Piston Aircraft Engine - Different flight conditions can cause the cylinder head temperature to rise or fall. For example, a prolonged climb at a high power setting can cause the engine temperature to increase and the attitude of the aircraft during the climb may be such that the air cooling is insufficient to keep the cylinder head temperature in the normal operating range.
In this instance the climb attitude should be reduced until the temperatures are back in the green band. Alternatively, a step climb could be adopted with periods of level flight to keep the temperatures down. The most reliable piston engines and the most reliable turboprop
Piston Aircraft Engine
engines are those that are properly managed as the complex and expensive equipment that they are. While piston engines have a greater number of direct wear parts, it is generally simpler and less expensive to service those wear parts.
Pistons Vs Turboprops Expense
It speaks volumes when Van's completions last year outnumbered the top 3 GA sellers... combined. Despite being great airplanes, the average weekend pilot can no longer afford/justify the cost of a new Piper or Cessna. It's great that the experimental category offers another alternative in the US.
Aircraft engines are, relative to the cost of them associated airframes, expensive; turboprops are certainly no exception. But the cost goes beyond the initial purchase price of the engine and its accessories, and extends to include maintenance issues
that occurs over the life of the engine. Amortizing the cost of a small PT6A with a $700,000 purchase price over a 3,600 hour TBO yields ~$195/hour, while an overhaul costing $250,000 costs ~$70/hour. With proper engine management and inspections, if this is extended to 8,000 hours, this cost drops further to ~$31/hour.
The EGT is hotter at leaner mixtures which indicates a more efficient combustion process where less unburnt fuel exits the cylinders through the exhaust system. During cruise the mixture is leaned using the EGT gauge by reducing the mixture to a point where EGT peaks and then enriching slightly to reduce the temperature in accordance with the aircraft flight manual.
Fuel Pressure
It is advantageous to lean the mixture in the cruise as this reduces the fuel consumption and allows the engine to operate at its most efficient state. Fuel is stored in tanks (usually in the wings) and must be delivered to the engine during operation.
The fuel is pumped (or gravity fed) under pressure from the tanks to the engine. It is important for the pilot to monitor the fuel pressure to ensure that a continuous stream of fuel is being supplied to the engine.
Fuel delivery is such a critical system that aircraft which require a pump to transport the fuel from the tanks to the engine are fitted with a backup pump system in the event that the primary pump fails.
If the fuel pressure begins to drop during flight, the backup pump can be used to increase the pressure. The backup pump is also usually activated during critical phases of flight such as take-off and landing to add some redundancy to the system and reduce the chance of an engine failure.
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While general aviation aircraft sales were down in 2020 — due to the pandemic — almost 2,400 aircraft were delivered during the year, according to the latest statistics from the General Aviation Manufacturers Association. That number includes 1,312 piston airplanes, by far the largest category of aircraft delivered.
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This site also participates in other affiliate programs and is compensated for referring traffic and business to these companies. A well-known aircraft, the Piper PA-44 Seminole has continued to prove its reliability and durability over the years.
And although this is one of the slowest out of the fastest twin-piston aircraft we'll see here, it won't let you down. Take a close look along the length of a propeller, from the tip towards the spinner, and you will likely notice that it looks like the propeller twists.
Common Faults After Engine Start
This twist along each propeller blade is, too... In typical aircraft engines, each of the engine cycles occur on a separate stroke or rotation of the engine. This sequence is mechanically controlled by a camshaft that actuates the valves
at the top of each cylinder allowing the fuel/air mixture to enter the cylinder and be subsequently exhausted. The image below is an extract from a Cessna 210 Pilot Operating Handbook where various acceptable engine speed and manifold pressure combinations are given for a flight conducted at 10,000 ft.
As an example, a pilot may choose to fly at an engine speed and manifold setting of 2400 rpm @ 20'' which should produce a true airspeed (TAS) of 171 mph burning 74 lbs/hr of fuel, or alternatively at a higher power
setting of 2550 rpm @ 21'' which will result in a TAS of 187 mph but will burn 87 lbs/hr. With speed comes the responsibility of fuel usage, and this aircraft only burns 22.4 gallons per hour at 75% cruise speed.
Common Faults During Engine Start
This has proven that the Piper PA44 Seminole offers extra speed for the same fuel usage. The Cessna 182 Turbo has a critical altitude of 20,000 feet, the same as its service ceiling, the Cessna T206H Turbo Stationair maintains sea level power to 16,000 feet while its service ceiling is FL240, and the Beechcraft Baron BE58TC has a critical altitude of approximately FL180
with a service ceiling of FL250. Once the engine has started it is important to check that the oil pressure rises within 30 seconds of the start. A low oil pressure could indicate that the oil pump has failed which could result in the engine seizing due to insufficient lubrication.
In this case the engine should be shut down immediately. However, the M500 claims a 50 knot improvement on cruise speed. In essence turboprop engines do not radically improve takeoff distances for equal power outputs, as the
propeller is still transmitting the same output to the surrounding air. The tachometer is color-coded to indicate the operating limitations of the engine. The normal operating limit is always colored green, while maximum operating speeds are colored red.
