Engines Turning Both Ways 

The only person on youtube who doesn't encourage people to comment gibberish for "engagement".

Thanks for risking tongue twisters on the weekend for us viewers. It would double (or more than) engineering, manufacturing, supply-chain, inventory, maintenance, and training costs. Standardization (on less) is one key to cost efficiency.

" Closely associated moving parts"...A most eloquent understatement.

I thought it was common knowledge that the turbines spin opposite below the equator! Just kidding, I appreciate your knowledge and explanation skills.

Interesting topic. I've read various aircraft manuals over the years, and I don't remember any warnings about gyroscopic forces from the jet engine affecting aircraft characteristics. There have to be some gyroscopic effects present, engine and airframe designers probably have to take them into account, but it seems it's not significant enough that would warrant warning the pilots in big bold letters. Now with propeller driven aircraft it's different, but again these are not gyroscopic forces that we are trying to cancel out with contra-rotating props, but rather: - P-Factor which causes yaw as the angle of attack increases and the prop centre of thrust shifts. This is especially dangerous in low&slow or engine-out situations. Not a big problem in ducted jet engines, where the angle of attack of the incoming air is small (and if it isn't, you have more serious problems). - Torque. This is simple, you turn the propeller in one direction, the airframe wants to turn the other direction, so you have to cancel that with ailerons. Interestingly even though jet engines produce much, much more torque to drive the compressor and the fan, there doesn't seem to be a lot of torque transmitted to the airframe. Don't know why, but one explanation I've found is that stators cancel most of it as they "push" the air in the opposite direction than the blades. - Propwash. In most aircraft configurations, the air accelerated by the propeller hits the wings and the empennage. However, the air behind the propeller is not moving straight, but swirling, which causes asymmetric lift on the wings and tail surfaces. Another issue that doesn't affect jet aircraft. So it seems there isn't much need to have contra rotating jet engines. Gyroscopic forces are not significant, and other adverse effects are unique to prop driven aircraft. Or at least not as strong in jet engines.

Gearboxes. Duh. Makes perfect sense. I always thought, "Man, that must be a nightmare for those maintenence guys to keep up with two different engines for planes with counter-rotating props."

AgentJayZ, it's been a while since I watched one of your videos. You gave me a fascination with turbines. So simple, so complex. If only I was younger...

Interesting and humorous. Thanks for having me as company. Enjoyed myself. Dan USA

As a pilot, there's no reason to have turbojet/turbofan engines in counter-rotation. Jet's do not create p-factor and torque issues. Most turboprops are not counter-rotating, so there is a "critical engine" in the event of a single-engine failure. The torque and p-factor can cause a "Vmc rollover" if the critical engine is operating at high power and the aircraft speed is allowed to get too slow. There are a very, very few TP's which AFAIK have engine cores that turn the same direction, but gear reduction drive does the reversal. Counter-rotating props are more common in piston aircraft, where critical engine performance is more important. Many, but not all, light piston twins used for training and private flying have counter-rotating engines to eliminate the critical engine in one-engine-inoperative situations.

No, the props on the 'Mossie' rotated in the same direction, and I believe that, as a result, the aircraft had a bit of reputation for a tendency to 'swing' on take-off. but nothing that a competent pilot couldn't handle. I believe that the Lockheed P-38 had opposite rotation Allison V-1710 engines driving (obviously!) opposite rotation props, rather than using an idler gear to reverse the direction of prop rotation. Like you, AgentJayZ, I am not aware of any gas turbine engine type that has been built in two versions, with opposite direction of rotation of the turbomachinery. Having said this, the Airbus A400M Atlas has opposite rotation props for each pair of TP400 engines. However, the turbomachinery rotates in the same direction in all four engines, with the reduction gearbox reversing the direction of rotation. PS the Merlins for the DH Hornet did have opposite-hand rotation props, but this was done with an idler in the reduction gear.

dont know about the mosquito but the DH Hornet had Merlin 130+131 engines, the only difference being there was an idler gear to allow one propellor to turn in the opposite direction. the tp400 for the A400M Atlas has the same arrangement. RR/Rover Meteor(tank engine version of the merlin) "The major change for tank use was to reverse the direction of engine rotation. Automotive gearboxes ran the opposite way to an aircraft propeller and changing direction required modification of the camshaft lobes (most Merlins were "right-hand tractor", i.e. the propeller rotated clockwise when viewed from the rear)."

Same goes for the majority of multi engine boats. The reverse rotating propellers on a multi engine boat have different gear boxes and the same engines.

I think j zed missed the most important thing about anticlockwise engines. Those engines preform better south of the equator... Just saying 😂

The belief that a jet engine has only one moving part comes from a 1950s ad introducing the De Havilland Comet, it was a picture of the Ghost engine centrifugal compressor connected by its shaft to a single stage turbine wheel, showing how simple a jet engine was as compared to a recip. Just marketing nonsense of course but it’s amazing how this misperception persists over half a century later.

