GM No 1 to Appendix XII – Lead Flight Test Engineer (LFTE)
CAA ORS9 Decision No. 1
LFTEs are Flight Test Engineers (FTEs) that have specific duties and privileges as a flight test crew member, to operate the test aircraft’s systems either directly or through dedicated flight test instrumentation, that could significantly interfere with the aircraft basic systems (such as flight controls and engine controls), or that could significantly impact aircraft stability and control (e.g. through weight and balancing flight management or flight control configuration changes). As an example, an LFTE could be permitted to shut down the engines or change the engine parameters through controls which are not accessible to the pilots.
The word ‘assisting’ (the pilots) should be understood in the sense of the critical actions (e.g. actions described above) which could be performed by the LFTE, if requested by the flight test order and agreed by the pilot-in-command.
Flight test categories
The purpose of this GM is to help operators to:
1. determine whether an operation is a flight test; and
2. to classify the flight test.
Flight test categories are defined in Appendix XII to Part-21, and are described in this GM in such a manner that an operator who wishes to classify a flight, should first determine whether the flight is defined as a flight test according to the ‘General’ paragraph. The operator should then determine if the flight test falls within the definition of Category 1 before moving to Category 2 and so on throughout the list until the correct category is determined.
Other types of flights, such as maintenance check flights, are not included in the flights described in this GM and are, therefore, not subject to it.
a) General
The testing of aircraft performance, handling qualities and systems, including checking compliance with Certification Specifications (CSs), requires specialist techniques, skills and theoretical knowledge. Therefore, flight test training and specific experience is required to enable a test crew to:
— safely perform systematic and comprehensive flight envelope exploration;
— acquire specific skills and abilities for some particularly difficult tests;
— mitigate risks by anticipating potentially hazardous situations, and by applying methods that permit the safest flight possible in these situations;
— understand the relevant CSs; and
— learn methods to assess whether the aircraft or its systems comply with these regulations.
It should be noted that the content of the flight test determines its category, and the flight test category determines the required competence of the crew.
Nevertheless,
— flight tests of an aircraft which does not have a Type Certificate (TC) should be considered either as Category 1 or Category 2 flight test until the type has been certified; and
— flight tests for a modification of an already certified type may be Category 1, 2 or 4, depending on the purpose of the test.
The rationale for this difference is the fact that a new aircraft type is considered under continuous assessment until the TC is issued.
Cases where more than one aircraft is involved in a flight test point:
Chase flights are a typical example of flights in which more than one aircraft is involved. Every aircraft participating in the test point(s) should be evaluated through this classification. The guiding principle should be the role of the crew of the chase aircraft in the safety of the aircraft under test or of the formation.
b) Category 1 flight test
Below are examples of flight tests to be considered as Category 1:
— Fixed-wing aircraft: VMCG, VMU, spinning, initial stalling, or for rotary-wing aircraft: H/V diagrams and Category A engine failures.
— Where encounter of surprising or even hazardous flight characteristics can be expected.
— Upon determination, aircraft handling and performance in conditions where at least one of the following parameters is approaching the actual limits of the aircraft envelope: altitude, attitudes, weights, CG, speed/Mach, stalls, temperature, engine and aerofoil performance.
— Where the embodiment of new systems is anticipated to significantly affect the aircraft’s handling or performance characteristics.
— When the crew of the chase aircraft has the duty to assist the test aircraft crew in recovering from a critical flight situation (i.e. assist the spinning aircraft crew in assessing the spin or triggering recovery actions).
c) Category 2 flight test
Below are examples of flight tests to be considered as Category 2:
— The flight test envelope has already been opened and it has been demonstrated that the general behaviour of the aircraft is adequately safe and there are no unsafe flight characteristics.
— All-engines-operating climb performance.
— Cruise performance.
— Static stability demonstration.
— Function and reliability flights.
— Systems tests of autopilot or guidance/warning systems such as Terrain Awareness and Warning System (TAWS) or Airborne Collision Avoidance System (ACAS), when the modes themselves are tested, requiring operating the aircraft by deviating from the standard operational procedures. Additionally, in the case of embodiment of such systems on an already certified aircraft, when the system integration in an existing cockpit requires a more global crew procedure assessment — for example, when the system has been integrated in cockpit screens and a centralised warning system which requires a new cockpit procedure assessment (note that some system tests may fall under Category 4; see below).
d) Category 3 flight test
These flights are commonly referred to as production flight tests. They are performed on each new aircraft of a type that is already certified. The aim is to check that the aircraft and its systems are working properly and conform to the certified type. As the type is already certified, the behaviour of the aircraft is known.
However, experience has shown that during production flight tests of a new aircraft, unexpected failures can occur which could not be described in the Aircraft Flight Manual (AFM). For this reason, it is considered that special experience should be required.
It should be noted that a TC or a Supplemental Type Certificate (STC) should have been issued in order for a production flight test to be considered as Category 3. Until a TC or STC is issued, any flight, including production flight tests, will be Category 1, 2 or 4 according to classification criteria.
It should be noted also that if the flight of an aircraft with a TC or STC requires flying outside the AFM limitations, then this flight should be considered as Category 1 or Category 2 flight.
e) Category 4 flight test
Typical Category 4 flights are those required by a DOA to demonstrate compliance with the airworthiness requirements of ‘not yet approved data’:
— cabin conversion;
— zonal drying system installation;
— Emergency Locator Transmission (ELT) installation;
— new cabin installation;
— cabin aircraft location pictorial system installation;
— new entertainment system installation;
— SATCOM and telephone installation; and
— new radio equipment installation.
Category 4 includes also flights after embodiment of guidance/warning systems which are not Category 2 and for which:
— good functioning test only is required; and
— there is no need to fly the aircraft outside the AFM limitations.
The modification should not affect the behaviour of the aircraft in any way.
However, there may be modifications whose tests, despite the fact that they have no influence on the behaviour of the aircraft, require flying in conditions which deviate significantly from the standard operational use of the aircraft. These unusual flight test conditions may require classifying the flight as Category 2, as mentioned above. The typical example to consider here is the approval of the modification of an already certified TAWS system. In this situation, it is required to fly at very low altitude and/or towards high terrain. Such a flight can be classified as Category 4 flight on a light aircraft (or helicopter) because that flight test is performed in a domain corresponding to the normal operation of the aircraft, whereas the same flight performed with a heavy CS-25 aircraft, especially if it needs to be flown in clean configuration significantly below gear and flaps warning heights, should be classified as Category 2 because such a flight does not correspond to the normal use of the aircraft and needs to adopt specific testing procedures as demonstrated in the Category 2 training.