Limiting takeoff power (Prop RPM)

Discussion in 'Flight Following' started by James331, Jun 13, 2016.

  1. James331

    James331 Ejection Handle Pulled

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    Anyone limit their prop RPM for takeoff?

    I've heard of some folks clipping a close pin on their prop veainer shaft to limit their RPMs, not a huge fan of actually clipping stuff to my controls, but I did have a few comments when I had to do a go around on my river a few days ago.

    Just a idea of the type of prop noise that I'm talking about.



    Now imagine that over water.


    On one hand not using full power on takeoff seems like a fundamental bad idea, on the other hand I have more than enough room to not need all 300hp.


    Thoughts?
     
  2. mondtster

    mondtster En-Route

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    I'm generally not a fan of voluntary partial power takeoffs...

    I occasionally fly a C206 at a drop zone with some houses near the departure end of the runway. When we're busy on the weekends I'm sure the people get tired of the frequent noise so once I'm established in the climb, clear of the trees, I'll reduce RPM to try and stay friendly. So far there have been no complaints with this procedure, I have full power for takeoff and it will be as quiet as is reasonable when going over their houses. Maybe something similar would work in your case?
     
  3. Ted

    Ted The pilot formerly known as Twin Engine Ted

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    I'm assuming you have the 2850 RPM IO-520 in the 185? That's what the 310 had as well.

    There's some semi anecdotal evidence I've seen that at 2850 RPM the thrust is the same (or lower) as 2700 RPM because of the prop inefficiencies up there, so you could make an argument for that. In general, my opinion is that the extra horsepower is a safety feature and I'm not too interested in reducing my safety, but I've also never gotten complaints (even from 3 AM wheels up times).
     
  4. Cooter

    Cooter Ejection Handle Pulled

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    The big jets do it all the time, but it's a little different in a single engine. I guess it depends on how much reduction is required to have a significant effect, and what impact that has on performance.
     
  5. Ted

    Ted The pilot formerly known as Twin Engine Ted

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    It's very different in the big jets. They have highly calculated runway lengths and "guaranteed" safety margins with the speeds and power reductions used. It's much different in piston aircraft. Lose an engine in a single, you're going down. The higher you are before you have to go down, the more options you have.

    In a piston twin, the equation is also often times bad, especially right after takeoff (where it's sometimes worse).
     
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  6. brcase

    brcase Pattern Altitude

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    At my airport altitude I am usually only going to get 25" anyway, when I only need about 1500' of runway and have 5000, I don't see any reason to run maximum RPM's in planes that makes a lot of noise, So I will usually just set my RPM for my normal climb, often about 2500rpm (I know it is about 6 turns out of the Prop control) and just take off full power but reduced RPM. That way I don't need to make any power changes during the climb out.

    Brian
     
  7. Cooter

    Cooter Ejection Handle Pulled

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    Which is why I worded my post the way I did.;)
     
  8. James331

    James331 Ejection Handle Pulled

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    That's the one, IO-520D.

    If I restricted it, I'd probably have to take it down to 2500 for it to slow the tips down enough to make a difference.

    None of my neghibors have said anything bad, seems like they actually like seeing the plane, I just want to keep it that way :)
     
  9. Zeldman

    Zeldman Touchdown! Greaser!

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    In the C-207 here in Juneau I usually limit the prop to 2500 RPM for take off, unless I am at max gross weight. Keeps the noise down. Density altitude is usually under "0". At full loads as soon as the wheels leave the runway I run the prop back to 2500 RPM. That helps to keep the neighbors from complaining, much. With a very light load I will take off at 25 inches at 2500 RPM.

    Like you, I would not attach any physical limiter to the controls at all.
     
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  10. Stewartb

    Stewartb Final Approach

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    It depends on the temperature. I never use full RPM in cold winter temps. I never limit revs in summer.
     
