Hi folks,

I was bringing my #1 son home last Friday from NCSU.  He's an engineering major, 3rd year.  He was telling me what one of his professors said in class.  I laughed 'til I was sore when I heard it, and he argued with me about it, because he thinks the prof knows everything.  Before I tell you the story, he found a reference to it in the prof's Web notes: "Globe and Mail, 1991."  So its got to be true, right?  [;)]

The story goes like this:  The F16 was one of the first fly-by-wire planes, and one of the early prototypes had a serious bug in its software.  If the plane was flown from the northern hemisphere to the southern hemisphere, it would flip over when it crossed the equator (i.e. fly on its back.)

Its a very funny idea.  I think its bogus because, although the F16 IS fly-by-wire, when it was designed there was no internal system that would tell the plane where it was on the earth.  At least, I don't know of a way that the plane would know when it passed over the equator into the souther hemisphere.  F16's were designed in the early 70's, and GPS is an invention of the 80's.

What do you all think?  If you think this is TRUE, please provide a reference, if you think its FALSE, tell me why.

Not true. Even if it was, it would have nothing to do with fly by wire. I'm no avionics expert, but if this sort of thing would happen at all it would have something to do with the airplane's flight management system. And IMHO the chances of that are about .00001%

'Fly by wire' refers to the fact that the plane's control surfaces are operated by servo mechanisms instead of hydraulics.  It would have no effect on any navigation system that might induce the plane to flip over.

This guy mentions it in his article, about 3/4 of the way down.

[url]http://www.eweek.com/article2/0,3959,623340,00.asp[/url]

I don't know about that, but early production "block" F16s suffered from a design/construction flaw called "chafing" where wires were run throughout the airframe against sharp corners and such.  This would cause the wires to lose their insulation and short-circuit or induce random signaling.

In the early-mid 1980s, an Air Force pilot was flying his aircraft in reduced visibility (clouds or night, I can't recall) and his avionics when haywire.  His artificial horizon (in the HUD, I believe) told him he was suddenly flying towards the ground, so he pulled up very sharply.  In reality, he was flying upside down and level and his pull "up" actually put him nearly straight down into the ground.  Reportedly, they found his hand still attached to the stick.

His wife sued General Dynamics for faulty design, which they later corrected.

Here's another article about it.  Apparently they caught the equator thing in simulations before the aircraft was actually built.

[url]http://catless.ncl.ac.uk/Risks/3.44.html#subj1[/url]

If you do a search for "F-16 Equator Bug"  you'll get a ton of hits about this, so apparently it is true, although, as I said it was found in simulations.

Regarding "fly by wire", the first aircraft to use fly by wire technology was the Canadian Avro Arrow back in the mid to late 1950s.We have recovered almost enough parts to rebuild one(it was scrapped ans ordered destroyed by our government for political reasons).Hopefully it will fly once again.

  Skullboy.

NO NO NO NO NO!  I do NOT believe things just because there are a lot of references to it.  That by definition is urban legend. If I believe this then I've got to believe the story about the dog that coughs-up fingers...

I want confirmation or proof!  I just KNOW that there's an old McDonald Douglas or General Dynamics engineer hanging around here that's going to debunk (or confirm) this.

That is definitely not true. Inertial laws, gravitational flux, and other physical forces used for navigation do not inverse from southern hemisphere to northern hemisphere.

However, after crossing into the southern hemisphere, the F-16's on-board commode did start rotating the OPPOSITE direction when flushed.

That is definately a software problem.

Actually the F-16 would know where it is, with all the Gyro's and Onboard Navigation equiptment (GPS not withstanding). So yeah, its definately within the realm of possibility.

The F-16 all of them from A to Block 60 know exactly where they are LONG/LAT down to seconds and perhaps further then seconds. Its just that on the Navigational panel it is printed out in Hours'Minutes'seconds. But the onboard computer could actually go down much further tenths hundreths of seconds. Translating down into feet or even inches. But yeah its definately possible.

In other words, it wouldn't be anything caused by physics just how the software glitched under certain conditions.

Weirder crap has happened.

The F-16 killed a couple of test pilots because the FLY-BY-WIRE system intially was force feedback, in other words the stick moved very little, and just measured the pilots force on the stick to determine how much to deflect the control surfaces. Consequently pilots were accidently pushing the f-16 way passed its controllable flight envelope, and into POST-Stall. So they put a regular stick in and put an AOA limiter on the Aircraft.

