Counter-rotating props essay

riot shields

riot shields

Well-Known Member
anybody know of any links to information on counter-rotating props on multi engine planes? i've got to do a paper on it, and its tougher than expected to find some damn sites!

thanks!
 
I don't know of anything on the internet, but what do you want to know? There are some pretty sharp people here on Jetcareers (myself not included, but I do fly one), maybe you can get some info. from here.
 
one of my problems is i never think out what i plan on writing about, i never make an outline or a rough draft, i just.. go with it. so i decided to do a paper on the advantages of conter-rotating propellers on multi-engine airplanes.
so i guess, if anybody thinks of any advantages, that would be great.
my report is due in.. oh.. less than 3 hours.
ive had over 3 months to do it.
i love procrastinating!
 
riot shields said:
one of my problems is i never think out what i plan on writing about, i never make an outline or a rough draft, i just.. go with it. so i decided to do a paper on the advantages of conter-rotating propellers on multi-engine airplanes.
so i guess, if anybody thinks of any advantages, that would be great.
my report is due in.. oh.. less than 3 hours.
ive had over 3 months to do it.
i love procrastinating!
Click to expand...

I have some free time...want me to write the report for you? How many words/pages does it need to be? I won't charge a cent...

















:sarcasm: Good luck and let us know how it turns out. That's the tops on procrastinating, even by my standard procrastinations.:) Get a hold of a multi engine book and start reading, look at the avweb article above, and learn what the above acronyms mean that JH posted. Have fun learning.

TX
 
Aw heck Joe, I'm an MEI and I can't even remember what SMACKFUM stands for it's been so long since I gave any multi instruction! I just know that it's important and stuff :)

Airnet still treatin' ya well?
 
Yeah, that's why I didn't write out what those were...I don't remember.:) ;) At least I'm not an active MEI...

Airnet's going good. Sitting standby in 'Bus, possible charter to Columbus, GA either tonight or tomorrow, then in BHM starting Sunday thru Wed. Then back to home (Arlington for a day...I'll give you a call and let you know if I'll have free time; BTW, my cell # has changed.) then JAX for some much needed rest.
 
haha, im in the same boat. i feel like such a horrible instructor trying to remember all those letters associated with vmc. it's been over a year since ive flown a twin. i should have thought this one out!
i should do a report on my school's horrible twin that breaks down every single day and talk about it's.... lack of aerodynamics
 
Notice the ;) . Maybe I should have used a :sarcasm: tag instead...I never gave 1 minute of ME dual but still remember the acronyms and what they are for...it pays to stay in the books to get away from the "theory of disuse". It was a dig at JH (friendly fire) for being an active CFI and MEI (I think, anyways) and not remembering.
 
I am assuming you mean counter-rotating propellers in the sense of two propellers mounted to one engine rotating in opposite directions. Here are my thoughts on the matter.

1) Elimination of some of those left turning tendencies if the multi engine aircraft did not have counter rotating engines.

2) A propeller generates thrust when it pushes air rearward along the longitudinal axis of the aircraft (action-reaction). However, a propeller does not shove air purely rearward, it sends air back in a spiraling slipstream. Any swirl the propeller imparts is useless, wasted energy because the tangential component of that velocity does not point rearward. When you have two props operating one behind the other in opposite directions, the second prop imparts exactly the opposite of the swirl of the first prop. Therefore, the two propeller system converts wasted swirl energy in rearward energy and increases thrust.
 
FlyNavy said:
Good article here:

http://www.avweb.com/news/airman/184438-1.html
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That's a neat article, thanks! However, I do have a question: is the author short-selling the benefits of two engines? He makes it sound like high performance singles are ideal unless you can't get enough HP out of one engine, thus making two absolutely necessary. I contend that a 200fpm climb rate from Vyse beats a engine-out glide any day of the week. I'll be referencing a Barry Schiff article about drift-down in a Seminole as soon as I can find it.

J.
 
Realms09 said:
I am assuming you mean counter-rotating propellers in the sense of two propellers mounted to one engine rotating in opposite directions. Here are my thoughts on the matter.
Click to expand...

I was thinking the same thing at first, but as he's explaining it in relation to ME airplanes, I am assuming he's talking about critical engine ops. Otherwise, it would just be counter-rotating props on an engine, or something to that effect. Of course, what do I know, I'm just a cargo guy...:D

TX
 
Yup yup, I'm an MEI (and current to fly twins even!), but I've got zero multi students so the knowledge has gone by the wayside.

But if you want me to teach somebody how to land, boy howdy...
 
Yeah, I need some help landing. Every time I go from the Van to the Baron or Ho, I always flare like I'm still in the Van. I've had some pretty ugly landings...no dings, but definitely could be smoother. Help...:banghead: :bandit:

edited for smilies
TX
 
I've got a theory. You could put an instructor in the plane with any primary student and blindfold him and tell them where they are at in relation to the runway. It would go like this:

Base: Don't raise the nose, stop raising the nose, I know you're trying to raise the nose. You can't pitch for airspeed right here or you'll stall and spin it in.

Final: No, don't flare here, we're at 300'. Don't talk back, I know what you were trying to do. Stop flaring and don't be afraid of the ground.

Flare: Hold it off, hold it off, look down the runway. If you don't look down the runway and hold it off so the mains touch first you're going to drop it in

*SLAM*

See?

Nothing wrong with any of that, just super common errors that almost everybody makes (including myself, I NEVER wanted to flare).
 
Sorry, I forgot to put a smilie on the end there:D . One of these days I'm going to go to an FBO (especially if I hear of an • instructor) and do a discovery flight.

Maybe I'll go up with you if I have time when I'm in town. Although, it would definitely be ugly since I haven't seen an airspeed indicator below 100 Kts until over the numbers...not sure I could muster up the courage to see 55-65 kts on the gauges again:)

edit: and, no I'm not calling you an •...separate thoughts there that could be misread...
 
If you want an interesting topic. The p-38 had counter rotating props but it interferred with airflow over the tail. They fixed it by still having counter rotating props but instead over rotating like the seminole/duchess does they do the opposite and make both engines critical.
 
John Herreshoff said:
I've got a theory. You could put an instructor in the plane with any primary student and blindfold him and tell them where they are at in relation to the runway. It would go like this:

Base: Don't raise the nose, stop raising the nose, I know you're trying to raise the nose. You can't pitch for airspeed right here or you'll stall and spin it in.

Final: No, don't flare here, we're at 300'. Don't talk back, I know what you were trying to do. Stop flaring and don't be afraid of the ground.

Flare: Hold it off, hold it off, look down the runway. If you don't look down the runway and hold it off so the mains touch first you're going to drop it in

*SLAM*

See?

Nothing wrong with any of that, just super common errors that almost everybody makes (including myself, I NEVER wanted to flare).
Click to expand...

I always would flare late, or not enough. Pound it in. Took me a while to get that one down. I found that the pattern procedures were cluttering my brain too much to have anything left by touchdown time..LOL

When the pattern became more automatic it came to me. That has nothing to do with CR props though. CR props eliminate the left turning tendancy I would imagine. Just a guess, I have no first hand knowledge.
 
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