80SE “low-rpm”
05-19-2012, 12:01 PM
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80SE “low-rpm”
Hi all
My 80SE had a turbine stop due to “low-rpm” during flight today. Voltage were fine, but min-rpm = 18.200 , min temp=338C and V_pump_min = 0,7V seems rare to me. Normal idle pump voltage is 0,4Volt (I think).
I was throttling down to idle in a moderate dive after full throttle – do you think it might be blown out? I did’nt se any white smoke, and it seemed just to stop during idle.
I newer had any fuel line issues, or flameouts before. Turbine has 8 hours run in total.
My 80SE had a turbine stop due to “low-rpm” during flight today. Voltage were fine, but min-rpm = 18.200 , min temp=338C and V_pump_min = 0,7V seems rare to me. Normal idle pump voltage is 0,4Volt (I think).
I was throttling down to idle in a moderate dive after full throttle – do you think it might be blown out? I did’nt se any white smoke, and it seemed just to stop during idle.
I newer had any fuel line issues, or flameouts before. Turbine has 8 hours run in total.
05-19-2012, 01:04 PM
#2
RE: 80SE “low-rpm”
The most likely cause is a pump overshoot to the low side. Far enough that the engine rpm got below the preset cutoff. In other words, the pump didn't respond as well as it should to the ECU commands and it allowed the rpm to get down to somewhere below 28k or so (wherever the cutoff is set at the factory) and the ECU turned the motor off. The shutdown parameters you report are just wherever the engine was when it got around to recording the data and aren't the exact numbers for the cutoff point.
The engine is ok. You can get out the GSU and check how well your pump responds. Just get the engine running in the mid range or max and do a throttle chop to idle. Observe the minimum rpm on the GSU. You could easily see 3,000 - 5,000 or more rpm below normal idle for a not so good pump. This can be worse (or better) in the air. Conversely, you could see an overshoot at the high end as well.
Seen this often enough in flight, mostly in the traffic pattern where the engine dies when pulling the throttle to idle in the base turn or on final.
If you verify the pump allows an rpm overshoot as described, there are work arounds I've used in the past if you don't want to buy a pump. First you might want to look and see where the IdleThrResponse is set in Limits. I usually use Fast, but you can try Normal, Slow or Very Slow and see if that helps.
Also you can go into Limits and raise the idle rpm 2,000 or so to give more margin on the cutoff. If you can't do with the extra rpm you need to slow down how fast you reduce the throttle to idle. I have a method to do this in the Tx if all else fails.
The engine is ok. You can get out the GSU and check how well your pump responds. Just get the engine running in the mid range or max and do a throttle chop to idle. Observe the minimum rpm on the GSU. You could easily see 3,000 - 5,000 or more rpm below normal idle for a not so good pump. This can be worse (or better) in the air. Conversely, you could see an overshoot at the high end as well.
Seen this often enough in flight, mostly in the traffic pattern where the engine dies when pulling the throttle to idle in the base turn or on final.
If you verify the pump allows an rpm overshoot as described, there are work arounds I've used in the past if you don't want to buy a pump. First you might want to look and see where the IdleThrResponse is set in Limits. I usually use Fast, but you can try Normal, Slow or Very Slow and see if that helps.
Also you can go into Limits and raise the idle rpm 2,000 or so to give more margin on the cutoff. If you can't do with the extra rpm you need to slow down how fast you reduce the throttle to idle. I have a method to do this in the Tx if all else fails.
05-20-2012, 02:33 AM
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RE: 80SE “low-rpm”
Hi Thud
Thanks for your reply!!
I tested this low-idle overshoot from full throttle yesterday, but it didn't go below 36k (=idle). Full throttle had also no overshot ("Fast" ) I will test it again next time.
Throttle to low was "Normal", but I will try changing it to Slow, and I will lift the idle throttle a bit while the retract is up.
Thanks alot
Thanks for your reply!!
I tested this low-idle overshoot from full throttle yesterday, but it didn't go below 36k (=idle). Full throttle had also no overshot ("Fast" ) I will test it again next time. Throttle to low was "Normal", but I will try changing it to Slow, and I will lift the idle throttle a bit while the retract is up.
Thanks alot
05-20-2012, 10:16 AM
#4
RE: 80SE “low-rpm”
Sounds like the pump is fine, maybe even better than a lot I've seen. There may other possibilites or it's a one off we'll never have an answer for.
If you get a normal flight in, you might look at the recorded min & max rpm's and the temp's for the flight just to see if anything obvious is happening.
If you get a normal flight in, you might look at the recorded min & max rpm's and the temp's for the flight just to see if anything obvious is happening.
