Aborted Start With Rising ITT
At 05:40 at a coastal PNG airfield, you attempt to start a turboprop engine using the aircraft battery. OAT is 24 °C, battery voltage is 22.4 V before start, and external power is not available. On the first attempt N1 rises to 22 % and stagnates; ITT climbs through 650 °C and is still rising at about 15 °C per second when you abort at 720 °C. The start limit is 750 °C for 5 seconds and 800 °C for 2 seconds, and the starter duty cycle is 60 seconds on, 5 minutes off. Fuel flow indicated 180 kg/h during the attempt; NG was 22 %; oil pressure was normal. The previous start was normal. The aircraft has had recent fuel-control rigging. You have one more attempt available before the starter limit is reached.
1. Diagnose the likely cause of this start. Explain why it is not a normal start and what the indicated parameters show.
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This is a hung, hot start: N1 stagnates at 22 % while fuel flow is 180 kg/h and ITT climbs rapidly. Fuel is being added without corresponding acceleration, so the excess energy goes into temperature. The low battery voltage of 22.4 V can cause a weak starter and slow acceleration, but recent fuel-control rigging is a stronger lead: a rich schedule or misrigged linkage can produce exactly this pattern. Ignition timing, late light-up and a weak starter are alternatives. The previous normal start does not rule out rigging drift.
A normal start should show steady N1 and NG acceleration with ITT peaking and then falling. Here the continued rise after abort is the warning.
2. State your next actions before any further start attempt. What limits, checks and records apply?
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Do not make an immediate second attempt. Allow the starter to cool for at least the 5-minute duty limit and let the engine cool; investigate first. Check the fuel-control rigging against the manual, the ignition exciter and leads, battery capacity and starter current. If the cause is not found, use external power and make one closely monitored attempt only if the manual permits; abort at the first sign of stagnation or at 750 °C.
Record the aborted start, peak ITT and duration. Treat any exceedance as a maintenance event requiring inspection. If rigging is suspect, do not fly until it is corrected and a satisfactory start is demonstrated.