McCulloch J-2 progress

[J-2 Skyfarer]

I am happy to report that my McCulloch J-2 N4315G is finally going back together after exhaustive inspections and necessary refurbish/repair of all components on the rotorcraft. I am lucky to have a local A&P who owns and and flies a Hiller Model D. He took a genuine interest in the J-2, which was a real boon to the project. My machine is certified, and I intend to keep it that way. I owned and flew N4320G for 120 hours back in 1986, and I look forward to getting back into the air with 4315G. I will keep you posted and perhaps send some photos.

 

[All_In]

Wow, awesome ride and news!!!
Please do post pictures... We love videos too, hint!

 

[robhodgman]

Yes, please post pictures!!!

 

[J-2 Skyfarer]

Work on my J-2 restoration has made a great leap forward with the first spin-up of the rotor, which was quite smooth. My A&P owns a Hiller, so he is sympathetic to rotory-wing owners. There is much more to do on the machine, but a lot of it is cosmetics (upholstery, etc.) I am looking forward to the first flight. I am planning to fly my longtime friend, Si Smith, down to Texas to give the machine a good inspection before the initial flights. I bought my first J-2 from Si back in 1986, and he taught me how to fly it. Here's a recent photo of my first taxi to the gas pumps to get fuel.

 

[Cresco750]

Getting close now!

 

[J-2 Skyfarer]

A couple of recent photos of progress on N4315G. As you all may know, the horizontal stabilizer on the J-2 is fabric-covered. Mine suffered from severe "ringworming" and factory-old paint. My mechanic suggested that we remove the fabric and thoroughly inspect the stabilizer frame, which is all aluminum. Sure enough, the trailing edge had about a 4-inch section of corrosion. My mechanic, who is skilled in fabric work, repaired that section and recovered the stabilizer. I have decided to leave it with its doped finish rather than apply paint to it. With proper maintenance and care, the stabilizer should last another 40 years. The rotor head was in very good condition when I bought the machine (the log book says it has 97 hours on it). We inspected, cleaned, and serviced the three hydraulic dampers and torqued them by the book for proper lead/lag movement. The first rotor spin-up was very smooth.

 

[WaspAir]

Cool. You may find after more hours that vibration and air loads on the stab cause some wear on the trunnions, well before the fabric raises concerns again.

 

[J-2 Skyfarer]

Cool. You may find after more hours that vibration and air loads on the stab cause some wear on the trunions, well before the fabric raises concerns again.

Yes. I believe you are correct. The trunnions that were on the machine were in very good condition and very snug, so we cleaned them up and reused them. I also have a pair of what look like new-old-stock (unused) trunnions in reserve. In any event, I will keep an eye on the stabilizer.

 

[WaspAir]

Great! Parts like that are becoming precious these days, as you are undoubtedly aware, so it's nice to have some already in hand before they are needed.

 

[okikuma]

Is the J-2 rotor head originally from a Hughes 269?

I've always held the impression that it is and they only difference were the rotor blades.

Wayne

 

[MikeBoyette]

Yes and the blades are untwisted.

 

[GyroCFI]

It's very very close, but I don't believe parts are interchangeable. The friction disks in the dampeners are different I believe if my memory serves correctly. They were both designed by Drago Jovanovich a few years apart. When I sold my Super J-2 back in the early 90's it had several brand new transmissions, rotor heads, teleflex control cables and I think a new set of blades, etc... Unfortunately there were some time-limited parts that were a real pain to change like the main rotor bearing at 300 hours, so not a real practical machine, but I loved flying mine!!

 

[okikuma]

Too bad one cannot "STC" a different set of rotor blades. With the current 26' diameter rotor disk (530.93 sq ft) and a 1600 lb gross weight. The disk load is a dismal 3.0 lb/sq ft. With a 30" diameter rotor, a 2.26 lb/sq ft disk load. With a 34' diameter rotor, a 1.76 lb/sq ft disk load.

Wayne

 

[WaspAir]

I used Schweizer-Hughes pitch links on my Super J-2, and some other bits without difficulty. It's the old style vertical axis cans for the dampers, not the horizontal can style of the later models.

Drago used the same basic head on everything, including his tandem rotor helicopters, the JOV 3 and the McCulloch MC-4.


https://images.app.goo.gl/HQpfx1AKC1C8RrzL7

 

[J-2 Skyfarer]

It is my understanding that this particular rotor head was designed by Drago Jovanovich specifically for the J-2 gyroplane and that Hughes then purchased the design for their TH-55 and 269-series helicopters.

 

[MikeBoyette]

Too bad one cannot "STC" a different set of rotor blades. With the current 26' diameter rotor disk (530.93 sq ft) and a 1600 lb gross weight. The disk load is a dismal 3.0 lb/sq ft. With a 30" diameter rotor, a 2.26 lb/sq ft disk load. With a 34' diameter rotor, a 1.76 lb/sq ft disk load.

Wayne

Yeah Dad and I talked about imagine how good that thing would fly with a set of his big blades on it.

 

[WaspAir]

Yeah Dad and I talked about imagine how good that thing would fly with a set of his big blades on it.

Were those symmetrical airfoils? I assumed not, but for a 500 rpm prespin, you really want zero lift at flat collective pitch.

More mass would have made it intentional-jump capable. Maybe some 35 foot diameter wide-chord Parsons-built blades as on the 18A would satisfy the critics. I enjoyed mine as it was.

 

[MikeBoyette]

Were those symmetrical airfoils? I assumed not, but for a 500 rpm prespin, you really want zero lift at flat collective pitch.

More mass would have made it intentional-jump capable. Maybe some 35 foot diameter wide-chord Parsons-built blades as on the 18A would satisfy the critics. I enjoyed mine as it was.

No they were not however Dick Degraw has no problem using them on his machines for doing jumps. The smaller blades are used on the Mosquito helicopter with no problems.

 

[GyroCFI]

I remember a particular time flying my Super J-2 in the winter when I was light on fuel, by myself, and it was pretty cold out. The J-2 did jump a few feet in the air when I pulled collective. was a great ride that day!

 

[okikuma]

Here's a link to an earlier J-2 thread I started back in 2020.

Wayne

https://www.rotaryforum.com/threads/mcculloch-j-2-gyro-plane-by-jim-griffin.1145693/