# 1. History of the real Dornier 128-6 “D-IBUF”

Dornier has a longstanding tradition in flying boats, culminating in the giant triple-deck Do X with no less than 12 engines grouped in 6 tandem engine nacelles on top of the massive wing. The composite twin-turboprop “Seastar” of Dornier heir Conrado which up till now hasn't made it to the production stage due to money and hereditary troubles within the Dornier family was the last attempt to revive this long tradition.
Another Dornier son, Irenäus ("Iren"), is currently in the process of bringing a small two-seater amphibian flying boat to production status. It is called S-Ray 007 and is primarily aimed at the new LSA class in the USA.
Iren has also gained some popularity by bringing into renewed service the Do 24-ATT seaplane turned amphibian (a former company demonstartor) and flying it halfway around the globe, making many public appearances with this magnificent piece of kit at all sorts of aviation events.
The other not so well-known specialty of the traditional Dornier company (later a part of the now defunct Fairchild-Dornier) are STOL (Short Take-Off and Landing) utility aircraft, starting with the Do 27, a single engined high-wing taildragger with fixed slats along the leading edge of the wing combined with double-slotted flaps. Some are still active today, particularly in parachuting.

For reasons of better safety and performance a twin engined version was dubbed Do 28A and already had the unique layout of the later 128-6: The engines where mounted on pods protruding from the floor of the fuselage and the main gear was also attached to these pods. This design allowed for the wing to be free of lift-reducing engine cowlings and the thrust center of the props to be approx. in the height of the drag center of the complete aircraft.
From these A/B versions the main production model Do 28D Skyservant evolved sporting an all-new design, particularly a spacious rectangular section fuselage. Its maiden flight took place at Dorniers’ company airfield in Oberpfaffenhofen in Bavaria, Germany on February 23, 1966. It was particularly popular with the German Luftwaffe (101 aircraft) and the German Naval Air Arm (20 aircraft), but was also exported to and is at home in all regions of the world with less sophisticated airport infrastructures, totaling in more than 200 aircraft in 30 countries. It was (and in part still is) used for the following tasks:
- passenger and freight transport
- liaison missions
- sea patrol and coast guard missions
- dropping of parachutists
- SAR operations
- ambulance missions
- photogrammetric survey
- remote sensing missions

"D-IBUF" started out as a Do28D-2 with the serial number 4302. Its first life being that of Dornier's Company Demonstrator it went through many stages of modification: in this picture which was taken at the 1976 Hannover Air Show in Germany it is already fitted with external fuel tanks of the later Do128-2 and 128-6 versions.
The Do28D created an absolutely ear drum busting racket with their unmuffeled Lycoming piston engines and prop tips brushing very closely by the fuselage. They could well be heard approaching minutes before they actually came in sight.
For this reason as well as due to problems in the supply of avgas in some parts of the world Dornier around 1977/78 modified "D-IBUF" into the so-called Do 28D-5X Turbo-Skyservant prototype and initially two Avco-Lycoming turboprop engines downrated from 608 to 405 SHP (Shaft Horse Power, amount of power delivered to the prop, disregarding any surplus thrust generated by the exhaust gases), shown here at the International Aerosalon at Le Bourget, Paris in 1978.
German sub-title for this Photo of the Do 28D-5X Turbo-Skyservant prototype from “fliegermagazin no.7, July 1979”: Workhorse for the Third World: Dorniers young Turbo-Skyservant
Note that the engine nacelles are still rectangular.

In this side view of the Do 28D-5X Turbo-Skyservant prototype the registration “D-IBUF” is visible, as are the external under wing tanks. In the background is one of the many Do 28D of the German Luftwaffe.

In the course of development the usage of Pratt & Whittney Canada’s extremely popular and dependable PT6A-110 turboprop engines plus a complete (and in my eyes rather pretty) re-design of the engine nacelles transformed “D-IBUF” into the first production specification aircraft of the Do 128-6 which made its maiden flight on March 4 1980:
Note that the front edge of the aerodynamic balancing tab of the rudder still is practically vertical like in the prototype Do 28D-5X Turbo-Skyservant.

