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Setting the Baseline...the Piper Cub

by Budd Davisson, courtesy of www.airbum.com

This sentence begins a whole new series for Sport Aviation and the Experimental Aircraft Association. You might call it Comparing the Classics. Or Classics Explained. Actually, you can call it anything you want. We call it an educational reference for those thinking about diving into the wide variety of post-war classics. Since over 35,000 airplanes were produced in 1946 alone, we certainly have plenty to chose from.

Not so many years ago, evaluating post war classics would have been unnecessary since every pilot had flown most of them. That's no longer the case. Nearly half of the pilots flying today learned in the last 15-20 years. How many do you suppose learned in a Cub? Or had a Cessna 120 available to rent for $8.50 an hour?

Another sobering fact: Just short of half of the EAA members now active joined since 1985. Nearly 70% joined since 1980. To them the classics fall right in with antique airplanes are just as foreign.

The goal of this series, which will eventually touch on each and every airplane of the period, is to explain those airplanes in commonsense terms. We aren't going to get into "stick force per "G"" or "spiral divergence" or any of the other 3-D tech-talk we've come to associate with well-done pilot evaluations. We want people to understand how these airplanes compare to airplanes they either have already flown, or which are readily available for comparison.


Citabria and C-152 are the Datum Points
Since so many classic aircraft have the little wheel at the back, we selected the Citabria as the base-line airplane for those handling and performance factors having to do with ground handling. The Citabria is the only tailwheel airplane which is readily available at flight schools and even it is sometimes hard to find.

We selected the Cessna 152 as the datum for all other comparisons, once off the ground, unless otherwise noted. The comparisons will be in the vein of "...during roll-out the airplane tends to wander a little more than a Citabria..." or "...the ailerons are a fair amount heavier than a C-152, but the airplane responds to aileron input much more quickly..."

We'll put these comparisons into a chart which rates a number of performance and handling factors against the datum aircraft. They will represent zero and the evaluation aircraft will be rated plus (better, easier or quicker) or negative (worse, slower or harder) on a scale of 1 to 5, plus and negative.

The J-3 Cub
To kick this thing off we thought we'd evaluate what used to be the airplane to which all others were compared, the J-3 Cub.

There are bound to be a lot of folks out there who are saying, "What? Another Piper Cub pirep? That's so basic it's like explaining dirt. Everyone has flown a Cub!"

Only a few years ago would have been a valid statement but go back and look at the earlier statistics. Between the total take-over of the tricycle gear trainer and the exploding prices of Cubs, with very few exceptions, if you want to fly a Cub, these days, you have to buy one. They have become so popular because of three basic facts: They are very nostalgic, they are lots of fun, they are cute as a bug.

Mechanical Description
We're going to ignore the history of the airplane, since everyone knows it and get right down to the nuts and bolts.

The fuselage of the Cub is welded steel tubing with the landing gear being a welded "V" with external bungee springing. The wings are attached right in the middle of the cabin where the fuselage truss comes together in an inverted "V". This means the entire top of the cabin and the windshield framing is made of light-gage, bent steel "U" channels which are often bent and filled with extra screw holes.

As with all aircraft of its type, the fuselage is prone to longeron rust at the tail post from water running to the low point. Remember, these airplanes weren't always hangar queens, so most have had, or need, repairs in that area.

Another area of corrosion concern is the struts. The original struts were unsealed and could rust internally at the bottom end where moisture collects. That problem, combined with the integrity of the strut forks themselves, is why there's an inspection AD on them. That's also why so many people simply buy new, sealed struts from Univair and be done with it.

The wings used what was to become the standard Piper rib construction in that they never went to stamp metal ribs as did Taylorcraft or Luscombe. Piper ribs are fragile trusses of "T" sections formed by folding extremely thin aluminium into the required "T" cross section. They are strong, but there are a lot of pieces involved and, once broken, require patience to patch in a clean manner.

Wing spars come in two varieties, wood and extruded aluminium. Wood spars are seen in every variation from a single plank, to laminated, to laminated with the individual laminates made up of different length pieces scarfed together. Properly varnished and cared for, all variations are fine, but need inspection before buying. Beware grey, flaking varnish or dark wood. This is an indication moisture may have found its way in.

The post-war aluminium spars are modified "H" sections and need only be inspected for corrosion on the top side of the lower caps which can trap moisture. Also inspect for extraneous screw holes.

