Help me understand these two controls...

[LAdamson 240]

Honest.. I love this stuff. I'm a CFI, and I really enjoy teaching... So, I'm not trying to be argumentative, nor a smart-alec :( But.. you're STILL not getting it... :(

I'll always argue with CFI's..................and sometimes I'm right! :( In the meantime, I'll research this farther, since I'm not getting a full consensus one way or the other. There would seem to be variables when it comes to available engine power, etc.In the meantime.............what causes lift? Is it pitch for speed or throttle? Or both? LOP or ROP? B) L.Adamson

[Brett_Henderson 5]

Oh lordy.. let's not get into THAT debate.. Does Bernoulli or Newton make an airplane fly (now I'll never sleep)

[Guest KenS]

Jim,I don't Know if your question was answerd, but if the controls you refer to are for a TurboProp AC then the condition lever is for speed control of the jet engine. It runs at two speeds and the middle detent is generally ground idle and the upper detent is flight idle. The RPM lever is to limit the maimum speed of the prop(s). The throttle is essentially a prop pitch control.This is a somewhat simplified explanation and I hope it helps.Have a good day and happy flying.Ken

[Tim Arnot 5]

This is true.. that's why we're not to allow the prop-rpm/100 to fall below the MP in inches.. I.E. 25"/2500 (25/25) is OK.. but 25"/2300 is bad. And the engine will let ya know it... it will vibrate and even "buck" a little.That's the old, "square it off" method ( 23/23 24/24 25/25 ).

Nope. That's an old wives tale, and is refuted by Lycoming and many POHsFor sure there are MP/RPM combinations that set up bad resonances and need to be avoided, but these are usually stated in the POH, and it's not a general principle to say 23"/2300 bad. If it's in the POH you can fly it and expect it to work (our club Tobago POH allows for 24.4"/2350 as a 75% power setting). Similarly if the POH says don't fly it...

[rpowers 5]

I need to jump in here because this has never been clear to me.When I take off I have throttle and pitch all the way forward.Is this correct?If so when I reach altitude which do I pull back first,throttle or pitch to get proper RPMS?Thanks,Ron

[Brett_Henderson 5]

Nope. That's an old wives tale, and is refuted by Lycoming and many POHsFor sure there are MP/RPM combinations that set up bad resonances and need to be avoided, but these are usually stated in the POH, and it's not a general principle to say 23"/2300 bad. If it's in the POH you can fly it and expect it to work (our club Tobago POH allows for 24.4"/2350 as a 75% power setting). Similarly if the POH says don't fly it...

23"/2300 is not bad.. it's perfectly "squared", which is ideal. And, 24.4/23500 (24.4/23.5) is pretty darn close to squared ( 0.9 difference). Every engine/prop combination is different.. Turbo-normalized engines have they're own scales and MP/RPM relationships.The rule of thumb is no wive's tale.. High MP + low RPM is bad. Call Lyc up and ask them what happens if you fly a C182 at 28" / 2300RPM (if you can even do it). Now.. obviously, at takeoff and into a climb, you can run 28" at 2600 RPM.. but that most DEFINATELY is hard on the engine. If you leveled off at 3000msl and cruised like that, you cut the engine life WAY down.Here's the "rule": If it's in the POH, you can do it. But you won't find any settings in the POH where the settings are more than 1 or 2 units apart. Sans POH, the rule is, you "can" do what ever the engine won't complain about.. again.. you won't get more than a unit or 2 apart before problems start. And even brushing the edge of that is counter-productive. Even IF the engin doesn't balk.. you ARE putting undue stress on it AND the prop.

[Brett_Henderson 5]

I need to jump in here because this has never been clear to me.When I take off I have throttle and pitch all the way forward.Is this correct?If so when I reach altitude which do I pull back first,throttle or pitch to get proper RPMS?Thanks,Ron

Yes.. that's correct. You want max MP and max RPM for takeoff. As soon as the climb is established, it's good practice to back prop-RPS back just a tad.. The slight reduction of RPM add up over the hours of takeoff power settings. In a non turbo-charged airplane; the MP will take care of itself. It will fall off as altitude increases. All you need to do is to make sure the difference between MP and RPM never get too large.In fact.. using a C182 as an example.. if your flight will have you cruising above 6000msl, you'll firewall the throttle at takeoff.. and never touch it again (assuming a direct climb to altitude). At aprox. 6000msl, full-throttle will give you 23-24" of MP.. which is right at most cruise settings.As for which to do first ? For accelerating or climbing; adjust the prop first. Like.. if you're cruising at 23/23.. increase RPMs first, so that the MP doesn't get too high above RPM.Conversely.. as you descend.. pull the power back first..

[LAdamson 240]

Here's the "rule": If it's in the POH, you can do it. But you won't find any settings in the POH where the settings are more than 1 or 2 units apart. Sans POH, the rule is, you "can" do what ever the engine won't complain about.. again.. you won't get more than a unit or 2 apart before problems start. And even brushing the edge of that is counter-productive. Even IF the engin doesn't balk.. you ARE putting undue stress on it AND the prop.

