CSU's??

[I_Con]

Hi all

 

I'm new here so please be gentle.

 

After having just completed my GFPT in a C172 and taking a couple of flights with passengers, it's time to start navex, I have decided to do it in a C182, but I just cant get my head around that darned blue knob. My first and only flight in the C182 was out into the training area for a couple of stalls and general handling then back to the AD for circuits. Conditions were very bumpy in the circuit, coupled to that I was in a faster and heavier plane so alot of what my instructor was telling me was going in one ear and out the other.

 

So my question is can anyone help me out with info regarding CSU's. I kinda know the basics, i.e. to set power we start from throttle, then pitch, then mixture, then the opposite for reducing power. But thats as far as my knowledge goes. I want to know how it works in detail, problems that can arise, how not to damage CSU/engine with incorrect settings, e.t.c. Are there any articles online or good books that go into detail regarding CSU's? Any help will be greatly appreciated.

 

I'd ask my instructor but I don't want waste the limited time I have at the air field in a class room learning something I can learn at home.

 

Tanks in advance.

 

Con

 

 

[djpacro]

I agree with cficare - your instructor must educate you as part of providing the endorsement.

 

For additional reading, I suggest the FAA Handbook of Aeronautical Knowledge (chapter 6 for props).

 

 

[Bandit12]

There should also be plenty of information in the theory books (such as the Trevor Thom series) about the CSU.

 

They aren't too difficult, but an understanding of the mechanics of what is happening is really helpful.

 

Why not just do the nav training in the 172? Plenty of time to convert to bigger and more expensive aircraft later.

 

 

[facthunter]

Cfi is right there. There are many aspects of operating variable pitch CSU's etc, that you should be on top of or you should not be using one. I don't know offhand what books are available , but conversion notes for larger piston engined aircraft might be a start, or even Wiki. Look up things like prop safety speed ,pitch locks/stops. All your manifold settings will be related to RPM settings and your variable pitch prop has to be handled in a way where you get the maximim performance benefit without damage to the engine.

 

Mixture is a height/power thing and a bit separate from pitch (RPM) and MP considerations. At low speed the prop should be in fine pitch if you might need maximum power. At high speed you would overspeed your engine, if the pitch was in fine, so in some respects the prop behaves as a gearbox does.

 

Obviously you start your engine in full fine, where your prop behaves as if the pitch is fixed, sitting on the fine pitch stop.

 

If you are dealing with radials look up the concept of "balanced" power where high rpm's with low MP can damage the engine. Some engines can be overboosted if low RPMs and high MP's are used. There are also balancers fitted to some of the larger engines crankshafts which can be upset by harsh engine handling. Nev

 

 

[Guest Howard Hughes]

how not to damage CSU/engine with incorrect settings

You more than likely won't damage a C182 with incorrect settings, you can probably do a lot more damage with incorrect use of the cowl flaps!:thumb_up:

 

 

[Tomo]

Firstly... Welcome along!

 

I find it interesting you're wanting to do the Nav's in a 182... they use a lot more fuel!

 

Agree with those above that your instructor should explain it all to you, but nothing wrong with reading up more about it yourself for sure! I like the fact you want to know how it all works, rather than just the procedures. Makes so much more sense when you know why and what happens when you move a lever, rather than just seeing numbers change.

 

Here's something I just found, has some pictures :thumb_up: and a few descriptions.

 

http://www.fly13.co.uk/Tug/VP Prop/Prop.htm

 

 

[IanR]

One key think is to look at the tables that give MP settings for each RPM setting. Also there will be a climb RPM and MP setting. Its not complicated but as others have said you need to be briefed on the concepts.

 

One thing to remember is that a CSU is a Constant Speed - so when you say set 2400 RPM it stays at that whatever the throttle setting (within reason)

 

 

[I_Con]

Thank you to all who replied, the links so far are what I was after. My theory books (DH GFPT and Bob Tait PPL) do touch on the subject but thats it.

 

To answer the questions that have come up. Firstly my instructor did give me a briefing but it was a briefing on a C182 in general and didn't really get into any detail re a CSU, and I didn't get any literature on the subject either which is why I am here. Also I'm only at the air field one day a week so didn't want to waste my time with my instructor being briefed on something I could learn at home (or on slow days at work ) in my own time.

 

Why a C182? Well I want to move on from a 172 when I have my PPL so no time like the present, and I want to get more ratings eventually (night, retract and twin maybe) so wanted to get the CSU out of the way early. I know they cost more but they are faster so it kinda works out the same in the end, and lastly at the school I'm using its really hard getting one of the C172's for a 2 hour flight let alone for half a day for a nav, and I wanted to start the nav training ASAP instead of waiting 2 months for a plane.

