Counter Rotating Props ?

[Rob Schaffer]

Question,... I know that the P-38 Lightning has engines that actually were mirror images of eachother, such that the props also rotated in opposite directions to reduce the torque.

Specifically, I'm looking to find out of the B-17 had them. With four engines, did they all rotate the same way? Inboards vs Outboards? Left wing vs. right Wing?

Need to finish the props on my tattoo and want to make sure I have the rotations correct


also,.. any GA aircraft that has opposing prop directions?

 

[TMetzinger]

Can't answer the B-17 question, but there are several GA twins with counter-rotating props.

 

[bbchien]

Rob, that's actually incorrect about the P38. Though it was designed with counter-rotating props, under pressure of war production, some were shipped with TWO critical engines (to reduce mach airflow over the elevator which became mach blanked in a dive-->crash) and some were shipped with two rightward turning engines.

Very few got deployed with the counter-rotation setup in the CORRECT (righ engine turns left) direction. Aerospace was still working out the problems of mach.

PA-34 has no mach problem. The wings fall off. It's got counter-rotating props.

 

[Yellowbird]

The B-17 props all turned in the same direction, as did the props of all the other WWII multis that I'm aware of (other than the P-38, and the stillborn XF5F).

I was under the impression that the P-38 engines differed only in the gearbox, but I could be wrong.

 

[Ted]

Bruce is correct. The P-38 had counter-rotating props that produced two critical engines, but the tails falling off was the reason for it.

B-17s didn't have counter-rotating props, they were all right-hand rotation.

The only GA planes that come to mind with counter-rotating props are the later Twin Comanches, Navajo Chieftain, Navajo C/R, and the Seneca II-V. The general idea is to make engine-out situations easier to manage and also provide better single-engine performance. However it's interesting to note that once you get to higher-powered twins like the 421, P-Navajo, and then into the turbine realm, they typically have both props spinning the same way. The P-Navajo was something of an anomaly since both its props are left-hand rotation.

 

[roncachamp]

Question,... I know that the P-38 Lightning has engines that actually were mirror images of eachother, such that the props also rotated in opposite directions to reduce the torque.

Not mirror images, the Allison V-1710 could be built up in either CW or CCW shaft output by primarily turning the crankshaft end for end.

Specifically, I'm looking to find out of the B-17 had them. With four engines, did they all rotate the same way? Inboards vs Outboards? Left wing vs. right Wing?

The engines on the B-17 all rotated in the same direction.

also,.. any GA aircraft that has opposing prop directions?

Piper used it on some Twin Comanches and Navajos, Senecas, and Seminoles, the Cessna Crusader, Beech Duchess, perhaps a few others.

 

[roncachamp]

Rob, that's actually incorrect about the P38. Though it was designed with counter-rotating props, under pressure of war production, some were shipped with TWO critical engines (to reduce mach airflow over the elevator which became mach blanked in a dive-->crash) and some were shipped with two rightward turning engines.

Very few got deployed with the counter-rotation setup in the CORRECT (righ engine turns left) direction. Aerospace was still working out the problems of mach.

That's not correct, I believe the only Lightnings produced without counter-rotation were the "castrated Lightnings" ordered by the British.

 

[Ted]

also,.. any GA aircraft that has opposing prop directions?

You could incorporate a P-Navajo into your tattoo. Nobody will know what it is, and most people will think that the guy put the props on backwards.

 

[roncachamp]

You could incorporate a P-Navajo into your tattoo. Nobody will know what it is, and most people will think that the guy put the props on backwards.

Unlikely.

 

[vontresc]

Ok Ted, why did Piper put on two left turning engines on the P-Navajo? Just to screw with the pilots????

Or did Lyc only build left turning TIGO-541-E1As?

 

[Rob Schaffer]

Nice,.. thanks guys.

 

[Ted]

Unlikely.

I've been asked that before about P-Navajos.

Ok Ted, why did Piper put on two left turning engines on the P-Navajo? Just to screw with the pilots????

