Lessons Learned at the Talkeetna Fly In - A Bit Too Slow

[BC12D-4-85]

Are there any vids of these wings from above or top of tail with yarn tufts installed? Just curious about how much air flow is left attached and where.

Gary

 

[Eddie Foy]

I have read all of the comments here. Once again I will give my opinion.
This is an airshow maneuver. It has no use in real life. I dont spend a lot of time analyzing it because I have no need or desire to go there.

It is a risk versus reward kind of thing.

He took the risk, now he reaps the reward. A broken airplane.

 

[SpainCub]

Again, nothing more heart breaking and painful to see this happen, and thank you for sharing for the rest of us to lear from it.

I'm 50/50, I still see the initiation of the stall as an aileron induced stall do to an increase in Drag. You need to look at the first three frames when the video is in slow play, loop those frames and you could see a slight input in aileron, well before the wing is noticeably dropping, then as the input of aileron is increase, so is the drop and the end effect of the video and the possibility that wind direction might have impacted the laminar separation bubble created at these high AoA, where a hysteresis occurs, pilot feels the wing drop sooner that one can visualise it and that drives them into aileron input, then back to comments before. Certainly way to close to the edge of the flight envelop to even consider comping out of that one, not mater how quick once is in reacting to the wing drop...

@Dave, theoretically, there is still too much high to be in Ground Effect, the influence on the surface plane is still in Far-field effect, considering h/c ratio as a factor of influence to enter ground effect, where h is hight and c is cord of the wing. BTW Dave, I'll give you credit, your are absolutely correct, once the wing stops flying, you are in effect neglecting Bernoulli...

​

 

[skywagon8a]

... I still see the initiation of the stall as an aileron induced stall do to an increase in Drag.

Coupled with the increase in power and the lack of right rudder. I did not see the rudder move as the power was increased. That rudder should have been hard to the right.

 

[aktango58]

This is an airshow maneuver.

Performed at a fly-in, ie: Airshow



It has no use in real life.

Well, Not true. We as pilots should be doing this often, especially if we are going to land off airport ever. Consider that this is just slow flight, just above a buffet- same thing we do in training. The difference is that this plane had high lift devices that changes it's deck angle, and was below the 1,500' recovery faa requires for normal. Had he been doing this at 3,000' we all would be thinking it was just any day.

I dont spend a lot of time analyzing it because I have no need or desire to go there.

Every time you stall you have been there. The discussion might help as the principals are the same on all planes, and a full stall landing uses these very same elements being discussed.

It is a risk versus reward kind of thing.

Don't practice this type of flight condition you won't be able to land worth a crap.

He took the risk, now he reaps the reward. A broken airplane.

As many have themselves earned the 'hat'.

 

[Eddie Foy]

Well George. You know what they say about opinions.

 

[LMartin]

About that commentary, "The headwind subsided". That couldn't POSSIBLY have anything to do with it, because that's the foundation of the downwind turn peril and we've all heard ad-nauseum that no such phenomena exists. Free moving airstream etc... Once again inertia is the wildcard that those who haven't experienced it cannot understand. If not for the properties of inertia, the aircraft could immediately accelerate to maintain a constant airspeed, but obviously it can't so it flopped out of the sky. Just like when a last minute gust lofts you back into the air and then drops you if you don't immediately push it over to reclaim your energy. But again, this must all be imagined since it certainly can't/doesn't exist in our free airstream...

Okay, back to the immediate subject. No I didn't see any significant rudder either, but I do agree it would be hard not to instinctively push the stick over.

--P.S. A GoFundMe page. Seriously??? He prangs his plane showing off and then passes the hat to fix it! Talented stick or not, that's pretty low rent.

Yes. CFI Rod Machado would say, "The airplane doesn't know what the wind is doing." Any pilot who's ever worked an airplane low and slow would reply, "Right, the airplane doesn't know, but the pilot better." Some wind shifts catch us at unrecoverable moments.


