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pump, pressurize the system and again check for
leaks. The fuel selector, vents and fuel drains should
be properly marked and tested for proper operation.
NOTE: Many amateur-built aircraft take 5
to 8 years to build. During that time, many
rubber-based oil and fuel lines and cork gaskets
that were installed early in the building
process may have age hardened, cracked,
and/or turned brittle. The builder should
carefully inspect these components and
replace as necessary to prevent a premature
engine failure.
d. Hydraulic system: The hydraulic system
should function dependably and positively in accordance
with the designer’s intent. Retractable landing
gear should be rigorously cycled on the ground,
using both the normal and emergency landing gear
extension system.
e. Safety belt and shoulder harness: These
items should be checked for condition and proper
installation. A review of amateur-built aircraft
accidents has disclosed a significant number of
accidents in which the seat belt mounting hard points
13
5/24/95 AC 90-89A
failed. Each seat belt and shoulder harness mounting
hard point should be built to the designer’s specifications
to ensure that it will hold the harness and pilot
in the aircraft at the ultimate design ‘‘G’’ load specification,
both positive and negative, for the aircraft.
f. Avionics and electrical checks: Test the avionics
systems. Perform an operational check to
ensure the radio(s) transmit and receive on all frequencies.
Inspect circuit breakers/fuses, microphones,
and antennas for security and operation. Test
the ELT for proper operation and battery life. Electrical
systems can be checked for operation of lights,
instruments, and basic nav/comm performance.
Other electrical systems, such as generator/alternator
output can be checked during the engine run-ins, taxi,
and flight tests. Check the battery and the battery
compartment for security and if applicable, ensure
that the battery is properly vented to the outside of
the aircraft. Check the condition of the engine to
airframe bonding (grounding) wire. Ensure that all
electrical instruments operate properly.
g. Cowling and panel checks: Ensure that all
inspection panels are in place, the cowling is secured,
and cowl flap operation is satisfactory. Inspect the
propeller spinner and its backing plate for cracks.
h. Canopy/door locks checks: Ensure the canopy
or doors on the aircraft work as advertised. Double
check the canopy or door lock(s) so the canopy
and doors will not open in flight and disturb the
airflow over the wings and stall the aircraft. If a
canopy jettison system is installed, check for proper
operation when the aircraft on the ground and when
it is on jacks. (Jacks will simulate flight loads on
the aircraft.)
14
AC 90-89A 5/24/95
SECTION 8. WEIGHT AND BALANCE
‘‘Never argue with your spouse or a mathematician’’ Phil Larsh, Accident Prevention Counselor,
Colfax IN (1994)
1. OBJECTIVE. To discuss the importance of
developing an accurate weight and balance calculations
for both test and recreational flights. Additional
information on weight and balance can be found in
AC 91-23A, Pilot’s Weight and Balance Handbook.
a. A good weight and balance calculation is
the keystone of flight testing. Accurately determining
the aircraft’s take-off weight and ensuring that the
center of gravity (CG) is within the aircraft’s design
for each flight is critical to conducting a safe flight
test.
b. An aircraft should be level when weighed,
spanwise and fore and aft in accordance with the
manufacturer’s instructions, and should be in the
level flight position. It is highly recommended that
the weighing be done in an enclosed area, using three
calibrated scales. Bathroom scales are not recommended
because they are not always accurate.
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5/24/95 AC 90-89A
ITEMS WEIGHT (LBS) ARM (INCHES) MOMENT (IN-LBS)
Left Wheel
Right Wheel
Tail Wheel
TOTALS
101
99
42
242
60
60
180
80.8
6060
5940
7560
19560
TOTAL MOMENT = Empty weight CG or 19560 = 80.8
TOTAL WEIGHT 242
FIGURE 2. EMPTY WEIGHT CG
2. DETERMINING EMPTY WEIGHT CG.
a. The sample airplane for determining empty
weight is a single seater, which the kit manufacturer’s
design empty weight of 253 pounds and a gross
weight limit of 500 pounds. The datum line is located
at the nose of the aircraft and the CG range is
　
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