Archive for September, 2008

Poking the Bear

Thursday, September 25th, 2008

The loss of a Cessna Sky Catcher last week reminded me just how much we take for granted in the development of a new aircraft and how much risk there is in the exploration of the flight envelope. Early reports indicate that the prototype entered an unrecoverable spin as the test pilot was putting the aircraft through a full spin series.

Things did not go well in the stall under full power with crossed controls. This is not a good place for a normal pilot to be! Witnesses reported hearing a loud pop and seeing sparks that has been attributed to the firing of the BRS parachute system. The chute apparently malfunctioned and the test pilot bailed out. Talk about Murphy’s Law!

In the September issue of AOPA Pilot I had written about the importance of staying well within the edges of the flight envelope. Didn’t know that we’d have such a graphic demonstration so soon. Here’s a perfect example of what happens at or beyond the edges. It’s a tribute to Cessna’s experience in flight test that despite everything going awry, the pilot walked away.

There is both art and science to building a completely new aircraft. The record of manufactured Light Sport Aircraft has been good but as new airframes from a variety of manufacturers, foreign and domestic, enter the market it’s critical to the survival of this segment of the industry, and the pilots who fly them, that they be structurally and aerodynamically sound. And regardless of what machine you fly, going near the edges of the envelope is poking the bear.

Partisan Autopilots

Thursday, September 18th, 2008

A while back we discussed blank avionics screens and how dependent we’ve become on the hardware (Nothing can go wrong…). There was a recent Aviation Safety Reporting System ( NASA ASRS) report on a  wild and crazy autopilot (AP) that went berserk on a Piper Mailbu.

“WE HAD JUST STARTED TO RECEIVE VECTORS FOR THE ILS/DME RWY X APCH INTO ZZZ. THE AUTOPLT SUDDENLY PITCHED THE ACFT NOSE DOWN ABOUT 30 DEGS. WE WENT THROUGH OUR ASSIGNED ALT OF 3000 FT DOWN TO ABOUT 2400 FT. (AIRSPD WAS AROUND 165 KTS.) BEFORE I COULD GET THE AUTOPLT DISENGAGED, THE PLANE SUDDENLY PITCHED UP VIOLENTLY AND THEN PITCHED DOWN AGAIN WITH ENOUGH FORCE THAT EVERYTHING WAS FLYING AROUND THE COCKPIT AND CABIN.”

In a subsequent discussion with the pilot, he said he attempted to manually over ride the autopilot before hitting the red disengage button on the control yoke.  Rule number one on APs is to know at least three ways to retake command. This will be by yoke switch, panel switch, and circuit breaker – at a minimum.

To put it in political terms, APs are extremely partisan – they will always trim against you when engaged in a tug of war. For every pound of force you apply, they will counter. When you finally cut it off, the aircraft will be totally out of trim, and if you’re holding the barely equal and opposite force to balance, it will take strength, time ,and altitude to get things back to equilibrium.

I’m a big believer in APs and that they are essential for single pilot flight in significant IMC. But as with the glass, we need to be ready and able to discipline an unruly crew member and fly to a safe landing.

Speak up

Thursday, September 11th, 2008

In the blog two weeks ago, “It’s working,” I misspoke in saying that controllers were required to provide pilots information on precipitation. After some discussion with FAA officials, while they agreed that safety advisories are critical, would not go so far as to use the “R” word. So, be advised that while FAA is working hard to “encourage” controllers to let you know if there is precip ahead, it’s up to pilots to ask.

The proof on the variability of ATC services came shortly after the conversation. Last week, while I was flying to Michigan, the remains of Hurricane Gustav were raining themselves out over the upper Midwest. The aircraft is equipped with weather datalink so I was getting a reasonably good picture ahead. As you can see, there was a diffuse area of rain farther out and one heavier shower much closer.

Hearing nothing, I asked the controller what he saw. The response was ” There’s precip all along your route to destination.” While accurate, it provided no real information and there was no mention of the shower. When nudged, the controller acknowledged that there was an area of heavier precip. He offered no vectors so we just advised him that we were going to make a small deviation to the West.

Contrast that with the return trip and a weak cold front penetration – again, nothing of real consequence but the controller volunteered that there “was a band of precip about 20 miles wide showing mostly light but some moderate and that preceeding aircraft reported a smooth ride. Based on visual observation, knowledge of the weather system, the data link picture and the controller’s input we decided to press on and emerged on the far side with a little light rain and light turbulence.

The point is be proactive and cautious in gathering weather information. Some controllers will be most helpful and with others you’ll have to work at it. Not unlike pilots.