Pros and cons of engine types?

[Skyguns MKII]

Going to school for my FAA certificate and though I know the basics I still have the "gotta know it all" feeling. SO! pros and cons of the following

opposed
V block
In-line
reciprocating

[earl1937]

Going to school for my FAA certificate and though I know the basics I still have the "gotta know it all" feeling. SO! pros and cons of the following

opposed
V block
In-line
reciprocating

Not quite sure what your question is regarding your list of engines, but assuming they are asking you to evaluate each of the engines, here is my comment:

#1- Opposed engines are engines which have there cylinders on opposite sides of the crankcase and is the engine of choice of many manufactors of light aircraft such as Cessna, Piper and Beechcraft-Raytron. First appeared on the aviation sence in the forties, with the Cessna 120, Luschome 8A, Ercoupe, Stinson, Taylorcraft and probaley some others that I have forgotten about. Good reliable engine, no heat problems that I ever heard about with would warrant an AD from the FAA.

#2- There were a couple of different aircraft which tried the V-block engine, such as those in a car, but because of weight, due to liquid cooling and weight of the engine, as far as I know, neither one ever went to production.

#3- Inline engines have a long history in aviation, starting back in the mid or early 1900's, used almost on ever aircraft in WW1 and the in-line design went on to power a whole host of aircraft, Fairchild PT-19', 26's, P-51's, Spitfires and some of the Geman and Japanese aircraft also used the inline engine. Some were cooled in flight with a coolant liquid, and some were cooled with forced air thur the cylinder arrangement. Top end speed with the in-lines were good to excellent, but not much climbing power when pitted against the more powerful Radial engines.

#4- Radial engines are probabley the best all around design for a number of reasons. Power output vs weight, ease of cooling, simple design, ease of maintaince. Untill the on slaught of jet engines, ever aircraft which carried more than 3 people, since the late 30's, were powered with Radial engines, the smallest being a "Kinner", 5 cylinder on the PT-22 Rayans which trained a lot of pilots in the 30's and 40's to the biggest radial ever built, the Pratt & Whitney R-4360 engine which powered the giant B-36, XC-99, Boeing 377 Stratocruisers which the airlines used, the KC-97's, B-50's just to list a few of the aircraft which used this engine. Serveral of these aircraft had heat problems with the rear bank of cylinders, such as the B-36, B-29, B-50 and the Boeing 377. Even the Lockheed 1049G "Constellation", i.e. C-69 had cooling problems.

A opposed engine.

 A inline, inverted engine.

The largest radial engine ever mass produced, had 28 total cylinders, arranged in 4 banks of 7 cylinders in each bank.

I hope this might of help to you, if not, be more specific about your question and I might could help you!  

[Fish42]

#2- There were a couple of different aircraft which tried the V-block engine, such as those in a car, but because of weight, due to liquid cooling and weight of the engine, as far as I know, neither one ever went to production.

Except all those aircraft that did use V-blocks, because they give the same power but in a much shorter design.

Spitfires, Mustangs, Hurricanes, 109s, Yak 9, Pe-2, Mig 7, Beaufighter, Hawker Tempest, Bf110, He111 etc. The air in WW2 was full of V12s.

#3- Inline engines have a long history in aviation, starting back in the mid or early 1900's, used almost on ever aircraft in WW1 and the in-line design went on to power a whole host of aircraft, Fairchild PT-19', 26's, P-51's, Spitfires and some of the Geman and Japanese aircraft also used the inline engine. Some were cooled in flight with a coolant liquid, and some were cooled with forced air thur the cylinder arrangement. Top end speed with the in-lines were good to excellent, but not much climbing power when pitted against the more powerful Radial engines.

Most WW1 aircraft used the Rotary Engine.

Inline motors work just as well as a V but as the motor gets longer (More/larger cylinders), the strain on the Crank gets a lot higher. You then have to bulk it up which in turn saps some of the power gained. V-blocks keep the run shorter which reduces the spinning mass of the motor.

