Method for determining the horizontal airspeed of helicopters in low speed ranges

US4702106A · kind A · utility

Assignee

• LITEF GmbH · DE

Inventors

• Wolfgang Hassenpflug · Freiburg im Breisgau, DE
• Rainer Schwable · Garbsen, DE

Key dates

• Filing date: Jun 6, 1986
• Grant date: Oct 27, 1987
• Expiry date: Jun 6, 2006

Classification

• Technology area (CPC G): Physics
• CPC primary: G01P5/00
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method is disclosed for determining the horizontal airspeed of helicopters in low speed ranges. At least three control functions, .theta..sub.o,i (collective pitch), .theta..sub.s,i (longitudinal control) and .theta..sub.c,i (lateral control) are measured. The magnitude of the horizontal airspeed, V.sub.H,i, is determined from its known relationship to .theta..sub.o,i. This magnitude is included in non-linear calibration equations .theta..sub.s (V.sub.H, .psi.) and .theta..sub.c (V.sub.H, .psi.) and control profiles .theta..sub.s (V.sub.H,i, .psi.) and .theta..sub.c (V.sub.H,i, .psi.) are derived therefrom. The measured values .theta..sub.s,i and .theta..sub.c,i are applied to the respective control profiles and corresponding phase pairs .psi..sub.s,1, .psi..sub.s,2 and .psi..sub.c,1, and .psi..sub.c,2 located. The pairs are compared and the incident flow angle .psi..sub.i is determined as the value common to the two pairs. From this information, the components of the horizontal airspeed are found from the relationships: EQU V.sub.x,i =V.sub.H,i Cos .psi..sub.i EQU V.sub.y,i =V.sub.H,i sin .psi..sub.i.