F-117 Nighthawk's Flip-Down Radar Locators

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By: moon_light - 28th April 2017 at 16:56

.In PAK-FA thread there was a very heated discussion between Keypublishing members about whether F-117 has an RWR or not. Coincidently i tumble into this article today.Hope this settle it.

The F-117 continues to be one of the most intriguing aircraft ever built, even nearly a decade after it was retired, and close to 30 years after it was originally unveiled to the public. From the Nighthawk's "cloaking device" to its "toxic death" paint job, it seem like some of the most interesting aspects of the F-117's story are the small bits that have largely gone unreported. Maybe one of the most obscure and enigmatic details of the "Black Jet" is an elusive component called the Radar Locating System (RLS). For an aircraft that survives on its stealthy shape and coatings, these flip-down antenna arrays seem to deviate drastically from the F-117's modus operandi. But then again, the impetus for their existence may make more sense than not—that is if they really existed at all.
The F-117's Radar Locating System consists (as far as we know) of a pair of small planar antenna farms located under the aircraft's wings, about ten feet from the wing roots, near their leading edges. The idea behind the system seems to have been that the F-117 pilot, who would normally retract all the jet's antennas when moving into hostile territory to minimize its radar reflectivity, could activate the system and its antennas would pop down into the airstream. Once deployed, they would work as a radar homing and warning receiver (RHWR), not only notifying the pilot of the an enemy radar's presence and type, but also its direction and maybe even its general location.
Based on some accounts, the RLS seems to have been more about using the F-117 for the destruction of enemy air defenses (DEAD) role than just avoiding enemy emitters, and was possibly part of a program that aimed to see the F-117 dynamically go after radar and SAM sites as a secondary mission set. Based on the information available, it may have also had a recording function and could have given the aircraft a secondary signals intelligence collection capability as well.

The picture above is credited to James Goodall—if you don't own James's books, make sure to buy them, and a new one on nuclear fast attack subs is coming out this summer. It is a rare photo of this elusive system. According to one source, the array appears to be set up for spiral omni-directional electronic support measures (ESM) antennas, roughly 50mm in diameter, which are typical for 0.2-18GHZ surveillance coverage, and they can be specifically tuned to different bands.
The likely problem with the system was that it drastically increased the F-117's radar cross section when in use, as its flip-down antennas compromised the jet's smooth ventral surface. This is an especially bad attribute when it comes to maintaining a very low radar cross section for the critical forward hemisphere of the aircraft. The likely result was the F-117's radar signature bloomed drastically when the RLS was activated. As such, the system would not only blow the Nighthawk's cover, but it would also turn it into a target. Not just that, but it would have only offered a "snapshot" of the electronic threat environment around the F-117 at any given time. That's because the system would need to be retracted quickly, or it would turn the jet into a sitting duck while operating in enemy airspace.

By most accounts, it seems that the system was either just part of a test series, or was only used for a very limited amount of time operationally, and how many jets it was installed on remains an unknown—that is if it ever existed at all

Some veteran F-117 maintainers seem to remember the quirky RLS trap doors pretty well. They even have mentioned that they were known to sag, which would not only hurt the jet's stealth capabilities, but on dark nights that often were prime operations time for F-117 missions, partially opened RLS doors could be a hazard for maintainers foreheads.

Not just that, but the RLS is prominently featured in the F-117's "Dash One" operating manual. It is not only mentioned, and its abandoned control panel identified, but its location is also shown clearly in a diagram of the jet. You can see the mentions below, and the entire manual is

