# Engine offset

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#### slociviccoupe

##### Well-Known Member
Glad to see all the input. Thank you all for it.

#### Dan Thomas

##### Well-Known Member
As I mentioned before my plane needs significant left rudder in glide, which just seems wrong when making left turns in the traffic pattern, since we've all been schooled against using rudder to make skidding turns in the pattern... even though in my case the rudder is needed to keep the ball centered.
The typical airplane that needs right rudder in the climb will usually need less right rudder, not left rudder, in the climbing turn from climbout to crosswind in the circuit. New students sometimes have a hard time with that.

Until someone develops an affordable (meaning piston) engine that doesn't create a spiralling slipstream or has a prop that produces a torque reaction and whose downgoing blade pulls harder in a climb, we're just going to have to learn to deal with it.

Lots of down offset reduces the downgoing blade problem. The Ercoupe had lots of down-tilt on its engine, probably to reduce the pull to the left in an airplane that had no rudder pedals. But in cruise that engine is pulling the airplane downward a bit. More drag on the wing.

#### slociviccoupe

##### Well-Known Member
May sound dumb but does the opposite rotation of the prop counteract torque of the engine? Ive noticed this on direct drive airboats will torque to one side and the ones with gearboxes with prop rotation opposite the engine dont have this issue as much?

Could it be a good thing?

#### pwood66889

##### Well-Known Member
"The Ercoupe had lots of down-tilt on its engine, probably to reduce the pull to the left in an airplane that had no rudder pedals. But in cruise that engine is pulling the airplane downward a bit. More drag on the wing."
Correct you are, Dan. The downward pull is not that much, given the problems engine offset solves. And one notes the rudders are outside of the rear-ward flowing prop blast, so there is more to the coupe than just fritzing with the motor mount. Another Ercoupe fact is that the FAA never issued a Production Certificate. Each one had to be flown by an authorized (FAA? Can't remember) pilot before issued an Airworthy Certificate. My take is that the exact rig could not be dialed in good enough to just push em out the door by 1946.

#### Rockiedog2

##### Well-Known Member
HBA Supporter
I always set mine on zero xero whether geared or not and offset the rudder
I meant to say offset the vertical
I like it setup for cruise meaning zero offset in the mount and a little offset in the vertical and then rudder as required for climb/descent. And likely a small tab as req for fine adjustment.
That should be an airplane that flies like I like. Why would we try to minimize the need for rudder?

#### Dan Thomas

##### Well-Known Member
May sound dumb but does the opposite rotation of the prop counteract torque of the engine? Ive noticed this on direct drive airboats will torque to one side and the ones with gearboxes with prop rotation opposite the engine dont have this issue as much?

Could it be a good thing?
The roll caused by propeller rotation won't be reduced by any gearbox. The torque reaction is caused entirely by the aerodynamic drag on the propeller.

The only time a geared setup might notice less torque reaction is on initial RPM increase, with the prop's torque reaction countering the engine's block torquing against the crankshaft's mass as it accelerates. Once the RPM is stabilized there'd be no difference between the geared setup and a direct-drive affair.

#### Rockiedog2

##### Well-Known Member
HBA Supporter
When I flew a VW powered airplane for the first time I kept telling myself on take-off, "Left Rudder, Left Rudder". After a few flights I didn't have to think about it.

Right Pops. The need for rudder(or any other flight control) should be intuitive; no thought required. I think that would be called “behind the airplane”. Which we all are at first.

#### Rockiedog2

##### Well-Known Member
HBA Supporter
The roll caused by propeller rotation won't be reduced by any gearbox. The torque reaction is caused entirely by the aerodynamic drag on the propeller.

The only time a geared setup might notice less torque reaction is on initial RPM increase, with the prop's torque reaction countering the engine's block torquing against the crankshaft's mass as it accelerates. Once the RPM is stabilized there'd be no difference between the geared setup and a direct-drive affair.
Yessir
And on my Rotax 912 geared motor I had to learn that when there was a need for power, say to counteract sink on approach, the normal amount of power increase that we are used to with a direct drive motor isn’t near enough. We need to give it about double. I think the actual number is 2.43 which we don’t really care much about; just make the motor make a lot more noise than we used to. Eventually your hand and ears will learn what’s about right.

#### Dana

##### Super Moderator
Staff member
The typical airplane that needs right rudder in the climb will usually need less right rudder, not left rudder, in the climbing turn from climbout to crosswind in the circuit. New students sometimes have a hard time with that.
Yes, though I was talking about the descending turns, downwind to base and base to final.
The Ercoupe had lots of down-tilt on its engine, probably to reduce the pull to the left in an airplane that had no rudder pedals. But in cruise that engine is pulling the airplane downward a bit. More drag on the wing.
I believe the downthrust was to reduce pitch changes with power on an aircraft that had very limited pitch control. You don't want the plane to pitch up when power is added on a go-around when it's supposed to be incapable of stalling. You see that on free flight model airplanes, too, where there's no pitch control... on an airplane trimmed for best glide you'd have a violent pitch up under power unless there is significant downthrust.

[/QUOTE]
...on my Rotax 912 geared motor I had to learn that when there was a need for power, say to counteract sink on approach, the normal amount of power increase that we are used to with a direct drive motor isn’t near enough. We need to give it about double. I think the actual number is 2.43 which we don’t really care much about; just make the motor make a lot more noise than we used to.
More RPM, maybe, by that 2.43 ratio or whatever it is, and more noise perhaps, but not necessarily more power.

#### Rockiedog2

##### Well-Known Member
HBA Supporter
Dana said
>>>More RPM, maybe, by that 2.43 ratio or whatever it is, and more noise perhaps, but not necessarily more power.

come on Dana you know I'm 99% pilot and mostly speak pilot speak. Whoever heard the instructor yell "Add rpm!!!" or "add noise!!!" It's always been "add power!!!"

Reminds me of when I was living with #1. Gotta get it perfect.

#### Pops

##### Well-Known Member
HBA Supporter
Log Member
Joe-- You crack me up.

Reminds me of when my daughter was a student pilot. She was flaring to land, the instructor said " Don't land, Don't land". So she go's to full power and starts climbing out. The instructor said , " What I meant was to hold the main wheels off as long as possible".

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#### BBerson

##### Light Plane Philosopher
HBA Supporter
More RPM, maybe, by that 2.43 ratio or whatever it is, and more noise perhaps, but not necessarily more power.
How would a 701 pilot add RPM and noise and yet not get more power?

#### Rockiedog2

##### Well-Known Member
HBA Supporter
Joe-- You crack me up.

Reminds me of when my daughter was a student pilot. She was flaring to land, the instructor said " Don't land, Don't land". So she go's to full power and starts climbing out. The instructor said , " What I meant was to hold the main wheels off as long as possible".

that cracked me up Pops

#### Rockiedog2

##### Well-Known Member
HBA Supporter
How would a 701 pilot add RPM and noise and yet not get more power?
I don't know BBerson. It's some technical s**t that Dana's into. I didn't even bother to try to think about it.

#### slociviccoupe

##### Well-Known Member
Just to prety much end my post plans came last week and engine has no offset.