AOA indicator

Not that I am arguing with anyone, but my flight computer, knows my flap position, it also knows when I dump water and for how long (LX 90xx). I have in the profile the empty weight of glider and my weight with chute. True I need to set the amount of ballast and bugs. The argument that if the pilot does not enter the glider weight the results are wrong. It is nearly impossible to design idiot proof equipment, because they always make better idiots. As for software vs direct measure, there is a reason I do not have a vario named after me. Good discussion though and perhaps someone with a sharp pencil will design such a unit.

On Wednesday, April 20, 2016 at 6:35:08 PM UTC-7, Jonathan St. Cloud wrote:
Not that I am arguing with anyone, but my flight computer, knows my flap position, it also knows when I dump water and for how long (LX 90xx). I have in the profile the empty weight of glider and my weight with chute. True I need to set the amount of ballast and bugs. The argument that if the pilot does not enter the glider weight the results are wrong. It is nearly impossible to design idiot proof equipment, because they always make better idiots. As for software vs direct measure, there is a reason I do not have a vario named after me. Good discussion though and perhaps someone with a sharp pencil will design such a unit.

Not gonna work during a winch launch, no matter what, and for many people (including myself, if we ever get one here), that's a big omission.

During yesterday's flight I wondered how many times an AoA indicator would have been crying "The sky is falling!"
Seems OK for the C172 Family Truckster. Not sure how it would behave in turbulent narrow thermals or rotor, where AoA changes frequently.
Perhaps more aggravating than useful?
Jim

On Saturday, April 23, 2016 at 12:10:26 AM UTC-5, JS wrote:
During yesterday's flight I wondered how many times an AoA indicator would have been crying "The sky is falling!"
Seems OK for the C172 Family Truckster. Not sure how it would behave in turbulent narrow thermals or rotor, where AoA changes frequently.
Perhaps more aggravating than useful?
Jim

Was your stall warning going off? Because that little vane or whatever they use on Cezznas these days is just a crude on/off AOA indicator, calibrated to go off just before stalling AOA.

If it's turbulent enough to affect AOA that significantly, i would think it would be nice to know - so as to speed up enough to stay out of the stall range?

I will admit that it wasn't ever a problem in the F-4; 78 lbs/sq ft at 540 knots doesn't get bounced around much...

Information is information - AOA provides direct information, in real time, of what your wing is doing with regards to producing lift. Airspeed does not - it just tells you how fast you are moving through the air. Both are useful, for different reasons.

Ever tried a really hard slip in a modern glider? Or a K-21, even? What does the airspeed show? Hmm, it sure flies nice at zero airspeed! A properly designed AOA system would work at pretty much any realistic yaw angle, so you could slip without having to guess how fast you are going. Nice to have since the FAA still wants slips to a landing during a checkride!

(Just joking a bit there, but you get the idea...).

Kirk
66

I think sometimes the Cessna stall warning tabs are affected by gravity too, not just AOA. I was in the pattern at Bishop, CA in a Cessna 340 (pressurized twin, cabin class) with a Vso of 64 (with vortex generators) flying 120 knots. It was turbulent and the stall warning horn kept going off in the bumps, checked both ASI's and GPS speed, controls felt firm, no mushing, so I ignored the warnings landed fine, checked the stall tab, it appeared to operate normally. It seems like flying into Minden or Lake Tahoe I had encountered much worse turbulence yet never had the stall warning horn. While we trust instruments, keep your mind in the loop.

On Saturday, April 23, 2016 at 8:20:32 AM UTC-7, kirk.stant wrote:

Was your stall warning going off? Because that little vane or whatever they use on Cezznas these days is just a crude on/off AOA indicator, calibrated to go off just before stalling AOA.

If it's turbulent enough to affect AOA that significantly, i would think it would be nice to know - so as to speed up enough to stay out of the stall range?

I will admit that it wasn't ever a problem in the F-4; 78 lbs/sq ft at 540 knots doesn't get bounced around much...

Information is information - AOA provides direct information, in real time, of what your wing is doing with regards to producing lift. Airspeed does not - it just tells you how fast you are moving through the air. Both are useful, for different reasons.