One thing for sure, is that numerous rules and POH standards are getting thrown out the window. Running lean of peak is a good example. Lycoming has been dead set against it, but facts keep emerging that it's great. Lycoming has even backed down a bit in regards to what's in their manual. On the subject of running the C/S prop at full foward to gain the fastest speed; I brought this up this morning during breakfast with a few pilots who own constant speeds. The general thought was, that pulling the prop back a bit would yield the highest airspeed. But there was no proof since none of us run our engine/prop combos that way...................because fuel consumption would be on the high end.However, after reading several prop & speed reports with various RV's that we fly, it seems apparent that these particular aircraft DO fly faster with the prop at full foward. The bottom line for us, will be to try it.. :( edit: Turns out by chance, that this subject just came up on our RV builders forums. First guy say's to run the C/S prop at full throttle and 2700 max rpm to find the fastest airspeed. The next guy says "not so", as his prop's happy place is around 2600 rpm. Then the third guy say's he agrees with reply number one. :( L.Adamson

[Brett_Henderson 5]

Don't just love the ambiguity ?We can filter through it all though.. because (unless there's some sort of malfunction).. a prop at its the highest RPM, held AT that RPM because of its pitch.. WILL yeild the most thrust. This isn't opinion.. this is physics... LOLAnd yeah.. POHs are filled full of liability dodging "errors". The last Bonanza POH I read, called for NO flaps during short-field takeoff. A coiuple years ago, a heavily loaded Bonanza crashed after failing to climb..We (myself, several pilots (one a Bonanza owner), another instructor, a 30,000 pilot) all agree that the POH is wrong.. We watched video of the fatal takeoff attempt, and the consensus was that a notch of flaps would have saved the day.

[Brett_Henderson 5]

I should add, that some high-time engines end up with their torque curve altered a bit. If the engine's red-line is no longer the peak of that curve, then indeed a slightly lower RPM could yield more thrust,, because the twisting power being greater means that the blade pitch needed to "govern" that twisting force, could yield more thrust.. but this is not the norm (and probably a sign that an overhaul is called for)

[Geofa 108]

Don't just love the ambiguity ?We can filter through it all though.. because (unless there's some sort of malfunction).. a prop at its the highest RPM, held AT that RPM because of its pitch.. WILL yeild the most thrust. This isn't opinion.. this is physics... LOLAnd yeah.. POHs are filled full of liability dodging "errors". The last Bonanza POH I read, called for NO flaps during short-field takeoff. A coiuple years ago, a heavily loaded Bonanza crashed after failing to climb..We (myself, several pilots (one a Bonanza owner), another instructor, a 30,000 pilot) all agree that the POH is wrong.. We watched video of the fatal takeoff attempt, and the consensus was that a notch of flaps would have saved the day.

As a former Bonanza owner of 11 years I can confirm the POH is correct-it does better with no flaps for a short field takoff.I was based at a short runway of 1800 ft. for 5 years with 50 ft. trees on either end and did a whole day of experiments with someone on the ground measuring takeoff conditions with and without flaps. Without flaps worked much better. I was surprised myself.

[Brett_Henderson 5]

That's the type of experience shared, that make forums great.. ThanksIn this case though.. it wasn't a matter clearing an obstacle.. This was an armchair analysis of a takeoff that never should have happened.. It was a matter being able to get up off the pavement, into ground effect and then accelerating to Vy. This guy just ran out of runway before he could that, and his attempt to climb as pavement ran out, turned into a departure stall.After lots of talking.. obviously the REAL consensus was that the airplane was over-loaded for that runway (his home runway no less). And we decided that a notch of flaps would have gotten him climbing.. or, at the very least, off the ground soon enough to see that this wasn't gonna work, with an aborted takeoff / runway over-run as the worst case.Our conclusion was.. " IF we were flying a heavily loaded Bonanza from a short runway (obstacles not a factor).. a notch of flaps would be our choice" .

[Geofa 108]

That's the type of experience shared, that make forums great.. ThanksIn this case though.. it wasn't a matter clearing an obstacle.. This was an armchair analysis of a takeoff that never should have happened.. It was a matter being able to get up off the pavement, into ground effect and then accelerating to Vy. This guy just ran out of runway before he could that, and his attempt to climb as pavement ran out, turned into a departure stall.After lots of talking.. obviously the REAL consensus was that the airplane was over-loaded for that runway (his home runway no less). And we decided that a notch of flaps would have gotten him climbing.. or, at the very least, off the ground soon enough to see that this wasn't gonna work, with an aborted takeoff / runway over-run as the worst case.Our conclusion was.. " IF we were flying a heavily loaded Bonanza from a short runway (obstacles not a factor).. a notch of flaps would be our choice" .

I think I saw that video. I agree-it might have helped-though a short runway, overloaded, and high density altitude is a recipe for disaster. At the small field I was at-if it was over 75 degrees I would have to fly to the class c airport with long runways 5 miles away to pick up my passengers.

[Brett_Henderson 5]

Hey.. I found a Youtube of the crash.Take a look when you have time.. http://www.youtube.com/watch?v=gOaAZ1i2gNAEDIT: Oops.. I posted after your reply.. Regardless, it's great discussion fodder.

[Geofa 108]

Hey.. I found a Youtube of the crash.Take a look when you have time.. http://www.youtube.com/watch?v=gOaAZ1i2gNAEDIT: Oops.. I posted after your reply.. Regardless, it's great discussion fodder.

Yeah-that is the one. How tragic. I'd like to see what the ntsb determined. I seem to recall temps near 100f but that might have been misinformation.