Engine Power Loss Accident Prevention
Note: This document is kind of dated (ok, really dated ;-), so the
statistics are probably no longer relevant, but the safety information is
still valid. Also, this is a general FAA document, so while it isn't
ultralight specific per-se, the information can be applied to any flying
device, so it is worthy of inclusion here. Fly safe! -Jon
AC 20-105A - ENGINE POWER LOSS ACCIDENT PREVENTION
Department of Transportation
Federal Aviation Administration
Initiated by: AWS-340
This advisory circular updates statistical information and brings to the
attention of aircraft owners, operators, manufacturers, and maintenance
personnel the circumstances surrounding engine power loss accidents with
recommendations on how, through individual effort and consideration, those
accidents can be prevented.
Advisory Circular 20-105, Engine Power Loss Accident Prevention, dated
6/9/78 is canceled.
A review of Federal Aviation Administration's General Aviation Accidents
Factual Reports for the years 1977, 1978, and 1979, that list engine
failure as a cause, showed a total of 2,608 accidents. Those accidents
resulted in 473 fatalities and 1,396 injured persons. For several years,
"power loss" has been the greatest single type of general aviation accident
and during this review period accounted for 19.9 percent of all accidents.
Analysis shows that accidents have resulted from:
- Personnel Errors.
- Operations which exceeded the limitations of the powerplant.
- Failure of maintenance personnel to utilize acceptable maintenance
- Failure of Engine, Engine Part, or System Component.
- Engines were operated beyond the overhaul time recommended by the
- There was noncompliance with airworthiness requirements regarding
inspection, overhaul, repair, preservation, and/or replacement of
- Design changes and alterations were completed without engineering
evaluation and approval.
- Parts failed due to operation outside operating limitations; i.e.,
overtemp, overboost, low oil pressure, etc.
- Fuel Starvation and Exhaustion.
- Fuel starvation (fuel on board the aircraft but not supplied to the
engine(s)) and fuel exhaustion (no fuel available on board the
aircraft) resulted in 47 percent of the engine power loss accidents.
This usually results from improper preflight planning or improper
fuel management procedures.
- Contamination continues to be a notable factor in fuel starvation
accidents. During this review period of the 1,230 engine power loss
accidents related to fuel system, fuel contamination was a cause in
381 or 31 percent of those accidents. Advisory Circular 20-43C,
Aircraft Fuel Control, contains valuable information that alerts the
aviation community to the possibility of inadvertent mixing or
contamination of turbine and piston fuel and provides recommended
- Fuel System Design.
Accidents have resulted because pilots and
maintenance personnel failed to become familiar with the different fuel
systems and operating procedures. Design changes, accomplished without
proper evaluation, the lack of standardization of controls configuration
among aircraft, plus the peculiarities in aircraft fuel system designs,
have contributed to power loss accidents.
The following are recommended operating practices that could help reduce
engine power loss accidents:
- Know the limitations of the aircraft and aircraft powerplant. Avoid
operating in excess of those limitations. Be sure all engine(s) are
within acceptable operating parameters prior to takeoff. Keep
proficient in all engine and systems operating procedures, including
emergency procedures. The aircraft flight manual or the rotorcraft
flight manual contain the normal and emergency procedures, and proper
power assurance check procedures. Use the checklist during normal and
- Follow the manufacturer's operating instructions. Have a qualified
person investigate all abnormal engine operating conditions (oil and
fuel consumption, low power, vibration, engine instrument readings,
- Positively utilize a powerplant and propeller maintenance program
which gives full consideration to the Federal Aviation Regulations
and manufacturer's recommendations.
- Keep abreast of technical information related to the aircraft fuel,
oil, parts, airworthiness directives, manufacturer's technical
- Know proper procedures when engine inlet or carburetor icing
conditions are encountered.
- Follow engine manufacturer's inspection procedures following
propeller strike or sudden engine stoppage.
- Operate engine controls smoothly, as abrupt movements can result in
engine malfunction and power loss.
- Avoid overspeed, overboost, and overheat.
- Do not fly an aircraft with known engine discrepancies.
- Fuel Management.
- In relation to airplane performance, the fuel quantity on board the
aircraft is only "time in your tanks." Management of that time should
rank high an the list of a pilot's priorities. Be fully familiar with
the aircraft fuel system and fuel management procedures.
- Make adequate preflight preparations to ensure that sufficient clean
fuel is on board the aircraft for the time to destination, plus an
adequate reserve, predicated on airplane performance.
- Know and understand the positions of the aircraft fuel selector
valves. Markings should be legible, valves should be easy and smooth
to operate and with positive detent action.
- Be familiar with the sequence for selecting fuel tanks of the
aircraft. The use of fuel from tank(s) other than as recommended
(especially during takeoff and landing) can result in eventual fuel
starvation. Many aircraft return unused fuel from the carburetor to
a tank. If the tank is full, the fuel goes overboard through the vent
and is lost, thus reducing range.
- A pilot should know the total USABLE fuel on board the aircraft
before flying. The UNUSABLE fuel should not be considered when
planning a flight.
- Make a visual inspection to assure that the fuel tanks are full. If
you are in the habit of flying with partial fuel loads, use positive
means to know the quantity of fuel on board the aircraft before
flight. Complete trust in fuel gauges has often resulted in fuel
depletion short of destination and accidents.
- Make a thorough fuel drain check of all sumps before flight. Consult
the owner's manual for proper procedures.
- During preflight inspection, determine that all tank vent openings are clear of obstructions.
- Check fuel flow from each tank to engine(s) prior to taxi. Remember
to allow sufficient time for this check as the carburetor and lines
hold fuel that would have to be used before you would know if there
was no fuel flow from a tank.
- Determine that hand primers are closed and locked in the detent
- Be fully familiar with fuel boost pump operating procedures.
- Before switching tanks, check the fuel quantity in the tank to be
selected and after moving the selector check the fuel selector
position to be sure proper tank is selected.
- After switching tanks, monitor the fuel pressure until you are sure
there is fuel flow from the tank.
- Maintenance should include inspection of fuel cells and tanks for
discrepancies such as collapse, contamination, vent obstruction,
internal damage, security, leaks, gauge accuracy, and general
- Periodically make a visual check of the fuel filter for condition
- Check operation and security of fuel selector and system control
handles and/or knobs.
- During maintenance, a detailed inspection should be made of fuel
quantity indicating system wiring, components, and calibration.
- Design changes and alterations to aircraft engines should be done
with approved data.
- Replacement of engine parts should be completed following
- Maintenance should be accomplished in accordance with the
- Have a qualified maintenance person dress out propeller blade nicks,
dents, scratches, etc., as necessary, to prevent fatigue cracks that
could cause propeller blade failure resulting in power loss. The
dressing of propeller blades should be done following the propeller
manufacturer's recommended procedures. Excessive dressing could alter
the airfoil shape of the propeller blades to the point where
propeller efficiency is lost, causing insufficient propeller thrust.
In the case of a twin engine aircraft that loss of thrust could
prevent the aircraft from maintaining flight with one engine
Through the individual and collective efforts of the aviation community, we
hope to eliminate factors that have caused engine power loss accidents. This
advisory circular is one of many efforts to try to reduce the "power loss"
type of accidents. The simple act of "keeping the engine running" could
appreciably reduce the number of accidents.
M. C. Beard
Director of Airworthiness
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