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G1000 torque gauge question.

Old 17th Jul 2014, 13:21
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Hey morno……. you turbine guys keep saying how wonderfully easy they are compared to pistons.

As someone who is reasonably qualified to comment on the piston ops……MYTH BUSTED buddy
That's because I don't have to lean the bugger's, .

And now they're even easier with FADEC and no props, .
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Old 17th Jul 2014, 23:26
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The -10 has a perfect FADEC, and less trouble than yours
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Old 18th Jul 2014, 09:08
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Repost because I suffered from being the last person posting on page 1.

Quote:
SHP is worked out by Tq X RPM divided by 5252. So in reducing the RPM, you can increase the torque and produce the same SHP.
This always made me wonder. Say you left the RPM at the max setting and then increased the throttle to the maximum torque figure for the lowest RPM setting, other than having the engine output more than its book rated SHP what is the harm being done? No particular component is working harder* than it otherwise might have?

*or should I say beyond its limits.
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Old 18th Jul 2014, 10:10
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On a standard van, maxing both works out to be 705 SHP.

My understanding that it will put too much strain on the gearbox. Amount of power it is receiving vs the air density causes too much stress?

Just my guess.
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Old 18th Jul 2014, 10:19
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Blatant,

You are wondering what will happen if you deliberately over torque and engine... I'll let you think about that and see if you can work it our yourself.

BTW you don't have a throttle in a turbine....
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Old 18th Jul 2014, 11:21
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Blatant,

You are wondering what will happen if you deliberately over torque and engine... I'll let you think about that and see if you can work it our yourself.

BTW you don't have a throttle in a turbine....
Last time I checked some turbines had a thing called 'Auto-throttle'. Forgive this crucial error. Power lever then, I stand corrected.

No need to use that tone buddy. Exactly my point, is it really over-torquing? The gear box is having no more than the maximum torque allowable go through it. The Ng is within limits. The ITT is within limits. What is the limiting factor? Is it the way the engine is mounted to the airframe? Is it purely a certification thing?
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Old 18th Jul 2014, 12:43
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Exactly my point, is it really over-torquing? The gear box is having no more than the maximum torque allowable go through it. The Ng is within limits. The ITT is within limits. What is the limiting factor? Is it the way the engine is mounted to the airframe? Is it purely a certification thing?
Of course not! Mr Cessna just throws these figures out there for no reason whatsoever! Who'da thunk a manufacturer knows jack siht about a half a million dollar piece of machinary? And trend monitoring? That only gets downloaded to the manufacturers to waste a base pilot time for half an hour every week.

Limits exist for a reason. They help engines make Full TBO.
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Old 18th Jul 2014, 12:58
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The gear box is having no more than the maximum torque allowable go through it.
From my understanding of it, SHP is effectively the torsional energy being applied to the drive shaft via the power turbine and reduction gear. As you said, setting max Trq limit of 1970 with 1900rpm may not overspeed any component, but based on SHP definition, you have increased the stress imparted on the prop drive shaft. I would assume you will find yourself in all sorts of problems if it where to be overstressed and fail.

NG and ITT are indicators of the gas generator. That half of the engine could very well be within limits while your trying to make your prop depart the airframe.
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Old 18th Jul 2014, 13:16
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A quick mental calc to keep the max climb torque under control could be to reduce the max torque by about 70ft-lbs per 1000' above sea level, then adjust by +20ft-lbs for every degree Below 29 deg C OAT and -20ft-lbs for every degree over.
Works roughly for the temp ranges and altitudes most of them are flown in Australia (<10000' and 0-40deg C).

Of course you could always tape a copy of the Max Climb Torque graph to the visor and adjust every 1000-2000' ?
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Old 18th Jul 2014, 14:00
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Power Levers - Throttles. Who Cares?

Stick to your guns BL. Mr Lockheed has produced many fine C130 Hercules powered by turbo-prop Allison engines and they call the levers used to control engine power "Throttles". If they reckon they can be named throttles that will do me. Below an extract from a Lockheed Service Bulletin.

"The engine throttles and condition levers are mounted
in a quadrant on the flight control pedestal between the
pilot and co-pilot. The throttles are located to the left
of the condition levers and are used to make the desired
power settings. The throttle quadrant is marked for
different operating conditions from maximum reverse on
the ground to maximum power in flight"

Push him he GO - Pull him he STOP!!!!!
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Old 19th Jul 2014, 02:08
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My mistake I thought we where talking about C208's not C130's please continue...
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Old 19th Jul 2014, 02:47
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Hi
Most interesting discussion
Just another mechanic, but qualified PT6A and Cessna Caravan.
FWIW, my thoughts are that the ECTM module will record the exceedance, so will need to be interegated by technician - via laptop and that god awefull serial cable interface, and then a decision made.
From memory if the PRGB limit is exceeded it is a mandatory hot end inspection at minimum. maybe engine overhaul.
Having said that, the PT6 series is a very robust engine, and can take a lot of punishment.

Last edited by No Hoper; 19th Jul 2014 at 03:01.
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Old 19th Jul 2014, 11:17
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There's a ppruner on the other caravan thread that has seen 900hp out of a -114 from a newly rated pilot going to 2500 ft/lbs, would be interesting to know what the hot section's indications were...
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Old 19th Jul 2014, 11:18
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Explanation

OCTA, " BTW you don't have a throttle in a turbine..." In response to your statement just wanted to let Blatant Liar know that some turbine engine powered aircraft do have power levers or thrust levers, or what ever else you wish to call them, which are labelled "Throttles". Had you specifically said C208 did not have throttles I would not have commented.
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Old 19th Jul 2014, 22:49
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Just re-read my post Old fella and saw that is in fact what I said - I retract my comment.
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Old 24th Jul 2014, 05:49
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Not a 208 pilot, but been taking to one who is considerably experienced on type, and trolled his library for 208 info.

Beginning with serial number 372 (1044 for the B) Cessna fitted an Altair ETM which will record an exceedence if the engine is operated above the "maximum cruise power" as detailed in section 5. The ETM was fitted so as to make the engine eligible for a higher TBO. I guess the engineers must interrogate the ETM to determine what the TBO times for the various components may be.

That is not to say you can't exceed the max cruise power (but keeping within ITT, N1 limits), it's just that it will be logged and may impact the TBO.

The G1000 has a moving marker which will indicate the max cruise power applicable at the time.

Re horsepower. The first TQ red line is at 1865 and says "TO" next to it.

1865TQ X 1900RPM / 5252 = 675 horsepower

The second red line is the climb

1970TQ X 1800RPM / 5252 = 675 horsepower

Pull the RPM back while maintaining 1970TQ (assuming other limits are OK)

1970TQ X 1600RPM /5252 = 600 horsepower
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Old 25th Jul 2014, 01:48
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Power Levers - Throttles. Who Cares?

Pedantistry at its finest?

Throttles for mine, I don't care what anyone else calls them!
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Old 25th Jul 2014, 10:24
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Who Cares... indeed

Originally Posted by Howard Hughes
Pedantistry at its finest?
ahhhhmmmm... not wanting to split hairs or anything -but wouldn't that be Pedantry???

[PedantModeOff]

;-)
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