THE NEW PIPER AIRCRAFT, INC.
PA-32-301FT / 301XTC
MAINTENANCE MANUAL
PAGE 5
Jun 1/03
5G5
81-20-00
Bootstrapping This is a term used in conjunction with turbo machinery. If you were to take all
the air coming from a turbocharger compressor and duct it directly back into the
turbine of that turbocharger, it would be called a bootstrap system and if no
losses were encountered, it would theoretically run continuously. It would also be
very unstable because if for some reason the turbo speed would change, the
compressor would pump more air to drive the turbine faster, etc. A turbocharged
engine above critical altitude (wastegate closed) is similar to the example
mentioned above, except now there is an engine placed between the
compressor discharge and turbine inlet. Slight system changes cause the
exhaust gas to change slightly, which causes the turbine speed to change
slightly, which causes the compressor air to the engine to change slightly, which
in turn again affects the exhaust gas, etc.
Critical Altitude A turbocharged engine’s wastegate will be in a partially open position at sea
level. As the aircraft is flown to high altitude (lower ambient pressures) the
wastegate closes gradually to maintain the preselected manifold pressure. At the
point where the wastegate reaches its full closed position, the preselected
manifold pressure will start to drop and this is considered critical altitude.
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