Ever tried a really hard slip in a modern glider? Or a K-21, even? What does the airspeed show? Hmm, it sure flies nice at zero airspeed! A properly designed AOA system would work at pretty much any realistic yaw angle, so you could slip without having to guess how fast you are going. Nice to have since the FAA still wants slips to a landing during a checkride!

(Just joking a bit there, but you get the idea...).

Kirk
66

We all have stall warning horns/lights in ag spray planes. Almost everyone has disconnected them. Another useless instrument when it comes to flying that is necessarily stick and rudder.
Dan

On Saturday, April 23, 2016 at 11:59:42 AM UTC-5, wrote:
We all have stall warning horns/lights in ag spray planes. Almost everyone has disconnected them. Another useless instrument when it comes to flying that is necessarily stick and rudder.
Dan

Dan, while I tend to agree that most stall warning indicators are of marginal use if you are current and have lots of experience in a particular plane, remember we are talking about glider pilots - most do not fly that much each year, and many may fly several different types frequently.

Heck, if you are comfortable in your plane, hardly any instrument is really needed. But if I could only have one - it would be a good AOA indicator :^)!

Kirk
66

On Saturday, April 23, 2016 at 3:19:47 PM UTC-7, kirk.stant wrote:
On Saturday, April 23, 2016 at 11:59:42 AM UTC-5, wrote:
We all have stall warning horns/lights in ag spray planes. Almost everyone has disconnected them. Another useless instrument when it comes to flying that is necessarily stick and rudder.
Dan

Dan, while I tend to agree that most stall warning indicators are of marginal use if you are current and have lots of experience in a particular plane, remember we are talking about glider pilots - most do not fly that much each year, and many may fly several different types frequently.

Heck, if you are comfortable in your plane, hardly any instrument is really needed. But if I could only have one - it would be a good AOA indicator :^)!

Kirk
66

Gliders are flown substantially differently than most other aircraft: we circle just above stall speed at high bank angles. A stall warning would be going off continuously and would be more annoying than anything. Above 30 degrees bank angle I find it impossible to stall the glider anyway; a stall will usually occur because of a gust. I don't know what an AOA indicator would add because AOA varies from the inner wing tip to the outer wing tip. The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!

Tom

On Friday, April 29, 2016 at 6:18:00 PM UTC-5, 2G wrote:

Gliders are flown substantially differently than most other aircraft: we circle just above stall speed at high bank angles. A stall warning would be going off continuously and would be more annoying than anything. Above 30 degrees bank angle I find it impossible to stall the glider anyway; a stall will usually occur because of a gust. I don't know what an AOA indicator would add because AOA varies from the inner wing tip to the outer wing tip. The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!

Tom

Tom, in many respects gliders are flown just like fighter planes - either fast or hard turning, at varying g loads and weights. Which is why AOA is often used instead of airspeed in those conditions. This is not a stall warning system, but an indication of what the actual AOA of the plane is. It can be an averaged indication - the critical AOA will be the same once calibrated. Momentary excursions due to gusts are handled just like on the airspeed indicator - you ignore them!

Amazing how almost everyone who actually hasn't used a real AOA system dismisses the concept out of hand. Kinda reminds me of the Brits before WW2 who totally dismissed Frank Whittle's ideas about jets (after all, he was just a lowly Flight Lieutenant) and as a result missed out on possibly having jet fighters during the Battle of Britain...

Cheers,

Kirk
66

On Friday, April 29, 2016 at 6:18:00 PM UTC-5, 2G wrote:

The MOST important thing to do is to maintain coordinated flight. Maybe you could put an audible warning on the yaw string!

Tom

I don't agree. The MOST important thing is to not exceed stalling AOA. Below that, yaw (within limits) adds drag (or may help a bit - see discussions about slipping turns while thermalling) and may be less efficient; but you can still control your glider - exceed the critical AOA, and you are a passenger until you reduce it.

Airspeed indicators are required (which are indirect AOA indicators). Yaw strings or slip balls are not.

Kirk
66