Abstract: A system for maintaining documents relating to aircraft. A first set of documents is carried onboard an aircraft, in computer-readable form. The set includes (1) the aircraft maintenance manual, (2) the aircraft maintenance log, (3) the aircraft configuration log, (4) task cards, (5) pilot logbooks, or any combination of these. Copies of some, or all, of the documents in the first set are maintained, in computer-readable format, at a ground-based location. As operation of the aircraft occurs, changes will occur in either, or both, sets of documents. The changes are then copied into the other set, to maintain consistency.

Abstract: A document management system. The system uses well known MACs, Message Authentication Codes, or equivalents. In general, an MAC is used to authenticate a copy of a document. First, the document is fed to a specific algorithm, which produces the MAC. Then a copy-to-be-verified is fed to the same algorithm. If the same MAC is obtained, the copy is taken as authenticated. Under the invention, when maintenance is undertaken on an aircraft, a technician uses a computer to generate a digital document describing the maintenance. An MAC is generated for the digital document. The technician encrypts the MAC, using the technician's encryption key. The encrypted MAC is attached to the digital document, and the pair is stored. Now, any copies of the document can be validated by (1) de-crypting the MAC and (2) validating the document using the MAC. In one embodiment, no paper documents are generated, nor signed, at the time of the maintenance.

Abstract: Apparatus which is selectively operable at low frequencies (less than 5,000 Hz and preferably between about 100 Hz to about 1,000 Hz) breaks up jets of high-viscosity fluid into monodisperse droplets. The apparatus includes a housing having a chamber, a piston disposed in the chamber, a magnetic-coil system operably attached to the housing and to the piston, and an oscillator for driving the magnetic-coil system. The housing and the piston define a reservoir for receiving a supply of high-viscosity fluid which is acted upon by oscillating motion of the piston to impart pressure perturbations on the supply of fluid so that the fluid upon discharge from the reservoir separates and breaks up into a plurality of monodisperse droplets. Also disclosed is a method for optimizing the performance of the apparatus to minimize the power required for droplet formation.