User Guide

EMERGENCY DESCENT
As we’ll cover when we look at the engine, a rapid major
power reduction is hard on the engine--but when you need to get
down, fast, to avoid losing consciousness, it’s no time to scruple.
It’s highly unlikely that the Mirage will be cruising at an indicated
airspeed higher than 165 knots--so pull the power to idle, drop
the gear, and stuff the nose down until you approach 195 knots.
The airplane will come down like a rock; once you’ve gotten the
descent going, you need to fiddle a bit with the fuel mixture to
keep the engine running smoothly. When you get to a “breath-
able” altitude, level off, retract the gear, and set an appropriate
cruise power.
THE POWERPLANT
Perhaps the most significant difference between the Mirage
and the 172, and certainly the most significant in terms of how
you’ll operate and fly it, is its magnificent turbocharged, inter-
cooled engine and its constant-speed propeller. We’ll address
them first separately, then together:
THE ENGINE
Like the 172, the Mirage has an Avco-Lycoming engine, and
there’s a family resemblance among all the “Lycs.” The 172’s 160-
hp four-cylinder engine is an IO-360, meaning that it’s fuel-
Injected, its cylinders are horizontally Opposed, and it has a dis-
placement of 360 cubic inches. Using the same notation, the
Mirage’s 350-hp six-cylinder TSIO-540 is TurboSupercharged,
fuel-Injected, horizontally-Opposed, and has a displacement of
540 cubic inches. Notice the relationship in displacement? Just
about every cylinder Lycoming has ever built since the fall of
Carthage has had a displacement of 90 cubic inches. While there
are differences in detail design, the Lyc boys basically put togeth-
er engines by adding more and more 90-cu.-in. cylinders, all the
way up to a monster eight-cylinder IO-720.
In this era, when products from computers to hair dryers
have “turbo” modes, it’s worthwhile to take a moment to describe
a real “turbo.” It’s short for “turbosupercharger;” the Mirage
engine has two of them, one for each bank of three cylinders (pri-
marily because two little ones fit better into the cowling than one
big one).
For a normal flight, set the cabin altitude at 500 to 1000 feet
above your takeoff altitude before departure. Once you have
things squared away for your climb, set the controller to 500 to
1000 feet above your landing altitude, or to your cruise altitude
plus 1000 feet on the inner ring of numbers, whichever is higher.
If you’ve had to use this latter technique, reset the controller to
500 to 1000 feet above your landing altitude as you start your
descent.
Just below the controller is a triple indicator showing cabin
altitude, cabin rate of climb or descent, and differential pressure -
the difference, in pounds per square inch, between the air inside
and outside the cabin. A glance at this will reveal how carefully
the structure of a pressurized airplane must be designed. For
example, assuming that each cabin window has an area around
one square foot, at the maximum normal differential pressure of
4.5 psi, it has to withstand a force of some 650 pounds. Each half
of the windshield has to withstand close to a ton!
PRESSURIZATION SYSTEM FAILURES
There are only two ways the pressurization system can fail:
“not enough” or “too much.”
In the first case, you’ll notice a higher cabin altitude than
what you’ve selected; if the cabin gets much above 10,000 feet,
the CABIN ALT annunciator will illuminate. Check that the con-
troller is set properly, the pressurized air dump valve control is
pushed all the way in, and the PRESSURIZE/DEPRESSURIZE
switch is in the PRESSURIZE position; if that doesn’t cure the
problem, you have no choice but to descend, donning your oxy-
gen mask if the situation warrants.
The “too much” situation is somewhat more insidious, since
there’s no warning light--and how many of us spend a lot of time
looking at cabin pressure in cruise? It’s also highly unlikely, since
even if the pressurization system loses control over the outflow
valves due to some malfunction, the valves themselves will pas-
sively vent overpressure at 5.6 psi. Still, a significant overpressure
could pose a real hazard, since it could cause structural failure of
the fuselage.
The cure is easy: pull the pressurized air control to its RAM
position, flip the pressurization switch to DEPRESS--and hang on
to your ears! At this point, the airplane will depressurize very rap-
idly–as before, descend, donning your mask if necessary.
Flight Instruction
Flight Instruction
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