Curb feelers for the tail strake

[FlyingMonkey]

The AP will likely be quite happy flying around with a low wing or level as long as it is flying the course.  You will want to perfect your rudder trim and with our canted panels your slip/skid ball is suspect.

 

First I move my rudder left and right and find the middle with the fuel sight tubes.  Next I use that to confirm my ball and then I fly with the ball in the confirmed position and confirm my wings are level.

 

Perfect coordination is illusive in a CT.

 

Cool, thanks.

[Anticept]

 

BTW, I think my EFIS also needs to be leveled in roll, it shows a very slight right bank when level on the ground.  I have to make sure it's not a gear geometry problem first, but I'm thinking the autopilot in smooth air will help me get these the EFIS calibrated correctly.

 

 

Andy:

 

The pitch attitude changes when airspeed does, because it will affect AoA. Don't try to make it perfect because you are going to chase it all over the place every time you decide to fly at a new speed

[FastEddieB]

Those of us with synthetic vision don't need to look outside while landing 

I'm afraid I'm not quite there yet.

 

But I'm working towards it!

 

[WmInce]

Just curious...

 

...do some here actually monitor the attitude indicator in the flare, so as to stop pulling at some specific pitch attitude?

 

As a data point, I never have. For me, even glancing inside at the instruments would take my attention away from the actual landing process.

 

I don't.

But if I found myself in a "higher than normal" pitch attitude during landing, I would take a quick glance at it to help me make a decision to continue or go-around.

[WmInce]

I'm afraid I'm not quite there yet.

 

But I'm working towards it!

 

 

Synthetic vision is a scud runner's delight.

The negative impact, no pun intended, is only a matter of time.

[FlyingMonkey]

Andy:

 

The pitch attitude changes when airspeed does, because it will affect AoA. Don't try to make it perfect because you are going to chase it all over the place every time you decide to fly at a new speed

Yeah, that makes sense. The plan is to set it at normal cruise speed with zero vertical speed. That should keep it within a few degrees of level in most circumstances.

[Anticept]

Yeah, that makes sense. The plan is to set it at normal cruise speed with zero vertical speed. That should keep it within a few degrees of level in most circumstances.

It's affected by weight too. Just tweak it and get it close.

[Anticept]

The DPE can, and has, chosen any field. Simulated soft field landings and takeoffs on asphalt are a walk in the park, actual soft field operations are quite a bit different. I almost want to say "harder", but really it's more like it's different.

 

An analogy that I will use is it is like mudding it with a manual truck. You can practice mudding on dry dirt or asphalt, and go through the motions of proper shifting. But until you actually go and mud it, you haven't actually developed the skills, only the basics. Shifting at the wrong time can means you stall the engine, or kill your momentum, or too much throttle in the wrong gear and you dig yourself in a rut. It's one thing to tell someone about it, but it's completely different to go put it into practice. But, once you've experienced real mudding, simulated mudding is a walk in the park. Same with soft field work.

[Runtoeat]

Interesting subject.  By chance, recently my friend constructed a small box that raises his nose wheel 4" and 8" off the ground.  We used this box to statically simulate the sight picture during landing with varying pitch angles.  With 4" rise of the front wheel, the pitch angle is  approximately 5 degrees and the tail on his CTLS is about 26" off the ground.  This condition is what I would call a "hi normal" pitch attitude during landings  This 4" rise off the ground with the front wheel produces a very noticeable pitch up attitude.  With the nose wheel 8" off the ground, the tail skid drops to being only about 8" off the ground and the pitch angle approaches 10 degrees.  The tail touches the ground at about 12 degrees pitch angle and this is perceived as a "extreme" pitch up attitude sitting in the plane.  Bottom line is one wants to keep the pitch angle less than 5 degrees and definitely should stay away from any angle approaching 10 degrees to prevent tail strike.  We find our typical pitch attitude just prior to touch down is around 2.5 degrees with the nose just a coup0le of inches off the ground and I suspect this might be true with other CT owners too.

[Ed Cesnalis]

Dick,

 

For what flap setting is 2.5° typical?  I have always said that in my CTSW level was a stall attitude with closed throttle and 30° flaps.  

 

On my perfect landings there are 3 phases coming out of the round out.

1. nose too low while bleeding off any excess speed.
2. nose high enough to clear
3. when well behind the power curve and ready to land move stick to aft stop and get the nose up as high as I can.

When I get it right I feel like a bird reaching forward with his feet while he flares to a spot landing.

[FlyingMonkey]

My wife handles the insurance for the toys.  She told me our aircraft insurance restricts soft field takeoffs and landings unless under emergency conditions.  We do have tundra tires on the CTLSi, but we didn't get them to do soft field landings, we got them because they were offered as a freebie in the package.

