Archive for June, 2013

SWAP

Thursday, June 27th, 2013

storm radarBefore we leave the convective weather topic for a while, think about the emphasis the airlines put into staying out of big, sparky clouds. As you can see from the graphic, there was a lot of weather approaching the DC area from the west on Monday afternoon.

I ‘d committed to a Tuesday morning presentation in Milwaukee, and one needs to allow extra time in convective season whether flying GA or on the airlines because the airspace can turn ugly on almost any afternoon. A gate hold was put into effect for my flight that was scheduled for a 1400 departure. At 1600 we left the gate, and at about 1700 the flight launched toward the line of weather. The delay was not because the Boeing 737 couldn’t avoid the weather on its own but rather that the system could not handle 30 or so flights all headed westbound and all working through the same hole. (Tell me again how NextGen is going to resolve this.) It was a nice ride with only some light turbulence.

Here is a definition of the Severe Weather Avoidance Plan (SWAP) from the National Weather Service Center Weather Service Unit in New York: 

“When an isolated convective cell initiates, an aircraft may be able to deviate around it or fly over the top of it. However, when multiple cells develop and organize into clusters or lines, jet routes in the path of these storms are forced to close. Aircraft using these routes must deviate to other routes. A SWAP is implemented when a significant number of routes are either closed or forecast to close, thus lowering the capacity of the National Airspace System (NAS).”

The Collaborative Convective Forecast Product (CCFP) leaves little doubt as to where the weather was and that the tops, at FL390, were above what most light GA aircraft could tackle. Think about how much teamwork and planning goes into running the system. It should be clear that scheduling is clearly secondary to safety. It’s a lesson some GA pilots should learn.

Looking speculatively at the situation above, there are several reasonable options. An end run to the south might work, assuming the line did not build much farther down that way. It would be at least an hour (or more) detour in most low-altitude light aircraft, but it would keep one out of the cluster—which is a good place not to be.

The second option is to merely wait a few hours until the line passes. That creates other opportunities for difficulty such as more storms forming or darkness, as night approaches.

The third option, which is my favorite in summertime flying, is to go early in the day which eliminates much of the storm problem in the first place. The idea is to be on the ground by early afternoon. That’s not always possible and there are early morning storms, but it’s one of the most reliable strategies.

Option four is simply to cancel, and sometimes that’s the best choice. As we’ve said many times, there is no place one has to be.

Maybe all of us should develop a SWAP strategy. The pros do it.

We hope you were able to catch our Thunderstorms Avoidance webinar last week. Be sure to check out the other products from the Air Safety Institute to help keep you out of harm’s way, such as the Thunderstorms and ATC (requires Flash player) online course, our Thunderstorm Avoidance safety quiz, and our Accident Case Study: Time Lapse. These products are funded by donations to the AOPA Foundation. If you like what you see, please consider a donation today.

Gust Fronts

Wednesday, June 19th, 2013

airplaneLast week was the Air Safety Institute’s annual Storm Week. We only do it once a year despite some TV channels celebrating atmospheric mayhem weekly, gusting to daily and sometimes hourly. The webinar that we recorded for posterity was attended by over 900 pilots who had some interest in learning more about boomers from a controller’s perspective, and with some guidance on datalink thrown in. An area we did not spend much time on but deserves more attention is gust fronts. This phenomenon, which does not accompany every thunderstorm, can really make a hash out of your arrival or departure.

To misquote Forrest Gump, “Thunderstorms are like a box of chocolates…”, etc. What looks the same may not be, and benign can turn ugly really fast. The gust front is on the leading edge of the storm and forms when the storm hits maturity. A ripping good downdraft descending at, say, 3,000 feet per minute, has nowhere to go when it hits the ground—except out—usually to the front of the storm. The winds can go from practically nothing to 40 knots in the blink of an eye.

I was in the back seat of a Cessna 172 some decades ago with a new private pilot up front as PIC and an Air Force pilot friend, who was getting his checkout at McConnell Air Force Base in the F105 (affectionately known as the Thud). We’d flown to an airport east of Wichita and it had begun to cloud up, so we decided to return to Cessna Field on the east side of the city. On the west side, about 15 miles away, a pretty healthy thunderstorm had set up shop and shut down operations at the airline airport.

The winds were five knots or so from the northwest as we lined up on short final to Runway 35 but rapidly increased to about 15 -20 knots from the west—close, if not beyond,  the demonstrated crosswind capability of the Skyhawk and well beyond the demonstrated crosswind capability of the pilot. We were about 10 feet off the ground when my Air Force friend strongly suggested a go-around. It was a good call! We headed out east and he turned to me, as senior Cessna driver, and said something to the effect of, “You get your posterior up here and land this thing!” I’m still not quite sure how we managed the seat transfer, but he came aft, I went forward to the right front seat, and we came back around for a second try. By that time the gust had passed and the winds were fairly steady from the west at about 12 knots. I’d like to say it was a heroic save on my part, but it wasn’t—just a normal  Kansas crosswind, and that’s what Cessnas are built to handle.

But there were several good lessons: Don’t judge a thunderstorm by its looks, sitting in the back seat makes it a long stretch to the controls, and when in doubt—go around! I remember all three to this day.

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Parts & Pieces Matter

Thursday, June 13th, 2013

aircraft maintenanceIn about 10 to 15 percent of GA accidents something mechanical broke or failed to work as planned. Usually it’s the engine, sometimes the landing gear (retractable), and very seldom the flight controls. But if ever there were a place for Murphy to cause mischief that might be it.

Here’s why: Flight controls almost always work. The systems are relatively simple, well-designed, and robust. They are checked on every annual (supposedly), and I would guess that 99.999 percent of the time everything is good.

But a recent NASA ASRS report indicates that just when you thought it was OK to ignore that most reliable system…

Weather:  clear, wind 030 at 7 kts. Student was landing on Runway 08. Upon touchdown the airplane veered significantly to the left. Student attempted to straighten the ground roll using rudders. Student then stated she could not move the rudder. Instructor immediately initiated a go around. Once airborne and stable, instructor verified rudder pedal was ‘stuck.’ Upon visual inspection, instructor noticed that the bushing holding the left rear rudder pedal had come loose when the cotter pin had come off and bushing had become lodged into the side wall of the airplane. Instructor managed to reposition the bushing and landed without incident. Mechanic replaced the cotter pin and verified aircraft was airworthy.

Although this flight ended without incident, it could have been catastrophic had either a less-experienced PIC and/or a more aggressive maneuver (spin) been in operation. My suggestion is to “wiggle” the rudder pedals prior to spin entry and landings to ensure the rudder pedals are not stuck. A visual inspection would not hurt either.

We don’t know the general condition of the aircraft, so it’s possible that the cotter pin was just the tip of the proverbial iceberg, but it does serve as a reminder that all those seemingly inconsequential pieces can become critical at exactly the wrong time. Has anyone suffered a similar or worse mishap?