The rudder was later replaced by the reverse slanted front edge version of the former Do 28-D. Sometime in 1981 D-IBUF was fitted with and certified for operation with wheel/ski landing gear. This was due to the “Alfred Wegener Insitute for Polar Research” (AWI) actually flying it down the west coast of Africa to Antarctica dubbed “Polar 1” along with the next derivative of this plane, a Do 228-100 (Polar 2) in 1983/84 on an expedition sponsored by the German Federal Minister for Research and Development. Sadly Polar 3 (another Do228-100 of the AWI) and its crew of 3 where shot down by Frente Polisario guerrillas while overflying the Western Sahara on its return flight from Antarctica back home on 24 February 1985…
D-IBUF however was sold to the Technical University of Braunschweig to serve as the flying lab of their Institute of Flight Guidance and Control. The orange / white / marine blue livery from the AWI was retained apart from some retouches particularly of the logo on the vertical stabilizer.

A nose beam in various shapes and sizes (depending on the projects carried out with it) was added. In its tip it carries a pitot tube type airspeed sensor to allow for precise airspeed readings. Various other sensors and antennas cover the plane. Inside 19” racks for computers and measuring equipment were installed. For more details on the "goodies" currently installed in this research aircraft please visit its very own website...
The FS2004 version of "D-IBUF" (contained in “do1286V5.zip”) depicts the plane as it was in February 2001 when I was able to photograph it in full detail and could even fly in it for the first time. It can now be fitted with two additional pitot tube booms protruding forward from the wingtips which proved helpful when flying directly behind a Bombardier "Global Express" business jet in tests concerning its vortex - one of the now four airspeed sensors always has a plausible signal even in such extreme circumstances.

One of the most interesting projects (from a flight simulation point-of-view) it was involved in so far (around1995) was the so-called “Synthetic Vision”, a joint project of the Technical Universities of München and Braunschweig led by Professor Gottfried Sachs. It is a symbiosis of GPS navigation, a digital terrain database, a monitor (initially a display helmet with motion sensor) and a kind of flight "simulator". All combined into a package that reads the current aircraft coordinates via GPS, positions the virtual aircraft in the same location over the digital terrain database and projects the resulting pilot’s virtual view onto the screens of the display helmet. This would allow virtual VFR approaches to airfields completely covered in fog (as depicted at left – approach to Runway 27 at Braunschweig in foggy conditions. The inset shows the real view from the right side of the cockpit, the display helmet of the pilot filling most of the view), or to safely follow rugged terrain in low visibility conditions.
The technology was additionally verified by a flight through the scenic Altmuehl valley in Bavaria, southern Germany, below the valley ridges precisely along a virtual corridor depicted on the pilot’s display helmet.
NASA along with a number of avionics companies is currently working on making this technology affordable and dependable enough for the general (flying) public. To my knowledge this is now available in certain types of business jets.
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## 1.1 Technical Data

Power plants | 2 x Pratt & Whitney PT6A-110
Type of propeller | Hartzell B3TN-3D T10282B-9.5
Number of prop blades | 3
Propeller diameter | 2.36 m / 7 ft 9 in
Wing span | 15.55 m / 51 ft
Length | 11.41 m / 37 ft 5 in
Height | 3.9 m / 12 ft 10 in
Wing area | 29 m² / 312 sq. ft
Cabin length | 4.10 m / 13 ft 5 in
Cabin width | 1.37 m / 4 ft 6 in
Cabin height | 1.52 m / 5 ft
Cabin area | 5.30 m² / 57 sq. ft
Cabin volume | approx. 8 m³ / 283 cu. ft
Maximum ramp weight | 4380 kg / 9656 lbs
Maximum take-off weight (MTOW) | 4350 kg / 9590 lbs
Maximum landing weight | 4140 kg / 9127 lbs
Maximum payload | 1273 kg / 2806 lbs
Take-off distance over 50 ft | 554 m / 1817 ft
Maximum climb speed (2 engine) | 6.4 m/s / 1260 ft/min.
Maximum climb speed (1 engine) | 0.9 m/s / 177 ft/min.
Maximum cruise speed | 339 km/h / 183 knots
Service ceiling | 8580 m / 28150 ft
Range | 1460 km / 788 NM
Landing speed | 125 km/h / 67 knots

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