REFLECTOR: Back in the air.

[Hiroo Umeno]

Good thoughts on the mixture.  I didn't mention it in the original post but I did suspect something like that and I kept an eye on the EGT through the flight.  The EGT was generally in line with the rest so I definitely think it is an airflow issue.  I'll have to see if the "rubber seal" under the cowl is leaking or not.

My plane does not have the conventional fiberglass box over the top of the engine.  Instead, the whole upper cowl area is pressurized through ram air from the top NACA and I have metal baffles around the entire top with rubber flaps sealing the gaps between the baffles and the cowl.  If it isn't leaking, I might need an additional arrangement to direct more air over to that corner.  It is interesting that the #5 on the other side has no problems.

Hiroo

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Chuck Jensen
Sent: Monday, May 28, 2007 7:27 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Back in the air.

Hiroo,

It sounds like you are getting some quality time on the bird.  Regarding the hot C#6, of course, it may be a cooling/baffling (well, actually its always baffling, but of a differently type) issue.  However, another possible cause is if you are running rich of peak, #6 by be way leaner than the other cylinders so while they are running ROP, #6 is running right at peak EGT/CHT temps.  Or, if you have engine instrumentation for each cylinder and you are running lean of peak, then perhaps #6 fuel mixture is way too rich.  In this case, as you bring the other cylinders to LOP, it leaves #6 right at peak temperatures.

Air flow/cooling may be the most obvious cause of hot temps, but since its isolated to a single cylinder, there are a couple other possible causes, such as fuel/air mixture to that cylinder.  Just another thought to noodle over.

Chuck Jensen


 -----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Hiroo Umeno
Sent: Sunday, May 27, 2007 9:36 PM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Back in the air.
Yesterday, after many thwarted attempts and frustrating weekends staring at the sky, I was able to bring N21HV back in the air.

Take off was at 1:10pm.  After staying close to Paine to verify that all systems were running temps were in the reasonable range, I took the plane through some "cruise" configuration tests over Puget Sound.  The flight prior to this in September was with the Mid-CG configuration with 60lb ballast on the co-pilot seat and the additional 30lb of lead-shot in the nose.  Yesterday was a aft-CG test without the 60lb ballast keeping the 30lb in the nose, full tank of gas.  This simulates the single-pilot X/C load-out.

Some numbers in case anyone cares<g>.  (Performance data based on data capture from the EFIS)
Take-off Weight: 2011lb (2400 Gross)
Take-off CG: 121 (115 - 121 allowable)
Initial Climb:  1800fpm at 2424ft DA, 2430rpm, 27.5in/Hg on the MAP, 100Kts
Cruise: At 6000ft DA, 2650rpm, 20.6in/Hg MAP, 152Kts TAS, 8.0Gph burn rate.

The plane is currently in the "Dirty, no-pants" configuration where all the aerodynamic trims, fairings, and wheel covers are still off which, I am told, will add another 15Kts or so.  At this point, I haven't been able to test the wide open throttle since the CHT is still running hotter than I would like.  I have 13 hours on the engine so far and my engine guy tells me that it will run hot until all the rings break in.  It does bother me a bit that #6 CHT stays consistently hotter than the rest, though.

I did a somewhat rectangular leg of W10 - BVS - FHR - 0S9 - W10 including some dodging of occasional wispy layers here and there.  Over South Whidbey, I did some low-speed work like MCA, Pitch-Buck, etc.  On pitch-buck, with the CG fairly close to the aft limit, I ran out of the elevator travel at 75Kts and the aircraft settled onto steady, mushy descent.  Noticeable pitch buck never occurred.

Back at Paine, I did a few touch-and-go's, all were fairly good.  On the last landing, (full-stop) I was able to slow the plane down to taxi speed a bit past A6.  If I can consistently nail this one, I can bring my personal minimum runway length to 3,000 from my current 4,000.

Overall, very good flight.  2.5 hours on Hobbs.  13.9 TT airframe cumulative to date.  It's a nice flying machine!


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