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  • Stephen Murphy
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8 months 1 week ago #1251

Hello, I am new to the Forum and am in the process of purchasing a seneca 2. I was wondering if people could share how they are managing their engines during climb and cruise. i.e. LOP/ROP (not to open a can of worms), power settings, fuel flow, CHT, EGT's. Just trying to get a feel for what's normal and help me figure out how to run the engines. Thanks!!

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8 months 1 week ago #1252

Congrats on the Seneca II- I just love that plane!

Ok so here is the way I fly the Seneca II-
remember that is a turbocharged engine and your right hand is the absolute pressure controller.
Mixtures are always full rich above 75% power.
On take off - prop full forward, mixtures full rich= set power to 38 inches. It will ram up to 40 on the takeoff roll. If the over-boost light comes on, back off until it goes out. Hold the brakes until you set take off power then release. only

Climb- above 1000 feet AGL- props back to 2450 rpm- the manifold pressure may increase with prop speed reduction.
Most of the time, this will not cause an over boost. If you have Meryln MAgic waste gates it definitively will not over-boost. There is no need to pull the power back first unless you are consistently getting the over-boost light on prop reduction. reduce manifold to 33-35 inches for the climb. You will loose 1 inch per thousand feet gained so - plan to
arrive at your cruise altitude with 30-31 inches . retard mixture if EGT's drop below 1250 in the climb. 1250-1300 normal EGT in the climb. fuel flow is irrelevant in climb.
Cruise- close the cowl flaps- reduce props to 2300 for normal cruise, 2200 for economy cruise and 2350 for max cruise.
once the props are set- reduce manifold to - 30" mp. 30"mp and 2300 rpm yields 70.5% power at 10,000 feet - lean to 1475 egt and no hotter than 1500. That will yield approx. 11 gph/ side.
plan on 3% power for each inch of manifold and 3% for each 100 RPM.
there is an power setting chart in the flight manual but the above rule of thumb works great.
If im not in a hurry or have a tail wind- 29/2200-
Normal cruise- 30/2300. High cruise- 30.5/2350.
EGTS for all - 1475/not to exceed 1500-

Decent- Probably the trickiest part- Reduce power 3" begin your decent. For every 1000 feet of decent you will gain back an inch. . Wait 60 seconds - reduce power another 3"- repeat-
plan to arrive at your pattern altitude with 20" mp.
Depending on how hot and how heavy and what the density altitude is- 20" in level flight should yield gear speed.
Use the gear as a speed brake- deploy without power reduction. flaps at the white arc- Monitor EGTS- don't push the mixtures up too aggressively- the Seneca doesnt have engine cooling issues like most turbos

Final- flaps approach= Speed - Blue line plus 10 until established on final, then blue line, then flaps full and Blue line minus 10 over the fence- thats going to be around 14 " carry a little power into the flair (10-11"). The Seneca has a known elevator blanking issue in the flair- (totally disappears with he installation of VG's) and carrying a little power give the stabalator enough authority to hold the nose up in a flair with two people in the front seats-


Under no circumstances - for any reason - do I recommend that you to operate lean of peak. It is not an approved procedure for that engine according to the manufacturer. I have had two Seneca customers cook there engines (all 4 of them ) with less than 400 hours total time on them doing just that. Yes- you will burn a gallon an hour less- and go slower- and it can be done. But if you do it wrong- even once- its going to be costly. How many gallons do you have to save to cover the cost of an overhaul? fuel is cheap- and engines are not.

Note: the engines have 8 quart sumps- small for a turbo. I always run 100AW oil- never multi vis. and I always run it full.
If it " blows a little out the breather" it shoudn't. It is likely an oil control ring issue pressurizing the crankcase. However, if you fly high- and I ran mine high all the time- the differential pressure may cause some blow by. Still, you shouldn't see more than a quart every 6-7 hours max.

I hope that answers your questions. I don't know where you are located but if you are east coast- Id be happy to come and check you out in your Seneca! Its what I do! You can call my cell anytime! \

Michael Leighton
561-704-2008

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8 months 2 days ago #1254

Michael,
Wow, thanks for such a thorough run down of how you fly you're plane. I really appreciate it. Just wondering what kind to TAS you are getting up above 10K at those settings. I understand that each plane flies a little different. Going to go look at a nice Seneca next week. Cross my fingers!

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8 months 2 days ago #1255

Well TAS will depend on which props you have on the airplane - 2 blues are faster than 3 blades, whether or not you have de-ice boots , boots cost you 5 knots , and if you have any speed mods on the plane .
My 2 blade - non deiced- Aeneca with all the speed mods trued 177 knots at 10,000 feet at 30.5/ 2300 rpm.
My fully de iced 3 blade Seneca only saw 167 knots at the same power and altitude.

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