MULTI ENGINE RATING
To add a multi engine rating to a private, commercial, ATP, or CFI certificate, the FAA requires an instructor endorsement and a practical test. A Knowledge test (written) is not required. The practical test includes a detailed oral test.
Pilots may take their original private pilot or other practical tests in a multi-engine airplane, in which case they will be subject to additional experience requirements. A pilot certificate obtained in such a manner will not include single engine piloting privileges (ability to deal with a total power loss is not demonstrated during multi engine certification).
If you are in the San Francisco Bay area and would like initial or recurrent multi engine training, please contact the author of this article, Anton Sabev.
Are multi-engine airplanes really safer?
Why require an additional rating to fly multi-engine airplanes?
If these questions intrigue you, read on ...
Muti Engine Safety Math
Per flying hour a Twin Engine Airplane compared to a Single is:
Surprisingly safety doesn't improve significantly with 3 or 4 engines. A dual failure in the 3 engine types usually creates an unacceptable loss of performance. In the 4 engine types a dual failure on the same side creates a directional control dilemma.
The Pilot Makes All The Difference
Two engines are better than one, but ...
Incompletely trained or rusty pilots can fly multi engine airplanes, but not safely. In normal operations they would be at least twice safer flying a single engine airplane. This is due to the higher probability of any of the engines failing in a multi and the consequences of not being prepared to handle those cases.
Long over water flights are safer in multi-engine airplanes, but only with proper preflight planning. The pilot needs to make computations which prove that, in case of an engine failure, enough range is available to reach the destination, the departure, or the alternate airport. The computations should assume the worst possible moment for engine failure - the equal time point - and take into consideration existing winds and temperatures.
Multi engine airplanes have a significant safety advantage over singles in mountain over flights. Again, this only holds true if care is taken to ensure that a takeoff and flight at safe altitudes above peak levels is possible after an engine failure.
Given the above no wonder there is a popular saying "If an engine fails in a twin the remaining engine will only carry you to the scene of the accident." Obviously this is not true for airline operations as well as for private pilots who take the time and effort to stay proficient in engine out operations.
So One of My Engines Failed
Engine out operations frustrate flight in two basic ways.
Performance - Will She Climb?
Performance degradation affects our climb rate, service ceiling, range and airspeed. In a twin we lose much more than 50% from any of these when we lose 50% of our thrust power. Why? Climb depends on excess power. A significant amount of power is used just to overcome drag in level flight. Therefore if we lose half of our power we lose much more than half of our climbing ability, which in turn lowers our service ceiling. Multi engine pilots are taught to combat performance problems by maintaining proper flight speed and bank, minimizing drag, and by preflight verification that performance will be adequate after an engine loss.
Directional Control - Will She Fly?
Directional control problems after an engine failure are insignificant at normal flight speeds, but become severe as speed decreases. There is a speed (Vmc), usually higher than stall speed, below which control is impossible to maintain. Pilots can regain directional control by increasing airspeed, banking into the working engine(s) (the more the better), feathering the dead engine. If altitude is not an issue - when we're very high or still on the ground - we can cure all directional problems by simply closing all the throttles we have.
Takeoff Decisions - Fast or Fatal
Both control and performance are even more critical during takeoff. In a takeoff engine failure situation a quick decision needs to be made whether to abort or continue the takeoff. This decision entirely depends on the airspeed achieved, the runway length, and surrounding terrain. In typical propeller twins and runway length combinations most of the accident causing errors are MISJUDGED CONTINUED TAKEOFFS. On the other hand the typical Turbojet-runway length combinations more often result in MISJUDGED ABORTED TAKEOFFS.
When learning multi engine flying two additional training factors are:
The last two present no difficulties to pilots experienced with high performance single engine airplanes. On the other hand newly certified private pilots are likely to require more training addressing the above areas.
Centerline Thrust - Is It Better?
Pilots of centerline twins will be similarly affected by performance loss as any other twin after an engine failure. There won't be directional control complications. This is a great blessing, but it has some negative consequences. It is now harder to detect an engine failure on takeoff, and much harder to figure out which engine failed. Each airplane has different engine failure indications which make recurrent training very important. It is just as imperative to maintain blue line (Vyse) speed after a failure as in any other multi engine airplane.