[Ardy123]

What was the advantage to having an inverted V design?

[Fish42]

What was the advantage to having an inverted V design?

It allowed better views for single seat fighters of the time.

[nrshida]

The question is a bit vague, but some issues are addressed in what has become the following wall of text. Hope it's useful.

There's a little ambiguity in the world of aircraft about what an inline engine is as the term seems to be interchanged quite freely with V engines. The history of this might be to distinguish them from radial engines, while in the automotive industry they are distinctly different things. A V engine has essentially two banks of inline engines sharing a common crankshaft.

One thing you notice about many V engines is that the same angle keeps suspiciously popping up. The Rolls Royce Merlin and the Griffon, the Allison V-1710, Daimler-Benz DB 601 and 605 and many others all use a 60° angle between the banks. This is not insignificant, for a V12 engine the 60° bank gives a theoretically perfect primary and secondary balance: in other words the reciprocation of the pisons, con rods and the rotation of the crank cancel each other out harmoniously (A straight six also has this attribute and many WWI aircraft employed this format). This is a very different situation from a (Ford, I think it is) 90° V8 with a flat plane crank which produces a vertical oscillation twice the frequency of the revolutions, so the engine literally wants to bob up and down in its mountings. This has an obvious advantage in terms of reducing vibration and stress on the engine, and hence increasing reliability.

One restriction of  the 60° bank is that it does limit the space available for the fuelling system. This is why many Ferarri engines have a bank of 72°, the needs to improve aspiration overode the balance issue.

Additionally regarding perfect primary and secondary balance with twelve cylinder engines, there is another bank angle which also has this benefit: 180°. The Hawker Typhoon and Tempest essentially have two 180° V12s on top of each other in a shared casing. These engines are called horizontally opposed engines but not necessarily boxer engines. The way to distinguish is that in V engines (of any angle) two connecting rods typically share a big end bearing while in a true boxer engine each connecting rod has its own bearing.

Any boxer engine with six cylinders or more will also have perfect primary and secondary balance (VW Beetle for example does not, it has the same secondary balance characteristics as an inline 4). Many post war civil aircraft use a six cylinder boxer unit, which has an additional advantage regarding cooling which we will address later. Porsche has stood by the boxer engine from the first 356 right through all models of 911 and many of their racing cars including their 8-cylinder Grand Prix cars, however an interesting example is the vaunted Porsche 917 which in fact employed an air-ccoled 180° V12 and NOT a boxer engine.

This brings us to another interesting point about engines: positive net torque output. If you imagine a cyclist doing his thing, only part of the revolution of his pedals is delivering torque to the bicycle (and hence the road). As his pedal comes over the top only at about 20 degrees or so does the lever of the crank begin to deliver rotational force, at the top and bottom of the pedal rotation and all the way back up there is no positive torgque contribution, infact a negative or a subtraction from the torque is the situation. Only the momentum of the crank and his other leg keeps the whole thing rotating smoothly.

With a four-stroke engine this positive and negative torque is exasperated because each piston is only making a power stroke every other rotation. The magic number with piston engines is 7. 7 pistons never have a negative torque phase and are thus always making positive torque. Although a six cylinder engine comes very close!

All of the aircraft in Aces High have a positive torque output (including the Storch) but again consider what more firing strokes means. At low altitudes the Nakajima Homare engine with a displacement of only 32 litres and two valves per cylinder nearly matches the output of the Daimler Benz DB605 with over 35 litres of displacement and four valves per cylinder (and a superior supercharger). The 18 cylinder engine simply has 50% more power pulses per 720 degrees of revolution this explains the outputs (here is another difference between air and liquid-cooling: it is very difficult to employ a 4-valce head with an air-cooled engine and a bigger valve area makes for a more efficient output. This also weighs into the selection).

