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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.

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44
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6answers
17k views

What are some of the differences between piston engines used in aircraft and automobiles?

What are some of the differences between piston engines used in aircraft and automobiles? It seems aircraft engines are much more expensive, I imagine some of that cost must be due to the more ...
44
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4answers
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Why do most radial engines use an odd number of cylinders?

To help suppress vibration, most 'V' and 'horizontal' engines use an even number of cylinders as closely opposed as possible. Radial engines are well known for excessive vibration. For some reason ...
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5answers
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Why are two-stroke engines nearly unheard of in aviation?

Almost all aircraft piston engines are four-stroke engines, with one power stroke per piston every other crankshaft revolution and a great deal of intricate moving parts which are only too happy to ...
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6answers
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Why is water-contaminated fuel bad, but water-injection is not?

A "wet" takeoff of a KC-135 with J57 engines—By USAF Photographer (USAF photo) [Public domain], via Wikimedia Commons Why is water-contaminated fuel bad, but water-injection is not? The way I ...
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What are the differences between fuel types (comparing with vehicles)?

I find it funny that at gas stations, generally you can purchase "regular" gasoline (in various octane levels) or diesel. At airports, generally you can purchase 100LL avgas or Jet-A. Can you compare ...
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9answers
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Why increase the number of cylinders in an engine instead of increasing their volume?

I've been reading about WW2 planes lately. Some of them have 12 or even more pistons in their engines. But if your goal is to increase power, why would you add more pistons instead of simply ...
34
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2answers
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How often should an engine be run, to stay mechanically sound?

It's winter time and many light aircraft are sitting idle. This can be detrimental to an engine's health. What is a good rule of thumb for how often a piston engine should be exercised, and for how ...
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14answers
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Why don't small planes use turbine (turboprop) engines?

Turboprop engines are more fuel efficient1, lighter for the same power, mechanically simpler and consequently more reliable. They are also slightly easier to operate (no need to fiddle with mixture) ...
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4answers
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Why isn't the APU a standard diesel generator?

Why isn't the APU a standard diesel generator? Jet-A and diesel are interchangeable (with the addition of a lubricant). So why not use a cheaper piston engine as opposed to a jet turbine? V.S.
29
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1answer
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What is the metal bit in the front of this propeller spinner?

What is that grey spirally bit in front of the propeller mounted on this Shvetsov ASh-62 radial engine?
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7answers
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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, ...
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3answers
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Why do aircraft piston engines consume so much oil?

This question is related to single/twin piston engine aircraft. After flying in a Cessna 152 and a Piper Dakota I have noticed that they both consume a lot of oil. Oil check is an integral part of the ...
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Why would a C150 tachometer bounce so much that the needle fell off?

On a long flight in a C150E, the tachometer started bouncing a little bit and the severity of the bouncing gradually increased until it was extreme: The tachometer was spinning in loops and making a ...
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3answers
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Why are propeller engines uncommon on airliners?

My experience in aviation is essentially zero, but looking at Wikipedia it seems like the Tu-95 Bear offers high subsonic speed and extreme range. I assume that turboprop engines are more fuel ...
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10answers
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Why do piston engines in aircraft burn fuel at a higher rate than a comparable car engine?

I've never understood why piston powered plane engines burn such a large amount of fuel per time period than car engines. Can anyone elaborate on this? I know that a C172M will burn ~5-9+ gph at ...
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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 ...
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2answers
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Why does the lack of a magneto affect engine RPM?

So I don't have my pilots licence, but I was part of the Australian Air Force Cadets for nearly 8 years (wonderful organisation). During this time I went on a number of flights in Cessna 172's and ...
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2answers
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What was the first aircraft that could fly inverted?

I'm taking a guess and assuming the Wright Flyer was incapable of flying upside down. I'm just guessing it probably lacked the power... ;) So what was the first plane that could fly inverted for a ...
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6answers
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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 ...
21
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3answers
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Why are piston engines for aircraft rarely diesel powered?

Why hasn't diesel caught on much for aircraft engines? The list of diesel aircraft engines on Wikipedia is very short. The reason I see mentioned is their poorer power-to-weight ratios. (e.g. What ...
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5answers
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Why are Inline Engines more commonly used than Radial Engines?

Back in the early days of aviation radial engines were very popular, it seemed like all of the big planes of the 20s, 30s and early 40s used them. But some time during WWII (or so it seems to me) ...
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3answers
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Why the lack of faster piston-powered planes?

There aren't very many fast piston airplanes in production. By "fast" I mean, if you look back in the early to mid 20th century, before turbines won out, there were lots of piston airplanes in ...
20
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2answers
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When is pre-heating a piston engine important, and how does one pre-heat correctly?

As temperatures here in New York plunge toward (and below) freezing it's time for those of us without nice heated hangars to start thinking about pre-heating our aircraft before we turn the key. ...
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5answers
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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 ...
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3answers
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How does the mixture of an engine affect the engine's operation?

I know that in most piston aircraft that there is a mixture control for the engine. My question is, how does the mixture control affect the engine's operation and what type of situations dictate a ...
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3answers
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Why do reciprocating aircraft engines have more than one spark plug?

Most reciprocating aircraft engines have two spark plugs per cylinder. What are the reasons for this?
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3answers
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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 ...
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4answers
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When to reduce power on takeoff (Cessna 182 or similar)?

