Cruise Performance?

[FLIGHTO 8]

I just hit my 20 hour mark in this a/c and i have yet to see any of the talked about TAS per GPH that the charts claim...As per the charts: I should be getting around roughly 230-240 true at FL270 2000rpm Prop, under 700lbs.ft., all with under 28GPH..I cannot even get close. I am upwards of 36Gph and not acclerating to those true speeds with over 800lbs/ft ?I am interested in the 2000 RPM range only..I have printed the charts from Jetprops site that show 2000RPM at the flight levels.What is everyone getting? I know there might be a limitation to FSX but I was really under the assumption that I would be able to see 250+ true at cruise...I know its comparing apples to oranges but i get 225-230 true from a Cirrus SR22 Turbo at FL250....Thanks

Edited February 20, 2012 by FLIGHTO

[CoolP 283]

I know its comparing apples to oranges but i get 225-230 true from a Cirrus SR22 Turbo at FL250....

Yes it is, sort of. The high performance piston thingies like the Lancair even catch up (or take over) on the Duke's T cruise performance, running two PT6 and their fuel flow.But I see your point. I get some 230-240 TAS out of the JetProp at FL240+, but I think the FF is slightly higher than charted. One would have to note the exact conditions though, especially the ISA deviations, to really start comparing. Here's 233 KTAS at 787 lb torque, 2000 rpm and some -5C ISA. Now I didn't note he FF, but I think it was close to 30. http://imageshack.us.../screen3gd.jpg/Edited. The additional docs feature the -34 engine. The Carenado docs and the model are on the -21. Now don't ask me what exactly the difference on the values will be (ITT limits? 680 to 740C), but I think the rw folks wrote about the -34 being better in the cruise portion.In regard to the Carenado docs, I'd have to test some more. They only offer 2200 rpm charts, but I'm running 2000 in cruise and even climb. On 2200, the torque soon exceeds the P&W limits but I can see some safe 235KTAS at FL210 there. Further up, you get slightly slower but the FF reduces a lot. So you should see some 230 KTAS and 28.4 gph at FL250. As said, I will look and try further on my next flights. It's fun to do. Edited February 21, 2012 by CoolP

[CoolP 283]

Ok, I've flown and tested some stuff. Now the mistake I made was that I was flying rw weather and therefore +x ISA on the one flight and -x ISA on the other one. That's not a good basis to check something. So what I did was to pull her up to FL250 with the clear skies (clears all weather) preset of FSX, which should be the sim's ISA condition.Regarding the speeds and power settings in the Carenado PT6 -21 docs, the plane is spot on. The docs e. g. state some 231 KTAS at 700lb, 2200 rpm and I get some 228 and 229. Now the fuel flow is off in my eyes. Docs say 28.4 and I'm running some 34 or something. So I've used the very rough method of altering the fuel_flow_scalar = 1.4 value in the aircraft.cfg to 1.17 which enables some 28.5 gph in the above conditions.Now I'm stating the rough method for two reasons. First, I've only looked for that one setting, at FL250. Second, I have no idea how FSX handles the change on the full spectrum and I'm also not even close to Bernt Stolle's competence, who's set the higher FF value for a reason.So maybe test the change and report back. As said, the power settings look spot on to me. Only the FF 'needed' a change. For checking some more, I've descended to FL210 and used the Carenado docs again. So that's 800lb, 2200rpm and some 32.2 gph from the docs, whereas the altered FF value gives me some 32.6. Still in pure ISA conditions. Looks ok.Now further down to FL150. Docs say 27.7 with 600 lb, I get 25.0. So you can see that the rough method already shows it's character as the values are too low. Still, the power settings match the charts to 100%.FL120, 800 lb, docs say 34.6 and the tweaked value gives me 32.6.All of the above statements refer to the 1300 Malibu with the optional FDE patch from Bernt installed.If you like to test these things, please make sure to really use the ISA conditions in FSX. As shown, my rw weather based assumptions didn't lead to any usable data.

Edited February 21, 2012 by CoolP

[FLIGHTO 8]

I have noticed the same on the higher flight levels.... FF too high. I will set some testing up also..It put up a flag b/c I was in cruise - FL270, ISA -37, Tailwind of about 6knts, and I was up around FF36 (lil over 800lbsft) to get 230 true... Seems like a lot of fuel burn and questionable range.... On these similar conditions, on a +-450nm trip I am getting about 5.3nm/gal...

[FLIGHTO 8]

It just dawned on me!!!!! Why in the world would Carenado model the dash 21 and not the dash 34 or even the dash 35 to begin with... I think we should all think about a -35 STC(DLX) for this bird.......I could use 270knts true @ FL270...can you?

[CoolP 283]

It put up a flag b/c I was in cruise - FL270, ISA -37, Tailwind of about 6knts,

I think I've used my ISA values differently. I use it to describe the ISA deviation. So I would read your -37 ISA as some '37 degrees lower than ISA temp' while I think you mean you had -37C OAT. At FL270, where ISA says 38.4 or .5, this would be +1.4 ISA.Now please correct me if I'm stating wrong things. :(

Why in the world would Carenado model the dash 21 and not the dash 34 or even the dash 35 to begin with

I don't know, but, as pointed out above, we shouldn't look into the -34 docs but use the Carenado ones which are correctly listing the -21. Now don't ask me about the difference of the engines. I don't think it's SHP, but more of an ITT limit and things.

I could use 270knts true @ FL270...can you?

