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  #11  
Old 09-24-2022, 01:32 PM
jrs14855 jrs14855 is offline
 
Join Date: Apr 2008
Location: Lake Havasu City AZ
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Default Stalls

65 years of unstable approaches just as I learned in the Cub. Ag pilots take this to a whole new level. How come we're not all dead?? Its all about angle of attack.
Watch the RV4 turnback video. All done on angle of attack, airspeed is not a part of the occasion except to say that too much speed compromises the turnback.
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  #12  
Old 09-24-2022, 01:47 PM
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Toobuilder Toobuilder is offline
 
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Thanks for the response Bill. I consider myself fortunate to have a large number of military aviators as flying buddies, and your answer is in alignment with theirs.

Totally agree that some pilots have no intent or interest to find the edges and there is nothing wrong with that as long as they are aware that there is some risk of doing the "wrong" thing when that rare edge case presents itself. In these cases, some rote guidance like "never exceed xx degrees of bank when in the pattern..." makes sense.

The flip side of that of course is when you have a pilot who IS trained, proficient, and comfortable with the "...max perform the wing..." approach, and performs the landing as such. Should THIS pilot be taken to task for doing it in the civilian environment? Does this community endorse this display or condemn it as "hot dogging" or "reckless"?

There are many different skillsets among us and plenty of different "displays" of flying skill - and often not in alignment. We need to be careful not to paint all pilots with the same brush in these discussions.

And for the record, I'm not suggesting that this particular thread or the OP is going down the "judgement" path, but I've been around here long enough to know that similar threads end up that way. Just trying to get in front of the discussion in case it it goes off the rails.
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Last edited by Toobuilder : 09-24-2022 at 01:50 PM.
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  #13  
Old 09-24-2022, 04:33 PM
gasman gasman is offline
 
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In the video, you didn't mention about any feedback from the stick during any of these maneuvers, and leads to believe that the pilot is not paying attention to what his aircraft is trying to tell him.
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  #14  
Old 09-24-2022, 05:36 PM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Quote:
Originally Posted by gasman View Post
In the video, you didn't mention about any feedback from the stick during any of these maneuvers, and leads to believe that the pilot is not paying attention to what his aircraft is trying to tell him.
Interesting observation! Here's what I think is going on...

In the low speed spirals under discussion, the speed range is limited. In the RV-9A, speeds start at 70 knots and, even after the descending steep turn, don't change much, maxing out at around 100 knots. AOA never gets above 0.6, well below stall, and during the spirals per se, G force is less than 1.4. In other words, the airplane doesn't have much to say (!). And in the other airplanes in which I've flown Low Speed Spirals, I don't recall getting any cues in the stick (or wheel). (The one spiral that hit 2.18 G did that in the recovery, not in the spiral per se...)

The other point is that if the pilot is in a situation which motivated a steep turn to final, the attention paid to alignment with the runway is such that even if the airplane was trying to tell the pilot something, the pilot probably wouldn't notice it -- and that's a major point in base to final and other loss of control events. The NTSB report on the Learjet accident, NTSB/AAR-19/02, states this in Finding 8, as mentioned in the presentation. And there are many, many more similar examples to be found.

Great question! In the future, I'll try to be more attuned to any control system feedback, but my guess is that even the kinesthetic sensations will be masked by the visual inputs.

Standing invitation to anybody who wants to come fly the Expanded Envelope Exercises® with me in Savannah, including the Low Speed Spirals. These exercises are non-aerobatic, suitable for normal category, so you won't learn nearly as much in a short wing RV as you will in a more docile airplane.
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  #15  
Old 09-26-2022, 09:24 AM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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The login request has been removed from webinar, so you can watch it without giving any information. This is standard NAFI practice a few days after the presentation.
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  #16  
Old 09-26-2022, 01:46 PM
Vac Vac is offline
 
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Ed is correct, an airplane will be rock steady between 60% lift and L/Dmax (the 70-100 speed range at 1 - 1.4G's mentioned).

At less than 2 G's there would be little or no aerodynamic buffet in a 3/4/6/7, even at stall. 8's a bit different and can provide better buffet cues at 1-2 G's. Buffet cues in the 4 don't get noticeable until north of 2G's. Here's a 1.6 G stall in a 45 degree banked gliding turn--no aerodynamic warning: https://youtu.be/KTUKR6PiP8s. The stall occurs at a normal Vref, I'm simply asking for more G's than the airplane is capable of generating at that speed, IDLE power and bank angle (where the lift is pointed). Here's what's happening out on the wing as you approach the stall, notice how solid the airflow is even with the stall warning going off (set to FAR 23 criteria): https://youtu.be/W9Zr-Gd4IoI. Here’s a few actual stalls under the same conditions, and the take-away is how rapidly the stall progresses: https://youtu.be/j2H-ssR83_g.

It's a bit of a common misconception that a stable, descending gliding turn is "unloaded" (i.e., low G). A 45-degree banked gliding turn is still flown at 1.4 G's, just like a level turn, so stall speed is going to increase by about 15% and you don't have a lot of "energy/lift reserve" if you pull much harder at that bank angle.

Thoughtful presentation, Ed.

Fly safe,

Vac
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Last edited by Vac : 09-30-2022 at 06:55 AM. Reason: Added speed reference to accelerated stall demo
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