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Guevorkyan

Coast to coast test flight (FA50)

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Hi everyone,

I wanted to share my thoughts during a flight from Tahoe TVL to Teterboro TEB. Sim is P3D V4.4.

Addons:

PFPX (custom aircraft profile)

RXP GTN 750 (two units) (is there a way to interconnect them?)

ASP4 (ASCA Global Automatic)

To plan this flight, I used PFPX wih a custom made Falcon 50 profile. I've done this with the help of some Performance Manual Supplement I found around for the -4 engines (for reference, ours is the -3 model). This manual enabled me to compile a PFPX profile using different climb and cruise settings, so flexibility was the name of the game. You want to cross the pond? LRC or M.75 would be wise choices, or try the M.80 setting...

Climb performance has two possibilities, 260kias/M.72 or 300kias/M.80. Suits all the needs. Descent perfomance is only one, M.80/330kias.

Initial cruise altitude is derived from these charts and in my profile I only compiled for ISA conditions, although there are tables for -10°, +10° and +20°C.

Ok, this is PFPX release for the flight

BTIEp1g.jpg Fv1rhG7.jpg

According to the dispatch, initial cruise flight level with a TOW of 31,500lbs was FL410, with a possible step climb to FL450 at waypoint OCS.

Ok, let's look at the performance charts! Remeber that the PFPX profile is in reference to these charts (and a TFE 731-4 engine, not -3!).

Here's the climb performance for 260kias/M.72, which I chose mainly because I wanted to test the profile, and because of the nice tailwind forecasted for the route!

lX3RH0g.jpg

It looks like at ISA temps and 31,000lbs, initial cruise level of FL410 is very comfortable for this airplane. But let's look for a higher FL.

0DyFbVR.jpg

At FL430 it gets a bit heavy. Sustainable, but heavy nonetheless. I like playing it safe, especially if the ISA deviation turns out to be on the positive side. 410 it is! 

 

CLIMB

The Falcon 50 is very powerful, so the departure at TVL RWY36 (long runway, 6268ft elevation, -10°C OAT) is a piece of cake. There's a requirement to be able to be at or above 13,000ft 9.7nm out from the end of the runway. I got up there with distance to spare!

At 10,000ft I lowered the nose a bit to achieve 260kias and proceeded to climb in IAS mode until reaching M.72, when I switched to Mach mode. Climb rate obviously was managed by thrust setting.

g9gadeQ.jpg

I had to ease the throttles quite a lot so the airplane won't go "vertical". So much power. My climb power setting was around 80-85%, can't remember correctly. I start to suspect something is off compared to the charts (possibly the difference between -3 and -4 engines). 

Before reaching FL410, I start easing the throttles further so the climb rate gently reduces to below 500ft/m. This is because I'm in Air Hauler and if I reach the cruising level at over 1,000ft/m the pitch down commanded by the AP is massive (around 0.6g). People complain at the back. I would...

At TOC, the Davtron clock said 19 minutes since take off. So that's pretty accurate performance.

 

CRUISE

My aim is to attain a M.75 cruise as per this table here (look for the 41,000ft table.

Yd20ZUf.jpg

Here it says a very interesting thing. At the time I reach FL410, my weight is around 30,000lbs. ISA dev is +2, so I use the ISA line.

Every number seen in this table concurs with what I see from the cockpit...except N1 %.

To maintain M.75 at FL410, ISA +2 etc, I had to set my N1 at around 76-77%. A good 13% difference (the manual states that there may be a 2% difference, but that's it). 

I repeat, this table is for a -4 engine. I can't find a -3 performance chart. I don't know, but maybe the airplane is "too" powerful in the sim? I remember yesterday when I was able to take off from a 800ft gravel runway @32,000lbs without any problem...Could it be that it is too powerful, more powerful than the real thing? 

 

Also, I started watching the fuel system more closely. I begun to worry about the Central feeder tank quantity. It seemed like the Central Wing Tank wasn't filling the feeder tank, it's quantity remained constant. The only way I could get the central wing tank to flow backwards was by switching the Intercoms. Still, the Central feed tank won't fill.

The other two feed tanks remained constant at 609 lbs throughout the flight, with the corresponding wing tanks filling them. 

