Question for turboprop pilots (specially king air c90)
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Question for turboprop pilots (specially king air c90)
Hi,
since I have expierence only with C172 I curious to know how turboprop engines work, so I tried to fly kingair C90 in my home flght simulator and use POH for checklist and limitations but I have some question because I not sure FSX simulates turboprops as in real live.
1. in torque gauge and POH I see red line at 1315 but in takeoff when advanced the throttles to full forward the torque rise up to 1460 then go back to ~1420 so I needs to reduce power for 1315
2. also when change for climb power, when I reduce RPM from 2200 to 2000, the torque rise from 1315 to ~1500 so again I needs to deduce power for 1315 limitation
3. again in transition to cruise, I reduce Torque to 800-900 but when reduce RPM the Torque rise to something ~1100 then I reduce power to 900.
I know the fact reducing RPM will rise the torque but I dont know if this simulator size of change in torque is true for real engine behavior
since I have expierence only with C172 I curious to know how turboprop engines work, so I tried to fly kingair C90 in my home flght simulator and use POH for checklist and limitations but I have some question because I not sure FSX simulates turboprops as in real live.
1. in torque gauge and POH I see red line at 1315 but in takeoff when advanced the throttles to full forward the torque rise up to 1460 then go back to ~1420 so I needs to reduce power for 1315
2. also when change for climb power, when I reduce RPM from 2200 to 2000, the torque rise from 1315 to ~1500 so again I needs to deduce power for 1315 limitation
3. again in transition to cruise, I reduce Torque to 800-900 but when reduce RPM the Torque rise to something ~1100 then I reduce power to 900.
I know the fact reducing RPM will rise the torque but I dont know if this simulator size of change in torque is true for real engine behavior
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The KingAir C90A is one of the types that I fly occasionally. At sea level, the torque would go well above 1315 if you pushed the power levers to the stop, so you must be careful to set no more than 1315. The torque does rise noticeably when the rpm is reduced, and the amount of rise you mention is probably roughly correct. When reducing from take-off power to climb power, the first step is to pull back the power levers to reduce the torque to around 1000. Then reduce the rpm, which will cause the tongue to rise, and then adjust the power levers to set 1315 torque.
if the air temperature is well above standard, you may hit the 695 degree ITT limit before you reach 1315 torque, so you must watch that too - i.e. set 1315 torque or 695 ITT, whichever you reach first. On some aircraft, at higher altitude, the 101.5% gas generator speed limit will come into play before hitting either the torque or ITT limit.
if the air temperature is well above standard, you may hit the 695 degree ITT limit before you reach 1315 torque, so you must watch that too - i.e. set 1315 torque or 695 ITT, whichever you reach first. On some aircraft, at higher altitude, the 101.5% gas generator speed limit will come into play before hitting either the torque or ITT limit.
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Thanks for the answer.
so in transition from takeoff to climb power
when reducing torque to 1000, change rpm from 2200 to 2000 will rise torque around ~1300 ?
in take off, how mutch time take the engine to spool up from idle to takeoff power ?
thanks
so in transition from takeoff to climb power
when reducing torque to 1000, change rpm from 2200 to 2000 will rise torque around ~1300 ?
in take off, how mutch time take the engine to spool up from idle to takeoff power ?
thanks
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What will happen if you accidentally increase torque beyond allowed ? Like hitting turbulence while moving the throttles? Complete engine rebuild? Is there a FADEC version where you don't need to worry about this any more?
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There are two types of engines for tp's
Free turbine and fixed shaft.
Their operation is different.
And if you over torque them it depends on by how much and what the OEM says to do.
It can just be a oil sample taken (SOAP) and prescribed periods or it could be the engine has to go into the engine shop for strip down.
Some aircraft do have limiting systems on them even though they are not FADEC.
But in general pilots are taught not to rely on them. Unless you were on approach you wouldn't have your hand on the power levers in turbulence. And if your on approach you wouldn't be anywhere near the top of the range.
Free turbine and fixed shaft.
Their operation is different.
And if you over torque them it depends on by how much and what the OEM says to do.
It can just be a oil sample taken (SOAP) and prescribed periods or it could be the engine has to go into the engine shop for strip down.
Some aircraft do have limiting systems on them even though they are not FADEC.
But in general pilots are taught not to rely on them. Unless you were on approach you wouldn't have your hand on the power levers in turbulence. And if your on approach you wouldn't be anywhere near the top of the range.
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Originally Posted by tomerhm
so in transition from takeoff to climb power
when reducing torque to 1000, change rpm from 2200 to 2000 will rise torque around ~1300 ?
when reducing torque to 1000, change rpm from 2200 to 2000 will rise torque around ~1300 ?
Originally Posted by tomerhm
in take off, how mutch time take the engine to spool up from idle to takeoff power ?
So, when setting take-off power, move the power levers slowly until the ITT has recovered from its initial sudden spike, then more them more quickly until both props have achieved 2200 rpm, then set 1315 torque. At higher altitude, or warmer temperature, the engine will each 695 ITT before achieving 1315 torque, so you must use the lower torque for take-off.
The whole thing, from idle to take-off power, will take perhaps 6 or 8 seconds.
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FYI
C90GTi
TQ LIMITATIONS
TKOF & MAX CONT: 1,520 (13)
Cruise climb & max cruise: 1,520 (6) (13)
Transient: 1,626 (10)
NOTES:
(6) cruise TQ values vary with altitude & temp.
(10) the value is limited to 20 seconds.
(13) ... inadvertent torque excursions up to 1,550 ft-lbs are time-limited to 7 minutes.
TQ LIMITATIONS
TKOF & MAX CONT: 1,520 (13)
Cruise climb & max cruise: 1,520 (6) (13)
Transient: 1,626 (10)
NOTES:
(6) cruise TQ values vary with altitude & temp.
(10) the value is limited to 20 seconds.
(13) ... inadvertent torque excursions up to 1,550 ft-lbs are time-limited to 7 minutes.
Last edited by avionimc; 3rd Jan 2015 at 15:42. Reason: addition