More aviation questions 1

[rlc747capt]

I have an airplane with a Continental O-470-R, 230 HP Engine. I want to install a Continental IO-520-D, 300 HP Engine. I suspect I would have to modify the Engine Mounting and Firewall, but how much and can I calculate it?
The O-470-R weights 378 lbs to 495 lbs
The IO-520-D weights 419 lbs to 478 lbs
Maybe I want to install the IO-550, 310 HP Motor, so I will need a more substantial mount and firewall attachment.

Any clues and math to back it up would be appreciated.

Thanks.

 

[aviat]

There is a lot to conversions. First is the a/c a type certified or homebuilt? If the a/c has a tc you will need to go to its TCDS and see if the engine and propeller combination you want to use has been approved for that TC. If not then it is a major alteration and you would require a STC. It would probable be much cheaper if you could find someone who has already gained an stc and purchase it off him or her. To get an stc you have to test the engine and prop and a/c as a unit, doing vibration tests, flight tests, noise tests etc. It can be an expensive proposition.

Even if it is a homebuilt there are several things to consider beside the engine. Often you need a larger dorsal fin and sometimes a larger V-stab/rudder. Your engine mount could change with the prop installed. For instance, in the c185 the mount is different with a three bladed prop than with a two blade. As for the strength of the firewall structure it often works out that it has to be strengthened for a lighter engine.


You will have to determine if the increased performance is worth it. You are increasing the power by 30% but you will not get that much increase in A/S. It might be like 10%, with an increase in fuel flow. However, if you are after an increase in rate of climb putting in more power helps a lot. You can use the simple calculator below show a rough guide to the increase in A/S.

I have just scratched the surface to what’s required. You should obtain the services of a DAR for detailed information.

http://www.sacskyranch.com/velocity.htm

 

[Michaelah]

What you are proposing, may be considered a significant project by the FAA Small Airplane Directorate. If you will post the aircraft model, I can give you a fairly detailed response. The main items to consider, are performance, structural strength, powerplant interface and noise under 14 CFR Part 36. If this is a US registered aircraft, over 6,000 lbs, the changed product rule may apply. If so, you might well have to show compliance with modern amedment of 14 CFR Part 23.

anyway, let me know what aircraft you have got and I will take a shot at it.

Later

 

[rlc747capt]

Michaelah,

Thanks. Cessna 188, Cropduster, with an O-470-R, upgrading to IO-520-D . . . 230HP to 300HP (310HP possibly).

 

[Michaelah]

rlc747capt,

I down loaded the TCDS, Number A9CE, for your aircraft and what you propose should be fairly straight forward. It sounds like you want to convert to a A188() or a T188C. The T188C was not required to show compliance with 14 CFR 23.221 (spins) and as such you would end up in restricted category for the 310 hp conversion. Now the AGwagon 300 meets all applicable requirments of part 23 so you will be able to operate in normal category.

The simplest approach would be to verify that the fuselage from the firewall aft to the wing attach point is the same for the A188() vs the 188. If so, then confirm that the engine mount for the 188 is the same as for a A188(). If not , you will need to aquire an A188() engine mount.

This approach to certification is based upon a "Similarity" argument and should allow you to avoid expensive analysis and flight testing. If the fuselage is the same, I would have an A&P mechanic with an IA approach an FAA Flight Standards ASI to see if they will permit a field approval. Explain to the ASI that you are converting from one approved aircraft configuration to an other approved configuration. In this way you can reasonably claim that this is a minor change (if any) to the aircraft type design under 14 CFR 21.93. 14 CFR 21.95 will allow for minor changes in type design to be approved by field approval (FAA Form 337).

I will be out of town from March 2nd through the 14th and won't be checking this web site until I get back. If the FAA ASI agrees with the minor change in type design argument, I will walk you throught the rest of the process. If the FAA insists on calling this an STC project, the cost most likely will be to great for a one time approval.

Mike

 

[rlc747capt]

Mike,

Thanks for your input . . . Darn, I used an example that was too easy. I am more interested in the mathematics. If an aircraft with one firewall and engine mounting setup intends to be upgraded to accommodate a larger more powerful engine, then what formula would I use and what extra bracing or steel tubing would I use. Let's say, I would put a 400HP Turbine Engine or whatever. A fellow has approached me with an RV8 and wants to do two things, increase the Aspect Ratio, I suggested Winglets and increase Horsepower, but I will be darned if I can prove it on paper that my ideas are workable.

I have had no less than 9 Field Modifications to a Cessna A188B approved, first time, by the FAA. I know what I can do and what can be done. If you could point me in the right direction, I would appreciate it.