Post by Dave Athay on Apr 8, 2012 22:48:53 GMT -5
Of all the aircraft in our fleet, the DC-3 is the slowest, smallest, and simplest mechanically. But the venerable Gooney Bird still offers plenty of challenges, particularly when the ground is involved.
The old saying with the DC-3 is "if you can taxi this airplane, you can probably fly it." Ground handling could be its own separate topic. Today I'd like to focus on landing.
The perfect DC-3 landing looks very different from the perfect landing in the CV-240 or DC-6. Where the nosedraggers should touch down on the main gear first, with a few degrees of positive pitch, the DC-3 should be flown onto the ground smoothly, touching down on the main gear with a pitch attitude at or near ZERO degrees. Three-point landings can be accomplished in many small tailwheel aircraft. However, this is not recommended in the DC-3. In other words, the flare is completely different.
My biggest problem landing the Goon has been bouncing. In a tricycle gear plane, the center of gravity is forward of the main gear. So when you touch down slightly nose up with a slight downward momentum, the center of gravity continues to come down, pivoting the plane around the main wheels, lowering the nose, decreasing angle of attack, and reducing lift to keep the plane on the ground.
In stark contrast, the DC-3's center of gravity is BEHIND the main gear. So when you touch down, there's a tendency for the nose to go up, which INCREASES the angle of attack and actually INCREASES lift momentarily, causing the plane to bounce back up into the air.
So, what's the fix? I don't claim to be able to do this perfectly every time, but I have made some observations I'd like to offer for discussion.
First, a stabilized approach is critical. This is true any time you want to make consistently good landings. You've got to be on speed, on centerline, on glideslope, and making only small corrections to your approach.
Second, airspeed control. 85 knots on final seems to be the magic number.
Third, keep some power on all the way to the deck. Use a little burst (gently!) to break the descent as you start to enter ground effect. Once the descent has stopped and you're flying parallel to the runway about a foot up, slowly start to pull out the power and fly the plane onto the ground as smoothly as possible, keeping pitch constant (at zero) and using the power reduction to manage the descent. This is pretty much the way you land a helicopter.
Fourth, you have to negate the pitch-up tendency caused by touchdown with a pitch-down control pressure. Timing is everything: if you wait until the pitch up occurs, you'll already be airborne again. If you pitch down before you touch down, you'll be diving into the deck, landing hard, and end up bouncing anyway. Once you're down, smoothly pull the throttles back to idle.
Fifth, apply the brakes. If you've got a long runway, this might not be necessary. But if you need to stop quick, you'll have to start braking BEFORE the tailwheel is down. If you haul back on the yoke to get the tailwheel down before you've gotten rid of some speed, you'll just be flying again. Applying brakes while you're balanced on the main gear will result in a significant pitch-down force which you should be ready to counteract with some aft pressure on the yoke. Don't hold on the brakes too long, though, or the tail will just slam into the ground as soon as it stops flying. Once you've slowed down about 20 knots (around 60-65), let up on the brakes (if you're using them) long enough to ease the tailwheel onto the ground. It's important that you fly the tail down, instead of just letting it happen.
Sixth, once the tail is down, maintain full back stick to keep it down. Use the brakes as required. On most of the runways we fly to, you probably won't need the brakes much, if any, if you're landing right. When you've slowed to taxi speed, open the cowl flaps all the way, unlock the tailwheel, and exit the runway. Verify prop levers full forward, landing lights and transponder off, and retract the flaps once you're on the taxiway.
Those are my thoughts about landing the DC-3. I'm to the point where I can do it consistently without bouncing. Sometimes there's a little bit of a "skip," but nothing I'd really call a bounce.
How do you guys do it? What do you have trouble with?
The old saying with the DC-3 is "if you can taxi this airplane, you can probably fly it." Ground handling could be its own separate topic. Today I'd like to focus on landing.
The perfect DC-3 landing looks very different from the perfect landing in the CV-240 or DC-6. Where the nosedraggers should touch down on the main gear first, with a few degrees of positive pitch, the DC-3 should be flown onto the ground smoothly, touching down on the main gear with a pitch attitude at or near ZERO degrees. Three-point landings can be accomplished in many small tailwheel aircraft. However, this is not recommended in the DC-3. In other words, the flare is completely different.
My biggest problem landing the Goon has been bouncing. In a tricycle gear plane, the center of gravity is forward of the main gear. So when you touch down slightly nose up with a slight downward momentum, the center of gravity continues to come down, pivoting the plane around the main wheels, lowering the nose, decreasing angle of attack, and reducing lift to keep the plane on the ground.
In stark contrast, the DC-3's center of gravity is BEHIND the main gear. So when you touch down, there's a tendency for the nose to go up, which INCREASES the angle of attack and actually INCREASES lift momentarily, causing the plane to bounce back up into the air.
So, what's the fix? I don't claim to be able to do this perfectly every time, but I have made some observations I'd like to offer for discussion.
First, a stabilized approach is critical. This is true any time you want to make consistently good landings. You've got to be on speed, on centerline, on glideslope, and making only small corrections to your approach.
Second, airspeed control. 85 knots on final seems to be the magic number.
Third, keep some power on all the way to the deck. Use a little burst (gently!) to break the descent as you start to enter ground effect. Once the descent has stopped and you're flying parallel to the runway about a foot up, slowly start to pull out the power and fly the plane onto the ground as smoothly as possible, keeping pitch constant (at zero) and using the power reduction to manage the descent. This is pretty much the way you land a helicopter.
Fourth, you have to negate the pitch-up tendency caused by touchdown with a pitch-down control pressure. Timing is everything: if you wait until the pitch up occurs, you'll already be airborne again. If you pitch down before you touch down, you'll be diving into the deck, landing hard, and end up bouncing anyway. Once you're down, smoothly pull the throttles back to idle.
Fifth, apply the brakes. If you've got a long runway, this might not be necessary. But if you need to stop quick, you'll have to start braking BEFORE the tailwheel is down. If you haul back on the yoke to get the tailwheel down before you've gotten rid of some speed, you'll just be flying again. Applying brakes while you're balanced on the main gear will result in a significant pitch-down force which you should be ready to counteract with some aft pressure on the yoke. Don't hold on the brakes too long, though, or the tail will just slam into the ground as soon as it stops flying. Once you've slowed down about 20 knots (around 60-65), let up on the brakes (if you're using them) long enough to ease the tailwheel onto the ground. It's important that you fly the tail down, instead of just letting it happen.
Sixth, once the tail is down, maintain full back stick to keep it down. Use the brakes as required. On most of the runways we fly to, you probably won't need the brakes much, if any, if you're landing right. When you've slowed to taxi speed, open the cowl flaps all the way, unlock the tailwheel, and exit the runway. Verify prop levers full forward, landing lights and transponder off, and retract the flaps once you're on the taxiway.
Those are my thoughts about landing the DC-3. I'm to the point where I can do it consistently without bouncing. Sometimes there's a little bit of a "skip," but nothing I'd really call a bounce.
How do you guys do it? What do you have trouble with?