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How to know when prop turns right or left?


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#16 Kostucha

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Posted 19 December 2009 - 03:17 AM

-snip-

Speaking of props, anybody know which WWII fighter has two critical engines, and why??

:speak_cool:



Every twin engine bomber that aborted take off and ended up bellied at the end of the runway with bent props and a flight engineer scratching his head asking...

"Hey captain - what's wrong?"

"Uhhhhh... both engines are critical..."
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#17 zerosystem

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Posted 19 December 2009 - 04:26 AM

I think it's been explained pretty well here but here's a test

Which way are these props turning :lol:

Posted Image


who took the jets off of a perfectly good c-17 :innocent:

#18 Allok

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Posted 19 December 2009 - 05:48 AM

I'm not sure I fully understand the meaning of the question but most WWII aircraft have a less eliptical curve on the leading edges of the props. So if you stand in front of the plane or can't clearly see the pitch of the blades, the prop will be rotating with the straighter bit first.
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#19 Tallyho

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Posted 19 December 2009 - 12:53 PM

I think it's been explained pretty well here but here's a test

Which way are these props turning :innocent:

Posted Image


Inboard: Clockwise
Outboard: Counter clockwise

BTW The prop's direction is referrenced from the pilots view and not the bystanders view.

Fred
Posted Image

#20 alaninaustria

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Posted 19 December 2009 - 03:20 PM

Manufacturer's always reference prop rotation from the perspective of standing behind the engine. The Brits like to have counter clockwise rotation, and the rest of the world employed clockwise rotation. On a single engine prop aircraft you had to be careful during handling because the P-factor was critical to which way the prop rotated... if it was clockwise then you would need right rudder on t/o and if it was the oposite, then left rudder on t/o... there are some variencies to rotation (P-38 comes to mind), but that is a good rule of thumb.
Cheers
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#21 alaninaustria

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Posted 19 December 2009 - 03:29 PM

Regarding the A-400 military bird... the props are scimitar shape to reduce shock wave formation at the tips, and to reduce noise. The silver leading edge strip you see is called an erosion strip and it is only found on the outer section because the inner section contains AC powered deicing heaters. Because the outer section has an increased rotational velocity, thus more cetrifugal force deicing is automatic because the rotational forces will shed any ice accumulation.
The reason that the left and right side props both turn in towards one another is to maintain a uniform thrust vector when one or more engine is lost or shut down. The down going blade will create a thrust moment and the closer this moment is to the aircraft centerline, the easier the handling is during single or mulitple engine operations as well when turning into a dead engine. It is always safer (if you can) to turn the aircraft into the remaining engine because the remaining engine has more induced lift on the wing and if the speed is allowed to drop to a critical level then the aircraft can suffer a dynamoc roll over that without sufficient altitude to recover from, can be deadly. I lost a good friend to this trap back in Canada while flying a Grumman Goose.
Cheers
Alan
Recreating WWII aviation history in 1/32..... one plane at a time!
Stalled builds...
1/32 scale Hasegawa Big Jug... T-bolt stalled!
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Current Builds:
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#22 Jennings Heilig

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Posted 19 December 2009 - 05:35 PM

Manufacturer's always reference prop rotation from the perspective of standing behind the engine. The Brits like to have counter clockwise rotation, and the rest of the world employed clockwise rotation.


That's not entirely true. Lots of British engines turn clockwise (Merlin, Centaurus, etc). The Russians also have engines that turn counter-clockwise. It's more a manufacturer thing than a national tendency.

J

"It's all part of the show..."


#23 alaninaustria

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Posted 19 December 2009 - 07:50 PM

Hi J, thanks for the info... I was thinking mostly from the difference between the DeHav Chipmunk that has the counter clockwise direction and the Cesnna single engine products.... there was a very bad accident at the flight school where I learned to fly many moons ago when one of the fellows who went up in the Chipmunk for the 1st time after flying Cesnnas put in right rudder to counter the P-factor and rolled her up into a ball...
The manufactures's reference line is always from behind the engine looking forward.
Cheers
Alan
Recreating WWII aviation history in 1/32..... one plane at a time!
Stalled builds...
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Finished builds...
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Current Builds:
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Dreaming of.....
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#24 t.valdez

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Posted 19 December 2009 - 07:54 PM

