Flap problems Why?

[Anticept]

Eddie: Let's talk sometime about that trim, maybe I can help. PM a phone #?

[FastEddieB]

Good deal.

[Mike Koerner]

I don't believe electric flaps are lighter than manual. Furthermore, I think they are more expensive and less reliable.

I suspect the reason our planes have electric flaps is for safety - specifically to slow down the retract during a go-around.

I wish we had manual flaps because I would like to be able to dump the lift the second the wheels touch down. I think we would have fewer post-landing runway departures and a lower overall accident rate. However, I think we would have a higher fatality rate.

I remember years ago landing at Rialto in a early model 172 on a very dark and windy night. I screwed up the approach with full flaps and decided to go-around. I punched the throttle I dumped the flaps then got a sinking feeling as I realized I had just made a huge mistake. I got away that time and never bothered to explain what had happened to my passengers (including the woman who later became my wife) but the event is burned into my memory anyway.

I think part of the reason Cessna, and Flight Design, went to electric flaps was to prevent such calamities.

Mike Koerner

[FastEddieB]

I don't believe electric flaps are lighter than manual. Furthermore, I think they are more expensive and less reliable.

I suspect the reason our planes have electric flaps is for safety - specifically to slow down the retract during a go-around.

 

Pretty sure that's wrong on both counts.

 

Only way to be sure is to ask a designer.

 

Does anyone have access to a Flight Design designer, or a designer of another brand, who could opine on the reason they chose electric flaps?

 

And sorry to participate in a hijack, but I was taught early on to leave the flaps alone after landing, and it's still what the FAA recommends and wants to see on a checkride. Hence, in 40 years and a whole bunch of landings both as PIC and instructor, nosewheel and tailwheel, paved and grass, I've never seen a downside - land at or near the stall and there's virtually no lift to "dump". A pilot who "dumps the flaps" is in theory accepting decreased aerodynamic drag for marginally increased braking. I think you'll find in real life if there's any advantage to "dumping the flaps" after landing, the benefits are vanishingly small.

 

BTW, I'll stipulate there may be fringe, "bush pilot" applications where it may be a skill to hone. In day to day operations, not so much.

[FlyingMonkey]

This subject came up recently, and I definitely understand where Eddie comes from on leaving flaps alone.

 

But I agree with Mike about the CT specifically -- it still wants to fly at touchdown speed with full flaps, and it keeps a lot of weight off the wheels, which makes it pretty unstable in the early (fast) portion of rollout.  Add in some gusts from the side and it can get downright uncomfortable.  If I land at 30° flaps or more, I usually put up the flaps as soon as I'm down and stable on the runway (see my video in my thread "The Wild Kingdom" thread for an example).  This is not something you'd want to do in a retractable airplane, but for the CT I feel it's safest to get the weight planted on the wheels as soon as possible at high flap settings.   This is usually not a problem when using 15° for landing, and I usually leave them down until clear of the runway in that case.

 

Eddie, do you shun touch and go operations because of the reconfiguration issue, or do you consider that something else where the takeoff roll is separate from the landing? 

[Ed Cesnalis]

If you routinely land a CT in big gusty winds dumping the flaps can help to limit you to a single landing.  Gust factors in the 20kt range can get you flying again.  The problem with that lift off from the gust is it happens at a slow speed where directional control can be challenging.

[FastEddieB]

 

But I agree with Mike about the CT specifically -- it still wants to fly at touchdown speed with full flaps, and it keeps a lot of weight off the wheels, which makes it pretty unstable in the early (fast) portion of rollout...

Eddie, do you shun touch and go operations because of the reconfiguration issue, or do you consider that something else where the takeoff roll is separate from the landing? 

 

On the first point, if a plane still "want to fly" at touchdown, IMHO the touchdown was too fast. If you can time the touchdown with the stick all the way back, the plane is done flying at that flap setting.

 

On the second point, its a good one. To be 100% consistent, I would have to shun touch and goes - so I see the disconnect. I guess its balance: on touch and goes there's a benefit in efficiency, from more landings and takeoffs in a given unit of time and brake savings. For that benefit I'll accept some small additional risk of moving the wrong lever at the wrong time in a retractable at some point in the future. I've just never seen any appreciable benefit to "dumping the flaps" if the landing was slow enough in the first place.

