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scottb613

LJ35A - Lets Talk Numbers ?

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Hi Folks,

 

OK - from the get go - I'm definitely not expecting PMDG level of adherence to performance numbers on this product but I'm a bit confused and just trying to figure this stuff all out...

 

Recently - I just started putting together some numbers from the AFM charts in a tabular format - so I could have a ballpark idea on how to "properly" fly this thing... What I'm finding are gross mismatches from the data published in the AFM and that published on the FSW Reference page of the kneeboard...

 

We've all noticed and discussed the "Arming" of spoilers before - so we know the Reference page is wrong on that...

 

What is the Maximum Mach of this plane supposed to be - the FSW Reference states .75 Mi - the AFM states .83 Mi - so which does the flight model reflect ???

 

The FSW Reference states these flap speed limitations (Flap 8/250 KIAS), (Flap 20/200 KIAS), (Flap 40/150 KIAS) - - - The AFM states (Flap 8/198 KIAS), (Flap 20/183 KIAS), (Flap 40/153 KIAS)...

 

The two speed charts I've formatted from the AFM are for Vr and Vref - - - as these values only seems to be affected by weight - yet they differ wildly from the FSW Reference page...

 

So again - is it just the reference page that is messed up or am I misinterpreting the data from the AFM ??? FSW is known for getting the details right on a plane - so I really don't understand such large discrepancies between the two data sources... LOL - it could certainly be a gross conceptual error on my part as well...

 

Attached is my WIP on this...

 

 

a938ceca8c6681f70f65c58e809cf285_zpsqjkw

 

 

Regards,

Scott

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I see that the flap speeds of (Flap 8/250 KIAS), (Flap 20/200 KIAS), (Flap 40/150 KIAS) also happens to be what the kneeboard lists for the default Lear45 -- don't know what to conclude from that, however.

Al

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Hi Al,

 

Hmmm - maybe they went cheap on the Reference Page and just copied parts of the Lear 45 ??? Strange...

 

Here is a bit more RW performance data to add to your flying experience:

 

 

2016-12-16%2012_46_26-_zpswa7di4yl.png

 

 

Regards,

Scott

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Scott,

 

The Gates Learjet 35A was a very popular plane in its day so I would start with the printed specs and performance from the readily available online sources for the rw version.

 

I usually start with these guys.

http://jetav.com/gates-learjet-35a-performance-specs/

 

Then to fine tune something like the VMO speed I do some reading about base releases vs upgrades at block s/n dates. Usually these are very minor changes to performance but, it does happen.

 

You will notice the MTOW of the 35A was only 17,000 when it was first out, then moved to 18,000, then on to 18,300. This should be an indicator of which model Flysimware had in mind.

 

Your top end speed at altitude is going to be in the low 80s, for sure, not in the 70s. 0.82 or 0.83 sounds right. I will dig this one out.

 

The AFM says 0.83 M and that is real close to when the Overspeed alarm kicks in for my flight sim model.

 

That free AFM was one of the first releases if I remember correctly. If you look at the Max Takeoff Weight you will see that the 18,300 pounds version starts at S/N 035-067 so you can assume Flysimware s/b using specs in that range of Serial numbers and dates.

 

Here is what FSI teaches for all 30 series Lears.

 

Regards,

 

Ray

flaps.JPG

Takeoff.JPG

gear_2.jpg

  • Upvote 1

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Hi Ray,

 

Thanks so much for the detailed response - your always a wealth of information...

 

Reading through it now...

:wink:

 

Regards,
Scott

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FYI, an aircraft with the .83 Mmo - 359kt Vmo is uncorrected, indicated mach and your actual true mach number would be .81. Early serial numbered aircraft had an uncorrected pitot static system where only the pilot side altimeter was corrected.The copilot altimeter was uncorrected and could indicate hundreds of feet difference in indicated altitude during cruise flight.If the primary altimeter failed the crew would have to apply a chart correction to the copilot altimeter.

