Props don't counter rotate?

[Diesel_Thunder]

Probably a silly question, but I am used to seeing twin prop aircraft with counter rotating props. P-38 being a prominent example. In the pre-order video, I noticed that both props rotate clockwise.

 

Are the props on the Mosquito supposed to both rotate clockwise, or counter rotate?

[Bozon]

Like all (AFAIK) Merlin driven props, they are rotating clock-wise from the pilots point of view. This means that they induce a counter-clock ("left") roll as torque increases.

 

edit:

Also, left yaw on takeoff runs.

It also means that flying on just the left engine or just the right engine is different.

Edited August 16, 2021 by Bozon

[Flamin_Squirrel]

While both engines are running the torque cancels out (even without counter-rotating engines), so no left yaw on take-off. It's only when you get into single engine operation things change.

[Hartsblade]

38 minutes ago, Flamin_Squirrel said:

While both engines are running the torque cancels out (even without counter-rotating engines), so no left yaw on take-off. It's only when you get into single engine operation things change.

I don't think this is correct. In this video, starting at about 8:05, Kermit Weeks describes the engine torque on takeoff and how he would manipulate the throttles to counter it

 

[Flamin_Squirrel]

Hmm. That makes no sense to me, but then I've only flown a light twin, nothing that big. Interesting either way, thanks.

[grafspee]

37 minutes ago, Flamin_Squirrel said:

Hmm. That makes no sense to me, but then I've only flown a light twin, nothing that big. Interesting either way, thanks.

It makes sense for me, he was talking of gyroscopic precession during tail lift, when both props spins same way it will be massive.  

Another thing about mossie is that behind the engines there is no tail, so prop wash don't affect tail, until mossie get some speed it has near zero rudder or elevator authority, so initial roll is stabilized with engines power.

Edited August 19, 2021 by grafspee

[Flamin_Squirrel]

But this isn't a single with the torque acting around the longitudinal axis. The right engine will want to rotate the CofG aft/counter clockwise, the left engine will want to rotate the CofG forward/clockwise.

 

If what Kermit says means I'm wrong then I probably am, but if I am this is more complex than it might seem on the surface. In fact my book on flying twins specifically says the following: "In a twin, the [torque] reaction is largely negated until one engine fails".

Edited August 19, 2021 by Flamin_Squirrel

[rkk01]

4 minutes ago, Flamin_Squirrel said:

But this isn't a single with the torque acting around the longitudinal axis. The right engine will want to rotate the CofG aft/counter clockwise, the left engine will want to rotate the CofG forward/clockwise.

 

If what Kermit says means I'm wrong then I probably am, but if I am this is more complex than it might seem on the surface. In fact my book on flying twins specifically says the following: "In a twin, the [torque] reaction is largely negated until one engine fails".

 

Yes, but is that for a modern counter-rotating pair?

[Flamin_Squirrel]

No.

[Krupi]

8 minutes ago, rkk01 said:

Yes, but is that for a modern counter-rotating pair?

 

Correct, the gyroscopic effect of the props will want to push the aircraft in the same direction unlike counter rotating.

 

I have read and this gentleman repeats that the pilots note's tells them to "lead with one engine" to reduce this effect, really the tail plane was too small to cope with the power of the merlins.

Watch from ~2:50
 

 

Edited August 19, 2021 by Krupi

[zcrazyx]

i've watched various videos including the ones linked, the method seems to be don't use full power till the tail is up, use differential throttle and also if i remember correctly dont fly below 160mph unless landing. 

[Swagger897]

Torque does not cancel out in non-counter rotating multi engine aircraft, it only remains the same or becomes amplified based upon engine power or airframe design. There’s a reason why multi engine trainer aircraft use counter-rotating designs and that’s to allow students an easier time to grasp the fundamentals of multi engine flight. It’s sole purpose (counter rotation) is to reduce the gyroscopic effect. Such aircraft like Piper Seminole, Aztec, and others follow this design. 
 

In the case of the Mosquito, and any other non counter rotating multi engine aircraft, if the right engine goes out in flight, one would need to immediately feather prop, left rudder pushed (dead engine, dead leg), and apply appropriate power. 
 

Anyone unaware of multi engine flight really needs to take a look at some decent instructional videos to get a decent grasp of things, or else this aircraft will easily bite you and quickly that too. 
 

edit: 

 

 

There, already done for you and it’s right at 60s long. The aircraft fractured here is a Beechcraft Duchess, Beechcraft’s attempt at a light twin trainer. It features the counter rotating design as well which eliminates the critical engine like mentioned above. 

Edited August 20, 2021 by Swagger897

[Flamin_Squirrel]

Yes it eliminates the critical engine, but that's only a factor in single engine flight.

 

There's engine torque, P-factor, gyroscopic precession, and slipstream, none of which are acting around the same pivot point, so it's not as simple as just adding these factors together.

[Bremspropeller]

48 minutes ago, Flamin_Squirrel said:

Yes it eliminates the critical engine, but that's only a factor in single engine flight.

 

In theory, yes. However, there are departures from that case:

On the P-38, either engine is critical, as the both engines' descending blades are outboard of the nacelle.

