Direct Drive

[slick1537]

Finally made my move, found a job, and started my flight training so everything is finally falling together and working out great. I have 3.6 Hours of flight time and about double that in ground time (due to weather). However my instructor told me if asked to describe the power plant one thing I need to say is, "Direct Drive." I understand how the whole transmission works. However what would be an example of non-direct drive. What other types of drive is there?

[Gunner]

Impress your examiner and say this instead... (assuming you are in an R-22)

 

Horizontally mounted Lycoming O-320 (O-360-J2A on the Beta II), four-cylinder, air-cooled, normally-aspirated, carburetor-equipped piston engine, fueled with 100LL grade aviation gasoline.

[apiaguy]

The other type of engine is a geared engine......ie. GTSIO 520 continental... has a gear on the crank and a gear for the prop drive.

Internal planetary gear reduction... don't even know one for that one.

[captkirkyota]

An example of a non-direct drive would be ...... edited and deleted my answer due to the I got for an incorrect suggestion to a question. Lesson learned, do not offer up anything around here because temperamental people would rather tell you you are stupid rather than offer nice corrective inputs for the newbs to learn all while not being put off from the way it was said. So ends the lesson for today.

Edited August 1, 2007 by captkirkyota

[mechanic]

I think your CFI wants you to repeat what the POH states, per page 1-5 in Section 1.

 

Powerplant:

Lycoming O-320/360 XXX, Four- Cyl, Horizontally- opposed, direct- drive air-cooled, carubureted, normally- aspirated.

 

I think it refers to the cooling system! Direct Drive Cooling Fan. Hence, direct drive air-cooled....

 

Later

[apiaguy]

my goodness this site brings out people that don't know what the hell they're talkin about but they'll sure spout off...

 

Direct drive refers to the crankshaft being THE output shaft for connection to whatever you are driving.... ie. propeller, drivetrain, etc...

 

It does NOT have anything to do with the cooling fan or any of that crap and a turbine is NOT an example of a non-direct drive.

[joker]

Direct drive refers to the crankshaft being THE output shaft for connection to whatever you are driving.... ie. propeller, drivetrain, etc...

 

This is opposed to a non-direct drive engine (or rather, geared engine) where there is a reduction gearbox between the crank shaft and the 'output' drive shaft.

 

This is more weighty than direct-drive (due to the gearbox) and also more expensive, but does allow for optimum engine operation. Some fixed wing aircraft have this in order to gain optimum power for different regeimes of flight. However, as we run at constant rpm in helicopters, I guess this gearbox would be pretty much pointless.

 

APIAGUY, how did I do?

 

Joker

[mechanic]

my goodness this site brings out people that don't know what the hell they're talkin about but they'll sure spout off...

 

It does NOT have anything to do with the cooling fan.

 

 

My goodness the site brings out people that ARE smartasses doesn't it. Even when someone said "THINK", there is a difference. What I said is correct, it is a direct drive cooling fan. Airplanes are just lucky to have a prop direct drive and engine located in the front for cooling effect.

 

Um, let me check ASA R22 pilot guide and R22 POH. Ahh, yes here it is.

 

POH, section 7, page 7-3, A direct drive, squirrel-cage fan mounted to the engine output shaft etc.....

 

ASA R22 Pilot Guide page 1-8, The engine is air cooled, a large direct drive squirrel cage cooling fan etc.....

 

When you look at both sections of the above books for "Drive System", they don't terminate the description the same. They say a sheave is bolted directly to the engine output shaft. V belts transmit power etc... Again, a sheave and belts are not direct drives.. Thats what uncle sam said anyways.. And, in the R22 POH there is no comma between direct drive and air cooled, could be a misprint though?

 

I still believe the reference to direct drive is a reference to the cooling fan/system...

Sheaves, belts, or sprag clutches aren't synonymous with direct drives. Direct drives have no slippage. This is descriptive only and is not an engineering class or lecture.

[RotorWeed]

My goodness the site brings out people that ARE smartasses doesn't it. Even when someone said "THINK", there is a difference. What I said is correct, it is a direct drive cooling fan. Airplanes are just lucky to have a prop direct drive and engine located in the front for cooling effect.

 

Um, let me check ASA R22 pilot guide and R22 POH. Ahh, yes here it is.

 

POH, section 7, page 7-3, A direct drive, squirrel-cage fan mounted to the engine output shaft etc.....

 

ASA R22 Pilot Guide page 1-8, The engine is air cooled, a large direct drive squirrel cage cooling fan etc.....

 

When you look at both sections of the above books for "Drive System", they don't terminate the description the same. They say a sheave is bolted directly to the engine output shaft. V belts transmit power etc... Again, a sheave and belts are not direct drives.. Thats what uncle sam said anyways.. And, in the R22 POH there is no comma between direct drive and air cooled, could be a misprint though?

