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Post by Tom Goodrick on Oct 15, 2009 18:54:59 GMT -5
I have a vague memory from many years ago that we found that the static thrust setting in the aircraft.cfg file was irrelevent. I had forgotten that and had elevated that thrust setting to a high level. What were your reults in comparison with the setting in the aircraft.cfg file?
What was your estimate for the inlet area on the Williams engine and which engine was that? I know there are two but there may be more. My books are too old to show this stuff.
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Post by Tom Goodrick on Oct 16, 2009 9:13:27 GMT -5
I did some tests. The static thrust setting in the aircraft.cfg file does play an important part in setting up the engine for proper performance. I put a thrust gauge on the panel in place of the thrust/weight gauge I had been using. It showed a low thrust at idle and the proper rated thrust during full-throttle takeoff from the runway at 625 ft msl (KHSV). That is good enough for me. When I set the static thrust from 1695 lbs to 10,000 lbs, the idle thrust jumped up accordingly. That's good enough for me.
I think now that my memory was of the horsepower setting for piston engines which we found to be meaningless several years ago. However, I still set it properly.
On the Emb 100, I am now adjusting drag and inlet area to get both realistic climb and realistic cruise. The area of 3.25 sq ft left insufficient power at high altitude and high throttle settings. Rate of climb at low altitude was too high. I am trying 3.00 sq ft and more drag to reduce low-altitude climb rate. I am hoping the thrust at high altitude using higher throttle settings will give the proper cruise speed and fuel flow (after scalar adjustment. My time to climb and total fuel to climb are now pretty close to the real values.
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Post by Bill Von Sennet on Oct 16, 2009 12:29:40 GMT -5
I have been holding off on the Phenom 100, waiting to see if you can get the FD's corrected. Sounds like you are almost there, so I downloaded the aircraft.
When you are ready, please send me the .air and .cfg files.
I think their panel is a joke, so I will be using your panel from the Eclipse 500.
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Post by Allen Peterson on Oct 16, 2009 14:08:24 GMT -5
The fan diameters that I used are: GE Honda HF120 - 15.8" Williams FJ33-4A - 17.3" P&W PW610F - 14.5" With the above inlet areas and the thrust set to the specified value in the .cfg file, the thrust was within +/- 15%, as I remember. I adjusted the thrust_scalar accordingly. For the Phenom 100: P&W PW617F 17.6" (web site below) www.pwc.ca/en/engines/pw617f-eHope this helps.
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Post by Allen Peterson on Oct 16, 2009 18:49:28 GMT -5
I downloaded the Phenom 100 from FltSim, corrected the wing area, span, etc, in the .cfg file. I set the inlet_area to 1.689, the static_thrust to 1695 and the thrust_scalar to 0.9. I'm using your Eclipse 500 panel. After take-off (at about 60% to keep the temp. under 800*) and climb to 30,000 feet I'm getting 360 kts GPS GS with 66% throttle. So I must be doing something wrong since your results are different. I'll wait for your FDs. I haven't tried to land it yet.
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Post by Tom Goodrick on Oct 16, 2009 21:01:08 GMT -5
I wrote a reply and lost it as i was tossed off this Forum, probably because of a pop up for Flash which i don't have on this computer.
I am almost through fixing up the FD's. Allen, you are close. But there are many things here.
I'll send out FD's some time tomorrow. Test results are good.
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Post by Tom Goodrick on Oct 17, 2009 11:06:19 GMT -5
I sent you guys a copy of the latest FD.
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Post by Bill Von Sennet on Oct 17, 2009 14:40:58 GMT -5
Thanks Tom
I flew KLWB-KPWK (Lewisburg WV - Chicago IL) twice.