Or did Lyc only build left turning TIGO-541-E1As?

All the 541s have right-hand rotation crankshafts. The TIGO-541s utilize a single spur gear on the nose of the crank, and that spur gear mates with one connected to the prop. The result is a left-hand rotation prop. I don't know what the reasoning was behind it, probably to minimize the number of parts required. The 541 really was only ever put in the Baron 56TC, Duke, and P-Navajo. The TIO-541-A1A was also put in the Mooney Mustang, but I don't hear much about those. And it was also only 310 HP @ 2575 RPM, vs the 380 HP @ 2900 RPM for the Duke or the 425/450 HP @ 3200 RPM for the TIGOs.

Continental did the opposite with the GTSIO-520s used in the 421 and Commander 685 - the crankshaft itself is left-hand rotation, so add a single spur gear and you end up with a right-hand rotation prop.

What's interesting about this is that I can't think of any straight IO or TSIO-520s (or 550s) that are left-hand rotation. So probably they just did it to make the plane more conventional.

By the way, kudos to you for knowing the designator for the P-Navajo engine!

 

[Ted]

Nice,.. thanks guys.

This conversation is far from over - we need at least 4 more pages of debate.

 

[Telemakhos]

This conversation is far from over - we need at least 4 more pages of debate.

Let's do this! I'll try to be inflammatory. Ready?
Screw counter-rotating props and all the planes that have them! Contra-rotating props are the coolest and best!

 

[vontresc]

Wow nice to have someone from brand L actually acknowlege the existence of the 541s

But I did cheat and look the engine designation up on wikipedia...

 

[Ted]

Wow nice to have someone from brand L actually acknowlege the existence of the 541s

If you read very carefully, at no point did I mention who the maker of the 541 was.

 

[airbornejohnny]

That's not correct, I believe the only Lightnings produced without counter-rotation were the "castrated Lightnings" ordered by the British.

i thought the castrated Lightnings the British ordered only lacked superchargers, but that aside the powerplants were identical.

 

[kyleb]

i thought the castrated Lightnings the British ordered only lacked superchargers, but that aside the powerplants were identical.

They were identical. ;-) Both of 'em turned in the same direction. Parts commonality, you know...

 

[Dan Thomas]

Not mirror images, the Allison V-1710 could be built up in either CW or CCW shaft output by primarily turning the crankshaft end for end.

Camshaft would have to be different, as would magnetos, oil pumps, and so forth.

Dan

 

[roncachamp]

i thought the castrated Lightnings the British ordered only lacked superchargers, but that aside the powerplants were identical.

The British ordered them without turbochargers because they did not envision high altitude operations with them. They wanted right hand drive for commonality with the Curtiss Tomahawks they were also ordering.

 

[OffCenter]

The only GA planes that come to mind with counter-rotating props are the later Twin Comanches, Navajo Chieftain, Navajo C/R, and the Seneca II-V. The general idea is to make engine-out situations easier to manage and also provide better single-engine performance. However it's interesting to note that once you get to higher-powered twins like the 421, P-Navajo, and then into the turbine realm, they typically have both props spinning the same way. The P-Navajo was something of an anomaly since both its props are left-hand rotation.

How about the Cessna 337 Skymaster?

 

[Cap'n Jack]

<SNIP>

also,.. any GA aircraft that has opposing prop directions?

The original Wright Flyer was a GA plane (it wasn't military or scheduled airline) and it had contra-rotating propellers. I didn't read that it had to be a multi-engine plane.

 

[Ted]

How about the Cessna 337 Skymaster?

Ooh, that's a good one. I have no idea. Perhaps our friend who used to own one will chime in.

 

[OffCenter]

Ooh, that's a good one. I have no idea. Perhaps our friend who used to own one will chime in.

I'm guessing that the ENGINES both rotated in the same direction.
But since the rear engine was mounted facing backwards,
the props rotated opposite each other.

 

[denverpilot]

Ooh, that's a good one. I have no idea. Perhaps our friend who used to own one will chime in.

