
How To Take Down an F-117 - jscore
http://www.strategypage.com/htmw/htada/articles/20051121.aspx
======
runjake
We recently discussed this in another thread, but one of the low observability
(stealth) characteristics of the F-117 was a reduced radar cross section
(visibility) using flat sections of fuselage in a faceted manner.

This was calculated by hand by Skunk Works engineers. They didn't have the
benefit of computerized physical modeling back then. They were able to reduce
the radar visibility to a size about that of a bird (it's actually a little
larger, iirc).

My understanding with Zoltan is that he just looked birds flying at
500-600mph. He claims that he invented all this complex, custom gear
accompanied by advanced-sounding jargon, but the US military dismissed it as
hyperbole (which Zoltan is known for).

The B-2 had the benefit of computer-aided physical modeling which explains
it's lack of facets. The B-1 and B-52 also have low observability
characteristics to reduce their radar and infrared characteristics (although
they aren't known as "stealth" aircraft).

I think that stealth aircraft as we know them are largely obsolete. Hence, the
increased focus on UAVs and satellites. I have some ideas about where to go
next, but the costs would make the B-2 look like a Girl Scout cookie sale.

Disclaimer: I worked on many of the above-mentioned aircraft.

~~~
Dove
_This was calculated by hand by Skunk Works engineers. They didn't have the
benefit of computerized physical modeling back then._

Half true.

Stealth had been known to be theoretically possible [edit] for a long time. I
want to say the critical ideas date to papers in the 1930's, but I'm not sure
on that. I do know there were flying attempts at it in the 40's. [/edit] But
nobody could really pull it off due to the sheer computation required.

Stealth happened when computers got good enough. The critical breakthrough was
a computer program. Not a full blown physical model, mind you; a very specific
program to solve a very specific mathematical problem created by a very clever
mathematician.

But a computer program nonetheless.

\-----------

<http://www.456fis.org/F-117_STORY.htm>

    
    
       In early 1975, the initial Skunk Works Project Team 
       consisted of Ed Martin (Project Manager), Dick Schemer 
       and Denys Overholser. Overholser had recalled a 
       discussion with his then boss, Bill Schroeder, some years 
       earlier, concerning the mathematics and physics of 
       optical scattering. The two had concluded that detectable 
       signatures could be minimized utilizing a shape composed 
       of the smallest number of properly orientated flat 
       panels. In addition, Schroeder believed that it was 
       possible to develop and resolve a mathematical equation 
       capable of calculating analytically, the reflection from 
       a triangular flat panel; this in turn he hypothesized 
       could be applied in a calculation relating to RCS. 
       Overholser had hired his former boss out of retirement 
       and as Schroeder's mathematical computations became 
       available, Overholser and his team of two engineers were 
       able to use these to write the computer program that 
       could evaluate the RCS of prospective design submissions 
       nominated by Dick Scherrer and his group of preliminary 
       design engineers. Derys and his team worked night and 
       day, and in just five weeks produced an RCS prediction 
       program known as 'Echo 1'. The resultant model was a 
       faceted delta wing design which had more than its share 
       of skeptics within the Skunk Works, some in aerodynamics 
       referring to the shape as 'the Hopeless Diamond'.
    

[Edit: Fact check]

~~~
icegreentea
The computer's were important not just for calculating the shape of the
airframe, but how to fly the damn thing. You could in theory calculate the
F-117 (but not the B2's) frame by hand. But flying the F-117 -or any stealth
airframe - requires computer guidance.

In act, the prototype (Have Blue) just recycled some extra flight computers
from the F-16 (which is unstable in one axis... the F-117 is unstable in all
three).

------
jscore
More info here: <http://en.wikipedia.org/wiki/Zolt%C3%A1n_Dani>

Looks like Zoltan is a baker now in his home village in Serbia after retiring
from the military.

If he was a US general, he'd have a book, do media tours all over the country,
and perhaps even run for office.

~~~
ryanwaggoner
He was a colonel, not a general. And even then, the US has hundreds of
generals and admirals, most of which just retire and go on to a quiet 2nd
career or retirement. The ones you see on CNN are the exception.

------
jcapote
This article is really hard to read. It basically boils down to:

"He developed some ideas on how to beat stealth, based on the fact that the
technology didn't make the F-117 invisible to radar, just very to get, and
keep, a good idea of exactly where the aircraft was. Zoltan figured out how to
tweak his radars to get a better lock on stealth type targets. This has not
been discussed open"

I wish they went into more detail as to _how_ they did that.

