#Real-Life

About this file

Asobo Cessna Citation Model 700 Longitude Performance and Flight Dynamics Modifications Project Version 1.3

Version 1.3 Changes:
-Fuel consumption / thrust / N1 adjustments to closer match real world performance tables.*
-Climb performance adjusted - aircraft more closely matches real world climb performance at MTOW
-Restored tail logo lights omitted from prior version.
-Engine starters now automatically disengage once the engines are running
-Reduced rudder authority with increasing dynamic pressure and further improvements to rudder input / response
-Updated / simplified pfd tape readout (override of the default cockpit.cfg)
-Updated Aircraft variation in aircraft.cfg; will assist users identifying version and installation.**
-Adjusted flap drag performance: reduction in drag coefficient.
-Adjusted g-limits to spec for the type
-Increased landing light and taxi light intensity and throw distance (optional install).***

*A kind benefactor provided me with Cessna Longitude test / calculated engine performance data sheets that I've used to reference fuel burn, climb performance, and N1 settings. Unfortunately, the underlying Asobo turbine engine modeling leaves a lot to be desired, but I’ve now spent a quite unreasonable amount of time working toward some more reasonable N1/thrust/fuel consumption figures that are much closer to the specs Cessna has tested and/or calculated, particularly at target cruise altitudes and ISA conditions. Annoyingly, and no matter what parameters I modify, the fuel burn in the cruise Mach range (0.78 to 0.84) is always significantly better at middle cruising altitudes (FL320 to FL390) than at higher altitudes (FL390 and above), definitely unlike the real-world aircraft, which really likes to be up above FL400 for best efficiency. It appears that the lapse rate for the turbine fuel consumption isn’t modeled correctly within the simulation code and doesn’t correctly follow the lapse rate in available thrust with increasing altitude (which is a little off, but manageable in cfg files). In MSFS2020, as turbine aircraft climb they lose thrust, as they should, but the fuel consumption doesn’t drop requisitely. So, the fuel burn parameters must either be adjusted to favor low altitude realism or high altitude realism - but not both. To get reasonable approximations, I’ve used some “fudge” factors that Asobo added to the engines configurations file and made numerous fine adjustments to several engine parameters and drag/lift parameters, and while those help get the modeling closer, they can still create some odd and unrealistic performance results. This is not surprising given that, as of V1.3 publish date, Asobo have not seemingly focused on turbine aircraft performance fidelity to the degree they have piston engine aircraft. Bottom line: I’ve tuned the engine performance specs to be reasonably close to Cessna’s IRL figures for cruise at FL400 to FL450 and above and for flying around in the pattern and below 10k feet. If anyone has found a magical coefficient somewhere in the engine.cfg file to properly model this fuel consumption lapse rate with altitude, please let me know!

**When Livery selections are made, the Longitude will display the following in the variant area "FDE Fix V1.3". This will help identify more quickly whether installation of the package was successful and quickly identify package version - this will only affect the default aircraft listing and not other liveries, although the performance modifications will be applied to all livery versions. 

***Optional additional installation package increases the intensity and projection distance for the landing lights and taxi lights. This will affect any aircraft using the included files. Additionally, landing lights will no longer project light onto the cockpit floor. There is a known issue with the taxi lights for which a solution has not yet been found: if taxi lights are on while gear is up (stowed) the light will project strongly into the cockpit.