You always present very informative content, Thank You. Best Wishes to You and Your Family.

18:18 the Best Simpson's reference EVAR! Saxa-maphone!

It's interesting that you've addressed this topic, AgentJayZ, only a matter of days after I read something about the so-called Cobra manoeuvre, which I've only just remembered. It must have been on the internet somewhere, but I can't remember where I came across it and to what aircraft it was referring! My recollection is that article was referring to an aircraft with two engines (F-18 or Su-27?), and it stated that the manoeuvre had to be done with one engine at high or max thrust, with the other engine throttled right back, plus a rudder input, to keep the aircraft straight as it pulled up. This, as I understood it, was to counter the gyroscopic couple effect as the aircraft pulled up to the vertical with a relatively low airspeed, with the nose then dropping rapidly. Since the Pegasus in the Harrier was specifically designed with contra-rotating spools, in order to cancel out any significant gyroscopic couple effect in the hover, it seems credible that it could become significant as an aircraft pulls up in the Cobra, with the nose then dropping rapidly at the top of the manoeuvre. Is there anyone out there who could comment on this with authority?

Enjoyed.

That was very, very good question.

I don't doubt for one second that AgentJayZ knows exactly what he is doing... but did anyone else have their anxiety go through the roof watching that front frame get wheeled around on the cart? The thought of such a beautiful bit of technology hitting the ground made my body instantly prep, ready to catch it (even though it is just a video). I guess I'm a bit of a klutz. If I ever stood in such a shop, I'd act like I was in a high-priced pottery store. Time to move very slowly and thoughtfully.

P38 Lightning , Allison V12 piston engines had both a left and right rotation engines ??, or was it just gearboxes ??

Another Friday AgentJay Rant. superb!

Thanks.

Cool bike❤ the twin 🎉

4:45 not a turbojet, but the Piaggio P180 has the PT-6 (-66a I think) have counter rotating props from the addition of an extra gear. That’s more for P-factor than gyroscopic forces. Some piston twins have counter rotating piston engines, I thought the difference is the grind of the cam, but now that I think about it, the oil pumps would have to be different also if that was the case..The 737 must have a different gearbox for left vs right for the way the engines appear squished for ground clearance.

So basically, internet is full of misinformed idio.. sorry people. Even when it comes to jet engines. I love the things you do and how you do it. Educational, pedagogical and... let's call it humble ;) :*

If gyroscopic effects were problematic, we wouldn't have single-engine aircraft. Think about it...1 engine centrally mounted should be a worst-case scenario for roll stability. If the effects were cumulative for multi-engine aircraft, you would expect a lot of B52 crashes (8 engines), but a quick review of all the crash history I could find did not show any loss-of-control attributed to the engines rotating in the same direction. BTW, there have been a LOT of B52 crashes since the 1950's. So, that myth is busted.

A bit pedantic but on the note of F-18 vs F-16, they're rather aerodynamically different and the pilots are trained to fight them differently in bfm. TLDR F-18 is about aoa, F-16 is about turn rate. And agree 100% the gyroscopic effects are negligible when compared to the manufacturing considerations.

thanks for the reply regarding the Canuk Fighter Interceptor developped in the 50's . Is it possible to do a demo on the jet engines it used?

Hey Agent, I've got a question for you about exhaust ducts. If the exhaust nozzle is already operating in a choked condition, does the addition of more energy result in higher thrust due to the pressure wave formed? Or must a convergent-divergent duct be employed in this circumstance. Sorry if this is a dumb question I'm just having trouble grasping some of these concepts.

Rolls Royce Trent turbofans have 3 shafts which turn in opposite directions to i assume counters any gyroscopic forces within the engine, i don't know if GE or PW 2 shaft engines do thesame?

hi ajent jay z, I'm dean from kenya and i have a question.in high/low bypass turbofans,most of the rain water usually goes around the bypass area due to the centrifugal forces of the fan.but in a pure turbojet, wouldn't the rain water go directly through the compressor and in to the combustors and possibly cause a flameout? I'd really appreciate if you answered this because i cant seem to find the answer on google 😂. thank you

Can we get an update on the Iroquois?

The engineering calculations for a mirror-image engine are identical, so there is little additional expense there. The problems arise in the duplication of the manufacturing tooling, and verifying that everything has been correctly mirrored. Then comes the logistical nightmare - you have to make sure "R" versions of parts are not mixed up with "L" versions, particularly when everybody is in a hurry to get an engine back in service. Consequently, because of the added controls to prevent this, inventory and stock expenses are more than doubled. Either that, or they have to be maintained as completely separate engine types.

That would be the Avro CF-100 Canuk Orenda 11s? (i forgot to mention the type of engine the Canunk used.

