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jcmc1405

T5 temperature question

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Hello Mathjis and support staff.

I have been flying this bird a lot these days, a real joy to fly. However I have some questions regarding T5 temperature. Is this affected by OAT and surface temperature in the simulation?.It seems like it is impossible to reach the values on the performance tables. I mean, flying at 8000 ft the engines can produce only 30-32 of torque pressure without going to an over temperature "T5" (and a subsequent engine fire). So I am reaching average cruise speeds of 130 knots. Is this normal?. I have talked to pilots of my local airline ADA (they have a lot of twin otters). They told me they reach 145-160 knots. Is it possible that I am doing something wrong?.

Greetings from a very happy customer.

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Yes T5 is affected heavily by OAT.

Most performance charts are using ISA conditions ie. 15°C / 59°F at 1013 mbar / 29.92 InHg.

Also note that max continous torque changes with altitude.

Open the checklist and select the configuration page. On the two torque gauges there are blue marks indicating max continuous torque under the present conditions.

If Your actual torque goes beyond that mark the needles will become red, indicating that Your overtorqueing and thus is prone to overtemp.

Finn

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How did I miss this little gem..

Must have been reading documents late at night.

(snip)....On the two torque gauges there are blue marks indicating max continuous torque under the present conditions.

If Your actual torque goes beyond that mark the needles will become red, indicating that Your overtorqueing...(snip)

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Yes T5 is affected heavily by OAT.

Most performance charts are using ISA conditions ie. 15°C / 59°F at 1013 mbar / 29.92 InHg.

Also note that max continous torque changes with altitude.

Open the checklist and select the configuration page. On the two torque gauges there are blue marks indicating max continuous torque under the present conditions.

If Your actual torque goes beyond that mark the needles will become red, indicating that Your overtorqueing and thus is prone to overtemp.

Finn

Yes. I do understand. What I mean is, whereas the T5 temp red zone is reached, I only have ie. 32 of torque. When the limit indicated in that gauge you mention is much higher. That is heavily limiting my cruise speed.

Edit: I forgot to mention that I'm flying in the torrid zone, where the ISA atmosphere conditions are never present. Here we can easily reach 35 Celsius degrees at sea level. I know that has a huge impact on aircraft performance. However, I can't reach the speeds that my pilot friends say they reach. Maybe there's something else I am missing?

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Have you tryed pulling your prop settings back a bit this should get you out of the red on the T5. and your cruise speed should be around 160 to 170 below 10.000ft

Regards

Keith

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Have you tryed pulling your prop settings back a bit this should get you out of the red on the T5. and your cruise speed should be around 160 to 170 below 10.000ft

Regards

Keith

I usually reduce the RPM to 90% as it is recommended in the performance tables. But that isn't having a big impact on T5. Although it does have a big effect in torque.

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Propeller setting should not affect T5.

The Aerosoft Twin Otter Extended PT6 simulation is to a degree based on figures derived from this PT6 simulator:

http://selair.selkirk.bc.ca/training/systems/Alsim%20engine%20operation.html

Finn

Yeah. I see. In the end there is nothing I can do to control the T5 temp. So I guess I will be flying this bird at average speeds of 130 knots.

Thank you

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How have You setup weather ??

With surface temps (at sea level) around 35°C You should see OAT temps around 19-20°C at 8000 ft.

Finn

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To add to Finn's statement, the standard lapse rate is -2oC per 1,000 feet (-3.5oF). So at a standard sea level day of 15oC, you hit the freezing level at 7,500 feet.

For specialized purposes, there are other lapse rates for dry air (3oC per 1,000') and moist (saturated) air (1.5oC per 1,000').

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How have You setup weather ??

With surface temps (at sea level) around 35°C You should see OAT temps around 19-20°C at 8000 ft.

Finn

Thank you for your help Finn

For weather purposes I use Active sky 2012

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Thank you for your help Finn

For weather purposes I use Active sky 2012

AS2012 is great - I use that too.

Just note that it can happen that AS2012 can put wrong temperatures into the sim, which You also can read in Hifi's own support forum.

When in doubt - check the OAT gauge just above the captains head.

Finn

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