T6/Harvard power settings

[Ken Dwelle]

I used to use 2000/30" for takeoff due to the reduced noise level for the airport neighbors. Both of our T-6's are Reno racers and will climb at 1800'/min at that power setting. After reading Randy's article and talking with some high time T-6 guys I have been using 2250/36" on Takeoff for the last couple of years. I'm not sure I buy the power enrichment argument as the throttle is nowhere near the forward stop at 36". In any case I climb and do acro at 2000/30".

There is some room for discussion on cruise power settings as the engine operation chart in the back of the Dash-1 calls for more MAP than most guys seem to use. I generally cruise at 1850 and 26-28" and lean until it stumbles then go two clicks fwd on the mixture. This gives 28GPH and 165 Knots true, again ours are faster than stock. I use 2000 rpm in the pattern and lean 2/3 back on the ground to keep the plugs clean although this may be an old wives tale!

Ken

[Hvd2Pilot]

WOW! This is great response guys. I've been mostly concerned with overboosting in cruise & climb, but it appears as though others are using higher power settings with no problems.

Keep the input coming!!!!

Drew

[retroaviation]

Retroaviation, awesome looking machine... way to keep a yellow one that clean! I've heard that's not an easy task.

Thanks Vessbot. I know I sound like a broken record to many folks here, but that is the first airplane I ever built. We flew it between 100-130 hours per year (first flew in December 1995), and it still looks the same today. A good maintenance program, some decent paint, a little soap and water, and pride in your airplane, will result in a safe, good lookin' machine, for a long time. Just spent the last year of my life trying to convince a bunch of people that very argument.

Hvd2Pilot, to touch on your "overboosting" comment you made, that yellow airplane I posted pictures of had an interesting change during it's life where overboosting was kind of an issue. You see, when I built the airplane, we installed a standard R-1340-AN1, with a 10:1 blower in it. A number of years later, it was time for a new engine. This airplane was typically in the "outside" position during a three-ship aerobatic act (during barrel rolls, "crazy loops," etc.), so a 12:1 blower was installed in the new engine to try to help make it "more responsive" at the higher altitude airports, at the top of a maneuver.

Well, as it turns out, the big blower did help at altitude, but it didn't really do much to help during the formation acro. Actually, it became quite easy to overboost the engine, when not at high altitudes. It was amazing to me that after all those years of flying the airplane with the stock blower on it, how "sensitive" the big blower was with throttle movement. We all found ourselves to be smooth and deliberate in standard formation flying, but during the acro, when getting "sucked" during the last third of a barrel roll, you tend to have more agressive throttle movements. With the small blower, that wasn't an issue, but the big one could really push the manifold pressure up there. And no, we weren't watching the manifold pressure gauge while in the manuever, myself and several other people would watch it from the back seat during practice sessions.

Now, with all of that being said, we never caused any harm to the engine by doing this on occassion. As a matter of fact, I believe that same engine is still installed on the airplane today...dunno for sure though. Anyway, the lesson learned was that with the bigger blower, you had to use much more finesse with the throttle than with the smaller one.....especially at Sea Level or lower altitude airports. I think I can speak for the owner when I say that the big blower wasn't necessarily a good purchase. The stock setup on a T-6 works well, unless you're gonna go up "high" for long cross country flying.......and since that's no fun, who wants to do that??????

Gary

Gary

[Trey Carroll]

I asked long-time warbird pilot Frank Strickler if he could comment on what I had posted earlier in this thread... Here's what he has to say, which I fully believe in.

No, your pistons will not be cocked, crooked, off center, unbalanced, etc. The issue if one of piston ring seating. High BMEP keeps rings seated and does not allow for "piston ring float" (or slap or flutter or whatever else one wants to call rings rising and falling in their ring grooves)


"Under square" is a term often misused and misunderstood. Note any "unboosted" engine will run its entire life "under square".


Probably the largest benefit of full power take off and climb is that of fuel enrichment which allows cylinders already enjoying higher air flow to run even
cooler for even less time.


The Pratt is noted for its capacity to deliver 1" of MAP at 1850 rpm for each gallon of fuel consumed. ie. 20" = 20 gallons/hour, 25" = 25 gallons.


At pattern speeds the air plane will not "push" the prop and there needs no worry wasted.

Hope this adds to our conversation! I'd be interested to hear more of the T-6 drivers thoughts on the topic.

Tailwinds,
Trey Carroll