Operational Performace Comparison: Viper, Beagle, and Stubby

The F-35 compared with other modern jets.
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sprstdlyscottsmn

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Unread post06 Jun 2018, 20:36

splittingatoms wrote:How does an F-35A compare in this scenario, assuming its internally loaded and has a similar fuel state? Does a quick hit of burner and then limited mil-power "supercruise" compare favorably? I won't presume to dictate the best scenarios...you're far better than I. I'm just interested to see the real world implications of a clean airframe and high fuel fraction.

I don't have an updated F-35A model yet. My previous model shows a full Mil dash reaching 1.048M and using 2,300lb fuel over 10.1 minutes to cover the 100nm. AB dash takes 7.95 minutes, 4,461lb fuel. Again, my F-35A model is less accurate than my F-15E model right now.
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Unread post07 Jun 2018, 23:47

Fixed my Post Stall effects to better simulate the "flat plate" drag of an aircraft at high AoA. The Strike Eagle is heavy too. Too heavy.
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Unread post02 Jul 2018, 13:25

You need to get a copy of the new AIAA tech paper: "F-35 Aerodynamic Performance Verification"; I'm skimming it now and it appears to have a fair bit of F-35 flight test data, including altitude vs mach flight envelope charts, lift coefficient vs aoa charts, fuel flow vs mach number, etc; a lot of the charts don't specify which variant they're talking about, and the charts generally don't have their axis fully labelled, but they do show curves and test points for specified altitudes, airspeeds, etc on grids whose intervals, etc can be estimated.
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Unread post02 Jul 2018, 14:04

Dragon029 wrote:You need to get a copy of the new AIAA tech paper: "F-35 Aerodynamic Performance Verification"; I'm skimming it now and it appears to have a fair bit of F-35 flight test data, including altitude vs mach flight envelope charts, lift coefficient vs aoa charts, fuel flow vs mach number, etc; a lot of the charts don't specify which variant they're talking about, and the charts generally don't have their axis fully labelled, but they do show curves and test points for specified altitudes, airspeeds, etc on grids whose intervals, etc can be estimated.


I can't find it using google scholar. Can you show us the link please?
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Unread post02 Jul 2018, 14:30

https://arc.aiaa.org/doi/pdf/10.2514/6.2018-3679

Without buying it you can't really see much; I'm hesitant to post the full thing, because when you buy and download a copy it has your membership details (like full name) attached to the document (which I can remove from the pages, but I'm not 100% certain there isn't metadata tagging me in it).

Anyway, here's some of the charts - the flight envelope one appears to resemble an F-16C (with an F100-PW-229) with a gross weight of about 30,000lb and a DI of something like 70.
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Unread post02 Jul 2018, 15:16

In part of the document there's also a little chart included as part of a diagram; zoomed in it appears to show an F-35 E-M chart. The chart comes from a Figure outlining the process of calculating F-35 flight performance data, so AFAIK it's not based on flight test data, just wind tunnel, propulsion testing, etc data from early / mid stages of SDD.

I don't know what gross weight it represents, I don't know which F-35 variant it represents, etc, but I still think it's interesting:

What I'm seeing here is a minimum turn radius of a little over 2000ft (achieved between Mach 0.3 and Mach 0.7), a max instantaneous turn rate of about 20 deg/s at Mach 0.7 and +8Gs, with a specific excess power of -2500ft/s. Max sustained turn rate is shown at about 12 deg/s at Mach 0.8, +6Gs and a turn radius of something like 4250ft.

Again, there's a lot of unknowns about what exactly we're looking at here, but maybe one of you might be able to deduce some additional details from what we're seeing here.
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F-35 E-M Chart.png
From "F-35 Aerodynamic Performance Verification" - AIAA 2018
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Unread post02 Jul 2018, 15:40

What I see is that it represents an A model based on the 9G limit. I see that it does not do 9G to corner so it has a tapering feature similar to the F-16. If the Envelope Chart also shows in A model, then it seems as though the E-M chart represents an altitude of ~19,000ft based on ultimate speed (just past 1.4M) but with a higher Drag Index than the envelope chart (1.25M at Ps-0 for EM vs ~1.29M at Ps=0 for Envelope) but at a lighter weight than the Envelope chart (min speed of 0.2M in E-M vs min speed 0.25M in Envelope).
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Unread post02 Jul 2018, 17:01

Wait! Cruise at Mach 1.4?
What does PA cruise mean?
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Unread post02 Jul 2018, 17:10

gta4 wrote:Wait! Cruise at Mach 1.4?
What does PA cruise mean?

Don't get hung up on it. Think of it as measuring the fuel flow while at the throttle setting needed to sustain that speed and altitude.
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Unread post02 Jul 2018, 18:05

The se[ value at 19000 ft is amazing.
Accurate prediction 2 year ago:
F-35 will have very good subsonic SEP
viewtopic.php?f=55&t=52510
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Unread post02 Jul 2018, 19:48

gta4 wrote:Wait! Cruise at Mach 1.4?
What does PA cruise mean?