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Some instruments also have a yellow band which indicates a precautionary range; here the engine should only be operated for a short period (typically 5 min) before resuming operation in the green band. This thermodynamic reality has driven aircraft designers towards selecting turboprop engines for
single engine aircraft beginning in the 5,000 lb to 6,000 lb max takeoff weight range, as below this weight, 350 HP to 400 HP engines are sufficiently powerful to achieve sufficient takeoff and climb performance while remaining more
efficient than small turboprops. For example, the Cessna Caravan with the 675 horsepower PT6A and the Caravan EX with the 867 horsepower PT6A both have critical altitudes in the 7,000 foot to 8,000 foot range depending on temperature, but the Caravan EX
will climb well above the 675 Caravan and will maintain better airspeeds at higher altitudes as a result of the raw power improvement. Get the 23 resources I wish I had at the start of my aviation journey in an easy-to-reference PDF.
Rough Running Due To Fuel Starvation
Nearly all of the topics I most commonly get asked about flight training, all in one place, for free. What is supposed to be classified as a 200-knot aircraft, its maximum speed is 192 knots. But when being tested on cruise performance, it proved to be at its most efficient at about 100 knots, where only 3.6 gallons per hour of fuel was being consumed.
If the oil temperature or pressure is outside of the normal operating range, there is likely a problem with the engine's lubrication system. This is a potentially serious condition and so the best course of action is usually to land immediately at the nearest airfield where the issue can be addressed safely on the ground.
Most aircraft engines require priming before starting. This involves spraying fuel into the induction system of the engine close to the inlet valve. This additional fuel serves to enrich the mixture during the start process which helps the engine to fire and run smoothly as it starts.
Many aircraft have a dedicated engine primer, usually located near the throttle and mixture controls. Using this primer ensures that additional fuel enters the engine when and where it is required. The oil passing through the engine heats up rapidly due to the high temperatures in the engine.
Cylinder Head Temperature
This increase in oil temperature causes a reduction in the viscosity of the oil which means that the oil is able to flow more easily but loses some of its lubricating ability. For proper engine operation the oil must be kept within a certain viscosity range which corresponds to a particular temperature band.
Aircraft lubrication systems are fitted with an oil cooler, located upstream of the oil pump but downstream of the engine. Hot oil flows through the cooler, reducing the temperature of the oil before it re-enters the engine.
The oil temperature gauge is most often fitted between the cooler and the engine and thus provides a measure of the temperature of the oil before entering the engine. Starting an aircraft engine can sometimes be tricky - especially on a cold day or if the engine hasn't run in a while.
Let's look at some of the more common issues seen during start up. New piston engines range in cost from $25,000 for small four cylinder engines to more than $100,000 for large six cylinder engines such as the Continental TSIO-550.
Magneto Faults
The Pratt and Whitney PT6A series engines cost a minimum of $700,000 and easily exceed $1,000,000 for larger variants. A rough running engine could be an indication that the incorrect mixture setting has been applied to the engine as the engine is not receiving the correct ratio of fuel to air.
Alternatively, it could also indicate that a blockage exists between the fuel tank and the intake of the engine or that the fuel pump is not providing adequate pressure. The first step to troubleshoot a rough running engine is to select another tank to run off – if the problem then goes away you will know that the fault lies between that tank and the inlet manifold.
You can also engage the auxiliary or backup fuel pump to see if that corrects the issue. If this improves the running of the engine, then this indicates a fault in the mechanical fuel pump. The temperature in the engine is measured by a thermocouple located in the head of the hottest cylinder and displayed on the Cylinder Head Temperature (CHT) gauge in the cockpit.
This provides a direct and immediate indication of the temperature inside the engine, which must remain within a particular band during all stages of flight. The Tecnam P2012 Traveler was the first twin-piston aircraft that had electronic management of engine power, which would obviously make the pilot's job a lot easier.
Turboprop Conversions
With a max speed of 194 knots, this aircraft can comfortably get passengers to their destination. It is worth noting that typical turboprop certification does not provide credit for reverse thrust, only "beta" that is a propeller that
achieves neutral thrust output by moving the blades to be perpendicular to the incoming flow. Use of full reverse may further improve this distance, in the practical world. Cranking the engine puts a large load on the starter motor which could overheat if used for periods longer than 20 seconds.
If you are struggling to start the engine you may need to wait a minute or two between starting attempts to allow the starter motor to cool. As the engine fires you should advance the mixture lever forward to ensure continued delivery of fuel to the engine.
In the 50s and 60s, most pilots went over and above their private licensing and got their twin-engine ratings. The reason for this was that many WWII pilots had much preferred flying multi-engined aircraft. This created an already waiting market for new twin-piston aircraft that was bound to come.
How Do Piston Engines And Turboprop Engines Work?
The Piper Seneca is best known as an aircraft that is suitable for pilots who are just moving over to twin-piston aircraft. Its design makes it easier for pilots to make the change from almost any other single-piston Piper aircraft.
Comparing Piper's M350 and M500, which are similar airframes, the M350 with a Lycoming TIO-540 and the M500 with a PT6A-42A, reveals a 700 pound weight increase on the M500. The claimed takeoff performance for the M500 shows a 350 foot increase in takeoff distance.
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