Bjoern

Mods for the Learjet 35A

69 posts in this topic

Hey Bjoern,

first off: Thanks for your mods one more time!

I am using the experimental FDE right now and for some reason, on several testflights under ISA conditions, I can't push the Lear beyond M.73 at FL430 and M.75 at FL390, both with Max Cont Thrust.
I got the feeling it may miss a little bit of power in cruise as I'm unable to reachanything close to the Barber Pole.

Would you have any ideas if there's any quick and dirty fix for this which does not make it a rocket closer to the ground?

Furthermore I can not keep the climb schedule advised in the Lears performance charts, which would be 250/.70. It will get stuck somewhere around FL300 with your FDE if I'm not using .60 as in your own chart.

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With the barber pole at M 0.8 or something, M 0.75 at MCT (note we're not talking max available thrust) isn't exactly unrealistic, eh?

The climb schedule is junk since MSFS' flight dynamics are too limited to deliver both accurate climb and cruise performance. It's either or and you're spending most time in cruise mode anyway.

 

In general, don't think too hard about the experimental FDE, i.e. love it or leave it.
All I had for reference was one bloody YT video in which you could see the gauge indications during cruise and I still had to make a guess regarding fuel and weight. That's not enough to make a FDE from.

 

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13 hours ago, Bjoern said:

With the barber pole at M 0.8 or something, M 0.75 at MCT (note we're not talking max available thrust) isn't exactly unrealistic, eh?

 

Hard to tell, I only have experience with passenger jets, those however can easily be pushed beyond the barber pole at max cont thrust.
Keeping cruise speed at MCT is more something for propeller aircraft as far as I know.
Then again I only have experience with airliners and props, but not with business jets, let alone with LJ35's, so this is more of an uneducated guess/expectation.

You're right on the climb schedule, for a free mod and the limited available reference it is still superb!

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6 hours ago, Emi said:

Hard to tell, I only have experience with passenger jets, those however can easily be pushed beyond the barber pole at max cont thrust.
Keeping cruise speed at MCT is more something for propeller aircraft as far as I know.
Then again I only have experience with airliners and props, but not with business jets, let alone with LJ35's, so this is more of an uneducated guess/expectation.

You're right on the climb schedule, for a free mod and the limited available reference it is still superb!

I used to complain about slow climbs in the 727 only to find out that this is very much realistic at higher weights (according to people who flew the real thing). But once up there, with some time to accelerate and fuel burned off and in pre-Oil Crisis cruise mode, it will ride the barber pole all day long at less than MCT. But you normally just don't do that. You set your engines for long range cruise and let the weight and weather do the rest. Or, if light, go higher or more economical than usual.

According to a former fighter jock who I've consulted with for the FDE, the "time to altitude" tables in the pilot manuals are more often than not just rules of thumb or plain bragging from the manufacturer anyway, only attained with spotless airframes and engines right out of the box and climb speeds that will have you starved for forward velocity once up at cruise altitude. So take the table(s) in the manuals with a grain of salt. Ideally, you'd accompany every flight with a stopwatch, pen, paper and a calculator to make your own chart(s), should you want or need it/them for flight planning.

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Had a nice flight tonight from KLAX to PHNL. It pushed the limits, there was a strong headwind the entire trip but with careful step climbs I was able to make it and still have a safe reserve.

I was grossly overweight (Max passenger and cargo load) so the cruise was probably not as efficient as it should have been. The engines were at max thrust the entire cruise but at the very high cruise altitude this was not much of a problem.

I'm using the experimental FDE you posted.

 

I'm not too sure about the realism of this, but I will poke around the net and see if I can find some more info about how the engines behave in cruise and in particular during long range flights. I am not sure the Real Lear 35A could make this flight in similar conditions at these weights. I'd also like to check whether the apparent lack of power at high altitude is accurate. I have a feeling the engines should burn more fuel but also produce more power at very high cruise altitudes. I was never able to catch the barber pole at any time of the cruise. I was constantly about 15-20 knots slower than the pole. At FL50 the barber pole was around the 200 knots range.

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You're not supposed to catch the pole. It's a limitation, not a target speed indicator!

 

The reference videos used for the creation of the FDE are in its readme. Especially the third one is important since it shows the bog standard cruise config of FL 430 and Mach 0.75, somewhat away from the barber pole. As you can see around the 0:46 minute mark, if you pause it just right, the engines are basically firewalled at 95% N2 and 97.something% N1. I've only assumed an associated weight (less than 14000 lbs or so) and worked from there.

 

Here's another one at FL450 and 0.79:

At the ten second mark, you can catch a very short glimpse of the engine indicator, which is at 96.something% N1. ISA ground speed for 0.79 at FL450 is 453 KTAS and these guys were doing 485, so that's a 32 knot tailwind right there. My conclusion is that they made use of that tailwind and were rather light at the same time, yielding lower N1 and higher ground speed.

As stated at the end of the checklists, the CAE Simuflight Lear 35 Operating Manual and Scott's spreadsheets were the source for the performance charts.

And generally, airplanes are supposed to run out of steam at one point. The default FDE simply had too much power, but is not the only (payware) add-on aircraft suffering from this.

Also consider that the flight dynamics offered in FSX can only be tuned to one operating point, which is mostly long-range cruise since it's the most popular one. Other points in the envelope will therfor show increasing deviations from the real world data. There's nothing one can do about it.

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New revision.

Just an update for v3.0. Nothing exciting to report but this:

Users of the load/save module, mind the new titles for the default repaints (rename your save files accordingly!) and - more importantly - remove the slash ("/") from "RDR/GTN" or "RDR/GTS" in the "title=" line of every repaint. This is ABSOLUTELY CRUCIAL because the save module otherwise won't work!

 

Updated files: Aircraft.cfg of the experimental FDE (new default repaint entries), System.xml and Loadsave.xml.

 

Download, as usual:

https://drive.google.com/file/d/0B6K_xiE2GqmMZFJoTWgyVUJpaTQ/view?usp=sharing

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10 hours ago, Bjoern said:

New revision.

Just an update for v3.0.

Thank you very much!

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