  11. Ted

    Ted The pilot formerly known as Twin Engine Ted

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    I figured you knew plenty about it, I just wanted to make the post for the education of others. I spent some time in a previous job working on that. :)

    Understood. I was based at a 2800 ft runway right next to a subdivision. As in, I could've had a "through the fence" agreement if we lived there. For the 310, obviously that was relatively short so every horsepower counted in order to keep takeoffs as safe as possible. The airport manager said he never heard any complaints about me, and received very few complaints in general. It was also a pretty sleepy airport, it seems most complaints are at busy airports.
     
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  12. James331

    James331 Ejection Handle Pulled

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    We are similiar to AK, minus the wind, which is more tame.

    My straight away on the river is just over a mile, if needed I can add another 1/2 mile to that on a step taxi to takeoff.

    We're under 500MSL
     
  13. Clark1961

    Clark1961 Touchdown! Greaser!

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    I use "reduced" power nearly every time I take-off. It's full RPM but I back off about 5" of manifold pressure.
     
  14. Stewartb

    Stewartb Final Approach

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    You should go do some takeoff tests at full throttle/flat prop and then at full throttle/2700rpm. See what's what with your plane. Higher revs make for shorter takeoffs for me. One of my favorite float drills is to go to a long stretch and see how little power I can use to get off the water. That's a trim drill more than power but it'll teach you about flying the wing instead of flying the throttle. Take some ballast and move the CG to see how the trim changes. Fun stuff.
     
  15. Stewartb

    Stewartb Final Approach

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    Yikes! Why?
     
  16. Clark1961

    Clark1961 Touchdown! Greaser!

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    Why not? Engine originally rated for 200 hp is now rated 220 hp. Max manifold pressure was originally 41 inches and is now 40 inches. Manifold pressure does tend to climb a bit on its own (bootstrap).

    Home field has 8,000' runway and most of my flights are here in the land of long runways...
     
  17. Stewartb

    Stewartb Final Approach

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    Why not? Fuel flow is important for cooling when using high power. I need all the gas I can push through my cylinders at takeoff (high power/low airspeed) and that last little bit of throttle makes a big fuel flow difference.
     
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  18. 3 in the green

    3 in the green Line Up and Wait

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    Only one of the best sounds, ever, ESPECIALLY over water.

     
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  19. Skip Miller

    Skip Miller Final Approach

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    For those reducing power on takeoff who are flying carburetor engines (i.e., not fuel injected) please remember there is a fuel enrichment circuit built into the carb so that at full throttle, the mixture is made more rich. This fuel enrichment circuit is there for a reason. By using less than full throttle, you are defeating this circuit. Is that what you intend? As StewartB says in the message #17, the last little bit of throttle makes a big fuel flow difference.
     
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  20. James331

    James331 Ejection Handle Pulled

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    Music!

    I think so, you think so, but some non aviation folks can go ether way on it, luckily I live in AG ville
     
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  21. mscard88

    mscard88 Touchdown! Greaser!

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    Music to me ears! :happydance:
     
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  22. bradg33

    bradg33 Pattern Altitude

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    Airplane performance is more important to me than a little bit of noise. The IO520 in my airplane turns 2850 on take-off, and it's loud, but I've never given a second thought to the noise. Best practices, and common sense, call for the use of full power for takeoff.
     
  23. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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  24. RyanB

    RyanB Administrator Management Council Member PoA Supporter

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    Like Bradg33 said, I'm gonna value my available power and performance over the noise it may bring to the folks on the ground. I dont fly amphibs, but it doesn't seem logical to me, taking off without using the most performance I can get. Especially on some of these hot summer days.
     
  25. Dan Thomas

    Dan Thomas Final Approach

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    Might be an STC'd, certified clothespin.
     
  26. 3 in the green

    3 in the green Line Up and Wait

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    What do those go for? 0.8 AMUs? :D
     
  27. txflyer

    txflyer En-Route

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    Fly it like you STOL it ♦
    Full power but I'm running an MT two blade. It doesn't make much noise.
     
  28. pigpenracing

    pigpenracing En-Route

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    I back mine down in the Model 12 when I leave the ground. Full power and 2900rpm is about 46 gallons per hour :)
    It will still climb 3000 fpm backed down to 2400 rpm.
     
