Bubble level as cheap insurance for inadvertant VFR into IMC

[mike20sm]

I just read the Error Chain article by Michael Robinson in the October 2015 Kitplanes magazine "Aeronautical decision making—it seemed like a good idea at the time"

In it he shares his near death experience when he has no reference to the horizon. Wouldn't a simple bubble level that costs a few bucks and weighs less than half an ounce be a good thing to have on the dashboard? Would the vibrations make it unusable?

[Bryan Cotton]

Nope! You need some sort of a gyro. Try it sometime with a hood and a friend to keep you legal and safe.

[gammaxy]

As long as you are flying coordinated, the bubble can stay centered despite the actual roll attitude of the airplane. Also, when the bubble is not centered, it doesn't provide any useful information by itself about your roll angle unless you are stationary on the ground.

As you mention, a bubble level responds quickly to high frequency vibrations, which is why we typically use a slip indicator with a ball that dampens out the high frequency vibrations.

The slip indicator combined with a way of measuring heading change (magnetic/gyro compass or turn rate indicator) could be used--keep the ball centered and roll the airplane to reduce the rate of heading change. I've experimented with using my magnetic compass (round boat compass), but it does not respond smoothly enough and its response in climbing/descending turns is not easy enough for me to understand while flying that I would want to use it while in an unusual attitude.

I considered getting a cheap DC turn and slip indicator for just this scenario, but a modern battery-backup AHRS display can probably be had for less money and be more intuitive to understand when you need it in an emergency.

[mike20sm]

Thanks for the responses. I understand that once the level quickly goes to one side or the other it loses giving you any useful information, but my intent was that it would be a simple, instant, analog way of determining which way I should push the stick when spatial disorientation and panic sets in and you have seconds to live.
I'll gladly try it out once my flight training progresses from the gliders I'm currently in :P

[MichaelFarley56]

It's a great thought but unfortunately all it would tell you is which way to push the rudder so you're coordinated. There is NO actual roll information given with an inclinometer.

As others have said, your only attitude reference is given by either a gyro or a PFD/EFIS with AHRS. Given the overall cost of some of these new semi portable instruments like the Dynon D10 ( I think that's it) it's probably money well spent for insurance against loss of control in an accidental IFR situation.

[mike20sm]

Plus i forgot that if you're upside down it wouldn't be of much help there either.

[Bryan Cotton]

Mike,
You could try it in the 2-33. Finish the rating first though, that is more important!

[mike20sm]

Copy that. I had a bit of an ah-ha moment when thinking about it further and in 3 dimensions. Imagining going straight down and with the rudder influencing to one side, it would be at one extreme and would have no relation to the roll angle whatsoever. For what it's worth, there are many safety lessons in that article that are not going over my head, I realize the best way to survive is to not get in that position in the first place, I was just doing a bit of brainstorming.

[Rynoth]

Just to toss another option out there, there are several flight apps for ipad that can interface with GPS/ADS-B units that actually have AHRS integrated in them. For example, Foreflight (annual subscription, https://www.foreflight.com/) with the Stratus-2 GPS (about $900 new https://www.sportys.com/pilotshop/ipad- ... ipad.html/) will give you maps, weather, and full attitude display on your ipad. I think Garmin has a similar GPS+software product for Ipad.

As others have said, a bubble level or slip/skid indicator will tell you zero about your actual attitude relative to the horizon in an airplane, they are purely for rudder coordination. This is for the same reason that if you close your eyes or fly into a cloud, your body will eventually lose horizon reference... the feel in the seat of your pants becomes useless, and it's the same feel that the bubble-level would feel.

[Bryan Cotton]

Ask yourself what the bubble would show next to the iced tea in this classic display if Bob Hoover's airmanship.
http://youtu.be/pMWxuKcD6vE