This brings us to a discussion about engine cooling. Of course a radial lends itself very well to air cooling while an inline or V engine does not. There is some merit to the famous quote that a liquid-cooled aircraft engine makes as much sense as an air-cooled submarine however it is not as simple as that. In a dive an air-cooled radial engine can actually become over-cooled which leads to temporary fuelling problems.

The biggest penalty for liquid cooling is of course the radiator which can produce an awful lot of drag. Arguably the P-51D had the best wartime solution for this in single engine aircraft. With a twin engine such as the Mosquito or the Whirlwind you have the opportunity to nest the rads in the inner wing section which is as close to an optimal solution you can find. This opportunity was missed by the Me410 design team who essentialy doubled the drag of a single engined fighter's radiators!

Many modern civil piston craft use a boxer-six which has many advantages of both the radial (air-cooled, good access) and of the V / inline: perfect primary and secondary balance.

In the end all design solutions have compromises and especially with aircraft it is often only at the flight testing phase that the true measure of the design as a holistic entity announces. The relative advantages and disadvantages of the different formats are core to these design choices.

In closing there are two interesting aircraft which switched between air-cooled radials and liquid-cooled V engines throughout their production run:

The Fw190 started as an air-cooled radial and employed a liquid-cooled V12 in the later stages of its development and the Ki-61 did the opposite, being adapted to carry a radial when the supply of V12s ran out!

[Charge]

"This opportunity was missed by the Me410 design team who essentialy doubled the drag of a single engined fighter's radiators!"

Not really. Two engines, two radiators, the Mossie and Whirlie had two radiators as well, there is no way around the required cooling area, unless you use higher engine temperatures to make a smaller radiator more efficient which to my knowledge Merlin did not use but DB did. The 410 used the standard MT recessed radiator design and not the much draggier surface mounted design e.g. Spitty used.

http://109lair.hobbyvista.com/techref/systems/cooling/f_flaps.htm

http://www.britmodeller.com/forums/index.php?/topic/234907504-messerschmitt-me-410-hornisse-hornet/

-C+

[Debrody]

What was the advantage to having an inverted V design?

There was enough space for the cowl guns.

Also, Fish, most of the the Tempests had a H engine (Napier Sabre), as far as i know. Some had Bistrol Centaurus radials though.

[colmbo]

Power to weight, reliability and simplicity of operation make the turbine a clear winner.  Engage starter, fuel condition lever forward at specified percentage of rpm and Whoomp the turbine is running.


But for manly man airplanes you want a radial.  Crack the throttle, engage  starter and count 6 blades, primer on for 3 more blades where the mags are switched on.  3 more blades and she fires Bark, snort, cough...great clouds of smokr.  Keep tickling the primer as you move the mixture to auto rich ( using your third arm) and if you did things right she continue to run.

Jets (turbines) are for kids.

[earl1937]

Except all those aircraft that did use V-blocks, because they give the same power but in a much shorter design.

Spitfires, Mustangs, Hurricanes, 109s, Yak 9, Pe-2, Mig 7, Beaufighter, Hawker Tempest, Bf110, He111 etc. The air in WW2 was full of V12s.

Most WW1 aircraft used the Rotary Engine.

Inline motors work just as well as a V but as the motor gets longer (More/larger cylinders), the strain on the Crank gets a lot higher. You then have to bulk it up which in turn saps some of the power gained. V-blocks keep the run shorter which reduces the spinning mass of the motor.

Not for sure what the questions are that the FAA test requires, but from what I understand, the V block engine was about automobile type engines and how they would work in aircraft. That is why I did not include all the V-block engines of WW2 era. I wish he would be more specific, then I am sure someone could answer him with something that would help.
I am certainly no expert on WW1 aircraft and engines, but, the air war was not dominated by the rotary engine.
The albatross D.I. was one of the best German and Austrian air force aircraft of the last two years of the war and was powered by a 6 cylinder, in line, water cooled engine. The Nieuport16, was a French built aircraft which did use a rotary engine, The Curtiss Jenny trainer had a 8 cylinder V-block engine.
A lot of experts which have made statements as to the best fighter of WW1, say that the German Fokker D.V11, powered by a Meacedes D-III, 6 cylinder liquid cooled, in line engine of 160HP, was the best all around fighter of the first World War.

