Jump Jet FAQs
Q What
is Jump Jet?
A. Jump Jet is a vertical
take-off, hovering aircraft which uses a combination of 3-axis
solid-state gyro sensors and special aerodynamics to produce
stable yet highly manoeuvrable flight. It is optimised for a
living room environment, where we believe that many hobbyists
would like to be able to fly. So it is lightweight, durable
and it has no whirling rotor blades to take out the knick-knacks
on the mantelpiece. It can fly forwards and steer like an aeroplane,
but its speed is self-governed to a rate suitable for a domestic
space. Of course it can hover about like a helicopter, and can
be landed on the palm of an outstretched hand. It can also be
flown all around the house!
Q
Is Jump Jet suitable for learning to fly?
A.
Definitely yes. Unlike a radio controlled helicopter,
Jump Jet is aerodynamically self-righting, which means that
it tends to bring itself back to a horizontal, stationary hover
if it is tilted or moving. This makes it a lot easier for a
new pilot to get it into the air and begin developing a feel
for it. However, unlike many "super stable" hovering
novelty products, Jump Jet has a full set of effective flight
controls, so it can be flown with similar precision to a true
RC helicopter. Additionally, it is very safe to operate, with
no large whirling rotor blades.
Q
Does Jump Jet have proportional controls?
A. Yes. It has four, fully
proportional channels of control.
Q
Are spares available?
A. Four spare props are
included with every Jump Jet. We stock propellers and other
spares, the range of which will increase as further parts become
available.
Q: Can several batteries
be used so that the Jump Jet can be flown more than once without
re-charging?
A: We offer spare batteries
as replacements for worn-out units. Use of multiple batteries
is not recommended because the Jump Jet's battery socket is
not designed for frequent re-connection. Additionally, back-to-back
flights will cause excessive wear of the motors, because they
will not have the usual time in which to cool down.
Q.
How is the High Performance (25C) Battery better?
A. This battery is a "go
faster" replacement for the standard Jump Jet battery pack,
and brings improved performance through a new chemistry. The
Jump Jet maintains peak climb-out power through most of the
discharge, rather than losing performance steadily as the flight
proceeds.
The Alien Flying Saucer flight has similar characteristics
when using a 25C battery.
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Q
What is the benefit of infrared control?
A. Infrared control has
one huge advantage over radio-based communication: It works
by line-of-sight, so it cannot suffer interference originating
from outside the immediate environment. Jump Jet is intended
to be operated indoors in a confined space, amongst people of
all ages. It is therefore crucial that it doesn’t pick up interference
from another nearby transmitter, potentially causing erratic
or violent movements. Infrared control is immune to interference
coming from outside the room it is operating in.
Q
Can the Jump Jet be trimmed?
A. The Jump Jet has no
trims on the handset. That’s because the electrical values of
both the TX signal and the on-board gyros are automatically
zeroed at the aircraft each time the TX is switched on. If the
handset had trims and these were offset from centre, the aircraft
would re-zero to these trim positions at the next power-up,
negating their effect.
However, the automatic trim is not always 100% perfect because
it cannot correct for small differences in performance between
the motors and propellers, or a centre-of-gravity imbalance.
The best way to correct these errors is by adding one or two
small blobs of Blu Tack to the extremities of the aircraft as
necessary to bring it into balance.
Q
Can Jump Jet be enhanced in any way?
A. Performance can be "souped-up"
considerably compared with the stock product, by removing unnecessary
weight. In order to qualify for mass-marketing, Jump Jet includes
a number of parts whose purpose is to make the aircraft pass
various stringent safety tests, which go way beyond the requirements
of hobby aircraft. A typical model helicopter is after all,
a self-assembled, flying power scythe, with hot parts, noxious
fumes etc. It is up to the operator to use it safely.
If you are such a responsible hobbyist then there is no reason
not to pare down your Jump Jet to obtain the best possible performance…the
performance it was always meant to have! But do treat it with
respect.
1) The foam wings and tail have transparent tape applied
in various places, top and bottom. This weighs a total of
3g, or 5% of the total aircraft weight! Removing it isn’t
always easy but it can usually be done; alternatively, a replacement
foam set can be purchased, which will come without the tape.
2) The guard rings around the propellers weigh a gram each.
These do offer some real protection, but on the other hand
the propellers are quite well guarded by the surrounding body.
The rings easily unclip from the motors.
