Falcon 50 Cruising altitude >FL360?

[Gridley 257]

16 hours ago, JRBarrett said:

In the current FSW  model, I pitch down to acquire 320 knots climbing through 10,000 feet (using V/S), then switch to IAS hold and let it eat, controlling rate of climb with power. When current IAS reaches the point where 320 IAS = Mach 0.75, I switch to Mach hold. The transition will usually happen somewhere between FL250 and FL280, depending on air temperature. Once above FL250  or so, power levers do go almost full forward to keep a decent rate of climb.

Doing that, I have no problem reaching the mid to upper 30’s in reasonable time. I rarely fly above FL390 unless very lightly loaded, which is also true of the real aircraft. In real flights typical max cruise altitude would be FL400 westbound or FL410 eastbound. FL450 is possible, but not until the wing tanks are almost depleted, meaning you would be down to feeder fuel only, which means you had better be in a position to land within 60 minutes - i.e. once you get to FL450, you are only going to be there a short amount of time before it will be time to begin descent.

Tremendously valuable information for me.  Thanks a ton, Jim.

[Ariel 6]

An interesting thread. Thanks - lots of good stuff.  Like Al I have now done a flight test climb to see just where I would get to in term of realistic cruise levels with the current 2.0b model.

I assumed a mid-range configuration with 50% fuel, two pax and their bags, so not too demanding.  With regard to a realistic cruise level - the international ATC world assumes a basic minimum performance capability of 1000 fpm up or down - so I used that as the measure for the max cruise level.  Of course (with special clearance) cruise climbs can take place at less than 1000 fpm, so I went on up to the point where the climb rate was less than 500 fpm and quit there, levelling out to test the max level speed.

I show below a table of numbers that I noted on the way up, for what it's worth.  I had to use full forward throttle max power from 27,000 ft upwards until the end of the test (!).  Engine temps seemed to hold within what I think are the limits.

My conclusion was that the max realistic initial cruise level was FL 340.  With an assumed permission for a cruise climb I did get to FL380, but at that point I was clearly nearing the aircraft's service ceiling (an old term, maybe), so I levelled at that and waited for the maximum level speed .  This was M 0.81, way below the barber's pole.

So...  I am full of admiration for what FSW has achieved for simulation on a home PC, using old FSX software as a base.  The numbers are in the right range and I really enjoy flying it.  Nevertheless, from what Jim says above I'm certain that we've gone from the original "way overpowered" to an underpowered version.  The real FA50 may heve been a bit short of breath at high level, but considering the gross weight I used in this test the FSW version doesn't get there any more, at least for me.

I hope this won't offend the builder of the last flight model - the fuel burn wasn't right before that - and the software is limited.  But I would definitely like to trade a bit of the economy for a little more N1 power in the stratosphere!

Ariel

FSW Falcon 50 v2.0b Climb Test – short range configuration

Gross Weight: 34,510 lbs. (3 crew, 2 pax, 300 lbs bags, 50% Fuel).

Fuel Weight: 13,188 lbs

OAT set by Active Sky P3D weather engine.  Dep. AD elevation 340 ft.  OAT 19° C

All numbers as read from VC instruments (N1’s ± 1).  Temperatures are Total Air Temp (TAT).

Alt.	TAT °C	AP Mode	Climb Rate fpm	Av. N2 %	Av. N1 %	Comment
10,000	-1	ALT SEL + IAS (290 kts)	-	98	99	IAS climb set
20,000	-24		2000	98	96
25,000	-36		2000	100	98	Power increase
27,000	-		-	100	97	Throttle full forward (max).to the end
29,000	-	ALT SEL + MACH (0.70)	-			MACH climb set. (290kts = M 0.70)
30,000	-46		1600	99	95
34,000	-52		1000	96.5	93	Realistic (normal ATC) max cruise level.
36,000	-		800	96	92	Slow cruise climb
38,000	-60		500 or less	95.5	91.5
38.000	-60	ALT	-	95.5	91.5	Full power maximum level speed M 0.81

 

 

 

 

[ark 1,288]

To some degree users can tailor the performance of the Falcon 50 to suit their needs. In the aircraft.cfg file (which is in the main aircraft folder) there are engine and aircraft parameters you can tweak. Unless you have the necessary experience, this is easier to experiment with than with the air file:  For example:

[TurbineEngineData]
fuel_flow_gain          = 0.0065                //Gain on fuel flow
inlet_area              = 4.2500                //Square Feet, engine nacelle inlet area
rated_N2_rpm            = 29920                 //RPM, second stage compressor rated value
static_thrust           = 3500                  //Lbs, max rated static thrust at Sea Level
afterburner_available   = 0                     //Afterburner available?
reverser_available      = 1                     //Thrust reverser available?
ThrustSpecificFuelConsumption = 0.6             //Thrust specific fuel consumption (Jets)
AfterBurnThrustSpecificFuelConsumption = 0      //TSFC with afterburn/reheat engaged

[jet_engine]
thrust_scalar = 1.0

[flight_tuning]
cruise_lift_scalar     = 1.0
parasite_drag_scalar   = 1.0
induced_drag_scalar    = 1.0

So if you would like to increase the thrust of each engine by 10%, change the thrust scalar value from 1.0 to 1.1, etc.

