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Old 07-09-2017, 07:54 PM   #1
jackmckay
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Default FCS disengage safe airspeed?

Dear ED.

What is maximum safe IAS for FCS disengagement levels 1 and 2 without wing structural failures on max AoA. How Su27 wing accumulates structural damage and at what IAS and AoA?

Thank you.
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Old 07-10-2017, 07:05 PM   #2
WildBillKelsoe
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400 kph iirc


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Old 07-10-2017, 08:43 PM   #3
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Quote:
Originally Posted by jackmckay View Post
Dear ED.

What is maximum safe IAS for FCS disengagement levels 1 and 2 without wing structural failures on max AoA. How Su27 wing accumulates structural damage and at what IAS and AoA?

Thank you.
Stage 1 & 2 of the ACS aren't modelled in the DCS Su-27, it's either in full automatic or full direct mode. IIRC as Wild Bill said the maximum disengagement speed is 400 Km/h, though I'd be very careful disengaging it at anything over about 350.
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Old 07-11-2017, 12:56 AM   #4
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That means that DCS safe "Cobra" can only be done below 400km/h?
- Question: At what fuel fraction and 2xR73 configuration Su27 have P/W ratio over 1?

Last edited by jackmckay; 07-11-2017 at 01:02 AM.
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Old 07-11-2017, 07:26 PM   #5
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Quote:
Originally Posted by jackmckay View Post
That means that DCS safe "Cobra" can only be done below 400km/h?
- Question: At what fuel fraction and 2xR73 configuration Su27 have P/W ratio over 1?
Not sure what the maximum safe speed is, but I've never tried it above 400 Km/h.

As for the T:W ratio:

Su-27 empty weight = 16,380Kg
Weight of R73 = 105 so 2 = 210Kg
AL-31F thrust = 7,575Kg dry, 12,500Kg full reheat.
2 engine thrust: 15,160Kg dry, 25,000Kg full reheat.
Empty weight + 2 x R-73 = 16,590Kg

So, at 100% RPM with no afterburner your T:W ratio will never be above 1:1. With full afterburner your T:W will be 1:1 at 89% fuel load, with only 2 x R-73 missiles loaded.
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Old 07-11-2017, 07:36 PM   #6
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You can do cobra below 600km/h with no arnaments. With arnaments I haven't tested.
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Old 07-12-2017, 06:04 PM   #7
WildBillKelsoe
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Quote:
Originally Posted by DarkFire View Post
As for the T:W ratio:

Su-27 empty weight = 16,380Kg
Weight of R73 = 105 so 2 = 210Kg
AL-31F thrust = 7,575Kg dry, 12,500Kg full reheat.
2 engine thrust: 15,160Kg dry, 25,000Kg full reheat.
Empty weight + 2 x R-73 = 16,590Kg

So, at 100% RPM with no afterburner your T:W ratio will never be above 1:1. With full afterburner your T:W will be 1:1 at 89% fuel load, with only 2 x R-73 missiles loaded.
Its on wiki
https://en.m.wikipedia.org/wiki/Sukh..._.28Su-27SK.29

56% internal fuel
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Fat T is above, thin T is below. Long T is faster, Short T is slower. Open triangle is AWACS, closed triangle is your own sensors. Double dash is friendly, Single dash is enemy. Circle is friendly. Strobe is jammer. Strobe to dash is under 35 km. HDD is 7 times range key. Radar to 160 km, IRST to 10 km. Stay low, but never slow.
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Old 07-15-2017, 12:12 AM   #8
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Thank you WildBillKelsoe and DarkFire.
That means that Flanker with 2xR73, airspeed below lets say 500km/h, with fuel less than 50% and FCS off should accelerate in turn and even climb vertically if AoA is below lets say 25deg? Right?

Last edited by jackmckay; 07-15-2017 at 12:15 AM.
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Old 07-15-2017, 12:42 AM   #9
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ah yes, the mythical vertical climb. thrust will drop as you climb into thinner air, so you will never be able to maintain a vertical climb.
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