Having watched a moron who didn't maintain his landing gear have to shut the front engine down to "save the prop" and bounce it with the starter key, I distinctly remember the front engine turns to the right.

My second and last flight with that idiot who couldn't afford proper maintenance on either of his airplanes, or so I learned later.

VFR into IMC in the Rockies with the radios acting up too. Guy was a real gem. Held an ATP, too.

It's a long story about how I ended up on a trip in his 337, and how he should have had the gear looked at in Las Vegas, but it's the only time I've had fire equipment on the runway for a landing so far.

Nose gear light came on in the flare after circling and screwing with it for an hour at night.

Dude was a lot luckier than he was smart. Me too. I got a great education as a very low-time Private Pilot about what it looks like to be an accident statistic waiting to happen.

Filed the knowledge and experience in the "Don't ever act like that idiot", and "Don't get in airplanes that have exhibited major maintenance problems before a mechanic works on them." brain-files.

Ride the bus home if you have to...

No matter how convincing the owner sounds when he says, 'Oh it's no big deal, it does this all the time!'

Also learned the lesson, "Rated pilots don't give up control seats to bosses just because they want to sit up front." Got to watch the insanity build from the back seat. Even as a wing-leveler I would have been more useful up front while the guy went heads-down numerous times and forgot about flying the plane while he farted with his landing gear punp breaker, and everything else up there, at night, aimed at the mountains, bank increasing until he'd snap upright at our "heads up" comments over the intercom from the back seat.

 

[Henning]

Rob, that's actually incorrect about the P38. Though it was designed with counter-rotating props, under pressure of war production, some were shipped with TWO critical engines (to reduce mach airflow over the elevator which became mach blanked in a dive-->crash) and some were shipped with two rightward turning engines.

Very few got deployed with the counter-rotation setup in the CORRECT (righ engine turns left) direction. Aerospace was still working out the problems of mach.

PA-34 has no mach problem. The wings fall off. It's got counter-rotating props.

I talked with my great uncle about the 38 a while back, he flew them among others in the war. Most of the ones delivered to US pilots were in the counter rotating (one or the other) The right hand rotation planes were mostly Lend-Lease planes. He also said that the outward turning props gave a tactical advantage by tightening up the turns. He flew the P-38, P-39, P-47 and P-51 and said for a fight, he prefered the P-38 because he could out turn anything to the right.

 

[airbornejohnny]

The British ordered them without torbochargers because they did not envision high altitude operations with them. They wanted right hand drive for commonality with the Curtiss Tomahawks they were also ordering.

not according to the historical figures ive got. America imposed a ban on certain goods being exported to Europe...including SUPERchargers.

 

[Henning]

The original Wright Flyer was a GA plane (it wasn't military or scheduled airline) and it had contra-rotating propellers. I didn't read that it had to be a multi-engine plane.

No, it didn't, contra-rotating props turn opposite directions on a common axis.

 

[roncachamp]

I talked with my great uncle about the 38 a while back, he flew them among others in the war. Most of the ones delivered to US pilots were in the counter rotating (one or the other) The right hand rotation planes were mostly Lend-Lease planes.

All P-38s delivered to US pilots had counter-rotating engines. The engines of the sole XP-38 rotated inward at the top, rotation was reversed with the YP-38s because downwash over the wing center section was contributing to tail buffeting.

The only Lightnings without counter-rotating engines were those made for Britain as the Lightning I. The British accepted three and promptly gave the "castrated Lightning" a thumbs down, canceling the order. The USAAF accepted them as trainers, 19 of them retained right hand engines and were designated RP-322, "R" for restricted. The remainder had counter-rotating engines and were designated P-322.

 

[roncachamp]

not according to the historical figures ive got. America imposed a ban on certain goods being exported to Europe...including SUPERchargers.

Oh, yes, you can find a lot of "historical" material on the P-38 that says there was a ban on the export of the GE turbocharger. But there wasn't one. At about the same time the British and French were placing their orders for turbocharger-free Lightnings the British were also acquiring B-17Cs that did have turbochargers.

