Almost all of us equate the written word with reality whenever we get into a hangar flying discussion about a regulation or procedure. "Show me where it says that in the federal aviation regulations or the Aeronautical Information Manual" is usually the challenge.
You see it during multiengine training when the instructor introduces the aspiring many-motor pilot to the concept of minimum control speed with the critical engine inoperative (VMC). After all, there's a red radial marking on the airspeed indicator at VMC. The student needs to know what that means and how it was determined. The reference is FAR 23.149.
What is this thing called VMC? For those of you who have a multiengine rating in your future, when one engine fails on a twin the airplane yaws toward the bad engine. At the same time, the airplane begins to roll toward the bad engine. If the pilot takes no action, the airplane will roll inverted - if the ground does not intervene first. A pilot's first instinctive action is to apply full aileron against the roll, deflecting the aileron on the bad-engine side downward and making the situation worse. A fatal mistake. The downward deflected aileron creates more lift - and drag - on the bad-engine side of the airplane, which already has more than enough drag. A pilot's first trained reaction should be to stop the yaw with full rudder and to use the minimum amount of aileron necessary to do the job. Oversimplified, VMC is the lowest speed at which you have enough airflow over the rudder to offset the yaw.
The instructor quite properly explains the conditions under which the manufacturer determined VMC: Takeoff or maximum available power on the engines, the center of gravity in the most unfavorable location, maximum sea level takeoff weight, flaps in the takeoff position, landing gear retracted, propeller of the inoperative engine windmilling, the airplane airborne and out of ground effect, and the wings banked not more than five degrees toward the operating engine. The seed has been planted - in the student's mind a five degree bank toward the good engine is required by regulation.
In reality, Part 23 places a limit of five degrees of bank on the manufacturer to provide a level playing field among competitors - banking more than five degrees into the good engine can lower VMC enough to bring broad smiles to the faces of the manufacturers salespeople. The loss of altitude that can result from greater bank angles would do little for the customer's peace of mind, however. With all manufacturers held to the same standard, no one has an edge.
To put this into historical perspective, back in the late 1960s and early 1970s, when GI Bill flight training was invigorating the general aviation industry, the safety record for multiengine training was bad and getting worse. Instructors and multiengine students were spinning into the ground at an alarming rate. The Flight Test Guide in use at that time (AC61-4C, Multi-Engine Airplane Class or Type Rating) didn't even mention banking toward the good engine, and flight instructors and examiners were requiring students to maintain heading with the ball centered when recovering from a simulated engine failure.
Les Berven, an FAA aerospace engineer and test pilot, detected a disparity between the actual flight characteristics of twin engine aircraft with one engine inoperative and what he saw as erroneous beliefs and hazardous misconceptions in the aviation community. He did an internal staff study in 1976 that stated, among other things, that manufacturers were held to a five degree maximum bank angle into the good engine because larger bank angles would lower VMC. But pilots were led to believe that they would be able to control the airplane in the event of an engine failure if the bank angle was not more than five degrees. His flight tests showed that if the pilot held the wings level and kept the ball in the center, loss of control would occur as much as 24 knots above the published minimum control speed.
At the time Berven was studying the problem, the FAA Academy publication on Flight Training Maneuvers and Related Procedures for Light Multiengine Airplanes was telling examiners that for engine failures on takeoff and for VMC demonstrations, to "use a maximum bank angle of five degrees to maintain directional control" and to perform VMC demonstration at "the highest altitude at which takeoff power can be developed." (Because power output decreases with altitude, this led many instructors to perform the maneuver at altitudes too low to recover from an inadvertent spin.) Berven's staff study would fall on fertile ground at the FAA Academy, where the hazardous training situations were institutionalized.
Alarmed by the accident statistics, in 1975 Beechcraft told its dealers and flight schools to observe a new airspeed for training and demonstrations. VSSE, the safe one-engine inoperative speed for intentional engine cuts. The speed varied by model but it was established at approximately five knots above VMC. The rest of the industry quickly followed Beech's lead.
It took awhile for the results of Berven's study to emerge from FAA Headquarters. In a 1980 article, Aviation Consumer told its readers that during VMC demonstrations the bank angle should be about three degrees into the bad engine and the ball should be well out of the center. A 1981 AOPA Pilot article by TWA Captain Barry Schiff expanded on the subject, and in 1989 Embry-Riddle Professor Melville Byington provided a mathematical analysis in the AOPA Flight Instructor's Safety Report and gave instructors a rallying cry: "Stamp out the Five Degree Forever Syndrome!" Once and for all, the five degree bank angle into the good engine is a restriction placed on the manufacturer and is of no practical importance in multiengine training.
You can be certain that the single-engine climb figures shown in the performance section of the pilot's operating handbook were not achieved with a five-degree bank toward the good engine.
If an instructor wants to have a student duplicate the VMC conditions required for airframe certification as closely as possible, he (or she) can ask for a five degree bank into the good engine. But if the other certification requirements are not met (sea level takeoff power, most adverse CG location, etc), it will not be an instructive demonstration. After all, the factory engineering test pilots aren't foolish enough to do VMC testing at low altitude. They go to a high, safe altitude with less than full sea level power on the good engine and then extrapolate the handbook (and airspeed indicator) number with their computers. Smart instructors shade the odds in their favor by either restricting the amount of power their student is allowed to use or by sticking a steel-clad toe behind the rudder pedal on the good engine side.
The bottom line is this. At the moment of engine failure use full rudder to stop the yaw and crank in as much bank angle as it takes to do the job (with your leg straight and your knee locked it won't take much aileron). If that bank angle is a momentary 10 degrees, do it. If you lose altitude, so be it. It's far better to crash-land under control than to fall 100 feet inverted. With the airplane under control, let the ball out of the cage about three-quarters to one ball-width out of the center on the good engine side and use a bank angle toward the good engine that provides the best rate of climb. That angle will vary with loading, density altitude, and other factors, but will be much less than five degrees.
In 1996, the FAA's approach to engine-out emergencies has done a 180. The practical test standards now tells the applicant to "bank toward the operating engine as required for best performance." Note the lack of a specific bank angle or ball position.
Many pilots are still taking multiengine instruction in Piper Apaches, Cessna 310s, or other twins certificated under CAR 3, and their minimal "owners handbooks" may call for wings level and ball in the center if an engine fails. This is one time that "Go by the book" is the wrong thing to do.