These two measures will save a total of 7g – more than 10%
of the aircraft’s weight! Climb-out speed will be greatly increased,
and up to a minute may be added to the flight time. One note
of caution: At its stock weight, the aircraft is designed to
have insufficient lift to fly when nearing the end of the battery’s
discharge, so that it is safely landed before the power cut-off
point is reached. With reduced weight there is a good chance
that it will still be airborne when the power quits, so be careful!
Experienced pilots might like to consider flying with the foam
body removed altogether. The four-rotor "flight engine"
is perfectly flyable by itself, and is very fast and manoeuvrable.
It will no longer be self-righting however, so take care! RC
helicopter pilots should have no trouble flying it. It would
be a good idea to re-fit the propeller guard rings, and to add
a conspicuous marker to indicate the aircraft’s orientation.
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Q
Why do all the propellers turn in the same direction, instead
of in counter-rotating pairs?
A. Jump Jet belongs to
a class of aircraft known as "quadrotors", and traditionally
these have used four horizontal propellers with diagonal pairs
turning in opposite directions. On such a machine there is no
net torque reaction, and yaw forces have to be generated entirely
by differential torques from changing the propeller speeds.
Jump Jet has small, direct drive propellers which do not generate
much torque reaction, and the aircraft has the outboard foam
body which has a large moment of yaw drag. As a result, differential
torques alone are not enough to provide adequate yaw authority.
To boost this, we could have tilted the counter rotating
pairs of propellers equally in opposite directions, making a
small portion of their thrust available for yaw control. However,
having once decided to tilt the propellers, it was a small
additional step to tilt the pairs by different amounts so that
all the propellers could turn the same way. The resulting net
torque reaction is compensated by the differential tilts.
The benefit of this is simplicity....only one propeller
to make and no worries about which is which.
Q
What is the control range?
A. Infrared range varies
depending upon the environment. Although IR works in straight
lines (rather like a torch beam), it provides good omni-directional
coverage of a room because it reflects and re-reflects from
the walls and ceiling, filling the available space with energy
travelling in all directions. A torch beam can illuminate a
whole room in the same way.
However this only works well if the room is not too large,
and the ceiling is not too high. Generally a domestic room with
8 – 10 foot white ceilings is ideal, when range will be 20 –
25 feet. This allows full freedom within the great majority
of home spaces.
Range will be reduced outdoors or within a large indoor space
such as a sports hall. Also, some types of lighting can disrupt
IR reception and reduce range, especially high powered discharge
lamps and some types of fluorescent tube. Domestic lighting
usually causes no problems, unless the Jump Jet is flown very
close to the lamps.
Q
How can the IR control strength be maximized?
A. The Jump Jet’s infrared
control is very robust in most domestic environments. However
in larger rooms and at longer ranges, it is necessary to keep
in mind the transmission medium being used. The following tips
can make a real difference:
1) It may seem obvious, but when flying, point the controller
at the plane! Many pilots tend to point it downwards, so that
the infrared energy has to reflect off the floor before it
has a chance of reaching the receiver. This is even worse
if there is furniture between pilot and aircraft.
2) Don’t fly the aircraft close to lights. Unfortunately,
many compact fluorescent lamps operate at a similar frequency
to infrared, and can disrupt reception if too close.
3) Avoid direct sunlight, which will reduce range dramatically
if it hits the aircraft.
4) Jump Jet will not tolerate other infrared devices operating
in the same room.
5) Use fresh, alkaline batteries in the handset.
Q What is the difference
between Mode-1 and Mode-2 control?
A. In Mode-1 the left-hand
stick controls elevator and rudder. The right-hand stick controls
throttle and aileron. In Mode-2 the left stick controls throttle
and rudder and the right stick elevator and aileron.
(Snelflight sells many more Mode-2 sets than Mode-1.)
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Q: Is a 2.4GHz upgrade planned?
A. No.
This is for two reasons:
- Existing hobby 2.4GHz systems use proprietary
signalling formats. These may or may not be legally protected
and additionally, they are incompatible with one another.
Therefore it would not be possible to make an upgrade module
to work with more than one brand of radio. One major advantage
of conventional FM is that the signalling is reasonably standardized
across the industry.
- One of the most exciting things to do with
a radio controlled Jump Jet is to mount a wireless video camera
on it (Pictures & Video). Most
cameras tend to transmit on 2.4GHz, and interfere with other
communications in this band. During operation the camera transmitter
is located very close to the flight receiver, making interference
almost impossible to avoid unless the two transmissions differ
greatly in frequency. Combining the camera with conventional
FM provides an ideal solution.
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