@AgentJayZ - "Flight quality" engine. Hypothetical - you get 2 exact same versions of the allison/rr 250 in for rebuild, one for a helicopter and the other for, lets say a powerboat or mtt turbine superbike, what differences would there be between the two in regard to parts qualities etc? :)

What about unducted fan engines? Would they need to turn in opposite directions just like propellers do or is there some nature of it being a "fan" that makes that unnecessary?

Do high bypass fans on the latest jet engines have a noticeable gyroscopic affect?

Working for PW I always thought there were 2x version due to gyroscopic, like ethernet twisted pair. Thank you

I’d suspect that the cost to beef up an engine to deal with whatever gyroscopic forces that would be countered/cancelled by an opposite rotating engine would be less than trivial compared to the cost of developing and certifying that engine… though such a thing would be great for punishing a misbehaving logistics specialist. I think Sisyphus would have an easier time completing his task… If having handed jet engines is truly a concern, perhaps some money could be made selling one variant to northern hemisphere clients and the other to southern hemisphere clients and we just won’t mention equatorial clients as they’re just confused. 🤣

I would have guessed more..

What a great video as usual and it is a good question. At about 5:35 Jay says almost all prop engines have a gearbox - it's curious that everybody hasn't jumped on this one. Most are direct drive in fact. I wonder what that statement applies to nowadays - probably commercial planes and larger ICE engine aircraft? And also maybe variable-pitch propellers?

Its easier to keep the engines the same and then you just have to make and maintain a couple of small pipes, which is much cheaper than dealing with wrong facing accessories in an emergency.

It’s called a $90,000 coffee maker that’s how government contracts work👍🏻

❤️‍🔥

18:19 Samsquantch

Interesting that jets rotate in the opposite direction of piston engines from their respective countries. Most American engines, when viewed from the rear, turn counterclockwise. Whereas the turbines turn clockwise. And exactly the opposite for British engine s

There was an April Fool's joke, in the plant newsletter for the Westinghouse plant in Hamilton that produced industrial gas turbines, from the late 1980s or early 1990s. It announced an order to sell industrial gas turbines to Australia. Due to the change in hemispheres, the turbines had to spin the opposite way. Along with bringing a laugh, it sparked discussions on how you would change a gas turbine to run the opposite way. Except for the first and last stages, you swap the stationary blade profiles with the rotating blade profiles. The only engine family with any components that spin the opposite way is the Trent series. The Trent has three nested spools. The outermost spool is the high pressure section, the next spool in is the intermediate pressure section, and the innermost spool is the low pressure section. They realized that spinning the intermediate spool in the opposite direction of the high and low pressure spools eliminated the stator blading between adjacent sections. Eliminating two rows of stator blades in the compressor makes the engine a little shorter and a little lighter, but eliminating two rows of stator blades in the turbine section also save a lot of money, as hot section blading is costly. A shorter, lighter, and cheaper engine that produced the same power for the same fuel consumption was worth sorting out the teething problems of reversing the direction of the intermediate pressure spool.

🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿

So an incredibly silly question of no real importance, if you have a dual spool, or even worse, a triple spool engine, do each of the spools spin in the same direction relative to each other or can/does one spool spin in the opposite direction of the other? ISTM that any argument you could make about it uneconomical for the spool of a particular model of a turbojet engine only being able to spin in one direction, Just Goes Away when you're talking about multiple spools. I mean you could design one spool to rotate in the clockwise direction and another spool spin in the counter clockwise direction and EVERY instance of the engine corresponding spools would spin in the same direct, but that wouldn't affect that one spool in any one engine could be spinning in the opposite direction of the other spool in the same engine. The engine manufacturer would eat the cost of designing different spools spinning in opposite direction only once, and after that, there would be no additional costs relating to the direction of spin of the spools. So what am I missing?

Hello agentJayzulu, Have you heard of the second death of a Boeing whistle-blower? Do you want to share your thoughts, or is that not in your domain of interest?

Most (but not all) R-R engines rotate anti-clockwise (counter-clockwise is an Americanism), viewed from the rear. I say "most" because those engines originating from De Havilland, which ended up being rebranded as R-R , rotate clockwise, viewed from the rear. Armstrong Siddeley and Bristol engines typically rotated anti-clockwise, viewed from the rear. However, the AS Sapphire, which was originally a Metrovick engine, rotated clockwise, viewed from the rear, as did the DH Goblin and Ghost, but not (correction) the DH Gyron. As mentioned by another contributor, the (originally Bristol) Pegasus has contra-rotating spools primarily to cancel out the gyroscopic effect in the hover. Also emanating from Bristol, before becoming collaborative projects, the RB199 and the EJ200 have contra-rotating spools. All marks of RB211 and the earlier marks of the Trent had co-rotating spools turning anti-clockwise, viewed from the rear. However, the latest marks of the Trent engine from Derby, now have a contra-rotating HP spool, relative to the LP and IP spools, reportedly for performance reasons. In contrast, the BR700 series of engines from R-R Deutschland, rotate clockwise, viewed from the rear, possibly because of their V2500 ancestry.