1st time at FL240 106 min 213 gal
2nd time at FL380 92 min 170 gal
The climb from FL240 to FL380 was pretty slow while maintaining 200 kias
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Post by Tom Goodrick on Oct 17, 2009 14:57:14 GMT -5
I just climbed from HSV at 630 ft msl to 40,000 ft in 35 minutes and 143 nm burning 115 gallons. In another 20 minutes, I was in steady cruise at 371 KTAS with an endurance of 3.02 hours. That indicates an IFR range of 1106 nm. (My position at 55 minutes was 264 nm from HSV and I had 272 gallons remaining.) My payload are three 180 lb passengers, no baggage and I started with full fuel at max gross weight. As a guide I use a flight plan to Marquette, Michigan which is due north. (My heading was 359 deg.) I'll try it again with Fair Weather (this was in Clear Wx) to see the effect of a light cross wind and non-standard temperature. I'll publish a table of performance in a few hours. I recorded data every 2.5 minutes.
This aircraft now has a fair amount of practicality. Later I'll compare it to a CitationJet. The CitationJet has the same number of seats and weighs about the same.
I thought of one improvement that we should make in the weight distribution after looking at the photo of the plane with the loading vehicles. The aft baggage should be moved farther back. That will move back the most-forward CG at nax cabin load where 212 lbs is placed in the aft baggage area. I'll try to estimate its proper position.
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Post by Bill Von Sennet on Oct 17, 2009 15:39:14 GMT -5
I flew the KLWB-KPWK flight again with the Beech King Air C90B_XP at FL240
109 min 140 gal
Weather was the same RWX for all three flights, but at FL380 the headwinds where about 20 knots stronger.
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Post by Tom Goodrick on Oct 17, 2009 19:52:14 GMT -5
The long time to altitude was noted by each of the reviewing pilots in the magazines - J. Mac McClellan in FLYING and Thomas A. Horne in AOPA Pilot. J Mac remarked that it took 25 minutes to get to FL300 and 34 min to get level at FL350. where he saw 360 KTAS and 704 pph (352 pph/e) after it became steady. Horne reported a climb rate of 350 fpm at FL340 and a time of 34 min to level at FL350. Horne reported 352 KTAS at FL350 and 335 pph/e. Both reporters remarked that temperatures 15 degrees above standard caused poor than expected performance.
Here are the data for a climb I made today to FL400 in Clear Wx with 3x180 lbs in the cabin and full fuel at start of taxi at HSV. I flew a north track aiming toward Mraquette, Michigan to get distance info.
TIME___ALTITUDE__KIAS___FPM___THR%__PPH/E__F GAL___DIST NM _0.00______630_____0_______0_______0_____205____418_________0 _2.51_____4970_____193____1500_____60____699____392________-6 _5.01_____8930_____201____1500_____63____716____382_________2 _7.53____12900_____194____1500_____65____666____372________12 10.00____16770_____204____1500_____70____676____363________22 12.50____20640_____198____1500_____76____666____355________34 15.00____24540_____192____1500_____84____604____346________46 17.50____28060_____181____1200_____95____545____339________57 20.03____30760_____179____1000_____95____482____332________70 22.50____33020_____174_____800_____95____435____327________82 25.01____35060_____165_____800_____95____396____321________95 27.51____36640_____159_____600_____95____369____316________107 30.00____38140_____149_____600_____95____345____312________119 32.50____39200_____145_____400_____95____328____307________131 35.00____40000_____144_____400_____95____316____303________143 __________________________KTAS___________________________ 40.00____40000_____175_____339_____95____309____295________170 45.00____40000_____190_____365_____90____306____287________201 55.00____40000_____194_____371_____90____302____272________264 At 55 min endurance = 3.02 hrs. IFR range = 371*(3.02-0.75)+264 = 1106 nm
This performance is a little better than reported in the magazines. The range is close to 1178 nm at FL330 given as an Embraer spec.
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Post by Allen Peterson on Oct 17, 2009 20:02:54 GMT -5
Great job, Tom, thanks. I flew from KSEA to KCOE at FL300 in 59 minutes and used 154 gal. I flew using your checklist and AP and Auto Throttle except for the landing itself. This is my first jet flight "by the numbers", and I'm impressed. The last flight I made was in the Fokker FII. What a difference!
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Post by Tom Goodrick on Oct 18, 2009 10:51:56 GMT -5
I checked the weight distribution some more and decided the aft baggage positio is about where it should be.