~~~
andyv
Perhaps something along the lines of "Use the radar to look for the bird
flying at 600mph"...

~~~
runjake
I'm not sure why andyv was downvoted, other than the fact he quoted me in a
prior thread without citation? ;)

This is the conclusion the US military drew and was corroborated by Ben Rich
(the "father" of the F-117) in his book.

------
ajays
Personally, I think this bit was the key: The Serbs had spies outside the
Italian airbase most of the bombers operated from. When the bombers took off,
the information on what aircraft they, and how many, quickly made it to Zoltan
and the other battery commanders.

My guess is, if you know how many airplanes are on their way and at what time,
you can prepare. Knowing the ground speed, you can estimate when they're going
to be above you and quickly light up your radar, take a pot shot, and then
turn it off and scoot.

------
akamaka
Previous discussion: <http://news.ycombinator.com/item?id=799494>

------
poi98u7y6tryuio
So he used training and tactics - isn't that rather unsporting? I thought the
idea was we only flew expensive aircraft against people living in caves (or at
weddings) or at least stuck to bombing those with no anti-aircraft ability.

Poor people shooting back at $Bn aircraft just isn't fair.

~~~
PostOnce
Who said it was unsporting?

------
jleyank
I have to check, but I thought they used AAA to take the F-117 down. If so,
such things are statistical - put enough metal in a volume of space suspected
of having a plane, rinse, repeat.

If he had the intel to guestimate the location or path of a plane, it's just a
matter of time before the thing gets hit.

update: some searching revealed that low-frequency/old radars picked it up and
some form of SAM got it. But there were bullet holes in the wing, too. If
there was a hostile fighter up, that would work if it could be guided close
enough. I've read previously that old/low-freq radars would be more effective
as they weren't what was modeled when the thing was built.

The stuff's not magic, although the press and popular literature makes it out
as such. Far better to fly things w/o a pilot, as holding missile fragments
for hostage doesn't generate much interest.

~~~
lucasjung
It was the missile. However, he did know where to point it well ahead of time
before firing. As the article mentions, he used visual cueing and short-range
shots to minimize the time his radars were transmitting.

One thing this article didn't mention: when it came to predictability, NATO
aircraft were the polar opposite of Zoltan--they often flew the same routes,
at the same times, using the same radio callsigns, day in and day out. This
made it very easy for him to predict where an airplane would be. In the case
of the F-117, I have heard that the pilot made back-to-back passes over the
same target and was shot down on the second pass.

I also heard an apocryphal story about Zoltan: After the war he was
"debriefed" (not really an interrogation, since the war was over and he hadn't
committed any war crimes, but not exactly a friendly chat, either) in order to
learn his tactics. After a while, his interviewers realized that he believed
that the NATO forces were so arrogant that they had deliberately tipped their
hand to him: he couldn't understand any other plausible reason why they had
been so bad at keeping secrets, especially in regards to the movements of
their aircraft. When they tried to explain that they had thought they were
practicing good security, he refused to believe them and accused them of lying
--nobody could be THAT bad at keeping secrets!

~~~
nl
I hadn't heard that story, but I think I'd believe it.

There are a few references around to how some of his intelligence network
involved people sitting outside (military) airports in Italy and _phoning in_
when F-117's were taking off.

~~~
brc
I just read a story written by Jeremy Clarkson where he visited Iraq. His
transport arrived and departed in the middle of the night, lights off, so that
spotters couldn't determine direction or type of aircraft. So it would seem
that they are acutely aware of the issue.

------
dkokelley
The writing is difficult to read, but the moral of the story is good:
Effectiveness = Technology * People. Zoltan had good people to compensate for
antiquated technology, whereas NATO had modern tech, but the human factor
negated much of the tech advantage.

Also, the title is misleading. The article is more about how to hide than how
to neutralize the F-117. Being nimble, using landlines, and understanding the
enemy helped Zoltan outfox those who would try to stop him.

------
yread
There was also this rumour going around that f117 can in fact be detected by
passive systems Tamara and Vera. see
<http://72.52.208.92/~gbpprorg/mil/radar/tamara02.htm>

~~~
mjb
Optimisation for stealth against bistatic and multistatic radar systems is a
different problem from the monostatic case. The important thing is the split
between the position of the transmitter and receiver. In the monostatic
(transmitter and receiver in the same place) case, you need to optimise to
reduce radar energy reflected back in the direction of the transmitter.

When the receiver and transmitter are split, this problem gets harder, because
you need to optimise to reduce radar energy transmitted back in the direction
that recievers are likely to be (or don't reflect any, but that's a different
problem). This becomes even harder in multi-receiver systems, and even harder
in multi-receiver-multi-transmitter systems. As computation power and
communication bandwidth becomes cheaper, lower power, smaller and easier to
hide, many of the assumptions used during the development of the current
generation (and past generations) of stealth aircraft are becoming invalid.

Passive location systems, either secondary radars or systems using
'transmitters of opportunity' also reduce the effectiveness of anti-radiation
weapons significantly.

The radar vs. stealth arms race continues.

