30 FEBRUARY 2012

Quick, what will be the takeoff distance of your airplane at gross on a 90ºF day? How much crosswind can your airplane handle?

Detailed performance charts were never provided for many of the under 100- to

150-hp vintage airplanes we fly today. Consequently, determining takeoff or landing distances, crosswind components, and other performance figures for these airplanes becomes a guessing game or a “gut feel,” de-pending upon how much time one has accumulated in the plane.

Some years ago I participated in a 100th anniversary family reunion. The gathering was held in early August on a southwestern Minnesota farm. My cousin, who owned the farm, asked that I fly my J-3 and offer rides. Everyone could then take photos of the horse-drawn wagons, bundle pitching, and threshing that was tak-ing place. I agreed, and we cut a short runway in the hayfield adjoining the farm.

Not having ever done anything like this previously, I truly didn’t know what I didn’t know. However, I did pace off the runway while checking for holes and other obstructions that might hamper a smooth take-off or landing. There were trees at the east end and low-hanging power lines at the west end of the freshly carved 1,400-foot runway.

The next morning I arrived in the 65-hp J-3 Cub. By midmorning the temperature hovered around 85ºF and the humidity was high. On a normal day in this part of the country the wind is usually westerly at about 15 to 20 mph, but not today; it was nearly calm. I thought to myself that the trusty Cub was surely going to get a tough workout hauling passengers under these condi-tions. To my benefit, though, I could take off to the west and land to the east, saving a lot of taxi time.

Before hopping the first ride, I paced the runway and placed a visible marker at the halfway point, thinking that if I wasn’t airborne by the marker, I had adequate runway to shut down and stop.

When the threshing machine fired up, I began hop-ping rides. The first dozen or so were uneventful. After every exchange of passengers, I noticed the ride line

getting longer, and some of the awaiting passengers were rather stout. I pointed one individual out and mentioned to my wife, Sharon, that the stout cousin should be placed in line so that he received his ride when the fuel tank was near empty. Unfortunately, he was nowhere to be found at that point, so I gave an-other ride and shut down to add fuel.

While adding fuel and getting a drink of water, the stout fellow reappeared and hopped into the front seat. Realizing what had happened, I suggested he might want to wait, but it was his turn and he was adamant about getting his ride. I didn’t want to cause a problem, so I reluctantly started up and taxied into position for a takeoff, all the while thinking that if I’m not airborne at my marker, I’ll shut it down.

The poor Cub began rolling, and sure enough, we were off the ground just at midpoint. After climbing to about 15 feet, I couldn’t coax another inch of alti-tude out of the laboring J-3. With the power lines ap-proaching and no room to go under them, I decided a “gentle” skidding turn to the right was in order, as it was open unobstructed flatland for several miles. After completing the turn and continuing in a northern di-rection at 15 feet, my cousin asked why he was getting a ride different from the others. With palms sweating and knees shaking, I didn’t want to tell him what re-ally just happened. I responded, “I thought you might want to try something different.” Several more miles later, we had reached 200 feet and turned back for his photo pass followed by the landing.

I shut down the engine and climbed out, explain-ing to Sharon that I needed a break for a few minutes. After regaining my composure, the rides continued un-eventfully for the remainder of the day.

I’ve thought about that incident many times since then and vowed that I would never let myself get talked into a similar situation ever again. Additionally, I also vowed that I would get to know the Cub perfor-mance much better. The result is an accumulation of several rules of thumb. These rules will apply to most all of the low-horsepower vintage airplanes we fly.

A 10 percent increase in aircraft takeoff weight will

BY Steve Krog, CFI

THE Vintage Instructor

Some things you learn aftergetting your certificate

VINTAGE AIRPLANE 31

result in a 20 percent increase in takeoff distance.Density altitude increases the takeoff distance by

about 120 feet for each 10ºC above the standard tem-perature (15ºC [59ºF]).

For each knot above VREF (recommended approach speed), the touchdown point will be 100 feet farther down the runway.

On another occasion I learned another valuable les-son. An old aviator friend from out of town had stopped by the airport. During our short visit he mentioned that he hadn’t flown a Cub in more than 30 years and would like to make a short flight. I agreed, and he hopped in the front seat. I didn’t have an intercom in the Cub, so I mentioned that I would make the takeoff and then shake the stick, indicating that it was his airplane. I would hold my hands up for him to see, so that he could visually confirm that I was not on the controls.

After takeoff I shook the stick followed by hold-ing up my hands. He took control and began flying around the area. It was early afternoon, so we were experiencing the normal thermal and bump activity. I anticipated that he would fly for a few minutes and then return the controls to me by shaking the stick and holding his hands up. Minutes passed, and he contin-ued to fly . . . or so I thought.

My old aviator friend made a few turns and then sup-posedly shook the stick. However, I just assumed that it was the turbulence moving the stick and continued to let him fly. He never did hold his hands in the air. Fif-teen minutes later we were still flying, but it was mostly straight and level with a slow descent. When we got down to about 100 feet, I decided to take the stick, leveled the airplane, and returned to the airport.

After landing, I asked him if he knew the owner of the farm he was intending to buzz. With a look of complete surprise he stated that he wasn’t flying! He thought he had given the controls back to me and fig-ured I was lining up with the farm for a low pass.

Thankfully, nothing serious happened, but it made a lasting impression on me. I decided I would never again give a ride to anyone without clearly explaining and then demonstrating how to transfer the controls from one to another! Another lesson learned.

Shortly after my experience, I learned that an ac-quaintance had destroyed his newly restored Stearman under similar circumstances. He had taken a friend for a pleasure flight, and neither made an effort to discuss the exchange of controls before the flight. Each thought the other was flying, and the aircraft was flown into the ground. Thankfully the only damage to the two fellows involved was a broken ankle and a lot of bruises, but a beautiful airplane was destroyed.

Flying airplanes is a constant learning experience. A local pilot taught me another good lesson one summer Sunday afternoon. He hadn’t flown in a while and de-cided it was time to get current, as his family was com-ing for a visit and he wanted to give some rides. As he

taxied past my hangar, he waved and asked if I’d ride along while he did a few landings. I had a little time on my hands, so I decided to join him. What could it hurt?

The wind was fairly strong from the north, but rather than taxiing to favored Runway 36, he continued on to Runway 29. I thought that a bit odd, but maybe he wanted to work on his crosswinds. As he aligned himself with the runway centerline, I sat back to enjoy the ride. After applying full power we instantly found ourselves in a 90-degree turn to the right. I sat up and hit the left rud-der, realigning with the centerline. A half-second later we entered a 90-degree turn to the left and headed for the drainage ditch. I hit the right rudder hard, again align-ing with the centerline. Then he hit the right rudder. The tires were squealing, the tail was now in the air, and we were headed for the swamp on the right side of the run-way. I instantly pulled the throttle to idle, switched the mags off, and steered the airplane off the runway into the tall grass. I felt the airplane would go over on its nose, so I forced it into a ground loop. When we finally came to a stop my friend asked, “What just happened?”

After giving the incident some thought, I came to a conclusion: I should have spoken up when we didn’t use the best runway. He was so excited about flying again that he was oblivious to the wind. I learned an-other valuable lesson! When two pilots are at the con-trols, always confirm who is pilot in command and what is expected of the accompanying pilot!

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