Sent from my iPhone using SuperCub.Org mobile app

 

[aktango58]

Well George. You know what they say about opinions.

Thank you are right and I am wrong

I am just glad we all can discuss it this way.

Here is an article about saturday up at home. Maybe some of my comments are a bit sharp, but here is another example of a pilot not properly controlling his aircraft at low speed. The results were very bad. My friend and hunting partner was one of the EMTs, and I knew the pilot and plane.

https://www.adn.com/alaska-news/201...ash-rescued-by-local-residents-as-water-rose/

 

[SpainCub]

Coupled with the increase in power and the lack of right rudder. I did not see the rudder move as the power was increased. That rudder should have been hard to the right.

Agreed, corrective input would have been rudder input... but I see a very subtle input from the stick, lowering left aileron for three frames, before the wing begins to drop slightly... I think that even at this h/c ratio, near field will begin to creep in with an increase in drag, thus repetitive bursts of abrupt laminar separations (really fast little burst... influenced but the slip stream on the vorticity of the prop/wind direction change/drag increase for the "slight" nearfield effect or the ground plane... this is still a possibility.
If you ever looked at a slow and light stream of water coming down a piece of glass, like a windshield while when washing your car, play with it and touch the stream, you will see it change course ahead of where you placed you finger, it's a chain reaction of friction moving upwards do to drag.

 

[skywagon8a]

Also the power was cycling. It wasn't a steady change of power, up/down/up etc.

 

[mvivion]

George Tango, I wasnt speaking to you, but to Mike V, George M and Eddie F. Both George M and Eddie F
"like"ed the post from Mike V to which I had responded. All three are experienced aviators who may have flown a slatted Cub, but likely do not fly one often, nor own one, as assumed by me through their agreement with MTV's comment.

The slatted planes are not like any other a/c, and when flown in high AOA regime can perform like no other a/c.

I do not own one, but have flown several of the Valdez hotrods, and others, having built one and fabricated parts for several others.

George Tango, in the video, about 100 feet before the stall the aircraft was higher and began a descent (effectively, this was an increase in AOA, due to the descent).......right rudder was minimal, and neither before power application nor after, was additional right rudder commanded.

The airplane is flying on reaction lift (bottom of the wing, no Bernoulli) and hanging on prop and thrust at that point, but the descent (angle of attack increase) amd no additional thrust commanded caused the available lift to be exceeded by the weight of the a/c. That is my assessment.

I have no moral staement. We need to pilot effectively by knowing and providing inputs necessary to whatevrr a/c we are flying.

Wish we could hear from Tom on this.

Dave,

My point was simply that when you drive a true STOL equipped airplane like this to it's maximum AOA, and it departs, the departure will probably be a pretty aggressive one, and if this is the case, recovery will require considerable time and altitude. The beauty of the slatted airplanes is that they will continue to fly at very high alpha, and will tolerate a lot of "abuse" in this regime. But, if a wing really departs, as clearly happened in this case, it's likely to take a while to recover. My point was simply that he probably didn't have enough altitude to recover from that sharp a wing stall without hitting the ground.

Full right rudder may have started the recovery, and clearly would be the appropriate response to recover. Whether it would have permitted the airplane to actually recover before ground contact is pure speculation.

MTV

 

[behindpropellers]

I wonder if the insurance companies are watching these videos and considering premium increases.

 

[Dave Calkins]

Dave,

My point was simply that when you drive a true STOL equipped airplane like this to it's maximum AOA, and it departs, the departure will probably be a pretty aggressive one, and if this is the case, recovery will require considerable time and altitude. The beauty of the slatted airplanes is that they will continue to fly at very high alpha, and will tolerate a lot of "abuse" in this regime. But, if a wing really departs, as clearly happened in this case, it's likely to take a while to recover. My point was simply that he probably didn't have enough altitude to recover from that sharp a wing stall without hitting the ground.