Later serial number aircraft have the corrected system .81 Mmo - 350kt Vmo which is a true mach indication and would have the later autopilot and have a digital SAT/TAS gauge on the panel.Externally you can tell which pitot static system is installed by looking at the pitot probes.The Rosemount system probes are longer and have a different shape.

 

Any currently flying aircraft would have been converted for RVSM certification and that would have happened starting around 2004 for USA registered aircraft.There are different electrical, pressurization, bleed air, anti ice, thrust reverser, pitot static versions and numerous aircraft modification kits that occurred over the life of the production.Using a copy of a flight manual or training publication is helpful but not necessarily applicable because no one has any idea what serial number was or was not used as the model.

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Even if they used a specific serial number or production block there is a very low chance that the flight sim model could be built anywhere near those specs and sell for $40. What I do is record specifics about my flights and from time to time see if I can glean some summary information that I can use and share with others.

 

To have meaningful information, I think you need to record enough for others to replicate the flight and see if their model is performing the same or very close. As we all know, you can walk out to a line of the same year and model of an airplane and every single one will fly a little differently.

 

I used to buy three Cessna 150 trainers at a time from Burnside Ott in Florida. They typically had something greater than a 100 small Cessnas flying on any given day. This was when they were training Iranians to 'learn to fly' along with a few other students from around the world.

 

It was always exciting to fly in there and try to pick 3 'good ones'. I insisted on flying a circuit or two to see how the airplane performed. It usually took 6 - 8 flights for me to find 3 that I was willing to put my money on. If one had been on the ground for more than a few days, I didn't even bother to check it out. I went for the ones that the students favored.

 

Regards,

 

Ray

 

Here is the type of flight data I record.

High Alt - Lear35A perf.JPG

  • Upvote 1

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Hi Gary/Ray,

 

Then it seems the .81 indicated is a good figure...

 

Thanks for all the information and insights - hah - as you can see I'm working on checklists and performance figure charts - so I really like this aircraft...

 

Gary - FYI - haven't forgotten 68MJ - I have the 15 pin stripes wrapping the fuselage done - updated the reg - cleaned it up a bit - however - the 15 pin stripes on the engine nacelles are giving me fits the way the texture is mapped around the bottom... LOL - seriously - the hardest paint I've ever done and I've done a bunch... We'll get'rrr done though...

:wink:

 

Regards,

Scott

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Ray,

 

Interesting numbers, although the later serial numbered 35 aircraft had a 510 pressurization system the aircraft was restricted to a maximum operating altitude of FL450.We operated one of the last built Lear 25 models for a few years and that aircraft was certified to FL 510. As the Lear 25 had tip tanks it obviously had more drag than the newer design 28/29 wing with the winglets and which was incorporated into the later Learjet models.I never got it higher than 470 and you had to have cold air and be very light weight to do it and not very efficient for operation.

 

The FSW version may provide enthusiastic performance and the parameters provide a guideline for use in the sim but as you say you don't get reality for $40.

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True, True and True. The big thing for me is that we don't have to wear the O2 masks in the Flight Sim! Most of these guys don't have a clue about rapid decompression and the near instant affects.

 

Regards,

 

Ray

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True, True and True. The big thing for me is that we don't have to wear the O2 masks in the Flight Sim! Most of these guys don't have a clue about rapid decompression and the near instant affects.

 

Regards,

 

Ray

 

I took a high altitude course during recurrent training one year that included the altitude chamber session.The purpose was to recognize your individual symptoms of hypoxia onset.The chamber was session was educational and interesting however the classroom portion was some what unnerving as you were informed about the consequences of a rapid decompression and effects on physiology.The Payne Stewart event was a real eye opener and we took that course shortly after the accident. 

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I got my Altitude Chamber certification at McCoy AFB Orlando, before it was taken over for Disney. Yep, a real eye opener.

 

Ray

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