Thread: Unstable approaches

i'm starting a new thread in an attempt to stay on topic.

i find that summer landings present a whole new challenge in a CTSW. control authority is good and it is easy enough to maintain alignment and hold the centerline course. pitch authority is excellent and the CTSW responds well to throttle inputs but the hard working wing coupled with the light weight and slippery design can mean there is little ability to keep the ct on glide slope.

to be clear i'm talking about conditions where one or more portions of your short final glide is a climb because of excessive lift resulting from the unstable conditions. wind direction is likely highly variable and velocity is probably variable and gusty. these are the conditions that make landing my ctsw a whole new ballgame. not only are my control surfaces active but my throttle is active as well.

in such conditions i'm looking for a window that allows me to get slow close to the ground. on a day (likely afternoon) like this i am more cautious about trying to fix a landing and more prone to firewall the throttle if conditions send me upward again. in these less stable conditions the initital approach to the runway can be done with a larger margin from stall speed and in a configuration less affected by sheer. once you have contacted or spent some time inches from the runway with your speed decaying and then rise, float, baloon or bounce up you are now in the unstable condtions without the same airspeed that you had on your approach.

i fix a lot of landings for various reasons, this summer when the go-around vs fix it option comes up i will consider the stability and the possibility that at a slower speed my margin may be inadequate for an unfortunate gust with enough tailwind component.

i hope i was clear because i believe i am incrementally learning a valuable ctsw specific lesson. a long time ago i had extended discussions with one of the owners of an early ctsw landing incident that happened before one of the new owners learned to control the ct on landing. clearly inadequate training. the owner that i talked with continued to blame the design for responding without any input from the pilot. this pilot damaged the ctsw repeatedly by oscillating down the runway bouncing of the mains and nose wheel and believing that the ctsw was very badly behaved.

i have now experienced (without the contacts) how sensitive the ctsw can be when landing in unstable conditions when too slow while more than 3' from the runway. when gusts have an unpredictable frequency and their direction is variable (meaning some add lift and some subtract lift while all challenge your alignment and attitude.)

conventional wisdom dictates that you go-around as opposed to land from an unstable approach. we all have to fly in the real world where decisions are not black and white. do i land from a less stable approach? where do i draw the line? good judgment increases from experience.

Ed,

This is my first summer with my CT and I find much different conditions when I am in that last 2-3 feet above the runway.

Just when I think I have a great landing lined up, I ballon up and have to add power or except a small bounce when I contact the pavement. If I hold the stick and don't move it back at all then I have less ballooning but don't care for the firm contact I get.

I like to use 15 degree flaps for normal landing and wonder how much different things would be with 30 degree flaps, (seems you use 30 degree more often).

I am going to try leaving in a little power to see if I can get a softer touch down, but I am not to crazy about carrying power on base and final.

Columbia is in the foothills and gets some strange winds during the summer after 11:00 AM and poses somewhat of a challenge.

I can land safely without bending the airplane, but I would like to refine my landings for a smoother touchdown.

Originally Posted by awelectric

Ed,

This is my first summer with my CT and I find much different conditions when I am in that last 2-3 feet above the runway.

Just when I think I have a great landing lined up, I ballon up and have to add power or except a small bounce when I contact the pavement. If I hold the stick and don't move it back at all then I have less ballooning but don't care for the firm contact I get...

I experience this summer phenomena all the time, it's like a force field that your winter time experience ( as well as experience in other designs ) didn't prepare you for. Roger Lee was close when he said practice your roundouts. well first i got pi**ed off and then i went out and practiced my roundouts.

I learned something interesting, to put it in "force field" terms; the roundout when the force field is there is more not the same than the round out when the field ( winter ) isn't there. In an extreme case i found myself level at 4' with my nose still down and it was not yet time to pull back into a level or slight climb attitude yet. Energy was being bled off in that configuration and even the smallest back pressure I could manage would have finished my round out too high.

Here's the nugget *** extend the completion of your round out until you can do so without gaining any altitude and until it can be completed at an altitude of no more than 3' ***

That's my take at 30 degrees and at 15 degrees the feel should be a bit less critical.

Now what the hell is this force field? First I don't think that it is excess airspeed, I find if I reduce airspeed a little t hat the force dissappears but I'm too slow. It is a lot like a ground effect, more so than a sheer. It must exist at around 8' - 10', when we sense it at 3' our wings are at 8'-9'. One guess is that it is rising air from the sun on the runway but it isn't organized into a rotating thermal and reaches 9' above the runway and turns horizontally. The force as well might be a denser mass of air.

Ground effect was always a pleasant sensation that made landing a low wing easier, this effect presents a sudden change in the amount of lift our ct wings produce. Our high tech drooped wing tips might make the effect more pronounced.

