Kind of long response, but I hope you'll find it interesting. Ed Larry wrote: > > Hey Ed, > I'm curious about the performance with the 7146 prop. What's your rate of climb?
It's been too long since I measured it accurately with a stop watch.
It's better than most "Er"coupes but less than Alons. I measured these
things accurately once but I've lost the documents.
> Top indicated airspeed?
If I push to the firewall at 2000 msl, I get about 104-108 with the tach
just touching the red line. Sorry I can't remember this better, I don't
do it much.
Lately, I've considered cruising it at the firewall and letting it
spin. This is on the theory that, with such a flat prop, it won't be
straining the engine any. I've had at least 20 A&Ps and AIs tell me
"let it spin" though I've generally been too conservative to do so. I
also rarely putter around at low rpms. Puttering around I do at
2300-2400 rpm.
> What about level flight? How fast cruise, at what RPM?
I've historically cruised at 2400 rpm @ 5.4 gph (book says that's
maximum recommended cruise and what do I know?). At 2400 rpm, I get a
VERY well measured 100 mph true at 2,000 feet msl.
> What about your top RPM? Does it over rev with the 46" prop?
I'd have to be in a slight dive to go over red line on the tach. In
straight and level cruise, it just touches the line. Static runup is
exactly at the max rpm specified by type certificate A-787 for the C-85.
> I've never seen a reference to a 7146 before. Is it approved?
For everyone's information, (this is interesting):
--------------------------------------------------------------------------
--
A-787
Propeller and Propeller Accessories
4. Fixed pitch metal, McCauley 1A90CF or 1B90CM
Eligible on Models M10, A-2, A2-A, 415-D (per NOTE 4(b)), E, G, F-1,
F-1A
Static r.p.m. at maximum permissible throttle settings:
For models 415-D, E or G, not over 2225, not under 2025
For models M10, A-2, A2-A, F-1, F-1A, not over 2375, not under
2250.
No additional tolerance permitted.
Diameter: not over 71 in., not under 69.5 in.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- -
NOTE 4(b)
Item 4, 6 or 7 propeller and additional ERCO baffles (P/N 415-40487
left and right;
415-40488, one; 415-40597, two; 415-40598, two) installed.
--------------------------------------------------------------------------
-
<end quote>
Not a word about the prop pitch measured in inches. The limit is based
on real, measurable numbers as measured by the tach. My tach was checked
and is very accurate.
My prop meets these requirements to a "T". I assert it is fully legal.
> What prop did you have on before the 46?
It was the same prop but I don't know what pitch. When I was having my
big engine major overhaul and wing recovering, I got the prop
overhauled. We sent it up to a regional prop specialty company, then my
mechanic called me saying the shop was asking what the pitch was
supposed to be. I stretched my memory and told him 7146. Right or
wrong, I've been pleased with the results.
Do you know how many Coupers have amazed me by saying they've never been
over 5000 msl? With my history of airsickness, I do a LOT of cruising
above 8,500 feet in that perfectly smooth air. Before they changed the
transponder rules, I did a lot at 11,500 and 12,500. Climb out still
seems weak to me after my initial training in a 172 with no others in
the plane.
But, when I went mountain flying to Reno and Minden, Nevada, and the
great Northwest, I could easily cross the major mountain ridges at 2,000
feet over the peaks. I crossed Salt Lake City at 12,400 feet and got a
surprised reaction from the approach control and the airliners in the
pattern below me. It does take a while (an hour?) to get up there,
though. The scenery is better down in the passes, though. But for
safety, I like high.
With the ability to go high, I can follow the methods in Stick and
Rudder's chapter on high thin air "There's Gold In Them There Hills!"
At high altitudes, LEANED, I can get fuel burn down to 3.5 gph at nearly
100 mph true (given no adverse winds). I can sometimes flight plan 350
mile flight legs. Iowa to Connecticut with two fuel stops. (Better not
drink anything till you start the descent.)
I'm personally inclined to recommend pilots who fly in high, thin, hot
conditions to give away some cruise speed for the extra safety of a
climb prop. It looks to me like, if you meet the Type Certificate
rules, you can get the extra advantages and disadvantages of a pretty
flat prop. My home fields may be at or below 1,000 msl, but I'm big
enough that I'm always at the max gross limit of 1400 lb. for my 415-D
and this prop makes me happier.
May I suggest that responses on subjects other than "Flat,
super-climb-prop performance details" be given their own new subject
lines.
Thanks to all. I'm really looking forward to all the facts, details and
opinions that this brings out of everyone's brains and books.
--
Ed Burkhead
Peoria, Ill.
Ercoupe N3802H, 415-D
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