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lr172

Well Known Member
The other day I overshoot my final turn due to a stiff crosswind and I banked more than normal to compensate (didn't check, but probably around 45* or less). I don't believe I loaded up any G's, as my decent increased and I added power (My approaches are done at 85 MPH until short final). I had no negative effects or outcome. However, it got me thinking and researching to be sure I learn from this and stay safe.

It seems that bank angle in itself isn't a factor, it is the adding of G's through up elevator that causes the AOA to increase and thereby the stall speed increase. I have a D100 with an AOA indicator and my question is, if I am in a bank and near the stall point for my current configuration, will I get an AOA warning similar to when I stall level. I assume this is the case, but wasn't sure and looking for confirmation from those more experienced in this area.

Dynon recommends doing 4 stall maneuvers for AOA calibration (power-off/Clean & dirty + accelerated/Clean & dirty). I only did the power-off dirty calibration, as I didn't want the alarm going off too early in landing configuration. I am guessing they recommend this because the AOA at stall is less or more in the different configurations. Any guidance in this area? I am now thinking that I want a broader range of warning to be sure that I get a warning for the situation outlined above.

Thanks,

Larry
 
Yes, absolutely. AoA cares not about bank or pitch attitude, it only cares about AoA which is directly related to how much the wing is being asked to lift. If it's being asked to lift twice the weight of the aircraft (i.e. 2G) whether banked, wings level, or inverted, the wing will experience a higher AoA which will be reflected on the instrument.

The actual AoA will vary slightly with configuration (i.e. flaps up/down) and Dynon's method will produce something of an average. I'd recommend doing the sets they suggest; it worked extremely well on my D10A.
 
I've been in an RV with a Dynon AoA system that was alerting on high AoA.

The plane was pointed straight down, was doing about 100 knots indicated, and was stalled.

It's true AoA. It doesn't care about bank, pitch, or airspeed, just the angle of airflow over the wing.
 
Level turn is not a 1g turn...

Just to clarify, a coordinated LEVEL turn is not a 1g maneuver. At any bank angle the load factor increases, proportional to the inverse of the cosine of the bank angle . Recall from primary training that a 60 degree bank turn creates a 2g load factor and a stall speed of 1.4 times the 1g stall speed. The beauty of AOA indicators is that they accurately report the approach of wing stall at any load factor and bank angle.

With increasing bank angle it IS necessary to add up elevator to maintain a level turn.

Hope this doesn't sound "preachy". Easier to read here:

https://en.wikipedia.org/wiki/Load_factor_(aeronautics)

- Roger
 
dynonsupport said:
I've been in an RV with a Dynon AoA system that was alerting on high AoA.

The plane was pointed straight down, was doing about 100 knots indicated, and was stalled.

It's true AoA. It doesn't care about bank, pitch, or airspeed, just the angle of airflow over the wing.
Click to expand...

Would you also recommend that I do the full calibration for the best alerting? Does it average the different AOA's or always provide the most conservative warning? I thought I read that it was the latter.

Larry
 
RKellogg said:
Just to clarify, a coordinated LEVEL turn is not a 1g maneuver. At any bank angle the load factor increases, proportional to the inverse of the cosine of the bank angle . Recall from primary training that a 60 degree bank turn creates a 2g load factor and a stall speed of 1.4 times the 1g stall speed. The beauty of AOA indicators is that they accurately report the approach of wing stall at any load factor and bank angle.

With increasing bank angle it IS necessary to add up elevator to maintain a level turn.

Hope this doesn't sound "preachy". Easier to read here:

https://en.wikipedia.org/wiki/Load_factor_(aeronautics)

- Roger
Click to expand...

Sounds more educational than preachy. I understood that I would pull G's to stay level in the turn, but if I don't pull back and let the nose fall, is it true the G loading is closer to 1 and risk of stall lower or is that a misunderstanding on my behalf?

Larry
 
The way I understand it, if you don't require the wing to maintain altitude (descending turn), then you're no longer requiring the wing to counteract gravity, so you can dedicate that lift to turning. Go knife-edge, if you like, pull 1 g & you'll stall at the same speed. But you'll get a rather quick ride down. Going down doesn't have to mean that you've stalled.
 
