Forum: General F-22A Raptor forum

I don't buy the whole PAK-FA advantage over an F-22. If its anything like previous intelligence blunders (MiG-25 Foxbat turning performance?). It's likely the PAK-FA is heavier, and has less maneuverability than the F-22.

Wasn't it Jon Beasley(test pilot from Lockheed) who criticized the Su-30 demonstration as being good for an air show, not so good in an actual dogfight. The likely hood is that the T-50 wont be significantly better than the Su-30MKI in maneuverability. I'm going to rewatch some of the Su-30MKI dogfight videos.

On CFD, I'd gladly do it if someone provided me with a model and $3,000 to buy the new computer I was looking at. Being serious though, trying to get a full flight envelope for a plane using CFD on one computer could be as time consuming as actually flying the plane to generate the envelope. Without (or maybe even with) serious hardware, the time it takes you to run CFD on the plane in some cruise state could be enough to get the real think to take off, do a bunch of maneuvers, and land. And as has been stated, high AoA and transonic flight can be very difficult to do. Those subjects are tricky even off the computer.

http://www.youtube.com/watch?v=cenIBqda8zA

According to that video, every sub second time step of simulation took 20 seconds of real time.

Your scale model will of course have scaled aero-servo-elastic properties, mass properties, flexibility effects, flight control system, propulsion system, and a data recording system with hundreds of sensors to provide the necessary data to do performance analysis. In addition to correcting for Reynolds number, you will be able to simulate pressure distribution differences due to Mach numbers up to at least 2.0, right?

Your scale model will of course have scaled aero-servo-elastic properties, mass properties, flexibility effects, flight control system, propulsion system, and a data recording system with hundreds of sensors to provide the necessary data to do performance analysis. In addition to correcting for Reynolds number, you will be able to simulate pressure distribution differences due to Mach numbers up to at least 2.0, right?

johnwill, respectfully I did say subsonic didn't I?

They used scale F/A-18Es during testing. These were not toy jets but professionally built flight test articles. They use hydraulic-electric actuators, not RC servos. Jet powered, and for extra credit, a FCS functionally similar to the real thing. At least one is still in use for drag reduction and stores separation testing. The people who fly "models" like this don't fly it because its just a cool toy.

Do you have any comments on the aerodynamics/performance of the T-50 to add to our discussion?

Did you say subsonic? I couldn't find it, but that's just me. Any comment on the rest of the items I mentioned? The F/A-18E model you mentioned is interesting, but irrelevant. Do you have a link to it?

No, I don't have any comments about T-50 performance because I know even less about it than you do.

Your scale model will of course have scaled aero-servo-elastic properties, mass properties, flexibility effects, flight control system, propulsion system, and a data recording system with hundreds of sensors to provide the necessary data to do performance analysis.

Did you say subsonic? I couldn't find it, but that's just me. Any comment on the rest of the items I mentioned?

I think all of that is only backing up his point, trying to do this is complicated and having someone do it for fun is not the same as a company like Lockheed or Boeing doing this as part of aircraft development.

All of that said, I do think that if someone sat down and made a good model of the PAK-FA and/or F-22 (virtual or physical model) and did some testing, there would definitely be some merit in the data obtained. It just wouldn't be conclusive. Probably better than trying to judge things from pictures and stats off Wikipedia though.

Can you measure pitch, roll, and yaw rates and accelerations? Can you measure airspeed, AOA, g, all control surface positions, pilot commands, etc?

I don't want to discourage you or anyone from building a T-50 model, but don't even begin to think it will give you any meaningful results whatsoever.

neurotech,
You are obviously an intelligent person and are probably very good at whatever it is that you do. But seriously, you seem to have little concept of the incredible complexity of physically modeling an airplane. Flexibility is an issue at all g levels, not just high g. An RC "fly by wire" system cannot possibly come anywhere close to modelling a real one, even if you knew the T-50 control laws, which you don't. Can you put enough sensors on that VLJ turbo fan to compute in-flight thrust? Can you measure pitch, roll, and yaw rates and accelerations? Can you measure airspeed, AOA, g, all control surface positions, pilot commands, etc?

And yes, there is one thing you missed, mass properties. Can you model the cg, weight, Ixx, Iyy, and Izz of the T-50?

I don't want to discourage you or anyone from building a T-50 model, but don't even begin to think it will give you any meaningful results whatsoever.

There is a few people around who would actually do something like this "for fun". Some of the pilots I flew with have been known to use a compute cluster to settle discussion points. The response from Boeing engineers was definitely interesting.

Its my personal opinion that somewhat useful data could be obtained by a compute cluster and a 3D model. I fully understand it wouldn't be conclusive. Unless Clint Eastwood steals a T-50, or the Russians release the data, It wouldn't be conclusive.

John - What do these guys think we have a Foreign Technology division for? Reverse engineering crashed UFOs? Stealing Migs from the Ukraine?

I've seen on youtube people flying scale YF-23s... Have they learned any secrets about the YF? Nope. Foolish is as foolish does.