Waypoints

AOPA Pilot Editor in Chief Thomas B. Haines braves IMC in his Beechcraft Bonanza.

Believe some currently circulating literature and you'll quickly come to the conclusion that flying in instrument meteorological conditions (IMC) in anything less than a twin-engine jet with triple redundancy will quickly lead to death. In fact, the most recent communiqué from Parker Hannifin Aerospace Company's Airborne Division, which manufactures aircraft system components for civilian and military applications, says outright that flights in anything other than day VFR without a backup to your vacuum-powered instruments can be deadly. "Failure to follow these warnings and mandates may result in death, bodily injury or property damage," reads the recent letter sent by Parker Hannifin to instrument-rated pilots.

The word mandatory appears in boldface 27 times in the three-page document. The February mailing is at least the third in the past couple of years warning pilots about the dangers of instrument flight without backup systems and proper pneumatic system maintenance.

The failure of vacuum system components and gyros causes only a handful of accidents per year, but when the systems fail in IMC the results are almost always fatal. As the Parker Hannifin information points out, "Despite minimum standard training, many pilots are not able to recognize the gyro instrument loss, transition to 'partial panel' instruments, and then safely fly the aircraft in IMC."

When things go wrong, the equipment manufacturer ends up in court. As a result, Parker stopped manufacturing pneumatic pumps a couple of years ago and is encouraging owners of its existing pumps to follow a strict maintenance program. The company has a "mandatory" replacement schedule for most pneumatic pumps every 500 flight hours or six years. Some models should be changed as often as every 300 flight hours. Others should undergo an inspection every 50 or 100 hours. For a complete list of models and times, see Parker's Web site ( www.parker.com/airborne/).

While the company's literature states that the replacements and inspections are mandatory, in fact, for those of us operating under FAR Part 91, there is no mandatory replacement or inspection interval for the pumps. But it's still good advice.

I replaced the pressure pump on my airplane three years ago when it had about 500 hours on it and when the pump was 10 years old. It was working fine, but I was aware of Parker's recommendations. The pump was already nine years old when I bought the airplane. I won't be waiting another 10 years to change the next one.

Besides regular maintenance and replacement, Parker recommends that anyone flying in IMC understand how the gyro instruments in his or her airplane are powered and how to recognize failures, maintain partial-panel proficiency, and receive training in recognizing spatial disorientation. Another recommendation is to always fly with either a backup pneumatic power source for the air-driven gyros or a backup electric attitude indicator (AI).

As one who regularly flies in IMC, I was not comfortable flying without a backup. In my airplane, which has an air-driven attitude indicator and electric HSI (horizontal situation indicator) and turn coordinator, I could either put in a backup air system or install a backup electric attitude indicator. Aircraft with vacuum systems have the additional option of a backup system that taps the difference between ambient air pressure and manifold pressure to drive the gyros. It is not an option for those of us flying with pressure systems — mostly Beechcraft products — unless the airplane is converted from a pressure system to a vacuum system.

I considered converting my airplane to a vacuum system and then installing a wet vacuum pump. Wet pumps tend to last longer and be more reliable than dry pumps, but they have their own shortcomings (see " Airframe & Powerplant: Spinning Instruments," January Pilot). However, installing a backup pump would only provide redundancy for that one system. By installing a standby electric AI, I could back up not only the source, but the instrument as well.

In the end, I had an R.C. Allen electric AI installed just to the left of the turn coordinator. I've not yet had to rely on it, but I do monitor it during flight and I have flown practice approaches using it as the primary AI.

On the verge of obscurity

Not all cockpit safety enhancements are so visible. In fact, one significant safety enhancement is all but invisible. I call it the "$5,000 button." It's located just to the left of the avionics stack and just below the avionics master. It's marked "WX Clear." Pushing it clears the lightning strikes off of the Garmin GNS 530 moving-map display. The strike positions are analyzed and displayed by the Goodrich Stormscope WX-500 system, which, unlike other Stormscope systems, has no dedicated display. The WX-500 is designed to interface with a multifunction display.

Before installing the WX-500 I considered other models of Stormscopes, believing that perhaps it was better to have a dedicated display for lightning data. Usually I fly with the Garmin display set at a range of either 35 or 50 nautical miles. But given the strategic nature of Stormscope information, I like to look farther out at storms — at least 100 nm and preferably 200 nm. So I was concerned that storms might lurk beyond the moving-map range or that closer to storms the display might become too cluttered to be useful. But, not surprisingly, Garmin does a good job of providing the pilot with useful cues on the moving-map pages that lightning strikes are being displayed at greater ranges. And the dedicated Stormscope page on the GNS 530 is only one knob click away from the primary moving-map page.

Closer to storms, the strikes show up on the moving map, allowing the pilot to easily determine whether the storm will allow passage to a particular waypoint. A couple of keystrokes declutter the screen. A push of the $5,000 button clears the lightning data. How quickly it reappears is a good indication of how strong the storm is. Using a numeric scale, the WX-500 also displays how rapidly a cell is growing or the number of strikes it is tracking.

Steering committee

While the Stormscope is all but irreplaceable on dicey weather trips, it goes for winter months at a time without providing much information. An even more obscure button, though, gets a workout on every flight. The unassuming S-Tec GPSS button hides over next to the autopilot controls. The square black button includes a green LED. When the S-Tec autopilot is in the Heading mode and the LED is lit, the GPSS — a roll-steering system — is driving the airplane. The GPSS causes the autopilot to interact directly with the GPS, bypassing the HSI. As a result, the autopilot flies whatever the GPS commands, including complicated flight paths.

The GPSS, which sells for about $1,000, turns a simple S-Tec autopilot, such as the System 50 in my airplane, into one with nearly the sophistication of an airliner's flight control system. It's truly remarkable to sit back and watch the GPSS anticipate significant turns in the flight plan and smartly maneuver the airplane to intercept right on the centerline of the new course — no overshoots or undershoots. Back-course approaches or DME arcs — no problem. The GPSS has them wired. Even complicated departure and arrival procedures are no problem for the box. Basically, any procedure that's in the GPS's database can be flown by the GPSS. GPSS in essence gives the average George autopilot an MBA.

GPSS is not all gee whiz. I've found it to be a useful aid when flying IFR in busy airspace. When ATC is barking about traffic and three other airplanes on the frequency have call signs similar to mine, it's nice to know that George can keep the airplane pointed in the right direction, never missing a turn, while I contend with other issues.

E-mail the author at [email protected].