The central feed tank kept reducing it's quantity until it reached 609 lbs. By that time I was over the Great Lakes and looking for an alternate airport in case of possible fuel starvation!

That's when the Central Wing Tank started flowing Jet fuel aft to the central feed tank, keeping it to 609 lbs all the way to landing. Is that how it's supposed to work? Maybe to maintain the CG within limits?

 

Back to the cruise, chosing to ignore the power setting (anomaly?), I figured out that I could climb to FL430 right a way, right?

UeFckko.jpg

Mmmmm....No. I don't think so. Again, I like to play it safe. I don't want to be too close to the coffin corner, my AOA at 410 was already at 0.5 V/Vs, near the yellow arc.

I could have attained FL430 if I wanted to, but any changes in the airmass could affect me big time. See that FL450 was right out of the question.

I decided to wait until my waght is around 28,000 to step climb to FL430. PFPX suggested FL450 by OCS...we'll see...

Fuel flow was right on the money, I'm pleased to say. Perfect match to the preformance charts. The N1% though...

 

DESCENT

Using the second GTN750 unit to calculate VNAV, I start the descent first by VS, so I can accelerate to M.80, and then Mach hold. Again, thrust managing the descent rate.

Plan was to do the ILS RWY06 approach to circling minimums and switch to RWY01 due to surface winds.

I maintain M.80 on descent until reaching 330kias, then maintain IAS hold. 

With the aid of the GTN's VNAV profile, I manage thrust to comply with the altitude restricitons. At 11,000 ft, I switch from IAS hold to VS so I can reduce KIAS to 250. Once I had 250, I returned to the IAS mode.

nDiqxq5.jpg

I shouldn't have waited for the minimums to switch runways. The turn was too tight!

ubwNut1.jpg

YbRMNOv.jpg

lyWq4i1.jpg

MMSxHds.jpg

FsC7U9n.jpg

cHfywgm.jpg

One last thing before I turn in: I can't seem to get the GPU to work once I finish a flight. I click on it in the config page but it won't stick to the green check mark.

When you start a flight from scratch, it works ok. I'm not sure if I'm doing it properly.

Well, I hope you liked the long post. Hopefully Mark reads about the N1 setting and tell me it's ok LOL.

 

 

 

Edited by Guevorkyan
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9 hours ago, Guevorkyan said:

Hi everyone,

Hi Folks,

THAT has to be one of the BEST PIREPS I’ve ever had the pleasure of reading... Superb job - sir... Charts - tables - comparing real world performance data - and beautiful pictures - who could ask for more... I hope Mark takes a look at the performance data comparisons...

Regards,

Scott

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Great pirep! I’m not at my sim computer at the moment, but I think that on one of the in-sim config screens, perhaps the one associated with Shift -1, there is a note that the modeled engine is the TFE731-40. Perhaps Mark can confirm?

The -40 came Standard on the Falcon 50EX, and is available as a retrofit for older Falcon 50s originally equipped with the -3 engines. The -40 does produce more thrust than the -3 at full power. A Falcon 50, even with the older engines, will climb very quickly when light - Dassault made military fighters before they entered the civil aircraft market with the Falcon 10 and 20, and they strove for high performance in all their designs.

Even on on the heavier Falcon 900s that my employer operates, they will typically reach 10,000 feet within 5 minutes after takeoff from a sea level airport if there are no intermediate ATC altitude restrictions.

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Nice post !  Would love to have your PFPX profile.

Joe

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Santiago - thanks again for sharing - much appreciated.

Joe

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Just received an e-mail indicating that Beta 4.7 has been released and it looks like Mark addressed the %N1 issue.

Falcon 50 Beta 4.7 Updates:

  • 1. New taxi and landing lights. Fixes the bug when fog is loaded. Also has a complete new recipe that makes the 2 lights blend together without over brightness. Also near dusk or dawn its also not over bright.

    2. New flight dynamics. 31% N1 idle. No more sticky taxi. This requires need no power to taxi. 85%-90% N1 to maintain 10,000 altitude to 20,000 altitude. And 93%-98% for high altitudes. This new update is more accurate to real world. And we my improve this over time.

