System Description by Don Pierce: Engine Start and Startup Sequence

"Don Pierce is a L-1011 Flight Test Engineer (Ship 3), then in Customer Training, then he had his own business doing maintenance training for L-1011 customers. Don is nothing but amazing in his knowledge of the L-1011. I am going to post several conversations on systems that I have had with Don over the past few weeks"



I will start with the photo of the ENGINE START panel.

The panel you have does NOT have the rotary Start Ignition select switch, which is located in the top center of the panel. Some airlines have it. It is a three-position switch, A/BOTH/B, which is used to select a single (or both) igniter(s).

I'll first go thru a sequence that is used during a normal engine start sequence.

1) The GROUND START switchights are solenoid held, and are latched in to initiate the start . This gives a command to open the associated start control valve to allow air (from the APU, another engine, or a ground cart) and begin the rotation of the compressors. The green VALVE OPEN light illuminates to indicate that the associated start control valve is NOT CLOSED. NOTE: This indication means the valve might be, lets say 3% open, allowing airflow, but there would be NO indication that the valve is partly open, since the indication operates at about 6%. This indication situation also applies to Pneumatics and Air Conditioning - with their "flow bars".

2) The amber PUSH legend in the momentary GND START RELEASE switchlight is illuminated any time a Ground Start switchlight (mentioned above) is latched in. Note: Power for the holding relay of the Gnd Strt switchlight goes through the GND START RELEASE switchlight when the latter switchlight is NOT pressed. So the start sequence can be interrupted at any time simply by pressing the GND START RELEASE switchight; the VALVE OPEN light will extinguish and the Gnd Start switchlight will "pop out".

3) When the N3 compressor (high speed compressor) reaches approximately 25% (the number varies by airline), the FUEL AND IGNITION toggle switch (not shown on the panel - but is located on the Center Console by the throttles) is moved from the OFF to ON position, allowing fuel to flow past the igniters, which are also activated at this time. This toggle switch must be pulled slightly out to be able to move it to the ON or OFF position. There is a "barrier" between each of the respective Fuel And Ignition toggle switches, to eliminate nuisance movement of adjacent toggle switches. For a few airlines the "barriers" have red lights that illuminates in event of a fire to advise the flight crew which engine to shut down.

Note that the FUEL AND IGNITION toggle switches also have a momentary ENRICH position. This position is used to supply additional fuel for starts on very cold days. It is generally referred to as Cold Day Enrichment. Since it is a momentary position, the switch must be held at the ENRICH position; the switch will revert back to the ON position when released from the ENRICH position..

4) When N3 reaches approximately 45%, the start control valve closes automatically and the VALVE OPEN light extinguishes. At approximately 51% N3, the GND START/ASSIST AIR START switchlight "pops out" automatically. Ignition is terminated at this time. The engine is now running "on its own".



The CONTINUOUS IGNITION switchlight is a latching switchlight, used when continuous ignition is desired - as in stormy weather. The white ON legend illuminates when the switchlight is latched in.

The FLIGHT START latching switchlight (for the respective engine ) is used when the flight crew determines that N3 rotation is sufficient for the restart of the engine. The start control valve is NOT used. The switchlight simply activates the ignitors. The white ON legend indicates switchlight position. The switchlight must be manually unlatched; it does NOT pop out automatically. Unlatching the switchlight will terminate ignition. This switchlight is labeled WINDMILL AIR START on most airlines.

The GROUND START switchlight (for the respective engine) is used when the flight crew determines that N3 rotation is NOT sufficient for the restart. In this situation the start control valve is used. The sequence of use is the same as in paragraphs 1) and 2). The switchlight is labeled GND START/ASSIST AIR START on most airlines.

To shut down the engine after its use (flight, taxiing, run-up, etc.), simply move the FUEL AND IGNITION toggle switch to OFF.