Monday, May 26, 2008

Who's got The Button


With all the activity surrounding my ferry flight, I've had precious little time to keep up with happenings in aviation. As I made my way through the backlog of reading over the last few days, I noticed that Cirrus has released a version of their SR22 aircraft with a G1000 system instead of the usual Avidyne system. And in classic Cirrus fashion, their marketing team assures us that they are not just jumping on the G1000 bandwagon, no sir. This G1000 has been Cirrusized. The main differences between the usual G1000 and the Cirrusized G1000 are fairly limited, but in addition to the SVS option (Cirrus refers to it as "Perspective") there are some are big improvements.

First, the screens are 12" instead of 10" because bigger is better, right? Well at least there will be room for more fingerprints on the screen surface. The second difference is that this G1000 installation provides a keypad, something that has heretofore been limited to a few aircraft like the Columbia, Mooney, Bonanza, and Baron. If you ask me, all G1000 installations cry out for a simpler way to enter waypoints and limiting the keypad installation seems like more of a marketing gimmick that anything else. But look closely at the keypad and autopilot interface, because there is something revolutionary here.

One of my biggest gripes with the G1000 has been the design of the BARO knob (used to set the barometric pressure for the altimeter) and the CRS knob (used to set the HSI course when in VOR mode or in GPS with OBS mode engaged). In the traditional G1000, these two knobs are concentric with the large outer knob being the BARO setting and the smaller, inner knob being the CRS knob. If I had five dollars for every time I saw a pilot inadvertently change the BARO setting when they meant to adjust the HSI course, well I could have already retired and be sitting on the porch of my beach house, sipping rum from a glass with a little umbrella.

Next to the Cirrus keypad are heading, course, and altitude select knobs. These knobs no longer appear on the G1000 PFD or MFD. That's right, the combined CRS/BARO knobs are no more in the Cirrus. What's more, the frequently used heading and altitude select knobs are in a separate, easy to remember location. Pretty cool.

The other Cirrus difference is an additional button on the autopilot interface labeled LVL, which is being referred to as the Blue Button or the Panic Button. The idea is that if you enter an unusual attitude that does not exceed 75˚ of bank and/or 50˚ of pitch, pressing the LVL button will engage the autopilot and should bring you back to straight and level. I think having a single button to level the aircraft could be a handy thing during high workload moments, but a button for unusual attitude recovery?

One of the most basic skills an instrument pilot learns is to recover from an unusual attitude, especially when they are experiencing spatial disorientation - their inner ear is telling them something that is at odds with what their instruments are telling them. There are two basic unusual attitude scenarios: Nose up and nose down. A common mistake when trying to recover from an unusual attitude is failing to control airspeed, so the first thing to do is look at the airspeed indication. A fast or increasing airspeed means the nose of the plane is pointed down. A slow or decreasing airspeed means the plane is pointed up. I train my instrument students to initiate recovery by adjusting power first.

When recovering from a nose-up unusual attitude, I teach instrument candidates to think "stall recovery": Full power, reduce the pitch attitude, then level the wings. Nose-up unusual attitudes are often caused by a malfunctioning, runaway pitch trim. If that's the case, I can't imagine that the LVL button is going to be of any use since it relies on pitch trim which has malfunctioned.

The nose-down pitch recovery requires that the pilot initiate a spiral dive recovery, just like you learned when you first tried steep turns as a student pilot: Reduce power to idle, level the wings to reduce load on the airframe, then pitch up. If you don't level the wings before pitching up, you not only risk over-stressing the airframe, you may only succeed in steepening the bank angle with the resultant altitude loss and increase in airspeed - referred to by some as the JFK Jr. syndrome.

Assuming the Cirrus autopilot doesn't have autothrottle capability, I can't imagine how the level button can level the aircraft without potentially overstressing the airframe. Perhaps the designers are relying on the rigidity of the Cirrus composite airframe and its hugely effective ailerons. One would assume that they have tested this system and found it works satisfactorily, but I'm still curious.

More importantly, I wonder if this kind of system is going to breed a new kind of instrument pilot with questionable instrument flying skills. It seems doubtful that designated examiners will allow pilots to use the LVL button when demonstrating unusual attitude recovery during an instrument rating check ride, so maybe we're safe for now.

The one thing I wish Cirrus would fix is their own button design. Cirrus needs to protect important bolster switches from being inadvertently turned off. I actually had a student do this during an ILS in actual conditions. Reaching for the heading bug knob, we hit a big bump, his hand came down squarely on the avionics switch, the switch went off, and all the screens and G430s went dark. In Cirrus' G1000 design, the PFD softkeys are very close to the bolster switches and it's easy to imagine bumping one while trying to access a softkey in turbulent conditions. Perhaps they can Cirrusize that problem away ...

3 comments:

PlasticPilot said...

I agree with you on the CRS / BARO combination on the G1000. I guess Garmin made it so to save space below for the autopilot controls...

Regarding switching-off the avionics in flight, I did it myself twice with an classical equipped plane, where the Avionics master is places beside the DME NAV1 / NAV2 switch (click here to read the full story).

Hopefully this did not turned the classical instruments off... I just lost auto-pilot, HSI, transponder, voice comm and GPS ;-).

Blake said...

Ugh.. when will these companies use QWERTY keyboards instead of the tranditional ABCDE style keyboards?

I'm sure by now that ALL pilots are proficient with computer keyboards.

I can type CYYZ without looking at the keyboard at all using QUERTY. But have to "hunt and peck" with the ABCDE style keyboard that are used nowadays.

John said...

I use the Dvorak layout myself, but even a QWERTY would be preferable.