Aircraft like the R-44 are powered by a Lycoming O-540, which is of course air cooled.

How is it cooled when hovering for long periods or slow taxiing?

For airplanes, this problem takes care of itself as high rpm and super slow (or no) speeds are mutually exclusive.

Is rotor downwash captured and ported over the cylinders?

All recips, as far as I know, have a cooling fan. If you Google r44 engine cooling, they have a bunch of pictures.

You asked pertinent questions.

For R44 systems descriptions start with the POH, free online at https://robinsonheli.com >Publications >R44 Series (in dropdown menu) >R44 POH (2nd dropdown menu) thence Section 7 - Systems Description

Further info can be had in Powerplant chapters of the Maintenance Manual and Ilustrated Parts Catalog, if desired.

The R44's engine cooling air inlets on the aft cowl were designed to capture MR (main rotor) downwash when hovering to minimize hot exhaust gas ingestion to the fanwheel inlet.

Fanwheel-supplied air also cools:
1. Muffler (also used as source of cabin heat)
2. Drive belts
3. MGB (main gearbox)
4. hydraulic reservoir (includes pressure regulator)
5. cylinders
6. oil cooler(s, two on fuel-injected version)
7. alternator
8. magnetos
9. fuel flow divider (fuel-injected version)
10. battery (when mounted in engine compartment)

Zzz,

Simplified explanation (my understanding) of Engine R44 cooling... The engine fan is bolted directly to the engine crankshaft. And ducted to just about everything from bow to stern that needs considerable airflow.

Some interleaved pictures from RHC R44 IPC:

The fan is also a “flywheel” which helps smooth operations:


Shroud:


Miscellaneous example of further ducting from fan:




Initial fan duct:

Got it! Thanks everyone.

8GCBC wrote:Zzz,

Simplified explanation (my understanding) of Engine R44 cooling... The engine fan is bolted directly to the engine crankshaft. And ducted to just about everything from bow to stern that needs considerable airflow.

Some interleaved pictures from RHC R44 IPC:

The fan is also a “flywheel” which helps smooth operations:


Shroud:


Miscellaneous example of further ducting from fan:




Initial fan duct:

Ted,

You need to change your avatar.....

MTV

Looks like an old VW

And Ted, I agree. A new avatar with both your aircraft would be cool. But I’m partial to the RW world.

CamTom12 wrote:Looks like an old VW
And Ted, I agree. A new avatar with both your aircraft would be cool. But I’m partial to the RW world.

How do you guys like my avatar?

Sold my Scout, God blessed me during my ownership, I loved that bird.

8GCBC wrote:

CamTom12 wrote:Looks like an old VW
And Ted, I agree. A new avatar with both your aircraft would be cool. But I’m partial to the RW world.

How do you guys like my avatar?

Sold my Scout, God blessed me during my ownership, I loved that bird.

Oh no! That’s too bad you couldn’t keep both!

Got any floats yet? Do they spin around on the water like a bug?

Gary