically. Maintenance will perform a CVR download which is used by engineering to verify all recording operations are valid.

Flight Data Systems  has a handheld download device that is used to retrieve the recordings.

Maintenance will pull the recorder.....
  
     
  
Install an adapter and place the unit back in the rack.
  
     
  
An interface cord is connected at the front of the recorder.
  
     
  
From there, it's just following the menu items to start the download operation.
  
  

The image of the switch above shows a switch that the ball and adjustment nut had fallen out of the switch rocker. It was being replaced at the time.

The control yoke microphone switch has two functions. When the top side is pressed it activates the "PTT" or push-to-talk for the selected communications radio. When the bottom is pressed, the flight interphone is active.

Crews do not like having to key the interphone to have normal conversation in the cockpit. It was not uncommon to see a rubber band wrapped around the switch to keep it engaged.

My airline has modified the yoke microphone switch to lock itself in the interphone position. A small ball rides up and over a mount extension.
  
   A tool adjusts the height of the ball. To far up..... the switch won't lock. To far down..... and it blocks the switch from being used.
  
   As a note: When the switch is locked in the interphone position, the cockpit speaker is muted out. It is assumed the both crew members have their headsets on for communication.
 

Yoke Microphone Switches    
  
                   

Orange in-line splices and pins.

Splice P/N  TSE-20-01 ( Reference )

Pin P/N 1841-1-5620 ( Reference )