It has been noted that by 2006, the system was not listed in official hazard and crash responders documents which are posted online here. The diagram showing the RLS doors are still there, but it does not identify it as being something that is accessible like the rest of the aircraft's retractable antenna, so it seems as if the doors were permanently sealed or filled-in at some point in time. This could have occurred during a depot overhaul or upgrade.
While we have a picture, written and first hand accounts of the Radar Locator System, it seems that its existence is still highly doubted by some—including the man that largely oversaw the development of the jet—senior Skunk Works engineer and F-117 program manager Alan Brown
I chatted at length with Mr. Brown about the F-117 and this obscure, and let's face it, mysterious feature. He was as puzzled as I was. After sending him the picture of it, he was kind enough to respond with his conclusions
"This picture doesn’t look like anything that was ever put on a F-117A airplane, and as such I am inclined to discount the story entirely. The only possibility to my mind is that the USAF made the modification themselves without Lockheed’s knowledge, but that itself is impossible for me to believe, knowing how well we followed up with the airplane in the field. Lockheed Skunk Works always had a cradle-to-grave philosophy in terms of follow-up with its products in service."
Mr. Brown was even nice enough to contact his successor as F-117 program manager, Sherm Mullin, to see what his thoughts were about the RLS enigma. His reply was just about the same as Mr. Brown's, stating that "it was never put on the F-117, period." Although he did mention that it could have been a concept from a study that occurred from 1984 to 1985 that apparently went off the rails conceptually and was disbanded with prejudice as a result.
During roughly that same time period it is known, although not well documented publicly, that the F-117 was tested with some fairly elaborate modifications. This supposedly included a handful of sensor systems in addition to the jet's stock Infrared Acquisition And Designation System (IRADS). We know that a passive electronically scanned array (PESA) radar was flown on one F-117 in a specially-built radome fitted on the Nighthawk's iconic wedge-like nose. Maybe RLS was one of the other mods that was deemed successful, and was accommodated for in some F-117s built, but never fully installed.

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By: Ryan - 28th April 2017 at 17:43 Permalink - Edited 1st January 1970 at 01:00

So it looks like it can detect radars but then it compromises its stealth, so probably not really functional against short range pop-up threats. Seems like they use them in a sort of periscope kind of manner. Take a quick look every now and again.

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By: moon_light - 28th April 2017 at 17:52 Permalink - Edited 1st January 1970 at 01:00

So it looks like it can detect radars but then it compromises its stealth, so probably not really functional against short range pop-up threats. Seems like they use them in a sort of periscope kind of manner. Take a quick look every now and again.

From the article quote Alan Brown and Sherm Mullin's words, the radar locator is a concept study and was never put on F-117. Could be because it doesn't work against pop up threat ?.

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By: TomcatViP - 28th April 2017 at 21:22 Permalink - Edited 1st January 1970 at 01:00

Covert elint ? Remember that it was about the same time the 71 was retired.

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By: garryA - 29th April 2017 at 06:03 Permalink - Edited 1st January 1970 at 01:00

Ha knew it.

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By: Cherry Ripe - 29th April 2017 at 08:00 Permalink - Edited 1st January 1970 at 01:00

There is a beautiful underside view of the F-117 here:

http://www.airliners.net/photo/USA-Air-Force/Lockheed-F-117A-Nighthawk/1268420/L

and there do indeed appear to be two hatches outboard of the radar-altimeter diamonds, but with the typical stealth-serration edges one would expect, rather than the straight-edged design shown above.

I think there might be some careful phrasing going on; note that the designer states that "This picture doesn’t look like anything that was ever put on a F-117A airplane". Which does indeed appear correct, but doesn't state that the RLS wasn't fitted.

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By: MSphere - 29th April 2017 at 08:55 Permalink - Edited 1st January 1970 at 01:00

85-0832 with straight design

[ATTACH=CONFIG]253008[/ATTACH]

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By: garryA - 29th April 2017 at 10:54 Permalink - Edited 1st January 1970 at 01:00

I think there might be some careful phrasing going on; note that the designer states that "This picture doesn’t look like anything that was ever put on a F-117A airplane". Which does indeed appear correct, but doesn't state that the RLS wasn't fitted

Sherm Mullin actually specifically mentioned that the RLS wasn't installed though

Mr. Brown was even nice enough to contact his successor as F-117 program manager, Sherm Mullin, to see what his thoughts were about the RLS enigma. His reply was just about the same as Mr. Brown's, stating that "it was never put on the F-117, period." Although he did mention that it could have been a concept from a study that occurred from 1984 to 1985 that apparently went off the rails conceptually and was disbanded with prejudice as a result.

This is likely the same case as the F-22 side array, the hatch exist but no sensor is put there

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By: MSphere - 29th April 2017 at 13:07 Permalink - Edited 1st January 1970 at 01:00

RLS was installed.. You can see the corresponding control panel on the right console..

[ATTACH=CONFIG]253015[/ATTACH]

Later it was removed..