The lowest stall aoa happens with full flap. If you calibrate your system at full flap you will always be conservative.
 
I was taught by a fighter pilot to always "turn the plane into a bullet " when in the landing pattern. Airplanes won't stall if the wings are not loaded. Great advice.
 
rv7charlie said:
The way I understand it, if you don't require the wing to maintain altitude (descending turn), then you're no longer requiring the wing to counteract gravity,.
Click to expand...

It's not just not maintain altitude; if you don't want to increase the wing loading (and AOA) you have to allow the airplane to accelerate downward (e.g., ever increasing rate of descent). At least until the vertical component of drag plus whatever lift the wing provides (some part of 1 g?) balances out gravity.
 
rv7charlie said:
Isn't that what I said, if you quote the entire post?
Click to expand...

I quoted only the first sentence because it wasn't correct. A descending turn isn't good enough, it has to be a descending turn at an ever increasing rate of descent. I suspect most pilots are unwilling to accept these vertical rates. e.g., if the total force generated by the wing is held to just 1g, and you're in a 45 deg bank, the vertical component is 0.7 g, so the plane accelerates downward at 0.3 g. After 5 seconds the vertical speed has reached 3000 ft per min.
 
free fall vs descent

Bob is right here. There is a difference between descending and accelerating downward.

In a turn, initially if you don't pull on extra g, you will start to accelerate downward, and the angle of attack won't increase, because you are not asking for lift. But if you allow this to continue, its not that you will just descend, but that you will accelerate downward, that is, your descent rate will continue to increase.
At some point, you will try to arrest the increasing descent rate, and in doing so, you will drastically increase your AoA, regardless of bank angle.

My point is that in making an 'unloaded' descending turn, you can delay the onset of high AoA for a while but eventually you will have to pay for it by higher AoA and g to arrest the descent. Don't think that just because you are descending, the stall speed won't increase with bank angle. It all depends on whether your descent rate is constant or increasing.

If you add to this the aerodynamics of low aspect-ratio rectangular wings, you have a potentially dangerous situation. Our wings don't have an abrupt stall, rather a mushy but dramatic increase in drag and descent rate.
There is more than one bad ending in the archives, by even high-time, highly experienced pilots, that arose from overshooting runway alignment, banking and pulling while too slow, and getting dramatic sink rates as a result.
 
'What we have here, is a failure to communicate.' Probably my fault for allowing the phrase 'maintain altitude' to show up anywhere in my post. What I was trying to say is that whatever portion of 1G you recover by not maintaining altitude, you can apply to turning without changing stall speed. The rest of the statement carries it to the extreme: you can, technically, go knife-edge and make a 1G turn without stalling. But you will arrive at the ground very quickly.

Quote from original question:
It seems that bank angle in itself isn't a factor, it is the adding of G's through up elevator that causes the AOA to increase and thereby the stall speed increase. I have a D100 with an AOA indicator and my question is, if I am in a bank and near the stall point for my current configuration, will I get an AOA warning similar to when I stall level. I assume this is the case, but wasn't sure and looking for confirmation from those more experienced in this area.
Unquote.
He asked what the G meter would indicate. If you an manage to bank, but maintain a 1G load on the airframe by *not adding back pressure on the stick* (not something that comes naturally), the G meter will still indicate 1G and the AOA indicator will not change. But obviously, you will descend quite rapidly. And the wing's stall speed will be unchanged.

So his statement that bank angle itself isn't a factor until he adds up-elevator, would be correct.
 
Thanks for the replies and discussion here. Clearly the message received is to be cautious, but it seems that the AOA will indicate impending problems and can be used as a warning to advise of a pre-stall condition in the situation outlined. I will practice this a bit more at altitude to test that assumption. I knew not to pull back in that turn, but it would seem that I may have been unconsciously been doing so. I plan get a CFI to do a bunch of stall and upset work with me this spring.

Larry
 
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