xavier1
1st May 2016, 23:23
Hi, I have some doubts about EGT vs ITT in turbofan aircrafts.
I am wondering which are the differences (operational, not technical or mechanical) about the ITT vs. the EGT.
As you may know, piston aircrafts, like the Bonanza A36... use a method to know if the engine combustion is ok, called EGT peak.
Due the air is less dense as soon we ascend (that is we have less oxigen in it), things burn bad. You would burn better a match at 0 feet than in the acme of the Everest mountain (29,029 feet). So things high don't burn so well... because we don't have much oxigen.
Due aircrafts fly, and sometimes high, they need to change the mixture (air and fuel) inside the engine.
When we fly high, we need less fuel and more air (lean mixture), that is because we need more air to burn the fuel. Due the air have less oxigen... we need to put more air inside the engine, so the fuel would burn better.
When we fly low... we need more fuel and less air (rich mixture), that is because we have a lot of oxigen in the air... so we don't need a lot of air to burn our fuel.
However... how do we know if the things are burning as they should inside the engine?
Very simple, measuring the gases temperature. How? With a termomether in the exhaust pipes.
We put a thermometer in the exahust pipes of the aircraft, to measure the gases temperature. Measuring the gases temperature, we can know if the engine is burning well (we must have the highest temperature possible) or if the engine is burning bad... then we will have a low temperature in the gases... as a candle fainting.
The goal of the EGT peak is... to enrich or lean the mixture, moving the red levers in the aircraft...forward or rearward... until we get the higest temperature for the gases. We can see that in the cockpit, because we must have an indicator, called EGT, that show us a needle. The objective here is to have the EGT needle in its highest possition.
Then, we need to move again the red levers to enrich or lean the mixture to make the EGT needle drop a bit. The goal now is to make the EGT needle drop a bit... around 20º degrees or what is specified in the performances tables.
However, we have two options. We can reduce the temperurate enriching the mixture, we move the red lever forward or we can reduce the temperature leaning the mixture, we have move the red lever, rearward. The goal here is, after reaching the peak, cooling a bit the temperature, making the peak drop in the number of degrees indicated in the performances tables, and we can make the peak drop by enriching (moving the red levers forward) or by leaning (moving the red levers backwards) the mixture.
That is in essence, the EGT peak.
However, I would need to know which differences do we find in the ITT versus the EGT.
I'm wondering if ITT is the same as EGT in an operational mode?
I mean, I am not interested right now about mechanical things, such as were is the thermometer located or stuff like that.
What I need to know is how do I operate the ITT? Do I need to find a the peak in the ITT such as in the EGT?
And then dropping the temperature?
If you could help me with this, I'd be grateful.
Cheers
I am wondering which are the differences (operational, not technical or mechanical) about the ITT vs. the EGT.
As you may know, piston aircrafts, like the Bonanza A36... use a method to know if the engine combustion is ok, called EGT peak.
Due the air is less dense as soon we ascend (that is we have less oxigen in it), things burn bad. You would burn better a match at 0 feet than in the acme of the Everest mountain (29,029 feet). So things high don't burn so well... because we don't have much oxigen.
Due aircrafts fly, and sometimes high, they need to change the mixture (air and fuel) inside the engine.
When we fly high, we need less fuel and more air (lean mixture), that is because we need more air to burn the fuel. Due the air have less oxigen... we need to put more air inside the engine, so the fuel would burn better.
When we fly low... we need more fuel and less air (rich mixture), that is because we have a lot of oxigen in the air... so we don't need a lot of air to burn our fuel.
However... how do we know if the things are burning as they should inside the engine?
Very simple, measuring the gases temperature. How? With a termomether in the exhaust pipes.
We put a thermometer in the exahust pipes of the aircraft, to measure the gases temperature. Measuring the gases temperature, we can know if the engine is burning well (we must have the highest temperature possible) or if the engine is burning bad... then we will have a low temperature in the gases... as a candle fainting.
The goal of the EGT peak is... to enrich or lean the mixture, moving the red levers in the aircraft...forward or rearward... until we get the higest temperature for the gases. We can see that in the cockpit, because we must have an indicator, called EGT, that show us a needle. The objective here is to have the EGT needle in its highest possition.
Then, we need to move again the red levers to enrich or lean the mixture to make the EGT needle drop a bit. The goal now is to make the EGT needle drop a bit... around 20º degrees or what is specified in the performances tables.
However, we have two options. We can reduce the temperurate enriching the mixture, we move the red lever forward or we can reduce the temperature leaning the mixture, we have move the red lever, rearward. The goal here is, after reaching the peak, cooling a bit the temperature, making the peak drop in the number of degrees indicated in the performances tables, and we can make the peak drop by enriching (moving the red levers forward) or by leaning (moving the red levers backwards) the mixture.
That is in essence, the EGT peak.
However, I would need to know which differences do we find in the ITT versus the EGT.
I'm wondering if ITT is the same as EGT in an operational mode?
I mean, I am not interested right now about mechanical things, such as were is the thermometer located or stuff like that.
What I need to know is how do I operate the ITT? Do I need to find a the peak in the ITT such as in the EGT?
And then dropping the temperature?
If you could help me with this, I'd be grateful.
Cheers