Full right rudder may have started the recovery, and clearly would be the appropriate response to recover. Whether it would have permitted the airplane to actually recover before ground contact is pure speculation.

MTV

sorry. This is where you are wrong. Full right rudder, additional power, and a INCREASE in deck angle will save the situation. (With an rc of sufficient power)

With a hotrod Cub we have to use all the power available and lotsa rudder

The R/C guys have been hovering airplanes hanging from the prop for about 35 years. No slats, lotsa rudder and power.

Not everyone who flies these hotrods Cubs can utilize these principles in high alpha (high angle of attack) flight. I can count three that I know. Surely there are more.

i am guessing any RC guys reading these words dont question my statement, and the full scale Pilots struggle with it.

Mike. Eddie. George. Have you flown one of these planes? Freindly question to know if you have experienced these planes.

They are different, the available thrust and quick spool up is a big part of the equation

 

[stewartb]

C'mon, Dave. Unless thrust exceeds weight and you're pointed straight up the wing's lift contribution requires an airspeed component. Regardless of what gadgets we add to the wing there will be a point at which it no longer supports weight. Tom is at the top of his craft with respect to flying that plane but when you balance on a ball bearing for long enough even the best guys are going to fall off. I have no judgement of right or wrong for the pilot. I think the notion of a low level slow flight exhibition is dumber than f--k. Speaking for myself the video was mildly interesting at first view because Tom has never added P-Stol flaps and the AOA shows it but there are variables a video can't illustrate, like the wind, so mild interest has evolved into no interest for me.

 

[Mauleguy]

I disagree with this being about slow flight, I do slow flight every time I go out and play off airport but I am never near the buffet of a stall. The picture out my airplane is the same as when I am wheel landing. There is no need to slow the airplane to the point of a buffet if you are slowing your airplane up to see something and you have to get that slow you probably should pick another spot.

 

[SpainCub]

Dave, don't forget Re (Reynolds number), this is why there is a diminishing return in increasing Chord and why you get more from increasing aspect ratio as a means of improving lift. Moving from a model to full scale is a topic on it¡s own, but all things considered, especially Re, to validate your comments, it would be like adding very large prop to plane in our size range of nearly 150hp and MTO of <600 lbs. (Used the SAE "Heavy Lift Cargo Plane" to gauge power to wight ratio to estimate range) and I bet those acrobatics planes are way higher power to lift ratios than those.

 

[Wingwrench]

I've only flown one slatted cub, first 20 hours on one I put together for a customer. My experience is the same as Dave's. Until I saw the aileron deflection I was surprised it departed. The airplane is very easy to fly at high AOA but you cannot move the ailerons, the instant a wing drops you pick it up with rudder. It will fly all day like that as long as the oil temp stays down regardless of wind. Once the nose came around there was no saving this one but there was plenty of time before that to correct it with rudder and power. You really have to experience it to believe it, it is a blast to fly.

 

[Dave Calkins]

SpainCub, the easiest to fly of the RC's I am speaking of (we call them "3D" airplanes) are the very over powered ones. The "lesser"-overpowered ones have less margin.

Stewart. If the Thrust! of the A/C contributes more, the load on the wing is less. Increasing AOA puts more load on the prop.

You'd have to ask Wayne, Goza, Peppards, Doyle, Kallam, and that bunch, but It felt like I hung Kazoom from the prop for several seconds, with a view of the a/c perfectly vertical at 1500 feet AGL. Dunno if any video exists.

 

[stewartb]

If you can borrow one of those $200K+ Cubs and promise to hover it on the prop at 25' above the runway at Skwentna? I'll delay my fishing for a couple of hours to come watch. And I'll bring a GoPro.

I'm just funnin you. I'm going fishing.

