Archive for the ‘Safety’ Category

Air Pockets or Worse !

Wednesday, May 14th, 2014

wavesToo many airlines think we can’t handle the truth, and so the flight crew refers to “bumps” rather than turbulence. You’ll even hear media types occasionally mention “air pockets,” a long outdated terminology. For light GA, turbulence is often uncomfortable and occasionally dangerous.

The Air Safety Institute, working with the FAA and the NTSB, is highlighting turbulence this month as part of our 2014 weather education campaign. Turbulence comes in a variety of forms and can be merely aggravating or really bad news.

Convective turbulence from thunderstorms is probably the worst and disassembles aircraft about six times a year. It often takes the form of the pilot first losing control, and then the hardware starts to come apart after all speed limits are exceeded.

But sometimes the bounces are in the form of waves and rotors. If you’ve done much flying in any sort of mountainous or hilly terrain you’ve likely experienced the wave—sometimes visible with lenticular clouds but not always, especially when the air is dry.

My first exposures to the wave were perplexing at best. In cruise flight with the autopilot in “altitude hold,” the airspeed was going up and the A/P was trimming nose down. Pretty cool—free lunch? You know the deal on lunches, because a few miles down the road just the opposite happened as the nose went up and the airspeed just went to pot. Thinking a navigational error had placed me into the Bermuda Triangle I called ATC to ask for a block altitude. It was, of course, the smooth part of the down wave.

However, altitudes below the smoothness can be a dentist’s delight—rough enough to jar loose fillings. Airspeed control is the key, and on descent in those types of conditions one should be well acquainted with VAmaneuvering speed. VA is one of those counter-intuitive concepts. As the gross weight declines, the slower the maneuvering speed. The published number in the handbook or on the placard is appropriate at max gross. If you’re lighter than that—slow down.

Airspeed bumps around a good bit in turbulence, and if everything is stable “right at” VA, a gust can increase the speed by 10 knots in the blink of an eye. When flying an older aircraft there is no comfort knowing that if the bozo that flew it before you exceeded VA, and got into heavy turbulence, some of the margins built into the structure when new have been used up. How much? Good question. Slow down.

Pay attention to pireps and Center Weather Advisories—the loss of a modified Cessna P210 is instructional. Even moderate winds over big mountains deserve to be treated with great respect. Maybe there’s something to this air pocket thing after all.

A few questions in SD

Wednesday, May 7th, 2014
9D0 sectional and turbine inset

                                      MEF 2,700 feet

There was a tragic accident in South Dakota last week when a PA-32R (Piper Lance) collided with a wind turbine. There aren’t that many people in South Dakota, so the loss of four prominent young men in the cattle business is really unfortunate. Losing anyone in an aircraft accident is unfortunate.

An accident chain seems clearly present here, but the usual caveat is that this is preliminary and there might be a completely different causal factor:

1) Fatigue? The accident is estimated to have occurred shortly after 9 p.m. CDT. Based on distance from the departure point in Texas, the flight would have been approaching four hours or more depending on headwinds. That means departure was made at the end of a long day and facing difficult weather. Better to leave a couple of hours earlier?

2) Weather? According to the NTSB preliminary report “The closest official weather observation station was…Pierre, South Dakota, 37 miles west of the accident location. The routine aviation weather report…, issued at 2124,..wind 010 degrees at 19 knots, visibility 10 miles, sky condition broken clouds at 1,000 feet, overcast at 1,600 feet, temperature 06 degrees Celsius (C), dew point temperature 05 degrees C, altimeter 29.37 inches, remarks, ceiling variable between 800 and 1,200 feet.”  Technically it was VMC but this really is IFR weather. Why no IFR flight plan?

3) Low Level? The impact with the wind turbine was about 300 agl. The tower itself was measured at 215 agl or 316 agl depending on which symbol you choose. The blades may extend well above that. Tower symbols are charted south of the airport about 10 miles. Why fly that low…to avoid ice perhaps, or to maintain ground contact?

