FLUG REVUE August 2006: DLR HALO laboratory outfitting under way

August 2006

GULFSTREAM 550 FOR HALO

By Mathias Gründer

A Gulfstream 550 is currently undergoing transformation in Oberpfaffenhofen into the High Altitude and Long Range Research Aircraft (HALO) which in future will serve as an observation platform for research on the atmosphere.

HALO

“Why does the conversion process take three years?” Dr. Andreas Giez, responsible for the sensor equipment on research aircraft at the German Aerospace Research Establishment (DLR) in Oberpfaffenhofen, cannot suppress a slight smile at the reporter's question. “On the upper side alone we plan to cut 12 'holes' of varying sizes, then another 11 on the underside, and there are six windows to be modified as well. On top of that there are three optional stores stations under the wings, there are even hard points on the winglets, a sensor mast on the nose etc. etc...”

Not to mention the interior cabin furnishings found in a standard installation, which have to be reconfigured. Then it soon turned out even as funds were being approved for the new aircraft that only Gulfstream was in a position to carry out the full refurbishment required by the scientists to the highest standard of quality and within the stipulated financial framework. After all, the American engineers already had extensive experience of special equipment configurations for their business jets, especially for military customers.

In any case, after over 30 years of excellent experience with the Falcon, which is still flying with the DLR, a new aircraft had to be purchased. “The Falcon is still in good shape and has relatively few flying hours for its age,” says Dr. Giez. However, its range and ceiling altitude are no longer sufficient for current and future research projects, and its payload capacity is also somewhat low. “Nevertheless, we will still get a good price for the aircraft, even if we definitely want to sell it outside Europe. Who wants to have the competition just next door?”

The application for funding to the tune of around €70 million, half of which is for the “green” aircraft, was submitted back in 2001, and when it was finally approved, a project team consisting of only five specialists began organising a user survey on the basis of experience with the Falcon. The DLR is only the operator of the aircraft, which is actually owned by a HALO user community numbering over 30 German institutes from environmental and climate research establishments.

These potential users reported their wishes as regards research projects and the associated tools and energy requirements. This was then used to draw up an overview of the modification work to be expected. The scientists were also asked to look 30 years ahead into the future, if possible, as the new aircraft is to be operated for at least that long. For some of the equipment now being installed there is not currently any specific requirement; it is simply the case that it might be needed in the future. This is the position, for example, of the underwing hard points, mounting brackets for approx. five metre long equipment containers, similar to the weapons pods carried on fighter aircraft.

Plenty of work left for specialists in the DLR institutes

These modifications, like others, are designated optional and are shown as such in the diagram on page 129. The majority of the modifications can already be made on the basis of Gulfstream specifications. In the case of other modifications, the American specialists still have some calculations to perform, while still others are under development in DLR institutes. “After all, we are an approved development organisation, and our aerodynamicists and aeroelastics experts still have quite a bit to do,” says Dr. Giez.

It soon also became clear that another equipment cabinet would be required behind the compartment for the on-board electronics to accommodate all the on-board systems which in a “normal” aircraft are accommodated below the floor plates. Extensive new wiring with 17 power distribution boxes has to be installed, bearing in mind that it has to be possible to quickly replace all the experimental equipment on board, depending on the particular mission to be flown next. Experience suggests that around ten different payloads will need to be installed every year. The cables and pipes in turn have to have special gaskets if they penetrate any pressure bulkheads. Such pipes affect air vents, for example, if external air is to be analysed, and also cooling of the equipment.

“Especially during measurement campaigns in hot countries we have cooling problems on the ground or at low altitude flight,” explains Dr. Giez. That is why a special liquid chiller is installed in the right-hand rear wing root. There are rails not only on the floor, to attach seats, but also at shoulder height on the fuselage sides, to which the experiment cabinets will later be attached. For prolonged flights there is even a requirement to have a small kitchen on board, while the mission power rack for the power supply (55kW) is to be moved towards the rear. The Gulfstream 550 can also take additional payload in the rear, even though the engines are already attached there. There is a spacious luggage compartment there, which will also be able to accommodate further equipment in the future. The aircraft, which is only flown mechanically to avoid the possibility of disruptive influences on the equipment, can in fact carry three tonnes' more payload than the standard model.

Numerous other user wishes had to be taken account at the planning stage. These are now taking shape at RUAG on the other side of Oberpfaffenhofen airfield – anti-icing for all the attachments, a video system, a system for rapid data transmission and many others besides. When one bears all this in mind, perhaps a three year construction time is not so long after all.

From FLUG REVUE 8/2006

Last updated 14 July 2006

FLUG REVUE, Ubierstr. 83, 53173 Bonn, Germany