Flex.Temp. Assumed Temp.

[Wennerholm 44]

Hi! I use flex.temp 58 in the tutorial #1. If I use flex.temp 65 , will the aircraft use more or less power at T/O? I believe that if I use a higher assumed temp my 747 will use less power. I do not know if I get it right or wrong.

[rondon9898 84]

The higher the assumed temperature, the greater the power reduction. The engines produce less thrust at higher temperatures because the air density is reduced. What you're doing, figuratively, is making the engine think the outside air temp is much hotter than it is, thus artificially reducing the power output.

Edit add: Also, I don't think Beoing chaps call it FLEX thrust - that's an Airbus/Fokker term

[Wennerholm 44]

Just now, rondon9898 said:

The higher the assumed temperature, the greater the power reduction. The engines produce less thrust at higher temperatures because the air density is reduced. What you're doing, figuratively, is making the engine think the outside air temp is much hotter than it is, thus artificially reducing the power output.

Edit add: Also, I don't think Beoing chaps call it FLEX thrust - that's an Airbus/Fokker term

Thank´s, very much!

[Wennerholm 44]

Thank`s very much!

 

[PMDG777 231]

3 hours ago, rondon9898 said:

The higher the assumed temperature, the greater the power reduction. The engines produce less thrust at higher temperatures because the air density is reduced. What you're doing, figuratively, is making the engine think the outside air temp is much hotter than it is, thus artificially reducing the power output.

Edit add: Also, I don't think Beoing chaps call it FLEX thrust - that's an Airbus/Fokker term

To add to this a little (you're exactly right John), an assumed temp (the Boeing term) of 58C means you're tricking the FADEC controllers into thinking it's 58C outside, but it might actually only be 30C. Pilots do this because higher thrust puts more stress on the engine components, so reducing the max thrust available at take-off can increase the life of the engine components. Of course there's a limit to how low you can reduce the thrust since you still need to get off the ground by the end of the runway!

[Wennerholm 44]

Just now, PMDG777 said:

To add to this a little (you're exactly right John), an assumed temp (the Boeing term) of 58C means you're tricking the FADEC controllers into thinking it's 58C outside, but it might actually only be 30C. Pilots do this because higher thrust puts more stress on the engine components, so reducing the max thrust available at take-off can increase the life of the engine components. Of course there's a limit to how low you can reduce the thrust since you still need to get off the ground by the end of the runway!

   Yes, I understand that. I travel with aircraft Sweden-China about once a month all year around in my real life work. I have notice that domestic flight in China use a very little distance of the runways and the sound from the engine sounds, for me, like full thrust. They also taxi in a higher speed compere to flight in Sweden. I guesses that they do not care to much about money or the environment. Domestic flight in China often use A319 and A320.

[Captain Kevin 586]

8 minutes ago, Ken Wennerholm said:

Domestic flight in China often use A319 and A320.

I'd think most domestic flights tend to use smaller planes like the A320 or the 737. Unless you're in Japan where they might use the 777 or even some US carriers fly the 767 or 777 domestically.

[Wennerholm 44]

Just now, Captain Kevin said:

I'd think most domestic flights tend to use smaller planes like the A320 or the 737. Unless you're in Japan where they might use the 777 or even some US carriers fly the 767 or 777 domestically.

Yes, Japan use 747 for domestic flight:-) 

[Captain Kevin 586]

10 minutes ago, Ken Wennerholm said:

Yes, Japan use 747 for domestic flight:-) 

Not anymore, they don't. Japan Airlines and ANA retired their 747s a few years back.

[Wennerholm 44]

Just now, Captain Kevin said:

Not anymore, they don't. Japan Airlines and ANA retired their 747s a few years back.

   Ok! I did not know that. It was several years since I visited Japan. My wife´s closest friend is from northern Japan. I Think I know what caused the planet to make a sharp bank angel and step dive during the last flight. It was the Affinity Mask in my fsx.config. file.

   The right engine stopped working and and the right aileron malfunction. Also FSX. CTD. When i remove the Affinity mask everything get back to normal status. N1 on all four engine is now stable and the rudder works fully both on right and left turn.

[paradoxbox 13]

Japan uses 777-200's and 777-300's for the routes the 747-400D's used to fly. It also uses 737-800's on some routes (With more flights now than with the 747's)

 

Korean Air still has a few 747's they use for very short flights, for example Seoul Gimpo to Cheju island - I think this is about a 1 1/2 hour flight or so, maybe a bit longer.