phyphox - roller coaster mode - accelaration z direction

[hubert.linders@gmail.com]

This week I enjoyed a supervised flight in a glider (small plane without engine). The flight starts with the plane being pulled by a cable on a winch to approx. 500 m height under an angle of some 40°. 
I used phyphox in "roller coaster" mode, i.e. measuring a in x (along short sides of phone), y (along long side of phone) and z (perpendicular to phone) directions.

I was wondering whether the tilt of the phone influences the measurements in the z direction. In other words, should I correct the values by the cos of the tilt angle?

Thank you.

P.S. Sorry if this question has come up before. I could not find it in the forums.

[Elisabeth Brenner]

This week I enjoyed a supervised flight in a glider (small plane without engine). The flight starts with the plane being pulled by a cable on a winch to approx. 500 m height under an angle of some 40°. 
I used phyphox in "roller coaster" mode, i.e. measuring a in x (along short sides of phone), y (along long side of phone) and z (perpendicular to phone) directions.

I was wondering whether the tilt of the phone influences the measurements in the z direction. In other words, should I correct the values by the cos of the tilt angle?

Thank you.

P.S. Sorry if this question has come up before. I could not find it in the forums.

This is an interesting question! 
The acceleration sensor in your phone has three axes which are parallel to the edges of your phone. You can see in ehich direction the axes are showing by opening the acceleration function in phyphox and moving your phone up and down/left and right/towords you and away from you. This means, that while the glider is being pulled up the sensor is moving the full accelaration from the winch in y-direction and the fraction of the gravitational acceleration in z-direction. In order to verify the gravitational force it is necessary to divide the value you measured by the cosine of the angle in which the glider is being pulled up, as you already noticed. Later, when the glider is in flight mode it should be approximately parallel to the surface of the earth, which means that you do not have to correct the measured values.