Mailing List flyrotary@lancaironline.net Message #38853
From: Al Gietzen <ALVentures@cox.net>
Subject: Lessons from yesterday
Date: Tue, 31 Jul 2007 10:50:28 -0800
To: Rotary motors in aircraft <flyrotary@lancaironline.net>

Ok; vague subject, because this is a collection of stuff, and followup on an enjoyable flight.

 

As probably everyone else, I am surprised at Buly’s decision.  As I was flying smoothly along at 195 mph TAS at 5200 rpm; my thought was NO WAY would I give up this rotary in favor of a Lycoming.  I’ll admit that it has taken a great deal of tenacity to get to this point; and there is more to go; but it’s a price I’m willing to pay.

 

Gears

I just wanted to make it clear that in my post the other day, I was not casting dispersions upon the RD-1B and its planetary gears.  I am quite happy with that re-drive and would say its combination of weight, performance and price is the best value out there.  And I also was turned off by Bud’s approach of selling imagined emotional issues.  If he’s going to sell a re-drive, sell its technical merits. Every choice I made in the engine installation I made with safety and reliability in mind (and I have grandkids). His clutch can be a good idea for protecting against torsional resonance; but what is this about the redrive and prop causing excessive starter loads?

 

Oil cooler

 

I put my two manometer ports at the oil cooler inlet to measure dynamic pressure in front of the center scoop, at the underwing surface, and 1 1/8” from the surface (the extremity of the scoop).  At the surface (1/4” tube at the surface) it was +2.75” H2O, and at 1 1/8” it was +8.5”.  Given the earlier measurement of about +9.0” at 5/8” from the surface; my conclusion is that there really isn’t much in the way of a well defined boundary layer.  Rather there is a thicker layer of turbulent air, probably caused by the gear well/gear doors just forward of the scoop.

 

With the tubes taped along the surface in front of the scoop, climbing out from a fresh start had the oil temp was up to 230F by the time I leveled out at 3000’ (OAT was 85F).  After recording the measurements, I landed with the intent to relocate the tubes and get more data – but upon reflection, I decided take off the tubes, put the VGs back on and go enjoy some flying.  Starting with a warm engine, and 190F oil temp at the start of the takeoff roll, I climbed at 1500 fpm to 2500’ (TPA) and then about 1000 fpm to 4500’, where the oil temp peaked at about 217F.  Obviously have those tubes in, and in front of the scoop in recent flights had made the problem worse.  Level cruise at 5000 -5200 rpm had the oil temp around 210F – on the high side, but with the OAT then about 87F, not too bad. Coolant temp was 185F.  I think I’ll just do some further work on sealing up the air leakage around the cooler.  After all; without cowl flaps or other means of control, if I made the cooling much better I’ll have to be concerned about the oil getting too cool when the OAT gets to be 40F.

 

Electrical

 

Chris; I’ll repeat that word again – Tenacity.  I have had continuing issues with the EM2 and EC2 over the two years or so since I got the engine running.  I’d say it is definitely different using them in a composite canard with long wire runs, than in an RV. And there were a couple issues particular to the 20B version. I’ve had to conclude that they are not very noise tolerant.  I made a series of wiring routing changes over that time, and finally added filtering on the circuit board of the EC2.  Right now I’m quite happy with the EC2, and the EM2 just needs a fix to a faulty EGT channel and a change to the FF calibration to adapt to putting the snubbers in the injector circuits.  When they’re working right, they are very nice. 

 

Be careful of running the EM2 wiring bundles, and the push-button switch wires, near any other wiring where there likely to be electrical noise; or near the bundle from the PCM to the EC2 box.

 

Bad news

 

I am going to be grounded for awhile until I can get the FAA straightened out about my medical certificate. R-r-r-r-r.

 

Al

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