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Bubble Level

Posted By:
Hal Bryan
#1 Posted: 8/11/2010 08:08:46

Could a small bubble level be put on the dash and be used to determine if wings are straight and level?

Paul Dowgewicz
Young Eagles Pilot or Volunteer
#2 Posted: 8/11/2010 08:48:37

 I wouldn't think so. How would you know that the surface you put the level on was built to the proper relationship to the wings?


Ralph King
#3 Posted: 8/11/2010 16:23:30 Modified: 8/11/2010 16:24:46

Well,  what comes first, level wings or a bubble level stating the wings are level?

However, it would only take a few seconds to place the level on top of the instrument panel.  Suggest a level under 1 foot, not a 3 foot level.

Great minds at work here!



Bob Meder
NAFI MemberAirVenture Volunteer
#4 Posted: 8/11/2010 18:50:05

We already have the inclinometer (a/k/a "the ball"), which presumably is installed properly in relation to the wing.  On a level surface, it should show the airplane sitting level, that is, with the ball centered.  In flight, though, it's a different matter, as the inclinometer is showing the quality of the plane's coordinated flight.  In a turn, if the plane is coordinated, it will still be level, since "local vertical" will stay at right angles to the fuselage.  Or, you could be flying straight and level with the ball off to the side, as you're in a slight slip.  (This last is one of my favorite gripes as a CFI when I'm flying in Cherokees.  Someone who doesn't understand P-factor cranks in full right rudder trim during a climb and leaves it there.  The next student [and often, rated pilot], flies with  me, not realizing that they should be carrying some right rudder with their foot.  Then they level out to cruise, holding a course with one wing slightly down, griping how the plane is "out of rig."  When I neutralize the rudder trim, they're always amazed...)

Bob Meder "Anxiety is nature's way of telling you that you already goofed up."
Dave Prizio
Young Eagles Pilot or VolunteerHomebuilder or Craftsman
#5 Posted: 8/12/2010 15:42:01

As mentioned, if you are trying to determine wings level in flight, a bubble level will not work. It will only indicate coordinated flight. Your artificial horizon is your best instrument for determining a wings-level condition in flight.

To level your wings on the ground you should consult the maintenance manual for your airplane if it is cerrtified or the construction plans/assembly manual for homebuilts to see where the proper leveling points are for your plane. It is unlikely that the top of the dashboard is the recommended leveling point for any airplane.

Greg Stauder
#6 Posted: 8/12/2010 19:58:34

You didn't say what your intentions are....do you want the level to indicate while the plane is sitting statically on the ground or to provide you with information in the air?  With the plane sitting still and with the level calibrated, it would work like any level.  With the plane in motion, you would drive yourself crazy trying to figure out what the level would be telling you.

Without going into too much detail, the bubble in the level is a gas and lighter than the surrounding fluid unlike the ball in the turn coordinator vial, which is heavier than the fluid.  That's the reason the level vial is formed or ground so it's convex upward.  The gas bubble migrates to the high point in the vial center.   The inclinometer is curved opposite, concave upward, so the ball centers in the low point, all things being equal by proper rudder inputs.  In a slip or a skid, the inclinometer fluid goes to the "light" side of the vial and the ball goes to the "heavy" side.  Under the same conditions, the gase bubble in the level vial is going to move in the opposite direction. 

For kicks, buy yourself on of those helium birthday balloons and tie the string to the seat belt in the right seat of your car so that it's tethered but still floating free.   Drive down the road, make a turn, and watch which direction the balloon moves as the heavier air inside the car moves toward the outside of the turn.

Of course, you could always install the level and then develop your own mnemonic like "step on the fluid", set your OBS to the reciprocal of the heading you're flying, and be a real flying maverick.