You will use a flight manual supplement that updates specific sections, primarily weight and balance. All other information from the original manual remains unchanged. If the aircraft is operated in the Utility category, the supplement does not apply.

No. The gross weight is provided as a straight-line variation between stations. A graph example is included in the supplement.

The conversion is based on the 1983 Cessna 172Q. While many components are similar, the 180 HP engine installation requires different propeller components, airbox configuration, and engine baffle modifications.

The battery box on 24 volt N model airplanes needs to be moved for left magneto clearance. The instructions and pictures are usually self explanatory and I do not get many questions on it. We do not supply any parts for the box relocation. They need to get their own aluminum angle and rivets.

The oil cooler needs to be moved to the firewall location if it’s not already there. Most airplanes have it on the firewall but a few may have it on the right rear baffle. The oil cooler lines, fittings, and hoses supplied are for the firewall installation. The kit does not contain any required parts to relocate the cooler. They need to get the angle aluminum and oil cooler chimney.

Yes, They will need to modify the original engine baffles to fit the A4M engine. They need to cut and fit the baffles to the engine contours as described in the instructions. Some customers go to a Airforms in Alaska and buy replacement baffles. They make some baffles but they are not PMA and must be installed as an owner produced part. We don’t get many questions on fitting the baffles as it’s a straight forward process. The SH-2 throttle cable bracket is produced by us and I don’t usually get any questions on that. It’s usually bolted on and it works. One leg of the bracket is held on with one of the carburetor mounting nuts and can be tricky to get installed due to the way the carburetor body is cast. The Avstar carburetors are much easier to install as they have much more room in that area. .

The carburetor airbox is one of the most asked about parts of the STC. Most airboxes are old an worn out before they even start to modify it. If they need a new airbox they must order the original airbox for the aircraft and modify it. No other airbox will work. I get questions about using the AirPlanes STC airbox and it will not work nor is it legal for them to use. The SH-2 adapter is installed on the airbox by first cutting of the original carburetor adapter for the MA4SPA, riveting the new airbox adapter after centering it over the carb heat shaft, and then opening the hole to match the new adapter hole for the larger MA4-5 carb. Depending on the airplane model there are two different airboxes that were used. A long airbox and a short airbox. The short airbox is connected to the cowling by a short hose and the air filter is on an adapter connected to the cowling by a short hose. I don’t get many questions on this airbox. The other is a long airbox that sits in an opening in the cowling. In addition to the SH-2 adapter there is a forward bracket that connects to the front of the box and the starter, alternator mounts to support the front of the box. This bracket needs to be modified also. I have attached a picture of what they need to do.

The original exhaust system is the same as what was removed from the engine except for the left hand exhaust risers, #3 and #4. The O-360 is 1” wider than the O-320 so they need to weld the SH-2 exhaust extensions to the end of the pipes. This keeps the outlet of the muffler in the same location where it exits the cowling. If they do not want to use the extension or if they need to replace the pipes they can order the #2 and #4 risers for the 172Q and they will be the correct size for the Superhawk installation. If they need a muffler or pipes for the #1 and #3 side they order the original part numbers for the airplane.

You will need to modify the front and rear bulkhead to install the propeller. The bulkheads need to have the propeller bolt holes enlarged for the larger bolts and the rear bulkhead needs to have the dowel pin holes relocated for the Sensenich propeller which is not a problem. Most questions are about cracked spinners. The Sensenich propeller is wider than the McCauley propeller and when they install the spinner the rear bulkhead spinner attach holes do not line up. They install the spinner then pull the backplate forward to install the screws. This leaves a lot of stress on the backplate and spinner and then one or both crack. The instructions say to use a rubber mallet to form the bulkhead around the propeller so the screw holes line up without putting any stress on the bulkhead or spinner. This is a step that is usually skipped and then a few months later it cracks. They will have to order the spinner and backplate that originally came with the aircraft and then modify them. They usually do not have the instructions.

Yes. The flap travel needs to be adjusted to restrict them to 30 degress maximum. This is done for the increased gross weight of the aircraft. This is a simple adjustment on most of the airplanes. There is a flap stop that is adjusted on the flap motor in the wing by loosening with an allen wrench sliding the stop. On early 172K and L model airplanes they need to remove the flap motor and install a floatplane flap stop P/N: 0500417-1 which we do not supply. I do not know much about the installation of this stop. I’m not sure how many of these airplanes are out there but I get very few calls about this installation.

The airspeed indicator needs to be remarked on I-M series aircraft. The markings are in the flight manual supplement for the applicable model airplane. They can send the indicator to any instrument shop along with the Supplement and they can remark it. We used to include this in the Superhawk kit but the shop we used closed when he retired. It was easier and less headache for us to let them do it for themselves.

Yes. Aircraft must be equipped with 6-ply tires due to the increased gross weight.