Rotation side of jet engine? / critical engine?

[WhySoTough]

Firstly. My questions are for the a320, but I'd imagine most jets are similar in this sense? Or?
What direction do the two engines rotate?
Is there a critical engine with jets?

Forgive my silly questions. :O

[B737900er]

The fan spins anti-clockwise, there is a white spiral on the cone of the fan to show you which way and if the fan is spinning.

I would tell you the answer to the critical engine question but to make you learn how to reference information, which is a required skill that is needed in this game, I recommend searching the definition of critical engine and read the basic mechanics of a jet engine and let you make up your mind :ok:

[DaveReidUK]

I'd imagine most jets are similar in this sense?

Not necessarily. :O

http://cdn-www.airliners.net/aviation-photos/middle/0/4/9/0989940.jpg

[hetfield]

On northern hemisphere anti clockwise, clockwise in southern hemisphere due to coriolis force;)

[enicalyth]

Historically US engines rotated one way and European ones the other. So it all depends. For that reason 5 minutes before crossing from one hemisphere to the other first one engine on a twin is shut down and restarted spinning the other way and then the next. Which to shut down first depends on Airbus or Boeing. The RAF flew TriStars and had to land at Ascension before going on to Mount Pleasant because of this. It was known as going tech at Asi and aircraft always went tech at ASI. Great care had to be taken to offset Coriolis force on Triples eg Rollers go one way and PW the other. It was not unknown for the MD-11s to get confused and many handling mishaps were due to this cause. Funnily enough DC10s managed to get it sorted but then they had real flight engineers. MD eventually scrapped the fleet because of the risk of memory items being recalled incorrectly. With Quads it is possible to have them going both ways so none of this applies to A380/A340/B747. Only twins on EROPS or Engines Run Opposite Sides need this rule these days. Contra-rotating props were especially designed to cross the equator and the only worry was if they carried enough oil in the first place.

[Microburst2002]

The british engineers waited to see in what sense other countries engineers decided to make their fans rotate.

Then they designed theirs rotating in the opposite direction...

;)

[FERetd]

Microburst 2002 - You mean the proper way!

[yotty]

Ah, but is that anti-clockwise VFR or VFF? :confused:

[z.khalid]

Just to clarify.
It's counter clockwise looking at it from the outside yes?
Or assuming rotation direction while sitting in cockpit?

[Lightning Mate]

Conventionally, the rotation direction is as viewed from behind the aeroplane.

[code0]

mmm just to add to that side of rotation of the turbine engine is a tricky one! sometime your fan N1 shaft turns one way and the N2 turns the other way to cancel out the centrifugal force. if not you will be internally pushing those rudders beyond the limit :) or might have to take a brick in ur travel bag!

so I guess the engine turns both ways! but the fan module or the N1 is what you see turning from outside! and the turning side depend on the manufacturer. And as someone said earlier the white snake on the tip of the fan module will tell u which way it turns.

Normally direction of the rotation is judged from the back of the engine facing the front of the airplane.

there are some contra-rotating and counter rotating configurations in turboprops and turboshafts. let me stop there!

Code0

[AirGek]

What if we fly along the equator? Is it up to the pilot or one engine has to spin one way and the other one the other way? :hmm:

[EEngr]

Microburst2002:
The British engineers waited to see in what sense other countries engineers decided to make their fans rotate.

Then they designed theirs rotating in the opposite direction...And when the Soviets copied British and American designs, they couldn't make up their minds,
So ....

http://www.aerospaceweb.org/aircraft/bomber/tu95/tu95_09.jpg

http://en.wikipedia.org/wiki/File:Tupolev_Tu-95_Marina.jpg

[Smudger]

enicalyth... I'll have a pint of whatever you're drinking !

[john_tullamarine]

E - what's the world coming to ? You intent on giving away all the secret engineers' stuff ?

Love it.

[Smilin_Ed]

I'll have a pint of whatever you're drinking!

Make mine a quart! :O

Ed

[john_tullamarine]

sometime your fan N1 shaft turns one way and the N2 turns the other way to cancel out the centrifugal force. if not you will be internally pushing those rudders beyond the limit

Just had a re-read. Can you run the background to this statement past us once again ?

[FE Hoppy]

On some types it's changed on an odd or even day to balance wear. Windmill relight with unfavourable screw could demand the infamous tail slide manoeuvre!:bored:

[blackhand]

sometime your fan N1 shaft turns one way and the N2 turns the other way to cancel out the centrifugal force Correct, the T53 Turboshaft engine does this as well, also keeps the anti torque control off the stops;)

[DaveReidUK]

sometime your fan N1 shaft turns one way and the N2 turns the other way to cancel out the centrifugal force. if not you will be internally pushing those rudders beyond the limit

Just had a re-read. Can you run the background to this statement past us once again ?

The Pegasus in the Harrier has LP and HP spools rotating in the opposite direction (to minimise gyroscopic precession in the hover, nothing to do with centrifugal force), but off the top of my head I can't think of any other examples.

[Pontius]

The Pegasus in the Harrier has LP and HP spools rotating in the opposite direction (to minimise gyroscopic precession in the hover

Correct. Precession meant everything changed by 90 degrees once you got into the hover. For instance, if you wished to yaw the nose to the right you pushed forward on the control column. Pitch the nose up = roll right etc. It was quite easy once you got used to it but the transitions to and from the hover were considered quite tricky manoeuvres and the classic Harrier 'steep climb' from the hover, performed at air shows, the trickiest of them all.

To add a fly to the ointment, Coriolis meant reversing everything in the Southern Hemisphere (remember it was already contra-rotating, so there's no ability to swap the direction of rotation). Embarked on a ship, this involved a LOT of concentration having crossed 'The Line' and having to do it all over again on the way home wasn't too much fun either.