 

[Cub Special Ed]

Big rc in this video. https://youtu.be/jNlaI-GnRG4

 

[ak49flyer]

Im not trying to stir the pot here, just trying to understand- Dave, if the wing is primarily flying on reaction lift in these ultra-high alpha regimes, (which I tend to agree with, by the way, bring a RC guy I get what you're saying), why do the slats enable these angles of attack? I thought the whole point of the slat was to keep the air attached to the top of the wing longer? Just something I've been mulling over; maybe I misunderstood what you were saying. I'm not disagreeing, just trying to understand...

 

[Wingwrench]

About the 9 min mark is the smoke trail with slats.

https://www.youtube.com/watch?v=q_eMQvDoDWk

 

[Dave Calkins]

Ak49, yes the purpose of the slat is to delay separation of airflow at higher angles.

I believe that in ground effect (commonly one half wingspan from the ground) reaction lift is the king.

I have been thinking about how the slat "cups" the air and sends it over the wing. What surprises me is that I have never sensed any "pitch up" when the slats deploy. I

Stewart B. We are not literally hovering on the propeller, or are we? Kazoom seemed to be the brief time I flew it. Yes, its probably over $200k.

 

[Eddie Foy]

Dave,
Define what you are calling reaction lift.

 

[stewartb]

You're the one that brought up hovering on the prop. I guess I'm stuck in the old school thinking that airplanes with wings require some element of airspeed to make the lift required to hold the airplane up. I like the idea of slower control envelopes opening up new opportunities and am personally invested in it but with all airplanes there is a point where too slow is too slow, as demonstrated in the video.

Here's a good paper discussing lift.The science is interesting and the delivery is amusing.
http://mb-soft.com/public2/lift.html

 

[Dave Calkins]

Eddie. The relative wind hits the bottom of the wing and is vectored down.

Have you flown a slatted airplane? I had asked you that several times. Thanks.

 

[Dave Calkins]

Stewart. In "high alpha flight" ( what Tom demonstrated in Talkeetna), propeller thrust is providing a portion of the weight lifting.

the more thrust, the more weight lifting. Any argument?

but the extra thrust must be vectored (lotsa rudder)

.....and if vectored to Cause a yaw, the flow increase under the left wing may have picked it up. And certainly the increased thrust would be assisting in lifting the a/c.

 

[OLDCROWE]

The relative wind hits the bottom of the wing and is vectored down.
.

Dave, from sailing in days gone by I understand relative wind and from that a couple of questions and observations.

When the realitive wind is vectored down does it attach and stay attached to the bottom of the wing making for an appearent wind lift vector or is it deflected away leaving the bottom of the wing as a turbulent zone. I was fortunate to meet and fly with Wayne in the prototype for a few days and was amazed watching the slats come on and off and saw part of his string study video and remember the tops of the wing but not the bottom, or did he care?

With fast boats tuned sails can work at very high angles of attack (close to the wind, say 35 degrees off) but you can't start with that high of an angle of attack, you have to round up to it with attached flow over the top as the realitive wind angle swings forward (reverse of powering downwind on a broad reach for amayzing speeds. When going up wind with a Jib if you loose the attached flow over the chord it immiediately back winds and you're toast in short order. The confusing part here to me is a high performance boat will point higher into the wind without a jib than with but the speed rally falls off, so it would seem to my pea brain that the slats are not truly generating lift as an extension of the wing like a jib does both with attached flow and with slot flow but floating slats are rather forcing more air along the top chord to stay attached to the wing via the slot only. So if that's the case I can absolutely see why the stall would be so very abrupt.

Does this make any sense at all?

Kirby

 

[stewartb]

Interesting. I don't know enough to comment on what the prop's contribution is. To me it creates airspeed and that allows the wing to provide lift. I can control the airspeed and lift by changing the AOA and power but there's a limit. I don't have enough power to overcome gravity. I'll leave the hovering to helicopter pilots.

 

[hotrod180]

Sometimes prop blast can be a substitute for airspeed re lift.
Witness raising the tail before beginning the takeoff roll.