[ATTACH=CONFIG]253016[/ATTACH]

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By: garryA - 29th April 2017 at 13:30 Permalink - Edited 1st January 1970 at 01:00

RLS was installed.. You can see the corresponding control panel on the right console

If RLS was installed in combat coded F-117 , iam sure someone like Alan Brown and Sherm Mullin would have know. They are F-117 program manager and Skunk Works engineer after all. Moreover, we don't even have an official designation for RLS on F-117 while we already know the designation of ELINT systems on much newer aircraft such as ALR-94 (on F-22) , ASQ-239 (on F-35) , ALQ-218 (on EA-18G) , AN/APR-50 (on B-2) ..etc further suggest that it doesn't go into full rate production
Btw your photo is too small for me to see what exactly written in the panel .But there may be 1 or 2 F-117 tested with the RLS for the study between 1984 and 1985 though (hence there may be the switch in some cockpit).Possibly similar to F-16 Vista program but much less popular. Accodring to the article, there is even one F-117 tested with PESA radar.
The F-117 cockpit at national musion doesn't seem to have the RLS control panel though

https://upload.wikimedia.org/wikipedia/commons/8/85/Lockheed_F-117A_cockpit_at_the_National_Museum_of_the_United_States_Air_Force%2C_Dayton%2C_Ohio%2C_USA.jpg

the slightly more modern F-117 cockpit doesn't seem to have it either

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By: MSphere - 30th April 2017 at 02:00 Permalink - Edited 1st January 1970 at 01:00

the slightly more modern F-117 cockpit doesn't seem to have it either

How can you tell? that part of the right console is not visible on your pic, at all..
In this more modern cockpit, the control panel is definitely there..

[ATTACH=CONFIG]253038[/ATTACH]

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By: garryA - 30th April 2017 at 02:43 Permalink - Edited 1st January 1970 at 01:00

How can you tell? that part of the right console is not visible on your pic, at all..
In this more modern cockpit, the control panel is definitely there..

The resolution of your pic is ways too low to actually read what written there. Furthermore, according to the article while both the hatch and the panel were on some F-117 ( i would assume for testing purpose or possible future upgrade at the point just like F-22 cheek array hatch ) but the RLS sensor itself was not installed according to the program manager and engineer

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By: MSphere - 30th April 2017 at 11:11 Permalink - Edited 1st January 1970 at 01:00

The resolution of your pic is ways too low to actually read what written there.

It is the RLS control panel, you can be quite sure.. there is no other panel on the F-117 with the same layout and the location matches perfectly..

Furthermore, according to the article while both the hatch and the panel were on some F-117 ( i would assume for testing purpose or possible future upgrade at the point just like F-22 cheek array hatch ) but the RLS sensor itself was not installed according to the program manager and engineer

Unlike you, who for some awkward reason strongly wishes for the RLS not to be installed, I am not having any agenda here.. I am merely stating the obvious.. the panel is there, that's it.. I think that until the rework the RLS sensors remained there, why would one go to such lengths to remove it if you simply can refuse to deploy it?

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By: garryA - 1st May 2017 at 05:41 Permalink - Edited 1st January 1970 at 01:00

It is the RLS control panel, you can be quite sure.. there is no other panel on the F-117 with the same layout and the location matches perfectly..

The location seem to match indeed, but then again, neither me or you ever sit in the F-117 cockpit to be sure if no other panel look the same. As far as i can see the electric and computer panel look rather similar

I am not having any agenda here

Nah, i dont buy that. You always deny having agenda even when it is clear that you do.

I think that until the rework the RLS sensors remained there, why would one go to such lengths to remove it if you simply can refuse to deploy it?

Or the fact that it can only take snapshot and increase aircraft RCS significantly when in used lead to it only used in test and not installed. Also even when undeloyed there are still gap between panel thus increase surface diffraction, that why the hatch was later sealed. Why would Sherm and Brown lie about a retired program?

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By: Cherry Ripe - 1st May 2017 at 06:29 Permalink - Edited 1st January 1970 at 01:00

Why would Sherm and Brown lie about a retired program?

Why would the USAF lie about it in the Dash-1? That was a restricted-circulation document ( might even have been NOFORN at one point ). If the RLS panel made it into the Dash-1, which was issued fleet-wide, I'd believe that over the memory or NDAed statements of two former project staff.

Until a former crew-member speaks out I suppose it'll just have to remain an enigma.

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By: MSphere - 1st May 2017 at 18:25 Permalink - Edited 1st January 1970 at 01:00

The location seem to match indeed, but then again, neither me or you ever sit in the F-117 cockpit to be sure if no other panel look the same. As far as i can see the electric and computer panel look rather similar

I am not going to argue, here is the F-117A manual, go and find me a panel which looks the same..

http://www.avialogs.com/en/aircraft/usa/lockheed/f-117nighthawk/to-1f-117a-1-utility-flight-manual-f-117a-aircraft.html#download

Nah, i dont buy that. You always deny having agenda even when it is clear that you do.