There is a considerable CG shift from normal loads to flying solo. Be sure to get in some practice at both. A typical operation involves some solo flight. You go to an airport within 100 nm, pick up passengers, take them a few hundred miles and fly back to your home base solo. You may want 60 lbs in the nose baggage for such operations. (An overnight bag and a can of kitty litter would do.)
I sent you all a set of V gauges for your panels that are set for the Emb 100.
The range of V2 (takeoff speed) varies from 104 KIAS to 122 KIAS.
The range of Vref (final approach speed with full flaps) varies from 90 KIAS to 102 KIAS.
Weight___V2 kias 10472____122 MTOW CG <20% 9912_____118 3 pax 80% fuel 9351_____115 8790_____111 8231_____108 3 pax 20% fuel 7685_____104 Solo 20% fuel CG >30%
Weight____Vref kias 9766______102 MLW 3 pax, 75% fuel, CG <20% 9349______100 8930_______98 8570_______96 8091_______93 3 pax, 15% fuel 7544_______90 solo, 15% fuel CG>30%
About half your takeoffs and landings will use the upper values but half will use the bottom values in each chart - flying back to home base or flying to a nearby airport that has jet fuel.
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Post by hanspetter on Oct 25, 2009 5:41:21 GMT -5
The jet flies nicely but I'll have to soften the nose gear spring loading. I've tried airports all over the world and various fuel loads -- it starts bumping the moment the nose wheel touches down and crashes if I brake.
If nobody else experiences this it's probably a question of scenery meshes that affect the invisible roughness of runways.
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Post by Tom Goodrick on Oct 25, 2009 9:39:38 GMT -5
Yes, the gear has been troublesome to many of us. I made an adjustment between the first and second versions (the latest is the third, which you all have now) that stiffened the nose gear but added damping. Bill's solution is to increase the stroke from 0.12 to 0.20 ft. I agree with that and will make the same change in mine. (0.2 was an original value.) Here's the line:
point.0=1, -15.00, 0.00, -4.3, 2500.1, 0, 0.6349, 46.8, 0.1200, 2.5, 0.8600, 10.0, 10.0, 0, 260.0, 260.0
which shows this value at 0.1200. The changes I had made from the original were the z values of all wheels (which can still be improved if you want to take the time to set the wheels closer to the ground under 1 g loading), the failure limit in fpm of 2500, the deflection at 2.5g (0.1200 ft) and the damping ratio of 0.86.
The z value has nothing to do with the dynamics, just the picture. The limiting vertical rate of 2500 fpm is something I do in most cases. 1500 is the normal setting but I have bumps in the runway at KHSV that will break that during takeoff. The 2.5g deflection of the gear (no relation to tire diameter) combines with the deflection with the standard assumption of 2.5 g dynamic load to set mainly the spring constant of the gear. You will see the 2.5 load/weight ratio in most gear data. That is simply a standard that applies to the minimal bounce. If an object with a linear spring is raised to a point where the spring is exactly undeflected and then dropped, the spring will deflect to support a 2.0 g load. That's according to Mecahnical Engineering or Physics theory. The extra 0.5 is added to handle minor contingencies. Of course some of our landings place a much greater load. This is not the max load for the spring. (The notes in some aircraft files are wrong about that.) It is merely a standard by which the spring constant is set according to the deflection given. Increasing this value will do two things. It allows the nose to dip lower during braking and it tends to make the gear absorb more energy during the deflection observed. The damping ratio (0.86 in this case) determines how much of the energy in the gear stroke is dissipated rather than just absorbed. If not dissipated, the energy in a gear stroke can cause a rebound and a bounce. The damping ratio also determines the force at initial contact which is the damping value applied directly to the vertical rate of the wheel because there is zero deflection to generate a force.
The damping ratio is a ratio of the actual damping to the damping that would be needed for "critical" damping. Critical damping is a value that brings deflection to zero with 100% of the energy dissipated.
I will try 0.2 ft deflection or more and see how it goes at Houston (KHOU 30L). 0.12 worked fairly well.
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