When your engine fails in a twin, how do you maintain max performance?
Your first step? Fly with maximum power with your good engine and pitch for VYSE, which is your best rate-of-climb for single engine operations. But the next step is just as important: minimize your drag.
What Kind Of Drag Can You Clean Up?
Obviously, you want to make sure your failed engine is feathered, and you’ll do that with your checklist. But after that, the next step isn’t quite as obvious.
If you’re flying with an engine inoperative and you’re keeping your wings level and slip-skid indicator centered like you do in normal flight, you’re actually slipping through the air, and killing your climb performance.
Unfortunately, there isn’t an instrument in your plane that can tell you that when you’re slipping during single-engine flight. But there is something that can prove it: yarn. And we’ll get to that in a second.
Why Is My Plane Slipping Through The Air?
So why is your plane slipping? First off, if you’re flying with both engines running, and you’re keeping the slip-skid indicator centered and your wings level, you’re in a zero sideslip configuration. Basically, your plane is going straight through the air.
But when you lose an engine and you fly wings-level, “ball” centered, the asymmetrical thrust produced by your single engine makes your plane slip through the air.
This is bad, because you’re creating a whole bunch more drag than what’s necessary. And if you’ve ever flown a light twin single-engine, you know that you need every bit of performance you can get.
Flying Zero Sideslip
So how do you fly zero sideslip in a twin? There’s no perfect way to tell, because there isn’t an instrument in the cockpit that can tell you when you’re not slipping during engine-out flight.
But there is a very good rule-of-thumb. By banking your plane 2-3 degrees into the operating engine, and using your rudder to get a half deflection toward the operating engine, you’ll achieve zero sideslip, and get the most performance you can out of your plane.
What Does It Look Like From The Air?
We mentioned the yarn, and now it’s time to see it in action. First, here’s where the yarn is when both engines are running.
Now, here’s where the yarn is with 1 engine shut down in zero-sideslip. See how it’s in the exact same spot?
Now, let’s take a look at where the yarn is during wings-level, ball centered flight. See how far left it moved? That’s because the airplane is slipping through the air because of asymmetric thrust from the left engine.
Getting The Most Out Of Your Twin
Flying at VYSE and making sure you’re in zero sideslip flight is the key to getting the most performance out of single engine operations.
On our flight, we had an additional 100 FPM of climb performance in zero sideslip vs. wings-level, ball centered flight. And it was the difference in us being able to maintain altitude, versus drifting down.