PT6A-67D Power settings ??????
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PT6A-67D Power settings ??????
Guys, posted this question in Tech Log forum but didn't get a response, maybe someone here can help ?
I fly for a private organization that has recently purchased an aircraft fitted with a couple of P&W PT6A-67D engines and I would like to know what other operaters are using as a standard power setting. You see my boss thinks that 'long range cruise" is the best (feels as if you could get out and run faster) but will allow us to use "intermediate cruise power" (slightly faster) but calls the "high speed cruise" (from the AFM) "emergency power" (his words!!). Now considering that at ICP the turbines are idling along at 92 to 93 percent and even at HSC they are only running at 96 to 97 (which, if I remember back to my BGT theory,is where the designers anticipated they would spend most of their working days and where they are most efficient) and that Max. Continuous is 104%, would we be doing anything to shorten the life of the engine or increase overhaul costs (bosses justification for the LRC policy) by running them at the higher power setting? There is another consideration here and that is operting costs.If, for example, this beast costs, say, $2000 an hour to operate and we make it go faster then at the end of the month (and we do about 100 hors per month) we could well save about 10% in flight time, or $20,000. Okay, so there will be an increase in fuel burn but the extra fuel, even at todays prices , is cheaper than flight time.
Anyone out there have a comment on this one??
I fly for a private organization that has recently purchased an aircraft fitted with a couple of P&W PT6A-67D engines and I would like to know what other operaters are using as a standard power setting. You see my boss thinks that 'long range cruise" is the best (feels as if you could get out and run faster) but will allow us to use "intermediate cruise power" (slightly faster) but calls the "high speed cruise" (from the AFM) "emergency power" (his words!!). Now considering that at ICP the turbines are idling along at 92 to 93 percent and even at HSC they are only running at 96 to 97 (which, if I remember back to my BGT theory,is where the designers anticipated they would spend most of their working days and where they are most efficient) and that Max. Continuous is 104%, would we be doing anything to shorten the life of the engine or increase overhaul costs (bosses justification for the LRC policy) by running them at the higher power setting? There is another consideration here and that is operting costs.If, for example, this beast costs, say, $2000 an hour to operate and we make it go faster then at the end of the month (and we do about 100 hors per month) we could well save about 10% in flight time, or $20,000. Okay, so there will be an increase in fuel burn but the extra fuel, even at todays prices , is cheaper than flight time.
Anyone out there have a comment on this one??
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Read the 1900D POH and if that doesn't give you the answer, read it again - more carefully!
And if you still have questions call the engine manufacturer, telephone (07) 3268 0000 and ask for a Field Service Engineer. He should also be able to send you their brochure of pilot handling notes.
And if you still have questions call the engine manufacturer, telephone (07) 3268 0000 and ask for a Field Service Engineer. He should also be able to send you their brochure of pilot handling notes.
but calls the "high speed cruise" (from the AFM) "emergency power" (his words!!).
From what I hear 3000 lbs TQ 1400RPM works quite well.
Suggest you look at this as well http://www.tc.gc.ca/aviation/applica...US92-27-19.htm
No continous Ops betwqeen 94% and 97.1%.
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It also depends a lot on sector times that the aircraft is used for.
Those engines are very thirsty and so on a short 15-20 minute flight, you'll still be chomping through 500-550Lbs/hr (each) of jet A, even back at around3000lbs Tq.
There wont be much of an increase in speed (and therefore reduced flight time) if you set max continuous power low altitudes, but the fuel flow will increase to over 600Lbs/hr (each).
However if your sector times are longer, say 1-2 hours, that increased fuel flow getting to the higher altitudes is more than off-set by quite a high TAS, as the TQ starts to reduce thru about FL150 and ITT limited at around FL230-250, you should get around 400-450Lbs/Hr /side FF.
Having said all that, you should get nowhere near max NG of 104% before you get to an ITT or TQ limit, I don't recall ever seeing one over about 101%!
By reducing or limiting the power settings and ITT limits will definitely increase the longevity of the engine and very high TBOs can be acheived. You'll need to talk that over with your engineers and Pratt though, and probably need to have history of operating PT6s.
My 10c worth would be:
set 3000 to 3500Lbs TQ below about 10000ft. Above that, MCP until TQ or ITT limited (either company or manufacturer limit). Go high. Look at the tables.
Hope that helps!
Those engines are very thirsty and so on a short 15-20 minute flight, you'll still be chomping through 500-550Lbs/hr (each) of jet A, even back at around3000lbs Tq.
There wont be much of an increase in speed (and therefore reduced flight time) if you set max continuous power low altitudes, but the fuel flow will increase to over 600Lbs/hr (each).