 

On a third point, I'm free to check out those brake parts and maybe trade rides later today or possibly tomorrow - let me know.

[FastEddieB]

If you routinely land a CT in big gusty winds dumping the flaps can help to limit you to a single landing.  Gust factors in the 20kt range can get you flying again.  The problem with that lift off from the gust is it happens at a slow speed where directional control can be challenging.

 

There may be a time and a place. With really large gusts I might choose minimal or even no flaps in the first place, reducing or eliminating any benefit from flap retraction on rollout.

[FastEddieB]

Good for you!

 

BTW, my Sky Arrow calls for 10º flaps for takeoff, so that's where I retract them to, usually after clearing the runway on a full stop. I then leave them there when parked so they're already at takeoff setting for the next flight - all I have to do is confirm 10º.

[FlyingMonkey]

I'm with Eddie on this.  I made 4 touch and go's yesterday and one full stop landing in the SkyCatcher.  All were in gusty, windy conditions and some with significant cross-wind, so I only used one notch of flaps.  Since I usually take-off with one notch, I didn't need to fool with the flaps after touch down.  I made 5 good landings, by the way.

 

If the winds are gusty or strong, I usually do the same thing...15° flaps and leave them alone, since they are my takeoff setting as well.

 

Honestly, I usually only use 30° flaps when the wind is 8 knots or less, and probably 6kts or less in a crosswind.  I probably don't *have* to raise the flaps in those conditions, the airplane just seems more stable on the ground that way.

 

Eddie, my touchdowns are usually ~42kt at 30° setting, that is right at stall according to the POH.  Once I sink to the ground I can't make it go any slower and still fly!  

 

I'm on call for work this week, so it's going to be tough to deal with the brake parts, unless you want to fly out to WDR sometime after 5pm one day this week.  This weekend might work if the weather cooperates.  I have Friday off as well.

[FlyingMonkey]

Good for you!

 

BTW, my Sky Arrow calls for 10º flaps for takeoff, so that's where I retract them to, usually after clearing the runway on a full stop. I then leave them there when parked so they're already at takeoff setting for the next flight - all I have to do is confirm 10º.

 

I used to taxi at -6 for wind tolerance, but recently I got paranoid about taking off with the flaps still up, so I switch to 0° for taxi unless the wind is up, since that's an appropriate takeoff setting.  I still check flaps before departing, but if I miss it somehow I'm still in a valid takeoff configuration at 0°.  I definitely prefer 15° for takeoff though, the takeoff is shorter and slower that way.

[gbigs]

If you routinely land a CT in big gusty winds dumping the flaps can help to limit you to a single landing.  Gust factors in the 20kt range can get you flying again.  The problem with that lift off from the gust is it happens at a slow speed where directional control can be challenging.

 

Correct.  In winds over 10kts cross or even headwind a no flap landing is much smoother and the plane prefers it.  I NEVER use 30 degree notch, not even on a short field.    Taking off with no flaps in a headwind or crosswind is also a no brainer for the CT.

[Doug G.]

Wrong. I generally use 15° and might plane has told me it is extremely happy with it, sometimes even overjoyed. And, if you don't know how to use full flaps, your training is not complete.

[FastEddieB]

Correct. In winds over 10kts cross or even headwind a no flap landing is much smoother and the plane prefers it.

Up until the point where the plane swerves off the runway for whatever reason, or blow a tire, or seizes a brake, or strikes a deer and that extra speed carries a huge downside.

 

Were you taught that way (no flap landings over 10 knots) or have you discovered it on your own? And how do you plan flap usage on your new plane?

[FlyingMonkey]

I used to make all my landings with 15° flaps.  Frankly, I found higher flap settings a little intimidating after a couple of "not pretty" attempts.  Once I got my 15° landings to be very consistent, I went back and wanted to really master the 30° setting.  I played with it in various conditions, at various approach speeds.  What I found was that my 30° landings had previously been inconsistent because I was simply carrying too much damn speed into the landing.