The original leading edges were .016, soft aluminium and won't take much abuse before assuming the visual character of a ploughed field. When restoring them, most opt for slightly heavier, harder material which makes a tremendous difference.

Tires and brakes are both strong and weak points for the Cub. The original expander-tube brakes use an inflatable doughnut to force a multitude of small blocks against the drums. As brakes go, they stink. That's also their strongest point because the airplane needs almost no brake for normal operations and the original brakes can't overpower it. The brakes biggest problem is that they are very expensive to rebuild. The tubes and blocks have sky rocketed. So have the original 8.00 x 4, smooth tires. This is one reason so many have gone to Cleveland wheels and brakes and 6:00 x 6 tires. That amount of brake, however, is far more than the airplane actually needs. With expander tube brakes it's hard to brake it hard enough to pick up the tail. With Clevelands it will go over on it's back in a heart beat.

The usual engine is the Continental A-65, which is probably the most important thing to happen to light aviation. This engine made little airplanes practical. If even remotely maintained it will start and run beautifully. Magneto coils are just about the only reason the engines won't start easily. TBO is a little vague, assumed at about 1,200-1,400 hours, but think how long it takes to put 1,000 hours on an airplane like a Cub.

The engines are still relatively inexpensive to overhaul mainly because we haven't yet reached the bottom of the barrel which was originally filled to overflowing by the military. The bottom of the barrel, however, is beginning to peek through.

The most common conversion to the airplanes is the simple replacement of the A-65 by a C-85. The additional horsepower makes the airplane into an entirely different animal. It still has its basic pasture goodness but with very spirited performance. Unfortunately, the 85's and C-90s are getting increasingly harder to overhaul. In fact, there is an STC to put the more common 0-200 crank into the C-90 case.

From a performance point of view, a metal propeller is preferably because it lets the engine reach peak RPM, but the wooden prop is much prettier. Neither is cheap.

Flight Characteristics.
To fly the airplane, you have to get in it, which in a Cub, isn't as easy as it sounds. You have to master the entry-dance. Right foot in the step, lean forward over the front seat, left foot past the stick, bring right foot in, lower yourself backwards. There that wasn't so hard, was it? The canvas sling back seat is much more comfortable than the front seat. Over-average height folks will be folded like a pocket knife in the front seat.

If it's your first time in a Cub, you'll think you're sitting at an impossibly steep tail down angle. And you are. Few Classics have such a tail down stance, but the feeling of blindness is largely one of perception. Because the airplane is so narrow, only a small wedge is taken out of the visual field. Unfortunately, it's directly in front of you.

Contact! Brakes! Mags hot!. A good engine will catch on the first blade. If it's your first flight, close the door, as it causes some perceptual difficulties because, with it open, you can see so much better out of the right than the left.

The first thing you'll notice in manoeuvring on the ramp is how hard the stupid heel brakes are to get at because they're snuggled under the seat. That's good. That way you won't be tempted to use them on landing where they aren't needed.

"S" turns are absolutely necessary to see ahead, but they also give you rudder practice. For some reason, maybe it's the light tail, the Cub is quicker to respond to the rudder than most light taildraggers, including the Citabria. It's only a minor difference but noticeable. On takeoff and landing it makes it a little easier than some to over-control.

By all means, do a full 360 turn to clear the pattern before taxiing onto the runway. The pilot sits so far back in the airplane vision is sharply limited by the narrow tunnel of the fuselage and the wings and a full turn is mandatory.

Lined up, suck the stick back and move the throttle smoothly forward. The noise turns into kind of a rattling roar and the airplane will begin accelerating at about the same rate as a heavily loaded Cessna 152. As soon as the power is full on, ease the stick smoothly forward and bring the tail up. If you're of average height you won't quite be able to see over the nose but the visibility improves drastically anyway. There is so much airplane between you and the outside world, there is no doubt when the nose tries to move.

The rudder becomes effective as soon as the power is on and you'll notice the tail moves each time your foot does. The airplane is very stable directionally. In fact, if there is no crosswind, the tail won't move sideways on its own. If it is, stop moving your feet for a second to see if it isn't you causing the movement.

Even on a calm day, the Cub will fly off the ground long before you can get in serious trouble. If there is just a few knots of wind on the nose, it'll leave the ground almost as soon as the tail is up. Solo it leaps off. Dual it takes much longer. The airplane really reacts to extra weight.