However if your sector times are longer, say 1-2 hours, that increased fuel flow getting to the higher altitudes is more than off-set by quite a high TAS, as the TQ starts to reduce thru about FL150 and ITT limited at around FL230-250, you should get around 400-450Lbs/Hr /side FF.
Having said all that, you should get nowhere near max NG of 104% before you get to an ITT or TQ limit, I don't recall ever seeing one over about 101%!
By reducing or limiting the power settings and ITT limits will definitely increase the longevity of the engine and very high TBOs can be acheived. You'll need to talk that over with your engineers and Pratt though, and probably need to have history of operating PT6s.
My 10c worth would be:
set 3000 to 3500Lbs TQ below about 10000ft. Above that, MCP until TQ or ITT limited (either company or manufacturer limit). Go high. Look at the tables.
Hope that helps!
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Shredder6
What prop setting do you use? In my company we always fly around with props 1400 and 3000 ftlb (driving Miss Daisy power as I call it). This generally gives an IAS of around 200 kts. The prop setting is mainly for noise reduction.
Our average sector length is about 40 mins but there is a fair bit of variation from 25 mins to 1:40.
I understand many operators use props 1550 and varying torque settings.
What prop setting do you use? In my company we always fly around with props 1400 and 3000 ftlb (driving Miss Daisy power as I call it). This generally gives an IAS of around 200 kts. The prop setting is mainly for noise reduction.
Our average sector length is about 40 mins but there is a fair bit of variation from 25 mins to 1:40.
I understand many operators use props 1550 and varying torque settings.
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CC
We use 1550 in the climb, 1400 cruise, descent and landing, (1550 at the crew's discression if conditions warrant).
It's definitely quieter with props back.
We generally set power to the torque limit at low altitudes (although between 3000-3500lbs is still a good for 220-225kts), and the
temp (ITT) limit at high FLs, IAS around 200kts, dependant on the weight at the time.
'Course, that speed drops right off if the FO's been into the pie warmer at the airport cafe!
We use 1550 in the climb, 1400 cruise, descent and landing, (1550 at the crew's discression if conditions warrant).
It's definitely quieter with props back.
We generally set power to the torque limit at low altitudes (although between 3000-3500lbs is still a good for 220-225kts), and the
temp (ITT) limit at high FLs, IAS around 200kts, dependant on the weight at the time.
'Course, that speed drops right off if the FO's been into the pie warmer at the airport cafe!
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PT6A-67D Power settings ??????
When I used to fly them (Ds only), the operator had done flight tests to see if there was any better cost benefits to be found.
What they found for an average temperature of ISA + 20 For the D was, any sector over 40min, we went to F230 or above and used a cruise regime that was found to be just below High Speed Cruise as follows:
Prop setting remained 1550 rpm
Torque - F250 - 2100ftlbs - FF 640 pph - TAS 260
F240 - 2200ftlbs - FF 680 pph - TAS 264
F230 - 2300ftlbs - FF 720 pph - TAS 268
These settings gave a SAR that was better than Intermediate Cruise figures but gave us better sector times.
It was also 200ftlbs below High Speed Cruise and gave us the option of if the anti ice was needed, we could push the levers back to the 2100 - 2300 setting, the fuel flow then was the same and we only lost a couple of kts TAS - the penalty was increased temperatures, but still well below max.
Any altitude below F230, we went to Intermediate Cruise, and at F180 and below we set a max FF of 800 pph and matched torques to limiting side, otherwise she was too thirsty (all prop settings stayed at 1550 for ease of operation, but a bit more noisy than 1400).
The D hates anything below F230, and she was made to get up there quickly and stay as long as possible.
Hope this helps.
TWB
What they found for an average temperature of ISA + 20 For the D was, any sector over 40min, we went to F230 or above and used a cruise regime that was found to be just below High Speed Cruise as follows:
Prop setting remained 1550 rpm
Torque - F250 - 2100ftlbs - FF 640 pph - TAS 260
F240 - 2200ftlbs - FF 680 pph - TAS 264
F230 - 2300ftlbs - FF 720 pph - TAS 268
These settings gave a SAR that was better than Intermediate Cruise figures but gave us better sector times.
It was also 200ftlbs below High Speed Cruise and gave us the option of if the anti ice was needed, we could push the levers back to the 2100 - 2300 setting, the fuel flow then was the same and we only lost a couple of kts TAS - the penalty was increased temperatures, but still well below max.
Any altitude below F230, we went to Intermediate Cruise, and at F180 and below we set a max FF of 800 pph and matched torques to limiting side, otherwise she was too thirsty (all prop settings stayed at 1550 for ease of operation, but a bit more noisy than 1400).
The D hates anything below F230, and she was made to get up there quickly and stay as long as possible.
Hope this helps.
