TACTICAL UAV WITH IN FLIGHT ADJUSTABLE PROPELLER,
COMPUTER PROGRAM WHITE EAGLE 2
KOSTA VELIMIROVIĆ
Military Technical Institute, Belgrade
NEMANJA VELIMIROVIĆ
Faculty of Mechanical Engineering, Belgrade
Abstract: The metod for estimation piston-engine, long range, UAV PEGASUS (with in flight adjustable propeller)
performances is presented in this paper. Total energy model programme (WHITE EAGLE 2) is basis for performance
calculation. Insted of fixed pitch propeller, using in flight adjustable propeller, significantly improves take-off, climb,
range, endurance and lowers noise. Method and its results are ilustrated by numerical example.
Key words: Tactical Unmanned Aerial Vehicles, long range, propeller, piston-engine, performances, fixed pitch
propeller, in flight adjustable propeller.
Memoriam et honor general Milutin Milovanović, Kajmakcalan's hero, the holder of decorations White Eagle with
swords
1. INTRODUCTION
Unmanned Aerial Vehicles (UAVs) are remotely piloted
or self-piloted aircraft that can carry cameras, sensors,
communications equipment or other payloads. They have
been used in a reconnaissance and intelligence-gathering
role, and more challenging roles are envisioned, including
combat missions providing attack capability for high-risk
missions. In this paper, one improvement
flight
performance UAV PEGASUS (Figure 1) is presented.
Reason for the improvement is replacement fixed pitch
propeller with in flight adjustable propeller.
Figure 2: UAV PEGASUS, long range, PARTNER 2011
exposition
The pitch of fixed pitch propeller is set and cannot be
changed. With this type of propeller, the best efficiency is
achieved only at a given combination of airspeed and
number of revolutions. Blade angle, usually measured in
degrees, is the angle between the chord of the blade and
the plane of rotation and is measured at a specific point
along the length of the blade.
Figure 1: UAV PEGASUS
196
Figure 3: Pusher propeller - Pith or Blade Angle (teta)
Figure 5: Fixed - pitch,climb and cruise propellers
The purpose of varying pitch angle is to maintain an
optimal angle of attack (maximum lift to drag ratio) on
the airplane propellers as the aircraft speed varies. This is
the reason in flight adjustable propellers were invented.
An adjustable pitch propeller allows an onboard flight
system to change the pitch of the propeller to give the best
thrust characteristics for any given flight condition. These
propellers allow to adjust the pitch of the propeller during
flight. This allows to achieve many different rating.
2. WHITE EAGLE 2 COMPUTER PROGRAM
Figure 4: Fixed - pitch propellers
White Eagle Computer program is used for the
calculation of basic and special performances tactical,
piston-engine, UAVs long range (Figure 2).
There are two types of fixed-pitch propellers—the climb
propeller and the cruise propeller. Whether the airplane
has a climb or cruise propeller installed depends upon its
intended use:
The program consists of several modules:
1. Мodule for determining the mass UAV,
The climb propeller has a lower pitch, therefore less drag.
Less drag results in higher number of revolutions and
more horsepower capability, which increases performance
during takeoffs and climbs, but decreases performance
during cruising flight.
2. Airport Module - based on current meteorological
conditions determine the data of the airport. This
module requests data: frontal wind speed, slop and
quality of the runway.
3. Atmosphere Module - data calculations are made for
the altitude. It works for all conditions from polar to
tropical.
The cruise propeller has a higher pitch, therefore more
drag. More drag results in lower number of revolutions
and less horsepower capability, which decreases
performance during takeoffs and climbs, but increases
efficiency during cruising flight.
4. Aerodynamics Module - loaded aerodynamic
characteristics of clean, takeoff and landing
configurations. This module also presents data on the
aerodynamic characteristics of the launcher and
missiles under the wing.
− Low Pitch Propeller properties:
o Low speed flight
o Good Acceleration
o Good Climb
o Finer speed control throughout throttle range —
particularly at low throttle settings
5. Engine Module - two-strokes
engine, provides
information on the performance and fuel consumption
in function of the regime, the number of revolutions
and the height of flight.
6. Propeller Module - aerodynamic data, two blade
pusher propeller. Data from this module are used for
the calculation of propeller thrust forces installed.
− High Pitch Propeller properties:
o High speed flight
o Poor Acceleration
o Poor Climb
7. Performance Module - compute the minimum and
maximum speed, climb, ceiling...
8. Turn Module - turnaround data calculation.
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9. Takeoff and Landing Modules - presents all data
related to the take-off or landing. The data refers to the
characteristic length, velocity, time and fuel
consumption.
10. Cruise Module - optimal parameters of cruising and
endurance.
