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AoA according to Backcountry182


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You would want to be 100% confident in that indicator and it’s accuracy! As well as being right at the top of your flying game! That close to the stall requires a lot of recency, skill, and practice regardless of What’s installed on the dash! 

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Every flight begins and ends close to the stall.

Stall warning indicators (lights or horns) used to be considered important safety gear in GA aeroplanes.

ASIs are, themselves, rarely accurate at low speed and high AoA. But one needs to know the quirks of a given plane and its instrumentation.

AoA is better than airspeed as a stall warning. For a start, they're (usually) up on the dash, visible while looking out; their warnings are independent of aircraft weight. An ASI is not and therefore not as reliable.

There's no reason to believe that having an AoA display would encourage a pilot to fly near the limit (or the limits of his/her competence).  But there are times when being confident of actual lift reserves can save the day.

 

If nothing else the instrument serves as an educational device.

Edited by Garfly
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Put all your trust in an instrument would you? Do they need electricity to make them work? Do they need calibrating? Do they distract you from looking out?

Even if they are perfect and never fail you can quickly go from near max lift to zero lift in hilly country at low level. I haven't had a stall warning in any of my planes this century and  I manage to get by, but I don't try to push the boundaries.

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11 minutes ago, Yenn said:

Put all your trust in an instrument would you?

No.

 

(But I do amaze myself with the faith I put in that fire breathing chitty-chitty-bang-bang contraption up front.  😉  )

Edited by Garfly
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16 minutes ago, Garfly said:

Every flight begins and ends close to the stall.

Stall warning indicators (lights or horns) used to be considered important safety gear in GA aeroplanes.

ASIs are, themselves, rarely accurate at low speed and high AoA. But one needs to know the quirks of a given plane and its instrumentation.

AoA is better than airspeed as a stall warning. For a start, they're (usually) up on the dash, visible while looking out; their warnings are independent of aircraft weight. An ASI is not and therefore not as reliable.

There's no reason to believe that having an AoA display would encourage a pilot to fly near the limit (or the limits of his/her competence).  But there are times when being confident of actual lift reserves can save the day.

 

If nothing else the instrument serves as an educational device.

Agree completely and a good short field operator at the top of their game is great to watch. Watch some of them constantly moving then elevators to see how much they have left. It’s awesome to watch.  Personally I don’t fly enough anymore to have that level of confidence or motor skills.Once when I was doing it every day absolutely! These days I prefer a nice big buffer 1.4 VS as a min manoeuvring speed back to 1.3 over the fence. No need for a stall warning then it never gets close enough! But i can still appreciate a good set of hands and feet doing it well. 

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If you don't trust electrical gadgets, well this old chap has an app for that.  

 

 

Actually his video is well worth a look; he urges on us the educational value of AoA awareness; of fixing its relation to stall/stick position in our muscle memory. 

 

(Like training wheels, the indicator could be seen as less important the more one's intuition picks up on it.) Anyway, if you don't want to spend 14 mins watching the vid, I've transcribed his concluding remarks:

 

"The final overwhelming advantage of using angle of attack to monitor slow flying is that with every approach or practised forced landing, the pilot reinforces his or her intuitive grasp of the relationship between the position of the control column, the position of the elevator, the angle of attack and the stalling angle.

 

It is sadly apparent from reading accident reports that not all pilots have had a sound intuitive grasp of this relationship and this can put any aircraft at risk, from the humble light aircraft to the mighty Airbus.

 

There is a lot of discussion, currently, about pilot distraction in the causation of loss of control in flight. In cases of unintended stalling, I think that this is getting it the wrong way round: all pilots continue to be able to keep their wings level whatever else is going on. And in the same way, they should also possess, to almost the same level, the intuitive awareness that pulling back on the control column increases the angle of attack and that at the end of this procession lies the stall" 

 

 

 

 

Meanwhile, over at FLY8MA, he's been doing some real-world performance testing on his Bearhawk Patrol; specifically the differences between flying light and flying heavy.

 

(Results summarised at 13:25)

 

Among other things, he turned up a 7 mph (6 kt) difference in stall speed. That's quite a lot at the bottom end. In a tight spot, say a forced landing into a short field when you're light, if you follow your AoA, it might lead you to a 6kt slower touch down (crash).  Slower, that is, than the target speed you'd otherwise have flown off your ASI (based on gross weight). Excess lift reserve = excess energy to dissipate. (So more ouch.)

 

Of course, the truly intuitive flyers among us will be doing that anyway, by feel.

