Jump to content

Flight Design full stall landing


Ed Cesnalis

Recommended Posts

It's perfect timing I get to go out into the world again tomorrow. It never going to have an ending with a definite conclusion or it would have been settled decades ago by people that flew before us, but its been a fun ride.

Until our next discussion have safe flights.

 

Take care,

Roger

 

 

Hi John,

It's like looking for the perfect president. Half will always like him and the other half will dislike them and that debate has gone on since the first president.

Link to comment
Share on other sites

  • Replies 73
  • Created
  • Last Reply

. . . "It's like looking for the perfect president. Half will always like him and the other half will dislike them and that debate has gone on since the first president." . . .

 

But now it's quite different.

We have a self appointed king. :)

Link to comment
Share on other sites

Roger,

 

Your arguments are fluid, having the target of we are all right, now morphing to we are all the same. I don't buy it.

 

This go round you floated the '40 is same as 50' trial balloon that got shot down pretty easily so you ended with there is no real difference between us, seems you've decided we really all land at the same speed.

 

Truth is we don't all land the same and their are 2 camps. Slow camp more often involves closed throttle, aft stick at touch down, slow approach speed, and 30 degrees. Fast camp more often involves partial throttle, 15 degrees or less, faster approach speed, and centered stick, allowing it to settle.

 

Many of us cross the line and use the other camps technique on occasion and when I do the speed difference is meaningful. The fact that fifteen and thirty have similar stall speeds doesn't mean you will land at similar speeds even when you change the setting and change the landing goal.

 

Not long ago I posted a video and named the thread CTSW Normal Landing and immediately there was controversy and you changed the name to My Normal Landing becuase I used a closed throttle and 30 degrees and did a full stall landing. Posters wanted the difference to be known, yet in the end the argument has morphed to 'no meaningful difference, we all land at the same speed'

Thats just not true even if it results in one big happy family.

Link to comment
Share on other sites

The level flight stall characteristics demonstrate that FD has located the aft stop at a conservative location. I have to stall in a nose high attitude to get more than a mild mush. Our full stall landings are limited as well, I have had my stick at the stop while several feet in the air and found no need for throttle because the sink was well controlled.

 

To me having the stick all the way at the stop several feet in the air sounds like an accident waiting to happen. At this point the sink rate can only increase, and you have no way other than throttle to get you out of trouble.

Link to comment
Share on other sites

To me having the stick all the way at the stop several feet in the air sounds like an accident waiting to happen. At this point the sink rate can only increase, and you have no way other than throttle to get you out of trouble.

 

I agree totally, I was simply pointing out that the stop is located conservatively. When I felt the stop while I was sinking through several feet I was ready to advance the throttle but the rapid sink never developed.

Link to comment
Share on other sites

I am not a carry power to touchdown kind of guy, but if you want to land as slow as possible then you can do that by carring some power. The problem is if you carry to much then you will drag the tail.

 

I use and teach 15° flaps for normal landings (near stall speed). This is what was being taught by most of the experienced CT instructors and pilots when I started with the CT in 2007, and this is what I use to this day.

Link to comment
Share on other sites

I agree totally, I was simply pointing out that the stop is located conservatively. When I felt the stop while I was sinking through several feet I was ready to advance the throttle but the rapid sink never developed.

 

Until you do the testing and engineering you have no base for this statement. The stabilator has 23° travel stop to stop. This is 5° more than the Cherokee that I just checked. It is possible that increasig the travel could cause the stabilator to stall rather than the wing. If this is the case then things would get ugly quick.

Link to comment
Share on other sites

The stabilator has 23° travel stop to stop. This is 5° more than the Cherokee that I just checked. It is possible that increasig the travel could cause the stabilator to stall rather than the wing. If this is the case then things would get ugly quick.

A tailplane stall is pretty ugly, especially since the correct reaction is not intuitive. There was a video of a plane that got icing on the tail feathers. Here's a quote from the AC on it.

 

 

(6)

Another hazard of structural icing is the tailplane (empennage) stall. Sharp-edged surfaces are more susceptible to collecting ice than large blunt surfaces. For this reason, the tailplane may begin accumulating ice before the wings and can accumulate ice faster. Because the pilot cannot readily see the tailplane, the pilot may be unaware of the situation until the stall occurs. There have been reports of ice on the tailplane without any visible ice on the wing. This can occur if the tailplane has not or cannot be deiced.

(7)

A tailplane stall occurs when, as with the wing, the critical angle of attack is exceeded. Since the horizontal stabilizer counters the natural nose down tendency caused by the center of lift of the main wing, the airplane will react by pitching down, sometimes uncontrollably, when the tailplane is stalled. Application of flaps can aggravate or initiate the stall. The pilot should use caution when applying flaps during an approach if there is the possibility of icing on the tailplane.