[nrshida]

Not really. Two engines, two radiators, the Mossie and Whirlie had two radiators as well, there is no way around the required cooling area, unless you use higher engine temperatures to make a smaller radiator more efficient which to my knowledge Merlin did not use but DB did. The 410 used the standard MT recessed radiator design and not the much draggier surface mounted design e.g. Spitty used.

Respectfully, I think you have missed the point.

Power to weight, reliability and simplicity of operation make the turbine a clear winner.

But you do have to factor in the fuel consumption!

[B3YT]

Not for sure what the questions are that the FAA test requires, but from what I understand, the V block engine was about automobile type engines and how they would work in aircraft. That is why I did not include all the V-block engines of WW2 era. I wish he would be more specific, then I am sure someone could answer him with something that would help.

Erm what are you smoking cos it seems like good stuff . The Rolls Royce merlin was a V block  , so was the WWI RR  Eagle , RR kestrel , Alison V1710, RR peregrine . These were not developed from auto-mobile engines but from the ground up for aero use.   

[Zoney]

This brings us to another interesting point about engines: positive net torque output. If you imagine a cyclist doing his thing, only part of the revolution of his pedals is delivering torque to the bicycle (and hence the road). As his pedal comes over the top only at about 20 degrees or so does the lever of the crank begin to deliver rotational force, at the top and bottom of the pedal rotation and all the way back up there is no positive torgque contribution, infact a negative or a subtraction from the torque is the situation. Only the momentum of the crank and his other leg keeps the whole thing rotating smoothly.

Sir, if you are describing a casual bicycle rider your statement is true.  If you are described a trained bicycle racer you have completely missed the mark.  The professional cyclist has shoes that clip into the peddles.  This allows him to pull up, push forward, and pull back along with pushing down on the peddles.  He will maintain a high rpm, 70 rpm or better and he will not have a "stroke" as you have described it but will be a "spin".  There is nothing in common with a professional bicycle racer's ability to produce power and a reciprocating engine of any type.  The professional cyclist using this "spin" method is also able to use more of the muscles in the upper and lower portion of the leg greatly enhancing his ability to produce more power.

[nrshida]

Sir, if you are describing a casual bicycle rider your statement is true.  If you are described a trained bicycle racer you have completely missed the mark.  The professional cyclist has shoes that clip into the peddles.  This allows him to pull up, push forward, and pull back along with pushing down on the peddles.  He will maintain a high rpm, 70 rpm or better and he will not have a "stroke" as you have described it but will be a "spin".  There is nothing in common with a professional bicycle racer's ability to produce power and a reciprocating engine of any type.  The professional cyclist using this "spin" method is also able to use more of the muscles in the upper and lower portion of the leg greatly enhancing his ability to produce more power.

It's just an analogy Zoney. Not that type of cyclist no, just an ordinary one.

[B3YT]

Sir, if you are describing a casual bicycle rider your statement is true.  If you are described a trained bicycle racer you have completely missed the mark.  The professional cyclist has shoes that clip into the peddles.  This allows him to pull up, push forward, and pull back along with pushing down on the peddles.  He will maintain a high rpm, 70 rpm or better and he will not have a "stroke" as you have described it but will be a "spin".  There is nothing in common with a professional bicycle racer's ability to produce power and a reciprocating engine of any type.  The professional cyclist using this "spin" method is also able to use more of the muscles in the upper and lower portion of the leg greatly enhancing his ability to produce more power.

It's not just pro cyclists either . I use clipless (not using toe clips but the type you describe) and so do most cyclists.  though you still get dead spots (11-1  and 5-7 o'clock positions) in fact you don't even need clips to achieve  that , if you tilt your foot forward on the upstroke you can pull up on the pedals .