I always thought that radial engines must have an odd number of cylinders.

Going to Google these two questions

Edit: For 4 stroke engines, there must be an odd number of cylinders:
So, I assume that in 2 stroke engines, an even number of cylinders would be acceptable.

Why does a Radial Engine always have an odd number of cylinders ? Any four stroke engine, regardless of construction, must fire all of the cylinders in two revolutions of the crankshaft.

Unlike an automobile engine, a radial engine has only one crankshaft throw for all the cylinders in a bank.

Remember that an 18 cylinder engine is just two 9 cylinder banks, set 180 degrees to each other.

The firing order starts with the #1 cylinder at the top and proceeds around the engine in a counter clockwise direction as viewed from the front. The firing order progresses from the #1 cylinder, skips #2 cylinder and fires #3 cylinder.

So in the first revolution of the crank, the firing order would be #1, #3, #5, #7 and #9.

Using this skip and fire technique, the next cylinder to skip on the second revolution of the crankshaft, would be the #1 cylinder.

On the second revolution of the crank, the firing order would be #2, #4, #6, #8.

Again using the skip and fire technique, the #9 cylinder is skipped and the #1 cylinder is again ready to start the whole process over again.

If there were an even number of cylinders, half would never be fired.

 

Semi-obscure rotary wing question:

What do Russian and French-made helicopters (among others) have in common?

 

You are correct sir!!!

 

You got one part of the answer and the second part was embedded in what you copied from the internet. There can be an even number of cylinders in engines with an even number of banks. Thus a two bank engine with 7 cylinders per bank has 14 cylinders.

 

1. They are not made in the USA.
2. They have a rotary wing.
3. They need some sort of fuel to fly.
4. They are all constructed with metric hardware.



I'd have to ask the interwebz.

 

OK, a semi-trick question!

 

All of ^these are correct. Perhaps I should have added that helicopters made in the US and many other countries do not have what I am looking for in common.

 

All of ^these are correct. Perhaps I should have added that helicopters made in the US and many other countries do not have what I am looking for in common.
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I'm going to take a wild guess and say that their rotary wings have a fixed angle rather than an adjustable angle.

 

Hint: (It's not the tail rotor)

Bell 412 Made in the US:


French Dauphin:

 

Nope. All helicopters must be able to change the pitch angle of the rotor blades.