Thread: A little rpm did wonders

I went out this morning to do some work in the pattern. My training was focused on the majority of landings to be at 30 degrees and no throttle/full stall. Today I decided to try the 2700 rpm approach at 55 kts and 15 degrees of flaps. It is amazing how much more consistent the landings were! I actually had 5 landings that were remarkably the same!

I was a little nervous on the first attempt as I was not sure how the CT would react having a little power. On short final the CT felt more stable and there was no tendency to balloon at the round out which really sort of surprised me. The plane really does just want to settle on the runway without the drop associated with a full stall landing. Just a nice smooth "chirp" with the nosewheel in the air a few inches which touches down nice and gently. Again "amazing"! I thought the first one was a fluke and I just got lucky but it just kept happening the same each time. You have to be diligent on the height of the roundout but the timing of the flare is not so hyper critical.

The conditions were on the calm side so I plan to continue experimenting with more wind, gust etc. Also the sight picture Roger Lee suggested of flying your feet right down the centerline of the runway made the "not quite lined up straight" landing disappear so thanks for that!

One of the benefits to a full stall landing technique is flying the pattern with no throttle on the base and final legs while maintaining enough altitude to always make the field. When you fly the base leg with 2700 rpm, the tendency is to come in alot flatter due to the extra energy on final. I plan to stay in the habit of flying a no throttle base and final to maintain a safe "Oh #$%&# my engine just quit" altitude but then adding a little rpm on short final for the settle landing at 0 or 15 degrees...just so I don't rely on that extra rpm to get me there and I don't come in too HOT!

It also makes alot of sense to have that extra control authority in X-winds and gusty conditions rather than a stall approach where you could really be pushing your luck if you get a rogue gust! Thanks to everyone for all the suggestions regarding landing techniques and if you haven't tried the 2700 rpm settle approach you really should. Try it you'll like it! I did not even have the temptation to look at my landing gear to make sure it was still alligned/straight when I put my bird away...A habit that I'm sure a few CT owners would like to break!

Smooth Landings,


Orson
N789TW

Hi Orson,

I'm with you. 2600-2700 rpm at landing just gives better control with landings all around. Since I put my feet on the line I don't ever land crooked or drift. You can leave in 2700 rpm and still keep your higher approach in case of an engine out. Just try a few different set ups.

Hi O Jet

Do you keep the throttle setting at 2700rpm till the wheel touch, as I still have a CT with the long wing and no wing lits she I don't even attempt landing in high winds.

Greeting from NAM
Peter

Orson -

I'm with you there. I think the CT likes a little power with landing. I will pull the power when close to flaring, sometimes over the threshold, sometimes just after touching down. It depends on the winds, and as you note, a little power helps with the gusts sometimes.

You might also want to experiment with CG - aft CG seems to help reduce control sensitivity in the flare, making it easier to get better landings.

Doug

Peter,

I enjoyed your picture on the other thread. I have landed at both 2700 rpm after touch down and pulled the power back just prior to touch down which seems to be a little more predictable as the occasional bump in the runway right after touchdown does'nt tend to cause a slight lift especially if you're flying single.

It looks like your location indicates that you may have to deal with blowing sand from time to time...have you had to land with sand blowing across the runway? If so how was it?

Orson

Hi Orson

As I have an Old CT with "not so good" cross wind characteristics, I tend not not fly if the cross wind get more than 5kts. I have however at a couple occasions landed with a strong sandy headwind with no problems on a tar strip, but I have had one occasion where I needed to do that on a sandy strip in the desert at Sossesflie this was a bit tricky has I could not see the edges of the runway very clearly. My CT being a German model had the single box filter for air, this I have removed as it possed a problem with the sand and dust. Have replaced it with 2 K & N filters which are easy to clean.

Greeting Peter

Hi Peter,

mounting the K&N-Filters for sandy conditions is a very good idea. The air box is not very airtight and sometimes I wonder why it does not become flooded if you fly through rain (which happens sometimes in Germany ) .

BTW: I have about 150 hours on our Club-CT2k and CrossWind above 5 kts is not a problem if it is below 15 kts and you do not set the flaps more than 15°. Landings in strong CrossWinds and 30 or 40 ° flaps are very tricky.

