FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1949
1949 - 1677.PDF
FLIGHT, 29 September 1949 • 441 GAS-TURBINE SAFETY Anti-icing and Fire-prevention Arrangements on D.H. Ghost Civil Installations POWER-PLANT icing is admitted to be one of the chiefoperational problems likely to be met by the new genera-tion of gas-turbine-powered transports, but recently a more confident note has bt-en discernible when those engagedon the development of anti-icing systems have been approached ior information. There now seems reason to believe thatdamage as a result of ice entering compressor air-intakes can be averted quite easily in the case of centrifugal-compressorturbojets and turboprops. One of the few power plants in which anti-icing, fire-extin-guishing and other systems have reached an advanced stage is that of the civil de Havilland Ghost turbojet as fitted inthe Comet. The makers state that the centrifugal impeller is of sufficiently robust construction to permit quite large piecesoi ice to enter the compressor without causing damage. More- over, centrifugal effects prevent ice formation on the impellerblades. Remedial measures are therefore limited to the pre- vention of ice accretion in the air-entry ducts and on the front-bearing fairing and support vanes. Although the power out- put of a gas turbine is adversely affected if the temperature ofthe intake air is raised, the performance of the Ghost suffers little, if at all, as a result of the heating of the duct surfacesas the air temperature does not rise appreciably. Two sources of heat are employed. One is from a bleed muffon the jet pipe, the muff being an annular duct surrounding the jet pipe just to the rear of the turbine. The hot air thusbled-off is piped forward to the nose portion of the air-intake fairing. The flow is controlled by a valve, and before beingpassed round the leading edge of the intake the very hot air is diluted with cold air Irom a small forward-lacing intakeOperation of the syst«-m is clearly indicated in the; accompany- ing diagram. The Other source of heat—employed for the fair-ing for the front bearing and for the support vanes within the intake—is the circulation of hoi oil from the engine systemthrough these components. Accessories and auxiliaries are contained in a still-air zonebetween the cowling and the intake duct, and are thus out of the main airflow and protected from icing. Regarding fire control, de Havillands point out that thedirect entry to the single-sided impeller enables the intake air to be isolated from all the cowled compartments" around theengine. Thus, the nacelle can be divided into compartment-; separated by fireproof bulkheads which greatly reduce the riskof a nacelle fire, and the arrangement also results in a con- siderable economy in extinguisher fluid. The three zones onthe Ghost are: (1) forward of the fire-wall on the compressor casing; (2) between this and the partition at the turbineshroud; and (jj rearward around the jet pipe, which carries its own shroud acting as a fire-wall for the pipe. A venturi cuflon the jet nozzle induces a strong airflow from Zone 2 along the Zone 3 annulus This has the double purpose of ventilat-ing Zone 2. and ensuring that the temperature of the jet-pip." shroud is kept at a safe level during ground runs. Incident-ally, in the event of fire this airflow does not result in rapid dilution of the fire-extinguishing gas, because the pilot's firstaction is to cut off the high-pressure fuel cock. This culs the power of the engine, and the venturi suction is reduced tonegligible proportions. FIRE EXTINGUISHER THERMAL BOTTLES ANTI-ICING ZONE1 SPRAY RING ZONE 2SPRAY RING HOT GAS BLEED MUFF HOTCOLD HOT SCOLD • FIRE EXTINGUISHER HEATED BY HOT OIL CIRCULATION VENTURI CUFF THERMALANTI-ICING MIXINGCHAMBER Thermal anti-icing, fire extinguishing and ventilating systems for the Ghost. The nacelle is divided into three zones and simple toggle-fastened cowlings form the enclosure. An engine change can be accomplished, cowled to recowled, within the hour. O EVALUATING THE HELICOPTER N Saturday afternoon last, a notable paper entitled Some Economics of the Helicopter—Present and Future, was presented before the Helicopter Association of Great Britain by Mr. L. S. Wigdortchik, A.F.R.Ae.S., who is Chief Experi- mental Engineer of the British European Airways Helicopter Unit. Too often, in lectures dealing with the economics of air transport, the pro-aeronautical bias of the lecturer tends to make him gloss over the unrelenting necessities of economic survival. These are usually manifested in the plain argument of how much return can be derived from a given outlay and, in general, aircraft do not show up as well on this standard as do most other vehicles. Mr. Wigdortchik, however, had composed a paper of admirably balanced proportions, and it was evident that whatever professional bias he has towards the helicopter, he is not blind to the severely practical economic standards which it must fulfil if it is ever to become a busi- ness proposition. His lecture' was the more important by reason of the fact that it was almost certainly the first of its kind based on a considerable practical experience of helicopter- operating economics. A digest will appear in Flight next week. Following edification in the afternoon, members of the F II . . . : ..-...-•..•.......; • . •• " Helicopter Association gathered for their annual dinner in the evening at No. 6, Stanhope Gate, Park Lane; a most enjoy- able and convivial affair. PROTECTION BY PHOTO-CELL SOME of the many industrial applications of electroniccontrol equipment, particularly in conjunction with photo- electric detection, were shown at a recent demonstration staged by Radiovisor Parent, Ltd., of 1, Stanhope Street, London, N.W.i. Among the apparatus demonstrated was a smoke-detector for the protection of buildings from fire, in which two photo- electric cells are illuminated by independent light-beams and electrically "balanced" so that equal interruption of both beams (e.g., by fog) will have no effect,,.'whereas independent interruption, as would be caused by smoke from a fire, ener- gizes an alarm circuit. It is understood that an adaptation of the system for airborne use is under consideration by the manufacturers. Other exhibits included "invisible ray" intruder-alarm systems which, as they can be equally well operated out of doors should be of considerable value for perimeter-fence protection
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
