Flutter of control surfaces of the F-16?

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saberrider

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Unread post06 Jan 2018, 15:29

Does the F-16 have flutter of control surfaces ? If it has in what speed regimes?
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Patriot

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Unread post06 Jan 2018, 18:33

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johnwill

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Unread post06 Jan 2018, 20:09

No, the F-16 does not have flutter of control surfaces. The article says that control surfaces might be used to damp some forms of flutter. Here's the true story. In 1977 and 1978, during Full Scale Development flight testing, a low level sustained antisymmetric pitch oscillation was discovered for one very heavy external store loading at a narrow mach range. The loading was a normal download of 4 CBU weapons mounted on MER ejector racks at stations 4 and 6 (the most inboard wing hardpoints). The full load was two forward CBUs and two aft CBUs on the MER. The normal drop sequence for a MER is for an aft weapon to go first, leaving two weapons forward and one aft on the MER. The resulting oscillation was uncomfortable but not dangerous. Because it was sustained, not divergent, the oscillation was not flutter.

In any event, The problem at that time went away, since the MER was not used in operational service on the F-16 as far as I know. I could be wrong. Reading the article, it sounds like there was some effort solve the problem about 25 years later. I don't know if that capability was ever installed.
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basher54321

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Unread post06 Jan 2018, 20:58

:notworthy:

Another mystery - I have never seen any MERs on F-16s outside of the FSD photos of 75-0746 although they are listed in early A documentation - maybe I assumed carpet bombing went out of fashion with better bombing systems.

So they were actually certified on the F-16 despite the weight (6 x MK-82 each) and lack of use?
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saberrider

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Unread post06 Jan 2018, 22:40

I was asked about "control surface's": flaperons ,slab , rudder and LEF's for fluttering @ totally envelope of flying. Because in my Sim I get flutter of the flaperons @ 480-500knots.I don't know why? I believed is because FBW try to stop aggressive behavior in acc. rolling.
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tailgate

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Unread post07 Jan 2018, 04:08

No flutter in the 16 flight controls that I ever saw. I never saw anything carried on 4 and 6 except gas bags. You start loading the 16 down without gasbags and your combat radius becomes very small.
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johnwill

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Unread post07 Jan 2018, 05:31

saberrider wrote:I was asked about "control surface's": flaperons ,slab , rudder and LEF's for fluttering @ totally envelope of flying. Because in my Sim I get flutter of the flaperons @ 480-500knots.I don't know why? I believed is because FBW try to stop aggressive behavior in acc. rolling.


I suspect your sim FCS is nowhere near the real deal in terms of filtering, frequency response of the control surface actuators, mass and stiffness properties of control surfaces and backup structure, airloading, and so on. To repeat, F-16 control surfaces do not flutter.

tailgate has another reason the MER was cleared at 4/6 for 6-MK-82, 6-MK-82R, and 4-CBU, but never used operationally. The 4/6 hardpoint was needed for fuel. That's in addition to the oscillation problem, indicating the MER was too flexible. Hugh speed movies of store ripple ejection sequences were scary, with the MER looking like a wet noodle.
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saberrider

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Unread post07 Jan 2018, 07:41

Thanks to all .That's why I ask so many things because rigging is not near the reality. The way the controls are blended in do not replicate the real deal e.g. in Sim flaps in To/L go up and past 0 line if aileron's is used for rolling , then rudder inputs don't fade at high AOA and now flutter is present.
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basher54321

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Unread post07 Jan 2018, 14:28

thank you

@ tailgate
Israel in 1982 used all 4 pylons for A-G although the only case for the USAF I am aware of was apparently this in Desert Storm (401st?):

4xMK84_desert_storm_4.jpg



Lockheed Martin had a recent demo pic for the F-16V with CFTs on their site and it looks like MERs on 4/6 was wondering if it was photoshopped:

Block72.jpg
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Unread post07 Jan 2018, 15:30

Alike MERs the same reason why the Viper dont get cleared for gun pod was lack of stiffness of the hardpoint #5 which wasnt originally designed for loads resulting from a fire recoil.. which affected directly the accuracy of the fire . True or not?

https://youtu.be/wNcZQQ6Fv2Y
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tailgate

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Unread post07 Jan 2018, 17:42

basher54321 wrote:thank you

@ tailgate
Israel in 1982 used all 4 pylons for A-G although the only case for the USAF I am aware of was apparently this in Desert Storm (401st?):

4xMK84_desert_storm_4.jpg



Lockheed Martin had a recent demo pic for the F-16V with CFTs on their site and it looks like MERs on 4/6 was wondering if it was photoshopped:

Block72.jpg


Greets Basher, that first pic I see Shaw jets, 17th and 33rd to be exact. Those were probably operating from KKMC hitting targets in Kuwait ( 10 Minute fight ). But that was not a typical load operationally. Jet doesn't have long legs with that config. Not sure, but those could also be alert jets for CAS call ups.

Not familiar with the second pic as far as version. I would gather a guess that those CFT's give the same capability/logistical point as 370 tanks? In any case, frees up some space. But I'll tell you, just looking at that jet, that's allot of drag hanging there and I'm positive they would have allot of tank time getting somewhere.
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tailgate

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Unread post07 Jan 2018, 17:54

Oops....Israel probably would be the exception to this rule as talking with their pilots,they are 5 minutes from anything......I flew with them when we were in Incirlik and The 16's I saw were three baggers back then so don't know if even they do it as a standard op procedure.

( I meant to say flew along side them in joint exercises)
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basher54321

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Unread post07 Jan 2018, 22:07

Patriot wrote:Alike MERs the same reason why the Viper dont get cleared for gun pod was lack of stiffness of the hardpoint #5 which wasnt originally designed for loads resulting from a fire recoil.. which affected directly the accuracy of the fire . True or not?



See end here for some reasons:
http://www.f-16.net/f-16_versions_article18.html


I thought the GPU-5 was actually used briefly in Desert Storm:
viewtopic.php?f=18&t=3921&p=42493&hilit=PAVE+CLAW#p42493
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basher54321

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Unread post07 Jan 2018, 22:18

tailgate wrote: Not familiar with the second pic as far as version. I would gather a guess that those CFT's give the same capability/logistical point as 370 tanks? In any case, frees up some space. But I'll tell you, just looking at that jet, that's allot of drag hanging there and I'm positive they would have allot of tank time getting somewhere.


thanks - bit less in terms of qty - but the big reduction in drag might offset some of that - if you are not carrying 12 x MK-82s on MERs :D
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tailgate

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Unread post07 Jan 2018, 23:06

We would run down to Avon from Moody carrying two MK84's on BAI training. Just those two made a difference in acft performance.

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