Small/Private Powered Aircraft



The following information can be found in the 'Instrument / Commercial Manual, Guided Flight Discovery' by Jeppesen, a Sanderson Training Product.

The phrase "attitude instrument flying", "indicated attitude" or just "attitude" will be seen frequently in flying manuals. Attitude instrument flying refers to controlling the aircraft by reference to flight instruments, rather than flying by the pilots' vision.

The following picture depicts various instruments and their 3 respective functions: Control, Performance and Navigation.

Control instruments directly indicate pitch and power. Performance instruments indicate how the aircraft responds to changes to pitch and power. Navigation instruments indicate the position of the aircraft relative to a facility or a fix.

Pitch refers to the airplanes' movement left and right while moving horizontally. Banking refers to the 'tilt' in degrees the airplane experiences.


Note that D - the attitude indicator, gives the pilot an immediate and direct indication of the airplane's pitch and bank attitude. The heading indicator, E, is the primary source of heading information. The Turn coordinator allows the pilot to establish and maintain constant rate turns (angle of Banking the plane). The Altimeter, B, displays the altitude of the plane.


The following is a closeup of an altimeter. This instrument mearsures the vertical elevation of an object above a given reference point. The reference may be the surface of the earth, mean sea level (MSL), or some other point. There are several different types of altitude, depending on the reference point used! The pilot needs to know what reference point is used so that he/she will know what altitude applies. Of course, when there is nonstandard temperature (another number to memorize) aircraft performance suffers and in extreme heat for example, airports will close because the plane is almost impossible to land safely.

Note that the altimeter is connected to a static port (lower left in picture). The static port allows the altimeter to register the outside air pressure. Observe the altimeter setting window (top right). A pilot needs to be comfortable with decimals, units of measure and gauges that change values - much less how to read the numbers on a gauge. This makes the Cartesian coordinate system look easy! The large hand and small hand both point to the same numerals and yet these numbers have different units of measure. The unit of measure is in thousands of feet for the small hand while the unit of measure is in hundred's of feet for the large hand.

Memorizing specific numbers and units are important for a pilot. The 'magic' number in the altimeter setting window is 29.92 inches of mercury, usually written as 29.92 in. Hg.


In order from left to right we have the airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator and vertical speed indicator. The attitude indicator, heading indicator and turn coordinator are considered the three gyroscopic instruments. Gyroscopic instrument operation is based on two fundamental concept that apply to gyroscopes - rigidity in space and precession.

Rigidity in space refers to the principle that a wheel with a heavily weighted rim spun rapidly temds to remain fixed in the plane in which it is spinning. By mounting this wheel or gyroscope on a set of gimbals, the gyro is able to rotate freely in any plane. This allows the gyroscope to be used to measure changes in the attitude or direction of an airplane.

Precession: When an outside force tries to tilt a spinning gyro, the gyro respoinds as if the force had been applied at a point 90 degrees further around in the directin of rotation. This effect is called precession, because the cause precedes the effect by 90 degrees.






Return to Previous Page