11. Start - compute fuel consumption and other data.
12. Planning module
13. Range Module - the most complex module of the
computer program White Eagle 2. This module calls
all the listed modules and determine the maximum
endurance of the flight profile.
Figure 6: Propeller power coefficient teta = 15°, 17.5°,
20°, 22.5°, 25°
3. NUMERICAL EXAMPLE
Climb capability and other performances UAV
PEGASUS
(propeller
blade
angle
teta
=15°,17.5°,20°,22.5°,25°) are presented in numerical
example.
UAV PEGASUS data:
Engine:
Engine power:
Propeller:
Wing span:
Wing area:
Fuel:
Maximum take-off
weight
two-strokes, boxer, air-cooled,
direct drive, fuel-injection
32 КW, maximum speed 6500
(revolutions per minute)
Two blade, pusher, diameter
0.813 m
6.34 m
4.24 m2
70 kg
Figure 7: Propeller efficiency teta
=15°,17.5°,20°,22.5°,25°
Numerical example - varying propeller blade angle (teta)
and corresponding flight performances. Performances of
UAV PEGASUS (weight=202 kg) are presented in
Figures 8, 9 and 10.
230 kg
The Figures 6 and 7 show some propellers performance.
Pitch
teta=15°
teta=17.5°
teta=20°
teta=22.5°
teta=25°
propeller static
forces
h=0 m
(N)
695
598
491
403
max.speed climb
h=0 m
(m/sec)
max.speed climb
h=3000 m
(m/sec)
min. time climb
h=0-3000m
(sec)
7.84
6.46
5.40
4.60
4.34
3.45
2.83
2.30
512
631
761
907
horizontal speed
max
h=4000 m
(km/h)
214.2
203.5
194.2
Horizontal turn
load max
h=0 m
(-)
3.35
3.07
2.88
2.71
Figure 8: Performances UAV
Pitch
horizontal speed max
h=0 m
(km/h)
teta=15°
teta=17.5°
teta=20°
teta=22.5°
teta=25°
237.8
226.0
217.2
horizontal speed
max
h=3000m
(km/h)
221.5
210.7
201.8
Figure 9: Performances UAV
198
Pitch
Horiz. turn load
max h=3000 m
(-)
teta=15°
teta=17.5°
teta=20°
teta=22.5°
teta=25°
2.28
2.08
1.95
1.83
Take-off ground Specific range, rating Specific endurance,
fuel flow, rating 55 %
80%
run/take off
h=3000 m
h=3000m (km/kg
distance m
(kg fuel/hr)
fuel)
m=230 kg
144/225
16.49
9.15
176/266
24.85
7.37
228/329
29.71
5.95
322/443
31,09
4.49
Figure 10: Performances UAV
meter. Torque from the electric motor is multiplied in a
Important facts:
planetary gear drive which turns the lead screw.
UAV weight is 202 kg, UAV take-off weight is 230 kg.
Propeller teta=15° is very "low load", if rating ≥ 60%
than number of revolutions per minute ≥ 6500
propeller teta=17.5° is "low load", if rating ≥ 80% than
number of revolutions per minute ≥ 6500
Propeller teta=25° is "highly loaded". Engine can`t reach
a maximum speed (6500 revolutions per minute) and
maximum power, rating 100% .
Analysis of results shows the benefits of installing in
flight adjustable propellers instead of fixed - pitch
propellers are: shorter take-off, higher rate of climb and
fuel - efficient cruising.
Figure 12: In flight adjustable propellers
7. TECHNICAL SOLUTION
In-flight pitch adjustment is like shifting the gears of a car
in order to save fuel, engine wear and reduce noise.
7. CONCLUSION
Presented preliminary analysis shows that discussed
UAV can be equipped with in flight adjustable propeller.
Replacement fixed-pitch propeller with in flight
adjustable propeller would be useful. Use in flight
adjustable propeller reduces fuel consumption. It also
reduces the required amount of fuel in tanks. In-flight
pitch adjustment is like shifting the gears of a car in order
to save fuel, reduce engine wear and reduce noise.
Further project development of tactical UAV PEGASUS
should consider it as a aircraft equipped with in flight
adjustable propeller.
References
Figure 11: In flight adjustable propellers
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The ability to change the pitch in flight is as significant
for the airplane pilot as for the driver of a car to shift
gears in the transmission.
This results in substantial savings in fuel, engine wear and
noise. Pilot controls the pitch through the toggle switch.
Pressing the toggle switch one way sends electric current
through the graphite brushes to the slip rings and finally
to the electric motor. Depressing the toggle switch the
other way-reverses the polarity of the current and the
rotation of the electric motor. As long as you hold the
switch in one direction the pitch changes in that direction
and you observe the result on your RPM meter. The pilot
uses a switch and observes the results on the engine RPM
199
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