Forum: F-16 Procedures

Hi

On two different video's showing vipers on ramps. I have seen a rapid movement of the flaperons and stabilators +/- 5 degrees for 3 seconds or so most likely on startup. Something which I did not observe on other video's of viper startups.

Is this an indication of an error in the FLCS? Or was the pilot simply checking the controls?

F-16.net Sponsor

You might see them move on startup as hydraulics come up, but most likely you will see the surfaces move as the pilot selects the FLCS BIT or when the pilot cycles the control surfaces, so no error.

Cheers,

ViperDude

Thanks..
clears that up.

(I second Brother Dude's comments, and will add...)

When the hydraulics are cold, they can have a delay in reaction or the cold fluid will resist flowing; this can cause FLCS BIT faults.

"Stirring" the flight controls around for a while helps warm things up by getting the fluid to do some 'work' and circulate through the system.

I'd say it's what your seeing, just after start up before the FLCS BIT is accomplished.

You'll see the controls 'stirred' much more during cold weather. (Sometimes more than once if the FLCS BIT fails)

Heavy construction equipment will often do this too; moving things through their range of motion 'working' the hydraulic system to warm it prior to straining the system with a load. Cold lines and other components could be blown or damaged by the cold fluid. Letting a machine warm up somewhat during cold weather will help prolong component life and reduce false (un-needed) maintenance.

TEG

Some guys (and I think all FCF’s) will cycle the controls during JFS max motor prior to lighting off the engine.

Stabs, Flaperons, and Rudder all should move freely without any generators on-line.

Flight control warm-up is quite a few minutes after engine start … after SEC and EPU bleed air mode checks.

If you have a link to the video, I’ll tell you exactly what’s happening.

Thank you gentlemen...
In layman's terms..
The jet is stretching its legs before it goes.. si?

Salute!

The early models with the analog FLCS had a 40 second BIT that slammed the control surfaces all over the place. And that was the abbreviated FLCS test, not the ones we did for an FCF.

Nowadays, much faster and more benign.

The original BIT measured rates and deflection angles and all kindsa things. LEF's also moved. We did other things while it was in progress, like typing!!!! no data transfer cartridges in those days, heh heh.

After all was done, we old farts kept our stone age habits and did things like "left stick, left flaperon up, right down, a tad of left rudder", and "forward stick, left aileron, right rudder" and so on.

Gums sends....

Gums wrote:

After all was done, we old farts kept our stone age habits and did things like "left stick, left flaperon up, right down, a tad of left rudder", and "forward stick, left aileron, right rudder" and so on.

That's because you weren't about to let some newfangled airplane tell you it was functioning ok, you wanted to see for yourself to make sure- like a good(and smart) pilot ought to. That's why you are here to share your aviation wisdom and knowledge with us! Thumb

Great respect to you, Sir. Salute

Posts by Gums, The Engine Guy, and several others are the reason I keep coming to F-16.net! Respects!

To any of the old analog guys: Gums mentioned how the jet got bounced around during the FLCS BIT. Did it ever get so bad that it affected the alignment of the INS? Or was the platform isolated well enough to guard against that?

With FCNP in block 15’s and below, the only thing that normally screwed up INS alignment was a CC kicking one chock out early and the jet rolls forward a few inches. (Pisses everyone off because it takes so long for realignment) With EGI in block 30’s I haven’t seen any movement issues that throw off the alignment.

But no ... FLCS self test did not throw off the alignment, even on a very windy Eddy day.

Thanks gums.. that summed it up..
It was an early block I saw.. and true to your description..the control surfaces seemed to be going bezerk.
As an afterthought.. is the same applicable to the Euro MLU's?.. With the "re-furbished" interior.

Yup, a 40 second analog self test would cause the surfaces to appear like they are going berserk! Laughing

Especially if it passes!

Lets slow it down a bit, with a lot of the self-test cut out!

http://www.youtube.com/watch?v=fzgF0kOqSW4

Mucho Gracias VVet.

Salute!

Thanks for the video, Vark-breath!

Made me cry, and I liked the loadout (except for those nasty tanks, heh heh).

For the newbie- note the stabs flicking up and down a bit as he taxied out. Doggone FLCS was trying to achieve commanded Gee. I tellya, those control surfaces moved ALL THE TIME. Going thru gusts on low levels, taxiing, you name it.

That looked a newer motor - a GE ?

The INS aligned quicker and better than the one we had in the SLUF. Also drifted a lot less. Never had any problems with bumps and such.

Ahhhh maaaan, I miss those days, sniff, sniff......

Merry Christmas to all!

Gums sends...

Forum: F-16 Procedures

Rapid movement of control surfaces during startup