just wondering about the cruise power setting PC-12 drivers use across the country:
our SOP's restrict it at 720 ITT and 100% NG while the cruise limitations in the POH mention 760 ITT and 104% NG...
that lower power setting represents a loss of about 8-10 kt at FL 240 and adds an extra 25 min of air time per sched days which is a big cost considering that these planes fly between 1500-2000Hrs/year...
Any comments?
Gowest
PC-12 cruise power setting?
Moderators: lilfssister, North Shore, sky's the limit, sepia, Sulako, I WAS Birddog
Where I flew PC12 we used the same power setting. It's true that it reduce the speed, but the fuel flow is lower also so your consumption is lower per mile than if you where cruising at the limits. Another reason why we did that was that when you have only one engine, you don't whant to push it to hard, you whant to be friendly with it.
I’m not PC-12 Driver but a BE20 one see if this helps.
8-10kts is really nothing from an operating position. You need to look past the speed issue and get into other things.
Running an engine at 100% versus 104%. The POH says you can run at 104%. But look at it from this point. Let’s say the engine spins at 38,000rpm at 100%, and at 104% it is at 39,500 rpm. Over one hour, your engine has worked less by 91,200 rpm, thus allowing less wear on parts. This usually allows the engine to extend its life past the TBO.
The second would be the difference in fuel savings. The less fuel used the better. My guess it is close to 100lbs an hour savings, so the extra 25 minutes, is still less fuel, thus less cost per mile or more profit, you can look at it both ways.
8-10kts is really nothing from an operating position. You need to look past the speed issue and get into other things.
Running an engine at 100% versus 104%. The POH says you can run at 104%. But look at it from this point. Let’s say the engine spins at 38,000rpm at 100%, and at 104% it is at 39,500 rpm. Over one hour, your engine has worked less by 91,200 rpm, thus allowing less wear on parts. This usually allows the engine to extend its life past the TBO.
The second would be the difference in fuel savings. The less fuel used the better. My guess it is close to 100lbs an hour savings, so the extra 25 minutes, is still less fuel, thus less cost per mile or more profit, you can look at it both ways.
good point tintin (et milou?) but when those guys designed the PT6A-67B they had in mind that pilots are not very cautious and added already a big safety margin in setting those limitations, so why not using that engine to the limits it was design to?
Go west young men, go west...
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co-joe
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I don't see fuel burn being the answer. People out there just seem to think that running at a little less temp means longer engine life, which is brobably true, but then they assume that lower RPM is also going to give longer life which really has no truth.
At my last company red line wasn a limit...it was a goal. Straight from management down to the check captains. They have hundreds of PT6's and have the longest on condition program in canada
You can't wreck a PT6 by running red line torque or N1, the only way to do damage is to over temp. That's why the transient torque limits are soo high.
Besides I didn't think single engine turboprops could run on condition in a commercial air service.
At my last company red line wasn a limit...it was a goal. Straight from management down to the check captains. They have hundreds of PT6's and have the longest on condition program in canada
You can't wreck a PT6 by running red line torque or N1, the only way to do damage is to over temp. That's why the transient torque limits are soo high.Besides I didn't think single engine turboprops could run on condition in a commercial air service.
A bit off topic, but say you work 20 days a month. That's an extra 100 hrs a year just for obeying the SOPs!
Also, from what I've seen pilots seem to stray a touch high on SOP power settings so by setting them a bit lower than the designed maximum there is a built in margin for error.
Also, from what I've seen pilots seem to stray a touch high on SOP power settings so by setting them a bit lower than the designed maximum there is a built in margin for error.
The PC-12 has a cruise power chart which will be below the 36/720/100 you are used to when cruising at 240. Look in the POH. On days when you operate at ISA-30 which you will in a couple months, the number in the POH and you SOP will become very close to each other.
Yes the engine is certified to 36.96/760/104. But that costs a lot more money for the company. Maintenance watchs the amount of TRQ you get for a given ITT. When the TRQ gets too low, overhaul time, (or 3500 hrs whatever comes first)
The numbers you are using came from Kelner and most if not all operators have adopted them.
Like someone else before you said, you are building hours. Enjoy it.
Yes the engine is certified to 36.96/760/104. But that costs a lot more money for the company. Maintenance watchs the amount of TRQ you get for a given ITT. When the TRQ gets too low, overhaul time, (or 3500 hrs whatever comes first)
The numbers you are using came from Kelner and most if not all operators have adopted them.
Like someone else before you said, you are building hours. Enjoy it.
It's better to break ground and head into the wind than to break wind and head into the ground.
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uber pilot
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PC12 power setting
we use 760 to climb and 720 to cruise or 760 to cruise if required. Single engine turbines do also follow under on condition approval as well. I to do not believe the engine comes out any better running at lower limits, our O/h reports show no added saving doing so. Short answer is follow manufacturer recommendations and you can't go wrong!
