If there ever is a Lear 35A - 2.8...

[scottb613 1,188]

Hi Folks,

Great stuff...

 

Based on Gary's pix - it seems that the FSW Lear may be a tad overpowered as well... If the FSW is in the 97% N1 around 25,000 Ft - we'd probably be in a rocket like 4000 FPM climb... The RW Lear is doing 250 KIAS at 1000 FPM at that setting - granted it seems like a very warm day... Temps for ISA should be around (-34 C) @ FL250 - looks like they are (+3 C) if I am reading the gauges correctly... Also - in cruise - it looks like 92% N1 - whereas we normally have to be around 82% N1 to prevent over speed... Aircraft loading is unknown... Wonder if it would be worth trying to modify the power scaler ???

 

Are these all XML gauges ???

 

One additional sidebar question - when the pubs mention required runway lengths - they aren't talking about distance to get airborne - right - they are talking about the distance needed to make V1 - then do a complete stop before running out of runway - correct ???

 

OK two sidebar questions - does the RW Lear need "step climbs" ??? I noticed the pubs seem to omit cruise data for higher weights in the higher FL400 plus... Normally - you just don't power up to FL450 with a full load - do you ???

 

Regards,

Scott

[ark 1,288]

The controller or keyboard assignments for the G1000 buttons have to be assigned in FSX though and will remain global.

 

 

For those that have a registered copy of FSUIPC then by making the G1000 software key assignments using FSUIPC rather then through FSX you can make the key assignments 'profile specific' and then the assigned keys will be available for reuse (different assignments) with other a/c.

 

 

I'm making good progress reworking the autopilot vertical modes, so you can look forward to more.

 

 

I guess I missed what the issue is with the vertical modes.  Is the goal here to make the vertical modes more realistic with respect to the real FC-530 autopilot?

 

Al

[odourboy 1,289]

 

 

Wonder if it would be worth trying to modify the power scaler ???

Engine static thrust settings as per the aircraft.cfg look correct, but the other factor is table 1506 (Corrected Thrust Factor vs CN1 and Mach number) of the airfile. It appears to be based on the Lear AI model and may be too aggressive. However, I could be totally off base here, so you might ask the developers how they did the engine airfile tables.These are tough to get right because there are several moving parts (not to mention a flaw in the FSX jet engine pressure altitude modeling).

[albar965 1,041]

 

 

One additional sidebar question - when the pubs mention required runway lengths - they aren't talking about distance to get airborne - right - they are talking about the distance needed to make V1 - then do a complete stop before running out of runway - correct ???

 

No. Take off distance is until you reach 35 ft above the runway. See manual figure 5-28.

 

This model is overpowered. You can take off in slightly less than 3000 ft at MTOW at sea level under standard conditions instead of 5100 as per handbook.

 

meh

 

Alex

[scottb613 1,188]

Hi Alex,

 

Thanks for responding... So is the distance from V1 to get 35 feet above the runway greater than the distance to go from V1 to a stop ? Maybe I have a gross conceptual error - V1 is your decision speed - so if you can't stop on the remaining runway from V1 - why even have it ? I'm s SEL guy and this is my first real attempt to master bizjets...

 

Regards,

Scott

Engine static thrust settings as per the aircraft.cfg look correct, but the other factor is table 1506 (Corrected Thrust Factor vs CN1 and Mach number) of the airfile. It appears to be based on the Lear AI model and may be too aggressive. However, I could be totally off base here, so you might ask the developers how they did the engine airfile tables.These are tough to get right because there are several moving parts (not to mention a flaw in the FSX jet engine pressure altitude modeling).

Well - definately interesting info - I wonder if we have the skills to adjust any of this ? I've dabbled with Air Wrench and other FDE tools a bit but never really completed a significant FDE mod I was happy with and I've never worked with turbines...

 

Regards,

Scott

[odourboy 1,289]

Well - definately interesting info - I wonder if we have the skills to adjust any of this ? I've dabbled with Air Wrench and other FDE tools a bit but never really completed a significant FDE mod I was happy with and I've never worked with turbines...

 

Regards,

Scott

These tables are not hard to edit - there are a couple of airfile editing tools kicking around. The hard part is to get the operational data points necessary to make them accurately reflect the engine performance then testing your changes to see they conform (often an iterative trial & error thing).

 

Also, the issue may lie in the drag.

[albar965 1,041]

Thanks for responding... So is the distance from V1 to get 35 feet above the runway greater than the distance to go from V1 to a stop ? Maybe I have a gross conceptual error - V1 is your decision speed - so if you can't stop on the remaining runway from V1 - why even have it ? I'm s SEL guy and this is my first real attempt to master bizjets...

