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Creating Emergencies By Practicing Emergencies

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 Airplane Flying 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 will occur.

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 of every piston engine operating manual? And shouldn't every student pilot be taught that kind of information? I believe all 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 the 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 suggestions!

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 inspectors.