Cessna Citation Model 700 Longitude Performance and Flight Dynamics Modifications Project Comments:

After reading user comments on the forums regarding the Cessna Citation Longitude model from Asobo concerning inaccurate weights, fuel consumption, handling, etc... and due to my own poor experience and frustration with Asobo's starting efforts, I started work on revising a wide variety of parameters in the configuration files for the Cessna CJ4 model to match the specifications for the Longitude. I modified the default layout.json file for the Longitude to bypass the encrypted configuration files and point to copied versions of non-encrypted files from the CJ4. These files have all been heavily modified and with a fair amount of guesswork I've been able to produce a working version of the Longitude that is more docile in handling and produces performance numbers that much more closely match the real-world specs. I'm not a Longitude pilot, so my modifications are more by feel and based on comments on forum topics from those claiming to fly the type. Input from type-rated pilots with knowledge of the aircraft handling and envelope will always be greatly valued. My adjustments are generally focused on performance and handling. Any issues with the G5000 suite and avionics in general are not the subject of this modification. If Asobo chooses to decrypt the xml files associated with the type, a motivated person could presumably start modifying and improving the avionics suite much like has been done with the CJ4 and other un-encrypted aircraft.

I have modified a great many variables and parameters in the available configuration files. I would greatly appreciate feedback on handling, control sensitivies, or other performance related parameters from knowledgable sources so I can continue to improve and update these modifications. If I missed something or you find a performance "glitch" please let me know.

Open items for possible future versions:
-Further engine performance improvements (especially if Asobo improves turbine engine modeling).
-Takeoff thrust settings, when a/c not in motion, will quickly exceed the 950C ITT limit until the aircraft achieves significant forward velocity: No solution identified at this time.
-Autopilot roll / bank control is still sluggish - haven't found a solution yet and this may affect precision approaches.
-Further refinements to handling and flight envelope modeling - further testing and tweaking could get it closer.

Significant avionics issues (there are many more, but these are commonly noted) that I don't have file access to address, but maybe someday...
-A/P max thrust authothrottle N1% limit. Could not solve using current file access.
-FLC MACH bug - FLC does not properly adjust Mach setting as aircraft climbs. This made testing of climb performance tricky!
-Disable or modify gear warning indicator when not appropriate. Could not solve using current file access
-Gallons fuel remaining displayed on MFD vs. pounds (or kilograms)-Auto-ground spoilers should set to Norm by default (instead of disarm)
-Cabin altitude is incorrect (too high) at high alt. 

Installation:
Download the .zip file and extract to desktop or other location of choice.
See included Install_ReadmeV1.3.txt file for further instructions and version notes.
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Current Version 1.30
Initial Release November 18, 2020
Last Updated November 29, 2020
File Size 45.48 KB
Downloads 2,637
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155 Comments
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    locstar
    December 02, 2020

    Hi how do I install this if I have my community on another drive, for example the simulator is installed in my K drive. Do I have to drop the additional layout.json in there too?

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    MiyuAkuryo
    December 01, 2020

    -Updated / simplified pfd tape readout (override of the default cockpit.cfg) this seemingly led to me not having colors at all anymore on the tape. So its kinda hard to tell whether I'm in the range for take-off/full flaps aswell as whether I'm close to overspeeding. Was it intended to remove all colors from it?

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    dakfly0219 replied
    December 01, 2020
    The G5000 doesn’t appear to have green or solid red speed tape markings. At least not that I could find references for in the literature and online images and video. It does have calculated V speed markers which you can somewhat replicate with the WT G3000 mod. Asobo haven’t modeled the auto-calculated v speeds to the extent you would find these in the real avionics suite. The red, green, and white speed tape colors are hard-coded to specific reference speeds and won’t change based on aircraft weight and configuration. So in summary, they are 1) apparently not available in the real G5000 suite, and 2) not going to accurately display meaningful reference speeds. For these reasons, I removed them.
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    CH4Pz
    December 01, 2020

    Hey man, loooove this mod, the asobo one came a long way last update, but had to go back to this, as just 'feels' so much more authentic. Im getting a weird issue with 1.3 though. When climbing on auto throttle with V/S at say 2500fpm and A/T at 250 (does it at all settings i tried, this is just example) the throttle will surge upto 250, then back right off and the plane drops like 30 kias, then powers back on. FLC definitely helps reduce this instead of V/S, but did notice a surging as it began to level on FLC too. Didnt notice it last version. Any thoughts?

