Advice on STC for Newbe

[Olddude100]

Hi, hope this is ok to ask here., I am trading my Cessna 170 for a C 180B
The question is, it's O_470J has been replaced by a IO-470L. The 470L has been derated to the same power as the J model 2600 RPM to 2450 RPM. Why?. I can see a cheeper STC complince but can anyone maybe have another reaon? The prop can take the higher RPM. About 30HP increase.
Thanks for any input..

 

[Olddude100]

Can't edit a post ????
i was asking this more twords a airfram question ranter then a engin question. I am sure there is no engin limitations.

 

[CoffinsCorner]

I am guessing here, but could this be related to propeller torque effect?

Usually the propeller is turning clockwise, as viewed from the pilot. This imparts a tendency for the aircraft to rotate counterclockwise (i.e. left wing downwards). This rotation must be counteracted by moving the ailerons. Maybe there is an aileron trim limitation, and incresing this limitation would require an additional mod (more cost) to the ailerons?

 

[Olddude100]

Thanks, there is something I did not think about -torque- other then engine mounts. But book says only a few mins at full power.

 

[dgapilot]

Might also have to do with the requirements of CAR 3.112(a)(2)Longitudinal trim under the following conditions (i) During climb with maximum continuous power at speeds between Vx and 1.4 Vs1

 

[Olddude100]

Help me understand that CAR. The 180B has no Longitudinal trim. And it does require a lot of right rudder on takeoff which will affect the Longitudinal axes.
Maybe at full throttle with the 30 more HP in a stall could result in a spin easer.
I'm just guessing and wondering why not allow the 30 * hp and use it for very short fields only if needed. In AK so a lot of off airport work or fun.
Thanks for the info..

 

[Olddude100]

The AC is sold so I guess this does not matter anymore. Should have been faster...