Flight-critical

Dow-United Technologies Composite Products Inc (Dow-UT), Wallingford, Connecticut, developed an advanced resin transfer molding (AdvRTM) process for production of complex and flight-critical airframe and engine structures in RPs. The process has been further developed to improve the quality of RP aerospace components substantially at the point where two or more sections are molded together. A patented technique of shaped unidirectional fiber preforms... 

Verification (refer Fig. 1.3) is the evaluation of an implementafion of requirements to determine that they have been met (i.e. Did we build the thing right Finding 3 in the FAA study (2002) into Aeroplane Safety Assurance Processes concluded that A more robust...process that challenges the assumptions made in the safety analysis of flight critical functions is necessary in situations where a few flight critical failures (2 or 3) could result in catastrophic events. ... 

It might be thought that Lockheed were prepared to accept the obvious pain that CORE and SPARK must have inflicted because of the extreme criticality of the software under development. Actually, this view is quite wrong there was no pain. In fact the code quality improved (by one or two orders of magnitude over comparable flight critical software) and the cost of development fell (to a quarter... 

Five to ten years ago, these materials were still in the incubation period of development. Since that time, polymer research and system commercialization have progressed significantly. Desired weight benefits provided the primary impetus for producing cost-effective raw materials and developing qualified processes to ensure eventual production development. That development is now under way on flight-critical composite components in high-rate production. 

But SIAT observed an erosion of safety defenses - a shift away from the rigorous execution of pre-flight and flight-critical processes. It identified systemic issues that indicated an erosion of key defensive practices such as reduced staff levels and failed communication. The reasons for the erosion of safety defenses were suggested to be many reductions in resources and staffing, shifts toward a production mode of operation, and optimism engendered by long periods without a major mishap. 

The direct energy transfer (DET) system plays vital roles when the satellite is operating in a dark period (absence of sun light) or during the sun-illuminated portion of the flight. Critical components of this system and its block diagram are clearly identified in Figure 2.4. 

Acknowledgement. This work has been funded by the Assurance of Flight-Critical Systems element of the SSAT project in the Aviation Safety Program of NASA ARMD. 

Flight essential refers to the subset of equipment and assets necessary for continued flight and landing of an aircraft or air vehicle. Typically, this subset of equipment applies to normal operation (i.e., no failures) and is therefore larger than the subset of equipment designated as flight critical. 

Mission critical is a designation given to the minimum subset of equipment, tasks, and assets necessary to achieve completion of a mission. This includes operation under both normal and abnormal conditions. The failure or malfunction of this equipment, tasks, or assets would preclude safe and successful mission completion. Depending on the type of system and the system definitions, flight-critical equipment could be the same mission-critical equipment. As a general rule, should a contingency necessitate shutting down certain equipment, the mission critical must not be shut down. 

Whilst we are on the subject of severity classification, it may be useful to clarify the use of the term safety critical , which is often used as the basis for design guidance, continued airworthiness, and maintenance. To this purpose, the following information is summarised from a draft FAA memorandum (ANM-03-117-10), which provides the criteria for identifying flight-critical system components as applied to large aircraft. First, we need some definitions ... 

When a combination of two failures results in a hazardous failure condition, or a combination of three failures results in a catastrophic failure condition, every component in the combination is a flight-critical system component regardless of its individual hazard classification. There may be cases where a combination of four (or more) failures warrants additional review and validation. 

All components contributing to a significant latent failure condition are considered flight critical. 

ANM-03-117-10, Identification of Flight Critical System Components, FA A Memorandum (Draft), US Department of Transportation. 

The nuclear chain reaction can be modeled mathematically by considering the probable fates of a typical fast neutron released in the system. This neutron may make one or more coUisions, which result in scattering or absorption, either in fuel or nonfuel materials. If the neutron is absorbed in fuel and fission occurs, new neutrons are produced. A neutron may also escape from the core in free flight, a process called leakage. The state of the reactor can be defined by the multiplication factor, k, the net number of neutrons produced in one cycle. If k is exactly 1, the reactor is said to be critical if / < 1, it is subcritical if / > 1, it is supercritical. The neutron population and the reactor power depend on the difference between k and 1, ie, bk = k — K closely related quantity is the reactivity, p = bk jk. i the reactivity is negative, the number of neutrons declines with time if p = 0, the number remains constant if p is positive, there is a growth in population. 

Because of tank heating, fuel volatiUty is also more critical in supersonic aircraft. For example, the Concorde tank is pressurized to prevent vapor losses which could be significant at high altitude where fuel vapor pressure may equal atmospheric pressure. The tank can reach 6.9 kPa (1 psi) at the end of a flight. The need to deoxygenate fuel for thermal stabiUty in the HSCT will doubdess require a similar pressurized system. 

The establishment of a separate air supply for spaces that have a critical function (e.g., cockpits, flight-control towers, emergency-response centers) and... 

Cornish,T. J. Antoine, M. Ecelberger, S. A. Demirev, P. A. Arrayed time-of-flight mass spectrometry for time-critical detection of hazardous agents. Anal. Chem. 2005, 77, 3954-3959. 

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