Experimental and numerical investigation of longitudinal static stability and stick force gradient of an ultralight aircraft
(2020) MMKM10 20192Innovation
- Abstract
- The main goal was to improve the longitudinal flying qualities by investigation of low stick forces and pitch-sensitivity of the ultralight aircraft, BW600-RG and to provide design suggestions for improvement. Computational fluid dynamics (CFD) was used to estimate stability derivatives and coefficients for calculation of the flying qualities derivate stick force gradient. Flight testing was conducted to validate the calculated stick force gradient with experimental data and evaluate effects of passive flow control devices on the elevator. Finally, the effects of aerodynamically increasing the stick force gradient by tail volume ratio and elevator-to-tail chord ratio were analysed.
The investigated flight condition involved clean... (More) - The main goal was to improve the longitudinal flying qualities by investigation of low stick forces and pitch-sensitivity of the ultralight aircraft, BW600-RG and to provide design suggestions for improvement. Computational fluid dynamics (CFD) was used to estimate stability derivatives and coefficients for calculation of the flying qualities derivate stick force gradient. Flight testing was conducted to validate the calculated stick force gradient with experimental data and evaluate effects of passive flow control devices on the elevator. Finally, the effects of aerodynamically increasing the stick force gradient by tail volume ratio and elevator-to-tail chord ratio were analysed.
The investigated flight condition involved clean aircraft configuration in cruise. The stability of the aircraft was evaluated by the measure of stick-fixed and stick-free static margins. 3D, steady-state, RANS simulations in STAR-CCM+ were used to predict the stick-fixed static margin, which was found to be in reasonable agreement with the analytically calculated stick-fixed static margin, though slightly lower. Additionally, a virtual disk model was implemented to study the indirect propeller effects. However, no significant effect was found regarding longitudinal static stability. Hinge moment coefficients were acquired using CFD to calculate the stick-free static margin and in turn the stick force gradient.
The stick force gradient measurement from the flight testing was in fair agreement, within 15%, compared to the calculated stick force gradient. It was determined that the inadequate stick force gradient was primarily due to unfavourable elevator lift and hinge moment characteristics resulting in a low stick free static margin. Increasing the tail volume ratio by extension of fixed tips and slightly reducing the elevator-to-tail chord ratio was examined to be the most effective way of increasing the stick force gradient for the aeroplane. (Less) - Popular Abstract
- In addition to designing an aircraft to be able to fly and manoeuvre, the experience of piloting the aircraft must also be considered. This is addressed by the aircraft’s flying qualities to ensure that the aircraft has acceptable response characteristics, mission performance and flight safety. This thesis investigates the flying qualities of the ultralight aircraft BW600-RG and addresses the ease of controlling the aircraft in pitch, referred to as longitudinal flying qualities. The longitudinal flying qualities primarily depends upon the aircraft’s stability characteristics, the mechanical steering system and control surface aerodynamics. While flying qualities tend to be rather subjective, formulated in terms of pilot opinion, they have... (More)
- In addition to designing an aircraft to be able to fly and manoeuvre, the experience of piloting the aircraft must also be considered. This is addressed by the aircraft’s flying qualities to ensure that the aircraft has acceptable response characteristics, mission performance and flight safety. This thesis investigates the flying qualities of the ultralight aircraft BW600-RG and addresses the ease of controlling the aircraft in pitch, referred to as longitudinal flying qualities. The longitudinal flying qualities primarily depends upon the aircraft’s stability characteristics, the mechanical steering system and control surface aerodynamics. While flying qualities tend to be rather subjective, formulated in terms of pilot opinion, they have in this thesis been quantified and evaluated through the measure of stick force gradient. The stick force gradient essentially describes the variation in stick force, or control force, felt by the pilot following a departure from a steady flight condition. Computational fluid dynamics (CFD) and flight testing were used for analysis and validation and were found to be in reasonable agreement. CFD was used to provide design suggestions to achieve the desirable longitudinal flying qualities. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9016802
- author
- Månsson, Philip LU
- supervisor
- organization
- course
- MMKM10 20192
- year
- 2020
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- stick force gradient, longitudinal static stability, flying qualities, flight mechanics, CFD
- language
- English
- id
- 9016802
- date added to LUP
- 2020-06-15 10:01:32
- date last changed
- 2020-06-15 10:01:32
@misc{9016802,
abstract = {{The main goal was to improve the longitudinal flying qualities by investigation of low stick forces and pitch-sensitivity of the ultralight aircraft, BW600-RG and to provide design suggestions for improvement. Computational fluid dynamics (CFD) was used to estimate stability derivatives and coefficients for calculation of the flying qualities derivate stick force gradient. Flight testing was conducted to validate the calculated stick force gradient with experimental data and evaluate effects of passive flow control devices on the elevator. Finally, the effects of aerodynamically increasing the stick force gradient by tail volume ratio and elevator-to-tail chord ratio were analysed.
The investigated flight condition involved clean aircraft configuration in cruise. The stability of the aircraft was evaluated by the measure of stick-fixed and stick-free static margins. 3D, steady-state, RANS simulations in STAR-CCM+ were used to predict the stick-fixed static margin, which was found to be in reasonable agreement with the analytically calculated stick-fixed static margin, though slightly lower. Additionally, a virtual disk model was implemented to study the indirect propeller effects. However, no significant effect was found regarding longitudinal static stability. Hinge moment coefficients were acquired using CFD to calculate the stick-free static margin and in turn the stick force gradient.
The stick force gradient measurement from the flight testing was in fair agreement, within 15%, compared to the calculated stick force gradient. It was determined that the inadequate stick force gradient was primarily due to unfavourable elevator lift and hinge moment characteristics resulting in a low stick free static margin. Increasing the tail volume ratio by extension of fixed tips and slightly reducing the elevator-to-tail chord ratio was examined to be the most effective way of increasing the stick force gradient for the aeroplane.}},
author = {{Månsson, Philip}},
language = {{eng}},
note = {{Student Paper}},
title = {{Experimental and numerical investigation of longitudinal static stability and stick force gradient of an ultralight aircraft}},
year = {{2020}},
}