Beginning in 1940, the DFS (Deutsches Forschungsinstitut
für Segelflug), or German Research Institute for Gliders,
started an ambitious program to achieve supersonic flight. Since the only
engines powerful enough and available at the time were rocket engines,
it was realized that the solution was to have the assault on the sound
barrier take place at a high altitude. It was decided to divide the program
into three sections:
The DFS decided to design a new aircraft (although much was learned in
an earlier design, the DFS 54) to investigate the first part of their three-step
program. Thus, in 1941, the RLM assigned the number 228 to the aircraft,
and requested that the DFS 228 also be designed for high-altitude reconnaissance
duties as well as research work.
The first part was concerned with developing and testing of the pressurized
cockpit section, the method of pilot escape in case of emergency and performance
testing of rocket engines at high altitudes.
The second part was to discover the performance of various sweptback wing
configurations. The DFS acquired the Heinkel P.1068 designs, which had
various wing sweep angles.
The third and last part was to actually build a supersonic aircraft with
information learned in the above two steps, which was eventually to become
the DFS 346.
The first prototype
of the DFS 228 (coded D-IBFQ) was completed in 1943 by the DFS, although
the control sections and landing skid were built by Schmetz. The fuselage
of the DFS 228 V1 consisted of three circular sections: the nose section
containing the cockpit; a center section which contained the landing skid,
fuel tanks and a Zeiss infra-red camera; and the tail section with the
Walter HWK 509A-1 or A-2 rocket engine. The wing was attached at the mid-fuselage
point, and featured 4.5 degrees of dihedral. Wooden construction was used
for the entire wing, with a single laminated wooden spar running from wingtip
to wingtip, wooden ribs and a plywood covering. Wide-span divided
ailerons were fitted to the wing (the inner section acted as landing flaps),
and lift spoilers were also fitted to the upper and lower wings. A conventional
tail unit was used, also with all wooden construction. Landing was done
on a retractable skid. Since the DFS 228 was to operate in extremely high
altitudes, a completely pressurized cockpit was designed. Although it was
thought at first that the pressure cabin could be of wooden construction,
a metal compartment was built after the wooden one failed to hold sufficient
pressure. The nose section was double-walled constructed with aluminum
foil insulation. The V1 prototype had a conventional seated pilot's position,
but the V2 and later aircraft were to have a prone pilot position, due
to the difficulty of of sealing such a large compartment with the pilot
seated upright. All glazed areas were made of double layered Plexiglas
and were provided with warm air circulation between layers to prevent frosting
of the Plexiglas.
sealing problems became apparent on the V1 cockpit, it was decided to go
with a prone pilot. An adjustable horizontal couch was provided for the
pilot to lay on; all controls, oxygen supplies and cockpit equipment mounted
directly to the steel tube structure which was then attached directly to
the main fuselage bulkhead at the back of the cockpit. This also had the
added advantage of keeping the pressurized area small. thus it was easier
to keep sealed. The new cockpit arrangement was incorporated in to the
DFS 228 V2 and later aircraft.
A very interesting
flight plan was arranged for the operational recognizance DFS 228. It was
to be mounted above (or could be towed behind) a carrier aircraft (usually
a Do 217), where it was then carried to approximately 10000 meters (32808
feet). Upon release, the DFS 228 would then ignite its rocket engine until
an altitude of about 23000-25000 meters (75460-82021 feet) was reached.
By this time, the 228 would be over its photographic target area and after
its reconnaissance mission was fulfilled, the aircraft would then make
a long glide back to base.
In the case
of an emergency at high altitudes, the complete pressurized nose section
(with all life support equipment attached) could be jettisoned by firing
four explosive bolts, or it could take place automatically when the cockpit
pressure dropped below a minimum level. An automatic parachute would then
deploy to stabilize and slow the descent. When a safe altitude was reached,
the pilot was ejected by compressed air, who would then descend to the
ground using his personal parachute. This escape procedure was successfully
tested by the Soviets after the war, with a captured DFS 346, which had
a similar escape system.
DFS 228 V1 flight
trials were made at Hörsching, just southwest of Linz, by the DFS
and also by Erprobungsstelle Rechlin in late 1944. Over 40 test flights
were made, and although powered flight was to take place in February 1945,
none were actually made using rocket power, and none exceeded 10000 meters
(32808 feet). It was in these tests that the upright pilot's position was
found to be unsuitable for proper cockpit pressurization. The decision
was made to go with the prone position cockpit, and was included into the
DFS 228 V2, which was built and also flight tested. The main faults found
with the 228 were that it suffered from poor aileron effectiveness at high
altitudes and that the elevators were very sensitive. Other than the early
pressurization problems, the general handling was satisfactory and the
problems would not hamper the intended role of the aircraft. A potential
problem could have arisen with the use of the Walter HWK 509A1 or A-2 rocket
engines, due to the fact that the flight profile meant for the rocket engine
to be intermittently operated, and the possibility existed of valves and
pumps freezing up at the extreme altitudes and low temperatures in which
the flight was to take place. Of course, newer rocket engines were continually
being developed, and perhaps some sort of heating system or the possibility
of using M-Stoff and A-Stoff (methanol and oxygen) for fuels, which could
have operated at much lower temperatures, could have been developed.
The DFS 228
V2 was destroyed at Hörsching in May 1945, only the forward section
had parts worth salvaging. The DFS 228 V1 survived the war, and was surrendered
at Ainring in the US Zone of Occupation. On June 18, 1945, it was taken
by road to the US Air Technical Intelligence Unit at Stuttgart. It was
later sent to the RAE Farnborough in June 1946, and although allegedly
was sent to the scrap pile in 1947, another report has the DFS 229 V1 being
sent to Slingsby Sailplanes Ltd. at Kirkbymoorside in Yorkshire. Strangely
enough, Slingsby offered a design for their T44, a stratospheric research
sailplane which incorporated several DFS 228 features, including the detachable
pressurized cockpit section.
Ronnie Olsthoorn's DFS 228 images
DFS 228 Dimensions
DFS 228 Weights
DFS 228 Performances
DFS 228 Models
||Injected & Decals
||includes mounting struts for
Do 217K carrier aircraft
DFS 228 cockpit, designed by Dr. Felix Kracht
DFS test pilot Rolf Mödel tries
out the prone position at the DFS Ainring facility. The landing skid activation
lever can be seen near the bottom of the photo.
T-Stoff Walter HWK
Zeiss Infa-red Camera
Fuel Lines Combustion Chamber
Pressure Cabin Tank
| The escape sequence from the DFS 228
1) The pressurized nose section is separated from the
fuselage by four explosive bolts.
2) The nose section's descent is slowed by the use of
3) When a safe altitude is reached, the pilot is ejected
from the nose section.
4) The pilot's parachute is automatically deployed.
5) A normal parachute landing is then made.
|The rear of the DFS 228's pressure cabin, note the
four explosive bolts and hookups for
electrical connections and flight controls
A side view of the pressurized nose section of the DFS 228
The DFS 228 V1 atop its Dornier Do 217K V-3 carrier aircraft
In Flight (unpowered/gliding) photos of the DFS
The DFS 228 at Ainring, just before its removal to
the US Air Technical Intelligence Unit at Stuttgart
Farnborough 1946: The remains of the DFS 228 V1 languishes
outside, its final disposition is unknown.