Technology Database  Details, units and mechanisms FOLDING PROPELLER
Folding
Propeller
 In its design, operation and
control characteristics, the folding propeller differs fundamentally from known
helicopter propellers because blades of the propeller may be extended prior to
takeoff or during flight of an aircraft, transforming it into a helicopter
propeller (enabling the aircraft to perform vertical landing or takeoff as an
ordinary helicopter) or be fully retracted (transforming it into a compact
assembly which may be easily and readily put into the fuselage or covered with
cowlings), enabling the aircraft to transform itself into an ordinary airplane
and fly at any required speed.
À design for à folding
controllable propeller (FCP) with elastic blades has been developed and a
prototype produced.
All rotors known to date have
rigid blades, and their extension (opening) or retraction during flight is a
serious technical problem which had not previously been resolved. The design
features of the elastic blades allow for folding them (to wrap them on drums)
and unfolding them with the propeller rotating. The blade fold/unfold mechanism
is compact, has a relatively small mass and allows for reducing the propeller
diameter to 5% - 6% of the maximum one. GFSP = 5 –7% G max takeoff
weight of an aircraft.
 FCP designs developed ensure
their stable operation and controllability in all flight modes, including
extension and retraction modes.
FCP is able to change aerodynamic
rotation of blades in a wide range of cases, allowing the aircraft (helicopter)
substantially to increase the payload in vertical takeoff and to increase the
horizontal flight speed.
A FCP scale model has been tested
in wind tunnels both in vertical and in oblique flows, including in the
autorotation mode. The tests confirmed the validity of theoretical calculations.
 The following preliminary designs have been
developed on the basis of FCP:
- Transport aircraft capable of taking loft from
and landing on unprepared sites.
-
Rescue aircraft performing
rescue operations in the mode of hovering over land or sea and VTOL capable
on water or land surfaces.
-
Heavy helicopters capable of
carrying a payload weighing several hundred tons and performing assembly
work.
-
Autorotating system for
descending cargoes from high-speed aircraft with remote control or automatic
precision and soft landing in a given area.
-
FCP application on pilots'
ejection seats and aircraft cabins, allowing a more controlled descent.
-
FCP application on unmanned
remote controlled aircraft for prolonged flights at high altitudes to
perform meteorological or environmental observations.
Source: SciTecLibrary.ru
Publishing date: September 27, 2000
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