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Guest panzerschiffe

To all aircraft designers, Why???

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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 to 37,000ft (with allot of Payware/Freeware aircraft) if you can reach it. CaptianSim's 727 will barley make 35,000ft but will not gain anymore speed past Mach .61. I would think once you've struggled to altitude you should be able to gain speed again once you level off. 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...

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Made some edits and ran out of time.....Continuing from above, people will find this with more than a few of their jets:Let's say your at Mach .78 at 31,000 in an airliner and want to climb to 37,000ft. You could easly expect to see your speed drop criticly with an 1800 rate of assent (and with some aircraft a setting of 800 would be too much to handle) if you can reach that altitude at all. CaptianSim's 727 will barley make 35,000ft but will not gain anymore speed past Mach .61 (if that) once at that altitude. I would think once you've struggled to altitude you should be able to gain optimal cruising speed 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.

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Step climb, fuel load, density altitude, indicated vs true, vs ground speed. Have you taken all these factors into account? With most of these simulated aircraft being around for quite a long time now------------- these new "discoveries" would have been a hot potato, but I don't remember the massive complaints.Without getting into exact ceilings, you can't just expect to pickup speed while flying level at an altitude you've struggled to get to. It's a tradeoff, as the engines power is required to maintain that altitude with air being less dense. The plane will keep slowing down unless you lower the nose. Otherwise you could techincally keep step climbing until reaching "airless" space, and that doesn't happen without extra power.L.Adamson

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I figured someone would respond with the points you just made L.Adamson, that's why my post was so long trying to explain. The point I'm trying to make in a nutshell is most FS aircraft aren't designed to be flown much past 31,000 feet. It doesn't matter what the real aircraft in question's maximum surface ceiling is. I don't think designers have taken surface ceilings into account untile very recently...

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One thing I should note about my suggestion in the ES forums.... I didn't make the adjustment based on climb performance. I made it on cruise performance. I usually will configure the aircraft at a set speed--whatever it's cruise speed is supposed to be at a given thrust level. Only then will I adjust the parameter I mentioned.I doubt (and anyone, correct me if I am wrong) that any jet can climb at 1800 fpm at such high altitudes. The 737NG, 757 and 767 all have 41,000+ ceilings. But older jets have lower ceilings, and as pointed out, step climbing is often the only way to achieve them under load. Bizjets have higher ceilings, but I've no clue what climb performance should be on an average load in the flight levels.Still, most real flights I take, the aircraft is at FL350 within 30 minutes of takeoff--and one 767 made it to FL410 in roughly the same amount of time--I also videotaped that flight many years ago, as it was my first experience with a 767 :) In that case, the aircraft had an average climb of about 1300 fpm to reach cruise.... And it's pax load was about average as well, and fuel load was fairly high, as we were on a Transcon flight...Alas, it was also a TWA jet.... Sad that livery only exists in the simming world now :(

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I think the term you are looking for is "service" ceiling, rather than "surface". This is by definition the altitude at which the climb rate decreases to 300 fpm.While I haven't tried the Capt Sim 727, I have tried a lot of the other payware and freeware jets and I have not noticed the phenomenon you are describing. If anything, I find their climb performance a bit too good (well perhaps with the exception of the airbus products). Perhaps your performance expectations are a bit optimistic. Now, if you say you are requiring 100%N1 or more to maintain cruise mach then you may have a point. From my own RW experience, most newer jets would be doing well to give you 1000 fpm at FL300, with the fpm decreasing as you climb (depending on wt, alt, temp, etc). The older jets would likely be climbing at 500 fpm or less. If you are expecting to see an 1800 fpm climb at cruise MN above FL300 then yes, you will be disappointed. As you approach the service ceiling for that weight, temp, etc the climb rate will be decreasing towards 300 fpm.Kevin in CYOW

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Oops,Service, surface, I was typing fast and didn't realize the error.

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I guess I don't understand why you are blaming the aircraft. I routinely fly my 757 at 39,000 ft and my MD82 at 37,000. I've had 737NGs up to 41,000 ft. I haven't seen the problem you're describing ever in FS2000 or FS2002 with freeware or payware a/c. I've flown the Flight1 Iron Knuckles DC9 at 35,0000 ft routinely as well as Ariane's 737-300 at 37,000 ft. I set my climb rate down to 1,000 fpm over 30,000 ft. (2,000 fpm up to 20,000 ft, then subtract 1,000 fpm for each 1,000 ft of altitude up to 30,000 ft.) I don't understand why you would have to edit anything on the aircraft.Steve :-wave

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Some aircraft do have problems maintaining even modest climb rates in the Flight Levels... (BTW, your rule of thumb is exactly what I use, althought I believe you meant "Subtract 100fpm)....In the ES Premier's case, it struggled to maintain 420 KTAS at FL350....not in climb, but in cruise. Easy fix.But, I think sim pilots often get themselves into trouble. They try to maintain that 2000 fpm climb rate all the way to FL370, and the speed starts bleeding off, then it becomes a vicious cycle. It's a must to lower the climb rate as one starts hitting the flight levels. I've never had a problem with most aircraft getting them to cruise altitude and keeping them there.

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I don't have any experience with payware heavies so I can't comment except to say I would be dissapointed if there were performance probs above FL300 in the DF 737 for instance.However, I have run across freeware heavies that do have a big prob "out of the box" at > FL300. I've spent alot of time tweeking FDE's (for learning and fun purposes) trying to get better performance/handling/autopilot reaction from some of the better known craft available.I have succeeded with a couple, still wroking on some others.One notable heavy (I don't want to mention any names, beggars should not be too critical), can't even maintain altitude at FL310 with full power - forget climbing higher. Fine looking craft - not much fun to fly tho.I think for the most part, FDE creators try to get ground handling, takeoff, climb-out, descent and approach done well; but just don't spend much time on high altitude cruise/climb.-hoo

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First, there are many different ways to tune FS jets, and many are tuned with a combination of parameters. The inlet parameters is (in FS) inter-acting with many other parameters and does not at all reflect the aircraft capability by itself.Often, setting "correct" inlet values actually leads to problems in other areas.Secondly, if anything, many FS aircraft are actually too EASY to climb to high altitudes. Many corporate jets are only capable of climbing to their ceiling height after quite a lot fuel burn, and therefore at much lower total weight. Even then towards the last part of the climb, progress will be very slow indeed. With some jets, if the airspeed is allowed to decay through climbing with an excessive vertical rate, the aircraft gets "behind" the drag curve and cannot climb at all until the high angle of attack and commmensurate drag are reduced through levelling off and re-establishing a higher airspeed/mach number. The air is very thin at 40,000 feet.Rob Young - RealAir Simulationswww.realairsimulations.com

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Oops. :-doh I meant subtract 100 fpm for every 1,000 ft above 20,000. Sorry 'bout that. :-lol Steve

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Thanks all, I guess there was some things I didn't understand about high altitude flight....

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It's not easy to make an aircraft perform as it should at low altitudes and then perform just as accurately at high altitudes. Aircraft tuned for high altitude flight likewise may perform out of spec at lower altitudes. On my aircraft I've tuned it that after the initial climb, you pretty much maintain 1800 fpm all the way up to 23-25,000 feet (gradually lowering the VS from there). Engines maintain about 93%-95% all throughout this phase. Seems about right, though I'll no doubt get complaints that my aircraft isn't powerful enough.

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