 

 

[Tomo]

Why a C182? Well I want to move on from a 172 when I have my PPL so no time like the present, and I want to get more ratings eventually (night, retract and twin maybe) so wanted to get the CSU out of the way early. I know they cost more but they are faster so it kinda works out the same in the end, and lastly at the school I'm using its really hard getting one of the C172's for a 2 hour flight let alone for half a day for a nav, and I wanted to start the nav training ASAP instead of waiting 2 months for a plane.

I guess that's a good enough reason! You'll enjoy it I'm sure!

 

 

[Mazda]

I agree, it is not easy to do here, ask direct questions from your instructor, ask him or her to draw a diagram of the type of CSU in the 182, and give background infomation of the other basic type, discuss failures, discuss what to do in an engine failure, discuss general settings and and look through the 182 book with your instructor. The instructor must be able to show all of this to you. If not, ask for an instructor who can show you.

 

The ATC books have some some general info on CSU.

 

The 182 is easier in some ways! Which model are you flying?

 

 

[sseeker]

Knowing how a CSU works fully is quite complex, we did this as a unit at school. If you want help, I'm more than happy to Skype with you to explain it. Do get your instructor to attempt to explain it to you and show you cut aways of the actual CSU & prop hub. It really helps.

 

-Andrew

 

 

[I_Con]

So I have taken everyone's advice have cancelled my first navex and replaced it with a thorough ground briefing followed by more circuits.

 

 

[facthunter]

Great aeroplane a C-182. The extra speed offsets most of the extra cost. Remember that this prop is actuated by oil pressure as many are. Props want to go to fine pitch due to centrifugal force., and this is opposed by oil pressure that is metered by a governor. Some others use electric motors geared to turn the blades to change the pitch. Some props can be feathered, to afford minimum drag, and some can be reversed to improve the aircraft's ability to slow down after landing. ( Some STOL planes have reverse thrust in flight capability).

 

Interesting stuff. Till you are going above about 110 Kts, you don'treally need CSU's as they add weight and complexity and cost, but it all seems right when you coarsen the pitch and the revs drop back, like going into overdrive. Nev

 

 

[Guest pookemon]

Really, while it will delay your NavEx, you should do a type conversion THEN the NavEx, or a NavEx then the type conversion. You shouldn't really do them at the same time. That's my opinion anyway. It's not that you can't do it, but I think it would just make it that much easier.

 

I read the CSU section of the PPL books I'm using for my training and it went in one ear and out the other. I think primarily because it talks about RPM and seems to confuse Engine RPM and Prop RPM. As with anything I think it's just practise, practise, practise. That's one reason I'm glad I am going the RAA route first. A Gazelle has one knob that makes the engine go louder or quieter. Pretty easy really. ;)

 

I think facthunter's description above is about as clear as it gets. And a demonstration along those lines in flight would probably produce an "Ah I see" moment...

 

 

[IanR]

One thing I noticed when flying one of the later model C182s was that there is not actually a lot to do - they are governed to 2400 rpm which is also one of the cruise settings - so you could not touch the blue control from takeoff to landing and stay within requirements - takes the fun away !! Is it one of those you are flying ? Earlier ones much more to do.

 

 

[Guest pookemon]

Pookemon, the engine RPM and Prop RPM can never be different speeds to each other at any given speed setting on the CSU because they are mechanically connected. It is the CSU that governs the engine speed automatically to the RPM you have set by continuously varying the propellor pitch.

And that, again, is a great point to make that the book didn't (or at least if it did - it didn't sink in). With using the two different terms, it made me think there was a variation in the "two rpm's". Just stating that the prop RPM and engine RPM are the same makes another piece of the puzzle drop into place. It'll be a while before I get close to anything with a CSU, but knowing these things is always going to benefit me in the long run.

 

Thanks,

 

Scott S.

 

 

[davebutler]

A little off topic but I just ran some numbers (Speed & Cost/hr) on a C172SP and C182Q I got from the Redcliffe Aero Club site and was suprised that the C182 came in a little cheaper than the C172 on a 150nM Navex:thumb_up::thumb_up:

 

 

[Bandit12]

And the throttle becomes a measure of manifold pressure (MAP) instead of engine RPM with a fixed pitch prop. Just like when you start climbing a hill in your car, you push the accelerator but the engine RPM doesn't change, and your fuel flow increases.

 

 

[facthunter]

Whether the engine is geared or not is not of much consequence,( except to the designer) . You will usually read ENGINE RPM's on your dash, and all limitations relate to that. Overspeed, RPM's for Manifold Pressure tables giving you creuising power options. Power output is a product of RPM set and MP. As you climb you will get to a height where the MP you want uses FULL throttle, and above that pressure height your MP will reduce, and so will the power.