I think I may know the reason why Eli is asking the question as I sold him some Revell P-38 props awhile back. The prop profiles are such that it is hard to tell which is the leading edge of the prop and the trailing edge, as molded. This problem also arises with other products which also exhibit symmetry in the molded product and it is difficult to tell the leading from trailing edge. Hence the question, which way is up? Rather than avoid the problem by putting the props at a fully feathered pitch (when using individual blades as is common with resin AM) or 0 degree pitch, a little research into the individual aircraft can go a long way to determine the rotation of the blade.
It can be difficult. The Lightning I sold to the British in WWII did not have counter-rotating props. The F-82 twin Mustang started with counter rotating props going clockwise and then switched to props going counter clockwise. Merlin engined Spit props went one direction, the Griffon engined props went the opposite direction.

#25 Allok

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Posted 19 December 2009 - 08:06 PM

Hi J, thanks for the info... I was thinking mostly from the difference between the DeHav Chipmunk that has the counter clockwise direction and the Cesnna single engine products.... there was a very bad accident at the flight school where I learned to fly many moons ago when one of the fellows who went up in the Chipmunk for the 1st time after flying Cesnnas put in right rudder to counter the P-factor and rolled her up into a ball...
The manufactures's reference line is always from behind the engine looking forward.
Cheers
Alan

Same thing happened to Tim Wallace in a late model Spit a few years ago. He spent months in hospital, some of it in a coma.
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#26 Jennings Heilig

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Posted 19 December 2009 - 08:17 PM

On American P-38s the props both rotated outboard (over the top). That made both engines critical (speaking about engine out performance in the climb). On airplanes like the Piper Seminole where both props rotate inward (over the top), neither engine is critical. On most twins where both turn the same way, the one with the down-going blade outboard is the critical engine. That would be the right engine on those with clockwise turning props and the left on counter-clockwise turning props.

I'm not aware of any other a/c where the props both rotated outboard over the top...

J

"It's all part of the show..."


#27 LSP_Ron

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Posted 19 December 2009 - 08:41 PM

Same thing happened to Tim Wallace in a late model Spit a few years ago. He spent months in hospital, some of it in a coma.


Yes, It's happened to many Spit pilots moving over from a Merlin powered Spit to a Griffin powered Spit. The Griffin turns oposite to the Merlin. Torque on take off is reversed between these two engines requiring left rudder on the Griffin and right rudder on the Merlin during take off (I think I've got that right?)

Ron



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#28 alaninaustria

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Posted 19 December 2009 - 10:40 PM

Hi J, you got that right about the P-38... it is the only aircraft that I know about too, that has the handed props with the outboard thrust vector. Lockheed was forced to design the handed engine set up like this to avoid the prop slipstream and resultant turbulence causing flutter over the elevator at the rear. From a maintenance perspective the P-38 was not very field maintenance friendly because the engines could not be swapped out left to right or the other way around, they had to be the correctly turning engine for the appropriate side. I love the P-38 and all her ecentricities!

Sorry to hear about the SPitfire pilot, is that the same fella who wapped another Spit up down in NZ?
Cheers
Alan
Recreating WWII aviation history in 1/32..... one plane at a time!
Stalled builds...
1/32 scale Hasegawa Big Jug... T-bolt stalled!
Finished builds...
1/32 scale PCM Re 2005/1/32 scale Hasegawa Ju 87 G-2/1/32 scale Trumpeter Me 262 A-1a
Current Builds:
1/32 scale PCM Hawker Tempest Mk V/1/32 scale Trumpeter A-1H US NAVY Skyraider
Dreaming of.....
1/32 B-26 Marauder; 1/32 B-24; 1/32 Me 410; 1/32 Yak 3&7; 1/32 Saab Drakken....We can dream ..... can't we!?

#29 LSP_Ron

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Posted 19 December 2009 - 10:57 PM

Sorry to hear about the SPitfire pilot, is that the same fella who wapped another Spit up down in NZ?
Cheers
Alan


Hi Alan

Same incident, It's actually Sir Tim Wallis not Wallace and it occurred in NZ in mid 90's

Ron

Ron



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#30 Allok

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Posted 20 December 2009 - 03:42 AM

I think Alan is refering to the more recent incident involving a heavy landing causing the gear to collapse. Different guy, sorry about the spelling.
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