[Daniel_11000]

Pontius,
do you mean that my Piper Cub in Australia will yaw right during take-off when I’ll push forward to lift its tail , due to Coriolis effect, ??
I do not believe that ! ! Be serious ! !

[DaveReidUK]

I do not believe that ! ! Be serious ! !

I hope you aren't being. :O

But if you are, you might want to re-read the thread title.

[code0]

Add to above, John, check out the RR TRENT family . . .

[Daniel_11000]

DaveReid
I suspect that you misunderstand the fact that rotational mass (i.e.: rotors, like spools, propellers,fans) dynamics is completely independent from the type of engine behind it ! !
D

[code0]

Daniel, what Pointus is talking about is an effect induced by the propeller. Since because the propeller is also a "wing" when you nose up, the the angle of attacks change between (or among) the blades. so the down going blade and the up going blade produce a net force that make a yaw - Asymmetric propeller effect

Heavy 4 engined turbo props have their vertical stabilizer offset the butt line of the fuselage to compensate this, and not sure about the Cub but small single engined piston props have their engine little angled against the butt line. I have also heard (not seen yet!) there are small props with wash-in in one wing and wash-out in the other.

the maximum effect of these forces induce at the cruising speed, so they design the plane to be stable for the cruise.

stand to be corrected!

[Daniel_11000]

Code0
thank you for clarification, but..
the effect you are referring to is sometime called P-Factor (I do not know why), and is purely, as correctly you are saying, an aerodynamic effect ; when the propeller axis is not parallel with the wind (but only and strictly in this case) , the downgoing blade has an higher AoA of the upgoing blade, and this creates an asymmetry, which results in moving the center of lift (thrust, in the propeller case) toward the downgoing blade – and not in the center of the propellerazis. This happens an a bycicle a/c, even if it rests in its three-point attitude ; even if the axis is not moved, the asymmetry gives a yawing torque.
But when the tail is lifted in ‘my’ Cub (or in the Harrier !), the rotor axis (propeller, or jet engine spool in the Harrier case) is subject to a disturbing torque, and reacts with a 90° torque, which becomes greater if the disturbing action is quicker (gyroscopic effect)
D

[code0]

you are welcome!

Add to that...

The effects acting on a propeller aircraft are as follows - NOT the Harrier and I have no idea about how Harrier behaves! :oh:

Torque Reaction - your engines turn one way and fuselage try to turn the other way - makes a yaw effect

Gyroscopic Effect - when you yaw, it tries to make a nose down and when you pitch up, it tries to make a yaw, its just because the 90` effect of the point a force is applied from.

Spiral Effect - single engine prop wash make a "air wrap-around" the fuselage and attack the fin, making a yaw!

Asymmetric Blade Effect - what you have precisely mentioned

Finally and importantly

Atmospheric conditions - whatever the weather report contains!

I am not sure how these effects are applied on a turbofan, but mostly applied on turbo props and piston props! the explanation is quite lengthy! if you can do a search on above mentioned you will sure find the answer what you are looking for.

Code0

[Daniel_11000]

“NOT the Harrier” ? Not really indeed ! Gyroscopic effect act on every (every) rotational mass, even on rotor spool and fans (and if I remember correctly, Harrier has a proportionately biiig fan! ).
….and after having ‘my search’ done during many years of my professional life, I can confirm you that, as I have correctly stated in my post #27, only the gyroscopic effect - among those you listed -is the only one that applies also to jet engines – including the Harrier’s one , though me too I have no idea how this aircraft behaves .But I am sure engine and bearing designers did a lot of homework to take it into consideration in their design ! !

[code0]

“NOT the Harrier” ? Not really indeed !

D! what I meant was, i have NO idea about how Harrier behaves not that I have done much of studying about the aerodynamics or the engine. :)

But I will leave one clue with you, as the Harrier could "hover" or take off and land vertically, during this maneuver, if the engine is rotated in one direction, how to cancel out the force? wouldn't the fuselage and the whole body try to yaw (rather rotate) as it takes off? Helicopters have a tail rotor, does the Pegasus has some sort of mechanism? I have no idea, just for the learning!

Code

[Daniel_11000]

tip jets , if I remember correctly.
D

[DaveReidUK]

But I will leave one clue with you, as the Harrier could "hover" or take off and land vertically, during this maneuver, if the engine is rotated in one direction, how to cancel out the force?

Have you read post #20 ? :ugh:

[john_tullamarine]

to minimise gyroscopic precession in the hover, nothing to do with centrifugal force

That sorts out my confusion ..

[Tu.114]

Of course, as soon as a conveyor belt becomes involved, it all is different again...

[barit1]

N1 shaft turns one way and the N2 turns the other way

Historical quiz: What was the FIRST engine to employ this crazy scheme? :p

[hetfield]

BTW, anyone who knows the turning direction of airbus versus boeing toilett flush motors?

[TURIN]

GEnx has contra rotating shafts as do some variants of the RR Trent.

[lomapaseo]

GEnx has contra rotating shafts as do some variants of the RR Trent.

Why should this make a difference with only one fan shaft per engine?

[TURIN]

I think it's to reduce the need for a row of stators between the IP/LP shafts in the case of the Trent and the LP/HP shafts for the GEnx.
Shortens the engine, saves weight etc.

Although I could be wrong. :O

[lomapaseo]

I think it's to reduce the need for a row of stators between the IP/LP shafts in the case of the Trent and the LP/HP shafts for the GEnx.
Shortens the engine, saves weight etc.


\
Agree with that, I must have missed another ewe turn again. I thought we were in a critical engine on a side thread :)