Wow, you seem to know much more than I do.. so, what exactly is my agenda so that I invented a panel which actually is not there? :confused:

Or the fact that it can only take snapshot and increase aircraft RCS significantly when in used lead to it only used in test and not installed. Also even when undeloyed there are still gap between panel thus increase surface diffraction, that why the hatch was later sealed.

Yes, it was only used in test and not installed, that is why it has found itself in the flight manual, in the simulator and why I have shown you two independent pics of a RLS panel installed in the cockpit. Yep, that makes sense..

Why would Sherm and Brown lie about a retired program?

.. because it was classified?

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By: garryA - 1st May 2017 at 20:08 Permalink - Edited 1st January 1970 at 01:00

I am not going to argue, here is the F-117A manual, go and find me a panel which looks the same

This one ?

https://s15.postimg.org/o6asaoyaj/battery.jpg

Or could be this

https://s16.postimg.org/i6naxrm9h/8e8070051cbf2b4ae7e91e9b922f7b65.jpg

Idk, they all kinda look similar for me.

http://www.f-16.net/forum/download/file.php?id=22960&mode=view

what exactly is my agenda

I don't know, maybe just to side with flateric , may be just to say iam wrong because we always disagree....etc. That is my perspective, i know you will disagree, like you always do. But have been here for a while it very hard for me to believe you don't have agenda.

Yes, it was only used in test and not installed, that is why it has found itself in the flight manual, in the simulator and why I have shown you two independent pics of a RLS panel installed in the cockpit

I know it exist in manual , that what the article mentioned. Your pictures i still don't really buy it because it too blurry for me to read what written on the panel

because it was classified?

AN/APR-50 (B-2) wasn't classified , ALR-94 (F-22) wasn't classified , ASQ-239 (F-35) wasn't classified. They are all arguably much newer and more important why suddenly F-117 ? especially when it already retired?

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By: mig-31bm - 1st May 2017 at 20:33 Permalink - Edited 1st January 1970 at 01:00

Flip RWR sound like a horrible idea. If it up then pilot don't know if he being watched. If pilots know he being watched then why bother flip it down ?.

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By: MSphere - 1st May 2017 at 21:25 Permalink - Edited 1st January 1970 at 01:00

This one ?

Errr, nope.. this one is right here..
[ATTACH=CONFIG]253050[/ATTACH] [ATTACH=CONFIG]253051[/ATTACH]

Or could be this

Nope.. this one is on the side wall and has not changed or moved since the YF-117
[ATTACH=CONFIG]253052[/ATTACH]

Idk, they all kinda look similar for me.

Those are larger than the RLS panel and would not fit in that place..

I don't know, maybe just to side with flateric , may be just to say iam wrong because we always disagree....etc. That is my perspective, i know you will disagree, like you always do. But have been here for a while it very hard for me to believe you don't have agenda.

I disagree because you are wrong on this one.. and I think I have made honest effort to support my stance by evidence.. there is nothing more behind it..

I know it exist in manual , that what the article mentioned. Your pictures i still don't really buy it because it too blurry for me to read what written on the panel

I, too, can't read it but the switches, letters and lines match perfectly. The position matches, too.. I have checked all other panels in the F-117A cockpit before I have even started this conversation (hence the mentioned honest effort).. there is nothing else like it.. an error is very improbable..

AN/APR-50 (B-2) wasn't classified , ALR-94 (F-22) wasn't classified , ASQ-239 (F-35) wasn't classified. They are all arguably much newer and more important why suddenly F-117 ? especially when it already retired?

I can't answer that question..

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By: Levsha - 1st May 2017 at 22:02 Permalink - Edited 1st January 1970 at 01:00

AN/APR-50 (B-2) wasn't classified , ALR-94 (F-22) wasn't classified , ASQ-239 (F-35) wasn't classified.

What do you mean weren't classified? The avionics systems on all US military aircraft are certainly "classified" to a greater extent. I don't think anybody can tell you a whole lot about them, except perhaps their basic operating principles and functions, and specifications.

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By: garryA - 1st May 2017 at 22:20 Permalink - Edited 1st January 1970 at 01:00

What do you mean weren't classified?

I mean like their existence and name wasn't denied