 

BUNK [whacko]

Well, I'm sending an e-mail to Lockheed-Martin...

[img]http://www.photos.external.lmco.com/Drive4/PI/LR/PD001/PD001-078.gif[/img]

They made a movie about this.

I think you must be mistaken, Skullboy.  The stories that Canadians designed and built an aircraft are apparently all urban legend. [;)]

I think the equator nav thing is nothing more than urban legend.

The wiring harness chafing issue is real though.  At least one pilot was killed by the wires shorting out and causing his instruments to malfunction while he was trying to navigate through 0-0 weather.  Investigators believed that he was spacially disoriented and was flying inverted.  When he noticed his altimeter decreasing fast, he took what he thought was correct action; he pulled back on the "stick".  The aircraft then dove into the ground upside down.

The control column is actually on the right-side console.  I remember hearing about the "lack of feedback" issue about 1978.  The General Dynamics guys did alter the design to provide a bit of movement.

Way cool plane.

Total crap. Urban legend.

I remember that movie, but I can't remember the title.  Kind of like a detective flick made for TV but with a military flavor, like "JAG".

Sorry but the F16 has Dual Hydraulic boosted flight control surfaces CONTROLLED by electronic servo's fed inputs by the flight control computer which interprets pilots inputs. The 16 has 2 primary hyd systems, A & B, A = flight controls. B= flight controls and gear etc...

The issue here is not the mech system which controls the wing's surfaces i.e. ailerons, rudder, etc. but, the feedback control system in automated navigation if there is any at all. I don’t know of any mechanical hydraulic servo or cable systems that invert when passing through the N/S hemisphere.

I have little knowledge of jet planes however; with some industrial controls and fluid power background I highly doubt the f-16s are cable operated. Hence, my confusion in this thread.

Since we are talking about human controlled systems??? And the hydo/mechanical system would loose or gain substantial pressure when crossing this threshold? Or are we talking about pilot input navigation or computer controlled navigation?

Yeah we got a little off track. This story is BS IMOP, The prototype YF16 probably had no computer navigation system to mess with an autopilot to mess with the flight control computer !

Total Bull.  

See what kind of education you are paying for?  HaHaHaHa.  

BTW, you should have sent junior about 35 miles down the road where his blood would have been the correct color of blue.  Sky blue, that is.  (God's favorite color, you know,.......)

Just overlook me while I'm having one of those nostalgic moments....

J

MAN, none of you guys are real sniffers now, are you.
The girl in the movie was Laura Dern..MMmMMmmMmm!
The movie was Afterburn.
It was about what caused the death of her husband. The AF and GD blamed him, she proved it was a crappy design by GD. The courts awarded her 3.31 million, it was overturned due to the fact that what had caused the damage to the wiring was a spec called for and designed by the AF. So it was a military mistake. Can't sue the Military. GD off the hook.
The real problem was that they used Kapton wiring, which is complete shit. You should feel safe knowing that there is miles of this crap inside just about every aircraft built since the late 60's. The Navy is spending big money to replace this shit out of all it's aircraft.
This was one factor in retiring the F-14's early.

The real life wife is Janet Harduvel, she is a total hippie chick, she has her own radio show in Florida somewhere.

Fly-by-wire (in the F-16's case) mens that there is no direct mechanical connection between the pilot and flight controls.
The flight controls are still actuated by hydraulics.
The F-16 had a few problems when it was first being developed, I never heard about it wanting to flip itself over when it crossed the equator.
The F-16 is an unstable aircraft by design, it takes the computers to actually control the aircraft. Not as bad as the F-117 or the X-29.
The F-16 has a "switch" that turns down the flight controls reaction time for takeoffs and landings.
The computer controls the flight control system so that no matter how hard the pilot yanks on the stick the computer will not allow the pilot to overstress the airframe (yea right).
McDonnell Douglas had nothing to do with the F-16, it was a General Dynamics product all the way until they merged with Lockheed, now LockheedMartin.

Yea same problem with boats, once Navy crosses equator they turn upside down too, heck of a sight to see.

On a side note:  Water in Toilets south of the equator spins the "wrong" direction when flushed.

It does not make sense logically. It would mean that the control surfaces are slaved to a GPS system that is out of the pilots control. It is my understanding that Fly by wire, the flight controls are something like strain gauges that read the amount of force the pilot exerts on them. This is converted to electronic signals that  which are fed to the pumps or servos that are connecteed to the flight surfaces. How far off amI?