 

That seems unusual.  Do you have the airplane in a trust or some other arrangement?  I have not heard of such a restriction before...though I guess it would lower your premium!

[Tom Baker]

My wife handles the insurance for the toys.  She told me our aircraft insurance restricts soft field takeoffs and landings unless under emergency conditions.  We do have tundra tires on the CTLSi, but we didn't get them to do soft field landings, we got them because they were offered as a freebie in the package.

My guess that is that the policy says grass runways. Many policies are written that way. This would be a good time to check the clauses for ones policy. Just because it is grass does not necessarily make it a soft field.

[Roger Lee]

I agree with Dick. Most CT'ers are fairly flat in landing at touch and just before. When I touch my mains my nose wheel is just a tad behind. I see no real fictional reason to keep the front wheel off as long as possible. Once the nose is on the ground I have better and a more positive directional control, especially in bad crosswinds. While the nose is off the ground it is easier for a bad crosswind to push against my tail an rotate me. Whith the nose immediately down it must over come that friction of the nose on the ground to turn me.

 

Every plane is a little different and where one may strike a tail on a full aft stick another won't.

 

Planes are all different and that's why we learn our different characteristics in each one.

 

So long as you don't do a wheelbarrow landing nose too far down or strike the tail with a stick too far aft then everything else in between is okay.

[Ed Cesnalis]

When I touch my mains my nose wheel is just a tad behind. I see no real fictional reason to keep the front wheel off as long as possible. Once the nose is on the ground I have better and a more positive directional control, especially in bad crosswinds. While the nose is off the ground it is easier for a bad crosswind to push against my tail an rotate me. Whith the nose immediately down it must over come that friction of the nose on the ground to turn me.

 

In bad crosswinds I would rather spend some time on 1 wheel than to let the nose down to get that extra directional control.  The problem for me in this configuration is when the next gusts overcomes my grip on the runway.  You have extra friction on the nose but you are lighter on the mains and you are flat.  If I have my upwind wing lowered I might still get gusted beyond my grip but I can fly out of it instead of skidding sideways on my mains and my upwind wing coming up.

 

That steering might be nice when its nasty as long as it holds.

 

I once went for a wheelbarrow ride not because I touched down on the nose but because after all 3 wheels were on my mains came up and I weahter-vaned.  That was not the worst wind shear I have landed in but it was the closest I ever came to a real bad result.

[FastEddieB]

Yes, every plane is different.

 

Went out to the airport today and checked my "drag tail" angle.

 

First, plane level compared with tail touching:

 

 

 

Found an arbitrary and relatively level place for my propeller protector/level:

 

 

Zero'd the level and measured 5º nose down when level, 7º nose up with the tail on the ground:

 

 

 

So, that makes the difference 12º, which seems pretty typical.

 

Now here's a screenshot of one of my videos, right at the moment of touchdown, full flaps with the stick nearly all the way back:

 

 

Oh, and this is the way the big boys do it:

 

Just thought the additional data points might be of interest.

 

Add'l comments may follow.

[FastEddieB]

Only other comment right now is that 2.5º nose up sounds like very little to me, though it may be appropriate in some planes in some configurations for some missions.

 

As an instructor, when I see students landing too "flat", in my experience a slight misjudgment could easily have the nose touch down with or right before the mains. That is what sets the stage for a "bounce" or "porpoise" or "PIO" or whatever.

 

Speaking only for myself, I find landing with the nose higher lets the plane land with less energy. And keeping the nose up lets aerodynamic drag slow the plane, instead of brakes.

 

But of course, for the site veterans this is veering awfully close to territory already covered ad nauseum.

 

But there are always newbies checking in, and I want to be sure they get both sides, each of which may have its own merits depending on the plane and conditions.

[Roger Lee]

The big boy above also has his under fin trimmed considerably. Ours hangs down. Measuring on the ground may not tell the story. Level on the ground may not be exactly how it is in the air once air is moving over the wings. Same for landing.

[FastEddieB]

Measuring on the ground may not tell the story. Level on the ground may not be exactly how it is in the air once air is moving over the wings. Same for landing.

Not sure what you're getting at.

 

It really seems like the angle at which the tail strikes the ground is simple geometry.

 

With two caveats...

 

1) Yes, level on the ground does not mean that's the level flight attitude. That changes depending on a variety of factors. That may affect how much one will need to change that angle to get to the "tail strike angle", but the actual angle will stay the same. If, for instance, my Sky Arrow is flying 3° nose low compared to on the ground, I would have to increase the angle by 15° to hit the tail, but that would still occur at 12° pitch angle.