 

You generally don't use the mixture function below about 5,000 feet altitude, although some pilots will use it when taxying to prevent sooting plugs. If this technique is used you MUST ensure the mixture goes to full RICH for take-off.

 

IF you are operating a CSU you should be aware of any RPM's that you should not use. Some engines have as many as 3 RPM settings the engine is not to be operated at. This can also apply to a fixed pitch prop, but you are more likely to encounter a situation where you COULD SET a particular RPM on the CSU. Nev

 

 

[facthunter]

Take it up with him Cfi, Not me. Nev

 

 

[facthunter]

David, my training was not by the military, though most of my instructors were ex-military as was the training manual called an AP 1732 if I recall it correctly.

 

Whether you lean the mixture out or not IS predominantly an altitude thing. Whether it should be done at 1500' depends on how rich the carburettor is set up. It becomes almost essential at 8.000 feet as the normal carburetter is not baro compensated and it will be noticeably "lumpy" if not leaned somewhat. ( As well as wasting fuel, sooting the plugs, and making the oil black.

 

Leaning some engines can be a fairly imprecise thing. Some just lean it out till it just starts to falter and then richen it up a bit. In a good set-up you have charts where the pressure altitude, RPM, Manifold pressure and the power setting required tables give you a fuel flow to aim at as well. ( Assuming that you have a flowmeter) otherwise there is the EGT. gauge. with some going for the Lean of Peak temp. drop or Rich of Peak temp drop. Most of us know that you can hurt your engine by running it lean so I will leave the argument there for the moment. Nev

 

 

[Guest Howard Hughes]

Most of us know that you can hurt your engine by running it lean so I will leave the argument there for the moment.

What about if the AFM says to run it 'lean of peak'?

 

 

[facthunter]

I see my post has gone missing. I'm not blaming any outside interference, but this happens sometimes (very annoying). I can rarely bring myself to try to re-do the post.

 

Anyone who does oxy welding knows about carburising and reducing flames. I have never been a fan of lean of peak and as far as I'm concerned the Jury is still out on it. Stray oxygen (Surplus) will always find something to oxidise at high temperatures.

 

David, without trying to be picky , how could you ALWAYS TEND to do something? Tending implies an inclination and always means what it says. Every time..

 

I would support referring to the POH or The AFM, but often they are fairly reduced documents (They don't go into things too deeply) and I would not see them as being the last word on matters of principle. No-one hurts a motor very much,( if at all) running it a bit rich. There is a tendency to try to save money by running with a lean mixture. Lean mixtures are more prone to detonation and that is why it is not recommended to lean ANY engine at high power . They are likely to burn the film of oil entirely from the cylinder surface and oxidise things like a red hot exhaust valve. And they ARE red-hot when running at any reasonable power setting.

 

Mixture ratios that are well away from the ideal fuel air ratio are more difficult to ignite and burn slower. if you run a motor on a dyno and either retard it or lean it out the EGT will rise principally because the fuel is still burning when it exits the motor. Motors that are operating at the upper limit of their designed BMEP, (Almost a torque thing) are run excessively rich,( for safety).

 

. Most ( perhaps ALL) aero engines on take-off (max) power are operating this way to help keep them cool (er). and prevent detonation, and get the last bit of power available safely from a particular motor. You will recall the problems asociated with the Jabiru after the introduction of the "leaner " running carburetter set-ups. In our sphere of flying , "don't go there". when it comes to the lean mixture regime Nev

 

 

[poteroo]

I was taught, and still teach, leaning at all times when using less than 75% power settings. How you do it depends on the instruments available. It's nigh on impossible to lean LOP in carby engines, but in FI types it's easy with good instrumentation.

 

BTW, we used to lean our FI engines for t/o in PNG when operating off many higher altitude strips, because you couldn't achieve even 75% power at WOT on the ground. In theory you could go to 100 ROP for this but most of us used just a little more avgas because it was so cheap then.

 

happy days,

 

 

[facthunter]

The highest I've been without leaning is FL140. ( There was NO mixture lever) The engine was not happy as it was seriously rich. 75% is the figure often used . before leaning. This would/should mean that you are out of the power range where detonation may occurr. If you were climbing and the CHT's were towards the upper limit I would delay the leaning , in those circumstances.

 

Some private operators were taking off with less than WOT, because they believed they were nursing and therefore saving their engines. The engines were actually worse off as the motor never got the enrichened mixture stage that comes in at higher power settings. DCA at the time put out information spelling out that it was a bad idea to use less than the recommended full throttle. Nev