I'm concluding that backpressure in roundout is like rudder or aileron on crosswind landing. You need "just enough" the amount needed is a variable and you judge the amount needed by the result you get. All roundouts require different amounts of pressure, and different durations. Look for the force field and use it as a clue to be more patient, don't complete the round out as soon when it exists. If it made you balloon try it again and be more patient.
My thinking on the 2,700' setting is that when you need power in that neighborhood it is a fine number to adjust to. Ultimately energy can come from airspeed, power, and or altitude. They are interchangeable. Indicated airspeed is the best metric for maintaining an approach and pitch and power settings as well as slips are the tools you have to manage the energy while maintaining your touchdown target. The more you rely on a given power setting or a given angle for your stabilator the more you are relinquishing control. The CT does not quite land itself. Moving the stick back and rising is bad, better to hold the stick steady, better yet to pull the stick back without rising. Holding it steady limits your aerodynamic braking. Keeping power at 2,700 can be stabilizing but it does limit your ability to subtract energy.

This fource field / round out issue is one aspect of summer time approaches and probably the most important. If you handle the roundout without gaining unwanted altitude you shouldn't have to add power and then wrestle her down at a slower speed.

Originally Posted by awelectric

Ed,... If I hold the stick and don't move it back at all then I have less ballooning but don't care for the firm contact I get.

I like to use 15 degree flaps for normal landing and wonder how much different things would be with 30 degree flaps, (seems you use 30 degree more often).

I am going to try leaving in a little power to see if I can get a softer touch down, but I am not to crazy about carrying power on base and final.

at a given power setting 30 will be steeper with a more dramatic round out. speed is slower and runway visibility is better.

don't forget that sink can be high at any power setting. leaving in ( or applying ) power to soften contact is fine, just don't accept what you get even if you don't like it. same with keeping your stick steady.

if you are in the final stages of landing and sinking too fast you are down to 2 options. altitude is already spent so you can look to your throttle and or your stabilator to reduce your sink rate at this point. keeping the stick steady to avoid ballooning is ok but keeping it steady when you need to reduce sink rate is silly. same with throttle, keeping it at 2,700 to reduce sink is fine but not if sink is too high, adjust the throttle.

we all fly different, the navy vs airforce thing. you may be more prone to adjust throttle or pitch but may do a combination of both.

I've posted before that I believe a 0 flap landing can be done with almost the same amount of runway as a 15, and keep the nose gear out of danger. Have you guys tried that? I did a classic 0-flap with Doug last week. Cross the numbers at about 60, at 3-5', attain an AOA that stops the descent, and the CT will tell you when it wants to land. On an nice day you may bounce a foot in the air once or twice, just don't fight it by nosing down...bring the stick a little more back after each bounce. When both wheels stick bring the nose down and you're done flying.

If you're doing this in 15G25, for instance, a gust may send you 6-10' in the air. Then you have to decide on whether to add power or just go around. I thing transition training should include adverse conditions at 0 flaps, so that people have an option other than risk flipping the plane doing a 30 flap landing in high crosswind. JMHO.

Oguy,

I agree, meaning that a zero degree flap landing done well can be shorter than a 40 degree landing with a bunch of floating.

CTs land short even if not configured for a short field landing.

I have to say that it makes me feel a little better to know that you high-time pilots have many of the same problems that I do.

I have about 110 CT landings. None of them were particularly hard. I had a couple of high bounces I immediately flew out of, a couple where a gust in the flare caused me to yaw beyond my ability to counteract it before the wheels touched. I flew out of those too. And one where a gust caught me with the mains down and the nose up. I opted to fly out of that though a better pilot could have probably handled it.

Some of my nicest landings have been with a steady crosswind. Adding a bias to the controls seems to improve my smoothness and coordination. Hot and gusty just plain sucks. As Tom Dunham preaches, always be ready to go around. I generally land with flaps 15 and 55-60 knots at flair. Actual touchdown speed is probably around 40-45 knots.

Here's a question, how long do you keep the nose up after you touch down on the mains> My instructor teaches to hold the nose up as long as possible to ease the stress on the nose gear. I see no harm on a cool, still day, but I'm wondering if it's the best bet in gusts.

Originally Posted by Jim Stewart

...Hot and gusty just plain sucks...

amen to that brother.


as far as keeping the nose wheel up on roll out. start with enough backpressure to lighten the load but keep the wheel on the runway.

another option is to keep it from settling and keep increasing back stick till you run out of speed and it settles with full aft stick.

if the runway is soft you might want to add power and keep it up so it doesn't get stuck in the mud.

the same can be done with the mains, you can do a touch and go on one main wheel only for instance.

I haven't done any pattern work in awhile, I think it's time I spend an hour or more working on that last three feet.

I don't like 0 degree flaps, unless the wind is really bad and even then I don't like the approach angle. I use 15 degrees flaps most of the time, I will work with that and try some 30 degree landings.

At Columbia if you get to the ground near the numbers, the mountain at that end blocks the cross wind that comes up everyday. If you float very far, the wind coming down the grass runway, (about mid field) makes things real interesting.

I am going to see if I can add a little power once I have the runway made and see if I can slow the rate of decent without extending the glide.

I did all my landings at idle until a couple of months ago. I now keep the throttle above idle but at no particular RPM target. It seems to help in x-winds.