The suggestion to use some RPMs for better control on landings is not very helpful for the "long wing" Cts. With the fixed 2 blade Neuform propellor I had to reduce the idle-RPM to 1400 to make the beast land on runways shorter than 3 km
Today we have a 3-blade fixed fan and with this one landings are a little easier because of the better air-resistance of this prop. But an RPM of 2600 will make the Ct climb

Greetings from the home of FD

Markus

P.S.: Spellcheck said, english is OK

Hi Mark

Thank-you for the advise on the CTs with long wing, I have tried the little RPM but have had nasty experiences. What take-off RPM did you get with the 2 blade neuform prop?

Best regards
Peter
P.S don't worry about spelling...

Hi Peter,

the 2-blade Neuform was factory adjusted and with this setting we got about 4900 RPM at ground. With this setup, the Ct2k was very fast but didnt like landings as stated in my last posting.

With the 3-blade prop, which is mounted nowadays, the engine runs 5150 RPM at ground and runups. With this setup we tow gliders without any problems but cruising is a little bit slower than in older days. For getting 200 km/h (~110 kts) the engine has to turn about 5100 RPM, which is not as comfortable as 4800 RPM needed with the 2-blader.

My wishlist for christmas contains a pitch adjustable prop

Greetings

Markus

Hi Markus,


Too much prop pitch.
With the 912uls 100 hp running with the prop set to get only 5150rpm at wide open throttle you are not developing any engine torque or horse power. Bottom line your performance is a dog.

Reset the prop pitch to achieve 5500rpm and you will have a good performing CT. The engine specs on torque for the 912uls puts its best torque at 4800-5200rpm with 5000rpm in the middle, but the prop has to be pitched to get 5500rpm WOT flat and level. Climb and cruise with a ground adjustable prop is a balancing act. If you want the best of both worlds and have the performance of both climb and cruise set the prop to get that 5500rpm WOT flat and level. This is not a guess and is recommended by Rotax. If you wanted better climb over cruise for towing the glider up you may want to set it at around 5650-5700rpm. Very good climb, but at this rpm you will lose a little top end speed. If you only get 5400rpm then you would have a little better top end speed and a little less climb verses the 5700rpm. The 5500 will give you the best of both worlds and let the Rotax engine run where it was designed to run. With too much pitch you are not getting any performance on either side because you are dogging the engine. This is also proven by looking at the torque curve chart and HP curve in the Rotax manual. This is where many people now have set the prop pitch in the USA (on many different aircraft applications with the 912uls) to achieve 5500rpm. If you change your prop pitch from where it is now to 5500 rpm you will think someone supercharged your engine.
Whether it is a two blade or three strive for 5500rpm, your engine will be happier and work easier, too.
With your engine rpm only at 5150rpm flat and level you will need about 2 degrees flatter pitch. This is a good starting point. If it is slightly too much, I don't think it is, then take out .5 degree.

With this flatter pitch if you have a bad landing and balloon back into the air and need instant throttle/rpm it will happen faster with a flatter pitch prop and may save your bacon. Once you repitch a prop once or twice you will be able to do it in 30 min.

I saw the discussion on landings and rpm. Try setting your rpm early at with flaps or with out at 2700rpm and control your speed with the stick to keep it at 50-60 knots all the way to touchdown. Don't play with the throttle until you touch. I think with a few trys the landings will be smoother. Landing without power or playing with power at the bottom of the flare is ok, but takes a little more skill to be on top of changing conditions and plane pitch in reference to the landing. If on a short field or you are landing too long then flatten out the final approach. With this throttle setting you should be able to hit any target or the numbers anytime. If you can't then it is not the plane or the throttle setting, but the pilot skills. Just practice a little more with power. It is no difference in hitting a target than with out power, it's only in your head. Hitting a target is only aircraft control. 2700rpm will not keep you in the air, but help a little at the bottom round out and slow the decent rate just a tad. Because you have a lighter airplane then you might like 2500 or 2600rpm, just play with it a little.