Information on the aircraft.cfg file parameters can be found here: http://www.prepar3d.com/SDKv3/LearningCenter/simobjects/aircraft_configuration_files.html

Al

Edited May 21, 2020 by ark

[JRBarrett 3,050]

You could boost the static sea level thrust to 3750 from 3500, which would emulate upgrading to the TFE731-40, which is the engine that came standard on the 50EX. Many original Falcon 50s have upgraded the -3 engines to the -40. I just came across a Honeywell brochure online that was printed in 2001 for operators considering the -40 upgrade. FWIW, the original Falcon 50 time to climb spec from sea level to FL390 was 39 minutes with the -3 engine.

The -40 improves that to 23 minutes. The sea level thrust is higher, as is the thrust at FL400

The TFE731-60 used on the Falcon 900 is rated at 5000 pounds static thrust at sea level. 

[ark 1,288]

43 minutes ago, JRBarrett said:

You could boost the static sea level thrust to 3750 from 3500, which would emulate upgrading to the TFE731-40, which is the engine that came standard on the 50EX

Now that sounds like an interesting idea -- thanks Jim.

Al

Edit: Should we be surprised an A&P mechanic suggested we change all the engines!  😉

Edited May 22, 2020 by ark

[JRBarrett 3,050]

29 minutes ago, ark said:

Now that sounds like an interesting idea -- thanks Jim.

Al

Edit: Should we be surprised an A&P mechanic suggested we change all the engines!  😉

If anyone wants to experiment with the values, would not change more than one at a time. Increasing static thrust will affect takeoff performance. Not sure if it will also affect performance at higher altitudes. I’d be reluctant to change anything too far - currently the N1 and fuel flows are just about perfect within the limits of standard sim engine modeling - much more accurate than in early versions.

[ark 1,288]

12 minutes ago, JRBarrett said:

If anyone wants to experiment with the values, would not change more than one at a time. Increasing static thrust will affect takeoff performance. Not sure if it will also affect performance at higher altitudes. I’d be reluctant to change anything too far - currently the N1 and fuel flows are just about perfect within the limits of standard sim engine modeling - much more accurate than in early versions.

The suggested static thrust (engine) change is about a 7% increase. I wonder how doing that would compare to just changing the thrust scalar to 1.07 instead -- maybe the thrust scalar would provide a boost at all altitudes?

Do we have any test pilots out there willing to do some test flights and report back?

Al

Edited May 22, 2020 by ark

[JRBarrett 3,050]

Just now, ark said:

The suggested static thrust (engine) change is about a 7% increase. I wonder how doing that would compare to just changing the thrust scalar to 1.07 -- maybe the thrust scalar would provide a boost at all altitudes?

Al

Possibly! 

[Ariel 6]

Great stuff Jim and Al - thanks.  Lots of fun to be had now!  (Wish it didn't take so long!).

Ariel

[Ariel 6]

As a follow-up, I have now tested a small tweak as suggested.  As Jim's 250lb static thrust increase to the EX engines is 7%, near as word not allowed, I increased the thrust scalar to 1.07 as per Al's suggestion.

I repeated my previous air test with the same weights and speeds, but will spare you all the data table word not allowed and cut to the chase.  It felt much the same but the high level performance did improve.  The climb rate decrease at high level was not quite so consistent this time - I held the 1000 fpm minimum up to 39,000 ft, and even (almost) to 40,000 ft, but it then fell right off the table.  I could only crawl up after that, and stopped at 41,000 ft.  So with a half fuel load my reasonably attainable cruise level went up from FL340/350 to FL380/390.

At 41,000 ft in level flight and full power the speed crept up to a max of M0815, just below the barber's pole at M0845. The fuel burn at this time was 700 lbs per engine, which sounds ok to me.

So I think this was a good result, and after reading what Jim B. said above, plus what I've gleaned elsewhere, I think it equates well enough to the real-world FA50.  I shall stick with this small tweak anyway, it felt better.

