By Rob Arndt

Perhaps one of the most over-looked aircraft designs in the history of aviation is the GEMA “Kristall Flugzeug” (Crystal Aircraft) projekt of 1945 which originated three decades before the F-117 Nighthawk dedicated stealth fighter.


GEMA (Gesellschaft für Elektroakustische und Mechanische Apparate) historically was the birthplace of German radar and sonar development, employing in 1940 around 6,000 workers. GEMA was responsible for the development of the Freya, Seetakt, FuMG 404, and PPI Panorama radars as well as various German sonar equipment during the war, producing thousands of units.

The Jagdschloz FuMG 404 was designed with GEMA systems in 1937. It was produced in 1943 by Siemens & Halske. It operated on a frequency of 158-240 MHz. These frequencies could be changed so that the reflection of chaff could not be seen. 62 units were built.

The German heavy cruiser "Admiral Scheer" with the Seetakt radar on the mast


The world's first "Panorama" or Plan Position Indicator (PPI) display radar was built by GEMA in 1940 at Tremmen near Berlin. The 20 m large antenna is located in the top of the concrete tower and it rotates through 360 deg. at 6 rpm. Range is 120 km. The radar display station is located in the base of the tower and a PPI display, as shown above was used. The PPI radar was invented and patented by Hollmann in 1940 and developed by GEMA in 1937. This unit could not be jammed and it was operational up to the end of the war.

The Freya FuMG 39G was the first operational German early warning radar defense system. Before the beginning of WWII, in 1938, eight of these units had been delivered by GEMA and deployed along the German border.
The early versions had a range of 60 km which was later increased
to 120 km. Azimuth accuracy was 1.5 degrees and better.
These sets operated on a 1.8-2.0 meter wave length.




While GEMA concentrated mainly on radar development, the Luftwaffe inquired in 1944 if GEMA would investigate the claims by the SS that “crystal technology” could both improve radar equipment and that an application of a crystalline coating to a lightweight  fighter could possibly render such an aircraft totally “invisible” to Allied radars - all of them.

GEMA investigated a wide range of crystals using Siemens X-ray analysis and experimented with crystalline-coated materials subjected to various radar wavelengths using a specially modified DFS Weihe (Harrier) new build intended for sale to Sweden in 1945, similar to the license-built SE-104 trainer version already in use by the Swedish Air Force since 1943.


Swedish SE-104 (DFS Weihe), only 1 of 19 sent to
Sweden during WW2






















Normally, the Akaflieg-Munich Mu-18 Messkrähe (Measuring Crow) would be adapted for testing if it were just for an experimental stealth wing section, but could not in this case due to the need to cover the entire aircraft with crystalline coating and anti-radar materials. So, a major German aircraft manufacturer was contracted to heavily modify the DFS Weihe (reputed to be Messerschmitt).

The German Weihe

GEMA also built an experimental crystal radar unit that utilized jasper crystals for radar detection but could not make it work successfully.

Although no photo is known to have survived of the heavily modified test glider, the faceted affixed crystalline coating mixed with dielectric radar absorption fillers and redesigned overlaid cockpit is said to have rendered the craft “invisible” to all German radars used to detect it. It was quickly dubbed the “Kristall Flugzeug” (Crystal Aircraft).

After 4 successful flights with the glider, the GEMA information gathered was passed along to the RLM (German Air Ministry) with a request for a full size fighter mock-up. Since DFS was already overburdened with their DFS 228 recon rocket plane, DFS 346 research rocket plane, and a new test plane for television guidance… the GEMA projekt was not realized before capitulation.

Lippische DM-1 glider prototype, 1945

DFS had proposed a delta-winged craft to incorporate the crystalline technology, probably based on the Lippisch DM series of delta craft.

The “Kristall Flugzeug” was to be codenamed “Schwarz Diamant”- the “Black Diamond” under RLM provisional allocation 8-468.

The GEMA facility, however, was captured by the Soviets who sent thousands of its scientists and engineers back to the U.S.S.R. while demolishing some of its buildings. GEMA burned as many of its secret files as possible before evacuation.

The “Black Diamond” had not yet been assigned a RLM allocation number either and was believed to have been destroyed to prevent capture. So it remained a closely guarded secret for many years until
US intelligence went through the RLM files recovered at Wright Field.

The GEMA factory in Berlin


Ironically, it was a postwar book by Soviet Professor Pyotr Ufimtsev on “radar diffraction through use of geometric shapes” that led directly to the USAF development of the faceted F-117 in the 1970s after the professor’s book was translated into English! It seems the Soviets did not get any information concerning the GEMA/DFS “Schwarz Diamant” and neither did they accept Ufimtsev’s theories on anti-radar shapes.


The USAF, not sure that faceting would initially work, called their first design of the new stealth fighter… the “Hopeless Diamond”!


Hopeless Diamond design courtesy of Unicraft Models


'Hopeless Diamond'

Meanwhile, independent West Germany had secretly built the stealth interceptor MBB (Messerschmitt-Bolkow-Blohm) Lampyridae (Firefly) w/o US knowledge. In a visit to MBB in 1981 the USAF officials became infuriated when they saw the mock-up of the Lampyridae and put pressure on the West German Government to give the project up. It did in 1989 but MBB is claimed to have retained stealth knowledge as it evolved into DASA and now EADS.

MBB Lampyridae mock-up in the early 1980s

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Had they the knowledge of both the USAF development and of their own GEMA data? No one can confirm either.

Yet one can only wonder what impact the GEMA “Schwarz Diamant” would have had on the air war in 1945 had the war progressed longer. While the Ho-IX/Go-229 is always credited as the first true stealth aircraft in the world, having flown on February 14, 1945
... it is little-known or unknown that GEMA had its own stealth concept.


Aerospace writer Bill Rose responds to the alleged triangular Firely II NATO aircraft. 


May I add a few comments to the recent report on Firefly? Firefly (proper name Lampyridae) is a stealth interdictor aircraft, semi-secretly built by Messerschmitt-Bolkow-Blohm, (MBB) now Daimler Benz Aerospace in Germany.  Designed by Dr. Gerhard Lobert, this fighter sized aircraft is essentially a second generation F-117A.  Two demonstrators were flown at the Overberg Test Range in South Africa during the late 1980s, but the project was placed on the back burner and has probably been canceled.


Rose wrote this prior to the MBB-Lampyridae cancellation in 1989 and the transition from DB Aerospace over to EADS in the 21st century. Although his information is outdated, it does state that the first Fireflies flew. EADS surely has kept the stealth technology alive. Although the rumored Firefly II has yet to be identified, EADS in co-operation with Spain has produced the stealth UCAV Barrakuda which flew in 2006.