 

I slowed things down.  My current regime is once I go from 15° to 30° I slow to 52 knots, and down to about 50kt on very short final if I have a passenger.  If solo, I can let it get a little slower, about 48kt on very short final.  By very short I mean the last 50 feet or so.  In the round out I slow to just above stall and let the airplane land when it's ready.  If I'm much faster than these approach speeds, a float or balloon is much more likely.

 

I've become very comfortable with the 30° flaps setting, and that is my preferred landing mode in light to moderate winds.  The slower landing speed is very gentle on the airplane and gives better control.

[FlyingMonkey]

Using no flaps with a 10 knot headwind makes no sense.  Your airplane doesn't act or react differently with a head wind.  It simply has a 10 knot slower ground speed.  Also, a short field landing calls for full flaps in most airplanes.  Less than full flaps results in a faster airspeed, faster ground speed, and longer roll out, defeating the purpose of a short field landing.  If you're using less than full flaps for a short field landing, it's not a short field landing.

 

I love a 10kt headwind with 15° flaps...it's like being on an elevator!

[Anticept]

I'll use no flaps in a 10 knot crosswind...

[Ed Cesnalis]

I still do the majority of my landings at 30*.  Crosswinds greater than 20kts is where I generally use 15*.

 

At 30* I find I get the stick full aft even when I have some sinking left to do.  

 

If I get close to the ground and have energy to bleed off I use an attitude that feels nose low to me but probably isn't and at the last moment get the stick full aft for a final "bird like", behind the power curve, flare to a high attitude slow touchdown.

 

Another CTSW technique that I use is to allow a wing to drop if it wants to but soften the contact with opposite rudder and then lower the other wing again with rudder.  This feels like I'm 'feeling' for the runway and land with a 1-2 step, one wheel at a time, but not for crosswind correction as much as using / controlling the wing drop.

 

A CTSW lands 'different' but nicely

[Mike Koerner]

Gentlemen,

Let me start by correcting some misimpressions my earlier post seems to have generated: My landings are all at a minimum-energy, stalled condition. I normally land with 15 degree flaps, but I use zero in gusty conditions and 30 and 45 degrees occasionally just for the fun of it... but still I'm always stalled at touchdown. (Please note that I’m not advising anyone in anyway. Do what you were taught, what it says in the manual and what you feel comfortable with – hopefully one it the same.)

The challenge (I hate to say problem) is that the angle of incident of my aircraft’s wing is too high when the aircraft is setting on its wheels. (Please note that my aircraft is a CT2k. This may or may not be true of other Flight Design products or even other CT2k aircraft.) As a result it’s impossible to land with the nose up as high as you can, for example, in a fully-stalled 172; and the nose doesn’t fall through as far after landing. (This was documented in great detail in a post by Dave Ellis on a previous CT forum. He had added extensive instrumentation and a data acquisition system to his aircraft). Further, the coefficient of lift is still relatively high after landing. (This is very different than most aircraft which land on the mains with the nose high and kill virtually all lift as the nose falls through.)

One consequence of this relatively high coefficient of lift is that the plane takes off again after a fully-stalled landing when hit by a relatively modest gust down the runway. Another is that it slides sideways across the runway, bouncing from main to main, after the upwind wheel is set down in a strong crosswind (side slip) landing.

It is critically important to get the flaps up, all the way, as quickly as possible after landing. (So far I have not had a problem confusing the flap switch with the gear switch in my CT ;-).

Also, I disagree with the suggestion that the aerodynamic drag with the flaps down does as much to slow our aircraft as braking with the flaps up.

And finally, in any light sport aircraft, I think it’s a mistake to have the flaps in any position other than fully up while taxing. It’s too easy to get blown around or blown over. I wait until I turn onto the runway before lower the flaps for takeoff.

Mike Koerner

[FastEddieB]

Good post. Seems like you've really sorted out what works best for you in your airplane.

 

My landings are all at a minimum-energy, stalled condition. I normally land with 15 degree flaps...