A Cub telegraphs everything it does, especially when it is getting too slow to climb. Play with the speed a few knots at a time, while climbing, and you'll find a point where you can actually feel the drag building, control effectiveness falling off and the climb slowing as the nose is brought up. Every Cub likes a slightly different climb speed, usually because the airspeeds are so far off, so just feel it out.

With one on board, a 65 hp Cub in 75 degree air may give as much as 400-500 fpm. 85 hp adds at least another 200 rpm and a C-90 makes you feel like you have a fly-weight tiger by the tail. The increased power is also very noticeable on takeoff acceleration.

As you level off and the speed rockets ahead (read that with a lot of sarcasm), be suspicious of any speed above 80 mph indicated. 75 mph is a pretty standard Cub cross-country speed.

The controls in a Cub set the standard for most of the long-wing Pipers to follow. There's a fair amount of system friction because everything is cable and pulley operated. These days the friction is almost always aggravated by at least one pulley that isn't turning. The friction helps build the perception that the aileron forces are heavy, but they really aren't. The airplane responds very much in proportion to the amount of stick put into it and will actually roll into a bank much faster than people expect, if they put their shoulder into it. The pressures are much lighter and the response higher than a Citabria, for instance. Compared to a C-152, they are about even, although it's hard to compare pressures between a stick and a yoke.

Elevator pressures and rates are matched to the ailerons and you won't even notice the rudder because it mixes in so naturally. And you will need rudder. The airplane has noticeably adverse yaw and the pilot who doesn't coordinate will polish the bottom of his jeans smooth. That's one of the things that makes it such a great trainer

Stalls in a Cub can be what you make them. Normally, they are soft and floppy with very little edge to them. Feeling goes out of the controls in such a noticeable fashion, as the stall approaches, your hand will tell you something is happening, if nothing else does. If you have the door open, the bottom half will begin to float up as the stall is approached. If you crowd the stick back hard or persist in an exaggerated nose-high attitude, it will pay-off, drop the nose and make you light in the seat.

Coming in to land, power back opposite the end of the runway, you risk a stretched muscle as you lean forward trying to get the carburettor heat on the right side wall by your foot. Crank, crank the elevator trim and the airplane will hold an approach speed of 60 mph by itself. It can fly the approach much slower, but there's no reason to.

The Cub is dirtier than most of its contemporaries so its glide slope is a little steeper. It comes down even faster than a Citabria or 152, but at such a slow speed, the pattern is still not super-tight or rushed. Also, there is no such thing as "too high" in a Cub, as it is one of the best slipping airplanes ever invented.

A secret for getting consistent, good landings: Break the glide just a little higher than you think you need to. If you fly it into ground effect expecting to burn off speed and three-point it, you'll almost certainly touch the mains before getting the tail down. For some reason, Cubs appear to have less ground effect than many airplanes.

The nice thing about a Cub landing is that it happens at a near-walk. Actual touch down is around 35 mph, so even if your technique is sloppy, everything is happening so slowly you have all day to set it straight. If you don't have much tailwheel time, try not to think about it. Get the airplane on more or less straight and it will roll more or less straight. Start fighting the rudders simply because it's a taildragger and you think you should be doing something, and it will do a slow motion dance. Best advice in landing a Cub is to make sure it is straight and not drifting and leave it alone after touch down. There's a reason for the saying "...lands easy as a Cub..."

A word about crosswinds and gusts: The airplane is really lightly wing loaded and rides thermals and gusts like a cork. It will, however, handle much more crosswind than most think it will, providing the pilot has a firm hand and a good head. It can, however be overwhelmed. Winds which are an annoyance in a 152 are a challenge in a Cub. In a pinch, diagonal the runway, or turn into the wind at the end of roll-out. Then you have to worry about taxiing. It's entirely possible to land in a wind which is too high to taxi in. In that case, keep the nose into the wind and wait for help to walk you in. More than one pilot has had to coast past the hangars at fifty feet with the door open and the throttle back while yelling for help before landing.

One common J-3 variation seen, by the way, is the Reed Clipped Wing conversion which removes 40 1/2" from each wing root. To many, this makes a good airplane even better. Besides making it capable of loop, roll, spin, type of aerobatics, with 85 hp, it will cruise at nearly 90 mph and its entire handling package tightens up, becoming quicker and more crisp. It will also handle much more wind with the short wings.

Market forces almost always place a price premium on products which have proven themselves both in aesthetics and use. No where is this more obvious than in the J-3 Cub, as it is easily the most expensive airplane in its category. This is a distinction many believe to be well deserved.