Thanks again for the advice,

Ariel

 

[ark 1,288]

2 hours ago, Ariel said:

As a follow-up, I have now tested a small tweak as suggested.  As Jim's 250lb static thrust increase to the EX engines is 7%, near as word not allowed, I increased the thrust scalar to 1.07 as per Al's suggestion.

I repeated my previous air test with the same weights and speeds, but will spare you all the data table word not allowed and cut to the chase.  It felt much the same but the high level performance did improve.  The climb rate decrease at high level was not quite so consistent this time - I held the 1000 fpm minimum up to 39,000 ft, and even (almost) to 40,000 ft, but it then fell right off the table.  I could only crawl up after that, and stopped at 41,000 ft.  So with a half fuel load my reasonably attainable cruise level went up from FL340/350 to FL380/390.

At 41,000 ft in level flight and full power the speed crept up to a max of M0815, just below the barber's pole at M0845. The fuel burn at this time was 700 lbs per engine, which sounds ok to me.

So I think this was a good result, and after reading what Jim B. said above, plus what I've gleaned elsewhere, I think it equates well enough to the real-world FA50.  I shall stick with this small tweak anyway, it felt better.

Thanks again for the advice,

Ariel

 

And of course you could always increase the thrust scalar to 1.1 to see what VS could be maintained up to 41000ft, although what that would do to the fuel burn I don't know.

Thanks very much for the feedback -- go stuff, and I'm sure of interest to others.

Al    

[HowAreYourRides 4]

Hi guys,

New to the forum.  Very interesting thread you have here.  Just wanted to offer some info I found.  Below is a link to a Falcon 50 performance manual I stumbled upon, and which I'm going to study in more depth in the coming days.  It says it's for the TFE 731-4-1C engines.  It does seem like the stars need to align for it to get much higher than FL400/FL410.  And even then, climbs take a very long time.  The chart limits seem to stop at 300fpm or 40 (!!) minutes.  1000FPM seems a little aggressive for inching up to the limits of your plane's capability of the day.  I fly the E175 and we routinely peter out to 700, 800 fpm - sometimes less if the wind shifts to a tailwind.  I think 500fpm is the expected minimum that defines your service ceiling in a jet.

The performance manual linked below says this about the climb profile:
Two different climb schedules are recommended:
• 260 KIAS/M0.72 associated with long range and M0.75 cruise
• 300 KIAS/M0.80 associated with M0.80 and maximum cruise thrust cruise

Also - side note.  I have about 225 hours in the Lear 35 (N604S and N360AY, which both have repaints available (!!) - so awesome).  Our climb profile in that thing was roughly 250/M.70.  The guys I flew with referenced turbine temp for climb power setting and, depending on who you talked to, it ranged from 795 to 830.  Cruise, also depending on who you talked to, was as follows:
FL200s - TT 735, M.75, or M.78
FL300s - TT 765, M.75, or FF 600 (most guys)
FL400s - FF 600 (most guys), or M.75

http://maistl.com/sites/wsa/50dash4/wp-content/uploads/2010/08/wsa-falcon-50-dash-4-performance-manual

Again, I have to study it a bit more, but I think there's a good chance that may answer just about all the performance questions we could possibly come up with.

All the best,

Tony

 

[ark 1,288]

1 hour ago, HowAreYourRides said:

New to the forum.  Very interesting thread you have here.  Just wanted to offer some info I found.  Below is a link to a Falcon 50 performance manual I stumbled upon, and which I'm going to study in more depth in the coming days. 

Tony -- thanks very much for the Performance Manual link and info. I have added the link under our Falcon50 Reference Information thread.

Al

Edited May 24, 2020 by ark

[Mad_X 12]

On 5/22/2020 at 2:46 AM, JRBarrett said:

Possibly! 

I would also love the see the slightly higher fuel burn of the middle engine 😉. 

[JRBarrett 3,050]

I have since spoken to one of our Falcon 900 pilots who used to crew a classic (non-EX) Falcon 50 a few years ago. He said that at heavier weights, they definitely would not try for upper 30s flight levels, as the aircraft simply did not have enough thrust to get there. The particular operator he flew for had offices in New York and California, and most flights were coast-to-coast with full or almost full tanks and typically 2 or 3 passengers. On an eastbound flight, they would initially cruise at FL350, stepping up to FL370 after about 2 hours, and eventually to FL390. They rarely, if ever went to FL410.

On the much more powerful 900, they typically can go directly to the upper 30s even with a full fuel load (21,000 pounds), and with less than full fuel will often go directly to FL400 or 410.