So you designed and built sims on a scale that CAE does, a world leader in this technology. . Why do I find that really hard to believe?

I personally don't build the entire thing of course but I do design the simulation software. Are you calling me a liar Bob?

Interesting discussion. But I haven't heard any discussion of the idle thrust of the engines in the actual aircraft, which also contributes to the descent performance at idle. That is also a variable depending on manufacturer.

Kevin and Bob,

 

From what I understand, Boeing collects Test data from at least the first four aircraft that are in the Test flight program to get the performance data that is published to provide a more accurate picture of what expected performance should be for a production aircraft. While there may not be large differences in the aircraft they aren't exactly the same obviously. I don't think it's presented as multiple packages but an average of the test data that is released.

Hi Paul

 

Indeed. Though I don't think several test aircraft all fly the same data points. Several aircraft are used to cover all the data points.

 

The released data package is based on the original predicted (theoretical) aerodynamic model and adjusted to match actual test aircraft measurements.

 

There is one data package for each type and variant. However the 767-400ER which Bob referred to might have been a special case in terms of how Boeing flight tested the differences to the base 767 model.

Interesting discussion. But I haven't heard any discussion of the idle thrust of the engines in the actual aircraft, which also contributes to the descent performance at idle. That is also a variable depending on manufacturer.

The same principle applies. The aircraft manufacturer will usually have an engine model from the engine manufacturer in their simulation model which they provide to sim manufacturers.

 

It only becomes an issue in FSX because the FSX engine model doesn't account for things like flight idle.

I personally don't build the entire thing of course but I do design the simulation software. Are you calling me a liar Bob?

 

I am stating that I spent a great deal of time learning about flight sims and how they  are designed by some of the largest flight sim manufacturers in the world , starting with CAE, Boeing, L3 and others, since my job involved interfacing with these companies and even training some of their workers. I am trying to explain how this is done in the case of CAE, and you are implying that I don't know what I am talking about.  

Kevin,

 

Yes, there is a baseline data set for each aircraft type, and the baseline data set is based on one, individual tail, but for $ you can customise to an elected tail. You can also pay $ to have the various 'options' data sets made available to you.

 

Kevin and Bob,

 

From what I understand,  Boeing collects Test data from at least the first four aircraft that are in the Test flight program to get the performance data that is published to provide a more accurate picture of what expected performance should be for a production aircraft.   While there may not be large differences in the aircraft they aren't exactly the same obviously.  I don't think it's presented as multiple packages but an average of the test data that is released.

This post practically says it all!

 

 

Yes, there is a baseline data set for each aircraft type, and the baseline data set is based on one, individual tail, but for $ you can customise to an elected tail. You can also pay $ to have the various 'options' data sets made available to you.

Certainly, but tail number data doesn't extend to changes to the aero data. It relates to specific aircraft configuration.

The same principle applies. The aircraft manufacturer will usually have an engine model from the engine manufacturer in their simulation model which they provide to sim manufacturers.

 

It only becomes an issue in FSX because the FSX engine model doesn't account for things like flight idle.

Well, I'm sure you are an expert in sim modeling and I am not, but I dabble. On your point about FSX not modeling flight idle thrust, if you go look at some representative .air files for transport type aircraft you will see that there is non-zero thrust at low N1 throughout the aircraft speed profile. Why is that not idle thrust?

Well, I'm sure you are an expert in sim modeling and I am not, but I dabble. On your point about FSX not modeling flight idle thrust, if you go look at some representative .air files for transport type aircraft you will see that there is non-zero thrust at low N1 throughout the aircraft speed profile. Why is that not idle thrust?

 

Research the difference between flight and ground idle.

 

Full names in the forum, please - first and last.

I am stating that I spent a great deal of time learning about flight sims and how they  are designed by some of the largest flight sim manufacturers in the world , starting with CAE, Boeing, L3 and others, since my job involved interfacing with these companies and even training some of their workers. I am trying to explain how this is done in the case of CAE, and you are implying that I don't know what I am talking about.  

Bob,

 

CAE don't do that any differently to any other sim manufacturer. The data available to them from Boeing is the same as that available to any customer. You may have spent time learning how flight sims are designed. I have spent my entire career actually designing and building them and getting them qualified by the FAA, CAA, etc. I've dealt directly with the Boeing data department (also Airbus, Fokker, etc) on a number of projects.

 

With respect, I didn't say you didn't know what you were talking about, I said the process you related about obtaining data from Boeing was not typical. I even conceded that the 747-400ER sims you mentioned might have been a special case, being a rather rare bird. You, on the other hand, said you found it hard to believe what I said was true and haven't retracted that comment.

Well, I'm sure you are an expert in sim modeling and I am not, but I dabble. On your point about FSX not modeling flight idle thrust, if you go look at some representative .air files for transport type aircraft you will see that there is non-zero thrust at low N1 throughout the aircraft speed profile. Why is that not idle thrust?

As Kyle hinted, what I meant was FSX doesn't model different idle settings. There's nothing in the AIR file which allows for a lower idle setting on ground, or multiple idle setting in flight.

Bob,

 

CAE don't do that any differently to any other sim manufacturer. The data available to them from Boeing is the same as that available to any customer. You may have spent time learning how flight sims are designed. I have spent my entire career actually designing and building them and getting them qualified by the FAA, CAA, etc. I've dealt directly with the Boeing data department (also Airbus, Fokker, etc) on a number of projects.

 

With respect, I didn't say you didn't know what you were talking about, I said the process you related about obtaining data from Boeing was not typical. I even conceded that the 747-400ER sims you mentioned might have been a special case, being a rather rare bird. You, on the other hand, said you found it hard to believe what I said was true and haven't retracted that comment.

As Kyle hinted, what I meant was FSX doesn't model different idle settings. There's nothing in the AIR file which allows for a lower idle setting on ground, or multiple idle setting in flight.

I understand the differences between ground and flight idle. The question on the floor is FSX modeling. That question is that since the .air file will provide different thrust settings as a function of aircraft speed and N1 setting, why is that not a reasonable (assuming the .air file developer put some thought into it) model for flight idle and ground idle? There are typically values of thrust for N1~20% and o.o Mach?

 

Rick Messier

I understand the differences between ground and flight idle. The question on the floor is FSX modeling. That question is that since the .air file will provide different thrust settings as a function of aircraft speed and N1 setting, why is that not a reasonable (assuming the .air file developer put some thought into it) model for flight idle and ground idle? There are typically values of thrust for N1~20% and o.o Mach?

 

Rick Messier

The problem with trying to do it that way is you can't control the switch from ground idle to flight idle and approach idle. Done through the air file it all depends on Mach No.