To be precise, to be at a truly "minimum energy" state, one would need to be both in a full stall and have full flaps. I'm still of the opinion that some of the extensive damage we're seeing on some CT landing accidents comes about from extra energy at touchdown - some caused by "flying it on" and some by less than full flaps. At higher energy states there's both a larger tendency to swerve and more damage in the works if and when inhospitable terrain causes the nosewheel to dig in or the plane flips.

 

Also, I disagree with the suggestion that the aerodynamic drag with the flaps down does as much to slow our aircraft as braking with the flaps up.

For my part, I actually posted something a tiny bit less declarative: "A pilot who "dumps the flaps" is in theory accepting decreased aerodynamic drag for marginally increased braking. I think you'll find in real life if there's any advantage to "dumping the flaps" after landing, the benefits are vanishingly small."

 

 

Mike also said*: "And finally, in any light sport aircraft, I think it’s a mistake to have the flaps in any position other than fully up while taxing. It’s too easy to get blown around or blown over. I wait until I turn onto the runway before lower the flaps for takeoff."

 

Good point. I've never noticed any appreciable difference between 0° and 10° flaps when taxiing, but I suppose there theoretically could be. I will reflect on changing my practice, especially on windy days.

 

 

*I don't know why we can't seem to have more that two quoted blocks of text. Is that a setting that can be changed?

[FlyingMonkey]

The effectiveness of "dumping" the flaps in the CT (real or perceived) might stem more from landing gear geometry than energy state.  If the gear track is too narrow, wheel camber/caster/toe-in are not ideal, gear legs are too long, too much/not enough flex in the gear legs,  or a host of other design issues, the ground handling might benefit from having more weight on the landing gear during the higher-speed phase of the roll out.

[Ed Cesnalis]

Eddie says he doesn't see how taxiing with 10* makes much difference.  In a CT 10* becomes 15* and full retracted becomes -6* or -12*.  The difference here is at least 21*.

 

If you land with 30* and retract to -6* that's a big 36* dump.

 

My impression by looking at the Sky Arrow is that it would land like a heavier plane than a CT, of course that is a guess.

[Tom Baker]

I am going to throw an opinion out based around 700-800 CT flight time in both CTSW and CTLS, and a little knowledge picked up along the way from different Flight Design personnel.

 

When landing the CT, and it is on the ground with flaps down a gust causes a different reaction compared to most other aircraft I have flown. On the ground the flaps try to raise the trailing edge of the wing causing the airplane to tip forward. If you have a gust right after touchdown and have relaxed the pitch control the airplane will try to wheel borrow. The same thing will happen if you apply power for a touch and go and let the airplane get to fast, or simply land to fast and relax the back pressure. In my opinion this is likely what is leading to the loss of control on landing.

 

This problem is more prevalent in the CTSW than the CTLS. One of the changes they made for the CTLS was to move the main landing gear aft a little bit to make the airplane more stable on the ground.

[FastEddieB]

My impression by looking at the Sky Arrow is that it would land like a heavier plane than a CT, of course that is a guess.

I have long since stipulated that the CT may be odd and require special techniques.

 

My techniques have served me well in all the GA planes I've flown, up to Piper Aztecs.

 

Key is, full stall=no lift, and hence all the weight should be on the gear anyway. I guess if you fly it on well above stall speed, and there's a time and a place for that, I suppose getting rid of the flaps after landing may serve some purpose.

 

Finally, I strongly recommend against doing it on a checkride. Might not bust the ride, but most examiners would frown on it, unless specifically called for in the POH.

[FlyingMonkey]

Key is, full stall=no lift, and hence all the weight should be on the gear anyway. I guess if you fly it on well above stall speed, and there's a time and a place for that, I suppose getting rid of the flaps after landing may serve some purpose.

 

 

 

I think this is incorrect.  Full stall = insufficient lift to support the full weight of the aircraft, not NO lift.  If there were no lift at all then control positions in taxi would be irrelevant, and there would be no need for gust locks on the ground.

 

On ground roll during takeoff, you can feel the airplane "get light" well before it lifts off, and at well below stall speed.  You are producing lots of lift, just not enough to support the weight of the airplane.