From what we know now, subject to change, there was no IFR flight plan filed even though the pilot was instrument rated. Don’t know if he was current. There was no reported communication with ATC. The weather system was widespread, so it’s unlikely that the pilot was surprised by the rain and fog. The temperature/dew point spread tells the story. It’s a “fur piece” from Texas to South Dakota especially at low altitude and bucking a 30-knot headwind. There is no indication they stopped for fuel, so could fuel exhaustion be an issue?

Armchair quarterbacking would say “controlled flight into tower (CFIT)” and VFR into IMC. Possible fatigue, possible fuel shortage, definite low ceiling and visibility, definite dark night, definite towers and apparently a strong desire to get home after a weekend in Texas: If all that is as it appears, it’s a risky proposition.

TAP—The Air Safety Institute has a Terrain Avoidance Plan Safety Brief that will keep you out of the rough. In this case the absolute bare minimum altitude for VFR is charted at 2,700 feet msl (Maximum Elevation Figure) with the tops of the turbines around 2,500 feet msl. Personally, I’d add several hundred feet to that.

The question none of us will be able to answer is why? Those that we lost can no longer explain. Would sure like to better understand the human mind. Too many smart, capable people are lost this way.

Free aviation safety programs from the Air Safety Institute—including ASI’s Do The Right Thing: Decision Making for Pilots online course—are available to all thanks to support from pilots everywhere. Help us to keep educating pilots on safety issues by donating to the AOPA Foundation today.

Slip Sliding Away & Goldilocks

Tuesday, April 29th, 2014
Photo: Brianna Bentley

Photo: Brianna Bentley

It’s not the first time—and certainly won’t be the last—that someone slides off the end of a moderately short but adequate runway. This “oops” was an expensive mistake from a hardware perspective, but fortunately there were no injuries.

A Citation CJ3 slid off the end of a 4,000-foot runway this weekend and into a water trap (appropriately named) of a nearby golf course. (Mind if we play through?) Golf etiquette notwithstanding; remember how critical energy management is to safe landings. It’s good practice to be on speed, on altitude, and on the center line, no matter how long or wide the runway is. I refer to this as the Goldilocks parameters: Not too much, not too little—just right.

In this accident we know mostly what happened—aircraft went off the end. Runway length according to the flight manual was sufficient for the aircraft. There was a displaced threshold of about 350 feet but, even with that, if Goldilocks was in the cockpit everything should have worked. This is also assuming little or no runway slope, no standing water or other contamination, and little or no tailwind. These affect all aircraft but are more critical in jets.

In bigger aircraft and jets the Vref, or landing speeds, can change significantly. This is based on weight, since fuel or passenger load can be a much larger percentage than on a light aircraft. But even in a Cessna 182, a 5- to 7-knot variation can make the difference between a floater and a sinker. Obviously to get book performance, flaps have to be full down. The CJ3 has ground flaps and speed brakes to help dump lift, and timely deployment is essential. Too soon to know if and how they were deployed.

These aircraft are typically equipped with angle of attack indicators, which will automatically adjust the speed for weight, configuration, and density altitude. Keep the energy on the green meatball (1.3 Vso) and you’ll get book performance every time.

The accident report will clarify more of the “what” and then it’s up to us to understand the “why.” If Goldilocks isn’t in your cockpit beware the wolf. In Florida—which is where this mishap occurred—one more caveat: It would be a pity to be gator bait after having survived unscathed!

ASI recently completed a “Takeoffs and Landings” video series made possible by the Canadian Owners and Pilots Association and the Donner Canadian Foundation. The videos cover short field landings, normal takeoffs, determining an abort point, crosswind landings, stabilized approaches, and the base-to-final turn. A great opportunity for pilots of all levels to hone these important skills.

What more, if anything, should we be doing to raise awareness?