Even though
the term dates back to the Cold War era 1960s American aeronautical engineering
boom, does anyone still use the term “pervertiplane” these days?
By: Ringo
Bones
Any group
of specialists has its own private lexicon and aeronautical engineers are
surely no exception. The word “pervertiplane” could be defined as a corruption
of the term “convertiplane” – which is a contraction of the term “convertible
aircraft” – pertaining to aircraft constructed in such a way that their lifting
and propulsion systems may be converted to permit efficient operation either
for vertical take-off and hovering or for high-speed forward flight. Such craft
are now more commonly termed as VTOL or vertical take-off and landing aircraft.
Convertiplanes
– at least their experimental prototypes – began life back in the beginning of
the 1960s. Examples of which are the X-19 broad-bladed tilting rotor turboprop
VTOL plane, the X-22 tilting ducted fan VTOL plane, which is probably the great-granddaddy
of the V-22 Osprey that got fielded back
in 2007 and some jet-engine high-performance experimental VTOL fighter planes
like the British-built Hawker P1127 cascade vane-nozzle turbojet VTOL that
later became the USMC’s Hawker Siddeley Harrier / Harrier Jump Jet and the then
West German EWR VJ-101C tilting engine turbojet VTOL interceptor.
Convertible
aircraft are sometimes called “convertiplanes”; however, one prominent
aeronautical engineer – legend has it that it was Igor Sikorsky – has suggested
the name “pervertiplanes” because so many of the machines, in his view, combine
the worst features of the helicopter and the fixed-wing aircraft. The necessary
provision of such structurally difficult features as tilting wings, tilting
rotors, cascade-vane assemblies and the like which may be subjected to high gas
temperatures and periodically fluctuating air loads, all at minimum structural
weight, leads to the development of very complicated mechanical devices that in
turn leads to a high probability of mechanical failure.
By far, the
most serious problem with convertible aircraft lies in its characteristics
following engine failure at low altitude. Unlike fixed-wing aircraft, which can
fly as a glider following engine failure or the helicopter, which can descend
at a safe – but rapid – rate with its rotor being spun by the flow of air past
it (a process called autorotation), the convertible aircraft commonly lacks
wings large enough to descend slowly as a glider, or a rotor large enough to
permit a safe autorotation descent. Worse yet, if power failure occurs during
transition, it may not be possible to achieve either type of descent and the
vehicle will fall like a rock. Looks like a convertible aircraft or
convertiplane’s reputation as a “pervertiplane” seems apt.
