Flight Mechanics, Flight Control and Aeroelasticity

CERTT-FBW23 - Certification Technologies for Fly-by-Wire of EASA CS23 Aircraft

CERTT-FBW23 is a joint research project that will last 39 months (01.01.2014 – 31.03.2017). Its aim is the development of methodical and technological fundamentals for the certification of a fly-by-wire system for CS23 aircraft. It is promoted by the Federal Ministry for Economic Affairs and Energy (BMWi) and is part of the Federal Aeronautical Research Programme LUFO V.


The ability for aerial work or individual transport of small aircraft that are certified according to EASA Certification Specification CS23 can be significantly improved by the use of intelligent flight control, flight guidance and flight management systems. Such systems allow to follow flight trajectories economically and with high precision under all visual conditions. Simultaneously, these systems increase safety, for example by protecting the aircraft from leaving safe ranges of airspeed or by preventing collisions with obstacles or other aircraft. Unmanned or remotely piloted versions of such an aircraft are suitable to facilitate flights of extremely long endurance.

In order to realize the required sophisticated functions, it is necessary to complement or replace the classical mechanical flight control systems by an electronic system as it is already done in commercial airliners (CS25 aircraft). Technological developments and increasing use of by-wire technologies in other industrial sectors have brought the price-performance ratio for avionics components towards an affordable range. For CS23 aircraft, the effort for the qualification of hard- and software and for the certification of the airplane are the main obstacles for introducing electronic flight control systems in CS23 aircraft. The main reason is that those systems are safety critical and therefore underlie very strict processes for development, approval and quality management.


Today, the complex and safety critical technology of electronic flight control systems (Fly-by-Wire, FbW) is almost exclusively used for aircraft of the CS25 category. Aim of the joint research project CERTT-FBW23 is to develop new technological and methodical approaches to make FbW technology attractive (from a cost perspective) for the use in CS23 aircraft, especially for Class I/II/III. This will open up advanced and new applications for aircraft of the CS23 category like efficient and intelligent utility aircraft which will be able to carry out special missions with high demands (duration, precision, complexity, etc.) almost autonomously. In order to cover a wide range of applications, such aircraft have to be equipped with extensive avionics and electronic flight control systems whose software is at least developed according to RTCA DO-178C Design Assurance Level C (DAL C).

To reach this aim, the activities of several EU and LUFO projects have been combined:

  1. the LUFO4 projects LAPAZ and LAPAZ2,
  2. EU project SAFAR and
  3. LUFO4 project FLYSMART-FBW23.

The scientific and technological aim of CERTT-FBW23 is to provide the methodical and technological fundamentals for the certification of such a system. Furthermore, decisive cost drivers at the certification effort shall be identified and the basis for a fast and efficient certification process shall be created.


AP100basics of process EASA CS23 / FBW on aircraft levelDefinition of the certification-related framework of the development process for CS23 Class I/II/III. Determination of the certification-related requirements on aircraft level and system level. Definition of the certification programme and the corresponding development process.
AP200basics of qualification / hardware technologyAssessment of architecture and hardware of the flight control system (Fly-by-Wire hardware including communication network) regarding a certification in CS23 aircraft and realisation of a hardware/software validator.
AP300basics of qualification / platform technologyConcept, implementation and validation of a procedure for automatic test case generation by means of a Tool Suite for an instance of the platform.
AP400basics of qualification / flight control functionsDefinition of a process and the associated procedures, methods and tools for:
1. efficient qualification of Flight Control Laws according to CS23 and
2. the corresponding flight control software according to RTCA DO-178 C.
The demonstration will be conducted by using the flight control functions that have been developed in the LAPAZ/LAPAZ2 projects for the STEMME S15.

Project Partner

  • Cassidian Airborne Solutions GmbH
  • Smart Embedded Technologies (SET) GmbH
  • Institute of Aircraft Systems (ILS) at the University of Stuttgart
  • Department for Flight Mechanics, Flight Control and Aeroelasticity (FMRA) at the Technical University of Berlin

Task of the TU Berlin

The Department for Flight Mechanics, Flight Control and Aeroelasticity is responsible for work package AP400. In AP410, procedures, methods and tools for the certification of automatic flight control systems according to CS23 and RTCA DO-178 shall be developed. This will be realized by using the flight control functions that have been developed in the LAPAZ/LAPAZ2 projects for the STEMME S15. The focus will be on cost-efficient methods in order to make them applicable for CS23 aircraft. In particular, the tasks will be:

  1. Development of methods and tools for efficient, automated certification of flight control functions according to EASA Certification Specification CS23 that shall be tailored to the special certification demands of CS23 but should be valid universally. This means that they shall not be dependent on a specific airplane type (exception: single- or twin-engined aircraft);
  2. Development of an automatic, model based method and corresponding tools for certification of flight control software according to RTCA DO-178 that shall support the correct transformation of the software requirements from a block diagram to a verified code.

Requirements are essential for the verification of the flight control functions and for the definition of tests to be performed. The requirements have to be written and managed in an electronically evaluable manner. The guidance provided by SAE ARP4754A, RTCA DO-178C and its Supplements for Model Based Design (RTCA DO-331) have to be taken into account during the requirements management process. A complete traceability is necessary in order to deal with the complexity and to guarantee the consistency of the results.
For an efficient test evaluation it is necessary to derive mathematical formulated criteria from the textual requirements so that an algorithm can decide clearly whether the criteria are fulfilled. In the LAPAZ project, a test environment has been developed for controller development that already allows automated verification tests to be performed while using high quality simulations of the aircraft and its control system. This test environment shall be extended with additional evaluation criteria.