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    dakfly0219 replied
    December 01, 2020
    I'm aware of this issue and looking into it for a future version update. Thank you!
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    MiyuAkuryo replied
    December 01, 2020
    can confirm having this same issue. As I usually always do my climbs/descends with FLC, except the initial climb while I'm not at my speed yet and FLC would thus descend instead of climb. I did notice this during level flight aswell. Been approaching the airport at 180 knots and it kept going to ~160 then back up to 180, back down etc.
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    dakfly0219 replied
    December 01, 2020
    Thank you for confirming. It’s a known issue and I’m working on a fix for next update.
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    connye
    December 01, 2020

    I have the Steam version and cannot find the folders to install this! Can you help me where to install for Steam version please :)

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    SoCalPilot
    December 01, 2020

    Here is a link to the results of my fuel efficiency test using v1.3 on an intracontinental flight from the Los Angeles area to Miami. https://forums.flightsimulator.com/t/longitude-fuel-efficiency-test-flight-results-using-the-mod-fix

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    SoCalPilot
    December 01, 2020

    I'm flying v1.3 on a cross-country flight right now from Southern California to Miami. I'm three hours into it. Started with 100% fuel (14593 lbs/2178 gal. My cruise altitude has been at FL450 and I currently am at 57% fuel (8330 ils/1242 gal). I have no passengers other than my co-pilot and we only have 400 lbs of baggage. I used to never make it this far on this route without having to stop and refuel. So far, so good!

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    antonvs
    December 01, 2020

    Another thank you for this great mod. As a person that flies Bizjets the most, this was and continues to be my favourite plane in MFS. I don’t know if it is your work, but the ground handling is so good - the plane just hugs the centre line with no effort at all. What a joy!

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    dakfly0219 replied
    December 01, 2020
    Thank you. Yes, I had to make quite a few adjustments to ground handling and rudder control parameters. The original default files were very twitchy on the ground and difficult to control.
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    AlphaOne
    November 30, 2020

    Keep up the work sir, it's amazing ! You have my warm recommendations.

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    Fabio
    November 30, 2020

    ciao chiedo se a qualcuno funziona il pannellino dell'autopilota? a me no

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    BillyMack
    November 29, 2020

    Thanks for your hard and great work. This mod makes the longitude one of the best planes right now in MSFS. Could you please make an accurated checklist? (climb and cruise profiles would be amazing) The POH is not free and it'svery very expensive

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    dakfly0219 replied
    November 30, 2020
    If time, permits I’ll look at this for a future release. Good suggestion!
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    OliveBeast20441 replied
    November 30, 2020
    BillyMack, The checklist in the Forums' link below is by no means complete, but perhaps it will serve as a temporary work around until a proper one is published: https://forums.flightsimulator.com/t/cessna-citation-longitude/154208/231 Originally posted on September 21st. Best regards, Mark
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    BillyMack replied
    November 30, 2020
    Perfect! One question. What is the most typical cruise speed? Thanks in advance Mark
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    BillyMack replied
    November 30, 2020
    Thanks a lot Dakfly
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    dakfly0219 replied
    November 30, 2020
    According to Cessna, your typical cruise speed is going to be between M0.81 and M0.83 at a typical cruise altitude of FL430. For this mod, you may actually get better fuel burn performance a little lower down due to the Asobo engine modeling limitations.
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    BillyMack replied
    December 01, 2020
    Perfect dakfly!
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    dakfly0219
    November 29, 2020

    New version 1.3 now available! Please comment any concerns or issues identified.

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    ronogent
    November 29, 2020

    Thanks for this much needed improvement which makes this plane my favorite now. Any possibility for you to create better default camera views instead of the much too zoomed defaults ?

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    dakfly0219 replied
    November 29, 2020
    You can directly modify your own cameras.cfg file in the official Longitude folder if you like to do this.


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