Jetstream 32 power concerns
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Jetstream 32 power concerns
Have been positioning around the Caribbean on an old J32 recently,and on my last trip,both sectors,we noticed the following,in climb and cruise:
Left engine torque,73..temp,600c...Right engine torque,63..temp 645c(5 degrees off yellow arc.)
The right engine was definitely being nursed to keep just out of yellow arc.
Question,common occurrence..or subject to imminent failure?
Regards,
A concerned YS!
Update..having done some research,maybe running these engines just out of EGT limits is standard practice..you tell me...
Left engine torque,73..temp,600c...Right engine torque,63..temp 645c(5 degrees off yellow arc.)
The right engine was definitely being nursed to keep just out of yellow arc.
Question,common occurrence..or subject to imminent failure?
Regards,
A concerned YS!
Update..having done some research,maybe running these engines just out of EGT limits is standard practice..you tell me...
Last edited by Yaw String; 27th Jan 2018 at 10:33.
It's been a few years now, but I worked line maintenance on a fleet of J31 airplanes. TPE-331s that "temp out" before reaching scheduled torque are often suffering from one or more of the following: Worn of damaged turbines, bleed air leaks, worn or damaged fuel nozzles, compressor or combustion liner damage. There are methods to troubleshoot and identify some troubles while others will only be found through visual inspection methods.
Yes, it possible that some operators have adjusted the temperature compensators (pilot foolers!) so as to cause the EGT indicators to indicate the EGT values inaccurately. (in either direction) It's also possible that the torque indicating system is faulty.
As a factory service center for TPE and TFE engines, our outfit encountered this discrepancy regularly. Step one would be a visual and borescope inspection followed by a test run and compare the run parameters with the values recorded on the Customer Data Sheet. (usually completed at the last overhaul or original build) If we saw an engine temping out with no obvious signs of visible damage or excessive wear, then we'd be required to temporarily replace the customer propeller with a calibrated test club and perform a bleeds blocked lebow (torque and temp indication calibration) run. The only factory recognized method to determine the true power output of a TPE-331 amounts to the practical equivalent of a full-on test cell run with specifically calibrated equipment.
The results of these tests usually found excessive and premature hot section wear/erosion. Lab analysis and metallurgical examination of the worn parts often found evidence of prolonged over-temperature operation by the customer. We often found that airline customers in particular had adjusted their temp compensators well beyond the maximum values specified on their engine data sheets. This has the effect of causing the cockpit EGT gauge to read well below what they should, leading to accelerated temperature related wear rates and a statistically increased likelihood of failure.
Then again I remember one engine that gained 15 degrees of EGT margin just from receiving a compressor wash! (a firefighting aircraft)
The TTL should keep it from grossly over-temping, but the reduction in available power might concern me on a runway or obstacle critical takeoff. I'd also take note that the more times an engine is run at critical temperature, the faster it wears. And the faster it wears, the more likely it is to suffer a hot section parts failure. Usually, with a normally operating engine it's only a small likelihood....
Yes, it possible that some operators have adjusted the temperature compensators (pilot foolers!) so as to cause the EGT indicators to indicate the EGT values inaccurately. (in either direction) It's also possible that the torque indicating system is faulty.
As a factory service center for TPE and TFE engines, our outfit encountered this discrepancy regularly. Step one would be a visual and borescope inspection followed by a test run and compare the run parameters with the values recorded on the Customer Data Sheet. (usually completed at the last overhaul or original build) If we saw an engine temping out with no obvious signs of visible damage or excessive wear, then we'd be required to temporarily replace the customer propeller with a calibrated test club and perform a bleeds blocked lebow (torque and temp indication calibration) run. The only factory recognized method to determine the true power output of a TPE-331 amounts to the practical equivalent of a full-on test cell run with specifically calibrated equipment.
The results of these tests usually found excessive and premature hot section wear/erosion. Lab analysis and metallurgical examination of the worn parts often found evidence of prolonged over-temperature operation by the customer. We often found that airline customers in particular had adjusted their temp compensators well beyond the maximum values specified on their engine data sheets. This has the effect of causing the cockpit EGT gauge to read well below what they should, leading to accelerated temperature related wear rates and a statistically increased likelihood of failure.
Then again I remember one engine that gained 15 degrees of EGT margin just from receiving a compressor wash! (a firefighting aircraft)
The TTL should keep it from grossly over-temping, but the reduction in available power might concern me on a runway or obstacle critical takeoff. I'd also take note that the more times an engine is run at critical temperature, the faster it wears. And the faster it wears, the more likely it is to suffer a hot section parts failure. Usually, with a normally operating engine it's only a small likelihood....
