nothing so far from a "Nurflügel", the INAV 1 arose from the necessity
of the INAV of a versatile and simple wooden built glider, with good performances
that could be built by clubs. Was Dr. Horten who lectured on the new design
in the "Tercer Congreso Argentino de Vuelo Sin Motor" ("Third Argentinean
Congress of Flight Without Engine") in 1953. The salient aspects of it
were published in the magazine "Vuelo Silencioso" of June of 1953 and the
comments of the construction of the first
prototype and results of the first test flight in the magazine "Vuelo
Silencioso" of May of 1954:
It is foreseen to develop new types of gliders in
the Design and Building Division of the INAV. Although the facilities in
La Cruz still are not in operation, yet this is not an impediment to begin
with test gliders, as it has been established by the Statutes of the INAV.
The Directive Commission in November of 1952 told me to begin the work
with a single seater glider, whose specifications have been given by the
General Director of Flight Without Engine, Mister Ernesto Vignera.
According to him, the employment of the INAV 1 is:
A training single seat glider, of a high resistance structure,
with a factor of acceleration from 8 up to 10, semiaerobatic, capable for
flight in clouds.
A glider for the "B" pilots' instruction and training
until the P.N.
These two employments are generally incompatible and
each one requires a different model. To avoid this it has been proposed
as a solution the placement of flaps that bring with them the corresponding
changes of flight characteristics. I would not want to promise for
the time being if they will produce the wanted flight qualities.
As third mission I have found out the desire of the FAVAV,
of having a sailing ship of the class of the "Meise", but simple and robust
in its construction, to be able to be made by the clubs in the least time
The Directive Commission, in their meeting of May
1953, has also given its authorization to accomplish this mission, and
I have proposed to develop a new design based on the training sailing ship,
but with a wing of bigger span. This design is constituted by the
fuselage, the tail group, wing takings and half of the ribs of the training
sailing ship .
The existence of three different necessities demonstrate
that the urgency of developing own gliders is big for the Argentinean sailing.
We should not increase the great number of existent gliders in the world
with one more, we instead should have to take into account for the project
the necessities that arise from the circumstances in the Argentina Republic.
with regards to the flight performances, later meteorological measurements
will give the basis for a design with optimal values. For the "INAV 1"
(training sailing ship) the minimum performances have been established
by the General Director of Flight without Engine, and those of the high
performances sailing ship are that of the maximum allowed increase of the
About the design it has been required that the sailing
ship can be built for the clubs in "kit" form, it is, is not wanted a light
construction, and that the wing of two parts be built in wood and be connected
to the fuselage in such a way that with taking out a bolt the two wing
tips reach the ground. This is very convenient for rig - out the machines
after landing in distance flights. There have also been prescribed spoilers
and a rigid command of ailerons, with push tubes . The fuselage was required
with: the front of steel tube, good dampening in the landing skate and
single - wheel, with adjustable treadle, open and closed booth, all the
commands with ball bearings and a compensation tab in the stabilizer. All
these desires were accomplished and also other more, as the hook trigger
of the of gravity center, to facilitate the tow by automobile or
winch and the tow with an airplane with single hook. In the first prototype
I desisted of the static balance for compensation of pilots' different
weights, since the sailing ship possesses a profile of the series NACA
23 that practically doesn't have variation of the center of pressure and
due to this, the glider has a great excess of stability. If the test flights
agree with what I think, we can desist of this compensation and the tab
in the stabilizer will be sufficient for all the weights of the pilots
to fly with stability in all the speeds without pressure in the neutral
position of the stick.
As you can see from the drawings, I chose the shoulder
gives good visibility upwards and backwards, which is necessary in the
turns in thermal. Forward, below and sidewards, the glider have enough
visibility, while ahead and below it doesn't exist. With the cover interchangeable
open booth demanded by the General Director of Flight without engine, the
visibility to the winch or automobile can be good during the tow.
The height of the wing tips on the ground was reached
with a dihedral of 5,7°, this gives, in combination with the dampening
of the slip due to the lateral surface of the fuselage, simple flight
qualities in what refers to the movements around the longitudinal axis.
For pilots with little training and blind flights this quality is a great
advantage. Also the small surface of the stabilizer gives little sensibility
around the traverse axis, facilitating this way the blind flight.
With regards to the vertical axis I made everything
to obtain a maximum of
maneuverability, being this pleasant to the pilot.
For this reason the ailerons have been developed with the border
of attack of Frise type and the rudder has been dimensioned to the maximum
possible size. In spite of all these, it is necessary to wait to know what
flight qualities will result in tests and if these will have be modified
according to those planned.
I want to remark that no apparatus is finished when
carrying out its first flight and that the test and the improvement of
flying qualities constitute an important part in the development of new
The single - spar wing, of two parts, is connected
to the fuselage like a cantilever shoulder wing with three bolts.
In the leading edge, made with compensated veneer,
are located push tubes with ball bearings,
and near the end of the wing, a rope attached to the main spar is used
to rig - out the glider to the ground. The aileron, aerodynamically compensated
, pivot on the main spar, likewise the spoilers in mid - span of the wing.
These last ones are insured against automatic opening and are operated
by ropes, the auxiliary spar that is connected to the fuselage with a fastener,
resists in the event of an accident accelerations up to 15 g. in forward
direction, and with bigger accelerations breaks as a fuse while the tubes
of steel of the booth support bigger accelerations. The front part
of the fuselage was designed in such a way that it supports 20 times the
glider and pilot's weight.
The direction of attack of the stress is calculated
with an angle of 30° up and with 5 g. sidewards, in such a way that,
if the security belts don't break, the pilot will be completely protected.
If a more serious accident happens, the tubes in the vicinities of the
pilot's seat will support 30 g., while the tubes of the front part will
open to the outside. With all this, I believe, we have made everything
in the tubes' structure to increase the pilot's security, although it results
in a weight increase from about 10 to 12 kg. in comparison with a normal
The covering of the fuselage can be made with a fine
aluminum foil or with cloth, or if we can produce it, shatter - proof plastic
material. On the instruments and the termination
of the pilot's booth I don't say anything, because this is left to the
The later part of the rounded fuselage, built in wood
with three longitudinal cords and veneered with compensated wooden, with
the keel down, takes a tail group of conventional construction, also
in wood, and the rudders are worked by wires. Behind the center of gravity
is located a wheel with dampeners; at the tail, a skate dampened by a tennis
ball and in the front part of the fuselage a wooden skate, also dampened.
To finish I want to express my hope that in a short
time it will be possible to begin the shop works and that in the next year,
in the Fourth Congress, we wil be able to show the prototypes in flight.
("Vuelo Silencioso", June of 1953)
|Wing loading with a load of 100 kg.
|Maximum glide speed
|Minimum sinking speed
||0.80 m/seg at 68 km/h
||1.04 m/seg at 63 km/h
||0.62 m/seg at 65 km/h
|Best glide ratio