This is especially true in the case of hand-held receivers. The  use of hand-held receivers for VFR operations is a growing  trend, especially among rental pilots. Typically, suction cups  are used to place the GPS antennas on the inside of aircraft  windows. While this method has great utility, the antenna  location is limited by aircraft structure for optimal reception  of available satellites. Consequently, signal loss may occur  in certain situations where aircraft-satellite geometry causes  a loss of navigation signal. These losses, coupled with a lack  of RAIM capability, could present erroneous position and  navigation information with no warning to the pilot.  Another way to minimize head-down time is to become very  familiar with the receiver’s operation. Most receivers are not  intuitive. The pilot must take the time to learn the various  keystrokes, knob functions, and displays that are used in  the operation of the receiver. Some manufacturers provide  computer-based tutorials or simulations of their receivers.  Take the time to learn about the particular unit before using  it in flight.  While the use of hand-held GPS receivers for VFR operations  is not limited by regulation, modification of the aircraft, such  as installing a panel- or yoke-mounted holder, is governed by  14 CFR part 43. Pilots should consult a mechanic to ensure  compliance with the regulation and a safe installation.  In summary, be careful not to rely on GPS to solve all VFR  navigational problems. Unless an IFR receiver is installed in  accordance with IFR requirements, no standard of accuracy  or integrity can be assured. While the practicality of GPS is  compelling, the fact remains that only the pilot can navigate the  aircraft, and GPS is just one of the pilot’s tools to do the job.  Always check to see if the unit has RAIM capability. If no  RAIM capability exists, be suspicious of a GPS displayed  position when any disagreement exists with the position  derived from other radio navigation systems, pilotage, or  dead reckoning.  Check the currency of the database, if any. If expired, update  the database using the current revision. If an update of an  expired database is not possible, disregard any moving map  display of airspace for critical navigation decisions. Be aware  that named waypoints may no longer exist or may have been  relocated since the database expired. At a minimum, the  waypoints to be used should be verified against a current  official source, such as the Chart Supplement U.S. or a  Sectional Aeronautical Chart.  While a hand-held GPS receiver can provide excellent  navigation capability to VFR pilots, be prepared for  intermittent loss of navigation signal, possibly with no RAIM  warning to the pilot. If mounting the receiver in the aircraft,  be sure to comply with 14 CFR part 43.  Plan flights carefully before taking off. If navigating to user- defined waypoints, enter them prior to flight, not on the fly.  Verify the planned flight against a current source, such as a  current sectional chart. There have been cases in which one  pilot used waypoints created by another pilot that were not  where the pilot flying was expecting. This generally resulted  in a navigation error. Minimize head-down time in the aircraft  and maintain a sharp lookout for traffic, terrain, and obstacles.  Just a few minutes of preparation and planning on the ground  makes a great difference in the air.  VFR waypoint names (for computer entry and flight plans)  consist of five letters beginning with the letters “VP” and are  retrievable from navigation databases. The VFR waypoint  names are not intended to be pronounceable, and they are not  for use in ATC communications. On VFR charts, a stand­ alone VFR waypoint is portrayed using the same four-point  star symbol used for IFR waypoints. VFR waypoint collocated  with a visual checkpoint on the chart is identified by a small  magenta flag symbol. A VFR waypoint collocated with a  visual checkpoint is pronounceable based on the name of the  visual checkpoint and may be used for ATC communications.  Each VFR waypoint name appears in parentheses adjacent  to the geographic location on the chart. Latitude/longitude  data for all established VFR waypoints may be found in the  appropriate regional Chart Supplement U.S.  VFR waypoints provide VFR pilots with a supplementary  tool to assist with position awareness while navigating  visually in aircraft equipped with area navigation receivers.  VFR waypoints should be used as a tool to supplement current  navigation procedures. The use of VFR waypoints include  providing navigational aids for pilots unfamiliar with an area,  waypoint definition of existing reporting points, enhanced  navigation in and around Class B and Class C airspace, and  enhanced navigation around Special Use Airspace. VFR  pilots should rely on appropriate and current aeronautical  charts published specifically for visual navigation. If  operating in a terminal area, pilots should take advantage of  the Terminal Area Chart available for the area, if published.  The use of VFR waypoints does not relieve the pilot of any  responsibility to comply with the operational requirements  of 14 CFR part 91.  VFR Waypoints  Tips for Using GPS for VFR Operations  16-33 