TWB
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Mr Pt6
For any PT6 related issues suggest you contact Peter at MR PT6 ltd.
Ph (07)3802 2163 / 0405 737 085
Email: [email protected]
Ph (07)3802 2163 / 0405 737 085
Email: [email protected]
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Shredder6
IMHO that's the way they should be operated. No wonder you guys keep overtaking us
These engines are operating so far below their design limits that I doubt there would be much of an engine life concern with the slightly higher torque settings your using, and I don't think prop gearboxes are too much of a problem. Surely the slight increase in fuel burn is outweighed by the reduction in hours.
Although, I'm sure there are reasons for the lower power settings as well, and I am just a driver. Perhaps someone with a bit more relevant expertise than me could comment.
IMHO that's the way they should be operated. No wonder you guys keep overtaking us
These engines are operating so far below their design limits that I doubt there would be much of an engine life concern with the slightly higher torque settings your using, and I don't think prop gearboxes are too much of a problem. Surely the slight increase in fuel burn is outweighed by the reduction in hours.
Although, I'm sure there are reasons for the lower power settings as well, and I am just a driver. Perhaps someone with a bit more relevant expertise than me could comment.
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Thanks for the input folks, you've raised some interesting points. I was particularly concerned after I checked out that link provided by by "27/09" even though it was dated 1992 I took it to our engineering types for an opinion. They had never heard of it but did a check just to make sure and advised us that it doesn't apply to our machine. I guess P&W have had fourteen years to overcome the problem that caused the 94.0 to 97.1 restriction. And I agree, if you can go to 5000 ft/lbs and 1700 for 20 seconds then HSC (high speed cruise) can surely be doing no damage.
"Shredder6" when you say you set the torque limit, are you talking max continuous i.e. 3750 ?? And what ITT limit were you using in the climb? The book says that 720 was used to calculate the published climb performance figures??
Thanks again,
igv
"Shredder6" when you say you set the torque limit, are you talking max continuous i.e. 3750 ?? And what ITT limit were you using in the climb? The book says that 720 was used to calculate the published climb performance figures??
Thanks again,
igv
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IGV
Yep, 3750Ft/LBS in the climb up to an ITT limit of 760 which is the factory temp limit, and for the cruise we use a company ITT limit which is slightly less than that.
Will check-up on the 720 ITT limit for climb performance calculations but that sounds a bit odd, particularly with the above mentioned climb ITT limit.
Yep, 3750Ft/LBS in the climb up to an ITT limit of 760 which is the factory temp limit, and for the cruise we use a company ITT limit which is slightly less than that.
Will check-up on the 720 ITT limit for climb performance calculations but that sounds a bit odd, particularly with the above mentioned climb ITT limit.
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Cool
Normally we cruise at about 3000 lb and 1550 rpm and 1400 for a quieter flight. For decent we pull back to about 2500 lb and 1550 and in the traffic pattern I use about 1500 lb and 1550
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Cloud clutter, how come you guys fly aroung with torque limit of 3000 lbs whether you are at 4000ft of 25000ft.
If at say 4000 feet you might have an ITT of 670 and at alt up around the flight manual limit of 760 or what ever your company limit may be.
It seems to me that a high ITT is what will wear your engine out not the torque setting.
We find getting there faster is cheaper than the bit of extra gas you use with the higher power setting.
Have never had any engine problems due to using the ITT as a limit in 7 years in both the 65B and 67D engines
The flight manual is fine for setting your power but does not allow for a tired engine with a high ITT as ITT is not mentioned in the power setting tables.
Also no high speed cruise at 1400RPM for the D, dont like the idea of flying around around at 1550rpm all day, the bloody thing is loud enough at 1400 if you are sitting by the engines!
If at say 4000 feet you might have an ITT of 670 and at alt up around the flight manual limit of 760 or what ever your company limit may be.
It seems to me that a high ITT is what will wear your engine out not the torque setting.
We find getting there faster is cheaper than the bit of extra gas you use with the higher power setting.
Have never had any engine problems due to using the ITT as a limit in 7 years in both the 65B and 67D engines
The flight manual is fine for setting your power but does not allow for a tired engine with a high ITT as ITT is not mentioned in the power setting tables.
Also no high speed cruise at 1400RPM for the D, dont like the idea of flying around around at 1550rpm all day, the bloody thing is loud enough at 1400 if you are sitting by the engines!
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Mate I don't fly them any more, but I agree with what you're saying. The main thing was standardisation I think so that all the muppets like me in the company could work out what they were doing.
A lot of people wouldn't dream of cruising with props 1400, but that's the way my company did it. As you say, it's loud either way.
A lot of people wouldn't dream of cruising with props 1400, but that's the way my company did it. As you say, it's loud either way.
