My 1968 Cessna Cardinal

New modifications, cowl


Cowl modifications:

I bought the aircraft in Texas, outside of San Antonio. The weather was overcast, cold and freezing level was rather low also.

On my way back to Southern California I noticed the speed was rather low...around 110ktas approximately.

When I got back I decided I wanted to see how much faster I could make the aircraft go. I decided to buy most of the available STC’d kits and have them installed by my mechanics.


I bought several kits from a company in Canada called “Maple Leaf Aviation”. They specialize in Cessna modifications and specifically the Cardinal. The developer of the Kits, Roy Sobchuk, has done a great job and all the parts fit with minor adjustments.

The first one I had installed is referred to as the fixed cowl flap. The original cooling air exit of the early Cardinals is actually just a big hole at the bottom of the cowl. Some air actually enter through this hole and reduces the pressure differential between the plenum and the lower cowl and it is very poorly designed. The cooling drag is quite big and I would assume that with the original configuration, the cooling drag itself is about 35% of the aircraft total drag. This is quite a bit, but it is not uncommon for small aircraft like this. The fixed cowl flap covers the exit hole and provides a smooth exit for the cooling air plus increasing the pressure differential and thus provides better cooling...this later on proved to be a little challenge. More about that in the performance section.

Here are some pictures of the original exit hole, although not on my aircraft:

















The fixed cowl flap was installed and I also installed the exhaust tube fairing. The exhaust tube fairing also reduce the drag, both external and cooling drag.

Here are some pictures of the installation on my plane.





























Cooling inlet modification

I wanted to reduce the cooling drag even more and I purchased another kit from Maple Leaf. This one is called the “winterization kit”. The original purpose was to use is in colder climates since it supposedly increases the cylinder head temperatures. It didn't change any of my temps, but it lowered the induction drag a bit.

This is how the original cooling inlets look like:















This is how the inlet kit looks like unpainted















And here it is painted and also with some modifications to the baffle system in order to maximize efficiency and minimize drag.