-
at 95% APU speed, the ECB de-energizes the ignition system.
When you release the MASTER SW pushbutton switch:
-the shutdown sequence is started (Ref. 49-61-00),
-
at 70% APU speed, the ECB energizes the ignition system,
-
at 7% APU speed, the ECB de-energizes the ignition system.
IGNITION - DESCRIPTION AND OPERATION
____________________________________
1.
General
_______ The ignition system gives the constant high-energy ignition which ignites the fuel/air mixture in the combustion chamber. It operates during the start sequence when the APU speed is between 7 % and 60 %. The Electronic Control Box (ECB) controls the ignition system fully automatically.
2.
Component Location
__________________
(Ref. Fig. 001)
-------------------------------------------------------------------------------FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA | | | | DOOR | REF. -------------------------------------------------------------------------------IGNITION UNIT 315/ 315AL 49-41-38 316 316AR IGNITER PLUG 315/ 315AL 49-41-41 316 316AR ELECTRICAL LEAD - IGNITER PLUG 315/ 315AL 49-41-43 316 316AR
3. System Description
__________________ (Ref. Fig. 001) The ignition system ignites the fuel/air mixture in the combustion chamber of the APU during the start sequence. The main components are:
-
an ignition unit,
-
an igniter plug,
-
an igniter plug electrical-lead. The ignition unit is a completely self contained unit, installed on the lower left side of the APU. This ignition unit produces the electrical energy that is needed to ignite the fuel-air mixture in the combustion chamber. An electrical lead delivers the electrical energy to an igniter plug, screwed into the combustion chamber. The ECB switches off the ignition unit when the combustion flame can support itself. The high efficiency components of the ignition system guarantee a minimum ignition spark energy of 1 joule, a high-voltage of 18 KV pulse. This is regulated to a spark rate of 2 to 10 sparks per second. The system components are sealed to minimize the possibility of any contact with flammable fluid or vapours in the APU compartment.
R EFF : 001-049, 101-105, 107-107, 151-199, 49-41-00Page 1 201-210, Config-2 Aug 01/05
CES
Ignition System - Component Location
Figure 001
CES
4. Component Description_____________________
A. Ignition Unit The ignition unit is installed inside a nickel-plated aluminum box that is hermetically sealed. This protects the components inside the box against the environmental effects of moisture and altitude. The ignition unit is shop-repairable only.
B. Igniter Plug Electrical-Lead The electrical lead is made up of a Teflon-insulated center conductor, shielded with a nickel-copper inner braid. This is covered with a convoluted flexible tube of spirally wound nickel-iron alloy with a nickel-copper outer braid jacket. The electrical lead is installed between the ignition unit and the igniter at the left side of the the APU.
C. Igniter Plug The igniter plug is made up of an electrode, an insulator and a two-piece outer shell. The electrode is made of tungsten-alloy and the insulator is made of aluminum-oxide-alloy. The outer shell is made of stainless steel and has cooling holes to aid in reducing tip temperatures to extend tip electrode life. The tip ground electrode contains iridium wear inserts to resist high temperature spark erosion.
5. Operation/Control and Indication________________________________ (Ref. Fig. 002) When you push the MASTER SW 14KD and the START 2KA pushbutton switches:
-the start sequence is started (Ref. 49-42-00),
-
at 7% APU speed, the ECB energizes the ignition system. The ignition unit supplies high-voltage electrical energy through the electrical lead to the igniter plug. Thus the fuel-air mixture in the combustion chamber ignites,
-
at 60% APU speed, the ECB de-energizes the ignition system.
When the APU speed is below 95% due to flame out the ECB triggers the
ignition unit to operate to recover the APU speed to 100%.
R EFF : 001-049, 101-105, 107-107, 151-199, 49-41-00Page 3 201-210, Config-2 Aug 01/05
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