Questions tagged [piston-engine]

Piston (reciprocating) aircraft engines are internal combustion engines, similar to the type found in most automobiles. They are typically gasoline powered.

Piston aircraft engines are reciprocating internal combustion engines, similar to the type found most automobiles, which are used as powerplants in some aircraft, generally driving a propeller either directly or through a reduction-drive gearbox.

These engines are typically gasoline-powered, burning some form of AvGas or automotive gasoline, though some aircraft diesel engines exist, which can burn diesel fuel or jet fuel.

The first successful powered aircraft all used piston engines, which remained ubiquitous on aircraft of all sizes through the early-to-mid-1950s. However, the first workable s were built and placed into military service during World War II, and the raw speed of jets and their ability to use practically any combustible liquid as led them to quickly eclipse piston engines in aircraft (with s following soon afterward). The first (the ) entered commercial service in 1952, and the first widely-successful jetliner (the ) carried its first paying passengers in 1958; the large piston-engined airliners of the 1940s and 1950s, such as the , , and , fell almost entirely out of frontline passenger service by the end of the 1960s. Even for small, short-haul aircraft (where a jet's high speed provides little advantage, and its high fuel consumption provides a considerable disadvantage), piston engines were progressively replaced by s, due to the latter's vastly-higher (large piston engines, with their many cylinders, valves, pistons, sparkplugs, etc., are notoriously prone to suffering s) and their ability to run on the same fuels used for large jet aircraft. Since at least 1970, the main niche for piston engines in aviation has been small aircraft, as small piston engines are much more reliable than their larger counterparts, and turbine engines scale down poorly to very small sizes.

Other powerplant types include:

  • - a turbine engine driving a propeller.
  • - a turbine engine producing thrust directly
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How can reducing power too quickly on a piston engine damage it?

In many places, it's been stated that you should reduce power slowly to prevent engine damage. Depending on who you talk to, some say you should reduce the manifold pressure by 1 inch per minute, others say two. However, I'm not sure just how…
Qantas 94 Heavy
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Why should some piston engines not be run lean of peak?

Leaving aside the claimed pros and cons of lean-of-peak (LOP) vs. rich-of-peak (ROP), the C172S Lycoming IO-360-L2A handbook I have says "Continuous operation at mixture settings lean of peak EGT is prohibited", and indeed I was always taught to run…
Pondlife
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Why does manifold pressure increase with power?

Whilst writing an answer to this question, I remembered something I don't really understand. The partial vacuum in the inlet manifold is caused by the piston descending with the inlet valve open during the "suck" phase of the Otto cycle. It is this…
Simon
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What is "detonation" in a piston engine?

Recently, I saw this question, which included a rather alarming quote: Full throttle operation with carburetor heat on can cause detonation. Woah! That doesn't sound good. In fact, I would have figured aviation engine manufacturers would have…
raptortech97
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Why cycle the magnetos before engine shutdown?

Inspired by this question asking about shutting down a light aircraft engine I realised there is another ritual which I do, but have long forgotten the reason why. Having parked a light aircraft, and switched off the electrics, with the engine still…
Jamiec
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What are the advantages/disadvantages of diesel/Jet A-1 piston engine?

Some GA aircraft, notably the DA40/DA42, are equipped with piston engines that use Jet A-1 and/or automotive-grade diesel instead of aviation gas (avgas). An example of such engine is the Austro Engine AE300: What are the advantages/disadvantages…
abey
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What are the differences between Lycoming and Continental engine designs?

Inspired by a discussion in chat. Most GA piston singles are powered by either Lycoming or Continental engines. The engine designs used by both manufacturers are broadly similar (4-cycle, horizontally-opposed, gasoline-powered, air-cooled), and…
voretaq7
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Why do the Lycoming HIO-360 A1A and IO-360 engines produce different power?

I have just acquired an aerobatic aircraft fitted with a Lycoming HIO-360 A1A. Reading the specs on the engine I see it has the higher (8.7:1) compression of the 200hp IO-360 engines, which seem mainly to make that power at 2 700 rpm, but this one…
Ron Wheeldon
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Why are updraft carburetors standard in aviation?

My only detailed experience with carburetors is in aircraft. I'm pretty familiar with the principles behind float-type carbs, but I recently saw a schematic for a "downdraft carburetor" with a choke valve. This got me curious, so I did a little…
egid
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Why did the Daimler-Benz DB 605 compression ratio vary between cylinder banks?

The Daimler-Benz DB 605 was an inverted V12. The compression ratio of the 2 banks varied slightly. Why did the designers do this? Compression ratio: 1:7.3 right bank, 1:7.5 left bank (museomotori.unipa.it)
Brinn Belyea
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In a piston aircraft engine, how much heat must be removed by the oil cooler?

It is pretty straightforward to compute the heat and power generated by the combustion process, given the displacement, RPM and fuel mass flow rate. Similarly, the power exhausted can be computed with knowledge of EGT and conservation of mass. The…
user34656
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Why is a feather check performed on a piston engine and how much RPM drop should be allowed?

Light general aviation piston twins have full-feathering props. It's normal to perform feathering checks by pulling the prop level all the way down to feather, briefly, and observing the changes. First, why is the feather check performed and what is…
ryan1618
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Can I use motor oil in a aircraft piston engine?

In one episode of the 'reality' show Airplane Repo a pilot topped off an aircraft engine with motor oil; I think it was a Cessna 182 but I may be wrong. What would be the effect on the engine? Is it a practical (and safe) alternative if aviation oil…
Pondlife
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Why in the Seneca 2 the Rated Horsepower are higher at 12000 feet than at sea level? (215Hp at 12000feet, 200Hp at sea level)

Reading the POH I found that the Rated Horsepower at 12000 Feet are higher compare to sea level. I have in the past studied the back pressure of the exhaust gasses but I cannot completely understand how it works.
Andrea Ghilardi
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Does engine oil have a shelf life?

Suppose that I buy a case of oil. For some reason I stop flying and the oil sits in storage for a sufficiently long time. After that, I decide I want to put it in my engine. Is there a point after which (reciprocating) engine oil should no longer…
Steve V.
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