Pilot’s Operating Handbook Section 7
EXTRA 500 Description of Airplane and Systems
temperature is measured by a sensor located within the bleed
ducting prior to cabin entry through the front pressure bulkhead.
The temperature controller compares this actual inflow
temperature to the desired inflow temperature and adjusts the
temperature modulating valve to match this desired inflow
temperature.
It is within the nature of this design (bleed air cooling by means
of an air to air heat exchanger) that cabin bleed air may not be
cooled below ambient temperature before entering the cabin.
Therefore a vapor cycle air conditioning system (refer to
paragraph
7.22) provides additional cooling capacity for hot
ambient conditions.
The automatic temperature control limits cabin inflow
temperatures to values below 72 °C. An additional independent
thermal switch installed in the cabin bleed duct activates the red
BLEED OVERTEMP warning light located on the annunciator
panel in case the cabin inflow temperature exceeds 85 °C. In
case, the BLEED OVERTEMP warning light on the annunciator
panel illuminates, indicating a temperature controller failure, the
temperature can be manually controlled by switching the
TEMP CTRL switch, to the MANUAL position (see Figure 7-16).
Selected and held in COOL or WARM position activates the
temperature modulating valve manually (overrides the
controller) causing warm up or cool down of incoming bleed
air.
Important Avoid unnecessary operation of the environmental bleed
control in manual mode to avoid risk of bleed air
overtemperature condition. A sustained bleed air over-
temperature condition may cause structural overheat
including structural damage or even risk of fire.
7.20.c Mass Flow Control
Environmental bleed air to the cabin is mass flow controlled. A
computerized mass flow controller governs the mass flow valve
in the engine compartment. Mass flow control input data comes
from the mass flow sensor installed in the environmental bleed
duct (actual mass flow) and controlled to 4lbs/min.
26. January 2011 7-59
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