 

Sorry, total misunderstanding on my side. I'm talking about takeoff distance not required runway length.

Currently I adjusted the thrust scalar down to 0.92 which unfortunately results in an anemic climb performance at higher altitudes. I'm not a FDE expert.

 

Alex

[Bjoern 1,157]

Since you guys opened the "flight dynamics" can of worms...

 

1) The EGT gauges are modeled in 3D and therefor inaccessible. They use the FSX default EGT variables, which are powered by a very simplified and, frankly, unrealistic model. You can overwrite the variable with XMLTools at the cost of some very ugly needle twitching at low RPM. So that isn't an option. (EPR, by the way, is just as unrealistic.)

 

2) You can tweak yourself to death on the flight dynamics unless you find some usable information from the real thing online. Either do the engine tables according to the real specs and adjust lift and drag or get lift and drag right and then do the engine tables. But without any hard reference info on any of those three elements, you're screwed.

 

3) FSX' atmospheric modeling stops at 36089 feet (boundary to the tropopause in an ISA atmosphere) and will be regarded as constant above that. High altitude performance therefor can not be modeled according to real world data.

 

4) Since FSX works with a constant value for thrust specific fuel consumption, you will have to tweak this parameter for cruise and live with the realism penalty in other flight phases OR work around this with some XMLTools magic or Doug Dawson's FuelDump gauge (already used in the Learjet for, well, dumping fuel)

 

If anyone really wants to tackle the FDE, read up on real world aerodynamics and use these documents as references while diving in. Lots of university lectures on real aerodynamics can be found online.

http://www.entre2poles.fr/Entre2poleS/Le_Blog_de_Mr_Throttle/Entrees/2009/1/31_Flight_Simulator..._Cest_fini_!_files/Aircraft_Sim_Tech_Zyskowski.pdf

http://fsdeveloper.com/forum/resources/flight-dynamics-in-msfs-v1-0.169/

http://fsdeveloper.com/forum/resources/fs-thrust-vs-altitude-calculations.43/

https://msdn.microsoft.com/en-us/library/cc526949.aspx

Air file tool: http://www.difusco.de/ootb/AAMV22.zip

 

I guess I missed what the issue is with the vertical modes.  Is the goal here to make the vertical modes more realistic with respect to the real FC-530 autopilot?

 
Yup. I'm using a LJ31 manual (from Smartcockpit, I think) as reference which uses a different autopilot, but I guess the modes available in the 35A should be the same or at least quite similar. As far as I understood:
 
IAS/MACH - hold airspeed/mach at the time of mode engagement; may be adjusted with the vertical trim switch on the yoke
V/S - hold vertical speed at the time of mode engagement; may be adjusted with the vertical trim switch on the yoke
GS - follow glide slope
ALT SEL - will arm near the altitude indicated on the altitude selector panel and, upon attaining that altitude, switch to "ALT HLD" mode
ALT HLD - will hold the current altitude; may be adjusted with the vertical trim switch on the yoke*
 
 
*The manual doesn't mention how adjustment works on the real thing, so I assume that the aircraft will simply revert to "ALT SEL" mode and it'll be up to the pilot how to get there.
 
 
So far, the ALT and VS modes are in as described above and I think I got the IAS mode working well enough. Still need to do MACH HOLD though.

[scottb613 1,188]

Hi Bjoern,

 

As always - good stuff - as far as flight model fidelity - LOL - I'm just looking for hand grenade close...

 

We do have some good flight data thanks to your finds... I like the tables with time,fuel, and distance to get to various altitudes...

 

Also that profile off of Fltplan gives us some expected climb rates...

 

250 KIAS/ .7 MI

 

10,000 - 3,820 FPM

20,000 - 2,760 FPM

30,000 - 1,680 FPM

40,000 -   740 FPM

45,000 -  500 FPM

 

As far as your autopilot adjustments - they sound VERY similar to Bob Scott's Honeywell in the Tin Mouse B737-200 autopilot - he programmed the ability to make adjustments like you mentioned by pressing on the yoke while the autopilot is engaged... He's still around and might be a good resource ?

 

Regards,

Scott

[ark 1,288]

 

 

Yup. I'm using a LJ31 manual (from Smartcockpit, I think) as reference which uses a different autopilot, but I guess the modes available in the 35A should be the same or at least quite similar. As far as I understood:

 

Since you are doing all this work (thanks!), I sure wish we could find a manual for the FC-530 autopilot so we could be sure how things are supposed to work.

Al

[Bjoern 1,157]

Hi Bjoern,

 

As always - good stuff - as far as flight model fidelity - LOL - I'm just looking for hand grenade close...