(8)

Perhaps the most important characteristic of a tailplane stall is the relatively high airspeed at the onset and, if it occurs, the suddenness and magnitude of the nose down pitch. A stall is more likely to occur when the flaps are approaching the fully extended position, after nose down pitch and airspeed changes following flap extension, or during flight through wind gusts.

 

Having a greater range of travel is one thing - is there a greater range of negative travel? Can the stabilator go down far enough to induce a tailplane stall? If hte extr 5 degrees were all on the up side it wouldn't make any difference as far as stalling propensity.

Link to comment
Share on other sites

Icing is a killer. We aren't supposed to fly in icing conditions or if you leave your plane outside and ice forms over night it shouldn't be flown until all ice has been removed.

 

 

It's not a flaps issue, more of too slow and too much pitch in the stab with aft stick and a nose high attitude. I haven't seen or heard of a CT with a tail stall, but with a full stabilator it may (????) be possible under just the right circumstances. Maybe FD has that calculated and it won't happen?? I don't know how all the engineering numbers for a tail stall add up in the CT. That's way out of my league. I have heard of lots of other planes that that has happened to, but not a CT yet.

Link to comment
Share on other sites

Roger, Meade's material contains the following warning on tail stalls:

 

"...Application of flaps can aggravate or initiate the stall. The pilot should use caution when applying flaps during an approach if there is the possibility of icing on the tailplane."

 

So, if a tail stall is a possibility, then less flaps the better....

 

No.

That is not what the text is implying.

 

In the event that the tailplane is iced up, then the application of flaps could make it more severe.

 

Application of flaps will not cause an undisturbed tailplane to stall. Otherwise, the aircraft could not be certified to begin with.

 

* Aside from that, and as we all know well, the CT is prohibited from flight into known icing conditions anyway. :)

Link to comment
Share on other sites

I don't think a tail stall is anything that can occur in any normal plane under any normal circumstances.

 

If one has done snap rolls, you know that stick full back abruptly - literally as abruptly as you can pull - does not cause a tail stall. The main wing stalls with no hints the elevator losing effectiveness. I've only done fairly basic aerobatics, so there may be advanced maneuvers where it's a factor, but that's beyond my pay grade.

 

If the elevator changes shape, as in icing, all bets are off. But that's a rare occurrence - or at least it should be.

Link to comment
Share on other sites

You guys missed my point to CT. He said that the stops were set conservatively. I just pionted out with 23° of travel from stop to stop that if it was increased it could cause the tail to stall. With the airplane set with in limits I don't think it would ever be a problem, but the setting might not be as conservitive as he thinks.

Link to comment
Share on other sites

Tom, you didn't answer my question, which is where is the extra travel? Is it down (more aggressive) or all up (what difference does it make)?

 

Jim, sorry I missed the question. Per the book the extra travel is down. This could just be the difference in where they call nuetral to measure the travel from.

Link to comment
Share on other sites

  • 4 weeks later...

Sorry to start this back up, but I got thinking about full stall landings and ground effect. I found this, which leads me to beleive that since AOA is reduced in ground effect (to maintain a constant lift) then stall speed would be reduced (since a stall occurs when you reach the critical AOA and ground effect lowers the AOA), so a full stall landing in ideal conditions would be slower than stall speed at altitude - correct? There's also some discussion of how ground effect might mess with your airspeed indicator.

 

There's also some pretty interesting data on ground effect. At a height of 1 wingspan the reduction in induced drag is only 1.4%, but when you get down to 1/10 of the wingspan (probably about where my low wing plane is on the ground) the reduction is over 47%.

 

http://www.faatest.com/books/FLT/Chapter17/GroundEffect.htm

Link to comment
Share on other sites

  • 2 months later...

I applaud the evolution in your 'take' on landings but there is some contradiction in what you are saying now. You advocate landing in a crosswind on one wheel yet state that the slip isn't held all the way to the runway. In a crosswind you are landing on one wheel because the slip is still there. In a smooth crosswind, like at the beach there may be no gradient and a lot of side loading if you don't contact with correction in. Here in Mammoth not so much.

 

You say that stalling is impossible due to the flare if done properly. There is a big if in there and stalling is possible, rapid sink is more likely. You can only arrest your sink with flare for so long before the rate of sink accelerates.

 

My nosewheel can 'grab' even if I touch down on my mains and hold the nose off, the longer I hold it the less it might grab if not aligned. All unwanted turning from the nose wheel isn't from touching down in the wheel barrow configuration that is simply the worst case.

 

I say its a good idea to get straight before contact but not always a big deal. If my upwind wheel is low and I am going to softly contact on it my CT will pivot into alignment softly and gracefully.

Link to comment
Share on other sites

CTLSi,

 

Reference your last sentence in the previous post about the Navy and Air Force no longer train pilots to straighten the nose if in a crab etc.. As former head of the Navy's flight instructor school, I can assure you that is not the case. If your landing on glare ice that would be an accurate statement because your just like a hockey puck. Otherwise any pilot should strive to land aligned with the intended direction of landing.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.


×
×
  • Create New...