In-flight loss-of-control (LOC-I) still poses a severe threat to today’s commercial aviation. Hence, we review the literature for non-linear analysis and control methods of LOC-Iand upset recovery. Using state-of-the-art methods such as continuation theory and reachability estimation, we sketch an analysis of an aircraft’s flight envelope in terms of its trim conditions and propose control approaches both within and outside the envelope.

https://hal-enac.archives-ouvertes.fr/hal-01543046/document

Non-linear Analysis and Control Proposal for In-flight Loss-of-control

As in-flight loss of control has remained a severe threat to aviation, aeronautical research designed several approaches for upset recovery, few of which has been demonstrated in flight tests.
The on-going success of micro air vehicles, however, rises the possibility of cheap and flexible flight demonstrations. In this paper, we present the concept of and first steps towards an aerial experimental platform for upset recovery: EDURA. EDURA is part of the CONVEX project to investigate,develop, and demonstrate non-linear upset recovery control laws in a fixed-wing MAV.

https://hal-enac.archives-ouvertes.fr/hal-01587228/document

EDURA: an Evolvable Demonstrator for Upset Recovery Approaches with a 3D-printed Launcher

While in-flight loss of control has remained a severe threat to aviation, few of the upset recovery approaches designed by aeronautical research has been demonstrated in flight tests. Enabled by the ongoing success of micro air vehicles, we discuss the concept of an aerial experimental platform for upset recovery, EDURA (Evolvable Demonstrator for Upset Recovery Approaches), allowing cheap and flexible flight demonstrations. The aerodynamic coefficients of the vehicle presented here are numerically computed and extended to a full-envelope aerodynamic model using piece-wise polynomials in pre-and post-stall. Eventually, the aerodynamics are verified with wind-tunnel force measurements for a 3D-printed mock-up.

https://hal-enac.archives-ouvertes.fr/hal-01857275/document

Analysis of the Aerodynamic Coefficients for the Evolvable Demonstrator for Upset Recovery Approaches with Evaluation in the Wind-tunnel

In the case of total flight control system failure, engine thrust may be the only way to control an airplane. There is a large class of transport jet airplanes with the twin engines mounted on the aft fuselage. The techniques for controlling these airplanes with engine thrust (Throttles-Only Control (TOC) has been briefly studied. Because the engine thrust line is either at or above the vertical center of gravity for these aircraft, they require different techniques from the underslung engines configuration for TOC. The MD-90 is a relatively recent version of this class of aircraft, with highbypass turbofan engines, a digital flight management system and a digital autopilot and autothrottle. A very brief first look at TOC in an MD-90 high-fidelity level D simulator in 1995 showed promising results. Therefore, a further study using a desktop simulation has been conducted to determine the TOC characteristics of the MD-90 and to investigate and develop methods for control sufficient for survivable runway landing. One promising method is to use the speed-hold autothrottle to stabilize and control the flightpath. Tests were flown for a no-flaps configuration at a speed of 200 and 220 kts, Flaps 15 at 155 kts, and Flaps 30 at 137 kts in this brief look at the concept.

Preliminary Study of the Use of an Autothrottle to Improve The Throttles-Only Control Characteristics of a Twin Jet Transport Aircraft With Aft-Mounted Engines

If normal aircraft flight controls are lost, emergency flight control may be attempted using only the thrust of engines. Collective thrust is used to control flightpath, and differential thrust is used to control bank angle. One issue is whether a total loss of hydraulics (TLOH) leaves an airplane in a recoverable condition. Recoverability is a function of airspeed, altitude, flight phase, and configuration. If the airplane can be recovered, flight test and simulation results on several transport-class airplanes have shown that throttles-only control (TOC) is usually adequate to maintain up-and-away flight, but executing a safe landing is very difficult. There are favorable aircraft configurations, and also techniques that will improve recoverability and control and increase the chances of a survivable landing. The DHS and NASA have recently conducted a flight and simulator study to determine the effectivity of manual throttles-only control as a way to recover and safely land a range of transport airplanes. This paper discusses TLOH recoverability as a function of conditions, and TOC landability results for a range of transport airplanes, and some key techniques for flying with throttles and making a survivable landing. Airplanes evaluated include the B-747, B-767, B-777, B-757, A320, and B-737 airplanes.

Kerry Wilson

Papers

Manual Throttles-Only Control Effectivity for Emergency Flight Control of Transport Aircraft