    3. Go Around is now 3800 FPM. This is where you should be for takeoff with our new flight dynamics.

    4. ITT now shows roughly 470C to 875C range. Structual ice adds 100C to ITT gauge 1 and gauge 3. SPR with ITT below 100C will increase 50C to all 3 ITT gauges.

    5. FIxed some of the monitors with backwards map in cabin.

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On ‎12‎/‎8‎/‎2018 at 3:48 PM, JRBarrett said:

I think that on one of the in-sim config screens, perhaps the one associated with Shift -1, there is a note that the modeled engine is the TFE731-40. Perhaps Mark can confirm?

The -40 came Standard on the Falcon 50EX, and is available as a retrofit for older Falcon 50s originally equipped with the -3 engines. The -40 does produce more thrust than the -3 at full power. 

Engines on the Flysimware Falcon 50 are the -3 engines, confirmed by Mark.

The -40 engines have the same take off thrust as the -3 engines, but they are flat rated and hence keep the thrust to a much higher altitude. 

Edited by FDEdev

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Awesome post...  Gah!  I've got to get the sim up and running again!

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Last night I flew from TEB across the pond to Stansted, using the release version.

I don't have the numbers here, as I'm out from home.

TOW was around 36,000lbs, and fuel on board 14,800lbs. The fuel requirement for the route at M.75 was 12,000lbs IIRC.

Three things I observed: First, the N1 on cruise at 41,000ft, TAT -30 and M.75 was 76% again. I was expecting higher as per changelog in 4.8. 

Second, although fuel flow indicators showed numbers really close to the real charts, I don't think it's actually burning that amount. For the 6.7 hours it took to fly the route, in reality I the airplane only burned around 8,000lbs according to the fuel usage box. After the flight, I still had fuel in all the wing tanks (plenty). So there's something off there. 

The fuel flow indicators showed higher (chart-real) fuel burn than the actual (which is too low). According to the actual fuel used, it looks like the average fuel burn was around 400lbs/h per engine along the whole route, which is too low.

Third, the aircraft weight box doesn't work for me. I set the weight using the built-in config in Shift+3 and it translates but doesn't move further as you burn fuel.

 

Edited by Guevorkyan

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Hi Folks,

While in the RW - flying the aircraft as Santiago does would be the only way to gauge proper fuel burn... This being a sim - simply climbing to altitude and looking at the GTN's fuel burn page - should give us a perfectly accurate fuel burn forecast - no ??? Might save some substantial time when trying to tweak the fuel burn parameters ???

Also - IIRC - doesn't the "Air Wrench" tool also give you a predicted fuel burn based on your flight model ?

Great work Santiago - some fantastic testing - seems you're wearing the hat of Chief Test Pilot... Keep at it !!!

:wink:

Regards,
Scott

 

 

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1 hour ago, Guevorkyan said:

Last night I flew from TEB across the pond to Stansted, using the release version.

I don't have the numbers here, as I'm out from home.

TOW was around 36,000lbs, and fuel on board 14,800lbs. The fuel requirement for the route at M.75 was 12,000lbs IIRC.

Three things I observed: First, the N1 on cruise at 41,000ft, TAT -30 and M.75 was 76% again. I was expecting higher as per changelog in 4.8. 

Second, although fuel flow indicators showed numbers really close to the real charts, I don't think it's actually burning that amount. For the 6.7 hours it took to fly the route, in reality I the airplane only burned around 8,000lbs according to the fuel usage box. After the flight, I still had fuel in all the wing tanks (plenty). So there's something off there. 

The fuel flow indicators showed higher (chart-real) fuel burn than the actual (which is too low). According to the actual fuel used, it looks like the average fuel burn was around 400lbs/h per engine along the whole route, which is too low.

Third, the aircraft weight box doesn't work for me. I set the weight using the built-in config in Shift+3 and it translates but doesn't move further as you burn fuel.

 

After you have set the fuel load on the configuration screen, you need to click on the gross weight set button on the counter with your center mouse button. This will set your “total fuel used” button to zero, and enable the gross weight counter to start decrementing once the engines are running. This may affect fuel consumption later on, I’m not sure.

I have not done any long flights yet. Most of my tests have been 600-700 nm legs with about 1.5 hours flying time. I have been using about 3,300 pounds on these short flights, which is quite close to the “book value”.