 

I still believe the reference to direct drive is a reference to the cooling fan/system...

Sheaves, belts, or sprag clutches aren't synonymous with direct drives. Direct drives have no slippage. This is descriptive only and is not an engineering class or lecture.

 

 

The cooling fan is not part of the power plant. Direct drive refers to output flange being directly driven by the crank. Or in a gear drive motor the output flange is driven by gears. Anyone remember the old Cessnas that had the gear drive props?

[mechanic]

The cooling fan is not part of the power plant. Direct drive refers to output flange being directly driven by the crank. Or in a gear drive motor the output flange is driven by gears. Anyone remember the old Cessnas that had the gear drive props?

 

If the engine cannot operate with out it,then its a required componet. You better call Frank and have him change the POH Powerplant description in Section 1. Its been awhile since I saw a O-320 crank. The flange IS the crankshaft.

[RotorWeed]

If the engine cannot operate with out it,then its a required componet. You better call Frank and have him change the POH Powerplant description in Section 1. Its been awhile since I saw a O-320 crank. The flange IS the crankshaft.

 

Apiaguy gave an example of a non direct drive aircraft power plant the GTSIO 520 continental.

Not all power plants used in avation are direct drive. This discription has nothing to do with what ever is connected to the output flange. Joker, Apiaguy, and Gunner are all correct.

[Guest pokey]

However what would be an example of non-direct drive. What other types of drive is there?

 

I dont think their wording of "direct drive" is the best description of the engine. To put it simply, it just means that the power being absorbed, & the power being provided by the crankshaft is 1 to 1, (RPM - wise, that is). As in no gear reduction.

 

When you are swinging a large diameter propeller, you want to keep the tip speed w/ in reason. The crankshaft speed to satisfy this propeller speed may not be w/ in reason (too slow) SO? they put a gear unit INSIDE of the engine, coupling it to the propeller. Now i know what yer gonna say next, "well in the helicopter we have a reduction transmission" YES we do, but? THAT transmission is NOT an integral part of our "direct drive" engine. It is a separate unit.

 

 

In your car? Your engine is direct drive also. It is the transmission bolted to the end of the engine that makes the different speeds & drives.

 

Take a look at FAR part 43, appendix A b2ii

 

and as for some of the arrogance? we ALL need to think a bit B4 we push the "post" button

[RotorWeed]

That was a very good discription of a direct and "non direct" drive power plant. Lycoming does NOT provide the cooling fan as part of their engine. It is a Robinson built unit that is connected to the crank shaft, after the engine is installed into the airframe. Thank yo Pokey.

 

RW

[Guest pokey]

Anyone remember the old Cessnas that had the gear drive props?

 

I i i i i , son of a ! its on tip of my tongue, i'll have too get out my Cessna Wings to the world history book & get back to ya,,,,,, my 1st thought is round engine, but i think thats wrong,,,,,,,,, ( i can tell ya this tho, i never worked on one)

 

 

Thank yo Pokey.

 

RW

 

yer welcome RW

[palmfish]

I i i i i , son of a ! its on tip of my tongue, i'll have too get out my Cessna Wings to the world history book & get back to ya,,,,,, my 1st thought is round engine, but i think thats wrong,,,,,,,,, ( i can tell ya this tho, i never worked on one)

yer welcome RW

 

Cessna 175

 

From Wikipedia..."An unusual feature of the 175 is the use of the geared Continental GO-300 engine. Whereas most single-engine airplanes use direct drive, this engine drives the propeller through a reducing gearbox, so that the engine runs at 3200 rpm to turn the propeller at 2400 rpm. The engine was esssentially an O-300 engine with a gearbox mounted on the drive end, and some internal modifications to provide durability at higher engine speeds."

Edited August 1, 2007 by palmfish

[apiaguy]

aahhh......

 

1. Just mean to say to those making a post that if they really have no idea then a post about their thoughts doesn't help anyone... just adds confusion.

 

2. you did fine joker

 

3. mechanic..... I don't have a problem with you saying the fan is direct drive... it is.... but the original question was the powerplant description of direct drive.

[slick1537]

Thank everyone for their responses. I didn't really understand until pokey added his post. I understand completely now. Thanks!

[RotorWeed]

Cessna 175

 

From Wikipedia..."An unusual feature of the 175 is the use of the geared Continental GO-300 engine. Whereas most single-engine airplanes use direct drive, this engine drives the propeller through a reducing gearbox, so that the engine runs at 3200 rpm to turn the propeller at 2400 rpm. The engine was esssentially an O-300 engine with a gearbox mounted on the drive end, and some internal modifications to provide durability at higher engine speeds."

