instrument can be flush mounted in its cutout from the rear of  the panel. Integral, self-locking nuts are provided at the rear  faces of the flange corners to receive mounting screws from  the front of the panel. The flanged-type instrument can also  be mounted to the front of the panel. In this case, nut-plates  are usually installed in the panel itself. Nonferrous screws  are usually used to mount the instruments.  There are also instrument mounting systems where the  instruments are flangeless. A special clamp, shaped and  dimensioned to fit the instrument case, is permanently  secured to the rear face of the panel. The instrument is slid  into the panel from the front and into the clamp. The clamp’s  tightening screw is accessible from the front side of the panel.  [Figure 10-135]  Regardless of how an instrument is mounted,  it should not be touching or be so close as to touch another  instrument during the shock of landing. Many aircraft instruments require electric power for  operation. Even nonelectric instruments may include electric  lighting. Only a limited amount of electricity is produced by  the aircraft’s electric generator(s). It is imperative that the  electric load of the instruments, radios, and other equipment  on board the aircraft does not exceed this amount. Electric devices, including instruments, have power ratings.  These show what voltage is required to correctly operate the  unit and the amount of amperage it draws when operating  to capacity. The rating must be checked before installing  any component. Replacement of a component with one that  has the same power rating is recommended to ensure the  potential electric load of the installed equipment remains  within the limits the aircraft manufacturer intended. Adding  a component with a different rating or installing a completely  new component may require a load check be performed. This  is essentially an on the ground operational check to ensure the  electrical system can supply all of the electricity consuming  devices installed on the aircraft. Follow the manufacturer’s  instructions on how to perform this check.  Many instruments contain colored markings on the dial  face to indicate, at a glance, whether a particular system  or component is within a range of operation that is safe  and desirable or if an undesirable condition exists. These  markings are put on the instrument by the original equipment  manufacturer in accordance with the Aircraft Specifications  in the Type Certificate Data Sheet. Data describing these  limitations can also sometimes be found in the aircraft  manufacturer’s operating and maintenance manuals.  Occasionally, the aircraft technician may find it necessary to  apply these marking to an approved replacement instrument  on which they do not appear. It is crucial that the instrument  be marked correctly and only in accordance with approved  data. The marking may be placed on the cover glass of the  instrument with paint or decals. A white slippage mark is  made to extend from the glass to the instrument case. Should  the glass rotate in the bezel, the marking will no longer be  aligned properly with the calibrated instrument dial. The  broken slippage mark indicates this to the pilot or technician.  The colors used as range markings are red, yellow, green,  blue, or white. The markings can be in the form of an arc or  a radial line. Red is used to indicate maximum and minimum  ranges; operations beyond these markings are dangerous and  should be avoided. Green indicates the normal operating  range. Yellow is used to indicate caution. Blue and white  are used on airspeed indicators to define specific conditions.  [Figures 10-136  and  10-137] 10-82 Figure 10-135.  Instrument mounts— flanged (top and middle) and  flangeless (bottom).  Instrument Range Markings Instrument Power Requirements Front mounted Rear mounted Clamp mounted Nut plates mounted in instrument Nut plates mounted in panel Strap tightened by clamp Clamp mounted on instrument panel