 

 

 

Edited by Garfly
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Plenty think they have a single stall speed for their plane. Change of weight means a new stall speed applies. Margins are something else. High(er) margins increase safety but you will use more runway. You should have a pretty good idea of where you will touch down without forcing it ON.. An AoA or reserve lift indication is a good back up. Like all instruments you don't just fly on it or you will chase it. It's more appropriate to fly an attitude and check it's effect on what you are getting  from it and readjust the attitude if necessary.. An AoA can confirm an efficient holding speed or even cruise speed but it's not usually used that way as there's other ways of doing it. but it's a back up Holding often is done at  speeds with not a lot of margin for error and at levels where you can get icing which will up the speed at which the plane stalls.

 When you go flying in the large big tubes and can't see who's flying it, the landing speed...Target Threshold Speed is calculated on real weights to one knot. Similar for takeoff where the V1  Vr and V2 speeds are calculated along with the trim position. In older fairly conventional planes the prestall buffet was often enough to provide a good warning. The usual mandated warning horn can have a 9 knot margin.  I'm all for extra valuable information to the pilot where it doesn't adversely draw too much attention from other things. .  AoA on a head up display would be fine. Nev

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As I understand it (and as BC182 says in the video) AoA indications are independent of a/c weight, Density Altitude, and of G-load, too. 

Edited by Garfly
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Certainly good enough for this guy. Stuck out in front of the wing, though.

 

(Again, he emphasises stall/stick position.)

 

 

Edited by Garfly
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Good video - very clearly articulated.

 

Off topic question: Why did he raise the undercarriage ? My guess, just habit, because I wold surmise that on this aircraft it can not make any difference to drag.

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20 minutes ago, planesmaker said:

Stall stick position would change would it not with a different cg? If I load passengers in rear seat it would mean I need less rearward stick movement to stalling AofA

You'd think so, but this is how the Royal Newcastle Aero Club training manual puts it: 

 

http://www.rnac.com.au/files/2018/03/5.00-Stalling-v1.02.pdf

 

Excerpt:

"Stall stick position: That elevator position required to achieve the critical angle of attack. The control column will always be in the same position to achieve the critical angle of attack in any given configuration. The stick force does not matter, the STICK POSITION does.

The angle of attack of the wing is caused by the angle of deflection of the elevator. If we pull the stick back too far and deflect the elevator too far we will increase the angle of attack of the wing beyond the critical angle and stall it."

 

Whether "in any given configuration" takes CG into account, I'm not sure.

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Clear as mud! Take it to extreme with rear cg you could be at position to have full forward stick and still not be able to prevent stall. Obviously this would be outside cg limits. 

Edited by planesmaker
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This might be clearer, then, in that it spells out "for a specific flap setting or centre of gravity"

It is from CAAP 155-1(0). 

 

3.14 Stick Position And The Stall

3.14.1 An important aspect of both normal and aerobatic flight is the relationship of the stick position to the angle of attack of a wing for a specific flap setting or centre of gravity, in particular at the stall. The fore and aft position of the control column determines the angle of the aircraft's wings to the airflow. For example, the stick positions for cruise, glide and the stall move progressively aft. Once the stick position for the stall has been determined (and remembered), it can be used as a measure of whether an aircraft's wing is stalled or not. If the stick is forward of the 'stalled stick position', the aircraft will always be in unstalled flight, regardless of aircraft attitude or airspeed.

3.14.2 Appreciation of this concept, and the ability to recognise and apply stick position to achieve CLMAX (that is the point just before a wing stalls) can increase awareness and enhance a pilot's confidence and aircraft handling at this critical phase of flight.

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It's clear if you think it through." For any given configuration" the  Stick Stall Position will be the same. Configuration includes actual C of G at the time .

  Stall is an angle of attack not just a speed. The elevators are the control that the pilot uses to change that. If the plane's C of G is far enough to the rear it may stall where ever the stick is.. Having C of G forward or limiting UP elevator travel may make the plane unstallable but may also make it harder to land.

  I don't see making the plane unstallable is the way out.  A talk we had a few months ago about inadvertent stalling  put the willies up me.. IF you have even ONE inadvertent stall, count yourself lucky and do something about your skills in this area. It doesn't HAVE to be like that and you are on borrowed time if it is. . Nev

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Skippy I agree with you that raising the undercarriage would not change the drag while you are flying, but I think you are looking at a sea plane and the drag would be excessive with the wheels down on the water.

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2 minutes ago, Yenn said:

Skippy I agree with you that raising the undercarriage would not change the drag while you are flying, but I think you are looking at a sea plane and the drag would be excessive with the wheels down on the water.

Absolutely correct - just me being picky.

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