 

Great find! I haven't worked on a "gear drive" Cessna for about 22 years now but that is a great example of a "non direct drive" power plant. I've known a couple 175 owners that swear by them!

Thanks for the posting palmfish.

 

RW

[mechanic]

3. mechanic..... I don't have a problem with you saying the fan is direct drive... it is.... but the original question was the powerplant description of direct drive.

 

apiaguy or pokey,

 

First, I am not trying to be difficult! But, why does the R22 POH in section 1 descriptive data, say "direct drive air cooled" not "direct drive, air cooled"??? That comma threw me. Is it a misprint?

 

When you go to section 7 and look at systems descriptions, they list different items.

 

 

Examples, from current up to date R22 POH as of Apr 07:

Section 1 Powerplant

Lycoming O-320/360

Four-cyl, horiz opposed, direct drive aircooled, carbureted, normally aspirated.

 

Section 7 Powerplant

One Lycoming four cyl, horiz opposed, overhead valve, aircooled, carbureted eng w/ a wet sump oil system, etc, etc,....Skip to next paragraph.

 

A direct drive, squirrel-cage fan mounted to the engine output shaft supplies cooling etc, etc,....

 

 

If the examiner wanted they could choose either right? Which one should be quoted?

 

Is this the norm for all POH's?

 

Later

[RotorWeed]

I looked back through my check ride notes; this was a question a DPE asked me on one of my check rides. The correct answer he was looking for was "Four-cylinder, horizontally opposed, direct drive, air-cooled, carbureted, normally aspirated". The examiner could care less about the cooling fan since it is not part of the power plant; that is part of the aircraft.

 

I'm posting this for the noobs that are getting ready to take a check ride not to cause hate and discontent.

One thing I did to prepare for my check ride is ask to see my CFI's check ride notes from all the check rides he'd ever been part of. I put all the data into a data base, and made sure I knew all the correct answers for the oral. hint hint

 

Good luck on your check ride.

 

RW

[apiaguy]

Mechanic..... I really don't know if there needs to be one....(a comma between direct drive and air cooled)

The engine is a direct drive air cooled engine... that just means it is cooled by air......not water or some other medium. Only later in the descriptive data for the particular aircraft does it mention the primary source for airflow... ie..squirrel cage fan

 

I don't think any examiner would give you crap if you said either... the verbage of the airflow source (caged fan)... is only more descriptive and applicable to the helicopter installation. What an examiner is trying to get out of you is that you understand the basics of the powerplant you are operating.... that it is a direct drive design.... and that it is aircooled.

 

 

Think of the engine separately from the squirrel cage fan assembly..... now the engine WITHOUT that fan assembly is STILL a direct drive aircooled engine. Does that help?

Edited August 2, 2007 by apiaguy

[palmfish]

Great find! I haven't worked on a "gear drive" Cessna for about 22 years now but that is a great example of a "non direct drive" power plant. I've known a couple 175 owners that swear by them!

Thanks for the posting palmfish.

 

RW

 

Yeah, I've been living and breathing Cessna's for the last 6 months as I've progressed through my fixed-wing add-on ratings - flying a 172, 206, and 210. You might be interested to know about the Soloy 206 I'm flying now. It's a Cessna 206 with a 420 hp Rolls Royce (Allison) C20 turbo-shaft engine driving a propeller reduction gearbox. It's a very cool airplane...

 

http://soloy.portal.acrosonic.com/ViewDocu...x?DocumentID=17

 

BTW, I must admit I've never thought about (or been asked about) direct drive vs. non-direct drive engines before. Is this a common Robinson question? Also, I was wondering, what do you Robinson pilots do with the squirrels in between flights? Do they stay in the fan cage or do you bring them inside the FBO?

Edited August 2, 2007 by palmfish

[Pogue]

Also, I was wondering, what do you Robinson pilots do with the squirrels in between flights? Do they stay in the fan cage or do you bring them inside the FBO?

Smart pilots bring them in and feed them popcorn. They want acorns but that makes them fat and screws up your weight and balance...

[RotorWeed]

Smart pilots bring them in and feed them popcorn. They want acorns but that makes them fat and screws up your weight and balance...

 

The squirrels stay in the cage!!! It’s a little known fact that the squirrels are actually the “power plant”. The trick is to get them all running in the same direction so you can achieve max take off power.

 

rw

[Gomer Pylot]

A reasonable examiner just wants to know that you understand the basics, not that you can quote Bible passages from memory. And just because you can quote paragraphs from the POH doesn't mean you really understand anything. As long as you can show that you know how the thing works, you should be fine. Of course, there are unreasonable DEs who just want to make sure you are suitably impressed by by their exalted position, but I've never dealt well with those, and they're not that prevalent.