Helicopter

Helicopter Bell 206 Longranger III with external measuring payload

Development of the Helicopter platform

In order to widen the area of application towards low and slow flying airborne platforms enviscope GmbH decided in 2005 to develop a helicopter platform for scientific use. To provide the opportunity to run surveillance and remote sensing applications was one trigger for the investment. Another one was the possibility to perform turbulence measurements with high spatial resolution.

With Rotorflug GmbH, a company formed in 1972 and operating Bell, Agusta and Robinson helicopters from 8 locations distributed over Germany, enviscope GmbHfound a partner with a long-lasting experience in “special mission operation” of helicopters.

One of the specialities of Rotorflug is the operation of a towed sawing machine in order to cut trees along power lines. This is a challenging task for the pilots which is comparable to the plans of enviscope GmbH to use a helicopter with external payload for cloud measurements in altitudes up to 3.000m.

Basic Equipment

A helicopter of type Bell 206 L3 (Longranger) was choosen for the employment within the field of atmospheric science. The Longranger of Rotorflug is equipped with an external hook, 2 photo hatches and can carry 2 pilots, 2 scientists and measuring equipment of 200 kg for more than 2 hours in an economic way. In order to be able to carry out a wide range of atmospheric measurements we have integrated a basic set of scientific equipment for use in environmental research. The equipment was designed to provide a basic infrastructure and has been selected regarding the special requirements for operational flexibility.

The basic infrastructure consists of the following equipment:

• equipment racks for standard 19-inch housings
• power supply for the measurement equipment
• slinging gear for external loads with rope lengths of up to 150 m
• fiber optical interface to the towed platform
• platform for downward looking instruments (in preparation)
• Adaptors and covers for the two wide openings in the cabin floor for remote sensing instruments
• data acquisition system for meteorological and avionic parameters

Technical Details

Bell206 L3

Platform for scientific payloads

Application “Cloud Turbulence Masurements”

Since 1999 small-scale cloud turbulence measurements have been performed by the Leibniz-Institute for Tropospheric Research (IfT-Leipzig) with the Airborne Cloud Observation System ACTOS.
This autonomous measuring platform was developed by IfT in co-operation with enviscope GmbH and was operated successfully in several measurement campaigns.
Compared to a “static” balloon a helicopter provides much more flexibility in space and time even when slinging ACTOS. However, nobody knew what exactly the influence of the rotor downwash is to an external payload towed under a helicopter.

Investigations in the early 90’th showed that the downwash is neglectable when the helicopter is flying with relatively high velocity (40 – 50 m/s with rope length of 15m), but for the intended improvements in the data quality of turbulent fluxes measurements this velocity had to be reduced significantly.

In 2004 first studies have been done by investigations of the flight attitude of the platform and the 3D flow field around it. It could be demonstrated that the artificial disturbances at the platform are determinable by choosing carefully the correct parameters of forward velocity of the helicopter, length and material of the towing line.

Proof of concept could be gained in 2005. Both the scientific eligibility and the operational questions could be evaluated to offer new innovative measuring opportunities.

For detailed information please contact Dr. Holger Siebert, IfT Lepzig or have a look to High resolution cloud turbulence measurements at IfT.