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Old 02-28-2018, 06:30 PM   #181
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Originally Posted by Maverick Su-35S View Post
Now, (a bit absurd one will find it), the F-15 turns better than the Flanker at both low (full aft stick full AB) and high speeds (around the best turn corner). For short, with both planes fueled the same (30% fuel), the F-15 completes the fastest (full aft stick from around corner speed) 360 turn in about 14.4 seconds, while the Flanker in no less than 15.8. How did this happen?
I'm not sure if this has been pointed out... and I'm otherwise not getting involved in a debate about flight models..

But the Flanker's fuel is measured in tonnes. Full capacity is 9.4 tonnes, or 18800 lbs.

F-15C's internal fuel capacity is measured in lbs and maxes at something like 13,400 lbs or 13, 800 lbs.

Hopping in both aircraft and fueling them both up to 30% is not "fueled the same".

Flanker is carrying 5,640lbs of fuel.

F-15c is carrying 4,140lbs of fuel. How much this would effect your "testing" I won't go as far to assume.. but there's 1500lbs difference in fuel weight there. Seeing as we're talking about the accuracy of an FM.. perhaps it'd be worth running your test with accurate fuel measurements.
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Old 02-28-2018, 06:46 PM   #182
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Originally Posted by Alfa View Post
Someone once said that "the Su-27 carries its external fuel internally" .
That certainly calls for a in soviet russia joke
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Old 02-28-2018, 07:22 PM   #183
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We're good now, Vatikus provided exactly the information required.

Basic fueling would be 5220kg, which would result in a 50% fuel weight of 2610kg or 5700lbs, or 28% of total fuel.
The implications on maneuverability here are fairly big.

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Sorry but I only have my phone and tablet until saturday, and I can not upload anything from those for some reason.

The pages I have found interesting are 13/269 14/269 (limitations) 20/269 (flight envelope) and 51/269. Please have a look at those.

I think chapter 1 (limitation) and chapter 4 (maneuvers?) are the most relevant for us here, so if parts of it could be translated, it would be great
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Old 02-28-2018, 07:24 PM   #184
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In this case, where we have the charts of the two aircraft, the only valid measurements are that of DCS FM vs. the aircraft's data.

From there on, any comparisons between the two aircraft have value in DACT knowledge, not in the judging of one aircraft's performance based of that of another.

So the comparisons can be made for any desired purpose OTHER than making claims that one or both FMs are somehow wrong.

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Originally Posted by Headwarp View Post
F-15c is carrying 4,140lbs of fuel. How much this would effect your "testing" I won't go as far to assume.. but there's 1500lbs difference in fuel weight there. Seeing as we're talking about the accuracy of an FM.. perhaps it'd be worth running your test with accurate fuel measurements.
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Old 02-28-2018, 07:43 PM   #185
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Quote:
Originally Posted by GGTharos View Post
In this case, where we have the charts of the two aircraft, the only valid measurements are that of DCS FM vs. the aircraft's data.

From there on, any comparisons between the two aircraft have value in DACT knowledge, not in the judging of one aircraft's performance based of that of another.

So the comparisons can be made for any desired purpose OTHER than making claims that one or both FMs are somehow wrong.
Personally, again I'm not here to debate FM. But perhaps anyone that is here to provide input on FM or even just comparison data, along with required documentation, can at least use simple math if wanting to test by fuel weight to actually make the fuel weight equal as "fueled the same" would imply.

Also making such an argument based on their own testing, might want to provide video evidence with instrument flight as empirical proof that one can perform an 100% coordinated turn in both aircraft, under the same atmospheric conditions.

But more or less was just pointing out that claiming 30% of two different values is equal pretty much skews any test results that turned this into a 21 page thread.
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Old 02-28-2018, 07:51 PM   #186
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You are right about that. Some have suggested that aircraft should be fueled to 'same endurance' for testing.

Personally I think none of that should be done, and instead do the charts for each aircraft at different weights etc, then overlay them. Then you'll have data for any circumstances.

In any case, this thread was all about FM and who out-turns who. In the end, the flanker turns just fine - it's quite deadly when flying it in order to do what it was meant to do, instead of lab tests
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Old 02-28-2018, 08:26 PM   #187
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ironically enough the deeper you go into these comparisons the less practical relevance they end up having.
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Old 03-01-2018, 02:36 AM   #188
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That certainly calls for a in soviet russia joke
Heh yeah - it sounds contradictory, but there is some truth to it and, as per Yo-yo's remark, it also sounds like thats exactly how it is regarded .
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Old 03-01-2018, 03:07 AM   #189
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Quote:
Originally Posted by Headwarp View Post
I'm not sure if this has been pointed out... and I'm otherwise not getting involved in a debate about flight models..

But the Flanker's fuel is measured in tonnes. Full capacity is 9.4 tonnes, or 18800 lbs.

F-15C's internal fuel capacity is measured in lbs and maxes at something like 13,400 lbs or 13, 800 lbs.

Hopping in both aircraft and fueling them both up to 30% is not "fueled the same".
Thats true and, as mentioned, the large internal capacity of the Su-27 is in part down to a design decision not to employ external drop tanks, but...

Quote:
Flanker is carrying 5,640lbs of fuel.

F-15c is carrying 4,140lbs of fuel. How much this would effect your "testing" I won't go as far to assume.. but there's 1500lbs difference in fuel weight there. Seeing as we're talking about the accuracy of an FM.. perhaps it'd be worth running your test with accurate fuel measurements.
...you would normally also try to scale the fuel capacity to engine consumption. The Su-27 has more engine power than the F-15C and thus likely a higher consumption rate, so it might actually need that extra fuel to achieve the same endurance.

But for trying to evaluate the accuracy of the FM against official performance charts, it is of course necessary to assign the exact fuel state used in these.
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Old 03-01-2018, 05:09 AM   #190
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Quote:
Originally Posted by Alfa View Post
Thats true and, as mentioned, the large internal capacity of the Su-27 is in part down to a design decision not to employ external drop tanks, but...



...you would normally also try to scale the fuel capacity to engine consumption. The Su-27 has more engine power than the F-15C and thus likely a higher consumption rate, so it might actually need that extra fuel to achieve the same endurance.

But for trying to evaluate the accuracy of the FM against official performance charts, it is of course necessary to assign the exact fuel state used in these.
Regardless of consumption, I would assume if you wanted to compare the turning performance of the airframes from Aircraft A, and Aircraft B, any fuel added is an addition to the airframe. To give one more weight in fuel than the other is certainly going to effect its flight characteristics.

It's not the same as comparing flight longevity, and then that's not even considering whether or not there is a desire to compare aircraft using a set gross weight and what it would take to achieve equal numbers there.

That being said.. I'm not an aeronautical engineer or anything. So I'll not argue further, but since the subject was the turning speed of two aircraft and not the amount of time either is spending in the air.. seems to me equal amounts of fuel would only be fair. 1500lbs isn't exactly light. Think 3 gbu-12's and how a plane is effected dropping just one of them...minus the drag they would induce.
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