CFM Leap-1A cooling time?

[Speed_Alive_V1]

Not a NEO driver, but I've heard various times that there is an extended start up time due to a dual engine cooling cycling being required upon engine start. Something to do with an evening out of temperatures throughout the powerplant to prevent thermal shock/expansion in the matierals, is that correct? Is it something like 50secs per side? Would someone have any documentation to explain?

Also is there a significant difference in start up time of the Neo outfitted with the Leap-1A or P&W1100G compared to previous iterations of the 320? Because of the cooling cycle? Is this extending turnaround times or negligible?

Thanks

[KRviator]

I haven't seen any documentation, but this thread discusses it a bit more: A320N Engine Start (https://www.pprune.org/tech-log/635501-a20n-engine-start.html), and tdracer puts it down to bowed rotor protection with EGT above a particular threshold...

[ahramin]

First of all, the start itself is a little slower. In addition, before starting the engine it will give you a cooling time based on temperature and time since the last shutdown. Cold engine is zero, for warm engine I've seen anything from 10 seconds to a couple minutes depending on how much time between shutdown and startup. There is now an option to cool both engines simultaneously before starting the first one, saving a minute or two on the total start time.

All in all the start process for the NEO can be 3-4 minutes longer than a CEO. If you're doing the cooling during pushback and starting the second engine during taxi, the difference is less significant.

[Speed_Alive_V1]

Exactly the type of thread I was looking for, thanks!

[Speed_Alive_V1]

Thanks for the reply - interesting stuff. Like someone mentioned in the thread linked above, I guess when you're squeezing out fuel efficiency, tolerences will be tighter so measures like this need to be taken for protection. You mentioned slower to start anyway, is that because of larger diameter fan, smaller core,or some other reason? Does the APU output the same starting force as on the CEO?

And I assume as the cooling cycle motors to 25% N2 it can't (/shouldn't, at least with doors not yet closed :p) be done on stand prior to push?

[FlightDetent]

Same as above.

PW installed on ours, the normal starting is longer. 10 or 20 seconds which occasionally feels like eternity.

The pre-start slow crank - cooling - scheduled by FADEC becomes an additional step of the automated sequence, required time (if any) is displayed on EIS after energising the circuits.

​​​For us, no cooling at all is a seldom occurrence, typically somewhere between 30 sec to almost 2 mins is needed.

In theory, it is not a problem at all and the delay is insignificant. Technically true but on a busy ramp you become an obstacle. Especially on a delicately timed day with congested bays, de-icing in progress and everybody's CTOT running out.

The mitigating DUAL COOLING is an additional button. After the first engine master SW is selected on, a paralell crank is commanded at once for both sides. So for starting the second engine the cooling is already done.

Dual Cooling itself has an operational envelope, think oil temperature, and sometimes you are denied. On a cold morning for example.

[FlightDetent]

The aircraft had been on the ramp for 23 hours with OAT between -5 to 3 °C, then flew one sector 3:30 block.

Single cooling required for the next start:


https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/316x612/single_cooling_2e327a6889d85e2b403b6b0d8d8aac262ede6d2a.png

[pineteam]

Hi FlightDetent,

This is a glitch. We have the same issue in our NEOs fleet. First flight of day: No cooling required on engine 1 but always cooling required on engine 2. I can email you the document but the reason given by Airbus is:

COOLING time can be displayed on one engine and not on opposite one
while both engines shutdown at same time/slot. This can occur for the first
start of the day, especially when bow effect is low or null, considering
engine thermal status. In that case, it would have been expected to not
have any required engine cooling or MtS.
This is due to MS failsafe value set, caused by engine OFF counter validity
lost.
The clock disagree is the main issue leading to inconsistent MtS, like
failsafe value while not required due to long TAT.
This clock disagree can occur at either A/C power OFF or a A/C
power ON. Identified causes are:
Clock unsynchronized at A/C power OFF (GPS mode vs
internal),
Clock invalidity at one EIU during EIU/EEC initialization (indeed
both EIU may not initialized at same speed); this leads to one
EIU gets ready earlier than the other while clock inputs not yet
valid. Therefore, EIU requires failsafe MtS.
Improvements

[FlightDetent]

Perfect info, thanks.

Somehow, the picture at #7 shows a subsequent start after the first sector of the day (3:30). Posted to illustrate it is witchcraft.