165 Franklin Cruise RPM

D

dtreid

New member
What do you guys with the 165 Franklin and Aeromatic like to run you cruise RPM at?

Some of the info I've read say the the Franklins like to be run on the hard side which I'm assuming would be 2600rpm.
 
Harvey Leydecker (RIP) said he always ran his hard. Not sure what RPM, but 80% power wasn't unusual. He told me Frankies have closer tolerances than Lycoming or Continental.
 
I figure at around 5500ft I'm running mine at best 70% at 2600rpm. Sounds like I'm not overdoing it.
 
I have spoken to Kent Tarver about the 2650 redline on several occasions. He assures me that it does not need to apply to the Cruisair and 2800rpm is just fine.
 
David, you must understand that Kent hates the FAA. If you or your IA think you have more authority than the TC for our airplane , then good luck. I have serious doubts about the 2650 redline, but try to argue that when the TC of our plane says it clearly. Any IA that signs off your plane with a 2800 red line could easily loose his ticket. I like Kent, but he would rather argue than accomplish the things we need for the Aeromatic. My IA says that he has the test equipment to tell if the higher RPM is a real problem, but it is expensive and the FAA would probably not pay attention anyway. The FAA is here to help us. !!!!OH REALLY!!! ______Grant.
 
The problem then is that the TCDS still says that you need to red line your tach. We are flying Certified planes in the US, and picky as it is, you still need the proper markings in your aircraft. The same limitation is also on the Stinson TCDS with the 165.
I am not saying how you may adjust your prop, but I can't help but wonder why that limitation is there. There is an incredible amount of stress put on a prop.
Guess that is the neat thing about this...we each get to decide. In our case in the US, we still have to comply with the FAA requirements.
 
My feeling is have the IA...Inspecting Engineer, in Canada read both the engine and airframe data sheet, make a best decision on the marking. Put the marking on the instrument.
You the operator/owner of the aircraft can choose to abide by the marking or.....
Everyone is happy.
Kent has assured me that previous engineering data on the various parts of the Aeromatic have a safety
factor of nine.
When I got the T14-14 from Harvey Leydecker years ago, he had the Aeromatic set so that it would turn just short of 3000 rpm. It took all day to get that corrected. Anyway, the prop is still together and flying.
Dan
 
Larry, where is there a difference in the hubs for the Aeromatic on a Cruisair? I am aware of the High Cruise, but I have not seen where that changes the red line for the 165 with the Aeromatic. My IA has the equipment available to test props for vibrations (he does Kingairs) but says it would be multi thousands of dollars , and the FAA probably would not accept the data anyway. My IA hates the FAA almost as much as Kent does, but he can usually work with them. Even with proper testing, any approval would probably be for the individual airframe/engine/prop . I cant imagine the difficulty of getting a TC change when nobody really has owned the TC for the last half of a century. I think the only options are to stick with the TC or be an under the radar experimentor. Just my 2 cents worth. ______Grant.
 
I am fortunate enough to have my Cruisair under 'owner maintenance' category in Canada. Essentially experimental.
 
Maybe I asked the list historians already how the 165 Franklin managed to be on the Cruisair14-13's tcds in the first place since it was not ever manufactured with one. As I recall, the 165 engine showed up on the cruisair tcds around 1970 or so, long after it was out of production and orphaned. Was this a gracious act by the FAA? I suppose then, that that hidden hand could also apply the 2650 rpm limit as well.

From the torque curves of the 150 and 165 it looks like the two engines have about the same power at 2300 rpm but the 165 torque is rising there and peaks at 2650 or so. Actually at 2600 rpm the 165 is only putting out about 153 HP. The rest of the 165 rating is the 200 rpm rating difference. Soooo, it looks like a 165 needs to be buzzed up a bit to have any appreciable power advantage over a 150.

Yeah, 2500 or 2600 rpm WOT at cruise altitude seems about right to me. I should mention that the prop tip is at about mach .8 at cool cruising altitudes running 2600 rpm, and the Aeromatic blade tip section is not happy there. So some efficiency penalty applies over a metal prop (which there are no choices for a Franklin 165 Cruisair anyway).
r
 
There was one multiple STC for metal props on 165, and possibly one other. We have discussed this here before. Like most Cruisair STCs the owner of the STC is long dead, and there seems to be no way to revive these orphaned (but valuable to us) STCs. I dont know how we have to abide by a TC that has not been owned for 50 years or so, but we cant abide by STCs that are no longer owned. I talked to Eric Preston ( great photographer) a few months ago, and he thought there was a law change coming that would allow us to use orphaned STCs, but I have not seen any reference to it. Maybe something will get better in the future. I sure hope so. ______Grant.
 
I have posted before that I have a letter from the owner of one of the McCauley STC's giving me permission to use the STChowever I want. If you need a copy of his note, along with a note from me giving you permission to use the STC, let me know.
Larry Lowenkron
 
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