I pilot the PMDG 737 in my simulator and I know that before takeoff and before landing, the start switches must be set to CONT mode and at high altitudes in FLT mode. But what exactly are CONT and FLT mode? What they do ?
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asked Feb 23, 2020 at 4:05
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1$\begingroup$ You really shouldn't accept an answer quite that quickly - it's generally recommended to wait a couple days for Stackers in other time zones to have a chance to respond. $\endgroup$– VikkiFeb 23, 2020 at 4:40
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1$\begingroup$ Oh ok. This is a craze that I have come from other platforms, sorry. $\endgroup$– JeanExtreme002Feb 23, 2020 at 4:43
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$\begingroup$ No worries. :-) And now you know! $\endgroup$– VikkiFeb 23, 2020 at 4:45
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$\begingroup$ If an answer is (in the opinion of the OP) complete, clear, and it answers the question, then why shouldn't it be accepted? Could you please provide a link/clarification as to "it's generally recommended"? Some answers (ideally all, in fact) are entirely fact-based. If the question is, say, "What's the ceiling of X model" and there is an answer, with sources, what's the point of waiting? $\endgroup$– user12873Feb 23, 2020 at 5:10
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1 Answer
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The 737 has two separate engine-igniter systems (each of which has igniters on both engines). Each engine has four possible igniter modes (except for earlier-model Originals, which have five) - in clockwise order 'round the knob, they're GND, OFF, CONT (or, for early Originals, L IGN and R IGN), and FLT.
- CONT mode turns one of the igniter systems on (which igniter system is used depends on the position of a separate switch), and is used for takeoff and landing.
- GND mode on an Original or Classic, or on an NG that's on the ground, also uses a single igniter system, and is used for ground-starting the engines.
- FLT mode turns both igniter systems on, the better to help keep the engines operating under adverse conditions, or maximise the chance of a successful midair relight. In the real world, FLT mode is used only in conditions posing a significant risk of engine flameout (for instance, extreme turbulence or very heavy rain), or if a flameout has already occurred and one or both engines need to be restarted in flight - not for high-altitude cruise flight in general.
- On an NG, GND mode is another option for inflight restarts, in which case it uses both igniters (unlike how it operates for ground starts).
- Your simulator might be confusing FLT mode with OFF mode (neither igniter system operating), which is the setting normally used in flight (as combustion in a gas-turbine engine is generally self-sustaining unless the engine, or its fuel or air supply, is severely abused).
Additionally, on an NG, the EECs can automatically switch both igniter systems on (if an engine flames out) or off (if bad things happen during ground-starting), no matter what the position of the ignition knobs.
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1$\begingroup$ @JeanExtreme002, please either create a new question, or edit the question to cover all modes. Diverging discussion does not work well on this site as it orders posts by votes, not time. $\endgroup$ Jun 27, 2021 at 17:53