They had to go for that configuration on the 38 because of buffet with both engines rotating inboard. (IIRC)

Edited August 20, 2021 by Bremspropeller

[grafspee]

So conclusion, left hand tendency in Mosquitos due to P-factor, once tail goes up it should roll pretty straight. 

Slip stream not a factor, mosquito don't have tail behind engines.

Left engine is critical engine.

Edited August 20, 2021 by grafspee

[Flamin_Squirrel]

2 hours ago, grafspee said:

So conclusion, left hand tendency in Mosquitos due to P-factor, once tail goes up it should roll pretty straight. 

Slip stream not a factor, mosquito don't have tail behind engines.

Left engine is critical engine.

 

 

Yeah P-factor is the only thing I can think of that might be an explanation.

 

Been a good learning experience this thread. Disappointing the training documentation I have is misleading (although to be fair they probably didn't have 4,000hp taildraggers in mind!)

[rkk01]

Just read an account of a 157 Sqn pilot who lost the port engine on take off…

 

100-150’ AGL, 140-150mph.

 

Managed to belly land at a nearby USAAF airbase

[Swagger897]

8 hours ago, Flamin_Squirrel said:

Yes it eliminates the critical engine, but that's only a factor in single engine flight.

 

There's engine torque, P-factor, gyroscopic precession, and slipstream, none of which are acting around the same pivot point, so it's not as simple as just adding these factors together.

 

You've completely missed the topic at hand though and it shows you've done no research or have enough knowledge on the topic itself. Until you correct yourself you've already dismissed any further debate of the matter with your opening reply to OP:

 

On 8/19/2021 at 9:18 AM, Flamin_Squirrel said:

While both engines are running the torque cancels out (even without counter-rotating engines), so no left yaw on take-off. It's only when you get into single engine operation things change.

 

Torque does not cancel out with non counter rotating twins, as originally stated it only remains just as difficult to control, or if not worse, than a standard single. THE reason for counter rotating twins was to cancel out this torque effect. 

 

I'd highly recommend reading this article to have a better understanding and to stop spreading further mis-information, as well as outright denying factual evidence and experience by those who thoroughly understand the topic: https://www.pilotscafe.com/engine-inoperative-principles-in-a-twin-airplane/

Particularly the point of the ascending and descending blade theory which produces more thrust. 

[Mogster]

It’s interesting that apparently the Westland Whirlwind had L and R handed RR Peregrines but the Mosquito made do with R handed Merlins.
 

It seems RR wanted to turn out as many engines as possible and the leanest way to do this was to simplify production wherever possible. Part of the reason for the Whirlwind’s cancellation was RR wanting to reduce the number of work streams in its factories so the Merlin was chosen over the Peregrine. The Mosquito having R handed only Merlins must have been viewed as a compromise worth making early war although L and R  Merlins clearly had advantages as the Dh Hornet had them later. 

[Flamin_Squirrel]

6 hours ago, Swagger897 said:

THE reason for counter rotating twins was to cancel out this torque effect. 

 

How? Draw a diagram showing how the moments will achieve this.

 

Take some of your own advice, because you don't understand this as well as you think you do.

[grafspee]

8 minutes ago, Flamin_Squirrel said:

 

How? Draw a diagram showing how the moments will achieve this.

 

Take some of your own advice, because you don't understand this as well as you think you do.

As far as i know counter rotating props remove critical engine

Edited August 21, 2021 by grafspee

[=475FG= Dawger]

8 hours ago, grafspee said:

As far as i know counter rotating props remove critical engine

 

This depends on how they counter-rotate. If they counter-rotate inwards, then there is no critical engine. If they counter-rotate outwards, then they both become critical with respect to defining the critical engine as worse case scenario (descending blade outboard on the operating engine)

On 8/19/2021 at 8:18 AM, Flamin_Squirrel said:

While both engines are running the torque cancels out (even without counter-rotating engines), so no left yaw on take-off. It's only when you get into single engine operation things change.

This is wrong.

Edited August 21, 2021 by =475FG= Dawger

[=475FG= Dawger]

9 hours ago, Flamin_Squirrel said:

 

How? Draw a diagram showing how the moments will achieve this.

 

Take some of your own advice, because you don't understand this as well as you think you do.

Both engines are always applying a rotation force to the airplane opposite the direction of the propeller rotation. If they are rotating in opposite directions, the forces are in opposition and cancel each other out. If they rotate in the same direction, the forces are cumulative.

[Swagger897]

9 hours ago, Flamin_Squirrel said:

 

How? Draw a diagram showing how the moments will achieve this.

 

Take some of your own advice, because you don't understand this as well as you think you do.

The website I linked already has this shown in its images. 

 

Just goes to show the lack of maturity to take any criticism when proven wrong multiple times. 

[Flamin_Squirrel]

9 minutes ago, Swagger897 said:

Just goes to show the lack of maturity to take any criticism when proven wrong multiple times. 

 

 

The conversation was fine until you showed up. You've done nothing other than mud sling and cite articles you don't understand. Don't bother replying to anything else I say, because I'll simply ignore you.

 

Edited August 21, 2021 by Flamin_Squirrel