Only in the countries that have toilets. [;)] Also, they flush the "wrong" way in most of Europe.

Yes,  the F-16 is designed with "30 percent relaxed dynamic stability" which means that its preferred mode of travel (control surfaces held neutral) is any direction BUT nose straight forward.  It is the intrinsic instability of the design that makes it such a highly maneuverable aircraft.   As it has virtually no preference for flying straight and level,  it doesn't take a lot to change the plane's attitude, and the computer system knows how to do that according to the pilot's wishes.    

The more stable a plane is in flight with no control inputs,  the more control input is required to achive a desired change in attitude, and as more control input is required, the responsiveness of the aircraft is lessened.

Think of it like this:  Suppose you were riding a bicycle with wheels that each weighed a thousand pounds.  Would it be very maneuverable, or would it be really good at going in a straight line?  How would it compare to a bicycle that has wheels that weigh practically nothing?     Of course, the lighter wheels would contribute to a more maneuverable bicycle, but it would be less stable.






This is true in principle, but I can't recall if that is a physical switch or if it's an automatic adjustment to the flight control system by means of the computer's programming.    I'm not sure, but I think it's a software adjustment which is based on the position of the landing gear.  When you drop the gear,  the computer shifts to the softer control parameters.



Yes, the system works as advertised...but even maneuvering within the rated limits causes cumulative stress to the airframe.    For example, the Navy purchased 22 F-16N fighters for aggressor tactics education.  This was a special version of the F-16 which deleted the M61 gatling gun and also removed the capacity of the plane to fire air-to-air missiles (as they were ordered strictly for training and not for real combat) and the wings were strengthened.    Despite the wing strengthening,   all of those planes have since been retired after relatively short but intense service lives,  with at least 18 of the planes being grounded due to structurally significant wing cracks due to the intense maneuvering that they were subjected to as members of the Navy's aggressor tactics squadron.

They were painted in a striking multi-shaded blue paint job that approximates some Russian camo schemes,  and as they were equipped with the most powerful engine type available at the time, and weighed substantially less than the standard F-16,  their maneuverability and acceleration performance was the best of any type of F-16 ever for many years to follow. Only the latest models with the P&W F100-PW232 engine outperform the N models in acceleration and top speed.    

In theory,  the F100 engine variant developed for the F22 could be adapted to the F16 frame and retain its appalling 40,000 pound thrust rating (It's 32,000 for the F100-pw232) and give a lightly loaded F16 an appalling and unprecedented thrust to weight ratio of 2 to 1, which could make it by far the most formidable dogfighter in the sky, rather than simply being in the top class today. (No F16 has ever been shot down in air to air combat, ever.)   And incidentally, the F100 engines are so reliable that the general rule is that routine maintenance consists only of oil changes and borescope inspections on a regular basis.   Invasive maintenance is performed only when a problem is detected that indicates such need, which is rare for the type.
The average F100 engine stays in its plane for several years before being removed for any reason.



Yes, it was a change in the name of the company only, as far as I know.

CJ

Okay, here's what I got from Lockheed-Martin:



Verdict: Urban Legend.

Question: How do you get a UNC Chapel Hill graduate off your front porch?

Answer: Pay him for the pizza.

[:)]

Never saw the planes flip over when they crossed the equator.  We sure had problems with pirates when the ship crossed the equator.  They took over for a couple of hours and raised a lot of hell[;)]

This reminds me of several stories I have heard from P-51 pilots. It seems that the D models (at least) had a large fuselage fuel tank that would adjust the CG of the aircraft dependant on the fule left in the tank. During high G load turns, with the fuselage tank more than 1/2 full, the control inputs COULD reverse. This means that in a high G banked turn, the stick is usually pretty much full back. If the control inputs are reversed, this stick position will cause the turn to be stopped and the wings to be immediately unloaded. This scenario is really bad if you are in a hard turn trying to get away from an enemy fighter and all of the sudden your turn ends and for a few agonizing seconds, you are flying pretty much striaght out in front of a FW-190!
The good Mustang drivers would burn fuel out of the fuselage tank down to about 1/2 to 1/3 to keep the CG where it belonged, and then switch to the wing tanks until they were dry. On the way home they would switch back to the fuselage tank.