There are two sides I've heard when taking off in a Cessna 182 or other small airplane with a normally aspirated engine driving a constant speed propeller: As soon as your wheels are off the ...
16
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3answers
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Why did the turbojet replace the piston engine?

Many people say that this was because aircraft powered by turbojet engines were faster during WWII. However the Grumman F7F-4N Tigercat, a fighter powered by a piston engine, flew at a maximum speed ...
16
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4answers
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Why does the Piper Cherokee (PA-28-140) engine have such low horsepower despite the very large displacement?

I'm sure this question could apply to many other plane engines, but specifically I'm looking at the Piper Cherokee PA-28-140. Surprisingly, it appears that the engine used, the Lycoming O-320, has ~...
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2answers
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Is there any legitimate reason for adding momentary power when descending at idle with full carburettor heat on?

Scenario: While demonstrating a simulated engine failure emergency landing a flight instructor puts on carburettor heat and reduces the throttle to idle of a small single engine Cessna. After a couple ...
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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 ...
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2answers
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Why is the magneto drop check done at 1700 RPM?

In our Cessna 152, we carry out the mag drop check at 1700 RPM, following the POH. My question is why it is done at 1700 RPM? What will happen If I check it at 2000 RPM or less than 1700 RPM? And if I ...
16
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2answers
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Why did the manifold pressure gauge on the Ki-61 have negative values?

The manifold pressure gauge of the Japanese Ki-61 has values which go from +40 to -40. I know this has to be relative to something since negative pressure can't exist (you can't get more vacuum than a ...
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3answers
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Rotax engines have no mixture control, how do they handle less dense air?

Rotax engines have no mixture control, yet they don't seem to have any more problems than other engines at altitude. How do they handle the lower air density in order to not get a too rich a mixture?
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2answers
4k views

What causes a run-away propeller?

I've never understood this, why can't you just idle the engine and let it slow down?
14
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6answers
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Why are propeller airplanes still made?

Airplanes with propellers were invented a long time ago. After that, jet engines came into existence. My question is: why do we still have propeller engines? The reasons I can think of are: They are ...
14
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3answers
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What does feathering mean and how does it work technically?

Before I ask "What does Feathering mean when it comes to Jet/Propeller Engines" I have to say what I think I know: Feathering jet/prop engines mean achieving a sufficient turbine rotation speed at ...
14
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3answers
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What is a biplane propeller and how efficient is it?

Lazair ultralight series II used biplane props to absorb more power from the engine....so my question is what really is a biplane propeller and are they efficient in comparison to a four bladed prop?
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1answer
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How does carb heat increase the risk of dirt ingestion?

In this question about turning off carb heat just before landing, one of the justifications for doing so is to reduce the likelihood of ingesting dirt into the engine. How does carb heat (or the lack ...
14
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1answer
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What is this aircraft that has both piston and jet engines?

A friend sent me this picture of a trimotor aircraft with what looks like two radial engines and a jet in the middle. He didn't know what is was and neither do I. Anyone recognize it?
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Why are piston engines so unreliable in airliners?

Before the first jetliners appeared, all airliners used piston (reciprocating) engines, which were astoundingly prone to failing in flight, to the point where an inflight engine failure was an ...
13
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2answers
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Why/How does a “Powerflow” exhaust increase horsepower?

I've seen airplanes (typically Cessna 172s) with a "Powerflow" exhaust system and then claim to get several more horsepower, resulting in faster cruise speeds. How does a Powerflow exhaust work, and ...
13
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3answers
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Why is carburetor heat use discouraged on the ground?

I've been reading my private pilot books for when I start in February and Carb Heat has me stuck in a rut. I feel like I need to have a very solid understanding of this being that I live in a very ...
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4answers
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Should I have carb heat on for landing in a C152?

There is quite a debate about this! I'm a student, have gone solo. My first instructor insists the carb heat goes off/COLD on the approach ('ready for go-around' if needs must! And to prevent dirty ...
13
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1answer
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Why does manifold pressure increase when you turn on carb heat?

So everyone knows that carb heat decreases engine performance. Yet when we check the heat during run-up, the manifold pressure increases. Why is that? Shouldn't adding carb heat cause the intake air ...
12
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2answers
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What is the difference between SMOH and SFOH?

When looking at aircraft for purchase online, a lot of acronyms are used. In particular, the SMOH and SFOH acronyms are thrown around a lot for used aircraft. What are the differences between these ...
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4answers
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Why does carburetor icing require manual attention by the pilot?

Why is it carburetor icing has to be handled manually by the pilot, at least in a helicopter? I am hoping very soon to take my PL/H lessons, I have a little understanding of mechanics and how things ...
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2answers
922 views

Is the Soloy Dual Pac recognised as two engines or one engine?

The Soloy Dual Pac apparently allows two engines to rotate one propeller -- here's a picture of it on an Otter: Is this recognised as a centreline thrust twin engine aircraft, a "standard" twin ...
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2answers
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To a pilot, does turbocharging differ from supercharging?

When it comes to operating an aircraft, what are the practical differences between a turbocharged engine and a supercharged engine? I'm aware of the mechanics - turbochargers being exhaust-driven, ...