 

Correct?

 

2) The gear will compress a bit at higher weights or on a hard landing. This could lead to a tail strike at ever-so-slightly less than what was measured statically on the ground with the plane unladen and the gear not compressed.

[FastEddieB]

I have not read this yet, but this, from Boeing, might be of academic interest, though of course a Boeing is neither a CT nor a Sky Arrow!

 

http://www.boeing.com/commercial/aeromagazine/articles/qtr_1_07/AERO_Q107_article2.pdf

 

Interesting that the tail strike angle in a 747 is almost exactly the same as my Sky Arrow, at 12.5° (vs about 12° if I measured right). Leads me to think this may be a general design parameter.

[Anticept]

1) Yes, level on the ground does not mean that's the level flight attitude. That changes depending on a variety of factors. That may affect how much one will need to change that angle to get to the "tail strike angle", but the actual angle will stay the same. If, for instance, my Sky Arrow is flying 3° nose low compared to on the ground, I would have to increase the angle by 15° to hit the tail, bit that would still occur at 12° pitch angle.

Correct?

 

12 degrees according to your frame of reference. Pop open your maintenance manual and find the leveling means for weight and balance weighing, and use that as another reference, just to see what you come up with.

 

Additionally, it will depend on nose struts condition. As a side note, this is particularly true of OLEO struts, where temperature greatly affects the air charge pressure.

[FastEddieB]

12 degrees according to your frame of reference. Pop open your maintenance manual and find the leveling means for weight and balance weighing, and use that as another reference, just to see what you come up with.

Additionally, it will depend on nose struts condition. As a side note, this is particularly true of OLEO struts, where temperature greatly affects the air charge pressure.

I was going to argue with you, but what you and Roger are saying is starting to make sense.

 

Let me see if I can find what they use as a level reference in the AMM and I'll let you know what I find.

[FastEddieB]

Found it (should be legible if you click on it):

 

 

My plane does not seem to have the bubble level they refer to, but it looks like they use the center tunnel as a reference datum for level.

 

I should be able to zero my protractor/level using that, then simply drop the tail and measure it again to get the difference.

 

Again, this is all academic, and will not affect the way I land my plane, but its still interesting.

 

Thanks for the feedback and direction - never too late to learn something new!

[Runtoeat]

I think we're all in the same ballpark with final pitch angle. With a CTSW or CTLS, a ptich angle of 5 degrees means that the instrument panel begins to block my forward view of the runway and requires me to start looking out the sides of the instrument panel.  I am about 5' 9" and have short legs so I'm foward and up with my seat position.  I suspect that most CT owners will find 5 degrees as a very noticeable "nose up" but some may use this for their  "full stall" landing.  Others will hold a more shallow pitch where the runway is in view over the panel and do a their "full stall" in a more level attitude of about 2 or 3 degrees, gradually pulling back on the stick as airspeed slows.  Others will "fly it on" with a 2 to 3 degree angle just before touchdown. I guess I use a combined technique where I don't attempt to do the very difficult and hard to achieve totally stalled landing but to keep a slightly nose up pitch final touchdown, shooting to be slightly above stall speed just before touchdown but using squirts of power for any sinks that might pop up.  I think that the main point I try to emphasize and others have agreed with is to stay away from anything up at the 10 degree pitch angle to prevent tail strikes.  Interesting that approximately 12 degress pitch up seems to result in "tail on the ground" for most aircraft.

 

Anticept, guess you started this with suggestion for "curb feelers".  I think this might have merit for low hour students.  Kind of an audible "high pitch angle" alert during landing to train them for proper sight picture in the first hours of flight.  The scraping noise of the fin sure gets one's attention.  This would do the same without subsequent repairs. I think setting to contact ground at about 8 degrees pitch would be about right.

[Ed Cesnalis]

Dick,

 

At 30° I can't get my nose high without ballooning and at 15° I can't get slow without my nose high.  Flap setting makes a big difference. 

[Runtoeat]

Ed, flaps definitely do make a difference. I like the 30 or 40 degree flaps with short or grass runways because of the nice sight picture of the runway on final with the nose down to maintain airspeed and because of the high drag which one can use to his/her advantage to either cut power to set on a desired spot or add power to delay the landing.  If I get it right, I'm at a slightly nose up pitch of 2 or 3 degrees with 40 to 45 kt airspeed in this final phase, just prior to setting down.  If I don't get it right and I'm too fast or slightly high but have remaining runway, I get the plane back into the correct attitude and eventually find a spot to land.  if the runway doesn't allow this delay, I just go full power and go 'round.  Hope this does't get us into a flap argument.  I practice using all flap settings for landing and take- offs and each setting has it's own merrit.