  29. Mtns2Skies

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  30. Ted

    Ted The pilot formerly known as Twin Engine Ted

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    My instructor had a clothespin and a rubber band for his Comanche 180.
     
  31. Stewartb

    Stewartb Final Approach

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    Here's a perspective to consider. In winter I fly on and off a 15' ASL creek bottom in temps well below zero. Density altitude might be -6000'. Spin an 86 or 88" prop up full and you'll redefine noise. Use a prop speed calculator and you'll see there's real merit in reducing the RPMs. But what about throttle? Well my fuel system doesn't compensate for temperature but cold temperatures make for dense air and that makes for lean engines. Because of that I'll always use full throttle to maximize my fuel flow and provide a healthy mixture. Full throttle, reduced RPMs. Common practice in the cold. And yes, I know guys that use a clothes pin as a prop limiter so they can push the ball to the wall without thinking about it. No big deal.
     
  32. OkieFlyer

    OkieFlyer En-Route

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    Just a thought:

    Thousands of people take off and climb out in PA-28 140s, everyday getting, say 500 fpm climb rate. Right? If a person in a 182 or 185 or the like can achieve double that climb rate, even with the power pulled back a little, what would the be harm? Seems safe enough, and still way beyond what many less powerful planes can achieve with balls to the wall. I think it's probably not a great idea with high DA, if you need to do a high performance take off, or clear an obstacle. If we're talking normal takeoffs, in favorable conditions, why not?

    I go balls to the wall on every takeoff for a couple hundred feet AGL, so I'm really not trying to make a case for reduced power takeoffs, but this did get me thinking about it. I'm a flatlander though.
     
  33. Clark1961

    Clark1961 Touchdown! Greaser!

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    My engine<>your engine. Can you grasp that?
     
  34. RoscoeT

    RoscoeT Pattern Altitude

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    Noise is about prop RPM, not engine RPM. If you're flying a Pitts 12, that M14 engine is only turning the prop 1900 RPM at 2900 crank RPMs. An airplane with an M14 is the last airplane that'll get noise complaints, no matter what your prop/power setting is. No reason to back it off except to conserve fuel.
     
  35. Ted

    Ted The pilot formerly known as Twin Engine Ted

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    In the twin engine world, the general adage is waiting until 1,000 AGL before doing your first power reduction. The idea being that if you're 1,000 AGL you at least have time to do an identify/verify/feather/figure out WTF to do. What I use for climb power depends on the plane, the weight, the passengers, etc. In the 310 I did full power climbs solo, in the 414 I'm doing full power climbs when heavy (at least so far), but that's for performance.

    In a single, I view it as a bit different simply because if the engine quits, you are landing and you're doing it now. The higher you are when that happens, the more options you have. Now if you're surrounding by fields, who cares? Not a big deal, you land in a field. If you're surrounded by forest or other bad places to land, I'd be a bit more concerned.

    No, it's MY engine. MINE MINE MINE!
     
  36. steingar

    steingar Taxi to Parking

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    I'll take my safety vs. their peace and quite. Boats can be plenty loud too.
     
  37. bradg33

    bradg33 Pattern Altitude

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    Consider this: Runway behind you, fuel left in the truck, unused power in the engine. What do these have in common?
     
  38. Sac Arrow

    Sac Arrow Touchdown! Greaser! PoA Supporter

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    Bro do you even lift
    I've never limited RPM, but I used to limit my manifold pressure to 34 inches (vs. 38 inches full power) in the Turbo Arrow for normal takeoffs, since there was no noticeable difference in performance past 34 inches.

    (Yes I know a normal TA is 41 inches full boost, mine had an intercooler.)
     
  39. pigpenracing

    pigpenracing En-Route

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    You are right... I back the Model 12 down to save fuel. My 540 Powered Christen Eagle was the loudest airplane anyone in this area has been around. It was set at 2900 rpm when I got it and the airport manager complained everytime I took off. The tips went supersonic and was just LOUD! This video is from the guy who built the airplane. He told me he ran it at 3100 rpm. After a 15 minute flight in this plane my ears would ring for 3 days! Finally I found the Clarity Aloft and it helped a bunch.