I can see 264 KTAS in the -34 docs. But, mind the temp scale and the *. That's only possible at ISA -30C. So you would need some -68.5C OAT, which is pretty cold at FL270. The other value looks more realistic and says 256 KTAS at ISA.By the way, I think the Carenado docs state something wrong. They summarize all settings as 2200 rpm ones, but the tables are divided and I really think that the lower part gives you the 2200 rpm settings while the upper one is 2000. The rw docs work the same way and the values then make sense.In the Carenado docs, at FL270 we should max at 236 KTAS, 2200 rpm and some 700 lb on a standard ISA day. Will test that soon. Our JetProp should be fastest at FL230 and FL240 though, from the docs. 240 KTAS at ISA.

[CoolP 283]

Well I've tested this setting

In the Carenado docs, at FL270 we should max at 236 KTAS, 2200 rpm and some 700 lb on a standard ISA day.

and it works. It does not when you just load her and slew her up. But it does when you have some fuel burned. But it still takes a while to establish any 230 values. As Bernt pointed out somewhere else, the rw JetProp factory boys chose very optimistic values on some occasions. E. g. max climb rate at the lowest possible weight of the plane.I'm still running the tweaked FF value of 1.17 and the fuel burn at the above cruise setting is spot on. Means 28.2 in the sim and 28.1 in the charts.

Our JetProp should be fastest at FL230 and FL240 though, from the docs. 240 KTAS at ISA.

I get 236 KTAS at FL230. Again, with some 50% fuel in the tanks. I'd say that's pretty close to charted values. Fuel flow is charted 32.1 and 32.5 in the sim. Edited February 21, 2012 by CoolP

[Lifeguard911 9]

CollP,Does your adjusted FF value of 1.17 show as a lowered readout on fuel flow gauge?

[CoolP 283]

Yes, it just reads the actual FF from the sim, therefore your range increases too.Remember that the value represents a tradeoff of some sort. You may see too low values on the low and very high range of the power band. I've just set it that way because it gave me the best cruise FF values.As said in the oil temp thread, the FSX engine model seems to have some inherent specials for the devs trying to reproduce not only engine behavior but also any 'real world' values.

Edited February 22, 2012 by CoolP

[CoolP 283]

I just ran the Lancair to get a feel for her performance again, and because I like that one very much, just like the JetProp. Well, that high performance piston thingy easily runs some 250 KTAS at FL180. But the climbout is a different beast, it took me some 17+ minutes to reach it with the recommended 170 KIAS climb speed. That's with the plane at max GW, so the boys and girls plus some baggage. Our JetProp climbs slower, some 140 KIAS, but the rates are nearly doubled then. Also at max GW.I can get the Lance to reach those 250 KTAS at FL160 too, and this would actually outperform the T Duke, because the big lady is redlined at some 198 KIAS. The Lance can run some 210 or so. But, of course, you can't fly all the folks in the Lancair, you don't have an AC nor a fancy autopilot, you can't fly into known icing and so on. And you don't run the reliable PT6 but some piston engine, if that counts. However, the fuel burn is close to about one half of that from the JetProp and way better than the T Duke of course.But I'd say for cruising fast and efficient, that Lancair kicks a.., while the luxury flying happens on the turbine planes. It's nice to have them all in the sim. :(

[CoolP 283]

If anyone cares, the T Duke is running some 270 KTAS on a slightly warmer day now, FL250, 1800 rpm and with 49 gph. 2000 rpm gives me some 276 KTAS and 53.2 gph. So for the fuel burn increase, you gain some 40 KTAS over the JetProp (32.5 gph). The Lancair can run some 268 KTAS at FL260 with her 75% power settings. Means 20.6 gph.This once again shows how efficient that small Lance is.

[FLIGHTO 8]

Yeah, I flew the ES Cirrus SR22 for many hours....but time outgrew that model.... I used to get great performance from that lil fixed gear bird..... Thats why I am excited about Carenado doing one.... My luck it wont be the turbo motor.... The same way they modeled the dash 21 instead of the others...Any way. I am about to do some FL low twenties performance testing as you stated... lets see what happens... if i get the same or faster true at similar FF, that will be my new cruise alt.... We will see.....

[Lifeguard911 9]

CollP,Does your adjusted FF value of 1.17 show as a lowered readout on fuel flow gauge?

I changed my FF value today and now the fuel flow looks much better. Thanks for the tip.You know, slowly but surely all of the folks here fixing one thing after another like panels, cfg's, airfiles, etc., Carenado will have made one fine product. :( Edited February 23, 2012 by Lifeguard911

[CoolP 283]

You know, slowly but surely all of the folks here fixing one thing after another like panels, cfg's, airfiles, etc., Carenado will have made one fine product. :(

So true. ^_^I had a point where I asked myself whether if I should he happy or angry about Carenado's way. Not talking about the FF or something. As said, that one is a tradeoff with any value in my eyes. No, I mean if Carenado had not done a JetProp, we couldn't fly her. Now they have done one, but we need to tweak her more or less heavily (e. g. on the gauges).I think the second part is better than the first, but I really, really hope that the devs are reading on how much work went into tweaking. By the way, I can't thank the small community around enough for their work and feedback. :(

[Lifeguard911 9]

Deep down, I think a lot of us enjoy doing the tweaking. If any manufacturer were to sell an aircraft were everything worked perfectly, we wouldn't be so eager to buy it because there would be nothing for us to do with but fly it!I have often thought that what we do is similiar to guys who build hot rods. Anybody can buy a car of the lot but with a tinker there, a tweak or two there, throw in a custom paint job and sooner or later you have your perfect machine.