ENG START A320
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ENG START A320
Hi..
during engine start N1 was rotating by windmiling effect , are there any limit for this phenomenon to avoid any damage to the rotor shaft and the starter??
during engine start N1 was rotating by windmiling effect , are there any limit for this phenomenon to avoid any damage to the rotor shaft and the starter??
The starter is connected to the N2, not N1.
Last edited by fdr; 22nd May 2023 at 06:56.
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Not really. Remember that N1 is essentially a free turbine, and will start to rotate in the correct sense once the N2 has started to build up, there is a lot more force from the flow induced by the N2 than from the airflow over the N1 fan blade. The windmilling of N1 is normally in a negative direction if the wind is from the front rear of the engine.
The starter is connected to the N2, not N1.
The starter is connected to the N2, not N1.
yes I know that starter is connected to N2 shaft
my doubts how to prevent any probability for cause damage for the tower shaft or starter splince since the rotation is in the opposite direction.
Shatwa07: the N2 shaft is connected to an ancillary gearbox and the load/drag from that will stop any possible rotation of the N2 simply from wind blowing through it.
As others have mentioned the N1 shaft is free to rotate and will do so with even quite light winds since it is so well balanced.
As others have mentioned the N1 shaft is free to rotate and will do so with even quite light winds since it is so well balanced.
Tailwind restrictions on starting have little to do with N1 twisting in the wind. Rather, the problem is that the effective back-pressure that a tailwind presents to the core can cause a hung or hot start.
Used to be a big problem with the JT9D engines (which didn't have a whole lot of stall margin to start with).
Used to be a big problem with the JT9D engines (which didn't have a whole lot of stall margin to start with).
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This thread might be the appropriate time to ask.
What about the 20% N2 limitation for starter engagement? After having heard the terrible sound of engaging the starter on a car when the engine is running, one has a tendency to avoid ever wanting to do it again.
Obviously this is a much different design than a car but an explanation of why it is OK up to 20% but not above would be interesting.
As for tailwind on start issues on the JT9D, I have seen 50 knots on a CF-6. Better design?
What about the 20% N2 limitation for starter engagement? After having heard the terrible sound of engaging the starter on a car when the engine is running, one has a tendency to avoid ever wanting to do it again.
Obviously this is a much different design than a car but an explanation of why it is OK up to 20% but not above would be interesting.
As for tailwind on start issues on the JT9D, I have seen 50 knots on a CF-6. Better design?
What about the 20% N2 limitation for starter engagement? After having heard the terrible sound of engaging the starter on a car when the engine is running, one has a tendency to avoid ever wanting to do it again.
Obviously this is a much different design than a car but an explanation of why it is OK up to 20% but not above would be interesting.
Obviously this is a much different design than a car but an explanation of why it is OK up to 20% but not above would be interesting.
).
the problem is that the effective back-pressure that a tailwind presents to the core can cause a hung or hot start
I suppose in a severe case reingestion could present issues, but I'm not aware of any actual problems on large commercial aircraft. The engine nacelles are rather large and long - and with huge bypass ratios - so any exhaust would likely be highly diluted before it made it's way back into the core inlet.
Granted, they were old, rather tied JT9Ds, but still
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It used to be common practice for the headset Eng to call out "positive N1" when starting into a tail wind. Particularly on RR RB211/Trents. During manual starts (old school) we used to have to wait for the call before opening the fuel cock.
