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High thrust operation on A320
As a fuel saving measure on the A320 (and all other a/c...) you can shut down the engine #2 during taxi-in.
Normally a 3 minute cool down period is considered before shutting down the engine. Books say that 3 minutes need to be considered after "high thrust operation". What is that? Do we need to take 3 minutes, only after a landing where full reverse was used? Or also after a landing with idle reverse? In this case the highest thrust has been on the ILS, in normal conditions around 45% N1. Any idea? |
If idle Rev was used for landing then you don't need to wait 3 min. Everything above idle rev requires 3min cooldown before shutdown.
Approach thrust on ils is not considered as high thrust. That is by SOP. It's of course somehow simplified as you can use rev thrust above idle but still less than approach thrust but then you need to cooldown for 3min. Hope it clarifies ;) |
The OEM may have some guidance here. GE at one time suggested a EGT limit for the 3 minute rule.
Don't know if that's still in place. |
For CFM engines Airbus has specified that the 3 minutes start when the engines are retarded to idle during landing provided idle reverse is used.
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Good, it's been a topic here as well, though I believe we did not found the time to seek manufacturer's clarification. O-2021 would you share any "official" data?
Sincerely, FD (the un-real) |
Hey, of course. The thing is that we've got a communication from Airbus a few months ago because there was a lot of confusion on this topic also for the operator I used to work for. Since then I changed operator but I'll ask a mate to forward me that mail.
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Our SOP is 3 mins cooldown regardless.
It could be a company thing rather than a manufacturer for us. 3-5 mins is about the required taxi time anyway for us to get to the gate in most airports that we operate. |
From Airbus
After landing, operate the engine at idle for 3 minutes before shutdown in order to thermally stabilize the hot section of the engine. We consider hight thrust level operation to be thrust setting above REV IDLE or above normal taxi maneuvering power. Therefore, if MAX REV is used for landing, the three minutes cooldown period starts when reverse thrust is reduced to REV IDLE. *However, *if the landing is performed with idle reverse thrust or no reverse thrust, the cooldown period starts when the thrust is reduced at idle prior to touchdown. During taxi, if the power level goes above the normal taxi maneuvering power, a cooldown has to be performed and the three minutes countdown starts when thrust is again at *( or near ) idle. Cheers. |
if the power level goes above the normal taxi maneuvering power Thanks :). |
The max. N1 during taxi is 40%.
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For a brief period of time (<2 yrs?, ?-2009) Airbus had a comment in the FCOM allowing a 1 min cooldown but they reverted back to 3 mins (after idle reverse) once GE saw in service results. Last time I spoke with our GE rep the recommendation re 1 min was only on an occassional basis for safety (crowded ramp) or exceptional operational reasons.
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We operate CFM and IAE types. Our SOP is that no wait is required for idle on IAE as idle rev is not a high power setting for this engine. BUT idle rev is a high power setting on the CFM so 2 mins id required.
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Max N1 Taxi
Originally Posted by Liftdumper
(Post 6210323)
The max. N1 during taxi is 40%.
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Originally Posted by makmoco
(Post 10475266)
Where can I find this exact limitation? Little, if any, power above idle thrust will be needed to get the aircraft moving (40 % N1 maximum).Thrust should normally be used symmetrically. Once the aircraft starts to move, little thrust is required |
FCOM PRO-NOR-SOP-22 for IAE Engines: Note: The flight crew should operate the engines at or near idle thrust for a cooling period of 3 min before engine shutdown, in order to thermally stabilize the engines. Idle reverse thrust and normal thrust to maneuver during taxi (i.e. at or near idle), are not considered as high thrust operations. Therefore, both of the following applies: ‐ If the flight crew uses idle reverse thrust for landing and normal thrust to maneuver during taxi after landing, the cooling period starts when the flight crew retards the thrust lever during the flare ‐ If the flight crew uses maximum reverse for landing, the cooling period starts when the flight crew sets the thrust lever to idle reverse during the landing rollout. However, if operationally necessary, all engines can be shut down when the aircraft arrives at the gate, regardless of the time necessary for landing. Before engine shutdown, routine cooling periods that last less than the recommended time, can result in engine degradation. CFM and NEO have a different guidance. Check the applicable FCOM in PRO-NOR-SOP-22 |
For the NEO with PW1100G engines, it's pretty much the same except they replaced the word '' should'' by '''must'' in the first sentence. And they removed that part too
However, if operationally necessary, all engines can be shut down when the aircraft arrives at the gate, regardless of the time necessary for landing. Before engine shutdown. |
Our company had a visit from CFM, and their take was the optimum cool down time was 15 minutes.
Anything shorter eats into engine's life. 3 min is a bare minimum, any further minute helps increase engine life. |
IAE engines used to define high thrust as greater than 1.02 EPR IIRC, EPR being their reference rather than N1. Coming to a stop during S/E taxi and having to get going again would usually result in this being exceeded, as would turning into a slightly uphill parking bay against the live engine or going over the fuel hydrant humps.
Seems to have disappeared from the FCOM now. |
It used to be worded that way in my FCOM as well, however that has changed since April 2017 in our FCOMs: THRUST LEVER THRUST lever....................................................... ............................................................ .AS RQRD The flight crew will need a little power above idle thrust to move the aircraft. L2 For additional information on the thrust use during taxi, Refer to FCTM/PR-NP-SOP-100 Taxi Roll and Steering. |
Originally Posted by safelife
(Post 10476755)
Our company had a visit from CFM, and their take was the optimum cool down time was 15 minutes.
Anything shorter eats into engine's life. 3 min is a bare minimum, any further minute helps increase engine life. |
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