Cold and low operation with N1 and ITT gauges only
CRJ200 for example has non FADEC engine and only N1, N2 and ITT gauges and is flat rated to 23 degrees C. If I operate from the airport where temperature is -20 and I accidently put 20 into the FMS for N1 thrust calculation will I get any information that something is wrong and engine parameters are exceeded during takeoff roll? As I understand N1 will stay in the green range ITT will be in a green range too but certified engine thrust rating will be exceeded without any cockpit indication? Is there any risk associated with a such mistake except takeoff path looking more like F16 is departing?
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If you exceed maximum takeoff/go-around N1 for a given OAT, you are effectively overboosting the engines. The risk is that you are putting more load on the engine components that they are design to withstand.
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Originally Posted by FlyingStone
(Post 10900353)
If you exceed maximum takeoff/go-around N1 for a given OAT, you are effectively overboosting the engines. The risk is that you are putting more load on the engine components that they are design to withstand.
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100% (or whatever the limit is), is rotational limit of the low-speed shaft, it's not a thrust limit. You can only see the latter by inputting the correct temperature into the FMC, which I assume (not familliar with type) calculates the thrust limit on the CRJ.
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Originally Posted by FlyingStone
(Post 10900397)
100% (or whatever the limit is), is rotational limit of the low-speed shaft, it's not a thrust limit. You can only see the latter by inputting the correct temperature into the FMC, which I assume (not familliar with type) calculates the thrust limit on the CRJ.
And the answer is no. But also, the error is opposite of what OP wrote. Inputting a higher temp results in a lower, not higher, N1. |
Originally Posted by Vessbot
(Post 10900684)
But also, the error is opposite of what OP wrote. Inputting a higher temp results in a lower, not higher, N1.
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Originally Posted by Turbavykas
(Post 10900773)
This is not correct. If you input higher temperature RPM will be higher till the flat rate temperature. After flat rate temperature RPM will go down again due to ITT limitation.
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Originally Posted by Turbavykas
(Post 10900329)
CRJ200 for example has non FADEC engine and only N1, N2 and ITT gauges and is flat rated to 23 degrees C. If I operate from the airport where temperature is -20 and I accidently put 20 into the FMS for N1 thrust calculation will I get any information that something is wrong and engine parameters are exceeded during takeoff roll? As I understand N1 will stay in the green range ITT will be in a green range too but certified engine thrust rating will be exceeded without any cockpit indication? Is there any risk associated with a such mistake except takeoff path looking more like F16 is departing?
Any sort of warning that you've exceeded the engine rating on non-FADEC (or a FADEC operating in alternate mode) would need to come from the aircraft side (FMC or similar). Not familar with the CRJ, but on most Boeing models, when operating N1 engines in Alternate mode, there is an EICAS caution message if you exceed the max rated N1 by more than 2% (as calculated by the FMC based on aircraft sensed Total Temp - not any manually input temp). |
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