To DreamFleet and other aircraft designers...

[Leo112]

[font size="1" color="#FF0000"]LAST EDITED ON Jun-03-03 AT 10:41AM (EDT)[/font][p]This message is for anyone who designs jet aircraft,

This has been an issue for me for some time. Most aircraft I've flown in Flight Simulator over the past years (FS5 to FS2002) have a maximum surface ceiling of at least 37,000 to 41,000 feet (737,727,A320,757,Corporate, etc). When flying these birds such as CaptainSim's 727 or FFX's 737, I can barely reach 31,000 feet. It wasn't until I ran across this with Eaglesoft's new Premier Business Jet that me with JohnCI's help discovered that certain features in the 'aircraft.cfg' were set unrealistically. This is one example of wrong 'Inlet Area' settings. This is what John discovered:

"Climb performance, especially in the higher altitudes, can really suffer if the inlet area of the engine is too high in the aircraft.cfg. I noticed that I was running at almost 100pct thrust just to maintain 420KTAS at altitude. So I edited my inlet area while in cruise, finally settling on a value of 1.8 (vs. the original value of 2.5)."

"This value can be adjusted in the "TurbineEngineData" section of the aircraft.cfg. As I said, the fuel flow scalar may need adjustment to compensate. There are other ways to do this, but they involve messing with the drag, which has its own set of issues. Without being a Premier "expert", I don't like juggling too many values-I'd rather have it fly right, vs. flying the way I "think" it should."

Why are so many Freeware and Payware developers setting this or other settings wrong forcing us to have a hard time climbing past 31,000 Feet? I'll almost have to say this happens with 95% of the available aircraft on the market. Only the developers that have been lately designing Corporate Jets have took pains to make sure their designs get to at least 40,000 feet (if they didn't do this most users would complain knowing the jet should be able to fly past 32,000ft).

I pose this question to all Freeware and Payware designers (from Dreamfleet to PSS to CaptainSim to Mike Stone) because I can't understand why and how widespread of a problem this is. Passenger Jet liners commonly cruise in the mid 30,000 foot range (32,000 to 38,000) while Corporate Jet's cruise in the mid to lower 40,000ft range. Why don't we see this in FS2002??? I know some will say you have to step climb which is not possible with FS2k2's default ATC, but what I've seen is once your past 32,000ft, you barely have enough thrust to maintain a 800 foot rate of climb without losing criticle speed for every 100 foot gain (forget the standard 1800 climb rate). So let's say your at Mach .78 at 31,000, you could easly expect to see your speed drop criticly with a 1800 rate of assent (with some aircraft 800) to 37,000ft (with allot of Payware/Freeware aircraft) if you can reach that altitude. CaptianSim's 727 will barley make 35,000ft but will not gain anymore speed past Mach .61 once at that altitude. I would think once you've struggled to altitude you should be able to gain speed again once you level off but with some aircraft altitude is such a problem that they can't maintain speed (well under their prescribed surface ceiling. Not all aircraft have this problem but a great majority do, and what's sad is some of them we pay for like PSS's A320. With FS2k4 around the corner it would be nice to see this get addressed. In FS2k4 the higher you go the darker it gets making high altitude flights allot more interesting than it is today.



Thanks for any replies that helps me understand what's going on in FS aircraft design...

[ladamson]

[font size="1" color="#FF0000"]LAST EDITED ON Jun-03-03 AT 10:31AM (EDT)[/font][p][font size="1" color="#FF0000"]LAST EDITED ON Jun-03-03 AT 10:29 AM (EDT)[/font]

Maybe you're not using "step climbing" proceedures when required. All jet's can't substain a constant climb rate, which also varies with load.

edit---- one other item. When comparing airspeeds at altitude, are you comparing against actual true ground speeds (no wind --gps), since "indicated" is much less at high altitudes. Generally, simulated aircraft producers such as Dreamfleet have figured all this out..

edit again-------- did you throw "step climb" in your edit? I didn't see it the first time around.. :)

Ladamson

[Lou_Betti]

Indeed, Larry.

It has little or nothing to do with FS aircraft design, but much to do with FS piloting skills and expectations. Our flight dynamics experts (Steve Small and Ron Freimuth) are among the best in the business. They know what they're doing.

I have no problem getting our 737 to it's ceiling of 37,000', I just do not try to do it at gross weight, and at 1800 fpm all the way up! ;-)

Now, to compare a biz jet to a jet airliner, well, that proves my point. One would be essentially comparing apples to oranges.

Example, did you know that a Grumman Gulfstream has the same basic engines that are used on a Fokker F-100 airliner? Imagine, a 15 seat biz jet with the same power as a 100 seat airliner.

Comparing biz jets to large airliners is a bit of a stretch, to say the least!

Regards,
[link:www.dreamfleet2000.com|http://www.dreamfleet2000.com/gfx/im...FORUM_LOU.gif]

[Trev]

Above about Flight Level 300 you should flying on Mach numbers. B737 should be doing about Mach .82 at that altitude. Converted to IAS that would be about 310 or so Knots. Any faster and the overspeed alarm would probibly sound. I have had the Falcon Biz jet up to F/L 410.

Trevor:)



http://users.actrix.co.nz/trevw/new_zeaC.gif
New Zealand

[Erick_Cantu]

Yeah, and it would help if people read the readme. Like our 737-800, as mentioned above - with a full fuel load, it won't fly right. We can tell when people post screenshots whether they're using a reasonable load or not since we programmed in moveable trim. Step climb if you have a lot of gas. If you have a lot, it won't climb. I didn't have any problems hetting my -800 or your -400 or CS's 727 anywhere above 31,000 or through 37,000.

Also, people assume that because an airliner has a service ceiling of 41,000 that it always flies at 41,000. It won't. The 737-800 is certiifed up to 41,000 feet - but you'll usually find yourself cruising much, much lower.

-E

[font size=1]

One last thing before I quit!
I never wanted any more than
I could fit into my head!
I still remember every single word you said,
and all the sh*t
that somehow came along with it!
Still, there's one thing that comforts me
since I was always caged and now I'm free
Don't wanna be your monkey wrench
One more indecent accident
I'd rather leave than suffer this
I'll never be your monkey wrench
Don't wanna be your monkey wrench
Don't wanna be your monkey wrench
Don't wanna be your monkey wrench
Don't wanna be your monkey wrench

[/font]