Turboprop pilots past and present
06-13-2009 | 01:54 PM
#21
ULTP-Ultra Low Tier Pilot
Joined: Dec 2007
Posts: 3,228
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Juice is correct.
From an engineering standpoint, "power," = Force x Velocity. The traditional method to rate this in the US is Horsepower, which is 550 ft-lbs/second.
It's been a while since I've flown a turboprop, and I don't know the particulars of your engine, but here's a hypothetical example:
Torque: 1800 ft-lbs
RPM: 2400
"Average" Prop radius (To calculate average "speed" of the blade): 4 ft
Math:
1800 ft-lbs x 2400 rpm x 4 ft / 60 sec per minute (to convert RPM to RPS); then /550 to change ft-lbs/sec to horsepower
Answer: 523 hp.
How the engine develops that torque or rpm is irrelevant. Doesn't matter if the ITT split is 100 degrees: power is determined by ft-lbs/sec.
A way to prove it: if your turn coordinator is sensitive enough, the ball will move towards the higher-powered engine if the guy is matching ITT. ("Step on the good engine;" just like in engine-out practice)
From an engineering standpoint, "power," = Force x Velocity. The traditional method to rate this in the US is Horsepower, which is 550 ft-lbs/second.
It's been a while since I've flown a turboprop, and I don't know the particulars of your engine, but here's a hypothetical example:
Torque: 1800 ft-lbs
RPM: 2400
"Average" Prop radius (To calculate average "speed" of the blade): 4 ft
Math:
1800 ft-lbs x 2400 rpm x 4 ft / 60 sec per minute (to convert RPM to RPS); then /550 to change ft-lbs/sec to horsepower
Answer: 523 hp.
How the engine develops that torque or rpm is irrelevant. Doesn't matter if the ITT split is 100 degrees: power is determined by ft-lbs/sec.
A way to prove it: if your turn coordinator is sensitive enough, the ball will move towards the higher-powered engine if the guy is matching ITT. ("Step on the good engine;" just like in engine-out practice)
06-13-2009 | 06:27 PM
#25
Gets Weekends Off
Joined: Oct 2008
Posts: 1,154
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From: none ya...
06-13-2009 | 06:49 PM
#26
Gets Weekends Off
Joined: Sep 2008
Posts: 239
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I was taught to "slave" the weak engine (one with higher ITT) to the stronger engine by matching your torques. Seems like the best way to go for overall flying characteristics and engine wear. But, what do I know...I had 3000+ with PT-6s under my belt before I got stuck in the SAAB.
06-13-2009 | 06:53 PM
#27
Gets Weekends Off
Joined: Feb 2008
Posts: 313
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From: CRJ FO
ATR 72: you match torque...and the synchronizer does that as well. Never heard of matching ITT. I've seen engines 20 degrees different from each other with the same torque, rpm and nearly same fuel flow.
Since ITT is of little use of an indication of true power I can't see why you'd match it.
I think I would've asked (liked I was totally clueless) what the reasoning behind that was... you would've probably had the answer in excruciating detail.
Since ITT is of little use of an indication of true power I can't see why you'd match it.
I think I would've asked (liked I was totally clueless) what the reasoning behind that was... you would've probably had the answer in excruciating detail.
06-13-2009 | 07:41 PM
#28
Gets Weekends Off
Joined: Mar 2008
Posts: 280
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From: Beech 1900D
Thanks for all the replies guys! I flew BE-1900's before this and EMB-120's and we always matched torque as to not exceed ITT limitations. His reasoning was so that fuel flow would be the same and prevent an imbalance and therefore the need to crossfeed.
Me: "then we are flying sideways".
Him: "just trim it out".
Me: "we could pull the power out all the way on one engine and center the ball, but we would still be flying sideways".
Him: "we are not flying sideways that much".
Me: "Okay if that is the way you want it done then that is the way I'll do it"
He was obviously the captain.
Me: "then we are flying sideways".
Him: "just trim it out".
Me: "we could pull the power out all the way on one engine and center the ball, but we would still be flying sideways".
Him: "we are not flying sideways that much".
Me: "Okay if that is the way you want it done then that is the way I'll do it"
He was obviously the captain.
06-14-2009 | 06:37 AM
#29
Gets Weekends Off
Joined: May 2006
Posts: 187
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no see, u match the ITT's at maximum continuous power, hope for at least 3500lbs on one side and maybe 3000 on the other. Who cares if you're flying sideways, as long as you can under block every flight, and prove to the company that 20 minutes turns are just too long because all the pilots get board with all the free time after running to the bathroom, getting food, fueling, and cleaning the plane.
06-14-2009 | 07:57 AM
#30
Gets Weekends Off
Joined: Sep 2007
Posts: 155
Likes: 0
From: CA
I use the deice air pressure gauges to set power.
In all seriousness, some guys like to do things different to add an element of mystique to their flying. Sounds like you are flying with one of these guys. In trying to be different, they end up just looking like boneheads.
In all seriousness, some guys like to do things different to add an element of mystique to their flying. Sounds like you are flying with one of these guys. In trying to be different, they end up just looking like boneheads.
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