 

We do have some good flight data thanks to your finds... I like the tables with time,fuel, and distance to get to various altitudes...

 

Also that profile off of Fltplan gives us some expected climb rates...

 

250 KIAS/ .7 MI

 

10,000 - 3,820 FPM

20,000 - 2,760 FPM

30,000 - 1,680 FPM

40,000 -   740 FPM

45,000 -  500 FPM

 

As far as your autopilot adjustments - they sound VERY similar to Bob Scott's Honeywell in the Tin Mouse B737-200 autopilot - he programmed the ability to make adjustments like you mentioned by pressing on the yoke while the autopilot is engaged... He's still around and might be a good resource ?

 

Expected climb rates are all fine and dandy, but only as long as weight and atmospheric conditions are specified.

 

They are very similar because that's all that autopilots offered back in the day. The more sophisticated modes only hit the market from the early to mid-1980s onward and mostly in airliners.

I don't need input from Bob since "adjust by trim switch" is already in and was one of the easier to implement parts of the autopilot. But I'm not sure if adjustment by pitch trim in the FC-530 is possible since I'm just extrapolating from the KFC-3100 of the Learjet 31.

 

 

 

Since you are doing all this work (thanks!), I sure wish we could find a manual for the FC-530 autopilot so we could be sure how things are supposed to work.

 

Couldn't find one, but "Flying the Classic Learjets"* on Google Books mentions much of the same modes in the description of the older FC-200 model, "Flying"** specifically mentions HALF BANK and ALT SEL as an improvement to the old autopilot (which are lacking in the FC-200) and the Learjet 31 flight systems description from SmartCockpit with the KFC-3100 AP only has two VNAV-related buttons while the rest pretty much matches the functionality of the FC-200 and what little was said of the FC-530.

Youtube is no help since most videos show the FC-200.

 

So I just assume that the FC-530s vertical modes work about the same as in the KFC-3100, maybe without the possibility to adjust target values by pitch trim.

 

 

*https://books.google.de/books?id=Ne3YWS9Iy3EC&pg=PA106&lpg=PA106&dq=fc-530+autopilot&source=bl&ots=q9tRcvIzIN&sig=NjQQyr1Q1f7vh5DlO13an4ktRcI&hl=de&sa=X&ved=0ahUKEwie85_CjbHRAhXBXRQKHYFPCNQ4ChDoAQglMAA#v=onepage&q=fc-530%20autopilot&f=false

(The page about the ALT mode is blocked out)

 

**https://books.google.de/books?id=BzY0_48Lz54C&lpg=PA34&ots=bLqx4HSa-T&pg=PA30&redir_esc=y#v=onepage&q&f=false

[ark 1,288]

Couldn't find one, but "Flying the Classic Learjets"* on Google Books mentions much of the same modes in the description of the older FC-200 model, "Flying"** specifically mentions HALF BANK and ALT SEL as an improvement to the old autopilot (which are lacking in the FC-200) and the Learjet 31 flight systems description from SmartCockpit with the KFC-3100 AP only has two VNAV-related buttons while the rest pretty much matches the functionality of the FC-200 and what little was said of the FC-530.

 

 

I have also been looking for info on the FC-350 without success. Since Mark decided to model this autopilot, maybe he has a source for documentation. Or maybe we can find a RW pilot with FC-530 experience.

Al

[charlie130 196]

The simulation visual model is pretty good but recognize the limitations of an entertainment product.

 

Hi Gary, I agree its a very entertaining sim!

 

I recently tested the envelope a bit. From KEGE to KSTS. Had a 100+ knot head wind. Saw Mach 8.9 at FL480! Tried for FL 520 but engines gave up at FL510...LOL  At least we do see an envelope, even if it is a rather optimistic one! :wink:

 

I don't think anyone really exceeded M.78 in reality, those straight wings aint an F16, even if the Lear did begin life as a fighter bomber! :smile:

 

regards

 

David

[Bjoern 1,157]

This thesis deals with LJ35 takeoff performance in the takeoff domain and is probably the only source for some hard data.

http://www.fzt.haw-hamburg.de/pers/Scholz/arbeiten/TextEhrigF.pdf

TFE731 FAA type certificate: http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/39439532f4272527862568f7006f821d/$FILE/E6we.pdf

TFE731: http://www.airliners.net/forum/viewtopic.php?t=746059 (warning: Potentially inaccurate RPM figures.)

 

 

I'd really appreciate if someone else could try to fix the FDE as I just don't have the time.

[doublem 20]

2.8...Coming Soon (look near the end):

 

http://flysimware.com/website/LEARJET_35A_UPDATES.html