Traffic Patterns

by on September 27, 2008

I went out flying yesterday. It was just a little spin around the valley near my local airport. There were clouds at about 10,000 feet and a cold front was trying to push through the area, so I wasn’t too surprised by the bumpy ride. I just pulled the power back and loafed along, enjoying the view, knowing that a slower speed will often lessen the jolts from the turbulence. The reduced speed also kept me a bit farther away from that yellow arc on the airspeed indicator.

After touring the area for a while I decided to enter the traffic pattern and practice a few landings before the forecast winds started to pick up. At that time there was one other airplane in the pattern, a Cessna 150 that had been converted to a taildragger configuration and is often used as a trainer by some of the freelance instructors on the field. I planned my pattern entry to have the other aircraft about to turn on a base leg as I turned onto a right downwind leg near the opposite end of the runway. That way I thought I could maintain our spacing since I intended to make multiple circuits around the pattern. I figured I could always extend my upwind leg if I needed a little more space between us. Of course, all that planning would go out the window if another plane decided to join us but for the time being that was my plan.

My first touch-and-go went fine, though I’m still carrying too much speed on final and tend to skip a little on the first touchdown. This plane has a modified stall strip on the wing root leading edge which gives the plane a decidedly different feel in the landing flare than I am used to. It’ll just take some practice. I touched down, slowed until the tail was firmly on the ground, reconfigured the plane and added power, climbed out, retracted the landing gear, reached 300′ below pattern altitude and turned crosswind, then turned downwind and made my radio call. I didn’t see that other aircraft anywhere in the pattern. Now, I do my best to fly a traffic pattern the same way every time, especially at an uncontrolled airport like my home field. Towered airports put an extra factor into the mix with the controller, hopefully, seeing the big picture and issuing instructions to make the traffic flow more orderly. I had heard the other plane call crosswind and then downwind while I was still on the runway, so I knew I wasn’t in close proximity to him, but that could change if I continued on downwind without having visual contact I was at about mid-field and considering climbing out of the pattern when he made his base leg radio call, but I still couldn’t find him where he should have been. I was about 1500′ from the approach end of the landing runway when I suddenly saw him crossing in front of me left to right on base leg slightly below me and more than a mile from the runway. At that point I had two choices; extend my downwind leg so that I could turn base and arrive on final with sufficient spacing to make a safe landing behind him or make a climbing left turn out of the pattern and start over. I had just heard another call that they were north of the field and entering the pattern, so I elected to maintain pattern altitude and extend my downwind. I finally began my descent after turning on final and lining up with the runway.

I’m of the old school that considers the traffic pattern as the lowest altitude you would normally be flying and, therefore, would be the most critical time to have an engine failure. Since there is a runway in close proximity, that would be the most desirable place to land should that engine fail. Of course, that option is not available should the failure occur on the takeoff leg and possible not even on the crosswind leg, but all other points in the pattern should provide relatively easy access to a paved surface should the engine fail. However,  that is true ONLY IF you fly your pattern within gliding distance of the runway. So, how far can your aircraft glide from pattern altitude? That’s something you’re going to have to determine by referring to your aircraft handbook and factoring in your personal abilities and established personal limits. My aircraft was manufactures in 1948. There are no charts on gliding capability in the minimalist handbook. If there was something written about the glide ratio, it would probably say “refer to crowbar.”

I tried staying farther behind the Cessna 150 on the next pattern, but it just wasn’t meant to be with the speeds the other plane was flying and the distance the pilot was spacing away from the runway.  So, I made a full stop landing and called it a day. As I turned off the runway at mid-field, I saw an individual standing next to the taxiway identification sign with a handheld radio sitting on the sign. I had heard a couple of different voices on the radio and had assumed that the person in the Cessna was talking to an inbound airplane that was north of the airport preparing to enter the pattern, but it became obvious that the person in the Cessna was a new pilot on his first or second solo flight with his instructor monitoring the flight from a vantage point next to the runway.

A new pilot needs a bit more time to sort through things in the traffic pattern, so maybe a slightly wider pattern is a necessity early in training, but is the instructor doing the student a disservice by continuing to widen the pattern, implying that it is the appropriate way to fly a traffic pattern? Yes, the required pattern size and altitude varies with the size and speed of the aircraft, but we should do our best as pilots in command to minimize the risks in the pattern as much as possible.  I was based at another airport a few years ago and an instructor and student substantially damaged a training aircraft when they ran out of gas in the pattern and weren’t able make it to the runway from downwind at pattern altitude. (I won’t get into the running out of gas part.) Instead of having the embarrassment of pushing his aircraft off the runway and to the fuel pumps, the instructor now has an accident on his record.

Minimize risks, fly a pattern that matches your aircraft’s capabilities and teach your students to do the same thing.

NOTES:

A Visual Approach Slope Indicator (VASI) gives a visual indication of a 3 degree descent path to the runway, or a descent rate of roughly 300′ per mile. So, you could turn onto a final 2 mile from the runway at 600′ agl and see an ‘on path’ indication from the VASI.

An average light aircraft has a glide ratio of somewhere around 7:1 to 10:1, meaning for each 7′ or 10′ moved forward in a glide, you descend 1′. So, a glide from one mile would produce a descent of 1/7 to 1/10 of a mile or around 500′ to 700′. Or, put another way, from 600′ agl you could glide a bit over 1.1 miles before reaching the ground.

Here is a link to an interesting glide estimator that gives a bit more information on these calculations and the assumptions made.

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