Jabiru Aircraft
Pty Ltd
Installation Manual
Jabiru 3300 Aircraft Engine
REVISION
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Dated : 1
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Dec 2016
Page: 32 of 56
6
Air Intake System
6.1
Intake Air Heating
The Jabiru 3300 engine can experience carburettor icing in some conditions. Jabiru Aircraft strongly
recommend that a system for heating engine intake air be included in the induction system design.
6.2
Intake Hose & Air Filter Box
Jabiru Aircraft recommend that engine intake air be drawn from outside the cowl wherever possible.
Due to the way the carburettor works (as described above) it is sensitive to the air flowing into it.
Turbulence, swirl and sharp edges all affect the mixture metering system of the carburettor.
The hose type recommended for induction systems is SCAT aircraft type.
WARNING
SKEET type, which has an inner liner must NOT be used. Over time the inner lining can detach and
collapse, blocking the hose. SKEET hose should be used for positive pressure applications only.
Tight corners in the hose (as shown in Figure 33) can introduce both swirl and turbulence to the air flowing
into the carburettor
Connecting the hose directly to the carburettor can cause the hose to bunch up and cover the sense ports.
A “Cobra Head” duct or similar is recommended to prevent this.
Sharp corners inside the air filter box cause turbulence and a pressure drop. The pressure drop means that
the carburettor balance tube pressure reading is inaccurate, while the turbulence affects the readings at the
carburettor sense ports. Both items can cause power loss and rough running
– particularly at high power
settings.
For installations where there is very little room between the carburettor and the firewall a special duct has
been developed to minimise pressure drop and turbulence
– shown in Figure 37.
The intake hose should align as closely as possible with the carburettor body
– having the intake duct come
at the carburettor from one side encourages swirl and can give uneven mixture.
Figure 33. Air Intake Connections
Smooth entry into hose
– no
turbulence or pressure difference
Balance tube
“Cobra Head” duct
fitted to carburettor
Rough entry into hose
– high
turbulence and pressure difference
Balance tube
Hose bunched, covering
sense ports & adding
turbulence & swirl
Air filter box
Air filter box
