Is that AOA relationship the same for all airplanes? What’s the equation?

In the 501, what AoA gives you L/D max?
I'm assuming it is higher than .35.

That is impressive.

Max climb thrust to 410, then AOA .35, then how about the descent, thrust idle all the way down?

The indicated stall speed doesn't change that much with altitude, that is a relatively minor effect for a Citation. The true airspeed does change, of course. For planes with higher wing loadings and higher speeds, the effect is greater, but a Citation operating at 0.35 AOA is not experiencing those effects significantly.


Assuming your AOA is properly calibrated (I've seen a fair number that aren't), you stall at AOA of 1.0. That means at that airspeed, you can only produce the lift equal to the weight of the plane. Lift increases at the square of the speed, so doubling your speed means you can generate 4 times the lift. This would be an AOA of 0.25, you are using only 1/4 of the lift capability of the wing.

AOA = (Vstall / Vindicated) ^ 2

For my V, at 14,000 lbs, my clean zero bank stall speed is 89 KCAS. At AOA 0.35, this means I am flying at 150 KCAS. For my setup, KIAS is KCAS in most cases.

Mike C.

I would assume so, that's the most fuel efficient descent profile.

.35 is L/D max. But while this gives you max endurance, it doesn't necessarily give you max range due to the effects of wind. The Operating Manual has charts that give you best range numbers based on altitude, winds, and temperature. Depending on the winds, going faster may actually give you more range that going slower.

This is a little tangential, but I have an older analog AOA indicator in the Piaggio for which I didn’t have good documentation on how to interpret, and this thread finally made me do some searching - thanks to all for the AoA discussion which prodded me to do it.

Found this article which is a little dated but is not a bad summary.

https://www.safeflight.com/upload/AoA%2 ... 202006.pdf

Main things I wanted to know were nailing down what the color ranges defined, what the values correspond to, etc. Thanks to Mike C also for the basic AoA equation, which I confirmed correlate to my POH stall speeds, etc.

Summary:
- yellow = .6 aoa = 1.3 Vs = POH Vref speeds
- mid-yellow = .7 aoa = 1.2 Vs
- red = .75 aoa = 1.15 Vs = stall warning activation
- .5 aoa is roughly Vy

My AOA indicator is this:

Looks very similar to mine except without the selectable bug. Mine has a fixed bug at .35 for L/D Max. .6 is Vref.


I also have a little HUD with ^, V, and O designations for whether I am above, below, or at .6 when coming in to land.

great discussion. I will admit I didn't understand the AOA numbers on the gauge and Mike C's description makes so much sense. Total light bulb moment. or more like duh..

Mike

The indicated stall speed doesn't change that much with altitude, that is a relatively minor effect for a Citation. The true airspeed does change, of course. For planes with higher wing loadings and higher speeds, the effect is greater, but a Citation operating at 0.35 AOA is not experiencing those effects significantly.


Assuming your AOA is properly calibrated (I've seen a fair number that aren't), you stall at AOA of 1.0. That means at that airspeed, you can only produce the lift equal to the weight of the plane. Lift increases at the square of the speed, so doubling your speed means you can generate 4 times the lift. This would be an AOA of 0.25, you are using only 1/4 of the lift capability of the wing.

AOA = (Vstall / Vindicated) ^ 2

For my V, at 14,000 lbs, my clean zero bank stall speed is 89 KCAS. At AOA 0.35, this means I am flying at 150 KCAS. For my setup, KIAS is KCAS in most cases.

Mike C.

I'll add in my dumb question...

Is the AoA gauge accurate through all phases of flight? Is it accurate in a steep bank?

I've never flown with an AoA, but I would like to.

It is intended to be if properly calibrated. On my plane, the air vane and the flap position are combined and then displayed on the AOA gauge after passing through a "computer" box.

The AOA indicator does assume a clean wing, no contamination from ice or anything else. If you have that, then you may stall at a lower AOA.


Yes, it doesn't care about bank, weight, airspeed. All it knows is the AOA itself. You can be at 150 knots wings level and stall the airplane, you can be at 50 knots and 90 degree bank and not be stalled. Stall is not a speed, but it is an AOA.


There are those who says having an AOA is transformative and would prevent stall accidents. I'm not in that camp because ALL airplanes have an AOA indicator, the stall warning system. People stall the airplane with the stall warning going off, so the issue is clearly not the lack of indication.

For me, the AOA provides a double check of the Vref speed. If I am on speed, I should see 0.6 AOA. This double checks my Vref computation. I also have an indexer which gives me the yellow green, red discrete indications and it is mounted up on my glare shield so I can see it easily during the final visual part of landing.

Mike C.

It is accurate in all phases, even steep banks. It sees the same airflow the wing does, and the angle is "normalized" at all flap settings.

It is accurate in all phases, even steep banks. It sees the same airflow the wing does, and the angle is "normalized" at all flap settings.

It appears to be very helpful to wring the last bit of performance out of a short field landing too. I've enjoyed watching the guy from Costa Rica fly into some amazingly tight and short strips using the AoA as a primary indicator.