Laying on the floor, looking straight up with your head tightly against the rudder pedals is a common position for the general aviation maintenance technician. Some of these small aircraft make this a very uncomfortable way the human body has to be distorted in order to accomplish the task at hand. Some other aircraft make it appear that the technician is stretched out in a bed and is asleep. There are many reasons for having to access this area of the aircraft. Most pilot actions are done at the "instrument panel". All of the flight instruments, engine instrumentation, avionics controls & displays, cabin temperature controls, and flight controls (some aircraft have the elevator and ailerons controls either emenating from the floor or are "coming out" of the side upholstery as "sticks")and engine controls are in this confined area for easy access for either pilot.

Every 24 calendar months, if an aircraft is to be used during Instrument Flight Rules(IFR), the altimeter and static system must be tested for leaks and operation per FAR 91.411. The altimeter, airspeed indicator and vertical speed indicator are the instruments that use the static system in all basic IFR aircraft. The newer aircraft have systems that also need to sense static air such as Air Data Computers and Autopilot Altitude Hold Chambers. Static air is air pressure that is sensed outside of the aircraft at "static ports" that is still or not moving air and is measured perpendicular to the surface of the aircraft. As an aircraft changes altitude the air pressure the aircraft is flying through is constantly changing and the instruments sense this change in air pressure to determine how high the aircraft is flying, how fast the aircraft is flying and how fast the aircraft is moving vertically. This is an over simplified explaination of the system and is used here only to explain why some access is necessary "behind the instrument panel" for the general aviation maintenance technician.

Every aircraft is different from another aircraft. An owner may choose to install new equipment such as an engine monitor. This instrument is installed in a convient place in the instrument panel and looks very neat from the pilot perspective. To the general aviation maintenance technician "behind the instrument panel", the instrument has taken up more of the limited space, the wire bundle has to be routed around all of the existing components, a fuse or circuit breaker must be installed, etc. Depending how many pieces of extra equipment and how well these pieces of equipment were installed determines how much access room there is to remove an altimeter to do the required 2 year tests. An owner may ask "how come it took so long to do my tests?" and the reason may be because the altimeter may not even be able to be seen without removing several other units.

Engine control cables, oil pressure tubes, fuel pressure tubes, manifold pressure tubes, power wires, vacuum system hoses, static system plumbing, pitot system plumbing, wire bundles, avionics cooling air hoses, heater ducts, defroster ducts, flight controls sytems, etc. all have to be secured "behind the instrument panel" to prevent chafing and to allow the flight control mechanisms to move freely.

After being frustrated by trying to remove a piece of equipment for service or repair, a general aviation maintenance technician learns how to install new equipment with forsight. By making a hose a little bit longer, the instrument suction gauge can be unscrewed from the panel, lowered to below the panel and the hose clamps can be accessed much easier than trying to reach up past all of the other items and blindly using ones finger tips to remove the clamps. An extra two inches of wire is easily secured out of the way but that extra 2 inches of wire may allow an EGT gauge to be replaced in 10 minutes rather than one hour.

Modern aircraft have been designed to reduce the clutter "behind the instrument panel". Aircaft designed with "all electric" systems have eliminated the plumbing required for air driven gyros. Increasing aircraft buss system voltage from 14 volts to 28 volts has reduced the size of wires. Flat screen instruments may be two inches thick compared to some instruments that are 12 inches long. Remotely mounted gyros free up a lot of space. All of this makes it easier physically for service but requires a lot of new training for the general aviation maintenance techinicain to learn the new digital age systems.