I disagree with you're assessment that a level turn poses a higher potential threat than a descending turn. I think an AOA gauge would help a pilot in both scenarios, but IMO, more so to the descending turn pilot, especially if he accidentally strays into the high AOA regime.
Originally Posted by
JamesNoBrakes
A descending turn, which is usually done at low power (that's a good indicator right there), is usually at a fairly low AOA if done a any kind of normal speed.
What is the low power a good indicator of?
From my perspective, the final turn (i.e. a descending turn with power back) is notoriously dangerous because pilots fail to appreciate the lack of energy available in their aircraft. I’ll go out on the limb and suggest that more pilots have lost control of their aircraft in the final turn than on a level turn from downwind to base. Ask that pilot in the descending turn to level off or tighten his turn to prevent an overshoot and the AOA gauge will water his eyes. His relatively low AOA 3 seconds ago is going to shoot into the danger area far quicker without proper power and flying technique than his buddy in the level turn back up at pattern altitude.
Originally Posted by
JamesNoBrakes
A level turn, which requires higher power, may be done when a pilot is already fairly low on the downwind and base, so he's "saving" for final, but they often start to slow up, put in flaps, etc. This can create an excessively high AOA situation coupled with a turn. The stall warning may help, but this usually comes on pretty fast and some advance notice would be nice.
I don’t get the “saving for final” term. Also, is he lower than he would be in the turn to final? Certainly, excessive AOA and a turn are not a good combination. However, adding a descent to those two is worse, IMO. Personally, if I had to choose between encountering a stall in a level turn versus a descending turn, I’ll take level every time. If you’re turning level at high AOA and you stall at pattern altitude, you have altitude to recover. If your AOA spikes in a descending turn, you don’t, plus you already have a significant sink rate you have to counter as well.
Originally Posted by
JamesNoBrakes
Then there was the issue of takeoff, when the airplane isn't climbing, but it is in the air and covering ground, there may not be a great appreciation as to where the AOA really is. The pilot may think they have some protection because they are moving fairly fast over the ground, but the AOA is so high and the induced drag so high that it's not going to end well. Maybe with this indication earlier one would fly it to a safe-spot earlier, avoiding trees later.
I think what I'm getting at is that we tend to not appreciate where the AOA is. Plenty of these attitudes are "normal" for flight, I've seen plenty of airplanes in almost level flight "attitude", yet their AOA is nearly off the scale (in terms of right about to stall). That's probably one of the bigger issues with that takeoff video, the plane "appeared" to be in a normal attitude, so the guy probably thought the AOA was "normal". It wasn't.
Are you saying there are scenarios in a GA aircraft that could result in an “almost level flight attitude” with AOA “nearly off the scales” and the pilot would be unaware were it not for an AOA gauge? I don’t have a huge amount of experience with those aircraft, so perhaps you can give me some of the scenarios you are referring to.
That takeoff was a classic density altitude accident. I think his problem was more of energy deficiency than simply high AOA (at least at first). I could be off base here, so correct me if I’m wrong. I assume he attained the normal takeoff/climb IAS when he got airborne. Because of the density altitude, his TAS was higher to produce the same IAS. With little to no excess thrust for his climb, in order to maintain that IAS and the usual AOA at such an extreme density altitude, he had to hold a lower pitch attitude and he was unable to climb. So, when they were muddling along in semi-level flight after takeoff, wouldn’t the AOA gauge (if he had one) have been indicating something close to normal? Assuming he was holding the IAS he wanted (even if that required a descent), wouldn’t he see the roughly the same AOA he saw every other flight at that IAS?
I think, what would have shown him he was in trouble would have been ANY attempt to turn, climb or just increase back pressure on the yoke when his airspeed began to decrease. Now he would have seen that AOA gauge spike into the danger zone faster and further than with those same inputs at lower density altitude – giving him a true understanding of how low on energy he really was. So, to your point, there were definitely times during that flight an AOA gauge would have clued him about how close to the edge he really was. I’m just not sure he would have had an AOA indication that was “not normal” for the entire flight.
Last edited by Adlerdriver; 11-15-2014 at 09:19 PM.