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Unread post02 Jul 2018, 19:57

"...B. Test Matrix
The F-35 Aerodynamics and Propulsion teams entered the flight test phase of the SDD program with a high-fidelity
wind tunnel, analytical database. Extensive work was accomplished to ensure that all forces and moments identified
in the force and moment bookkeeping system were well-defined from wind tunnel testing and CFD. This was
particularly important when objectives were difficult to achieve from testing. The comprehensive nature of the
preflight databases was key to successfully verifying aircraft performance requirements with a minimal matrix of
flight test maneuvers.

The matrix of dedicated aircraft performance flight test maneuvers was designed to minimize required test flights.
At the same time, it continued to provide the data necessary to verify the KPP performance requirements and validate
the performance databases for all phases of flight. The goal was to validate a credible collection of the databases that
formed the basis of the performance products provided to the operator (e.g., flight manual, pilot checklist, performance
on the glass). The IFTPWG balanced fidelity in the final databases with the cost of testing and analysis. Its members
were constantly evaluating and refining the test matrices due to programmatic pressure to reduce flight test costs and
shorten the schedule. In the end, the number of dedicated test points flown for any one variant was roughly half the
number used for previous fighter aircraft. Table 2 summarizes the test points for clean configuration...."
&
"...Aerodynamics data for the aircraft in an up-and-away configuration (i.e., gear up) were standardized to the nearest
database breakpoint Mach number, 36,089-foot pressure altitude, a constant center of gravity, and a set of engine
operating parameters generally consistent with cruise conditions. The altitude serves as the baseline condition for the
aerodynamics database. Aerodynamics data for the aircraft in a powered-approach configuration (i.e., gear down)
followed that process but was modified due to the difference in typical operating altitudes between an up-and-away
and a powered-approach configuration; the latter occurs nearer to sea level so that sea level serves as the baseline for
powered-approach configuration aerodynamics. All aerodynamics standardization was completed holding test α
constant because the databases are a function of α, rather than of CL ..."
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F-35 Table Clean-aircraft dedicated performance maneuvers.gif
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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Unread post03 Jul 2018, 02:59

Okay, so I took the last few weeks off to help a board member develop some turn performance stuff, but now I am back at it. Examples of metrics being looked at currently are "Escort gone wrong" a co-direction, co-speed, closest altitude, 3-9 break into each other from half a mile. Both parties are executing a 180 and firing along the way. I will be scoring the odds of no one dies, red force only dies, blue force only dies, and both parties die. I will also do a BVR joust where I will be looking at the same odds only there will be no evasive maneuvers as the complexity goes through the roof. I will also to a 3-9 cross from 1/4 mile at the end of the joust into a break. The aircraft to include seem to change monthly, with the retirement of the Hornet, the funding of Block III- Super Hornet, the sale of the F-16V. BTW, I will be representing the most advanced versions of the aircraft found around the globe, meaning I will need to see what I really need to change to turn an F-15E into an F-15SA. Hmm, does this mean I still include Swiss F/A-18s?

*EDIT* It takes a long time to validate a performance model right now, between 20-40 hours. Then another 10 or so to run the model through the mission sets. I am halfway through F-15E mission sets and I don't know what will change to make it an F-15SA. I am already assuming APG-81 and EPAAWS. I'll have to look back at an old comparison I did to see what the impacts of the F110 will be.
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Unread post03 Jul 2018, 08:12

sprstdlyscottsmn wrote:What I see is that it represents an A model based on the 9G limit. I see that it does not do 9G to corner so it has a tapering feature similar to the F-16. If the Envelope Chart also shows in A model, then it seems as though the E-M chart represents an altitude of ~19,000ft based on ultimate speed (just past 1.4M) but with a higher Drag Index than the envelope chart (1.25M at Ps-0 for EM vs ~1.29M at Ps=0 for Envelope) but at a lighter weight than the Envelope chart (min speed of 0.2M in E-M vs min speed 0.25M in Envelope).


Nice note; for comparison, here's an F-16C (F100-PW-229, GW 22,000lb, DI=0) at 20,000ft:

Image

That's <9 deg/s sustained and 17.1 deg/s instantaneous vs ~12 deg/s and ~20 deg/s.

Also, maybe I'm missing something, but doesn't the envelope show a min speed of about Mach 0.15 rather than Mach 0.25?

That would mean that the E-M chart F-35A is both draggier and heavier than the envelope aircraft, which suggests even greater performance (as the envelope should be newer / real world data vs old calculated semi-real world data in the E-M chart; it's also unlikely that the envelope aircraft is an F-35B or F-35C if it's lighter and less draggy than an (albeit combat loaded) F-35A).
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Unread post03 Jul 2018, 08:40

Dragon029 wrote:]

Nice note; for comparison, here's an F-16C (F100-PW-229, GW 22,000lb, DI=0) at 20,000ft:

Image

That chart is for Mil power, Max AB look like this
Capture.PNG

So comparing F-35 and F-16 F-110 GE129 ( DI=0)
ITR = 20°/s for f-35 and 17.4°/s for F-16
STR = 12 °/s for f-35 and 12.5°/s for f-16
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