Boeing 737 Memory Items – Aborted Engine Start

JohanAero

When something goes wrong while flying on the Boeing 737, we use the QRH (Quick Reference Handbook). We just have to find out the correct NNC (Non Normal Checklist) and then we just read it and execute it.

For some of these checklists, we have memory items, meaning we have to know by heart some actions.

I have listed 9 memory items:

  • Aborted Engine Start
  • Airspeed Unreliable
  • APU Fire
  • Cabin Altitude Warning / Emergency Descent
  • Engine Overheat
  • Engine Fire, Severe Damage or Separation
  • Engine Limit or Surge or Stall
  • Loss of Thrust On Both Engines
  • Runaway Stabilizer

Aborted Engine Start

Engine start lever (affected engine) ...........................CUTOFF

We do this checklist for one or more of the following conditions:

  • No N1 rotation before the engine start lever is raised to IDLE detent.
  • No oil pressure indication by the time the engine is stabilized at IDLE.
  • No increase in EGT within 15 seconds of raising the engine start lever to IDLE detent.
  • No increase in, or a very slow increase in N1 or N2 after EGT indication.
  • EGT rapidly approaching or exceeding the start limit. (725°C for start-up)

One of the most common reason we would use the aborted engine start is for a hot start. https://www.skybrary.aero/index.php/Hot_Start

Boeing 737 engine start procedure.

When starting an engine, we simply put the engine start lever to IDLE position. We always keep our hand on the lever so we can put it to CUTOFF if something goes wrong.

During the engine start procedure, we monitor closely the engine parameters on the upper and lower display unit. We first put the engine start switch to GROUND. This switch uses battery power to open the start valve which in fact lets high pressure come from the APU. This allows to rotate the starter. The starter rotates the N2 compressor through the accessory drive gear system. So, we verify N2 rotation, oil pressure and wait for at least 25% N1 rotation. From that moment, we move the engine start lever to IDLE. This opens the fuel valves and causes the EEC (Engine Electronic Control) to supply fuel and ignition to the combustor where the fuel ignites. At starter cutout speed (approx 56% N2), power is removed from the start switch holding solenoid. The engine start switch returns to OFF, the engine bleed air valve returns to the selected position and the start valve closes.

On a standard day, sea level, approximate stabilized idle indications for CFM56 engine:

N1 RPM - 20%
N2 RPM - 59%
EGT - 410°C
Fuel Flow 272 KGPH

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