36.9
720/760
104%
36.9
720/760
104%
760 ITT is the Max cruise setting allowed by Pratt and Whitney. 740 ITT is the max setting according to Pilatus. It seems everybody that operates them uses 720 ITT. But think about it realistically, do you really want to be useing the max allowed setting out of 3 recommended numbers on a single engine aircraft. It only stands to reason that using the 760 setting is putting the max wear on the engine out of the 3. Personally while up there I'd rather stick to the 720 and give up 6KTS. I log 11.9 hours per sched day and I'll gladly give up the few KTS and keep it running. Plus the cost savings over a year are enormous but I'll post those figures at another time.
I seem to remember that drag is proportionate to the square of the velocity. ergo the slight reduction in speed should equal a commensurate drop in FF. fuel tends to be the largest cost for companies nowadays. The extra .4 on a 12 hr flight time day, would even itself out fairly quickly. As to the engines, 2 things kill turbines, heat and rotation the stresses on the wheel are once again based on the square of the velocity. turbine blade materials tend to lose their tensile strength in the last 50 degrees of temp. this allows the blade to stretch under the increased rotational load and causes seal rub or other damage. It's a single take care of your engine!
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sprucemonkey
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Turbines don't like heat - lower thrust lower heat longer engine life; that's why reduced-thrust take-offs are used.
If you're leasing out, specify lower temp/torque, customer has to take longer to get there, higher lease payments lower overhaul costs. Lessor could care less about fuel burn.
Run it harder, lower lease costs - higher fuel burn.
If you're leasing out, specify lower temp/torque, customer has to take longer to get there, higher lease payments lower overhaul costs. Lessor could care less about fuel burn.
Run it harder, lower lease costs - higher fuel burn.
"What's it doing now?"
"Fly low and slow and throttle back in the turns."
"Fly low and slow and throttle back in the turns."
When I first started flying turbines years ago. Managment wanted us to ru n them at max cruise all the time.
I rember thinking I wouldn't run my car like this why the airplane, but whatever PT6s are bullet proof right. I even asked the CP at the time, and the answer was " just do what managment tell us" kinda deal. Well next thing we know we are flying like this for 7 months. Maintenence finds that some of the ITT probes have been melted and we were running at 50 degrees over max cruise. - $90, 000 later we were back to running at 720 degrees.
We didn't know we are only as good as the guages right.
My recomendendation is see what your POH says you may find that 720 in the winter like one poster said is to high and you are torque limited at cruise before even reaching 720. This is a perfect oppritunity to baby that single engine.
Its just a machine man they do and will break.
I rember thinking I wouldn't run my car like this why the airplane, but whatever PT6s are bullet proof right. I even asked the CP at the time, and the answer was " just do what managment tell us" kinda deal. Well next thing we know we are flying like this for 7 months. Maintenence finds that some of the ITT probes have been melted and we were running at 50 degrees over max cruise. - $90, 000 later we were back to running at 720 degrees.
We didn't know we are only as good as the guages right.
My recomendendation is see what your POH says you may find that 720 in the winter like one poster said is to high and you are torque limited at cruise before even reaching 720. This is a perfect oppritunity to baby that single engine.
Its just a machine man they do and will break.
- NoseDraggers Suck
If someone has the numbers they could work it out to see if fuel is the answer. I don't have the exact numbers, but it goes something like this....
These are fake numbers, so someone plug the real ones in.....
100Ng= 600pph.
104Ng= 660pph.
~7lb per gallon
~$4 per gallon
Increase in airspeed = 6kts.
Average reduction on 60 minute sector = 2.5 min
Dry operating cost = $400/h
Average dry ops savings per 60min sector = $16
Average increase in fuel cost = 57.5min*60pph/7*4 = $35
You get the idea. Those numbers are obviously way off, but I think if you plug in the real ones, the results might be surprising.
These are fake numbers, so someone plug the real ones in.....
100Ng= 600pph.
104Ng= 660pph.
~7lb per gallon
~$4 per gallon
Increase in airspeed = 6kts.
Average reduction on 60 minute sector = 2.5 min
Dry operating cost = $400/h
Average dry ops savings per 60min sector = $16
Average increase in fuel cost = 57.5min*60pph/7*4 = $35
You get the idea. Those numbers are obviously way off, but I think if you plug in the real ones, the results might be surprising.
Last edited by JigglyBus on Thu Sep 21, 2006 4:05 pm, edited 1 time in total.
EXCELLENT point about the ITT probes, Stearman.
On a PT-6, the indicated ITT is an average of the 8 (?) probes. If one probe is kaput, that probe is still included in the average...but as a zero value. So with one failed probe, the actual ITT is going to be 12.5% higher than indicated. On a twin, this is easily noticeable as an ITT split. On a single, as Stearman aptly pointed out you're just melting your engine until you finally realize it at the next inspection. Cheers
On a PT-6, the indicated ITT is an average of the 8 (?) probes. If one probe is kaput, that probe is still included in the average...but as a zero value. So with one failed probe, the actual ITT is going to be 12.5% higher than indicated. On a twin, this is easily noticeable as an ITT split. On a single, as Stearman aptly pointed out you're just melting your engine until you finally realize it at the next inspection. Cheers
