Sopwith Pup - Rotary engines and loose cowlings

I thought this might be of interest .

I've been following Kermit Weeks exploits with his collection of aircraft in Florida on Youtube for a while but this video brings up a few things things that have a modelling relevance too.

There's a bit on rigging his New Zealand Vintage Aviator built replica Pup, I think Kermit confuses his wash in and wash out ?? but interesting to hear it is rigged with neither . He also poo poos the idea of the Camel turning faster one way to the other from his experience of flying one.


The video includes the maiden flight of the Pup after an extensive rebuild, it was badly damaged in a hurricane along with several other of Kermits aircraft. Unfortunately the cowling came loose in flight. I think Kermit used up a large amount of his luck with that one

I am not sure a rotary engine aircraft actually turns faster one way than the other but it was certainly safer for an inexperience pilot if the gyroscopic forces tended to push the nose down rather than up. Lifting the nose in a tight turn is a good way to initiate a spin which at the time was considered a dangerous manoeuvre, hence the saying "it turns faster one way than the other".

My 'Boy's own' knowledge of rotaries was that the Bentley BR2 as fitted to the Sopwith Snipe was considered the end of the line in rotary engine development largely because having a large rotating mass on the front of the aircraft produced a number of drawbacks including the torque making the nose rise when turning right and drop when turning left. A tighter turn to the left sounded logical too and potentially difficult to handle. I suspect poor fuel efficiency and total loss lubrication didn't stand up well against the likes of the water cooled RR Falcon etc , helped end the rotary's rein as well.

Quorneng wrote: I am not sure a rotary engine aircraft actually turns faster one way than the other but it was certainly safer for an inexperience pilot if the gyroscopic forces tended to push the nose down rather than up. Lifting the nose in a tight turn is a good way to initiate a spin which at the time was considered a dangerous manoeuvre, hence the saying "it turns faster one way than the other".

You've got it the wrong way round Q. It was safer to turn a rotary powered aircraft to the left where the gyroscopic precession kept the nose up, rather than to the right when the nose went down. In the days when the rotary was the preferred engine, aircraft were turned using the rudder rather than the ailerons. Accordingly, if a right turn was initiated after take off, then the nose down couple would often cause a crash, ergo, the preferred turn direction was to the left. I believe this is why, to this day, the preferred circuit direction at most airfields is to the left.

in flight, the nose up couple associated with a boot full of left rudder caused a much tighter turn than the nose down couple associated with a boot full of right rudder, so the aircraft 'turned better to the left'. Modern pilot's fly aircraft using the bank-and-yank technique, so the aircraft turning ability would be similar in both directions except that the precession causes a nose down yawing moment when turning left and a nose up yawing moment when turning right. Paradoxically, this is opposite to the accepted flight characteristics experienced in WWI, but it also serves to explain Kermit's comment on turns.

Don't be too rigid regarding the nose up/down gyro effect - it depends on which way the engine rotates! They didn't all go anti-clock when looking at them from the front!

Eric wrote: Don't be too rigid regarding the nose up/down gyro effect - it depends on which way the engine rotates! They didn't all go anti-clock when looking at them from the front!

But most of the rotary engines did go anti-clockwise when looking from the front, Eric, that's why the left turn after take off was mandated.

Is the torque effect of rotating mass( engine) anti clock in the same direction as an anti clock rotating fixed engine? I've never been sure about that. Or does the mass pull in same direction as that of rotation.

OT
The torque is created from driving a propeller. It doesn't matter what type of engine is driving it. The resulting torque tries to bank the plane in the opposite direction to the prop rotation.
The gyroscopic effects come from the rotating masses. The prop itself acts a gyro as does the crank shaft in a radial engine but in a rotary the engine the rotating mass is not only a great deal heavier but also at a larger diameter so it creates a much more significant gyroscopic effect.
There is no gyroscopic effect in straight and level flight but in a turn it will tend to raise or lower the nose. The strength of the the gyroscopic force depends on the speed of engine rotation and the 'rate' of the turn.