Greetings, This post is to seek a better understanding of FSX Aircraft FDE parameters rather than lodge a complaint of why aircraft performance doesn't match real world performnace per POH specifications. While many have gone to extraordinary lengths to simulate the real world in FSX,there are understandable limits from the dynamics of the real world. That said, I have a specific question regarding cruise performance of the RealAir Duke, Carenado Cessna 340A and real world POH specs. I notice both aircraft lag about 20 knots below IAS & TAS from expected POH cruise values. Almost the sane examples are prevalent with the Carenado C340A. I use the ASE weather engine if that is related to the issue. Here's an example with the magnificent RealAir Duke:RA DUKE FSX: FL 200, MP 30 IN, 2500 RPM, FF 119 PPH/PER ENG, OAT -39, IAS 146, TAS 191. B60 POH: FL200, MP 30 IN, 2500 RPM, FF 122 PPH/PER ENG, OAT -40, IAS 163, TAS 214. Any ideas and comments are welcomed.

Probably has to do with the turbocharging and the fact that FSX doesn't really model it. In FSX you have to lean the mixture way out as you climb up.

Presumably he did have the mixture set correctly since his fuel flow was pretty close to what it should be. I think the problem may be more related to the weather engine. I'm using AS6.5 and I noticed that sometimes the air pressure or vertical air movements force the plane to have a nose-up attitude for most of the cruise. This means the airspeed is going to be lower than expected since you have a high AOA. The pitch on the attitude indicator would read about 5 degrees nose-up. The autopilot has to maintain this pitch to keep assigned altitude. I'm not sure if that is the problem in your case though.Al

Greetings, This post is to seek a better understanding of FSX Aircraft FDE parameters ........RA DUKE FSX: FL 200, MP 30 IN, 2500 RPM, FF 119 PPH/PER ENG, OAT -39, IAS 146, TAS 191. B60 POH: FL200, MP 30 IN, 2500 RPM, FF 122 PPH/PER ENG, OAT -40, IAS 163, TAS 214. Any ideas and comments are welcomed.

I've noted the same for the C172 (which I fly in RW), and assume it's difficult to bring together enough parameters to track the real performance over a range of altitudes, temperatures, etc. I have the utmost respect for all aircraft designers so this is not a critique on them but rather an assumption that FSX has limits- which I understand for a $70 application. What I have done at times is to make my own perf tables based on various altitudes and RPM's, which replicate the POH ones for the real a/c. I do this because I like to be able to fly IFR in FSX and be able to correctly (or as correctly as I can in RW, with weather variables being the unknown) plan a flight, in as much as is required by the FAA if I'm not in radar contact (which is what you need to assume, being worst case). That being said, however, I'm often surprised just how correct that FSX stock C172S is to RW performance.Thanks, Bruce.

Greetings, This post is to seek a better understanding of FSX Aircraft FDE parameters rather than lodge a complaint of why aircraft performance doesn't match real world performnace per POH specifications. While many have gone to extraordinary lengths to simulate the real world in FSX,there are understandable limits from the dynamics of the real world. That said, I have a specific question regarding cruise performance of the RealAir Duke, Carenado Cessna 340A and real world POH specs. I notice both aircraft lag about 20 knots below IAS & TAS from expected POH cruise values. Almost the sane examples are prevalent with the Carenado C340A. I use the ASE weather engine if that is related to the issue. Here's an example with the magnificent RealAir Duke:RA DUKE FSX: FL 200, MP 30 IN, 2500 RPM, FF 119 PPH/PER ENG, OAT -39, IAS 146, TAS 191. B60 POH: FL200, MP 30 IN, 2500 RPM, FF 122 PPH/PER ENG, OAT -40, IAS 163, TAS 214. Any ideas and comments are welcomed.

Assuming they have their actual fuel burn rate correct, I'd hazard that the engine is not generating the correct level of thrust at altitude.