A TAT of -30 at FL410 is pretty close to ISA. N1 and fuel consumption will be higher at temperatures above ISA, and lower at temps below ISA. 

I typically see about 78 percent N1 at Mach 0.80 cruise at  FL 390 or 400. That may be a bit low, but fuel flow seems quite close. It was about 650 lbs/hr for each engine in cruise. In Beta 4.8, I definitely saw more N1 during the climb phase for a given IAS/Mach than previously, which is more accurate than earlier revisions.

In your previous coast-to-coast test flight, I recall that you mentioned that you had some concerns as to whether you would have enough fuel near the end of the trip, so on that occasion, it seemed that fuel burn out of the wings was working? Perhaps something didn’t initialize properly on your latest flight. Do try the center mouse click on the gross weight setting knob.

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I know Fuel Flow indicators are showing correct numbers as per the performance charts. But in reality, it looks to me that the airplane is not actually burning that amount of fuel, it's burning 50% less than that..

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Fuel needs to burn from the feeders first until they get to 600 pounds and then the feeders will draw fuel from the wing tanks. So they work as they should.

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29 minutes ago, Flysimware said:

Fuel needs to burn from the feeders first until they get to 600 pounds and then the feeders will draw fuel from the wing tanks. So they work as they should.

I know that. And it worked as intended indee. Once the feeders got to 600, the wing tanks started flowing aft.

What I'm saying is that from the fuel flow alone indicated in the gauges, I should have used around 12,000lbs on a 6.7hr trip. But the aircraft only burned 8,000lbs, despite what the gauges said.

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Just now, Guevorkyan said:

I know that. And it worked as intended indee. Once the feeders got to 600, the wing tanks started flowing aft.

What I'm saying is that from the fuel flow alone indicated in the gauges, I should have used around 12,000lbs on a 6.7hr trip. But the aircraft only burned 8,000lbs, despite what the gauges said.

We are checking the fuel burn rate right now based on 1 hour trips and we were off by 250 LBS. We are fine tuning it now. 

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Just now, Flysimware said:

We are checking the fuel burn rate right now based on 1 hour trips and we were off by 250 LBS. We are fine tuning it now. 

Ok!

I will continue testing as well, will pay special attention to the fuel flow gauges and the actual fuel consumption. Maybe it was a one-off.

Again, I burned 4,000lbs less than what the F/F indicated overtime. It could have been me messing around since I flew in Air Hauler and it loads the fuel automatically. But I cross checked the fuel load, and the aircraft weight. I also cross checked through my flight plan, comparing fuel usage to estimated fuel usage at every waypoint.

At TOC, fuel consumption was nearly as expected, but over time and further along the flight plan, the divergence started to broaden. This was a 3,000nm route and 6.7hr trip time, planned for 12,000lbs trip time and 14,800 total fuel. Burning only 8,000lbs @410 and ISA for the duration of the flight seemed really low, my wing-tanks weren't even empty (even less the central wing tank). 

According to the fuel flow gauges, I was burning in average 1,560lbs/h total. But in reality, it was closer to 1,200lbs/h, good for 398 per engine per hour (like a single Metroliner Garrett turboprop engine). That's my point.

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A real quick note after adjusting the cfg file. We found that each hour we tested the fuel burn rate dropped considerably more than we expected but not sure based on real world. This we can't change because the simulator PPH scalar is already pre factored. We can only put a starting value. The 1st hour after climb was 2100 PPH and the 6th hour 1130 PPH.

=================================================================

We increased the ThrustSpecificFuelConsumption slightly and lowered the fuel_flow_scalar as we found the PPH was low compared to the chart.

We then flew at FL430 with a weight of 36,000 LBS and the PPH was at 620 for each engine. The PPH after each hour does not drop as much as the chart shows. 

It took 1680 LBS of fuel to climb to FL430 and 11,300 LBS to fly another 7 hours. 

A total 8 hour flight used 13,300 LBS roughly. So we are happy with the new PPH burn rate.

==================================================================

To test use these settings in the aircraft.cfg.

fuel_flow_scalar = 1.0

ThrustSpecificFuelConsumption = 0.7

We lowered the first value and raised the second value.

==================================================================

Happy flying! This will be in our next update in a few weeks.

 

Edited by Flysimware
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