Creating Emergencies By
by Tom Jones
Article reprinted with
permission of FAA Aviation News
When was the last time you practiced
emergency descents? Was it when you were training for a pilot
certificate, recurrent training, or just for fun? The Practical Test
Standards (PTS) for pilot certification normally requires a
demonstration of an emergency descent. One of the requirements stated
in the tasks is proper planning.
Where does that
planning start, and where does it stop? Most pilots are concerned with
following the procedures, such as reducing power, extending landing
gear, flaps, spoilers, etc., and getting lower as fast as possible. Of
course, it requires planning to know what speeds to use and what
procedures are required and/or suggested by the manufacturer. How
often do we consider what the engine manufacturer requires? From the
reports we receive from FAA authorized maintenance technicians, not a
lot of consideration is given to the engine requirements. Considering
engine performance and operation is a part of that planning.
All pilots are familiar, or at least should
be, with the
Handbook (FAA-H-8083-3), formerly the
Flight Training Handbook
fAC-61 -21A). The book is well written, and contains up-to-date
information and graphics. On page 12-2 there is a discussion of
emergency descents. In particular, it states that the emergency
descent should be made at the maximum airspeed consistent with the
procedure used. A little further along, it unobtrusively states: "In
airplanes with piston engines, prolonged practice of emergency
descents should be avoided to prevent excessive cooling of the engine
cylinders." Could excessive speed and prolonged descents be adding to
your maintenance expense?
If we are supposed to avoid prolonged
descents at a low power setting, how do we learn how to save our
engines in the practice or training environment? Do the engine
manufacturers have information that we pilots need? For one thing,
they know that if an engine is cooled too rapidly, often called
"shock-cooling," engine problems will occur. Notice I said
will occur. Not maybe or
might or may. Damage
Some pilots may not fully understand what I
mean by shock cooling. It is something like when you are working on a
hot day and decide to eat an ice cream cone or drink a frozen
beverage. You're hot, and you decide to gulp down the beverage or eat
the ice cream really fast before it and you melt. If you've ever done
that, you know that you get a really sharp headache instantly.
Something like that happens to your engine. Except the pain doesn't go
away, it causes cracks in the cylinders, the exhaust system, or both.
The major problem is that the engine does not cool down uniformly. You
have hot engine parts and cold engine parts. As we all know from basic
physics, heat expands and cold retracts. So you have a cylinder that
cools down rapidly because of low combustion going on inside and
increased airflow through the cooling fins. You have an engine case
that is still hot, because no one told the main case to cool down
quickly enough to match the cylinders. Then, you have cool cylinders,
a hot engine, retracted cylinders, and an expanded engine case'that
means something has to give. The cylinder is the most likely place or
in some cases the exhaust system as well as the cylinders. Actually
the main thing that gives is your bank account.
So, where do we find the recommendations
made by the manufacturers? One good place is your maintenance
technician, ask him/her for guidance on proper procedures for engine
operation and maintenance concerns or contact the manufacturer. One
engine manufacturer, Textron/Lycoming, publishes guidance called
"Service Instructions." For example, their Service Instruction No.
1094D, printed on March 25, 1994, concerns leaning procedures. On page
two it states, "At all times, caution must be taken not to shock cool
the cylinders. The maximum recommended temperature change should not
exceed 50'F per minute." A lot of wisdom in a really out-of-the-way
publication. Shouldn't that kind of guidance and information be a part
every piston engine
operating manual? And shouldn't every student pilot be taught that
kind of information? I believe
pilots should be familiar with this information!
So, how do we pilots use this information?
I suggest that whenever you practice emergency descents you learn just
how much power reduction can be accomplished to reduce the power
sufficiently to descend in accordance with good practices. Remember
the PTS requires the pilot to exhibit knowledge of the elements
related to an emergency descent and to demonstrate proper planning.
Couldn't we consider part of this task to understand exactly how your
engine operates? For example, if you were flying an aircraft such as a
Cessna 421 or a Beechcraft BE-80 (Queen Air) and you were to rapidly
reduce the power to idle and begin a high rate of descent, you better
be prepared to handle a real emergency, because you just created one!
You will have another emergency when you go to have the repairs made.
I suggest that you learn all you can about
your engine, how rapidly it is supposed to be cooled down and how long
can it be operated at a reduced power setting in a high-speed descent.
I do not believe that any pilot examiner will be offended if you
demonstrate that you can effectively make an emergency descent by
following proper procedures. If the examiner has a particular method
whereby he/she requires a rapid reduction of power and a high-speed
descent, maybe you can have some information from the manufacturer and
Airplane Flying Handbook
to show him/her. Then impress the examiner with your ability to fly
the maneuver safely and in compliance with the manufacturer's
Save your engine. You just might want to
use it on a dark and stormy night, over the mountains, or flying out
over water traveling to the Bahamas. Or, you just might want to save
some money on engine maintenance!
Tom Jones is the
Operations Unit Supervisor at the Richmond (VA) FSDO. This article was
written with the assistance of Maintenance Inspectors of the Richmond
FSDO. The suggestion for this article came after repeated reports of
instances where training aircraft engine cylinders cracked
prematurely. Maintenance technicians who work for flight training
establishments often bring this kind of information to our maintenance