How future aircraft can benefit from a steerable main landing gear for crosswind operations

Abstract

Many unconventional configurations for future aircraft, such as aircraft with very high aspect ratio wings or blended wing bodies, suffer from adverse flying characteristics for crosswind operations. Although the reasons for such undesirable behavior are different, coming from either tight geometric limitations, such as small bank angle allowances close to ground, or unfavorable flying qualities in the lateral motion, the consequences are challenging characteristics for take-off or landing under crosswind. In the presented study, a crosswind landing assistance system that makes use of a steerable main landing gear was designed and demonstrated in simulator trials. With such a system, the so-called de-crab maneuver is obsolete and the aircraft can touch down in crabbed motion. During roll-out on ground, the de-crab is performed automatically and the aircraft is kept on the runway centerline. A special concept for manual steering during this automatic de-crab on ground is introduced in the paper. The system is demonstrated in an A320 full-flight simulator with airline pilots, showing a good performance of the system and satisfactory pilot acceptance. The simulation results also show that the side forces acting on the landing gears could be reduced significantly with steerable main landing gears. This raises the hope that with such a system, the landing gear could possibly be designed lighter, saving at least some of the additional weight and cost for the necessary steering actuators of the main landing gear.

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Abbreviations

AFS:

Auto-flight system

ATRA:

Advanced technologies research aircraft

AVES:

Air vehicle simulator

DLR:

German aerospace center

EGT:

Exhaust gas temperature

EPR:

Engine pressure ratio

FCS:

Flight control system

FHS:

Flying helicopter simulator

FMS:

Flight management system

GS:

Ground speed

HTP:

Horizontal tail plane

IAS:

Indicated airspeed

ILS:

Instrument landing system

METAR:

Meteorological aerodrome report

NASA:

National aeronautics and space administration

SFB:

Sonderforschungsbereich (collaborative research center)

STOL:

Short take-off and landing

Fx, Fy, Fz :

Longitudinal, lateral, and vertical component of the landing gear force (N)

H :

Altitude (ft)

k p :

Gain for proportional controller (−)

ny, nz :

Lateral and vertical load factor (−)

p tire :

Tire pressure (N/m2)

T Track :

Time constant (s)

u, v :

Longitudinal and lateral velocity component of tires (m/s)/(kts)

V :

Air speed (m/s)/(kts)

V Ground :

Ground speed (m/s)/(kts)

XTE RWY :

Cross-track error on the runway (m)

δ brake :

Proportion of braking applied (−)

\( \eta_{\text{NG}} \) :

Nose gear steering angle (°)

\( \eta_{\text{MG}} \) :

Main gear steering angle (°)

\( \mu_{\text{s}} \) :

Side-friction coefficient (−)

\( \mu_{\text{b}} \) :

Brake-friction coefficient (−)

\( \mu_{\text{r}} \) :

Roll-friction coefficient (−)

Ψ :

Aircraft heading (°)

Ψ RWY :

Runway heading (°)

ΔΨcrab :

Crab angle (°)

τ :

Skid angle (°)

\( \chi \) :

Track angle (°)

\( \Delta \chi_{\text{chase}} \) :

Chase angle (°)

\( \chi_{\text{CMD}} \) :

Commanded track angle (°)

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Acknowledgements

This work was supported in part by funding from the Horizon 2020 Framework Programme (Grant No. 640597).

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Vechtel, D. How future aircraft can benefit from a steerable main landing gear for crosswind operations. CEAS Aeronaut J 11, 417–429 (2020). https://doi.org/10.1007/s13272-019-00410-4

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Keywords

  • Crosswind landing
  • Steerable landing gear
  • Pilot assistance
  • Simulator study