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Veteran Joined: Mar 24, 2007 Posts: 379 Status: Offline

Gums, with you all the way on the power supply screwup - totally inexcusable. Sadly, it won't be the last one. That's what happens when you have so much electric stuff all over the airplane - people who are not airplane types. To them, the part they are working on is just another computer or power supply or relay or whatever. We have them in structures too, folks who couldn't tell you the difference between an airplane and a bridge. Just another piece of structure to them. They just don't realize the mistakes they make end up as smoking holes.

Here's a thought. It's not just contractors who have people like that, USAF has them too, else why would they approve such a design? So-called technical experts in the services have to approve everything the contractors build.

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Veteran Joined: Jan 11, 2004 Posts: 258 Status: Offline

Gums wrote:

Salute!

Well, hell!

I only did the trick on Block 1, 5, 10 and 15's.

Could it be that they changed the ISA's?

We have to find a Guard unit with really old jets to try this out.

The lock was mechanical, and you could feel the thing when it locked.

Meanwhile, we're looking for some help from a troop that has older jets.

Gums sends ....

Gums I worked Block's 10,15,25 and 42 starting in 1996 at the 162nd and I can tell you at that time I never experienced a difference as far as ISA's go between the different blocks. We used different books to order ISA's but they were all the same part# and were absolutely interchangeable between the blocks. I never experienced a mechanical lock on the ISA that I can remember.

Pete

here are 2 nice pics on the rotary actuators and the torque shafts. Replacing a LEF sucks. Laughing

VarkVet wrote:

Correct … the asymmetry brakes are an electrically actuated mechanical lock (fun to rig) designed to automatically shut the LEFs down if the flaps attempt to split.

Don't remind me, can take all afternoon to rig them. Laughing

Elite Joined: Apr 26, 2004 Posts: 1175 Status: Offline

Kaasjager. wrote:

VarkVet wrote:

Correct … the asymmetry brakes are an electrically actuated mechanical lock (fun to rig) designed to automatically shut the LEFs down if the flaps attempt to split.

Don't remind me, can take all afternoon to rig them. Laughing

How many folks here used a paper clip to rig them when they found out support didn't have the rigging tool?

Also Gums I worked on block 5's, 10's, 25's, 30's and 50's and I may be wrong but all the ISA's worked the same way. With that said I still think it is a liquid lock rather then mechanical, prove me wrong and next time I'm down south I'll buy you your favorite liquid......!!!!!

Purple

Last edited by Kaasjager. on Jun 03, 2008 - 03:45 PM; edited 1 time in total

Purplehaze wrote:

Also Gums I worked on block 5's, 10's, 25's, 30's and 50's and I may be wrong but all the ISA's worked the same way. With that said I still think it is a liquid lock rather then mechanical, prove me wrong and next time I'm down south I'll buy you your favorite liquid......!!!!!

Purple

I think i have a "simplified" drawing of an block 15 ISA somewhere around in a F-16 Pneudraulics training book. would that help you guys?

double post. Embarassed

Elite Joined: May 26, 2005 Posts: 1093

Awesome pics!

Elite Joined: Jul 11, 2007 Posts: 666 Status: Offline

Just a thought here but you know when you push the stabs/flaperons up I wonder if the hydraulic fluid equalizes on both sides of the ISA and it feels like they lock. In reality it’s only the fluid in the lines. I’ve never tried to pull one down after pushing it up so this is just a theory.
But this has nothing to do with the LEF operation.

Elite Joined: Oct 30, 2006 Posts: 627 Status: Offline

For servo actuators …I looked it up in the GS, self-contained spring in servo ISA commands the actuator to the neutral position when hydraulics (A&B) is below 720psi.

I guess that’s why you can only push them up to the point of the index marks and no further. They won’t pull down unless you manually push/pull the input rod on the control valve, or droop again after time. This is all liquid lock.

So Gums is correct except for fingerlocks.

Elite Joined: Jul 11, 2007 Posts: 666 Status: Offline

VarkVet wrote:

For servo actuators …I looked it up in the GS, self-contained spring in servo ISA commands the actuator to the neutral position when hydraulics (A&B) is below 720psi.

I guess that’s why you can only push them up to the point of the index marks and no further. They won’t pull down unless you manually push/pull the input rod on the control valve, or droop again after time. This is all liquid lock.

So Gums is correct except for fingerlocks.

That's good to know, keep someone from pulling till they have two hands full of flap pieces and the flap sill in the up position. Shocked

Elite Joined: Oct 30, 2006 Posts: 627 Status: Offline

So that leaves one unanswered question. If you have 0 to 720 psi on both A&B systems and the flaperons and stabs float up to the neutral position and stop. Then what?

Elite Joined: Apr 26, 2004 Posts: 1175 Status: Offline

How about Gums and I are correct and you all owe us liquid refreshment?

Elite Joined: Dec 16, 2003 Posts: 798 Status: Offline

Salute!

Luv you all. Great stuff here, trust me. If our stuff ain't recorded before we get completely senile, somebody will invent a fairy tale that becomes "history".

OK, "finger locks" a "feeling" I always had when pushing up a dead slab and it locked in both directions.

I'll buy in on a hydraulic lock of some kind whereby the pressure would be equal on each side of the actuator piston. I'll hunt down the stuff I have from '79 and see if there's an explanation.

All I know is I could push up on a drooping surface and all of a sudden it went "click" and froze.

Got to root around for some of those old GD documents.

Gums sends ....

Gums wrote:

All I know is I could push up on a drooping surface and all of a sudden it went "click" and froze.

It went click? Never had that happen, weird.

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Forum: F-16 Design & Construction

Ok so LEFs, how are they actually operated?