 

[RickH]

"...oh, don't give me a P-38,
with props that counter-rotate.
They'll loop, roll and spin,
and you'll soon auger in,
Don't give me a P-38."

 

[airbornejohnny]

Oh, yes, you can find a lot of "historical" material on the P-38 that says there was a ban on the export of the GE turbocharger. But there wasn't one. At about the same time the British and French were placing their orders for turbocharger-free Lightnings the British were also acquiring B-17Cs that did have turbochargers.

http://en.wikipedia.org/wiki/P-38_Lightning
http://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=74

my presumption has always been the ban had fallen under neutrality acts which were adopted by the U.S. before our involvement in WW2. My primary aviation historical resource has passed away so I dont have a direct line to that era anymore. can you prove there was no ban? the vast majority of resources Ive found say that there was; perhaps it was a grey area?

 

[roncachamp]

my presumption has always been the ban had fallen under neutrality acts which were adopted by the U.S. before our involvement in WW2. My primary aviation historical resource has passed away so I dont have a direct line to that era anymore. can you prove there was no ban? the vast majority of resources Ive found say that there was; perhaps it was a grey area?

Does the inability to prove something did not exist prove that it did exist? If the export of turbochargers was banned how was it that the British received B-17s with turbochargers?

 

[airbornejohnny]

Does the inability to prove something did not exist prove that it did exist? If the export of turbochargers was banned how was it that the British received B-17s with turbochargers?

Im just curious...obviously just because something cannot be proven does not necessarily mean it isnt the truth.

not to be overly technical, but the literature i read said superchargers were banned, not turbos. they are different technologies and i would presume supercharging could have been an emerging technology at the time, at least in aviation applications. P-38's were designed by kelley johnson, founder of skunkworks at Lockheed, so it wouldnt surprise me if this was simply intended to keep secrets secret.

 

[roncachamp]

not to be overly technical, but the literature i read said superchargers were banned, not turbos. they are different technologies and i would presume supercharging could have been an emerging technology at the time, at least in aviation applications. P-38's were designed by kelley johnson, founder of skunkworks at Lockheed, so it wouldnt surprise me if this was simply intended to keep secrets secret.

A turbocharger is a supercharger. One of the sources you provided used the terms interchangably.

 

[airbornejohnny]

A turbocharger is a supercharger. One of the sources you provided used the terms interchangably.

yes, the certainly did, however a turbocharger's turbine is spun using exhaust gasses and a supercharger uses a direct drive off the crankshaft, which reduces "turbo lag." i am not sure if the allison 1710-89 powerplants had both, at least in the 38's, but it is possible and not unheard of in other applications.

 

[airbornejohnny]

http://en.wikipedia.org/wiki/Allison_V-1710

just found this...seems to be more variation in calling similar technolgies the same thing.

 

[Cap'n Jack]

No, it didn't, contra-rotating props turn opposite directions on a common axis.

Thank you for the correction. The Wright Flyer was a GA aircraft that had counter-rotating propellers.

 

[roncachamp]

yes, the certainly did, however a turbocharger's turbine is spun using exhaust gasses and a supercharger uses a direct drive off the crankshaft, which reduces "turbo lag." i am not sure if the allison 1710-89 powerplants had both, at least in the 38's, but it is possible and not unheard of in other applications.

Only the V-1710B lacked a mechanical supercharger, I believe their only use was in the Navy's airships.

 

[Doggtyred]

yes, the certainly did, however a turbocharger's turbine is spun using exhaust gasses and a supercharger uses a direct drive off the crankshaft, which reduces "turbo lag." i am not sure if the allison 1710-89 powerplants had both, at least in the 38's, but it is possible and not unheard of in other applications.

Dont forget about power recovery turbines.. which are exhaust driven and apply the energy to the driveshaft (in addition to turbochargers and superchargers).. Many of your big WWII engines used these, especially when you consider 45% of the energy in gas goes out the tailpipe as waste heat.