Operations
10 Reasons Engine Failures Occur
1, Fuel starvation i.e. pilot neglect or error
2. Induction system i.e. maintenance or preflight neglect
3. Ignition system i.e. plugs or magnetos
4. Miscellaneous maintenance i.e. nut missing
5. Cylinder valve failure i.e. improper leaning
6. Fuel system operation i.e. selector to off
7. Carburetor ice i.e. failure to apply until late
8. Fuel contamination i.e. water and such…
9. Inadequate lubrication i.e. pilot neglect or error.
10. Major internal failure i.e. metal fatigue.
The Engine
The four-stroke/cycle engine was invented by N.A. Otto in 1876. His engine operated by having a piston sliding in a cylinder. The piston has a connecting rod fastened inside the piston and extending to a crankshaft which in an airplane has the propeller on one end. The reciprocating motion of the piston is changed into the rotation of the propeller. The aircraft engine develops full power for 90% of 2000 hours during which the comparable life of an automobile engine is developing 20% power for slightly over 100,000 miles. Most propellers have from 50 to 87% effective thrust.
The four cycles of the piston are timed to the opening and closing of valves with the spark to a sparkplug. The first stroke draws fuel through the open intake valve, the second stroke closes the valve and compresses the fuel to make it volatile. The explosion of the fuel on the piston head gives the engine its power. The fourth stroke gets rid of the residue of the explosion and is called the exhaust stroke.
All the letters and numbers of an aircraft engine tell the significant things about the engine. An "I" in its title shows that the engine has a fuel injection instead of a carburetor fuel system. O says that the engine is a horizontal opposed with the cylinders flat and in pairs opposite to each other. The number following the 0 is the total piston displacement volume in cubic inches. Different aircraft engine manufacturers have different lettering and numbering systems.
Single-engine planes have two to five degrees of downward tilt to the engine from the horizontal. This is the reason the rudder is the first positive control during takeoff. This also keeps the propwash away from the horizontal-tail and reduces the pitch changes that occur from power changes. This also serves to reduce the noise of singles when compared to twins.
There are several ways to learn about how engines operate. There are videos, reading, and actual taking apart a small engine. Visit a maintenance show where the engine is opened up so you can see the parts and get an idea of what the insides look like. Los Banos has such a shop.
Lycoming Model Codes for Reciprocating Engines
Each engine designation is made up of a prefix of a series of letters, a three-digit number and a suffix, which combines letters, and numbers. Some examples:
TO 360 C1A6D
IO 540 AA1A5
IO 360 A3B6D
PREFIX DISPLACEMENT SUFFIX
L - Left-hand rotation Cubic-Inches A - Power Section & Rating
crankshaft or
AA
T - Turbocharged
(exhaust gas driven) 3 - Nose Section
I - Fuel Injected B - Accessory Section
G - Geared (reduction gear) 6 - Counterweight
Application
S - Supercharged (mechanical)
D - Dual Magneto
V - Vertical Helicopter
A - Aerobatic
AE - Aerobatic Engine
O - Opposed Cylinders
Rethinking Engine Operation
BFC-Brake Specific Fuel Consumption a measure of fuel economy
CHT Cylinder Head Temperature hottest to the rich side of peak.
ICP Internal Cylinder Pressure highest pressure near CHT peak. Sets engine temperatures.
EGT Exhaust Gas Temperature gauge is rich-peak-lean as fuel/air proportions set.
POH Pilots Operating Handbook is a frequently not a consumer oriented source of engine operation.
--Common EGT setting 50-degrees on rich side of peak (ROP) is a compromise of efficiency and power.
--Best power occurs 125 degrees on rich side of peak. Excess fuel cools engine. Uses more fuel.
--Lean Side of Peak (LOP) flown with a cooler engine and no damage, less fuel, less power and fly further.
–It will cost you money to get the exact leaning numbers for your engine
Squared Power Settings
---25 inches at 25000 rpm is a fallacy in power management
---Radial engines can be damaged at high manifold pressures and low rpm
---Lindbergh taught
Range was increased from 500 to 950 miles. That's how we shot down Yamamoto.
---Unable to get a security clearance due to his forecasting a German victory before
combat missions in the Pacific as a manufacturer's representative.
---Use the POH numbers and you will find the may over-square settings are acceptable.
---Over-square has FAA approval as written in Accident Prevention Publication 87-40-28
---FAA says set power for smooth running and low noise.
---General rule is that low rpm causes less vibration, noise, heat, and wear.
---Longer engine life is sure to follow.
---Best operation will vary from aircraft and engines
---Exception apply to takeoff, engine break-in with high rpm required.
Getting Old
Engines deteriorate slowly and deceptively. The trouble will be structural due to excessive temperature or operational in one of the four operational systems; ignition, lubrication, carburetor, or cooling. 22% of aircraft accidents are the result of engine failure. Only 10% are due to mechanical failures. Of these 4% is only a partial loss of power. 12% are the result of running out of fuel to the engine and carburetor ice.
--Know what normal is.
--Is something not right?
--How is control response?
--Can the malfunction be corrected from the cockpit?
Engine Systems
Ignition
Carburation
Fuel
Lubrication
At 2400 rpm
piston up/down 40 times second
valves open/close 20 time second
sparkplug fires 20 times second
In an hour
Crankshaft 144,000 revolutions
Pistons reverse direction 288,000 times
In 1800 hours (engine life) propeller will turn 259,200,000 times
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