On Jul 2, 2004, at 11:43 PM, Ed Burkhead wrote:
Stephen,
a. A 415-C must have 13° of up travel
Plus or minus 1/2", per Service Manual p. 27.
Fred Weick had no reservations whatsoever about operating the Ercoupe 415-C design at 1400 lb. gross under the postwar CAR 03 rules (effective December 15, 1946) since it was designed to earlier, more stringent rules substantially similar to the later "utility" catagory. This is documented in that the Service Manual (revision still sold and used) dated January 1, 1947, lists in the back the first 415-D but has no different rigging instructions for same while in the front, p. 9 lists an "Allowable Gross" (normal category)" of 1400 pounds** (** Subject to CAA Approval).
b. A 415-D must have 9° of up travel This ain’t so bad – that’s what I had and it worked just fine – your touchdown speed raises by about 5 mph – no big deal. Additionally, the extra limit on the elevator keeps you from having the slipstream push down the tail so far that, with the increased gross weight, you get into a stall that is too aggressive and might let you spin.
Unfortunately, the new regulations arbitrarily decided that "When it is desired to designate an airplane as a type 'characteristically incapable of spinning,' (which did not exist, for practical purposes other than the Ercoupe) the flight tests to demonstrate this characteristic shall also be conducted with (in part) an available up-elevator travel 4º in excess of that to which the elevator is to be limited by appropriate stops". Accordingly, there is no liklihood whatsoever of spinning from an "aggressive stall" at 1400 lbs and 13º up elevator...that's what the plane passed it's tests demonstrating!
To pick a nit, the slipstreat IS still "pushing down on the tail...but the reduced area in the center of the "split elevator" means PART (don't forget the effect of the engine's sidethrust on an otherwise "straighth back" propwash pattern) of the highest velocity propwash has much less to push against.
c. All models from 415-E onward have the split elevator and 20° of up travel. The main difference in this is the cutout in the elevator to let the slipstream pass with little effect on elevator trim. This gives the plane little trim change from full power to idle. If you trim it for 75 mph at cruise, it’ll stay close to that at full power and at idle. With the slipstream NOT pushing down on the tail, having extra power is no problem because the slipstream can’t push the tail down – so you can’t get into too aggressive a stall (or spin).
It's legal FOR THAT AIRCRAFT!
3. Engine
Check the paperwork of the airplane – the form 337. These (when signed by the FAA) are the legal documents for the plane’s modifications – often called “one time STC”. If the FAA signed off on a change, it’s legal.
I’ve only heard of the crank-changing engine upgrade in a couple of casual discussions in recent years. Apparently someone had this good idea and got someone to approve of it. It sounds like a good idea. If you have a form 337 approving that engine change, it’s legal.This isn't an engine change. The STCs allowing use of the C-90/0-200 crank, rods and pistons in rebuilding a C-85 (since new cranks are either unavailable or expected to be so soon) make it clear the resulting engine is still regarded by the FAA as a C-85.
4. Model changes
a. You MAY NOT carry more than 1260 lb. as long as the plane is a C model.
b. You must convert it to a D to carry 1400 lb. The specifics to do this are authorized by the aircraft type certificate. Follow the type certificate’s requirements and the change is legal.
Follow Ercoupe Information Letter No. 1 in doing so.
Aircraft Specification A-787 governs all models except the C....except the C and CD!
c. According to the FAA type certificate person I talked to, it’s not *possible* to convert a plane from one model to another unless that change is specified in the type certificate. In this case A-787. A change from an earlier model to an E is not possible, I was told.
This FAA person advocates a point of view contrary to ERCO (again, see Ercoupe Information Letter No. 1) and unsupported by applicable fact.
http://edburkhead.com/Ercoupe/index.htm (scroll down to the bottom of the links)My recommendations:
d. However, you can change it to BE a 415-D and have the legal 1400 lb. gross weight then submit a form 337 to change the elevator to the split elevator to be “like” an 415-E. (All the change to be “like” an E gets you is the 5 mph slower touchdown speed and less trim change when you change power.)
1. Accept the fact that you have a C-85. You cannot "convert" this engine officially to an 0-200. (The C-75/85 cam will give more power with the longer, more efficient prop. Have your C-85 prop "tweaked" for 2575 rpm at about 120 mph, or for maximum climb, your choice)
2. Get a split elevator (you also need the "low speed warning spring, etc.) IF your local FAA acknowledges EIL No. 1. I can provide serial numbers of Ercoupe 415-Cs active on current FAA registry which they now list as converted to 415-E models. You can get the 337, etc. for each for $5 from the FAA to satisfy the local inspector.
The only STC you need you already have (if your engine rebuild is legal).
Regards,
William R. Bayne
<____|(o)|____>
(Copyright 2002)
Ed,
Spent some time with the airplane, asking some more specific questions.
It's placarded (if that's a word) as a C model. The engine is 0-200 in a C85 case, I've found where there are STC's to do this, so that you retain the same motor mounts, etc. No problem with the engine, the problem comes in with typical FAA crap. There is no STC on record to go from a C model to 0-200. You have to first be a D. Well, I don't want the 9deg elevator, so I'd have to do split tail, and get to an E (are you as lost as I am???).
I THINK I can have a C85 STC'd 0-200, and a C model brought up to an E (giving me 1400lb gross, and a 12deg elevator, but have NO IDEA how to start. Any clue?
On one hand, the worst case is I fly an 0-200 C model, KNOWING that it's really good to 1400#, but it's uninsured if I fly it over 1200#. At $17k purchase price, I'm not concerned with the insurance. BUT the engineer in me wants everything to be "by the numbers". Any clue where can I go to find the process to make the C model into an E with a C85 to 0-200 conversion?
I THINK I would:
1. Buy the STC to go from C to D, restricting the elevator to 9 degrees, and requiring the stainless fuselage section. Add the stainless fuselage section. At this point, I only have 1200# gross.
2. Buy Skyport's STC to put an 0-200 in a D model (the work is already done).
3. Buy the STC to go from D to E, (I'm not sure who holds this one) requiring the split elevator, but going to 13 degree elevator, and upgrading to 1400# gross.
Is this right?
I could be reading / understanding this completely incorrectly. What the airplane currently is = a C model with a C75 converted to an 0-200 during a complete overhaul, by changing the crank, carb jets, etc. I just want to find the best way to make it "legal", and find out what that would cost.
OR could I go "Like Model D" redo the cowling, buy the Skyport 0-200 STC, and then go "like model E", and have the elevator modified?
Any ideas?
Stephen.
